PID Controller Design for Ventilator...

[George Herold]

On Tuesday, August 18, 2020 at 3:05:56 PM UTC-4, bitrex wrote:

On 8/17/2020 11:53 AM, George Herold wrote:
On Sunday, August 16, 2020 at 11:14:22 AM UTC-4, jla...@highlandsniptechnology.com wrote:
On Sun, 16 Aug 2020 07:53:41 -0700 (PDT), Lasse Langwadt Christensen
langwadt@fonz.dk> wrote:

sųndag den 16. august 2020 kl. 16.31.14 UTC+2 skrev Jan Panteltje:
On a sunny day (Sat, 15 Aug 2020 22:46:45 -0700 (PDT)) it happened Ricketty C
gnuarm.deletethisbit@gmail.com> wrote in
d2d879c1-cf13-42f8-9727-8ef27dc2dc65o@googlegroups.com>:


He shows the only difference between patient triggered and machine triggered
waveforms is the negative pressure from the patient trying to draw air in
at the very start of the cycle. His diagrams are pretty poor with no registration
between the various points on different parameters, but he gets across
the main points. You can do a Google search to find other much better
diagrams. I don\'t think there are any new concepts to an engineer.

No experience with these things
but from _my_ life I know breathing is related to oxygen level in the blood.

not really, your breathing is mostly related to the amount of CO2 in your lungs
that\'s why breathing something like pure nitrogen will kill you without you
even noticing

I wonder how many old ladies ricky\'s team plans to kill, trying to
learn PIDs and stuff.

Do you know any good control \'theory/practice\' books. I\'ve got a few, but
I tend to get a little lost in the Laplace transforms, And would
love something with a more \'hands on\' feel, an AoE type of book.

Tim Wescott\'s book is fine.
https://www.wescottdesign.com/actfes/actfes.html

Would you enjoy this fine series from MIT on ordinary differential
equations including Laplace transforms:

https://www.youtube.com/watch?v=zvbdoSeGAgI

The whole lecture series is good. the Laplace transform (and other
integral transforms too) are, in general, tools for solving differential
equations. So a refresh on ODEs may be helpful

Yeah well I just replace \'s\' with \'i*w\' (omega.. angular frequency) and
Laplace transforms are fine. My problem is that it\'s easy to dig down
into the math (algebra) and lose a sense of what is going on.
I sorta need the math after I understand it.

George H.

George H.



--

John Larkin Highland Technology, Inc

Science teaches us to doubt.

Claude Bernard

 

[George Herold]

On Tuesday, August 18, 2020 at 3:59:43 PM UTC-4, Three Jeeps wrote:

On Monday, August 17, 2020 at 11:53:56 AM UTC-4, George Herold wrote:
On Sunday, August 16, 2020 at 11:14:22 AM UTC-4, jla...@highlandsniptechnology.com wrote:
On Sun, 16 Aug 2020 07:53:41 -0700 (PDT), Lasse Langwadt Christensen
lang...@fonz.dk> wrote:

sųndag den 16. august 2020 kl. 16.31.14 UTC+2 skrev Jan Panteltje:
On a sunny day (Sat, 15 Aug 2020 22:46:45 -0700 (PDT)) it happened Ricketty C
gnuarm.del...@gmail.com> wrote in
d2d879c1-cf13-42f8...@googlegroups.com>:


He shows the only difference between patient triggered and machine triggered
waveforms is the negative pressure from the patient trying to draw air in
at the very start of the cycle. His diagrams are pretty poor with no registration
between the various points on different parameters, but he gets across
the main points. You can do a Google search to find other much better
diagrams. I don\'t think there are any new concepts to an engineer..

No experience with these things
but from _my_ life I know breathing is related to oxygen level in the blood.

not really, your breathing is mostly related to the amount of CO2 in your lungs
that\'s why breathing something like pure nitrogen will kill you without you
even noticing

I wonder how many old ladies ricky\'s team plans to kill, trying to
learn PIDs and stuff.
Do you know any good control \'theory/practice\' books. I\'ve got a few, but
I tend to get a little lost in the Laplace transforms, And would
love something with a more \'hands on\' feel, an AoE type of book.

Tim Wescott\'s book is fine.
https://www.wescottdesign.com/actfes/actfes.html

George H.



--

John Larkin Highland Technology, Inc

Science teaches us to doubt.

Claude Bernard

Back in the day when I did design and teaching of this stuff, I used books by Brogan, Kou, Ogata, Diazzo & Haupis and Astrom. All are fairly theoretical, but Astroms book \"Computer Controlled System: Theory and Design - 3rd edition was one that rolled in the use of Matlab & Simulink, as well as a chapter on \'implementation details\' . There may be more applications oriented \"how to\' books around as of late, I just don\'t know about them. The Westcott book seems to be a valuable collection of \'things I learned when implementing control systems\' Anyone who lived in the trenches can identify with having learned those lessons.

Actually, some of the detailed example problems in Matlab & Simulink are quite good, and they have a example on how to use their code generator which is helpful. Getting it set up for your target machine can be a little tricky.
Good luck
J

Thanks, I\'ll give \'em a look see.

George H.

 

[server]

On Wed, 19 Aug 2020 08:05:08 -0700 (PDT), George Herold
<ggherold@gmail.com> wrote:

On Tuesday, August 18, 2020 at 3:05:56 PM UTC-4, bitrex wrote:
On 8/17/2020 11:53 AM, George Herold wrote:
On Sunday, August 16, 2020 at 11:14:22 AM UTC-4, jla...@highlandsniptechnology.com wrote:
On Sun, 16 Aug 2020 07:53:41 -0700 (PDT), Lasse Langwadt Christensen
langwadt@fonz.dk> wrote:

s?ndag den 16. august 2020 kl. 16.31.14 UTC+2 skrev Jan Panteltje:
On a sunny day (Sat, 15 Aug 2020 22:46:45 -0700 (PDT)) it happened Ricketty C
gnuarm.deletethisbit@gmail.com> wrote in
d2d879c1-cf13-42f8-9727-8ef27dc2dc65o@googlegroups.com>:


He shows the only difference between patient triggered and machine triggered
waveforms is the negative pressure from the patient trying to draw air in
at the very start of the cycle. His diagrams are pretty poor with no registration
between the various points on different parameters, but he gets across
the main points. You can do a Google search to find other much better
diagrams. I don\'t think there are any new concepts to an engineer.

No experience with these things
but from _my_ life I know breathing is related to oxygen level in the blood.

not really, your breathing is mostly related to the amount of CO2 in your lungs
that\'s why breathing something like pure nitrogen will kill you without you
even noticing

I wonder how many old ladies ricky\'s team plans to kill, trying to
learn PIDs and stuff.

Do you know any good control \'theory/practice\' books. I\'ve got a few, but
I tend to get a little lost in the Laplace transforms, And would
love something with a more \'hands on\' feel, an AoE type of book.

Tim Wescott\'s book is fine.
https://www.wescottdesign.com/actfes/actfes.html

Would you enjoy this fine series from MIT on ordinary differential
equations including Laplace transforms:

https://www.youtube.com/watch?v=zvbdoSeGAgI

The whole lecture series is good. the Laplace transform (and other
integral transforms too) are, in general, tools for solving differential
equations. So a refresh on ODEs may be helpful
Yeah well I just replace \'s\' with \'i*w\' (omega.. angular frequency) and
Laplace transforms are fine. My problem is that it\'s easy to dig down
into the math (algebra) and lose a sense of what is going on.
I sorta need the math after I understand it.

George H.

Right. Being able to push some equations around doesn\'t mean you
understand it.



--

John Larkin Highland Technology, Inc

Science teaches us to doubt.

Claude Bernard

 

[Ricketty C]

On Wednesday, August 19, 2020 at 11:05:16 AM UTC-4, George Herold wrote:

On Tuesday, August 18, 2020 at 3:05:56 PM UTC-4, bitrex wrote:
On 8/17/2020 11:53 AM, George Herold wrote:
On Sunday, August 16, 2020 at 11:14:22 AM UTC-4, jla...@highlandsniptechnology.com wrote:
On Sun, 16 Aug 2020 07:53:41 -0700 (PDT), Lasse Langwadt Christensen
langwadt@fonz.dk> wrote:

sųndag den 16. august 2020 kl. 16.31.14 UTC+2 skrev Jan Panteltje:
On a sunny day (Sat, 15 Aug 2020 22:46:45 -0700 (PDT)) it happened Ricketty C
gnuarm.deletethisbit@gmail.com> wrote in
d2d879c1-cf13-42f8-9727-8ef27dc2dc65o@googlegroups.com>:


He shows the only difference between patient triggered and machine triggered
waveforms is the negative pressure from the patient trying to draw air in
at the very start of the cycle. His diagrams are pretty poor with no registration
between the various points on different parameters, but he gets across
the main points. You can do a Google search to find other much better
diagrams. I don\'t think there are any new concepts to an engineer.

No experience with these things
but from _my_ life I know breathing is related to oxygen level in the blood.

not really, your breathing is mostly related to the amount of CO2 in your lungs
that\'s why breathing something like pure nitrogen will kill you without you
even noticing

I wonder how many old ladies ricky\'s team plans to kill, trying to
learn PIDs and stuff.

Do you know any good control \'theory/practice\' books. I\'ve got a few, but
I tend to get a little lost in the Laplace transforms, And would
love something with a more \'hands on\' feel, an AoE type of book.

Tim Wescott\'s book is fine.
https://www.wescottdesign.com/actfes/actfes.html

Would you enjoy this fine series from MIT on ordinary differential
equations including Laplace transforms:

https://www.youtube.com/watch?v=zvbdoSeGAgI

The whole lecture series is good. the Laplace transform (and other
integral transforms too) are, in general, tools for solving differential
equations. So a refresh on ODEs may be helpful
Yeah well I just replace \'s\' with \'i*w\' (omega.. angular frequency) and
Laplace transforms are fine. My problem is that it\'s easy to dig down
into the math (algebra) and lose a sense of what is going on.
I sorta need the math after I understand it.

That seems a bit backwards to me. The math is what ultimately explains things. You just need to understand the math. Math is hard, so people often take short cuts. I don\'t want to wade through a bunch of math of a PID controller that might not be completely correct, but I can use the math to explore the nature of the beast. The lung has a dissipative element and an integral element. That tells me what the waveforms of pressure, flow and volume should look like and how the controller should function. Until I get some idea of the math, I don\'t know what to expect.

I was just looking a the waveforms of our controller. I was being told our graphs are near, but not quite the same as the example case. I realized very quickly the differences are not from the controller. They are from differences in the lung model. With constant pressure, the spring constant creates a curve in the volume and a sloping curve in the flow. The dissipative element (like resistance) gives a pressure directly proportional to flow, so the flow would be flat like the pressure and volume would be a triangle. The example shows more influence from the dissipative element and less from the spring constant. The controller is working fine. The test case has a slower pressure release on the exhale side indicating the exhalation path is more obstructed than the example. If our test case were on a real patient the flow rate dropping near zero means the lungs are nearly full which I expect would make injury more likely and the volume needs to be reduced..

Maybe I am making your case because I didn\'t do any math to dig out this info, but it is because I have seen the math and understand what the math tells me.

--

Rick C.

-++ Get 1,000 miles of free Supercharging
-++ Tesla referral code - https://ts.la/richard11209

 

[rangerssuck]

On Saturday, August 15, 2020 at 9:44:08 PM UTC-4, Ricketty C wrote:

I understand the basics of PID design, but if you can\'t describe the thing being controlled, how can you design the controller other than trial and error?

The \"plant\" is a motor on a tall reducing gear (~300:1) turning an arm that presses on a bag producing an air flow with the loop controlled by a pressure measurement.

One issue I\'m seeing discussed is a tradeoff on the PWM resolution vs. frequency. Presently they are using 3.6 kHz with 8 bit PWM control. I kinda wonder if a sigma-delta might be better, but that might require some external logic. They seem to be shy of pushing the CPU too much even after changing from an Arduino CPU at 20 MHz to an ARM CM4F at 80 MHz.

The big concern is the overshoot when ramping up the pressure between exhale and inhale. In general, would it be better to simply jump the pressure set point at once and let the PID controller do its thing, optimizing the response time as best as possible controlling overshoot -or- would it be better to run up the pressure set point over a period of time which would seem to place less demand on the PID controller?

The model of the lung seems to include a spring constant (I think of this as a capacitor) in parallel with a dissipative element (a dashpot or resistor in electronics). The motor is highly geared to a relatively lightweight arm pushing on a bag with air passing through a tube of relatively low restriction. So initially the dominate opposition to flow will be the dissipation/resistor, i.e. proportional to the rate of airflow. This in turn is proportional to the arm speed (although not constant through the stroke due to the bag geometry). The arm speed is what is controlled by the PWM (approximately).

The lung model shows the dashpot and spring in parallel, but I\'m not sure that\'s appropriate. The response to air entering the lung will be the sum of the airway resistance (dashpot) and the lung compliance (spring) which would be a series combination to obtain the resulting air pressure. Well, maybe that is right for the mechanical model, but in the electrical equivalent if pressure is the same as voltage it would be a series arrangement.

Anyway, the lung would seem to be a capacitor and a resistor. So if driven by a P only controller, is there any way it could ring? I was shown data measured that showed huge ringing from an initial step function in the set point.

I watched some videos and it seems they use both pressure regulated and flow regulated cycles. I expect to see similar results with either method.

Interesting

--

Rick C.

- Get 1,000 miles of free Supercharging
- Tesla referral code - https://ts.la/richard11209

What you might want to think about is breaking the cycle up into chunks, to remove some of the mechanical geometry from the equation. Then do PID on each of those. The arduino libraries include PID and FastPID, which as another poster mentioned, can be tuned on the fly.

My thinking is that by removing mechanical variables, you\'ve really simplified things. I would start with a sketched curve of pressure (or volume)/time. Mark on the curve the points where the geometry changes significantly. Now try to tune the PID for the leftmost segment. When that\'s behaving OK, tune the PID for the next segment, leaving the first settings alone. Repeat until the whole thing is working.

Note - I have never done this sort of segment system, but that\'s where I would start.

I\'m a little concerned that \"they\" are running out of CPU with something as slow as human breathing. In fact, it\'s slow enough that you might consider a different approach: Map the rotation of the shaft to the volume of expelled air. Set many target points along that curve and then positively control the motor to hit those points of rotation at the proper times. This should also be easy to set up with Arduino PID controls (which will also work on higher end boards like ARM, ESP or the like). A tiny & cheap shaft encoder would make it really simple.

 

[Ricketty C]

On Wednesday, August 19, 2020 at 8:50:05 PM UTC-4, rangerssuck wrote:

On Saturday, August 15, 2020 at 9:44:08 PM UTC-4, Ricketty C wrote:
I understand the basics of PID design, but if you can\'t describe the thing being controlled, how can you design the controller other than trial and error?

The \"plant\" is a motor on a tall reducing gear (~300:1) turning an arm that presses on a bag producing an air flow with the loop controlled by a pressure measurement.

One issue I\'m seeing discussed is a tradeoff on the PWM resolution vs. frequency. Presently they are using 3.6 kHz with 8 bit PWM control. I kinda wonder if a sigma-delta might be better, but that might require some external logic. They seem to be shy of pushing the CPU too much even after changing from an Arduino CPU at 20 MHz to an ARM CM4F at 80 MHz.

The big concern is the overshoot when ramping up the pressure between exhale and inhale. In general, would it be better to simply jump the pressure set point at once and let the PID controller do its thing, optimizing the response time as best as possible controlling overshoot -or- would it be better to run up the pressure set point over a period of time which would seem to place less demand on the PID controller?

The model of the lung seems to include a spring constant (I think of this as a capacitor) in parallel with a dissipative element (a dashpot or resistor in electronics). The motor is highly geared to a relatively lightweight arm pushing on a bag with air passing through a tube of relatively low restriction. So initially the dominate opposition to flow will be the dissipation/resistor, i.e. proportional to the rate of airflow. This in turn is proportional to the arm speed (although not constant through the stroke due to the bag geometry). The arm speed is what is controlled by the PWM (approximately).

The lung model shows the dashpot and spring in parallel, but I\'m not sure that\'s appropriate. The response to air entering the lung will be the sum of the airway resistance (dashpot) and the lung compliance (spring) which would be a series combination to obtain the resulting air pressure. Well, maybe that is right for the mechanical model, but in the electrical equivalent if pressure is the same as voltage it would be a series arrangement.

Anyway, the lung would seem to be a capacitor and a resistor. So if driven by a P only controller, is there any way it could ring? I was shown data measured that showed huge ringing from an initial step function in the set point.

I watched some videos and it seems they use both pressure regulated and flow regulated cycles. I expect to see similar results with either method..

Interesting

--

Rick C.

- Get 1,000 miles of free Supercharging
- Tesla referral code - https://ts.la/richard11209

What you might want to think about is breaking the cycle up into chunks, to remove some of the mechanical geometry from the equation. Then do PID on each of those. The arduino libraries include PID and FastPID, which as another poster mentioned, can be tuned on the fly.

My thinking is that by removing mechanical variables, you\'ve really simplified things. I would start with a sketched curve of pressure (or volume)/time. Mark on the curve the points where the geometry changes significantly. Now try to tune the PID for the leftmost segment. When that\'s behaving OK, tune the PID for the next segment, leaving the first settings alone. Repeat until the whole thing is working.

The only changes in \"geometry\" (which I assume you mean the shape of the curve) is at the points were we change our set point. The ideal curve would be a square wave for which ever variable is being controlled. The rate of the leading edge will be limited by the details of the control loop. The trailing edge is not in control since that is simply the patient exhaling.

Nothing much is needed really. I think the ringing curve they showed me was pure P with no I or D terms in the control loop, but the gain was set far too high. Without the I term the P term requires an error to maintain a non-zero output. To minimize the error the gain is set way high resulting in excessive acceleration and ultimately ringing in the controlled parameter..

The other day they showed me working graphs where the exact shape is slightly different from the examples, but not in any way I would not attribute to the details of the lung model. I don\'t know what they did, but it is working.

Note - I have never done this sort of segment system, but that\'s where I would start.

I\'m a little concerned that \"they\" are running out of CPU with something as slow as human breathing.

I don\'t recall saying they had run out of CPU. Some weeks ago we switched from an Arduino CPU to an ARM CM4F when we needed more I/Os. No one objected to switching to a better CPU, but it has lots of room for growth in the project... except for I/Os. We are nearly out and they\'ve decided to add more LEDs.


> In fact, it\'s slow enough that you might consider a different approach: Map the rotation of the shaft to the volume of expelled air. Set many target points along that curve and then positively control the motor to hit those points of rotation at the proper times. This should also be easy to set up with Arduino PID controls (which will also work on higher end boards like ARM, ESP or the like). A tiny & cheap shaft encoder would make it really simple.

That would work for flow rate control, but the pressure depends on the patient and they are not all the same. It also depends on all the mechanical parts being the same with the same friction and the same resilience, etc. They have gone to great lengths to design a flow meter and we have a pressure gauge, so they are going to be used!

The more I think about the control loop, the simpler I think it will be. We have so much time to deal with the changes that it would require effort to muck it up.

--

Rick C.

+-- Get 1,000 miles of free Supercharging
+-- Tesla referral code - https://ts.la/richard11209

 

[bitrex]

On 8/19/2020 12:08 PM, Ricketty C wrote:

On Wednesday, August 19, 2020 at 11:05:16 AM UTC-4, George Herold wrote:
On Tuesday, August 18, 2020 at 3:05:56 PM UTC-4, bitrex wrote:
On 8/17/2020 11:53 AM, George Herold wrote:
On Sunday, August 16, 2020 at 11:14:22 AM UTC-4, jla...@highlandsniptechnology.com wrote:
On Sun, 16 Aug 2020 07:53:41 -0700 (PDT), Lasse Langwadt Christensen
langwadt@fonz.dk> wrote:

sųndag den 16. august 2020 kl. 16.31.14 UTC+2 skrev Jan Panteltje:
On a sunny day (Sat, 15 Aug 2020 22:46:45 -0700 (PDT)) it happened Ricketty C
gnuarm.deletethisbit@gmail.com> wrote in
d2d879c1-cf13-42f8-9727-8ef27dc2dc65o@googlegroups.com>:


He shows the only difference between patient triggered and machine triggered
waveforms is the negative pressure from the patient trying to draw air in
at the very start of the cycle. His diagrams are pretty poor with no registration
between the various points on different parameters, but he gets across
the main points. You can do a Google search to find other much better
diagrams. I don\'t think there are any new concepts to an engineer.

No experience with these things
but from _my_ life I know breathing is related to oxygen level in the blood.

not really, your breathing is mostly related to the amount of CO2 in your lungs
that\'s why breathing something like pure nitrogen will kill you without you
even noticing

I wonder how many old ladies ricky\'s team plans to kill, trying to
learn PIDs and stuff.

Do you know any good control \'theory/practice\' books. I\'ve got a few, but
I tend to get a little lost in the Laplace transforms, And would
love something with a more \'hands on\' feel, an AoE type of book.

Tim Wescott\'s book is fine.
https://www.wescottdesign.com/actfes/actfes.html

Would you enjoy this fine series from MIT on ordinary differential
equations including Laplace transforms:

https://www.youtube.com/watch?v=zvbdoSeGAgI

The whole lecture series is good. the Laplace transform (and other
integral transforms too) are, in general, tools for solving differential
equations. So a refresh on ODEs may be helpful
Yeah well I just replace \'s\' with \'i*w\' (omega.. angular frequency) and
Laplace transforms are fine. My problem is that it\'s easy to dig down
into the math (algebra) and lose a sense of what is going on.
I sorta need the math after I understand it.

That seems a bit backwards to me. The math is what ultimately explains things. You just need to understand the math. Math is hard, so people often take short cuts. I don\'t want to wade through a bunch of math of a PID controller that might not be completely correct, but I can use the math to explore the nature of the beast. The lung has a dissipative element and an integral element. That tells me what the waveforms of pressure, flow and volume should look like and how the controller should function. Until I get some idea of the math, I don\'t know what to expect.

I was just looking a the waveforms of our controller. I was being told our graphs are near, but not quite the same as the example case. I realized very quickly the differences are not from the controller. They are from differences in the lung model. With constant pressure, the spring constant creates a curve in the volume and a sloping curve in the flow. The dissipative element (like resistance) gives a pressure directly proportional to flow, so the flow would be flat like the pressure and volume would be a triangle. The example shows more influence from the dissipative element and less from the spring constant. The controller is working fine. The test case has a slower pressure release on the exhale side indicating the exhalation path is more obstructed than the example. If our test case were on a real patient the flow rate dropping near zero means the lungs are nearly full which I expect would make injury more likely and the volume needs to be reduced.

Maybe I am making your case because I didn\'t do any math to dig out this info, but it is because I have seen the math and understand what the math tells me.

What level of abstraction one needs to use at a particular time is a skill.

It\'s rare that there are interesting problems that one can intuitively
understand all the way up and down thru the levels and have some
God\'s-eye knowledge of everything without from time to time resorting to
faith in the idea that the process of pushing equations often provides
answers that are correct regardless if you \"grok\" every piece of it.

That is to say some people can read machine\'s \"mind\" I don\'t have this
ability.

 

[bitrex]

On 8/19/2020 11:05 AM, George Herold wrote:

On Tuesday, August 18, 2020 at 3:05:56 PM UTC-4, bitrex wrote:
On 8/17/2020 11:53 AM, George Herold wrote:
On Sunday, August 16, 2020 at 11:14:22 AM UTC-4, jla...@highlandsniptechnology.com wrote:
On Sun, 16 Aug 2020 07:53:41 -0700 (PDT), Lasse Langwadt Christensen
langwadt@fonz.dk> wrote:

sųndag den 16. august 2020 kl. 16.31.14 UTC+2 skrev Jan Panteltje:
On a sunny day (Sat, 15 Aug 2020 22:46:45 -0700 (PDT)) it happened Ricketty C
gnuarm.deletethisbit@gmail.com> wrote in
d2d879c1-cf13-42f8-9727-8ef27dc2dc65o@googlegroups.com>:


He shows the only difference between patient triggered and machine triggered
waveforms is the negative pressure from the patient trying to draw air in
at the very start of the cycle. His diagrams are pretty poor with no registration
between the various points on different parameters, but he gets across
the main points. You can do a Google search to find other much better
diagrams. I don\'t think there are any new concepts to an engineer.

No experience with these things
but from _my_ life I know breathing is related to oxygen level in the blood.

not really, your breathing is mostly related to the amount of CO2 in your lungs
that\'s why breathing something like pure nitrogen will kill you without you
even noticing

I wonder how many old ladies ricky\'s team plans to kill, trying to
learn PIDs and stuff.

Do you know any good control \'theory/practice\' books. I\'ve got a few, but
I tend to get a little lost in the Laplace transforms, And would
love something with a more \'hands on\' feel, an AoE type of book.

Tim Wescott\'s book is fine.
https://www.wescottdesign.com/actfes/actfes.html

Would you enjoy this fine series from MIT on ordinary differential
equations including Laplace transforms:

https://www.youtube.com/watch?v=zvbdoSeGAgI

The whole lecture series is good. the Laplace transform (and other
integral transforms too) are, in general, tools for solving differential
equations. So a refresh on ODEs may be helpful
Yeah well I just replace \'s\' with \'i*w\' (omega.. angular frequency) and
Laplace transforms are fine. My problem is that it\'s easy to dig down
into the math (algebra) and lose a sense of what is going on.
I sorta need the math after I understand it.

George H.

Do you have a particular example of what in the process of
\"understanding\" is a sticking-point?

All that\'s happening is that the integro-differential equations of LTI
circuits or systems in the time domain are being converted to algebraic
ones. And then once the equation is solved in the s domain you can run
the machine backwards and get the solution in the time domain again, if
you want.

The reason you can \"read\" the frequency response in the s domain by
making that substitution and taking the magnitude is because convolution
is the same as multiplication there, and the Laplace transform of the
unit impulse is 1.

In the time domain you\'d get the frequency response by convolution of
the time-domain equation with the unit impulse, in the s domain that
work is mostly already done for you as-is just by virtue of the
transformation process.

Both functions in both domains must have equal power spectral densities
so it\'s still the same system except the implicit convolution acting on
an s-domain transfer function has made the variable \"s\" equivalent to
complex frequency. hence you can make that substitution and it works out.

Sometimes you have to do algebra to get equations in the s domain in the
form of a transfer function between input and output and find magnitudes
and phases, but there\'s nothing really interesting in the algebra of
that itself, it\'s just a mechanical process.

 

[bitrex]

On 8/20/2020 5:21 PM, bitrex wrote:

On 8/19/2020 11:05 AM, George Herold wrote:
On Tuesday, August 18, 2020 at 3:05:56 PM UTC-4, bitrex wrote:
On 8/17/2020 11:53 AM, George Herold wrote:
On Sunday, August 16, 2020 at 11:14:22 AM UTC-4,
jla...@highlandsniptechnology.com wrote:
On Sun, 16 Aug 2020 07:53:41 -0700 (PDT), Lasse Langwadt Christensen
langwadt@fonz.dk> wrote:

sųndag den 16. august 2020 kl. 16.31.14 UTC+2 skrev Jan Panteltje:
On a sunny day (Sat, 15 Aug 2020 22:46:45 -0700 (PDT)) it
happened Ricketty C
gnuarm.deletethisbit@gmail.com> wrote in
d2d879c1-cf13-42f8-9727-8ef27dc2dc65o@googlegroups.com>:


He shows the only difference between patient triggered and
machine triggered
waveforms is the negative pressure from the patient trying to
draw air in
at the very start of the cycle.  His diagrams are pretty poor
with no registration
between the various points on different parameters, but he gets
across
the main points.  You can do a Google search to find other much
better
diagrams.  I don\'t think there are any new concepts to an engineer.

No experience with these things
but from _my_ life I  know breathing is related to oxygen level
in the blood.

not really, your breathing is mostly related to the amount of CO2
in your lungs
that\'s why breathing something like pure nitrogen will kill you
without you
even noticing

I wonder how many old ladies ricky\'s team plans to kill, trying to
learn PIDs and stuff.

Do you know any good control \'theory/practice\' books.  I\'ve got a
few, but
I tend to get a little lost in the Laplace transforms, And would
love something with a more \'hands on\' feel, an AoE type of book.

Tim Wescott\'s book is fine.
https://www.wescottdesign.com/actfes/actfes.html

Would you enjoy this fine series from MIT on ordinary differential
equations including Laplace transforms:

https://www.youtube.com/watch?v=zvbdoSeGAgI

The whole lecture series is good. the Laplace transform (and other
integral transforms too) are, in general, tools for solving differential
equations. So a refresh on ODEs may be helpful
Yeah well I just replace \'s\' with \'i*w\' (omega.. angular frequency) and
Laplace transforms are fine.  My problem is that it\'s easy to dig down
into the math (algebra) and lose a sense of what is going on.
I sorta need the math after I understand it.

George H.

Do you have a particular example of what in the process of
\"understanding\" is a sticking-point?

All that\'s happening is that the integro-differential equations of LTI
circuits or systems in the time domain are being converted to algebraic
ones. And then once the equation is solved in the s domain you can run
the machine backwards and get the solution in the time domain again, if
you want.

The reason you can \"read\" the frequency response in the s domain by
making that substitution and taking the magnitude is because convolution
is the same as multiplication there, and the Laplace transform of the
unit impulse is 1.

In the time domain you\'d get the frequency response by convolution of
the time-domain equation with the unit impulse, in the s domain that
work is mostly already done for you as-is just by virtue of the
transformation process.

Both functions in both domains must have equal power spectral densities
so it\'s still the same system except the implicit convolution acting on
an s-domain transfer function has made the variable \"s\" equivalent to
complex frequency. hence you can make that substitution and it works out.

Sometimes you have to do algebra to get equations in the s domain in the
form of a transfer function between input and output and find magnitudes
and phases, but there\'s nothing really interesting in the algebra of
that itself, it\'s just a mechanical process.

Wes Hayward\'s book \"Introduction to RF Design\" has a section about how
to apply it to designing a PLL. The intuition comes in via knowing a PLL
should have certain parts with certain characteristics. There\'s a VCO. A
phase detector. Loop filter. Feedback loop around.

And you figure out what the transfer functions of those are in general,
and the whole loop in combination. and you construct an equation for the
loop transfer function, with some unknown coefficients. What values the
coefficient have to take to make the loop stable and do what you want is
where the math/engineering comes in, you have to analyze the equation,
make plots of various values to figure out what the coefficients should
be to get the result you want.

Doesn\'t require a lot more \"understanding\" than that! \"it is what it is\"

 

[George Herold]

On Thursday, August 20, 2020 at 5:21:22 PM UTC-4, bitrex wrote:

On 8/19/2020 11:05 AM, George Herold wrote:
On Tuesday, August 18, 2020 at 3:05:56 PM UTC-4, bitrex wrote:
On 8/17/2020 11:53 AM, George Herold wrote:
On Sunday, August 16, 2020 at 11:14:22 AM UTC-4, jla...@highlandsniptechnology.com wrote:
On Sun, 16 Aug 2020 07:53:41 -0700 (PDT), Lasse Langwadt Christensen
langwadt@fonz.dk> wrote:

sųndag den 16. august 2020 kl. 16.31.14 UTC+2 skrev Jan Panteltje:
On a sunny day (Sat, 15 Aug 2020 22:46:45 -0700 (PDT)) it happened Ricketty C
gnuarm.deletethisbit@gmail.com> wrote in
d2d879c1-cf13-42f8-9727-8ef27dc2dc65o@googlegroups.com>:


He shows the only difference between patient triggered and machine triggered
waveforms is the negative pressure from the patient trying to draw air in
at the very start of the cycle. His diagrams are pretty poor with no registration
between the various points on different parameters, but he gets across
the main points. You can do a Google search to find other much better
diagrams. I don\'t think there are any new concepts to an engineer.

No experience with these things
but from _my_ life I know breathing is related to oxygen level in the blood.

not really, your breathing is mostly related to the amount of CO2 in your lungs
that\'s why breathing something like pure nitrogen will kill you without you
even noticing

I wonder how many old ladies ricky\'s team plans to kill, trying to
learn PIDs and stuff.

Do you know any good control \'theory/practice\' books. I\'ve got a few, but
I tend to get a little lost in the Laplace transforms, And would
love something with a more \'hands on\' feel, an AoE type of book.

Tim Wescott\'s book is fine.
https://www.wescottdesign.com/actfes/actfes.html

Would you enjoy this fine series from MIT on ordinary differential
equations including Laplace transforms:

https://www.youtube.com/watch?v=zvbdoSeGAgI

The whole lecture series is good. the Laplace transform (and other
integral transforms too) are, in general, tools for solving differential
equations. So a refresh on ODEs may be helpful
Yeah well I just replace \'s\' with \'i*w\' (omega.. angular frequency) and
Laplace transforms are fine. My problem is that it\'s easy to dig down
into the math (algebra) and lose a sense of what is going on.
I sorta need the math after I understand it.

George H.

Do you have a particular example of what in the process of
\"understanding\" is a sticking-point?

Not at the moment. I\'ve done mostly thermal loops, which
are easy (no thermal \'momentum/ inductance\'). I guess the
perennial question in a thermal loop is where to put the
heater/ TEC / cooler (plant) and where to put the temperature sensor.

George H.

All that\'s happening is that the integro-differential equations of LTI
circuits or systems in the time domain are being converted to algebraic
ones. And then once the equation is solved in the s domain you can run
the machine backwards and get the solution in the time domain again, if
you want.

The reason you can \"read\" the frequency response in the s domain by
making that substitution and taking the magnitude is because convolution
is the same as multiplication there, and the Laplace transform of the
unit impulse is 1.

In the time domain you\'d get the frequency response by convolution of
the time-domain equation with the unit impulse, in the s domain that
work is mostly already done for you as-is just by virtue of the
transformation process.

Both functions in both domains must have equal power spectral densities
so it\'s still the same system except the implicit convolution acting on
an s-domain transfer function has made the variable \"s\" equivalent to
complex frequency. hence you can make that substitution and it works out.

Sometimes you have to do algebra to get equations in the s domain in the
form of a transfer function between input and output and find magnitudes
and phases, but there\'s nothing really interesting in the algebra of
that itself, it\'s just a mechanical process.

 

[Ricketty C]

On Thursday, August 20, 2020 at 9:22:01 PM UTC-4, George Herold wrote:

On Thursday, August 20, 2020 at 5:21:22 PM UTC-4, bitrex wrote:
On 8/19/2020 11:05 AM, George Herold wrote:
On Tuesday, August 18, 2020 at 3:05:56 PM UTC-4, bitrex wrote:
On 8/17/2020 11:53 AM, George Herold wrote:
On Sunday, August 16, 2020 at 11:14:22 AM UTC-4, jla...@highlandsniptechnology.com wrote:
On Sun, 16 Aug 2020 07:53:41 -0700 (PDT), Lasse Langwadt Christensen
langwadt@fonz.dk> wrote:

sųndag den 16. august 2020 kl. 16.31.14 UTC+2 skrev Jan Panteltje:
On a sunny day (Sat, 15 Aug 2020 22:46:45 -0700 (PDT)) it happened Ricketty C
gnuarm.deletethisbit@gmail.com> wrote in
d2d879c1-cf13-42f8-9727-8ef27dc2dc65o@googlegroups.com>:


He shows the only difference between patient triggered and machine triggered
waveforms is the negative pressure from the patient trying to draw air in
at the very start of the cycle. His diagrams are pretty poor with no registration
between the various points on different parameters, but he gets across
the main points. You can do a Google search to find other much better
diagrams. I don\'t think there are any new concepts to an engineer.

No experience with these things
but from _my_ life I know breathing is related to oxygen level in the blood.

not really, your breathing is mostly related to the amount of CO2 in your lungs
that\'s why breathing something like pure nitrogen will kill you without you
even noticing

I wonder how many old ladies ricky\'s team plans to kill, trying to
learn PIDs and stuff.

Do you know any good control \'theory/practice\' books. I\'ve got a few, but
I tend to get a little lost in the Laplace transforms, And would
love something with a more \'hands on\' feel, an AoE type of book.

Tim Wescott\'s book is fine.
https://www.wescottdesign.com/actfes/actfes.html

Would you enjoy this fine series from MIT on ordinary differential
equations including Laplace transforms:

https://www.youtube.com/watch?v=zvbdoSeGAgI

The whole lecture series is good. the Laplace transform (and other
integral transforms too) are, in general, tools for solving differential
equations. So a refresh on ODEs may be helpful
Yeah well I just replace \'s\' with \'i*w\' (omega.. angular frequency) and
Laplace transforms are fine. My problem is that it\'s easy to dig down
into the math (algebra) and lose a sense of what is going on.
I sorta need the math after I understand it.

George H.

Do you have a particular example of what in the process of
\"understanding\" is a sticking-point?

Not at the moment. I\'ve done mostly thermal loops, which
are easy (no thermal \'momentum/ inductance\'). I guess the
perennial question in a thermal loop is where to put the
heater/ TEC / cooler (plant) and where to put the temperature sensor.

Earlier it was pointed out that delays in the system can impact loop stability. I believe thermal systems can have such delays, for example, when the heater itself has significant thermal mass and the object being heated also has thermal mass with some thermal impedance between.

Such a system can be stabilized by using multiple loops. A fast loop to control the temperature of the first thermal mass and a second, slower loop to adjust the set point of the first loop ultimately managing the temperature of the second thermal mass.

I suppose a single loop with a slow response would work, but I expect it will require a slower response than the two loop design to deal with integrator wind up because the inner loop would allow the set point to ramp up more quickly without ramping up the outer loop integrator. Yes, no?

Today in the conference call I explained the idea of reducing the overshoot by instead of limiting the slew rate of the PID controller, not driving it with an abrupt step function. Rather a slope can be used appropriate for the desired ramp up of the controlled variable. Rather than focus on making the controller manage the rate, give it the rate it should follow.

--

Rick C.

+-+ Get 1,000 miles of free Supercharging
+-+ Tesla referral code - https://ts.la/richard11209

 

[Tom Gardner]

On 21/08/20 06:40, Ricketty C wrote:

On Thursday, August 20, 2020 at 9:22:01 PM UTC-4, George Herold wrote:
On Thursday, August 20, 2020 at 5:21:22 PM UTC-4, bitrex wrote:
On 8/19/2020 11:05 AM, George Herold wrote:
On Tuesday, August 18, 2020 at 3:05:56 PM UTC-4, bitrex wrote:
On 8/17/2020 11:53 AM, George Herold wrote:
On Sunday, August 16, 2020 at 11:14:22 AM UTC-4,
jla...@highlandsniptechnology.com wrote:
On Sun, 16 Aug 2020 07:53:41 -0700 (PDT), Lasse Langwadt
Christensen <langwadt@fonz.dk> wrote:

sųndag den 16. august 2020 kl. 16.31.14 UTC+2 skrev Jan
Panteltje:
On a sunny day (Sat, 15 Aug 2020 22:46:45 -0700 (PDT)) it
happened Ricketty C <gnuarm.deletethisbit@gmail.com> wrote
in <d2d879c1-cf13-42f8-9727-8ef27dc2dc65o@googlegroups.com>:


He shows the only difference between patient triggered and
machine triggered waveforms is the negative pressure from
the patient trying to draw air in at the very start of the
cycle. His diagrams are pretty poor with no registration
between the various points on different parameters, but he
gets across the main points. You can do a Google search to
find other much better diagrams. I don\'t think there are
any new concepts to an engineer.

No experience with these things but from _my_ life I know
breathing is related to oxygen level in the blood.

not really, your breathing is mostly related to the amount of
CO2 in your lungs that\'s why breathing something like pure
nitrogen will kill you without you even noticing

I wonder how many old ladies ricky\'s team plans to kill, trying
to learn PIDs and stuff.

Do you know any good control \'theory/practice\' books. I\'ve got a
few, but I tend to get a little lost in the Laplace transforms, And
would love something with a more \'hands on\' feel, an AoE type of
book.

Tim Wescott\'s book is fine.
https://www.wescottdesign.com/actfes/actfes.html

Would you enjoy this fine series from MIT on ordinary differential
equations including Laplace transforms:

https://www.youtube.com/watch?v=zvbdoSeGAgI

The whole lecture series is good. the Laplace transform (and other
integral transforms too) are, in general, tools for solving
differential equations. So a refresh on ODEs may be helpful
Yeah well I just replace \'s\' with \'i*w\' (omega.. angular frequency)
and Laplace transforms are fine. My problem is that it\'s easy to dig
down into the math (algebra) and lose a sense of what is going on. I
sorta need the math after I understand it.

George H.

Do you have a particular example of what in the process of
\"understanding\" is a sticking-point?

Not at the moment. I\'ve done mostly thermal loops, which are easy (no
thermal \'momentum/ inductance\'). I guess the perennial question in a
thermal loop is where to put the heater/ TEC / cooler (plant) and where to
put the temperature sensor.

Earlier it was pointed out that delays in the system can impact loop
stability. I believe thermal systems can have such delays, for example, when
the heater itself has significant thermal mass and the object being heated
also has thermal mass with some thermal impedance between.

Such a system can be stabilized by using multiple loops. A fast loop to
control the temperature of the first thermal mass and a second, slower loop
to adjust the set point of the first loop ultimately managing the temperature
of the second thermal mass.

I suppose a single loop with a slow response would work, but I expect it will
require a slower response than the two loop design to deal with integrator
wind up because the inner loop would allow the set point to ramp up more
quickly without ramping up the outer loop integrator. Yes, no?

Today in the conference call I explained the idea of reducing the overshoot
by instead of limiting the slew rate of the PID controller, not driving it
with an abrupt step function. Rather a slope can be used appropriate for the
desired ramp up of the controlled variable. Rather than focus on making the
controller manage the rate, give it the rate it should follow.

There will be step changes when ventilating a patient.
Obvious ones are when the patient stops or starts trying
to breath.

Gently reacting to a patient that no longer inspires and
expires is likely to lead to a long-lasting expiration.

Ditto inflating a patient that is trying to take control
of their life.

 

[Ricketty C]

On Friday, August 21, 2020 at 5:36:58 AM UTC-4, Tom Gardner wrote:

On 21/08/20 06:40, Ricketty C wrote:
On Thursday, August 20, 2020 at 9:22:01 PM UTC-4, George Herold wrote:
On Thursday, August 20, 2020 at 5:21:22 PM UTC-4, bitrex wrote:
On 8/19/2020 11:05 AM, George Herold wrote:
On Tuesday, August 18, 2020 at 3:05:56 PM UTC-4, bitrex wrote:
On 8/17/2020 11:53 AM, George Herold wrote:
On Sunday, August 16, 2020 at 11:14:22 AM UTC-4,
jla...@highlandsniptechnology.com wrote:
On Sun, 16 Aug 2020 07:53:41 -0700 (PDT), Lasse Langwadt
Christensen <langwadt@fonz.dk> wrote:

sųndag den 16. august 2020 kl. 16.31.14 UTC+2 skrev Jan
Panteltje:
On a sunny day (Sat, 15 Aug 2020 22:46:45 -0700 (PDT)) it
happened Ricketty C <gnuarm.deletethisbit@gmail.com> wrote
in <d2d879c1-cf13-42f8-9727-8ef27dc2dc65o@googlegroups.com>:


He shows the only difference between patient triggered and
machine triggered waveforms is the negative pressure from
the patient trying to draw air in at the very start of the
cycle. His diagrams are pretty poor with no registration
between the various points on different parameters, but he
gets across the main points. You can do a Google search to
find other much better diagrams. I don\'t think there are
any new concepts to an engineer.

No experience with these things but from _my_ life I know
breathing is related to oxygen level in the blood.

not really, your breathing is mostly related to the amount of
CO2 in your lungs that\'s why breathing something like pure
nitrogen will kill you without you even noticing

I wonder how many old ladies ricky\'s team plans to kill, trying
to learn PIDs and stuff.

Do you know any good control \'theory/practice\' books. I\'ve got a
few, but I tend to get a little lost in the Laplace transforms, And
would love something with a more \'hands on\' feel, an AoE type of
book.

Tim Wescott\'s book is fine.
https://www.wescottdesign.com/actfes/actfes.html

Would you enjoy this fine series from MIT on ordinary differential
equations including Laplace transforms:

https://www.youtube.com/watch?v=zvbdoSeGAgI

The whole lecture series is good. the Laplace transform (and other
integral transforms too) are, in general, tools for solving
differential equations. So a refresh on ODEs may be helpful
Yeah well I just replace \'s\' with \'i*w\' (omega.. angular frequency)
and Laplace transforms are fine. My problem is that it\'s easy to dig
down into the math (algebra) and lose a sense of what is going on. I
sorta need the math after I understand it.

George H.

Do you have a particular example of what in the process of
\"understanding\" is a sticking-point?

Not at the moment. I\'ve done mostly thermal loops, which are easy (no
thermal \'momentum/ inductance\'). I guess the perennial question in a
thermal loop is where to put the heater/ TEC / cooler (plant) and where to
put the temperature sensor.

Earlier it was pointed out that delays in the system can impact loop
stability. I believe thermal systems can have such delays, for example, when
the heater itself has significant thermal mass and the object being heated
also has thermal mass with some thermal impedance between.

Such a system can be stabilized by using multiple loops. A fast loop to
control the temperature of the first thermal mass and a second, slower loop
to adjust the set point of the first loop ultimately managing the temperature
of the second thermal mass.

I suppose a single loop with a slow response would work, but I expect it will
require a slower response than the two loop design to deal with integrator
wind up because the inner loop would allow the set point to ramp up more
quickly without ramping up the outer loop integrator. Yes, no?

Today in the conference call I explained the idea of reducing the overshoot
by instead of limiting the slew rate of the PID controller, not driving it
with an abrupt step function. Rather a slope can be used appropriate for the
desired ramp up of the controlled variable. Rather than focus on making the
controller manage the rate, give it the rate it should follow.

There will be step changes when ventilating a patient.
Obvious ones are when the patient stops or starts trying
to breath.

Gently reacting to a patient that no longer inspires and
expires is likely to lead to a long-lasting expiration.

Ditto inflating a patient that is trying to take control
of their life.

You seem to not understand the issue. Everything has a spec. There is no need for an abrupt spec on any of the parameters. Humans typically don\'t respond to sub-millisecond stimuli other than perhaps light and then just barely. I guess sub-millisecond pressure changes can be noticed when they are in the form of explosions.

Why do people make silly statements about topics they don\'t actually know anything about?

--

Rick C.

++- Get 1,000 miles of free Supercharging
++- Tesla referral code - https://ts.la/richard11209

 

[Tom Gardner]

On 21/08/20 10:57, Ricketty C wrote:

On Friday, August 21, 2020 at 5:36:58 AM UTC-4, Tom Gardner wrote:
On 21/08/20 06:40, Ricketty C wrote:
On Thursday, August 20, 2020 at 9:22:01 PM UTC-4, George Herold wrote:
On Thursday, August 20, 2020 at 5:21:22 PM UTC-4, bitrex wrote:
On 8/19/2020 11:05 AM, George Herold wrote:
On Tuesday, August 18, 2020 at 3:05:56 PM UTC-4, bitrex wrote:
On 8/17/2020 11:53 AM, George Herold wrote:
On Sunday, August 16, 2020 at 11:14:22 AM UTC-4,
jla...@highlandsniptechnology.com wrote:
On Sun, 16 Aug 2020 07:53:41 -0700 (PDT), Lasse Langwadt
Christensen <langwadt@fonz.dk> wrote:

sųndag den 16. august 2020 kl. 16.31.14 UTC+2 skrev Jan
Panteltje:
On a sunny day (Sat, 15 Aug 2020 22:46:45 -0700 (PDT))
it happened Ricketty C <gnuarm.deletethisbit@gmail.com
wrote in
d2d879c1-cf13-42f8-9727-8ef27dc2dc65o@googlegroups.com>:




He shows the only difference between patient triggered and
machine triggered waveforms is the negative pressure
from the patient trying to draw air in at the very
start of the cycle. His diagrams are pretty poor with
no registration between the various points on different
parameters, but he gets across the main points. You
can do a Google search to find other much better
diagrams. I don\'t think there are any new concepts to
an engineer.

No experience with these things but from _my_ life I
know breathing is related to oxygen level in the blood.

not really, your breathing is mostly related to the amount
of CO2 in your lungs that\'s why breathing something like
pure nitrogen will kill you without you even noticing

I wonder how many old ladies ricky\'s team plans to kill,
trying to learn PIDs and stuff.

Do you know any good control \'theory/practice\' books. I\'ve got
a few, but I tend to get a little lost in the Laplace
transforms, And would love something with a more \'hands on\'
feel, an AoE type of book.

Tim Wescott\'s book is fine.
https://www.wescottdesign.com/actfes/actfes.html

Would you enjoy this fine series from MIT on ordinary
differential equations including Laplace transforms:

https://www.youtube.com/watch?v=zvbdoSeGAgI

The whole lecture series is good. the Laplace transform (and
other integral transforms too) are, in general, tools for
solving differential equations. So a refresh on ODEs may be
helpful
Yeah well I just replace \'s\' with \'i*w\' (omega.. angular
frequency) and Laplace transforms are fine. My problem is that
it\'s easy to dig down into the math (algebra) and lose a sense of
what is going on. I sorta need the math after I understand it.

George H.

Do you have a particular example of what in the process of
\"understanding\" is a sticking-point?

Not at the moment. I\'ve done mostly thermal loops, which are easy (no
thermal \'momentum/ inductance\'). I guess the perennial question in a
thermal loop is where to put the heater/ TEC / cooler (plant) and where
to put the temperature sensor.

Earlier it was pointed out that delays in the system can impact loop
stability. I believe thermal systems can have such delays, for example,
when the heater itself has significant thermal mass and the object being
heated also has thermal mass with some thermal impedance between.

Such a system can be stabilized by using multiple loops. A fast loop to
control the temperature of the first thermal mass and a second, slower
loop to adjust the set point of the first loop ultimately managing the
temperature of the second thermal mass.

I suppose a single loop with a slow response would work, but I expect it
will require a slower response than the two loop design to deal with
integrator wind up because the inner loop would allow the set point to
ramp up more quickly without ramping up the outer loop integrator. Yes,
no?

Today in the conference call I explained the idea of reducing the
overshoot by instead of limiting the slew rate of the PID controller, not
driving it with an abrupt step function. Rather a slope can be used
appropriate for the desired ramp up of the controlled variable. Rather
than focus on making the controller manage the rate, give it the rate it
should follow.

There will be step changes when ventilating a patient. Obvious ones are
when the patient stops or starts trying to breath.

Gently reacting to a patient that no longer inspires and expires is likely
to lead to a long-lasting expiration.

Ditto inflating a patient that is trying to take control of their life.

You seem to not understand the issue. Everything has a spec. There is no
need for an abrupt spec on any of the parameters. Humans typically don\'t
respond to sub-millisecond stimuli other than perhaps light and then just
barely. I guess sub-millisecond pressure changes can be noticed when they
are in the form of explosions.

Quoting such numbers indicates you clearly don\'t understand the issues.

Why do people make silly statements about topics they don\'t actually know
anything about?

I built a commercial lung ventilator, a long time ago. How many have you built?

I suspect I have more of a clue about that than you.

 

[Ricketty C]

On Friday, August 21, 2020 at 6:28:40 AM UTC-4, Tom Gardner wrote:

On 21/08/20 10:57, Ricketty C wrote:
On Friday, August 21, 2020 at 5:36:58 AM UTC-4, Tom Gardner wrote:
On 21/08/20 06:40, Ricketty C wrote:
On Thursday, August 20, 2020 at 9:22:01 PM UTC-4, George Herold wrote:
On Thursday, August 20, 2020 at 5:21:22 PM UTC-4, bitrex wrote:
On 8/19/2020 11:05 AM, George Herold wrote:
On Tuesday, August 18, 2020 at 3:05:56 PM UTC-4, bitrex wrote:
On 8/17/2020 11:53 AM, George Herold wrote:
On Sunday, August 16, 2020 at 11:14:22 AM UTC-4,
jla...@highlandsniptechnology.com wrote:
On Sun, 16 Aug 2020 07:53:41 -0700 (PDT), Lasse Langwadt
Christensen <langwadt@fonz.dk> wrote:

sųndag den 16. august 2020 kl. 16.31.14 UTC+2 skrev Jan
Panteltje:
On a sunny day (Sat, 15 Aug 2020 22:46:45 -0700 (PDT))
it happened Ricketty C <gnuarm.deletethisbit@gmail.com
wrote in
d2d879c1-cf13-42f8-9727-8ef27dc2dc65o@googlegroups.com>:




He shows the only difference between patient triggered and
machine triggered waveforms is the negative pressure
from the patient trying to draw air in at the very
start of the cycle. His diagrams are pretty poor with
no registration between the various points on different
parameters, but he gets across the main points. You
can do a Google search to find other much better
diagrams. I don\'t think there are any new concepts to
an engineer.

No experience with these things but from _my_ life I
know breathing is related to oxygen level in the blood.

not really, your breathing is mostly related to the amount
of CO2 in your lungs that\'s why breathing something like
pure nitrogen will kill you without you even noticing

I wonder how many old ladies ricky\'s team plans to kill,
trying to learn PIDs and stuff.

Do you know any good control \'theory/practice\' books. I\'ve got
a few, but I tend to get a little lost in the Laplace
transforms, And would love something with a more \'hands on\'
feel, an AoE type of book.

Tim Wescott\'s book is fine.
https://www.wescottdesign.com/actfes/actfes.html

Would you enjoy this fine series from MIT on ordinary
differential equations including Laplace transforms:

https://www.youtube.com/watch?v=zvbdoSeGAgI

The whole lecture series is good. the Laplace transform (and
other integral transforms too) are, in general, tools for
solving differential equations. So a refresh on ODEs may be
helpful
Yeah well I just replace \'s\' with \'i*w\' (omega.. angular
frequency) and Laplace transforms are fine. My problem is that
it\'s easy to dig down into the math (algebra) and lose a sense of
what is going on. I sorta need the math after I understand it.

George H.

Do you have a particular example of what in the process of
\"understanding\" is a sticking-point?

Not at the moment. I\'ve done mostly thermal loops, which are easy (no
thermal \'momentum/ inductance\'). I guess the perennial question in a
thermal loop is where to put the heater/ TEC / cooler (plant) and where
to put the temperature sensor.

Earlier it was pointed out that delays in the system can impact loop
stability. I believe thermal systems can have such delays, for example,
when the heater itself has significant thermal mass and the object being
heated also has thermal mass with some thermal impedance between.

Such a system can be stabilized by using multiple loops. A fast loop to
control the temperature of the first thermal mass and a second, slower
loop to adjust the set point of the first loop ultimately managing the
temperature of the second thermal mass.

I suppose a single loop with a slow response would work, but I expect it
will require a slower response than the two loop design to deal with
integrator wind up because the inner loop would allow the set point to
ramp up more quickly without ramping up the outer loop integrator. Yes,
no?

Today in the conference call I explained the idea of reducing the
overshoot by instead of limiting the slew rate of the PID controller, not
driving it with an abrupt step function. Rather a slope can be used
appropriate for the desired ramp up of the controlled variable. Rather
than focus on making the controller manage the rate, give it the rate it
should follow.

There will be step changes when ventilating a patient. Obvious ones are
when the patient stops or starts trying to breath.

Gently reacting to a patient that no longer inspires and expires is likely
to lead to a long-lasting expiration.

Ditto inflating a patient that is trying to take control of their life..

You seem to not understand the issue. Everything has a spec. There is no
need for an abrupt spec on any of the parameters. Humans typically don\'t
respond to sub-millisecond stimuli other than perhaps light and then just
barely. I guess sub-millisecond pressure changes can be noticed when they
are in the form of explosions.

Quoting such numbers indicates you clearly don\'t understand the issues.


Why do people make silly statements about topics they don\'t actually know
anything about?

I built a commercial lung ventilator, a long time ago. How many have you built?

I suspect I have more of a clue about that than you.

If you understood the issues you would not make the silly, technically vague, alarmist comments you have made here. The issues have to do with control theory, not medical. There is no medical requirement to drive pressure or air flow in microseconds. What was the step response of the ventilator you designed? I will have to say I\'m impressed that one person can design such a complex device. There are many, many facets to it and typically it would involve many engineers.

This is a perfect example of \"if you\'re not part of the solution, you are part of the problem\". Why are you going on about this? If you want to contribute, why not actually make a contribution. If you just want to rag on things, please go elsewhere.

There are plenty of threads here where people are just ragging on one another ad infinitum. It would be nice to keep the technical threads free of that.

--

Rick C.

+++ Get 1,000 miles of free Supercharging
+++ Tesla referral code - https://ts.la/richard11209

 

[Tom Gardner]

On 21/08/20 16:36, Ricketty C wrote:

On Friday, August 21, 2020 at 6:28:40 AM UTC-4, Tom Gardner wrote:
On 21/08/20 10:57, Ricketty C wrote:
On Friday, August 21, 2020 at 5:36:58 AM UTC-4, Tom Gardner wrote:
On 21/08/20 06:40, Ricketty C wrote:
On Thursday, August 20, 2020 at 9:22:01 PM UTC-4, George Herold
wrote:
On Thursday, August 20, 2020 at 5:21:22 PM UTC-4, bitrex wrote:
On 8/19/2020 11:05 AM, George Herold wrote:
On Tuesday, August 18, 2020 at 3:05:56 PM UTC-4, bitrex wrote:
On 8/17/2020 11:53 AM, George Herold wrote:
On Sunday, August 16, 2020 at 11:14:22 AM UTC-4,
jla...@highlandsniptechnology.com wrote:
On Sun, 16 Aug 2020 07:53:41 -0700 (PDT), Lasse Langwadt
Christensen <langwadt@fonz.dk> wrote:

sųndag den 16. august 2020 kl. 16.31.14 UTC+2 skrev
Jan Panteltje:
On a sunny day (Sat, 15 Aug 2020 22:46:45 -0700
(PDT)) it happened Ricketty C
gnuarm.deletethisbit@gmail.com> wrote in
d2d879c1-cf13-42f8-9727-8ef27dc2dc65o@googlegroups.com>:






He shows the only difference between patient triggered and
machine triggered waveforms is the negative
pressure from the patient trying to draw air in at
the very start of the cycle. His diagrams are
pretty poor with no registration between the
various points on different parameters, but he gets
across the main points. You can do a Google search
to find other much better diagrams. I don\'t think
there are any new concepts to an engineer.

No experience with these things but from _my_ life I
know breathing is related to oxygen level in the
blood.

not really, your breathing is mostly related to the
amount of CO2 in your lungs that\'s why breathing
something like pure nitrogen will kill you without you
even noticing

I wonder how many old ladies ricky\'s team plans to kill,
trying to learn PIDs and stuff.

Do you know any good control \'theory/practice\' books. I\'ve
got a few, but I tend to get a little lost in the Laplace
transforms, And would love something with a more \'hands
on\' feel, an AoE type of book.

Tim Wescott\'s book is fine.
https://www.wescottdesign.com/actfes/actfes.html

Would you enjoy this fine series from MIT on ordinary
differential equations including Laplace transforms:

https://www.youtube.com/watch?v=zvbdoSeGAgI

The whole lecture series is good. the Laplace transform (and
other integral transforms too) are, in general, tools for
solving differential equations. So a refresh on ODEs may be
helpful
Yeah well I just replace \'s\' with \'i*w\' (omega.. angular
frequency) and Laplace transforms are fine. My problem is
that it\'s easy to dig down into the math (algebra) and lose a
sense of what is going on. I sorta need the math after I
understand it.

George H.

Do you have a particular example of what in the process of
\"understanding\" is a sticking-point?

Not at the moment. I\'ve done mostly thermal loops, which are easy
(no thermal \'momentum/ inductance\'). I guess the perennial
question in a thermal loop is where to put the heater/ TEC / cooler
(plant) and where to put the temperature sensor.

Earlier it was pointed out that delays in the system can impact loop
stability. I believe thermal systems can have such delays, for
example, when the heater itself has significant thermal mass and the
object being heated also has thermal mass with some thermal impedance
between.

Such a system can be stabilized by using multiple loops. A fast loop
to control the temperature of the first thermal mass and a second,
slower loop to adjust the set point of the first loop ultimately
managing the temperature of the second thermal mass.

I suppose a single loop with a slow response would work, but I expect
it will require a slower response than the two loop design to deal
with integrator wind up because the inner loop would allow the set
point to ramp up more quickly without ramping up the outer loop
integrator. Yes, no?

Today in the conference call I explained the idea of reducing the
overshoot by instead of limiting the slew rate of the PID controller,
not driving it with an abrupt step function. Rather a slope can be
used appropriate for the desired ramp up of the controlled variable.
Rather than focus on making the controller manage the rate, give it
the rate it should follow.

There will be step changes when ventilating a patient. Obvious ones
are when the patient stops or starts trying to breath.

Gently reacting to a patient that no longer inspires and expires is
likely to lead to a long-lasting expiration.

Ditto inflating a patient that is trying to take control of their
life.

You seem to not understand the issue. Everything has a spec. There is
no need for an abrupt spec on any of the parameters. Humans typically
don\'t respond to sub-millisecond stimuli other than perhaps light and
then just barely. I guess sub-millisecond pressure changes can be
noticed when they are in the form of explosions.

Quoting such numbers indicates you clearly don\'t understand the issues.


Why do people make silly statements about topics they don\'t actually
know anything about?

I built a commercial lung ventilator, a long time ago. How many have you
built?

I suspect I have more of a clue about that than you.

If you understood the issues you would not make the silly, technically vague,
alarmist comments you have made here. The issues have to do with control
theory, not medical. There is no medical requirement to drive pressure or
air flow in microseconds. What was the step response of the ventilator you
designed? I will have to say I\'m impressed that one person can design such a
complex device. There are many, many facets to it and typically it would
involve many engineers.

Wow. So many misconceptions in one paragraph. Let\'s keep it simple.

1) I made no such statement about driving/measuring in microseconds.
2) I made no such statement about being the only person involved,
nor even the only company involved.

You really ought to learn to read only that which is stated,
and not allow your preconceptions to blind you

For the record, the step is the event that a patient has
died or been resurrected. (There are many others, of course)
The event is instantaneous, of course, and flips operation to
*completely* different behavioural *modes*. Determining the
trigger conditions and ensuring appropriate future behaviour
is not trivial.

It took 3 engineers in my company (RTOS infrastructure,
front panel, ventilator control), and several in another
company. The latter knew the ventilation requirements but not
how to design and implement them.

I was the PM, and designed and implemented the ventilator
control.

This is a perfect example of \"if you\'re not part of the solution, you are
part of the problem\". Why are you going on about this? If you want to
contribute, why not actually make a contribution. If you just want to rag on
things, please go elsewhere.

I\'m going to decline in this case; it would be a waste
of my time in two ways:

1) I have tried to educate you before, and found it notably
difficult to get you to think away from your preconceptions.
(cf with the above)

2) this whole effort is doomed to failure, for the non-technical
reasons others have stated.

There are plenty of threads here where people are just ragging on one another
ad infinitum. It would be nice to keep the technical threads free of that.

Yes, we\'ve noticed.

 

[Jan Panteltje]

On a sunny day (Fri, 21 Aug 2020 08:36:27 -0700 (PDT)) it happened Ricketty C
<gnuarm.deletethisbit@gmail.com> wrote in
<8b0ef434-ffbe-48a1-95ab-d3999eb114e3o@googlegroups.com>:

If you understood the issues you would not make the silly, technically vague,
alarmist comments you have made here. The issues have to do with control
theory, not medical. There is no medical requirement to drive pressure or
air flow in microseconds. What was the step response of the ventilator you
designed? I will have to say I\'m impressed that one person can design such
a complex device. There are many, many facets to it and typically it would
involve many engineers.

This is a perfect example of \"if you\'re not part of the solution, you are part
of the problem\". Why are you going on about this? If you want to contribute,
why not actually make a contribution. If you just want to rag on things,
please go elsewhere.

There are plenty of threads here where people are just ragging on one another
ad infinitum. It would be nice to keep the technical threads free of that.

Rick stt

Maybe YOU should simply build the thing, and not get lost in PID control theory.
One can easily measure air pressure and adjust the speed of a motor drive,
especially if it is a stepper, in milliseconds.
Now all you need is knowledge about the human interface to make it follow
a curve.
No PID stuff, just millisecond by millisecond adjustment against a known curve.
No long delays as in thermal heating and overshoot or big flywheels speeding up
or whatever.
Build something, test it on yourself.
Best way to get feedback and FEEL where it needs improvement.
You seem to think you are the only one in the universe who knows how to do things
you have nothing yet, not even a prototype,
math is useless in phantasy.
There is an old joke here:
How many <insert nationality here> guys does it take to screw in a light bulb?
Answer:
5
one to hold the bulb, and 4 to turn the ceiling.

I have been with a big company that actually now makes ventilators for the US,
and the time from idea to production I was told there was 2 weeks.
This thread has been going on and on,
where is your prototype?

No use trying to write code for a control system for a thing you do not even have.
Untestable,
Cool it man.

 

[Ricketty C]

On Friday, August 21, 2020 at 12:12:58 PM UTC-4, Tom Gardner wrote:

On 21/08/20 16:36, Ricketty C wrote:
On Friday, August 21, 2020 at 6:28:40 AM UTC-4, Tom Gardner wrote:
On 21/08/20 10:57, Ricketty C wrote:
On Friday, August 21, 2020 at 5:36:58 AM UTC-4, Tom Gardner wrote:
On 21/08/20 06:40, Ricketty C wrote:
On Thursday, August 20, 2020 at 9:22:01 PM UTC-4, George Herold
wrote:
On Thursday, August 20, 2020 at 5:21:22 PM UTC-4, bitrex wrote:
On 8/19/2020 11:05 AM, George Herold wrote:
On Tuesday, August 18, 2020 at 3:05:56 PM UTC-4, bitrex wrote:
On 8/17/2020 11:53 AM, George Herold wrote:
On Sunday, August 16, 2020 at 11:14:22 AM UTC-4,
jla...@highlandsniptechnology.com wrote:
On Sun, 16 Aug 2020 07:53:41 -0700 (PDT), Lasse Langwadt
Christensen <langwadt@fonz.dk> wrote:

sųndag den 16. august 2020 kl. 16.31.14 UTC+2 skrev
Jan Panteltje:
On a sunny day (Sat, 15 Aug 2020 22:46:45 -0700
(PDT)) it happened Ricketty C
gnuarm.deletethisbit@gmail.com> wrote in
d2d879c1-cf13-42f8-9727-8ef27dc2dc65o@googlegroups.com>:






He shows the only difference between patient triggered and
machine triggered waveforms is the negative
pressure from the patient trying to draw air in at
the very start of the cycle. His diagrams are
pretty poor with no registration between the
various points on different parameters, but he gets
across the main points. You can do a Google search
to find other much better diagrams. I don\'t think
there are any new concepts to an engineer.

No experience with these things but from _my_ life I
know breathing is related to oxygen level in the
blood.

not really, your breathing is mostly related to the
amount of CO2 in your lungs that\'s why breathing
something like pure nitrogen will kill you without you
even noticing

I wonder how many old ladies ricky\'s team plans to kill,
trying to learn PIDs and stuff.

Do you know any good control \'theory/practice\' books. I\'ve
got a few, but I tend to get a little lost in the Laplace
transforms, And would love something with a more \'hands
on\' feel, an AoE type of book.

Tim Wescott\'s book is fine.
https://www.wescottdesign.com/actfes/actfes.html

Would you enjoy this fine series from MIT on ordinary
differential equations including Laplace transforms:

https://www.youtube.com/watch?v=zvbdoSeGAgI

The whole lecture series is good. the Laplace transform (and
other integral transforms too) are, in general, tools for
solving differential equations. So a refresh on ODEs may be
helpful
Yeah well I just replace \'s\' with \'i*w\' (omega.. angular
frequency) and Laplace transforms are fine. My problem is
that it\'s easy to dig down into the math (algebra) and lose a
sense of what is going on. I sorta need the math after I
understand it.

George H.

Do you have a particular example of what in the process of
\"understanding\" is a sticking-point?

Not at the moment. I\'ve done mostly thermal loops, which are easy
(no thermal \'momentum/ inductance\'). I guess the perennial
question in a thermal loop is where to put the heater/ TEC / cooler
(plant) and where to put the temperature sensor.

Earlier it was pointed out that delays in the system can impact loop
stability. I believe thermal systems can have such delays, for
example, when the heater itself has significant thermal mass and the
object being heated also has thermal mass with some thermal impedance
between.

Such a system can be stabilized by using multiple loops. A fast loop
to control the temperature of the first thermal mass and a second,
slower loop to adjust the set point of the first loop ultimately
managing the temperature of the second thermal mass.

I suppose a single loop with a slow response would work, but I expect
it will require a slower response than the two loop design to deal
with integrator wind up because the inner loop would allow the set
point to ramp up more quickly without ramping up the outer loop
integrator. Yes, no?

Today in the conference call I explained the idea of reducing the
overshoot by instead of limiting the slew rate of the PID controller,
not driving it with an abrupt step function. Rather a slope can be
used appropriate for the desired ramp up of the controlled variable..
Rather than focus on making the controller manage the rate, give it
the rate it should follow.

There will be step changes when ventilating a patient. Obvious ones
are when the patient stops or starts trying to breath.

Gently reacting to a patient that no longer inspires and expires is
likely to lead to a long-lasting expiration.

Ditto inflating a patient that is trying to take control of their
life.

You seem to not understand the issue. Everything has a spec. There is
no need for an abrupt spec on any of the parameters. Humans typically
don\'t respond to sub-millisecond stimuli other than perhaps light and
then just barely. I guess sub-millisecond pressure changes can be
noticed when they are in the form of explosions.

Quoting such numbers indicates you clearly don\'t understand the issues..


Why do people make silly statements about topics they don\'t actually
know anything about?

I built a commercial lung ventilator, a long time ago. How many have you
built?

I suspect I have more of a clue about that than you.

If you understood the issues you would not make the silly, technically vague,
alarmist comments you have made here. The issues have to do with control
theory, not medical. There is no medical requirement to drive pressure or
air flow in microseconds. What was the step response of the ventilator you
designed? I will have to say I\'m impressed that one person can design such a
complex device. There are many, many facets to it and typically it would
involve many engineers.

Wow. So many misconceptions in one paragraph. Let\'s keep it simple.

1) I made no such statement about driving/measuring in microseconds.

I did and then you replied that I didn\'t understand \"the issues\". That is the issue you initially responded to. I pointed out the difficulty of designing a controller to provide an adequate step response without overshoot can be mitigated by not feeding the controller an abrupt step function. From there on you disagreed with everything I wrote to clarify the issue. You are just wrong about this. It\'s time to stop back peddling and accept that.

2) I made no such statement about being the only person involved,
nor even the only company involved.

You really ought to learn to read only that which is stated,
and not allow your preconceptions to blind you

Here is what you posted....

\"I built a commercial lung ventilator, a long time ago.\"

Where do you indicate you were not the only person involved? \"I built\" implies you and you alone. My response was a prod because I knew it was not you alone. Do I really need to explain the subtleties of the English language to you?

For the record, the step is the event that a patient has
died or been resurrected. (There are many others, of course)
The event is instantaneous, of course, and flips operation to
*completely* different behavioural *modes*. Determining the
trigger conditions and ensuring appropriate future behaviour
is not trivial.

Now you are being silly. The step input is asking the machine to provide 0 pressure, then raising it to the set value for the next sample. Expecting it to respond without overshoot is a tall request when the thing being controlled (the system of machine and patient) varies from case to case. Asking an operator to tune the PID parameters is a bit much when it is not needed. The rise time and overshoot specs can be met more easily by feeding the control loop a set of steps of initially high, but sequentially decreasing value allowing the control loop to follow the request without excessive wind up of the I term and minimal overshoot for a wider range of patient parameters.

It took 3 engineers in my company (RTOS infrastructure,
front panel, ventilator control), and several in another
company. The latter knew the ventilation requirements but not
how to design and implement them.

I was the PM, and designed and implemented the ventilator
control.

Excellent. Then you should understand everything I\'ve posted.

This is a perfect example of \"if you\'re not part of the solution, you are
part of the problem\". Why are you going on about this? If you want to
contribute, why not actually make a contribution. If you just want to rag on
things, please go elsewhere.

I\'m going to decline in this case; it would be a waste
of my time in two ways:

1) I have tried to educate you before, and found it notably
difficult to get you to think away from your preconceptions.
(cf with the above)

2) this whole effort is doomed to failure, for the non-technical
reasons others have stated.

Obviously it is not a complete waste of your time or you would not be making these lengthy posts. I suspect it is more a matter of recognizing that your useful contributions are limited. So instead you are blustering. You could contribute to the project without ever dealing with me and my limited abilities to learn.

There are plenty of threads here where people are just ragging on one another
ad infinitum. It would be nice to keep the technical threads free of that.

Yes, we\'ve noticed.

And yet you continue to use bandwidth to continue the conversation just so you can tell me how defective I am, but never actually making any technical points. None at all - in spite of your claims of superior knowledge. I still gain something from these discussions. They help me clarify my position by learning from your mistakes.

Thank you.

--

Rick C.

---- Get 1,000 miles of free Supercharging
---- Tesla referral code - https://ts.la/richard11209

 

[Ricketty C]

On Friday, August 21, 2020 at 12:46:47 PM UTC-4, Jan Panteltje wrote:

On a sunny day (Fri, 21 Aug 2020 08:36:27 -0700 (PDT)) it happened Ricketty C
gnuarm.deletethisbit@gmail.com> wrote in
8b0ef434-ffbe-48a1-95ab-d3999eb114e3o@googlegroups.com>:

If you understood the issues you would not make the silly, technically vague,
alarmist comments you have made here. The issues have to do with control
theory, not medical. There is no medical requirement to drive pressure or
air flow in microseconds. What was the step response of the ventilator you
designed? I will have to say I\'m impressed that one person can design such
a complex device. There are many, many facets to it and typically it would
involve many engineers.

This is a perfect example of \"if you\'re not part of the solution, you are part
of the problem\". Why are you going on about this? If you want to contribute,
why not actually make a contribution. If you just want to rag on things,
please go elsewhere.

There are plenty of threads here where people are just ragging on one another
ad infinitum. It would be nice to keep the technical threads free of that.

Rick stt

Maybe YOU should simply build the thing, and not get lost in PID control theory.
One can easily measure air pressure and adjust the speed of a motor drive,
especially if it is a stepper, in milliseconds.
Now all you need is knowledge about the human interface to make it follow
a curve.
No PID stuff, just millisecond by millisecond adjustment against a known curve.
No long delays as in thermal heating and overshoot or big flywheels speeding up
or whatever.
Build something, test it on yourself.
Best way to get feedback and FEEL where it needs improvement.
You seem to think you are the only one in the universe who knows how to do things
you have nothing yet, not even a prototype,
math is useless in phantasy.
There is an old joke here:
How many <insert nationality here> guys does it take to screw in a light bulb?
Answer:
5
one to hold the bulb, and 4 to turn the ceiling.

I have been with a big company that actually now makes ventilators for the US,
and the time from idea to production I was told there was 2 weeks.
This thread has been going on and on,
where is your prototype?

No use trying to write code for a control system for a thing you do not even have.
Untestable,
Cool it man.

You are a trip. You literally know nothing about the project and yet you talk about there being no prototype, etc, etc, etc.

What type of acid are you on today???

This group is largely as Larkin describes it. There are on occasion a few who are willing to consider a thought. Many more here are just a scene from 2001.

https://www.youtube.com/watch?v=mM6OIlreneA

If you have nothing to contribute to the discussion, why post?

--

Rick C.

---+ Get 1,000 miles of free Supercharging
---+ Tesla referral code - https://ts.la/richard11209

 

[Jan Panteltje]

On a sunny day (Fri, 21 Aug 2020 10:01:43 -0700 (PDT)) it happened Ricketty C
<gnuarm.deletethisbit@gmail.com> wrote in
<95d32c47-2cb3-40fd-aab3-7d7c5e3861ado@googlegroups.com>:

>You are a trip. You literally know nothing about the project and yet you talk about there being no prototype, etc, etc, etc.

Yea, you keep telling that to every body.
Consider visiting a shrink.