Help please w/ electromagnetic slip clutch

Guest
Everybody,
I'm working on a project that needs a slip clutch or brake or
something. I'm turning handwheels that need some sort of instantly
variable resistance to turning . Anywhere from 0 to 40 inch pounds. I
have been looking at magnetic particle clutches and brakes, eddy
current brakes, and disc type clutches and brakes. The magnetic
particle brakes would seem to be a good solution except that the ones
I have seen that can provide enough drag have too much drag when not
energized and have too large a diameter. About 3 inches diameter by
about 3.5 inches long is the space the clutch or brake must fit in. I
am considering rolling my own devices but am not sure how I would do
it. Maybe some sort of generator feeding a resistive load. By varying
the field strength the resistance to rotation would increase. Whatever
the solution is the resistance to rotation must be linear to the
current that actuates the device. That's one of the reasons I like the
magnetic particle barkes.
Thanks,
Eric
 
On Thursday, February 11, 2016 at 2:26:39 PM UTC-5, et...@whidbey.com wrote:
Everybody,
I'm working on a project that needs a slip clutch or brake or
something. I'm turning handwheels that need some sort of instantly
variable resistance to turning . Anywhere from 0 to 40 inch pounds. I
have been looking at magnetic particle clutches and brakes, eddy
current brakes, and disc type clutches and brakes. The magnetic
particle brakes would seem to be a good solution except that the ones
I have seen that can provide enough drag have too much drag when not
energized and have too large a diameter. About 3 inches diameter by
about 3.5 inches long is the space the clutch or brake must fit in. I
am considering rolling my own devices but am not sure how I would do
it. Maybe some sort of generator feeding a resistive load. By varying
the field strength the resistance to rotation would increase. Whatever
the solution is the resistance to rotation must be linear to the
current that actuates the device. That's one of the reasons I like the
magnetic particle barkes.
Thanks,
Eric
Click to expand...

I never heard of magnetic particle brakes. (I did google it)
The problem with a generator or an eddy current thing, is that
the damping will be proportional to the velocity, and I don't think you want
that. You want variable friction..(I think) just something that rubs?

George H.
 
In article <jdopbbdkheb8gd8uvuis5rauq0s01cfcum@4ax.com>,
etpm@whidbey.com says...

[snip]

the field strength the resistance to rotation would increase. Whatever
the solution is the resistance to rotation must be linear to the
current that actuates the device. That's one of the reasons I like the
magnetic particle barkes.
Click to expand...

As an alternative to a current-proportional
clutch, could you adopt a PWM system, to run
your device more like the anti-lock brakes
on a vehicle?

--- news://freenews.netfront.net/ - complaints: news@netfront.net ---
 
On Thu, 11 Feb 2016 11:32:50 -0800, etpm@whidbey.com wrote:

Everybody,
I'm working on a project that needs a slip clutch or brake or
something. I'm turning handwheels that need some sort of instantly
variable resistance to turning . Anywhere from 0 to 40 inch pounds. I
have been looking at magnetic particle clutches and brakes, eddy
current brakes, and disc type clutches and brakes. The magnetic
particle brakes would seem to be a good solution except that the ones
I have seen that can provide enough drag have too much drag when not
energized and have too large a diameter. About 3 inches diameter by
about 3.5 inches long is the space the clutch or brake must fit in. I
am considering rolling my own devices but am not sure how I would do
it. Maybe some sort of generator feeding a resistive load. By varying
the field strength the resistance to rotation would increase. Whatever
the solution is the resistance to rotation must be linear to the
current that actuates the device. That's one of the reasons I like the
magnetic particle barkes.
Thanks,
Eric
Click to expand...

A simple DC motor will do it. Not a generator, but a motor.
It must rotate though, cannot stay long in the same position.
Would wear out the brushes.


w.
 
On Fri, 12 Feb 2016 10:57:47 +0100, Helmut Wabnig <hwabnig@.- ---
-.dotat> wrote:

On Thu, 11 Feb 2016 11:32:50 -0800, etpm@whidbey.com wrote:

Everybody,
I'm working on a project that needs a slip clutch or brake or
something. I'm turning handwheels that need some sort of instantly
variable resistance to turning . Anywhere from 0 to 40 inch pounds. I
have been looking at magnetic particle clutches and brakes, eddy
current brakes, and disc type clutches and brakes. The magnetic
particle brakes would seem to be a good solution except that the ones
I have seen that can provide enough drag have too much drag when not
energized and have too large a diameter. About 3 inches diameter by
about 3.5 inches long is the space the clutch or brake must fit in. I
am considering rolling my own devices but am not sure how I would do
it. Maybe some sort of generator feeding a resistive load. By varying
the field strength the resistance to rotation would increase. Whatever
the solution is the resistance to rotation must be linear to the
current that actuates the device. That's one of the reasons I like the
magnetic particle barkes.
Thanks,
Eric

A simple DC motor will do it. Not a generator, but a motor.
It must rotate though, cannot stay long in the same position.
Would wear out the brushes.


w.
Click to expand...
Greetings Helmut,
I posted the same message on rcm that I posted here. Jon Elson
suggested using a motor too. His idea is to put a small resistance in
series with the main servo and connect the small handwheel motor in
parallel with the resistor. He's not sure it will work. Is his
thinking sound? If so then I will try it out and report back here and
on rcm.
Cheers,
Eric
 
On Thu, 11 Feb 2016 20:19:44 -0800 (PST), jurb6006@gmail.com wrote:

This sounds like a job for hydraulics.
Hydraulics would work but I won't be using any hydraulics.
Click to expand...
 
On Fri, 12 Feb 2016 11:24:14 -0800, etpm wrote:

On Fri, 12 Feb 2016 10:57:47 +0100, Helmut Wabnig <hwabnig@.- ---
-.dotat> wrote:

On Thu, 11 Feb 2016 11:32:50 -0800, etpm@whidbey.com wrote:

Everybody,
I'm working on a project that needs a slip clutch or brake or
something. I'm turning handwheels that need some sort of instantly
variable resistance to turning . Anywhere from 0 to 40 inch pounds. I
have been looking at magnetic particle clutches and brakes, eddy
current brakes, and disc type clutches and brakes. The magnetic
particle brakes would seem to be a good solution except that the ones I
have seen that can provide enough drag have too much drag when not
energized and have too large a diameter. About 3 inches diameter by
about 3.5 inches long is the space the clutch or brake must fit in. I
am considering rolling my own devices but am not sure how I would do
it. Maybe some sort of generator feeding a resistive load. By varying
the field strength the resistance to rotation would increase. Whatever
the solution is the resistance to rotation must be linear to the
current that actuates the device. That's one of the reasons I like the
magnetic particle barkes.
Thanks,
Eric

A simple DC motor will do it. Not a generator, but a motor. It must
rotate though, cannot stay long in the same position.
Would wear out the brushes.


w.
Greetings Helmut,
I posted the same message on rcm that I posted here.
Click to expand...

Cross-posting would have been appropriate in this case.

Jon Elson suggested
using a motor too. His idea is to put a small resistance in series with
the main servo and connect the small handwheel motor in parallel with
the resistor. He's not sure it will work. Is his thinking sound? If so
then I will try it out and report back here and on rcm.
Click to expand...

That's basically a really crappy way of doing what I suggested. Using a
current sense resistor and a current amplifier to drive your handwheel
motor is a good way of doing my suggested "echo the current" thing.

The "motor in parallel with a resistor" will tend to have a torque that's
proportional both to how hard the servo motor is pushing and to how fast
you're rotating the handwheel -- I don't think that's what you want.

--
www.wescottdesign.com
 
On Fri, 12 Feb 2016 14:09:23 -0600, Tim Wescott <tim@seemywebsite.com>
wrote:

On Fri, 12 Feb 2016 11:24:14 -0800, etpm wrote:

On Fri, 12 Feb 2016 10:57:47 +0100, Helmut Wabnig <hwabnig@.- ---
-.dotat> wrote:

On Thu, 11 Feb 2016 11:32:50 -0800, etpm@whidbey.com wrote:

Everybody,
I'm working on a project that needs a slip clutch or brake or
something. I'm turning handwheels that need some sort of instantly
variable resistance to turning . Anywhere from 0 to 40 inch pounds. I
have been looking at magnetic particle clutches and brakes, eddy
current brakes, and disc type clutches and brakes. The magnetic
particle brakes would seem to be a good solution except that the ones I
have seen that can provide enough drag have too much drag when not
energized and have too large a diameter. About 3 inches diameter by
about 3.5 inches long is the space the clutch or brake must fit in. I
am considering rolling my own devices but am not sure how I would do
it. Maybe some sort of generator feeding a resistive load. By varying
the field strength the resistance to rotation would increase. Whatever
the solution is the resistance to rotation must be linear to the
current that actuates the device. That's one of the reasons I like the
magnetic particle barkes.
Thanks,
Eric

A simple DC motor will do it. Not a generator, but a motor. It must
rotate though, cannot stay long in the same position.
Would wear out the brushes.


w.
Greetings Helmut,
I posted the same message on rcm that I posted here.

Cross-posting would have been appropriate in this case.

Jon Elson suggested
using a motor too. His idea is to put a small resistance in series with
the main servo and connect the small handwheel motor in parallel with
the resistor. He's not sure it will work. Is his thinking sound? If so
then I will try it out and report back here and on rcm.

That's basically a really crappy way of doing what I suggested. Using a
current sense resistor and a current amplifier to drive your handwheel
motor is a good way of doing my suggested "echo the current" thing.

The "motor in parallel with a resistor" will tend to have a torque that's
proportional both to how hard the servo motor is pushing and to how fast
you're rotating the handwheel -- I don't think that's what you want.
Click to expand...
Greetings Tim,
I don't crosspost because if some ass decides to reply to my post with
something off topic and insulkting I don't want it to pollute other
newsgroups too. I see enough of it on rcm. Regarding the resisting
torque changing with handwheel speed you are right-I don't want the
torque to change except by the changing current draw of the main
servo. I tried to find a small amount of MR fluid so I could try
making my own brake that way but no luck so far. I did order some
ferrofluid even though the MR fluid is better. I may just end up with
a brake that uses friction disc(s). Since the brake must be adjustable
it could certainly be adjusted for wear of the friction surfaces. As I
was writing this I realized that I cannot use a motor to apply torque,
drag can only be used. This is because I don't want the handwheel
spinning when the servo gets a movement command from a CNC control. So
when the machine is being operated as a CNC machine the handwheels
won't move. I'm a little frustrated right now because I have all the
components for the machine conversion except the handwheel brakes. I
have the machine, the servos, ballscrews, servo amps, encoders, power
supplies, control, wire, VFD, contactors, switches, etc. And I have
done a conversion before.
Eric
Eric
 
On Fri, 12 Feb 2016 13:23:47 -0800, etpm wrote:

On Fri, 12 Feb 2016 14:09:23 -0600, Tim Wescott <tim@seemywebsite.com
wrote:

On Fri, 12 Feb 2016 11:24:14 -0800, etpm wrote:

On Fri, 12 Feb 2016 10:57:47 +0100, Helmut Wabnig <hwabnig@.- ---
-.dotat> wrote:

On Thu, 11 Feb 2016 11:32:50 -0800, etpm@whidbey.com wrote:

Everybody,
I'm working on a project that needs a slip clutch or brake or
something. I'm turning handwheels that need some sort of instantly
variable resistance to turning . Anywhere from 0 to 40 inch pounds. I
have been looking at magnetic particle clutches and brakes, eddy
current brakes, and disc type clutches and brakes. The magnetic
particle brakes would seem to be a good solution except that the ones
I have seen that can provide enough drag have too much drag when not
energized and have too large a diameter. About 3 inches diameter by
about 3.5 inches long is the space the clutch or brake must fit in.
I am considering rolling my own devices but am not sure how I would
do it. Maybe some sort of generator feeding a resistive load. By
varying the field strength the resistance to rotation would increase.
Whatever the solution is the resistance to rotation must be linear to
the current that actuates the device. That's one of the reasons I
like the magnetic particle barkes.
Thanks,
Eric

A simple DC motor will do it. Not a generator, but a motor. It must
rotate though, cannot stay long in the same position.
Would wear out the brushes.


w.
Greetings Helmut,
I posted the same message on rcm that I posted here.

Cross-posting would have been appropriate in this case.

Jon Elson suggested using a motor too. His idea is to put a small
resistance in series with the main servo and connect the small
handwheel motor in parallel with the resistor. He's not sure it will
work. Is his thinking sound? If so then I will try it out and report
back here and on rcm.

That's basically a really crappy way of doing what I suggested. Using a
current sense resistor and a current amplifier to drive your handwheel
motor is a good way of doing my suggested "echo the current" thing.

The "motor in parallel with a resistor" will tend to have a torque
that's proportional both to how hard the servo motor is pushing and to
how fast you're rotating the handwheel -- I don't think that's what you
want.
Greetings Tim,
I don't crosspost because if some ass decides to reply to my post with
something off topic and insulkting I don't want it to pollute other
newsgroups too. I see enough of it on rcm. Regarding the resisting
torque changing with handwheel speed you are right-I don't want the
torque to change except by the changing current draw of the main servo.
I tried to find a small amount of MR fluid so I could try making my own
brake that way but no luck so far. I did order some ferrofluid even
though the MR fluid is better. I may just end up with a brake that uses
friction disc(s). Since the brake must be adjustable it could certainly
be adjusted for wear of the friction surfaces. As I was writing this I
realized that I cannot use a motor to apply torque,
drag can only be used. This is because I don't want the handwheel
spinning when the servo gets a movement command from a CNC control. So
when the machine is being operated as a CNC machine the handwheels won't
move.
Click to expand...

Is there any indication out of the CNC machine that lets you know when
it's CNC-ing and when it's following the handwheels? If so, just use
that to turn the haptic feedback on and off.

I'm a little frustrated right now because I have all the
components for the machine conversion except the handwheel brakes. I
have the machine, the servos, ballscrews, servo amps, encoders, power
supplies, control, wire, VFD, contactors, switches, etc. And I have done
a conversion before.
Click to expand...

I know the feeling.

--
www.wescottdesign.com
 
On Fri, 12 Feb 2016 19:54:31 -0600, Tim Wescott <tim@seemywebsite.com>
wrote:

On Fri, 12 Feb 2016 13:23:47 -0800, etpm wrote:

On Fri, 12 Feb 2016 14:09:23 -0600, Tim Wescott <tim@seemywebsite.com
wrote:

On Fri, 12 Feb 2016 11:24:14 -0800, etpm wrote:

On Fri, 12 Feb 2016 10:57:47 +0100, Helmut Wabnig <hwabnig@.- ---
-.dotat> wrote:

On Thu, 11 Feb 2016 11:32:50 -0800, etpm@whidbey.com wrote:

Everybody,
I'm working on a project that needs a slip clutch or brake or
something. I'm turning handwheels that need some sort of instantly
variable resistance to turning . Anywhere from 0 to 40 inch pounds. I
have been looking at magnetic particle clutches and brakes, eddy
current brakes, and disc type clutches and brakes. The magnetic
particle brakes would seem to be a good solution except that the ones
I have seen that can provide enough drag have too much drag when not
energized and have too large a diameter. About 3 inches diameter by
about 3.5 inches long is the space the clutch or brake must fit in.
I am considering rolling my own devices but am not sure how I would
do it. Maybe some sort of generator feeding a resistive load. By
varying the field strength the resistance to rotation would increase.
Whatever the solution is the resistance to rotation must be linear to
the current that actuates the device. That's one of the reasons I
like the magnetic particle barkes.
Thanks,
Eric

A simple DC motor will do it. Not a generator, but a motor. It must
rotate though, cannot stay long in the same position.
Would wear out the brushes.


w.
Greetings Helmut,
I posted the same message on rcm that I posted here.

Cross-posting would have been appropriate in this case.

Jon Elson suggested using a motor too. His idea is to put a small
resistance in series with the main servo and connect the small
handwheel motor in parallel with the resistor. He's not sure it will
work. Is his thinking sound? If so then I will try it out and report
back here and on rcm.

That's basically a really crappy way of doing what I suggested. Using a
current sense resistor and a current amplifier to drive your handwheel
motor is a good way of doing my suggested "echo the current" thing.

The "motor in parallel with a resistor" will tend to have a torque
that's proportional both to how hard the servo motor is pushing and to
how fast you're rotating the handwheel -- I don't think that's what you
want.
Greetings Tim,
I don't crosspost because if some ass decides to reply to my post with
something off topic and insulkting I don't want it to pollute other
newsgroups too. I see enough of it on rcm. Regarding the resisting
torque changing with handwheel speed you are right-I don't want the
torque to change except by the changing current draw of the main servo.
I tried to find a small amount of MR fluid so I could try making my own
brake that way but no luck so far. I did order some ferrofluid even
though the MR fluid is better. I may just end up with a brake that uses
friction disc(s). Since the brake must be adjustable it could certainly
be adjusted for wear of the friction surfaces. As I was writing this I
realized that I cannot use a motor to apply torque,
drag can only be used. This is because I don't want the handwheel
spinning when the servo gets a movement command from a CNC control. So
when the machine is being operated as a CNC machine the handwheels won't
move.

Is there any indication out of the CNC machine that lets you know when
it's CNC-ing and when it's following the handwheels? If so, just use
that to turn the haptic feedback on and off.

I'm a little frustrated right now because I have all the
components for the machine conversion except the handwheel brakes. I
have the machine, the servos, ballscrews, servo amps, encoders, power
supplies, control, wire, VFD, contactors, switches, etc. And I have done
a conversion before.

I know the feeling.
Click to expand...
I ordered some magnetorheological fluid to make my own brakes with. It
looks like the best option. Apparently its response to current is
pretty linear which makes things easier. And it is easy to seal
against leaking. All that is needed is a ring magnet around the shaft
that comes out of the area containing the MR fluid. The fluid will
form its own seal around the shaft.
Eric
 
On Thursday, February 18, 2016 at 8:44:32 AM UTC-8, et...@whidbey.com wrote:

I ordered some magnetorheological fluid to make my own brakes with. It
looks like the best option. Apparently its response to current is
pretty linear which makes things easier. And it is easy to seal
against leaking. All that is needed is a ring magnet around the shaft...
Click to expand...

If magnetism causes the fluid to stiffen, do the ring magnets make it stiff?
How do you apply magnetic field when you want it to brake?
What happens if the shaft gets magnetized?
Getting the fluid might only solve a small part of the problem.
 
On Thu, 18 Feb 2016 14:43:01 -0800 (PST), whit3rd <whit3rd@gmail.com>
wrote:

On Thursday, February 18, 2016 at 8:44:32 AM UTC-8, et...@whidbey.com wrote:

I ordered some magnetorheological fluid to make my own brakes with. It
looks like the best option. Apparently its response to current is
pretty linear which makes things easier. And it is easy to seal
against leaking. All that is needed is a ring magnet around the shaft...

If magnetism causes the fluid to stiffen, do the ring magnets make it stiff?
How do you apply magnetic field when you want it to brake?
What happens if the shaft gets magnetized?
Getting the fluid might only solve a small part of the problem.
Click to expand...
The fluid is magnetized between two surfaces that move past each
other, such as discs or a cylinder within a cylinder. The surface area
is important. The small area where the ring magnet is provides little
area for friction. Also, the magnetic field is kept low. So the
friction is quite low and can be lower than a typical lip seal or
o-ring seal. In the area where the braking effect is wanted the
magnetic field can make the MR fluid as think as peanut butter.
Ferrofluid can also be used as the seal and I have some of it on the
way too. Ferrofluid does not form the fibrils that MR fluid does
because of the much smaller particle size, so this means that it
doesn't thicken the way MR fluid does.
Eric
 
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