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Project Help and Ideas » force feedback

March 20, 2011
by d3adl0ck3
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Hello all! I have this idea for a workout machine and to make it work I need to be able to provide resistance to movement and ideally opposing force to simulate lifting heavy objects on the scale of 'human' strength. All I've really got is vague right brained ideas. I've considered something like mountain bike disc brakes for the resistance / lockout. Don't really have any good ideas for force feedback though. Has anyone tried anything like this? I'd be looking for forces around to 60 to 80 lb range preferably linear across the range from 0. Also ideally it should be reversible. I'll also need lots of them of various sizes. I realize this is probably very vague but I'm looking for broad ideas here so I hope someone has some interesting thoughts. Thanks!

March 20, 2011
by Ralphxyz
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I was working on tying my BowFlex to the Nerdkit, you can search the forum for Strain Gage to get some ideas on measuring Force/Feedback. What kind of apparatus are you picturing?

Ralph

March 21, 2011
by d3adl0ck3
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Hey Ralph, that sounds like a cool / similar idea. I am experimenting with the idea of simulating interaction in a virtual 3d environment and want to be able to a.) stop the user from moving through virtual objects and b.) I would love to be able to apply force as well such as holding up a weight. On this note I already have a large number of potentiometers multiplexed together and can measure a large number of angular positions quite accurately. I haven't looked into strain gauges enough to have put together a prototype yet but I'll definitely need those as well. Where I am getting stuck is the braking and actuation. For braking / actuating I am not sure if I should use dedicated brakes like disc brakes or use the actuators as brakes as well. One thought I had was to use a gearhead motor with a wormgear to get linear motion and put it on a strain gauge so I could move it in the appropriate direction to maintain the desired tension based on position. This is the approach that I've been leaning towards but I keep hoping there is a better way. Has anyone played with linear motion with this amount of force? Any ideas on appropriate motors/gears?

March 21, 2011
by Ralphxyz
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For Resistance (and weight for that matter) you could use a piston and vary the resistance using PWM cycling a solenoid valve.

Once you know what weight (resistance) is at what PWM cycle it would be pretty easy to write up a program to show your work out in time and weight. If the Nerdkit was controlling the resistance rather than trying to measure the resistance I believe it would be easier to implement.

This is interesting.

Ralph

March 21, 2011
by d3adl0ck3
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Hmm, that does sound very interesting. I am not sure I have the requisite knowledge to track down appropriate parts to start prototyping but I will try to look into it. If you (or anyone else of course) has some inkling of where to look I am of course interested.

March 21, 2011
by d3adl0ck3
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This would be awesome h2o2 pump

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