AnsweredAssumed Answered

Trouble designing and animating a robotic device

Question asked by David Cowens on Jun 26, 2012
Latest reply on Jun 27, 2012 by Keith Parker

Hello All,


We are designing a 6 DOF Stewart Platform and having a load of troubles with it. We have our entire idea sketched out and it is also actually about half built already. The problem we are having is in assembling and animating the robot.  This device uses 6 identical legs, so it would be nice if we could assemble 1 leg, then import that assembly as 6 sub-assemblies.  When we do this, the final assembly file refuses to move the parts into their proper positions.


Each leg looks like this which is the LM2070-01 attached to a metal plate. We used the linear motor CAD file from that site as well as premade CAD files from McMaster-Carr for the spherical joints and made our own metal plate. We then tried to import the sub-assembly into an assembly to attach them to two other plates similar to what is seen at the wiki page. We were able to attach the first two motors to both the top plate and the bottom plate perfectly fine.  We then tried to add a third but it would fail as soon as we got the last mate in. We have no explanation for this. We fought with it for several days before giving up the sub-assembly approach and remaking all 6 legs as well as all of their individual mates in a single assembly. This is what it looks like, except that it has a device hanging beneath the top plate, which was hidden so the platform could be seen better. We were wondering if there is a specific step we might have missed but I don't know how to demonstrate our exact process or what you all can do to help us with it.


Our next problem comes with animation. Since it is supposed to have six degrees of freedom, we want to demonstrate this capablility in an animation that looks like this, which I am describing as a cone with the base of the cone being the bottom plate. Essentially the way we are attempting to do it is have a fixed point in the center of the top plate, then angle the top plate to a certain amount along either the X or Y axis, then animate it rotating around the Z axis. This was the plan anyway. It won't allow us to fix the top plate at any point at all. It keeps telling us that it is over-constrained or unable to be solved.


We have been able to demonstate Z axis movement by using the linear motor function in motion study and setting it to osscilate. We then tried to offset the values by using the phase shift to make it wobble as seen in the gif above. This worked somewhat but when followed the path of the inner device, it was making a circle that was not cocentric to either plate. Is there possibly something we did wrong here? I know we can make these motions either by moving the whole device ourselves or by manually changing each linear motor value, however, we are looking to save time on this. Another way we would like to animate it is to make it look like a cone with the tip at a fixed point in the bottom plate and the device following the outside plane of the cone.


I'm sorry if this is very confusing, but I will gladly provide more detailed responses if we can get some help on this. Thanks.