Multimedia  

 

Volume 23 Issue 7/8- Publication Date: 1 July-August 2004
 
Feedback Control Methods for Distributed Manipulation Systems that Involve Mechanical Contacts
 
T.D. Murphey and J.W. Burdick Division of Engineering and Applied Science, California Institute of Technology, Pasadena, CA, USA
 

In this paper we introduce feedback control methods for distributed manipulation systems thatmove objects via rolling and slipping point contacts. Because of the intermittent nature of these mechanical contacts, the governing mechanics of these systems are inherently nonsmooth. We first present a methodology to model these non-smooth mechanical effects in a manner that is tractable for non-smooth control analysis. Using these models, we show that when considerations of these non-smooth effects are taken into account, a class of traditional open-loop distributed manipulation control methods cannot stabilize objects near an equilibrium. However, stability can be achieved through the use of feedback, and we present non-smooth feedback laws with guaranteed stability properties. We then describe an experimental modular distributed manipulation test-bed upon which one can implement a variety of control schemes. Experiments with this test-bed confirm the validity of our control algorithms. Multimedia extensions include videos of these experiments.

 
Multimedia Key
= Video = Data = Code = Image
 
Extension
Type
Description
1
Example One: This is a video of an experimental implementation of an open-loop elliptic velocity field. Recall that the object being manipulated is a clear piece of plexiglass with a white and black piece of paper on top for feedback. As predicted, the x and y coordinates are successfully stabilized and the ? dynamics are not stabilized. (5.8MB)
2
Example Two: This is a video of an experimental implementation of the underactuated system. Notice that despite the underactuation, the plexiglass is stabilized to the origin at the desired orientation. (17.1MB)
3
Example Three: This is a video of an experimental implementation of the fully actuated system. Here the advantage of full actuation is clear. The trajectory to the desired equilibrium is quite smooth and the wheels are all coordinated without any slipping. (9.8MB)
4
Example Four: This is a video of an experimental implementation of the globally stabilizing controller that combines the open-loop techniques with the closed-loop techniques. Outside the circle shown in the video, the system is running open loop. However, as soon as the center of mass of the plexiglass enters the circle, the closed-loop control is turned on and the plexiglass is stabilized to the origin at the correct orientation using the full actuation control laws. (9.1MB)
 
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