Lessons learned in nonlinear systems and flexible robots through experiments on a 6 legged platform

Both NASA's Jet Propulsion Laboratory and the University of Wyoming have constructed 6 legged platforms, or hexapods. The hexapods are intended to provide precise motion and six degree-of-freedom vibration isolation. Two experiments performed on these hexapods provide lessons in nonlinear systems and flexible robots. In the area of nonlinear systems, it has been learned that multiple hard saturations can induce limit cycles, undesirably turning an active vibration isolator into a vibration generator. Thus, new analysis tools for multiple hard nonlinearities in multidimensional systems are needed to explain and avoid these limit cycles. In the area of flexible robots, it has been learned that model-based decoupling approaches may not work in practice despite a reasonably good match between modeled and measured dynamics. Consequently, analytical methods of predicting the level of decoupling which will actually be achieved in practice are needed.