High-pass filtered positive feedback for decentralized control of cooperation

Abstract

In a multilegged walking system, the legs, when in stance mode, have to cooperate to propel and support the body and, at the same time, to avoid unwanted forces across the body. As a simple method to control the joint movement, we propose to use local high-pass fdtered positive feedback. This does not only make redundant the determination of equations for coordinate transformation, but is also robust against all kinds of geometrical changes within the mechanical system as, for example, changes in leg segment length, bending of segments, changes in orientation of the rotational axes (by accident or because the suspension is soft by design), or addition of further joints. This simplification is possible because, instead of applying abstract, explicit computation, the physical properties of the world are exploited. It permits extreme decentralization, namely control on the joint level, and therefore allows very fast computation. In order to provide height control of the body, one leg joint is subjected to a negative feedback controller.