Optimization of the locomotion of a legged vehicle with respect to maneuverability (robot, walking, hexapod, stability)

Abstract

A legged vehicle possesses a tremendous potential for maneuverability over rough terrain, particularly in comparison to conventional wheeled or tracked vehicles. In general, a legged vehicle can offer more degrees of freedom for movement than conventional vehicles. However, the coordination of the movements of the various leg joints in such a way as to produce the desired locomotion of the vehicle is an extremely complex task. The work documented in this dissertation is aimed at improving the maneuverability of a legged vehicle and reducing the operator's burden of manipulating the body and limbs. A major contribution of this research has been the development of the Dual Tripod Leg Placement Algorithm. This represents the first hardware implementation of supervisory control for an omnidirectional walking algorithm capable of rough terrain locomotion. In this algorithm, leg motion is limited only by geometrical considerations; there are no time sequencing constraints as in the typical wave gait formulations. The result is an extremely agile walking algorithm. Previous work on legged vehicle control generally assumes that the terrain is level, so that minimal operator interaction is necessary. However, for very irregular terrain the operator may require a guidance mode that gives maximum resolution and flexibility in controlling the position and orientation of the vehicle body and legs. In this dissertation, several Precision Footing Algorithms have been developed in order to aid the operator in this important task. Another major contribution of this research has been the development of the concept of Energy Stability Margin. This improved stability criterion provides an accurate quantitative measure of vehicle stability which can be automatically optimized. This measure, together with a consideration of constraints on the kinematic limits of individual legs, leads to the development of several schemes for Automatic Body Regulation. These Automatic Body Regulation schemes are incorporated into the vehicle control algorithm to provide a high degree of vehicle maneuverability while reducing the operator's burden. These improvements now make it practical to consider the application of a legged vehicle for locomotion on rough terrain for a realistic length of time.