A solution to control the dynamic behaviour of a pneumatic quadruped robot

Abstract

Describes a control/command architecture developed for the authors' quadruped robot RALPHY (French acronym for legged robot with pneumatic actuators). Dynamical and real time aspects as well as theoretical and practical approaches have been taken into account. In order to hierarchize and distribute as far as possible the different tasks to be realized, the robot dynamic model has been decomposed in two parts. A "coordinator level" controls the platform stability by means of leg to platform interaction model. In a dynamic situation, this stability is ensured by a "center of mass acceleration control" and a "force distribution control". A "leg level" deals with the control problem of each leg. The authors propose an adaptive computed torque type controller which takes into account nonlinearities due both to the dynamic model and to the pneumatic system. Finally, the authors develop the connection between these two levels, proposing a solution to deal with uneven terrains.