A new way to tackle position/force control for pneumatic robots

We propose a controller called “joint impedance controller” designed to deal with force and motion trackings. The objective is to control the motion of a biped robot leg during setting and raising phases. As equilibrium of these structures is crucial, transitions between the two phases has to be as soften as possible. Moreover, control laws have not to be too complex and have to take into account pneumatic actuator effects. For these purposes, we purpose a continuous joint impedance controller. The control design is based on a computed torque between the torque actuator and mechanical models. The relation between the torque due to the force applied on the ground and the corresponding position error for each joint is assumed to be of the second order and linear. The asymptotic stability is ensured using Popov criteria. Simulation results of this new controller are presented, leading to a good behaviour of the leg during the two phases at relatively high velocities