Position/force control of biped walking robots

The paper addresses the problem of modelling and control of a biped robot by combining Cartesian based position and force control algorithms. The complete walking cycle is divided into two phases: i) single support, in which is studied the trajectory controllability based on simple motion goals and ii) exchange of support, in which the forward leg absorbs the impact and then gradually accepts the robot´s weight. The contact of the foot with the constrained surface is modelled through linear spring-damper systems. The system´s controllability is enhanced through the insertion of a dynamic selection matrix that modifies the actuating profile in each phase. The control algorithms are simulated and their effectiveness and robustness are discussed