Controllability analysis of biped walking robots

The focus of this paper is 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 in two phases: (i) a single support phase, in which it is studied the trajectory controllability based on simple motion goals and (ii) an exchange of support phase, in which the forward leg should absorb the impact and then gradually accept the robot´s weight. The contact of the foot with the constrained surface is modelled through linear spring-damper systems both in the vertical and horizontal directions. 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.