Generic dynamic motion generation with multiple unilateral constraints

Abstract

Control methods based on a hierarchy of tasks provide a fast, easily-modifiable, and accurate way of generating a motion. In this paper, we propose to extend this hierarchical approach by using a cascade of quadratic programs to handle simultaneously the robot dynamics, inequality and equality constraints, and multiple non-coplanar unilateral contacts. First, we detail the proposed generic inverse-dynamics solver. Then, we prove that the model used to handle contacts encompasses the classical zero-moment-point balance condition. Finally, as an example of the capabilities of the method, we generate a complex motion where the humanoid robot HRP2 sits down on an armchair, using the armrests as additional contacts, while ensuring joint position and velocity limits.