Trajectory tracking disturbance rejection controller for a state constrained biped robot

The aim of this study was to design and evaluate an output based adaptive rejection controller (ADRC) for a biped robot. The controller considers the application of an extended state observer which serves for either estimate the velocity of the legs articulation angles as well as to estimate the disturbances affecting the robot dynamics. The observer design considered the angles constrains which naturally appear in the movement of a biped robot. A class of hybrid observer appeared as solution for the estimation of angles values and their positions. The control design (proposed in a distributed structure) used the constrained estimation of velocity to solve the tracking trajectory problem associated to the gait cycle of the biped robot. A set of numerical evaluations over a simulated biped robotic system proved that active disturbance rejection controller using the estimated state constrains tracked the reference angles of articulation. The comparison of the controller proposed in this study overcame the tracking results attained by the classical ADRC where the estimated velocities were freely estimated without taking into account the angles constrains.