Biped Robot Position Control with Stability-Based Ground Reaction Force and Velocity Constraints

摘要

This paper proposes a method to automatically limit referential joint torques of a biped robot to prevent the feet from losing contact with the ground. This method can be used to implement active balancing, which is equivelent to position control as long as the torque limits are not exceeded. Therefore, unlike the zero-moment point feedback methods, the proposed method is robust against disturbances and has a good trajectory following ability without having the usual dangers associated with stiff, position-controlled methods. Furthermore, this method is based on force sensor data, and thus unlike inverse dynamic methods, it is robust to variations in robot dynamics that can arise when the robot carries loads. This paper also proposes a method to limit referential joint velocities to prevent overshoot of the robot. This is useful when the robots center of mass (COM) position moves near the edge of the support polygon, because if the COM exits the support polygon due to overshoot, then it will not be able to return to it. These two proposals are then combined to form a position control system that is robust against overshoot and can strongly interact with the environment without losing contact of the feet with the ground. Finally, this position control system is implemented on the biped robot MARI-3, and it is shown that near-zero overshoot position control with compliance is achieved.