Bio-Inspired Equilibrium Point Control Scheme for Quadrupedal Locomotion

The goal of this paper is to present a force control scheme for quadrupedal locomotion by adopting observations of biological motor behavior. Specifically, based on the equilibrium point (EP) hypothesis, we set up a bio-inspired EP controller in Cartesian space. The proposed EP controller modifies the EP trajectories appropriately over time from two perspectives, which can ensure stable interactions and system equilibrium. One perspective is directly compensating for the posture angle error based on torso posture compensation. The other is based on the foot force tracking algorithm and admittance model. The main contribution of this paper is to show how the EP controller realizes dynamic balance with no input about inertial parameter identification for the robot or terrain information estimation. Overall, the EP control scheme is simplified for stability problems and is easy to use in practice. Finally, we carried out a series of simulations and experiments to evaluate the effectiveness of the EP control algorithm. The results demonstrate that the proposed controller may improve dynamic stability and realize compliance performance.