A Model-Based Control Approach for Locomotion Control of Legged Robots

In this project, a new method is proposed for controlling legged robots. This method takes dynamics of the robot into account to have better nominal tracking of desired trajectories and more compliant environmental interactions at the same time. We have incorporated also natural dynamics of the robot into the system by using off-line calculated gaits extracted from optimizations on energy. So the main control loop in this method consists of a feed-forward block that generates actuator torques given desired trajectories and also a feedback block designed and tuned specifically for the structure of the robot. A trajectory planner uses known optimal trajectories together with some control laws that modify these trajectories to have better robustness in different situations. We successfully tested this method on two robots. The first one was a monopod robot with two actuators and five degrees of freedom. On this robot, we integrated a high level controller that made the robot capable of performing locomotion on sloped terrains up to ±20◦ and rough terrains up to variance of 0.03 in terrain surface. On second robot which was a 2D quadruped robot using bounding gait, we ended up with stabilization of feed-forward, feedback and trajectory planner. This robot showed more robustness to the roughness of the terrain. The proposed control method could be a good candidate for control problems concerning compliance environmental interactions and energy optimality.