Minimax differential dynamic programming: application to a biped walking robot

We have developed a robust control policy design method for high-dimensional state spaces by using differential dynamic programming with a minimax criterion. As an example, we applied our method to a simulated five link biped robot. The results show lower joint torques using the optimal control policy compared to torques generated by a hand-tuned PD servo controller. Results also show that the simulated biped robot can successfully walk with unknown disturbances that cause controllers generated by standard differential dynamic programming and the hand-tuned PD servo to fail. Learning to compensate for modeling error and previously unknown disturbances in conjunction with robust control design is also demonstrated. We applied the proposed method to a real biped robot to optimize swing leg trajectories.