Towards fast and adaptive optimal control policies for robots: A direct policy search approach

Optimal control methods are generally too expensive to be applied on-line and in real-time to the control of robots. An alternative method consists in tuning a parametrized reactive controller so that it converges to optimal behavior. In this paper we present such a method based on the “direct Policy Search” paradigm to get a cost-efficient control policy for a simulated two degrees-of-freedom planar arm actuated by six muscles. We learn a parametric controller from demonstration using a few near-optimal trajectories. Then we tune the parameters of this controller using two versions of a Cross-Entropy Policy Search method that we compare. Finally, we show that the resulting controller is 20000 times faster than an optimal control method producing the same trajectories.