MPC-Net: A First Principles Guided Policy Search
This work addresses control challenges for robotics, particularly in multimodal systems like quadrupedal robots, but it is incremental as it builds on existing policy search methods with a novel loss function.
The paper tackles the problem of controlling dynamical systems with known models by introducing an imitation learning approach that uses a loss function based on the control Hamiltonian to directly solve optimality conditions. The result is a policy that successfully stabilizes different gaits on a real quadrupedal robot using less than 10 minutes of demonstration data.
We present an Imitation Learning approach for the control of dynamical systems with a known model. Our policy search method is guided by solutions from MPC. Typical policy search methods of this kind minimize a distance metric between the guiding demonstrations and the learned policy. Our loss function, however, corresponds to the minimization of the control Hamiltonian, which derives from the principle of optimality. Therefore, our algorithm directly attempts to solve the optimality conditions with a parameterized class of control laws. Additionally, the proposed loss function explicitly encodes the constraints of the optimal control problem and we provide numerical evidence that its minimization achieves improved constraint satisfaction. We train a mixture-of-expert neural network architecture for controlling a quadrupedal robot and show that this policy structure is well suited for such multimodal systems. The learned policy can successfully stabilize different gaits on the real walking robot from less than 10 min of demonstration data.