Hybridization of model-based approach with reinforcement fuzzy system design

Reinforcement learning (RL) is a popular learning paradigm to adaptive learning control of nonlinear systems, and is able to work without an explicit model. However, learning from scratch, i.e., without any a priori knowledge, is a daunting undertaking, which results in long training time and instability of learning process with large continuous state space. For physical systems, one must consider that the design of controller is very rarely a tabula rasa: some approximate mathematical model of the system is always available. In this paper, our focus is on control applications wherein the system to be controlled is a physical system. We can always obtain at least an approximate mathematical model of the plant to be controlled. We propose a method for hybridization of model-based approach with RL, which is the right solution for such control problems. The superiority of proposed hybrid approach has been established through simulation experiments on a cart-pole balance bench mark problem, comparing it with model-free RL system. We have used fuzzy inference system for function approximation; it can deal with continuous action space in Q-learning. Comparison with other function approximators has shown its superiority in terms of robustness of the controller to parameter variations in the plant.