Optimization of graded arrays of resonators for energy harvesting in sensors as a Markov decision process solved via reinforcement learning

The design optimization of the grading of a resonator array for energy harvesting in sensors is described. Attention is paid to set the resonator heights, possibly removing resonators whenever convenient. Instead of employing time-consuming heuristic approaches that require verifying the physical understanding of the problem and tuning the design ruling parameters, the optimization task is treated as a Markov decision process, in which states describe specific system configurations, and actions represent the modifications to the current design. The physics-based understanding of the problem is exploited to constrain the set of possible modifications to the mechanical system. Finite elements simulations are exploited to evaluate the action effects and to inform the reinforcement learning agent. The proximal policy optimization algorithm is employed to solve the Markov decision problem. The procedure is demonstrated to be able to automatically produce configurations, enhancing the mechanical system performance. The proposed framework is generalizable to a large class of problems involving the design optimization of sensors.