Joined Plant and Control Design for Continuous Variable Transmission Systems

This paper presents an integrated plant and control design framework (co-design) where both factors are simultaneously optimized. The study is based on a continuously variable transmission (CVT), which is a nonlinear system that requires a combined plant and control design optimization framework to achieve the maximal performance. In automotive applications, smaller CVT and mass as well as lower energy consumption are desired. Typically, for systems with nonlinear dynamics, nested co-design framework with open-loop control strategies are utilized. Here, a simultaneous integrated plant and control design with a closed loop control strategy is formulated for the framework of co-design. To analyze the benefits of simultaneous co-design, the results of the proposed co-design strategy are compared to that of a traditional sequential design method. It was found that using the proposed framework, up to 12.7% reduction in CVT variator mass and 7.5% in pulley leakage losses can be achieved without compromising performance.