The design of low cost valve-and-pump compounded pressure control system for the hydro viscous clutch

Hydro viscous clutch (HVC) is a power transmission unit which relies on shear stress of fluid to transmit driving torque. The conventional pressure control system suffers from high minimum operating pressure problem. This makes the HVC has a large drag torque and greatly limits the usage flexibility. In this article, a valve-and-pump compounded pressure control (VCPC) system is proposed for the hydro viscous clutch (HVC) to enlarge the working pressure range in the low pressure direction. The pressure of the control cylinder is adjusted by the rotary speed of pump or the electro-proportional relief valve (ERV) when the VCPC system works on different pressure stage. The adaptive robust control (ARC) algorithm and the feedforward PID algorithm are introduced into the VCPC system for the purpose of obtaining better pressure tracking performance. The effectiveness of the proposed VCPC system is validated through the compared experiments. Electromagnetic interference is considered and experiment results are carefully analyzed. It can be concluded that the pressure control range is increased by 38% with the proposed VCPC system. And compared with conventional control algorithms, the ARC algorithm has a better pressure tracking performance and relatively smooth input signal on low pressure stage.