Fuzzy controllers in hydrostatic transmission

A modern hydrostatic transmission consists of three main components, a diesel engine, a variable displacement hydraulic pump and a variable displacement hydraulic motor. The output speed of the hydrostatic transmission is controlled by governing the rotational speed of the diesel engine and controlling displacements of the hydraulic units. Traditionally a PID-controller has been applied in speed control system. This causes a problem because there is variation of dynamic properties of the speed control system while vehicle speed is changed. In this paper, two fuzzy logic based controllers are introduced and compared with the discrete PI-controller.