A position tracking control system is implemented by utilizing parallel-connected on/off valve series. The pulse code modulation method is used to achieve stepwise flow control and four valve series, each having four two-way sole-noid valves, are used. A cost function based controller is used to control simultaneously and independently flow paths from supply to cylinder chambers and from chambers to tank. It is shown that controllability can be improved especially at low velocities by allowing three or four valve series to be open simultaneously instead of using classical inflow out-flow control

Keywords: Pulse code modulation, on/off control, tracking control