Abstract: A control system 54 for a doser type hydraulic actuator 56 is disclosed. The doser actuator includes a pair of unequal area pistons 18, 20 on a common shaft 16 which are moved incrementally by injecting into or removing from a control pressure chamber metered quantities or doses of fluid. The doses are metered by timed openings of solenoid valves 32, 34 connecting the control pressure chambered to a supply 44 or return 48 pressure sources. The control system includes a base pulse width signal generator 106 which pulse modulates the solenoids as a function of the error between a requested position and an actual position. The base pulse width is modified by a correction means 108, 110, 112 when the error is within a predetermined band width. The correcting means compensates for the variations of the actuator when its response is uncertain with respect to the base pulse width.