| 摘要 |
A hydraulic pressure control system e.g. for vehicle brakes, includes pressure actuators 28, 30, 38, 40, solenoid operated fluid flow control valves 50 - 56, 60 - 66, a first pressure source 14, a second pressure source e.g. an accumulator 26 for traction control, and an electronic controller (86, 90, 142 figures 6 - 8) wherein the pressure at each actuator can be estimated, thereby eliminating the need for using pressure transducers to obtain a pressure signal for use in the controller, based on a calibratable relationship between estimated pressure and the difference in the volume of fluid flowing into the actuator and from the actuator. An effective duty cycle for a control valve is determined based on (i) the difference between the estimated pressure and the supply pressure and (ii) a commanded duty cycle. <IMAGE>
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