A controller (11) and a system for controlling the flow of fluid to a fluid pressure operated device (C) are disclosed. The controller is of the type including a rotatable spool valve (35) and a relatively rotatable sleeve valve (37). Relative rotation between the spool and sleeve define a main fluid path (MFP) and relative axial movement therebetween defines an auxiliary fluid path (AFP). An actuator (65) generates a mechanical output (71) in response to an electrical input signal (CS) to move the sleeve (37) between its neutral axial position (FIG. 6) and an axial operating position (FIG. 7). Axial movement of the sleeve is controlled by a joystick (J). The system includes various sensors (S,PS,G,P), which can sense a predetermined condition and generate an interrupt signal to interrupt or change the gain of the electrical input signal (CS).

A system for combined automatic and manual control of the motion of a vehicle comprises at least one manual control device and automatic equipment with at least one executing device. The executing device is coupled to the manual control device in such a way that a counterforce is generated in the manual control device to the force supplied by the driver. This counterforce is a function of the deviation, produced by the driver, from the intention of the automatic equipment. The automatic equipment is such that, over the whole control range, this counterforce is less than the force that the driver is able to apply on the manual control.

The manual force transmitted by a hand steering wheel to a fluid power steering mechanism is opposed by a reaction pressure that varies with the manual force at a proportionality factor of the operating pressure in the steering servomotor. The proportionality factor determining the reaction pressure is changeable under control of a reaction adjusting device.

A vehicle steering system has a desired-value generator arrangement which is actuated by a manual steering device. The desired-value generator arrangement is connected with a hydraulic actuating unit for the steered vehicle wheels by a regulating system. A modified PD control, along with taking a control segment into account, provides a precise operation of the actuating unit analogously to the operation of the manual steering device.

A servosteering control valve is provided with fluid reaction chambers which are pressued responsive to the speed of a vehicle for effecting a simulated steering resistance wherein at low speed, as in parking, there is no steering resistance and resistance increases with speed via feedback from the chambers of a double acting servomotor. The novel feature of the arrangement herein utilizes a coaction between the inlet flow control passage and return flow control passage of a steering control spool or piston valve, one such valve for each chamber. This is in conjunction with throttle passages disposed between the manually shiftable piston valves and a valve housing. Such passages are created by portions of the shiftable valves having elements slightly smaller in diameter than the diameter of the housing bore or bores in which the valves are shiftable. A single bore is used where the valves are coaxially integral and respective bores are used where the valves are separably movable. The arrangement places the throttle passages in flow series between the servomotor chambers and the reaction chambers. The effect of the throttle passages and their relationship with the inlet and return flow control passages results in pressure control of the reaction chambers such that at low speeds the simulated steering resistance is low or non-existent, as in parking, but varying to higher resistance at higher speeds.