Abstract: The invention relates to a by-wire brake system. There is a need for a trailer brake control circuit for a by-wire brake system. A brake control circuit for trailer brakes in a by-wire brake system includes a hydraulic pump or a supply of pressurized air, a hydraulic reservoir or an air vent, a pair of solenoid operated proportional valves for controlling communication between the pump, the reservoir and the trailer brakes, and a pair of solenoid operated shutoff valves, each controlling communication between the trailer brakes and a corresponding one of the proportional valves.

Abstract: A hydraulic circuit is provided for a by-wire brake system. There is a need for such a circuit which permits independent left and right brake operation and which has redundancy. The circuit includes left and right brake control valves, a left brake line communicated with a left brake, a right brake line communicated with a right brake, and a left-right cross-over valve operable to open and close communication between the left and right brake lines. The hydraulic circuit also includes a left shutoff valve between an outlet of the left brake valve and the left brake line, and a right shutoff valve between an outlet of the right brake valve and the right brake line.

Abstract: The invention relates to a hydraulic circuit for a steer-by-wire steering system which includes a hydraulic pump, a reservoir, a bi-directional steering actuator, a pair of electronic control units (ECU) for generating electrical steering control signals in response to an operator-generated steering command. There is a need for such a circuit which des not require large expensive valves. The hydraulic circuit includes a pair of solenoid operated directional control valve units and a pair of solenoid operated shut-off valves. Each directional control valve unit and a corresponding one of the shut-off valves are connected in series between the pump, the reservoir and the steering actuator, and are connected to a respective one of the ECUs and controlled thereby. In the absence of a fault condition both shut-off valves are open so that hydraulic flow to and from the actuator is shared by both the first and second directional control valve units.