Methods and apparatus to reduce noise and vibration in a hybrid hydraulic power steering system are disclosed. A method includes receiving sensor data from sensors of a vehicle and mapping the sensor data to filter coefficients. The method further includes generating a torque demand based on an input of the filter coefficients into a polynomial filter and tuning at least one of a torque assistance or a steering damping of an assisted steering system of the vehicle based on the torque demand.

The present disclosure relates to a load-sense system such as a load-sense steering system that operates in a static load-sense mode for low flows and operates in a dynamic load-sense mode for high flows.

A method (300) and control arrangement (210) for controlling a vehicle (100) to freewheel with engine off. The vehicle (100) has an engine (260) for propelling the vehicle (100) and a hydraulic power steering system (400). The hydraulic power steering system (400) comprises a primary power steering pump (270a) arranged to be driven by the engine (260) and a secondary power steering pump (270b). The method (300) includes: determining (301) when to start freewheeling the vehicle (100) with its engine off; and prior to starting the freewheeling of the vehicle (100) with engine off, determining (302) to start the secondary power steering pump (270b).

A hydraulic system for controlling a pair of steerable caster wheels includes a left side actuator and a right side actuator. A rear steering control valve is moveable between a first state for disabling direct control of the left and side actuators and a second state for enabling direct control the left and right side actuators to provide a steer response. A fluid connection continuously connects the pressure source and the fluidic tie rod fluid circuit in fluid communication when the rear steering control valve is disposed in one of the first state and the second state to continuously supply the pressurized fluid to the fluidic tie rod fluid circuit.

A secondary steering pump system may include a secondary steering pump, a bypass valve having a first bypass position configured for placing the secondary steering pump in fluid communication with a hydraulic tank and a second use/testing position configured for placing the secondary steering pump in fluid communication with a steering control circuit. The system may also include a solenoid valve configured for actuation by a solenoid and for selectively actuating the bypass valve from the first position to the second position. The system may also include a pressure sensor configured for sensing pressure in the system.

A secondary steering pump system may include a secondary steering pump, a bypass valve having a first bypass position configured for placing the secondary steering pump in fluid communication with a hydraulic tank and a second use/testing position configured for placing the secondary steering pump in fluid communication with a steering control circuit. The system may also include a solenoid valve configured for actuation by a solenoid and for selectively actuating the bypass valve from the first position to the second position. The system may also include a pressure sensor configured for sensing pressure in the system.

A turning system is configured to move a turning shaft to turn a left wheel and a right wheel of a vehicle. The turning shaft is configured to couple the left wheel and the right wheel to each other. A torsion bar is engaged with the turning shaft via a steering gear box. The turning system includes: a turning mechanism including (i) an electric turning mechanism including an electric motor configured to rotate a portion of the torsion bar which is located upstream of the steering gear box and (ii) a hydraulic turning mechanism configured to apply a moving force to the turning shaft in an axial direction, the moving force being produced by a hydraulic pressure; and an electric-motor controller configured to control the electric motor based on a frictional force in the turning mechanism and a road-surface reaction force that acts between (a) a tire on the left wheel and a tire on the right wheel and (b) a road surface.

A steering system for a trailing axle of a motor vehicle includes an electric motor, a hydraulic pump, a first valve, and a working cylinder. The electric motor is configured to drive the hydraulic pump. The working cylinder has a central bore and a piston positioned in the working cylinder. The first valve is fluidically connected to the pump such that the first valve is configured to block flow between the central bore and the pump in response to pressure generated by the pump, and to release the flow in response to a non-pressurized state of the pump in order to divert hydraulic fluid from the working cylinder through the central bore via an adhesion-driven movement of the piston into a central position in the central bore. A method includes operating a steering system for a trailing axle of a motor vehicle of this type.

Power steering device has steering mechanism 2, power cylinder 29 having a pair of hydraulic chambers 29a, 29b divided by piston 31 and providing steering force to steering mechanism, torque sensor 11 detecting steering torque Tr of steering mechanism, rotary valve 30 selectively supplying working fluid supplied from pump 9 to the pair of hydraulic chambers according to relative rotation between input and output shafts, hollow shaft motor 10 providing steering force to input shaft, control unit 13 in which microcomputer is mounted, and torque command signal operating section 61 provided in control unit and configured to calculate torque command signal Tm* for driving and controlling electric motor 10 on the basis of the steering torque Tr and vehicle speed Vs and when vehicle speed is a predetermined vehicle speed or greater, set torque command signal to 0. With this, physical size of power steering device can be decreased.

Power steering device has steering mechanism 2, power cylinder 29 having a pair of hydraulic chambers 29a, 29b divided by piston 31 and providing steering force to steering mechanism, torque sensor 11 detecting steering torque Tr of steering mechanism, rotary valve 30 selectively supplying working fluid supplied from pump 9 to the pair of hydraulic chambers according to relative rotation between input and output shafts, hollow shaft motor 10 providing steering force to input shaft, control unit 13 in which microcomputer is mounted, and torque command signal operating section 61 provided in control unit and configured to calculate torque command signal Tm* for driving and controlling electric motor 10 on the basis of the steering torque Tr and vehicle speed Vs and when vehicle speed is a predetermined vehicle speed or greater, set torque command signal to 0. With this, physical size of power steering device can be decreased.