A steering system and method are described for a vehicle having steerable wheels. A steering device may be coupled to one or more of the wheels. A parked state of the vehicle and a present orientation of the hydraulic steering device may be determined. The present orientation of the steering device may be compared with a neutral orientation of the steering device. Based upon a determined parked state of the vehicle and the comparing of the present and neutral orientations of the steering device, the steering device may be moved from the present orientation toward the neutral orientation.

An articulated work vehicle with linked front and rear frames includes a joystick lever, a force imparting component, and a controller. The joystick lever can be moved to an inside or an outside with respect to an operator's seat by being operated by an operator, to change a steering angle of the front frame with respect to the rear frame. The force imparting component is configured to impart an assist force or a counterforce to an operation of the joystick lever by the operator. The controller controls the force imparting component so that an operating force required to move the joystick lever to the outside is different from an operating force required to move the joystick lever to the inside.

An articulated work vehicle with linked front and rear frames includes a joystick lever, a hydraulic actuator, a control valve, a force imparting component, a joystick displacement sensor, a steering angle sensor, and a controller. The joystick lever is operated to allow a target steering angle to be set. The hydraulic actuator is driven hydraulically to change an actual steering angle. The control valve controls flow of fluid supplied to the hydraulic actuator to eliminate deviation between the target and actual steering angles. The force imparting component imparts an assist force or a counterforce to the operation of the joystick lever. The controller controls the force imparting component so that a counterforce is imparted to the operation of the joystick lever when the joystick lever has been operated in an opposite direction from a rotation direction of the front frame based on detections of the sensors.

A method includes receiving a handwheel angle signal, generating a handwheel speed signal and a handwheel acceleration signal, and synchronizing the handwheel speed signal and the handwheel acceleration signal. The method also includes delaying the handwheel angle signal, calculating a sum of the delayed handwheel angle signal and a phase value, converting the sum of the delayed handwheel angle signal and the phase value to radians, determining an offset correction value by calculating a sine function value of the converted sum of the operator torque estimation signal and the phase value, calculating a product of the offset correction value and a calibratable value of an offset mass magnitude, adjusting the operator torque estimation signal by adding the product and the calibratable value of an offset mass magnitude, and determining whether hands of an operator of the vehicle are on the handwheel based on the adjusted operator torque estimation signal.

A hydraulic system comprising: a hydraulic fluid pressure source, a hydraulic fluid reservoir, a hydraulically driven actuator having a first chamber and a second chamber, and a valve assembly having a first pilot-operated directional control valve and a second pilot-operated directional control valve, each including: an inlet port fluidly connected for receiving high-pressure hydraulic fluid from the hydraulic fluid pressure source, an outlet port fluidly connected for draining hydraulic fluid to the hydraulic fluid reservoir, a first actuator port fluidly coupled with the first chamber of the hydraulically driven actuator, a second actuator port fluidly coupled with the second chamber of the hydraulically driven actuator; first to fourth fail-safe solenoid-controlled pilot valves; and a pilot pressure fluid supply system.

In an example embodiment, a vehicle control system includes a memory including computer-readable instructions stored therein and a processor. The processor configured to execute the computer-readable instructions to receive information corresponding to, a yaw rate of a vehicle, a lateral position of the vehicle and a heading angle of the vehicle, determine a stability indicator indicating an estimate of a stability of the vehicle based on the received information, and adjust one or more gains of a steering system of the vehicle based on the determined stability indicator.

A pilot pressure control system for controlling a pilot signal pressure at a pilot inlet of a control valve includes a pilot outlet adapted to be connected to the pilot inlet. The pilot pressure control assembly further includes a first pilot valve assembly and a second pilot valve assembly. Each one of the first and second pilot valve assemblies are individually controllable so as to selectively provide a first fluid flow direction from a pressure line to the pilot outlet and a second fluid flow direction from the pilot outlet to a drain line. At least the first pilot valve assembly is adapted to assume a maximum pressure supply condition so as to supply a first pilot valve assembly maximum pressure to the pilot outlet. At least the second pilot valve assembly is adapted to provide a pressure drop from the pilot outlet to the drain line via the second pilot valve assembly. The pilot pressure control system is configured such that, when the pilot pressure control system is connected to the pressure and drain lines and when the first pilot valve assembly is controlled so as to assume the maximum pressure supply condition and the second pilot valve assembly provides a fluid flow in the second fluid direction with a minimum pressure drop, the pressure at the pilot outlet is equal to or above 20 of the first pilot valve assembly maximum pressure (Pmax).

An articulated work vehicle with linked front and rear frames includes a joystick lever, a force imparting component, a speed sensor, and a controller. The joystick lever is configured to change a steering angle of the front frame with respect to the rear frame by operation by an operator. The force imparting component is configured to impart an assist force or a counterforce to operation of the joystick lever by the operator. The speed sensor is configured to sense speed of the work vehicle. The controller is configured to control the force imparting component so as to impart the assist force or the counterforce according to the speed sensed by the speed sensor.

A vehicle guidance system comprises a hydraulic steering cylinder for controlling a steering angle of a steerable wheel of a vehicle. A hydraulic steering valve is adapted to control a flow of hydraulic fluid to the hydraulic steering cylinder. A stepper motor is adapted to move or modulate a shaft coupled to the hydraulic steering valve in accordance with a control signal or control data message from a vehicle guidance controller. A position encoder of the stepper motor can measure the movement of the shaft. A steering angle estimator can estimate the steering angle based on measurements of the position encoder. A location-determining receiver provides position data and heading data. A vehicle guidance controller provides the control signal or control data message based on the estimated steering angle, position data and heading data.

A vehicle guidance system comprises a hydraulic steering cylinder for controlling a steering angle of a steerable wheel of a vehicle. A hydraulic steering valve is adapted to control a flow of hydraulic fluid to the hydraulic steering cylinder. A stepper motor is adapted to move or modulate a shaft coupled to the hydraulic steering valve in accordance with a control signal or control data message from a vehicle guidance controller. A position encoder of the stepper motor can measure the movement of the shaft. A steering angle estimator can estimate the steering angle based on measurements of the position encoder. A location-determining receiver provides position data and heading data. A vehicle guidance controller provides the control signal or control data message based on the estimated steering angle, position data and heading data.