A hydraulic steering arrangement 1 is described comprising a supply port arrangement having a pressure port (4) and a tank port (5), a working port arrangement having two working ports (6, 7), a steering unit (2) arranged in a flow path (9) between the supply port arrangement (4, 5) and the working port arrangement (6, 7), and a second flow path (13) in form of an amplification flow path bridging the steering unit (2) and having an amplification orifice (A.sub.U1) which is controlled as function of the steering unit (2). Such a steering arrangement should have a possibility to change the steering behaviour. To this end at least a third flow path (14) in form of an amplification flow path is arranged in parallel to the second flow path (13), wherein the second/or the third flow path (13, 14) comprise an valve (15).

A hydraulic steering arrangement 1 is described comprising a supply port arrangement having a pressure port (4) and a tank port (5), a working port arrangement having two working ports (6, 7), a steering unit (2) arranged in a flow path (9) between the supply port arrangement (4, 5) and the working port arrangement (6, 7), and a second flow path (13) in form of an amplification flow path bridging the steering unit (2) and having an amplification orifice (A.sub.U1) which is controlled as function of the steering unit (2). Such a steering arrangement should have a possibility to change the steering behaviour. To this end at least a third flow path (14) in form of an amplification flow path is arranged in parallel to the second flow path (13), wherein the second/or the third flow path (13, 14) comprise an valve (15).

A work vehicle includes a hydraulic actuator that changes an actual steering angle, an actual steering angle detecting part, an operating unit that performs a steering operation, a position adjusting control part that controls the position adjusting part based on the actual steering angle, and a steering control part that controls the hydraulic actuator. The operating unit includes a support part, a rotating part supported rotatably by the support part, an operating part supported rotatably by the support part or the rotating part, a biasing part that biases the operating part to a predetermined position with respect to the rotating part, a position adjusting part that adjusts a rotation angle of the rotating part with respect to the support part, and a rotation angle detecting part configured to detect the rotation angle of the operating part with respect to the support part or the rotating part.

A valve for hydraulic parallel work systems is provided. The valve includes a first pair of ports, a second pair of ports, a first connection, and a second connection. The first connection is between the first pair of ports when the valve is in a load reaction-enabling state. The first connection transmits a load reaction from a load at a steering actuator to a steering device of a hydrostatic steering circuit. The second connection is between the second pair of ports when the valve is in an electro-hydraulic steering enabling state. The second connection fluidly connects a fluid source to an electro-hydraulic steering circuit.

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.

The present invention relates to a steering control system and method for a vehicle, and more particularly a control system and method for accurately controlling the lateral movement of an autonomous vehicle that has a non-linear steering system, e.g., a hydraulic steering system, which includes measuring wheel angles of the vehicle, calculating the actuation value for the desired wheel angle based on the measured wheel angle, and rotating the steering wheel according to the actuation value; wherein the actuation values are calculated based on a function f( ) representing the nonlinear behavior of the steering ratio depending on the position and movement direction of the steering wheel, and another function g( ) representing a response lag when the steering direction is changed.

A milling machine can include a frame; at least two tracks coupled to the frame for propelling the milling machine; first and second hydraulic cylinders configured to steer each of the at least two tracks, respectively; an adjustable hydraulic tie rod extending between the at least two tracks; first and second steering collars coupled to the each of the tracks to move the tracks, wherein the first hydraulic cylinder is coupled to the first steering collar and the second hydraulic cylinder is coupled to the second steering collar, and wherein the adjustable hydraulic tie rod is coupled to both of the steering collars; one or more sensors to determine the positions of the at least two tracks; and a hydraulic steering control system coupled to the first and second hydraulic cylinders and the adjustable hydraulic tie rod and configured to vary a steering mode of the at least two tracks between a parallel steering mode and an Ackerman steering mode, wherein if one of the one or more sensors fails, the hydraulic steering control system defaults to move the at least two tracks into the Ackerman steering mode.

A milling machine can include a frame; at least two tracks coupled to the frame for propelling the milling machine; first and second hydraulic cylinders configured to steer each of the at least two tracks, respectively; an adjustable hydraulic tie rod extending between the at least two tracks; first and second steering collars coupled to the each of the tracks to move the tracks, wherein the first hydraulic cylinder is coupled to the first steering collar and the second hydraulic cylinder is coupled to the second steering collar, and wherein the adjustable hydraulic tie rod is coupled to both of the steering collars; one or more sensors to determine the positions of the at least two tracks; and a hydraulic steering control system coupled to the first and second hydraulic cylinders and the adjustable hydraulic tie rod and configured to vary a steering mode of the at least two tracks between a parallel steering mode and an Ackerman steering mode, wherein if one of the one or more sensors fails, the hydraulic steering control system defaults to move the at least two tracks into the Ackerman steering mode.

A method of operating a steering system having a rotatable steering control, a steering actuator having a rod movable along a range of travel, a rotary device coupled to the steering control, and a valve assembly disposed between the rotary device and the steering actuator includes rotating the steering control in a first direction, displacing the rod toward an end of the range of travel, and determining when the rod reaches the end of the range of travel. The method also includes, after determining, actuating the valve assembly from a first position in which the rotary device is not in fluid communication with the steering actuator, to a second position in which the rotary device is in fluid communication with the steering actuator, and inhibiting further rotation of the steering control in the first direction due to back pressure on the rotary device.

A method of controlling a work machine having at least one wheel includes providing a controller, an operator control, and a steering system including a steering wheel position sensor, a road wheel angle sensor, a speed sensor, and a feedback device. The method includes detecting a change in steering wheel position via the steering wheel position device and a wheel speed of the at least one wheel via the speed sensor. A predicted lateral acceleration is calculated by the controller as a function of wheel speed and a feedback torque is determined by the controller as a function of the predicted lateral acceleration. The feedback torque is determined from a plurality of feedback torque curves stored by the controller, where each of the plurality of feedback torque curves corresponds to a sensitivity level selectable from the operator control. The feedback torque is commanded to the feedback device.