Abstract: The present invention relates to a redundancy circuit of an electric power steering system, the redundancy circuit comprising: a plurality of electronic control units for checking whether a breakdown occurs by crossing each other, and adjusting a control ratio according to the occurrence of the breakdown; and a selection control unit for receiving an input of the control ratio and control amount information of the plurality of electronic control units to determine control amounts of each of motors provided in the same number as the plurality of electronic control units.

Abstract: A method and system for validating the calculated localization (15) of a vehicle are devised. The vehicle (1) is equipped with P independent localization data sources (2-8), with P higher than or equal to 2.

Abstract: A steering motor generates a driving force based on a steering instruction from a travel control unit and applies a steering axial force to a rack shaft to thereby cause vehicle wheels to be steered. An action planning unit, through the travel control unit, initiates traveling at a starting position of parking on a movement path by suppressing the steering axial force to be less than a maximum driving force of the steering motor.

Abstract: 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.

Abstract: The present disclosure relates to an apparatus and a method for controlling a steer-by-wire system. In more details, the present disclosure relates to an apparatus and method for determining whether a catch-up is occurred due to a counter electromotive force in a rack drive motor in a steer-by-wire system and reflecting torque information that has not been output due to the catch-up on a steering reaction force motor, and thus providing an accurate steering sense for a driver.

Abstract: A steer-by-wire system for a motor vehicle includes at least two wheels which are steerable independently of one another in a normal operating mode of the steer-by-wire system, at least two steering actuators, each one being assigned to one of the steerable wheels and being configured for adjusting a steering angle of the particular steerable wheel, and at least one steering electronics system which is signally connected to the steering actuators and which is configured for controlling the steering actuators individually on the basis of steering commands.

Abstract: A control device for an unmanned vehicle includes a temperature data acquisition unit acquiring temperature data of hydraulic oil supplied to a first hydraulic actuator actuating a steering device of the unmanned vehicle, and a command output unit outputting a change command for changing a travel parameter of the unmanned vehicle based on the temperature data.

Abstract: A rotation control system for a steering system of a vehicle includes a steering shaft. The rotation control system also includes at least one component operatively coupled to the steering shaft, the steering shaft switchable between a rotational condition and a non-rotational condition during operation of the vehicle, the rotational condition occurring during a manual driving mode and the non-rotational condition occurring during an autonomous driving mode. The rotational control system further includes a condition switching device for allowing a user to switch between the rotational condition and the non-rotational condition, the condition switching device comprising at least one of a switch, a button, and a voice prompt.

Abstract: A method of control includes operating in autonomous mode and steering according to a tracking angle. The method also includes receiving a torque signal indicating a measured torque being applied to a steering control device and determining a difference between an expected torque and the measured torque, and based on a direction of the expected torque, the direction of the measured torque, and the difference between the two, switching from autonomous mode of operation to manual mode operation.

Abstract: The technology relates to determining the current state of friction that a vehicle's wheels have with the road surface. This may be done via active or passive testing or other monitoring while the vehicles operates in an autonomous mode. In response to detecting the loss of traction, the vehicle's control system is able to use the resultant information to select an appropriate braking level or braking strategy. This may be done for both immediate driving operations and planning future portions of an ongoing trip. For instance, the on-board system is able to evaluate appropriate conditions and situations for active testing or passive evaluation of traction through autonomous braking and/or acceleration operations. The on-board computer system may share slippage and other road condition information with nearby vehicles and with remote assistance, so that it may be employed with broader fleet planning operations.

Abstract: An apparatus for operating a pedestrian detection and collision mitigation system (PDCMS) function of a vehicle includes: a front detection sensor detecting a presence of a pedestrian on a driving lane of the vehicle and a distance and a relative speed between the pedestrian and the vehicle; a vehicle sensor detecting a speed of the vehicle; an electronic control unit operating a PDCMS function based on information detected by the front detection sensor and the vehicle sensor; and a warning unit operated to inform a driver of a collision of the pedestrian with the vehicle by a control of the electronic control unit.

Abstract: An apparatus includes a front detection sensor detecting presence of a pedestrian on a driving lane of the vehicle, gaze information of the pedestrian, and a distance and a relative speed between the pedestrian and the vehicle; a vehicle sensor detecting at least one of a speed, an acceleration, a steering angle, a steering angular velocity, or a pressure of a master cylinder of the vehicle; an electronic control unit activating a function of a pedestrian detection and collision mitigation system based on information detected by the front detection sensor and the vehicle sensor; and a warning unit operated to inform a driver of a collision of the pedestrian with the vehicle by controlling the electronic control unit.

Abstract: A rotation control system for a steering wheel is provided. The rotation control system includes a steering wheel and a steering shaft operatively coupled to the steering wheel. The rotation control system also includes at least one component operatively coupled to the steering shaft configured to switch the steering wheel between a rotational condition and a non-rotational condition.

Abstract: A modification system is provided for modifying the steering ratio for a vehicle having a tiltable telescopic boom arm (6). The vehicle has steered wheels (11), a steering wheel, and a steering transmission device serving to transmit steering movement between the steering wheel and the steered wheels (11) with a steering ratio R=Alpha/Beta. Beta is the steering angle of the wheels, and Alpha is the turning angle of the steering wheel. The system includes a sensor configured to determine a parameter relating to the telescopic arm. A control module controls the steering ratio that is configured to modify the steering ratio R as a function of the parameter relating to the telescopic arm. A wheeled vehicle is provided, fitted with such a steering ratio modification system.

Abstract: According to one example, a control system is disclosed. The system can include a steering system configured to direct a movement of a compactor within a compacting area. The system can include one or more sensors configured to generate data indicative of operational criteria of the compactor, the one or more sensors including a speed sensor configured to measure a speed of the compactor over a surface within the compacting area and a controller communicatively coupled to the one or more sensors. The controller can be configured to: receive data indicative of the speed of the compactor from the speed sensor, determine if the speed of the compactor exceeds a first threshold speed, and if the speed of the compactor exceeds the first threshold speed, control the steering system to limit a turning angle to a predetermined value such that a turning radius of the compactor is increased.

Abstract: A steering device for a motor vehicle is described, the steering device comprising a steering element for steering the motor vehicle, and an actuating element by means of which wheels of the motor vehicle are adjusted as a function of an actuation of the steering element. The steering element has a steering assist unit associated with it, in particular an electronic steering assist unit for active return of the steering element, the steering assist unit comprising a motor and an open- and closed-loop control unit which drives the motor for generating an assist torque. The open- and closed-loop control unit receives data from a first sensor which directly senses the position of the actuating element, and drives the motor as a function of the position of the actuating element. Further described is a method of controlling a steering device.

Abstract: A steering column assembly configured to couple to a steering wheel is provided. The assembly includes a steering column shaft having a first end and a second end, the second end configured to couple to the steering wheel. The assembly also includes an intermediate shaft coupled to the steering column shaft first end. The assembly further includes a steering input pinion coupled to the intermediate shaft. The assembly yet further includes a counter rotation mechanism configured to counter rotate rotational movement of the steering column assembly such that the steering wheel does not rotate.

Abstract: The invention concerns a method for determining the direction of longitudinal travel of a vehicle comprising a step (a) of collecting a first signal (Signal1), representative of a first driving parameter, such as the steering-wheel torque, and of which the sign of the value and/or the sign of the variations is not dependent on the direction of longitudinal travel of the vehicle, a step (b) of collecting a second signal (Signal2), representative of a second driving parameter separate from the first driving parameter, such as the yaw rate, and of which the sign of the value and/or the sign of the variations changes on the basis of the direction of longitudinal travel of the vehicle, then a step (c) of comparing signs during which the sign of the value, or of the variation, of the first signal (Signal1) is compared with the sign of the value, or of the variation, of the second signal (Signal2) in order to deduce therefrom the direction of longitudinal travel of the vehicle, depending on whether said signs are id

Abstract: Technical solutions are described for generating a damping torque in a magnetic torque overlay (MTO) steering system. An example method includes generating a damping torque based on a vehicle speed value, a handwheel velocity value, and a differential pressure value. The method further includes detecting an off-road condition, and in response, computing an off-road damping torque signal based on one or more of the vehicle speed value, the handwheel velocity value, the differential pressure value, and a handwheel angle value. The method also includes scaling the damping torque by the off-road damping torque signal in response to detecting the off-road condition.

Abstract: An automobile cornering rollover prevention system comprises a speed controller, a wheel deflection measuring instrument mounted on a front wheel of the automobile, force sensors mounted on axis positions of four wheels, and an angular speed measuring instrument and a speed controller mounted on the front wheel of the automobile, and the wheel deflection measuring instrument, the angular speed measuring instrument and the force sensor are all electrically connected to the speed controller. The speed controller is connected to a brake system of the automobile, so that the speed can be intelligently reduced through the brake system. When a driver changes ?1 according to a road condition, the speed controller may calculate a critical radius in real time and then compare the speed and give a command in real time for controlling the speed, so that the speed is maintained in an ideal range.

Abstract: Technical solutions are described for a payload detection module that detects payload using one or more steering system control signals and generates an axle load factor. An example payload detection module includes a rack torque module to determine a rack torque, a reference model module to determine a reference rack torque for the steering system based on a load scale factor, and a load factor calculation module to compute the axle load factor based on a difference between the rack torque and the reference rack torque. Further, a blend factor module determines a load blend factor according to the axle load factor. Further yet, a signal combiner combines a blended nominal base assist and a blended highload base assist according to the load blend factor, the combination modifying a motor torque command, the motor torque command being sent to a motor to generate assist torque.

Abstract: A control device is configured for use in a steering system in a vehicle with electromotive servo assistance. The control device includes control device elements and electronic components for actuating a servo motor arranged in each control device element. The control device has chambers configured to accommodate the electronic components of the control device elements. The chambers are sealed off from one another in a watertight manner at least up to a defined filling level. The electronic components of the control device elements are split over different chambers.

Abstract: The invention relates to a method for compensating a stick-slip effect in the case of a recirculating ball steering system (20) having a steering housing (22), in which a steering piston (24) is supported between a first working chamber (34) and a second working chamber (36), wherein the steering piston (24) has a toothed region (26) on the steering-piston outer wall of the steering position, with which toothed region teeth (28) of a segment shaft (30) mesh, the steering piston (24) can be moved along a longitudinal axis X-X, the working chambers (34, 36) are connected to a control valve (39) by means of pressure-medium lines in order to provide steering assistance, the control valve (39) is connected to a processor unit (40), by means of which valves of the control valve (39) can be actuated, and the processor unit (40) is connected to a sensor (42), which determines rotation of the steering column both in a first direction of rotation and in a second, opposite direction of rotation.

Abstract: A behavior control apparatus for a vehicle, comprising a control unit that controls braking/driving forces of wheels so that the magnitude of a deviation between a steering angle and a steering angle conversion value of a yaw rate decreases when it is determined that the deviation exceeds a threshold value in magnitude and the vehicle is in an understeer state; the vehicle has a steering device including a variable gear ratio type rack bar; and, when the sign of the steering angle is the same as the sign of the offset amount and the zero point offset amount exceeds a reference value in magnitude, the control device corrects at least one of the threshold value and the magnitude of the deviation according to the steering angle and the zero point offset amount so that it becomes difficult to determine that the magnitude of the deviation exceeds the threshold value.

Abstract: A collision avoidance apparatus includes a control unit that is configured to perform a collision avoidance process. The control unit determines whether or not an object is present ahead of the own vehicle. When the control unit determines that an object ahead is present, the control unit determines whether or not there is a likelihood of a collision between the object ahead and the own vehicle and whether or not a corner is present ahead of the own vehicle. When the control unit determines that a corner is not present and when a predetermined collision avoidance condition is established, the control unit is capable of changing a travelling direction of the own vehicle to avoid collision between the object ahead and the own vehicle. When the control unit determines that a corner is present, the control unit does not perform a travelling direction change of the own vehicle.

Abstract: A power-source voltage diagnostic device of an electric power steering apparatus that improves the performance for the anomalous detection of the motor power-source voltage VR-detecting circuit and is capable of continuing the assist control even if the extraordinary state is detected. When the failure (extraordinary state) detection of the VR-detecting circuit is performed by using the correlation between Vbat1-voltage obtained by the detecting section (Vbat1-detecting circuit) to detect the control voltage from the control power-source circuit and VR-voltage obtained by the detecting circuit (VR-detecting circuit) to detect the motor power-source voltage from the power source circuit, multiplexing is performed by providing VR-detecting circuits (VR-detecting circuit 1, VR-detecting circuit 2) of two systems and mutually comparing them so as to accurately perform the failure diagnosis of the VR-detecting circuits.

Abstract: Systems and methods for independently estimating a road surface friction coefficient value and a vehicular lateral velocity value are provided. In one example, the system includes: a self-aligning torque coefficient estimating module configured to obtain sensor signals from an electronic power steering (EPS) system and an inertial measurement unit and estimate a first self-aligning torque coefficient value based on the sensor signals using a recursive least square algorithm; a road surface friction coefficient value estimating module configured to obtain the estimated first self-aligning torque coefficient value and estimate a first road surface friction coefficient value based on the estimated first self-aligning torque coefficient value; and a feature control module configured to generate one or more control signals configured to control features of a vehicle based on the estimated first road surface friction coefficient value.

Abstract: In a diagnostic device, a determiner determines whether a rotational speed of an AC motor is within a low rotational-speed range in which its rotational speed is approximately zero. An input-voltage estimate calculator calculates, as an input-voltage estimate, an estimate of an input voltage to an inverter when it is determined that the rotational speed of the AC motor is within the low rotational-speed range. A malfunction determiner performs a diagnostic task. The diagnostic task calculates an absolute value of a difference between an input-voltage measurement value measured by an input voltage sensor and the input-voltage estimate. The diagnostic task determines whether the absolute value of the difference is higher than a predetermined voltage threshold. The diagnostic task determines that there is a malfunction in the input voltage sensor upon determining that the absolute value of the difference is higher than the predetermined voltage threshold.

Abstract: A control system and method for a hydraulic-power steering system of a vehicle including magnetic torque overlay (MTO) is provided. The control system and method minimize undesirable vibration in a handwheel of the vehicle as a result of disturbance in its front road wheels (e.g., road-wheel imbalance). In the control system and method, a base torque command is determined or generated. At least the base torque command is passed to a disturbance-rejection module. The disturbance-rejection module modifies the base torque command to minimize the vibration.

Abstract: An environmental sensing system relating to vehicle lane position includes first and second sensors respectively configured to provide first and second signals indicative of a vehicle lane position. A steering system achieves a desired lane position in response to a command from a controller to keep the vehicle in its lane, for example, during autonomous control of the vehicle. The controller uses the first signal if the first sensor provides a desired lane marker confidence. The controller switches to the second sensor and uses the second signal if the first sensor cannot provide the desired lane marker confidence and the second sensor can provide the desired lane marker confidence.

Abstract: Aspects of the disclosure relate to determining whether a feature of map information. For example, data identifying an object detected in a vehicle's environment and including location coordinates is received. This information is used to identify a corresponding feature from pre-stored map information based on a map location of the corresponding feature. The corresponding feature is defined as a curve and associated with a tag identifying a type of the corresponding feature. A tolerance constraint is identified based on the tag. The curve is divided into two or more line segments. Each line segment has a first position. The first position of a line segment is changed in order to determine a second position based on the location coordinates and the tolerance constraint. A value is determined based on a comparison of the first position to the second position. This value indicates a likelihood that the corresponding feature has changed.

Abstract: A voltage sensor abnormality diagnosis apparatus is applied to a motor controller operating switching of inverter by a switching signal for complementary on and off and diagnoses abnormality of input voltage sensor. An input voltage estimated value calculation section calculates input voltage estimated value by multiplying voltage command amplitude deviation by conversion coefficient, the voltage command amplitude deviation being obtained by subtracting theoretical voltage command amplitude, which is amplitude of theoretical voltage command calculated by using a motor model expression, from a control voltage command amplitude, which is an amplitude of a control voltage command calculated by feedback control and has been corrected by the dead time correction amount. An abnormality determination section determines that the input voltage sensor is abnormal if an absolute value of a difference between an input voltage sensor value and the input voltage estimated value is larger than a voltage threshold value.

Abstract: The present invention provides a lateral control apparatus including: an offset measuring unit that measures current lateral offsets of at least two other vehicles at a current time based on a center of a driving lane; a preview offset calculating unit that predicts a lateral offset of the other vehicle based on the center of the driving lane based on a location and a speed of the other vehicle at a time when a predetermined time has elapsed to calculate a preview offset; a priority determining unit that determines a priority of the other vehicles based on a difference between the lateral offset and the preview offset; and a controller that generates a route for lane keeping control of own vehicle based on the lateral offset of the other vehicle to which a top priority is assigned by the priority determining unit.

Abstract: An electric power steering apparatus provides a steering assist force to the steering system of a vehicle by controlling driving of an assist motor in accordance with a steering force acting on the steering wheel. The electric power steering apparatus includes a yaw rate sensor that obtains a measured yaw rate of the vehicle, a vehicle speed sensor that detects the speed of the vehicle, a steering angle sensor that detects the steering angle of the steering wheel, and a torque estimating apparatus that estimates a self-aligning torque on the basis of the vehicle speed and data having a smaller absolute value among the measured yaw rate and the steering-angle standard yaw rate and that corrects the steering assist force on the basis of the estimated self-aligning torque.

Abstract: Provided is a method of controlling a vehicle equipped with individual steering devices and individual rotational force generating devices for respective wheels. According to the method, operation of at least one group of the steering devices and the rotational force generating devices is controlled in response to electrical control signals generated according to a user's command, so that control of the wheels starts at separate points in time.

Abstract: A collision avoidance assistance device includes a target control amount calculation unit configured to calculate a target control amount used for travelling on a target trajectory through which the vehicle passes, a first control amount calculation unit configured to calculate a first control amount to be applied by the first steering assistance system out of the target control amount, and output the first control amount to the first steering assistance system, and a second control amount calculation unit configured to calculate a second control amount to be applied by the second steering assistance system out of the target control amount, and output the second control amount to the second steering assistance system. The first control amount is set to be larger than the second control amount during a predetermined time period from a time of starting the collision avoidance assistance.

Abstract: A steering apparatus includes: a steering angle zero point detection unit configured to detect a zero point of a steering angle of a steering wheel; a history recording unit configured to record a detection history of the zero point; a characteristic variation determination unit configured to determine whether or not characteristic variation has occurred in a steering transmission system on the basis of the detection history; a pressure measurement unit configured to measure a pressure in one of a master cylinder and a wheel cylinder that apply a braking force to a vehicle wheel; and a prohibition unit configured to prohibit for a predetermined prohibition period one of detection of the zero point by the steering angle zero point detection unit and updating of the detection history by the history recording unit, when the pressure equals or exceeds a predetermined threshold.

Abstract: A solenoid valve device includes: a solenoid valve that includes a solenoid that is supplied with driving current to generate magnetic flux, and a valve element that is moved by the magnetic flux generated from the solenoid; and a control device that controls the solenoid valve. The control device includes an alternating current component in the driving current and supplies the driving current including the alternating current component to the solenoid, and detects an impedance of the solenoid.

Abstract: A system and method for converting a vehicle steering angle command to a vehicle steering torque command for a vehicle steering system in a vehicle. The method estimates a self-aligning torque that defines the torque that maintains a vehicle steering wheel at a neutral steering position or to a position that makes no slip angle at the road wheel, applies known total steering torque commands to the steering system at a plurality of sample time steps where the known steering torque commands include the self-aligning torque, and measures a vehicle steering angle at each time step. The method then models the steering system of the vehicle using the torque commands, the measured steering angles, a system delay and a plurality of unknown parameters.

Abstract: For controlling supply priorities, a hydraulic system includes several loads, a pump, and a tank. One load has a first-level supply priority, and optionally a second load has a second-level supply priority subordinate to the first level. A third load has a third-level supply priority subordinate to the second level. Each load can be connected to the pump by a separate supply line. The supply lines for the first and the optional second load are connected to the pump by a common load-pressure-controlled priority valve and the supply line for the third load is connected to the pump by an additional load-pressure-controlled priority valve. A first load-pressure line leading to the pump is connected to a load-pressure line of the third hydraulic load and to a second load-pressure line.

Abstract: A first valve opening degree correction value computation unit computes a correction value (first valve opening degree correction value) for the absolute value of a valve opening degree command value on the basis of a rotation speed deviation computed by a rotation speed deviation computation unit in a pump driving motor control unit. A second valve opening degree computation unit computes a correction value (second valve opening degree correction value) for the valve opening degree command value on the basis of the sign of the valve opening degree command value and the first valve opening degree correction value. A correction value addition unit adds the second valve opening degree correction value to the valve opening degree command value set by the valve opening degree command value setting unit.

Abstract: A vehicle speed control device is provided. The device includes a steering device which steers left and right wheels, first and second electric motors which separately apply power to the left and right wheels, an operation amount acquisition unit which acquires an acceleration operation amount by the driver of the vehicle, a steering angle acquisition unit which acquires a steering angle which is a value between an inner wheel steering angle and an outer wheel steering angle; a vehicle speed acquisition unit configured to acquire an actual speed of the vehicle; and a control unit configured to control the first electric motor and the second electric motor on the basis of the acceleration operation amount, the actual speed, the steering angle, and a steering geometry indicating a geometric relationship between the steering angle and a turning center of the vehicle.

Abstract: In one aspect of the invention, a power steering assist system is provided. The system includes a housing, an actuator assembly, a rotary valve assembly, a bearing assembly, a differential pressure transducer, and a coupler. The coupler includes a first end and a free second end, the free second end extending from the housing and configured to couple to a component of a steering gear system.

Abstract: Embodiments of the invention provide methods and apparatus for reducing steering effort in a vehicle. In one embodiment, a method for installing a steering-assist system onto a vehicle having an electrically powered steering system is provided. The method includes placing a controller between a torque sensor and an electronic control unit (ECU) disposed on the vehicle, coupling a primary signal line from the torque sensor to be in electrical communication with the controller, and coupling a secondary signal line to the controller to be in electrical communication with the ECU, wherein, when movement is detected by the torque sensor, the torque sensor provides a primary signal to the controller and the controller provides a secondary signal to the ECU, the secondary signal being different than the primary signal.

Abstract: A power steering assembly having an input shaft for connection to a steering wheel, an output shaft coupled to the input shaft for operational engagement with a steering rod, a servo controller, an actuator, a sensor system, and an evaluation unit for evaluating measurement values provided by the sensor system. The coupling between input and output shafts permits a relative rotation therebetween. The servo controller has a rotatable final control element with and driven by the output shaft. The steering force assistance is controlled depending on relative rotation between the input shaft and control element. The engagement between the output shaft and control element provides a relative displacement therebetween. The actuator relatively displaces the control element in relation to the output shaft. The sensor system measures at least one differential angle between the control element and output shaft or between the control element and input shaft.

Abstract: Disclosed is a steering system which is capable of ensuring that a wheeled excavator travels straight while being driven on a paved road. The steering system for wheeled construction equipment includes: a hydraulic oil pump; a steering motor connected to the hydraulic oil pump; a steering valve controlling the operation of the steering motor; a steering handle operating the steering motor and the steering valve according to steering manipulation by the driver; and a steering cylinder steered by the manipulation of the steering handle. The steering system further includes an idle mode control unit which converts working mode into a steering mode not having straight line driving recovery performance when working mode, in which working and driving are enabled, is selected, and which converts exclusive driving mode into a steering mode having the straight line driving recovery performance through a signal input when the exclusive driving mode, in which only driving is enabled, is selected.

Abstract: A vehicle steering controller includes a shape recognizer that recognizes a shape of a road on the basis of a captured image, a steering control unit that controls steering of a vehicle on the basis of the shape of the road recognized by the shape recognizer, and a determiner that determines whether or not the shape of the road recognized by the shape recognizer is that of a transitional section between a curved road section and a linear road section. If the determination made by the determiner is negative, then the shape recognizer recognizes the shape of the road by performing an approximation using an approximation expression having a degree of one or two, otherwise the shape recognizer recognizes the shape of the road by performing an approximation using an approximation expression having a degree of three.

Abstract: A power steering apparatus including a power cylinder, first and second pumps, a control valve serving for selectively supplying a working fluid supplied from the first or second pump to one of a pair of pressure chambers of the power cylinder in accordance with a steering operation, first and second reservoir tanks, and a return passage changeover valve disposed between the control valve and the first and second pumps, the return passage changeover valve serving for communicating the first and second pumps with the control valve regardless of an axial position of a valve element and communicating one of the first and second reservoir tanks with the control valve in accordance with the axial position of the valve element to thereby carry out changeover between circulating fluid passages for circulating the working fluid to the first reservoir tank and the second reservoir tank.

Abstract: A pump rotation speed correcting unit includes a valve opening degree command differential value computing unit, a pump rotation speed correction value computing unit, and a correction value adding unit. The valve opening degree command differential value computing unit computes a temporal differential value of a valve opening degree command value that is set by a valve opening degree command value setting unit. The pump rotation speed correction value computing unit computes a correction value of a pump rotation speed command value on the basis of the valve opening degree command differential value. The correction value adding unit adds the pump rotation speed correction value to the pump rotation speed command value that is set by the pump rotation speed command value setting unit.

Abstract: A method for selectively charging and discharging a steering accumulator are provided. One vehicle steering system includes a hydraulic pump configured provide a source of pressurized hydraulic fluid for use in steering the vehicle. The steering system also includes an accumulator configured to hold pressurized hydraulic fluid from the pump for use in steering the vehicle in case of need. The steering system includes a charging circuit configured to selectively allow the hydraulic fluid to flow from the hydraulic pump to the accumulator based on a fluid pressure applied by a first pilot and a second pilot. The steering system includes a charging bypass circuit configured to allow the hydraulic fluid to flow to a steering control unit and to bypass the charging circuit. The hydraulic pump supplies fluid to the charging circuit and the bypass circuit.