Abstract: A torque-based method to steer a vehicle equipped with a steer by wire system begins when a driver applies torque to a steering wheel so as to change the direction in which the vehicle travels. Two sensors, a steering wheel angle sensor and a steering wheel torque sensor then generate an angle signal and a torque signal, respectively. In the unlikely event the vehicle steering system is malfunctioning, the steering wheel torque sensor will still generate a torque signal. This torque signal is used in place of the angle signal to generate the reference signal. Once the reference signal is generated, then it can be used to generate the road wheel angle signal, which is in turn used to position the road wheels accordingly.

Abstract: The invention relates to a method of storing information in the form of signals from a control system in a vehicle, said method comprising the step of reading a signal on recurrent sampling occasions and increasing the value of a counter which represents a signal value interval. The method further comprises the steps of measuring on each sampling occasion a change of the signal in relation to a previous signal value, comparing change with the threshold value, and, if the change is greater than the threshold value, increasing the value of a counter associated with this threshold value.

Abstract: A steering system for an automotive vehicle having two front wheels and two rear wheels is provided.

Abstract: A power steering apparatus includes a motor, a torque sensor, and a motor resolver. The motor generates an assisting force to reduce the steering force of the steering wheel. The torque sensor detects the steering torque of the steering wheel. The motor resolver detects the rotational angle of the motor. An electronic control unit (ECU) detects the absolute position of the steering wheel based on a detection signal Rt sent from a second resolver of the torque sensor and a detection signal Rm sent from a motor resolver. As a result, the cost is reduced and the absolute position of the steering wheel is accurately detected.

Abstract: In a control unit for an electrical-motor-driven power steering apparatus, there are provided an assist current command value calculated based upon a steering torque of a steering wheel, an assist current control value calculated based upon a motor current value of a motor and the assist current command value. A motor outputs an assist force based upon the assist current control value. Further, the control unit provides an estimation means for estimating a road surface &mgr; based upon at least one of the motor current value and the steering torque. To the control unit, there are further inputted a vehicle speed obtained based upon rotation of a wheel, and a steering angle obtained based upon rotation of the steering wheel. Therefore, the estimation means estimates the road surface &mgr; by comparing with a previously memorized standard value corresponding to the vehicle speed and the steering angle.

Abstract: A method for detecting a loss of motor control in an electric power steering system is disclosed. In an exemplary embodiment, the method includes determining a duty cycle of a steering command signal generated by a controller. The steering command signal commands a steering mechanism to be turned in either a first or a second direction, the second direction being opposite to the first direction. A steering velocity of the steering mechanism is determined, the steering velocity being characterized by a steering velocity magnitude and a steering velocity direction whenever the steering velocity is greater than zero. The steering velocity direction corresponds to either the first or the second direction. The duty cycle is then compared to a first selected value, and the steering velocity magnitude is compared to a second selected value.

Abstract: A method for controlling the rear steering angle of a vehicle includes receiving a plurality of signals indicative of rear steering angle; checking at least one of the plurality of signals to determine if it falls within a valid range; correlating at least a first signal of the plurality of signals with at least a second signal of the plurality of signals to determine if either the first signal or the second signal is invalid; and rejecting any signals found to be invalid.

Abstract: A method for validating a signal indicative of a speed of a vehicle includes receiving a plurality of signals indicative of vehicle speed; correlating at least a first of the received signals with at least a second of the received signals to determine if either signal is invalid; and signaling a rejection of any signal found to be invalid.

Abstract: An apparatus and method for controlling a mechanism for positioning video cameras for use in measuring vehicle wheel alignment includes optical targets for mounting to the wheels of a vehicle, at least one video camera for viewing said optical targets and producing at least one image thereof, a computer system for measuring said at least one image and for using said measurements to compute vehicle wheel alignment information, a positioning system for positioning said at least one video camera such that said optical targets are visible to said at least one video camera and such that said at least one video camera can produce said at least one image of said targets, and a controller for controlling said positioning system such that a user of said apparatus can cause said at least one video camera to be positioned in at least one desired position and such that said user can further cause said controller to remember said at least one desired position so that any user can, at a later time, cause said controller to

Abstract: A method of controlling an automotive electric power steering system includes estimating a first road reaction torque from driver's steering torque detected by a steering torque detector. A second road reaction torque is estimated from the steering angle detected by a steering angle sensor. A returning torque compensator calculates a steering wheel-assisting torque from the second road reaction torque. An assisting torque is generated by an electric motor according to the result of the calculation, and is controlled in a direction to return the steering wheel to its center position. The returning torque compensator determines whether the steering angle sensor is faulty when the difference between the first and second road reaction torques is greater than a given value.

Abstract: A reduced control system suitable for control of an active suspension system as a controlled plant is described. The reduced control system is configured to use a reduced sensor set for controlling the suspension without significant loss of control quality (accuracy) as compared to an optimal control system with an optimum sensor set. The control system calculates the information content provided by the reduced sensor set as compared to the information content provided by the optimum set. The control system also calculates the difference between the entropy production rate of the plant and the entropy production rate of the controller. A genetic optimizer is used to tune a fuzzy neural network in the reduced controller. A fitness function for the genetic optimizer provides optimum control accuracy in the reduced control system by minimizing the difference in entropy production while maximizing the sensor information content.

Abstract: A fail-safe system used in integrated control of a vehicle includes structural-element control portions. Preset priority degrees are given to the structural-element control portions, respectively. A manager control portion stores one or more substitute programs designed to implement functions of ones among the structural-element control portions which are necessary for travel of the vehicle. A downloading device operates for, when one of the structural-element control portions which is necessary for travel of the vehicle fails, selecting one from non-failed ones of the structural-element control portions as a download destination in accordance with the priority degrees and downloading the substitute program corresponding to the failed structural-element control portion into the selected download-destination structural-element control portion. The selected download-destination structural-element control portion is lower in priority degree than the failed structural-element control portion.

Abstract: To realize reliable detection of abnormality of a position detecting device regardless of a rotational position of a rotor, and attain simplification of a circuit structure and reduction of cost.

Abstract: In diagnostic apparatus and method for a motor-driven power-assisted steering system, an abnormality determining section detects a state in which the detected normal/reverse drive current indicates an opposite to a direction of the normal/reverse revolution drive torque and determines whether the state is in excess of a predetermined abnormality determination criterion so as to determine an occurrence in abnormality of the power-assisted steering system, the abnormality determining section comprising a sensitivity reducing section that varies a sensitivity of the abnormality determination criterion in a decrease direction as an absolute value of the detected normal/reverse drive current becomes smaller.

Abstract: In an electric power steering control system, a road surface reaction torque estimator estimates a road surface reaction torque on the basis of steering wheel angle. A neutral point learning unit and a neutral point compensator learn a neutral point of the steering wheel on the basis of the road surface reaction torque with respect to the steering wheel angle. A return torque for returning the steering wheel to the neutral point is computed from a difference between a current angle of the motor and the learned neutral point. As a result, the steering wheel returns to the neutral point under the current driving condition without application of any force to the steering wheel by the driver.

Abstract: A method of determining a vehicle steering wheel angle by receiving at least one steering sensor output from at least one steering sensor. The method then receives a vehicle speed signal. A centered steering angle is determined based on the received vehicle speed signal and the steering sensor output.

Abstract: A motor vehicle steering system is provided which includes: an operation member for steering a motor vehicle; a steering mechanism for turning steerable wheels of the motor vehicle; a first actuator and a second actuator each operative to apply a driving force to the steering mechanism; and a clutch mechanism operative to mechanically engage and disengage the operation member to or from the steering mechanism. When the first and second actuators operate normally, the clutch mechanism is brought into the disengaged state, and a driving force is applied to the steering mechanism from the first and second actuators and, when one of the first and second actuators malfunctions, the clutch mechanism is brought into the engaged state, and the steering assist force is generated by the other normal actuator in accordance with the operation of the operation member.

Abstract: During traveling of rolling stock on a route, running velocity of the rolling stock is detected. Vertical acceleration is also detected at a carbody above spring rigging of truck and a component is extracted in a predetermined frequency range from the vertical acceleration. When an absolute value of the vertical acceleration in the frequency range exceeds preset limit vertical acceleration corresponding to running velocity, the rolling stock is judged as being derailed. In another embodiment double integral of the vertical acceleration is carried out every predetermined evaluating time to calculate a vertical displacement amount. In the case that the vertical displacement amount is negative and an absolute value thereof is not less than a predetermined reference value, it is then determined that the rolling-stock is derailed.

Abstract: The invention provides a linkless steering apparatus for vehicle in which a steering mechanism and steering wheel are not mechanically connected. The steering apparatus drives a steering motor of the steering mechanism in accordance with a steering torque so as to increase or decrease a steering angle. The steering torque for this purpose is calculated based on results obtained by detecting a rotational angle of an electric motor (a reaction-force motor) connected to a rotational shaft of the steering wheel and an electric current flowing to the electric motor, a moment of inertia of the steering wheel, and a moment of inertia of the electric motor. Therefore, it is possible to avoid use of a torque sensor which requires a large space for installation thereof and high cost.

Abstract: A torque detection apparatus includes a torque sensor, a sensor circuit, a signal processing circuit, and an abnormal state monitoring circuit. The torque sensor is arranged on a rotary shaft and operates to output a predetermined electric signal related to a torque applied to the rotary shaft. The sensor circuit outputs the predetermined electric signal as a sensor circuit signal. The signal processing circuit processes the sensor circuit signal in order to output a torque detection signal. The abnormal state monitoring circuit is arranged proximate the signal processing circuit and operates according to the sensor circuit signal to detect an abnormal operation.

Abstract: An industrial lift truck includes a steering unit which operates in response to steering commands to operate an electric steering motor that turns a steerable wheel. The integrity of the steering unit is checked by applying alternating steering commands to the steering unit and monitoring the resulting current flow through the steering motor.

Abstract: In an automatic steering device adapted to generate a target steering movement of steering vehicle wheels and to actuate a steering mechanism so that the steering vehicle wheels are steered to follow the target steering movement in a feedback manner that a deviation of an actual steering movement from the target steering movement of the steering vehicle wheels is canceled, the speed of canceling the deviation is increased along with increase of the deviation at least up to a certain threshold value.

Abstract: A steer by wire control system having a steering wheel unit responsive to a steering wheel torque command and a road wheel unit responsive to a road wheel unit command is disclosed. A master control unit may be employed to perform processing as necessary. A method for steering a vehicle including receiving a tie-rod force signal, a road wheel position signal, a vehicle speed signal, a steering wheel position signal, and a feedback torque signal. Combining these signals to generate the steering wheel torque command signal and road wheel command signal to provide the operator with tactile feedback, while road wheel command signals are sent to road wheel units to provide steering direction. An Ackerman correction unit may also used to correct the left and right road wheel positions to track about a common center.

Abstract: A motor is stopped when a steering angular speed is not greater than a stop threshold VS and a motor electric current value Im is kept within a motor stop range &Dgr;I for a predetermined time period. The value of a steering torque increases as the motor electric current value Im increases. Therefore, the motor can assuredly be stopped when the steering torque is small. Further, when the motor is off, the sensitivity for motor actuation with respect to a change in the steering angle is set higher as the value of the steering angle increases.

Abstract: A closed loop steer by wire control system has three main components, a steering wheel unit, a roadwheel unit, and a master control unit. Signals generated by sensors in the steering wheel unit and roadwheel unit are passed back to the master control unit for processing. These signals include tie-rod force signals, and a steering wheel position signal. The master control unit uses these signals to calculate a steering wheel reaction torque signal which is sent back to the steering wheel unit to provide the operator with tactile feedback, while roadwheel command signals are sent to roadwheel units to provide steering direction. An Ackerman correction unit is also used to correct the left and right roadwheel positions to track about a common center.

Abstract: A method and apparatus that allows for safely operating a vehicle when an automatic steering control feature of a guidance control system is in operation. One or more sensors are used to determine whether the operator is in the vehicle. If the sensors detect that the operator has left the vehicle, the vehicle is shut off. The safety system includes one or more software programs that operate to determine whether the guidance control system is operating properly. More specifically, a control unit is coupled to the microprocessor and the steering control mechanism for determining whether or not an error condition has occurred. In the event that an error condition has occurred, the guidance control system is disengaged and control of the vehicle is turned over to the operator. In one embodiment, the safety system determines whether the operator is ready to take control of the vehicle prior to disengaging the guidance control system.

Abstract: A vehicle electric assist steering system (10) includes a switching circuit (56) for providing electrical power to an electric motor (52) of the vehicle steering system. The switching circuit (56) has a temperature condition. A temperature sensor (69) is coupled with the switching circuit (56) for providing an output signal (71) having a value indicative of the temperature condition of the switching circuit (56). A stall detector (70) is responsive to the output signal (71). The stall detector (70) is operable to reduce power to the electric motor to different level during a stall condition based on the sensed temperature condition of the switching circuit (56).

Abstract: An electric power steering apparatus includes a motor 1 which produces an auxiliary steering force in accordance with, for example, a steering torque detected by a torque sensor 7; a motor drive circuit 2 which controllably drives the motor 1; a power supply voltage detecting circuit 17 which detects the power supply voltage VB of the motor drive circuit 2; and a microcomputer 9. The microcomputer 9 detects terminal voltages VM+ and VM− of the motor 1 when the power supply voltage detecting circuit 17 determines that the power supply voltage AB is higher than a predetermined value. Then, the microcomputer 9 makes a decision to determine whether the detected terminal voltages VM+ and VM− are not predetermined values VTHH and VTHL, respectively. If it is determined that the terminal voltages VM+ and VM− are not the predetermined values VTHH and VTHL, respectively, then the microcomputer 9 determines that a fault has occurred on the lines connected to the motor 1.

Abstract: In diagnostic apparatus and method for a motor-driven power-assisted steering system, an abnormality determining section detects a state in which the detected normal/reverse drive current indicates an opposite to a direction of the normal/reverse revolution drive torque and determines whether the state is in excess of a predetermined abnormality determination criterion so as to determine an occurrence in abnormality of the power-assisted steering system, the abnormality determining section comprising a sensitivity reducing section that varies a sensitivity of the abnormality determination criterion in a decrease direction as an absolute value of the detected normal/reverse drive current becomes smaller.

Abstract: A vehicle steering apparatus controller that enables a sub-computer having a capacity lower than that of a main computer to recognize computation results in the same control cycle as the main computer. A main computer of the controller computes an auxiliary torque command value of a steering motor based on the torque of a steering wheel and the velocity of the vehicle in a main control routine. A sub-computer of the controller computes a value equivalent to the command value based on the torque and the vehicle velocity in each cycle of a sub-control routine, which is longer than that of the main control routine. The sub-computer includes a first comparison circuit for comparing the command value and the torque in each cycle of the main control routine and a second comparison circuit for comparing the command value and the equivalent value in each cycle of the sub-control routine.

Abstract: A method and an arrangement for operating an actuator in a motor vehicle are proposed. A first and/or a second operating variable signal is determined and a fault check thereof is carried out. When a fault occurs, a first reaction is immediately initiated, which can represent, for example, a limiting of the adjusting speed and/or of the acceleration of the actuator. When the fault condition has been present for a longer time, a second reaction is initiated, which applies a substitute signal instead of the faulty one for control or which consists of a switching off of the actuator operation.

Abstract: A method is disclosed for controlling a backing maneuver of an automotive vehicle and trailer combination in which the vehicle has operator-actuated front wheel steering and microprocessor-actuated, reversible electric motor driven rear wheel steering. For a given initial alignment of vehicle and trailer, the computer-executed method first determines whether the driver needs to pull forward before commencing the backing operation. The driver is then requested to turn the front wheels in a direction suitable for backing the vehicle without a trailer in the desired direction. The process then determines whether the driver needs to perform counter front wheel steering before backing. Then the process controls the steering of the rear wheels during the backing operation.

Abstract: A profile of a designated road by which a vehicle is guided to a destination is predicted by road map data. In the case where it is difficult for the own vehicle to pass through a curve of the designated road ahead of the own vehicle, a warning is given to a driver or vehicle speed is automatically reduced. Whether or not the car is correctly running on the designated road is decided by deviation &Dgr;&thgr; (=&thgr;V−&thgr;M) between azimuth angle &thgr;V of the actual advancing direction of the own vehicle and azimuth angle &thgr;M of the designated road. When it is decided that there is a possibility that the own vehicle is running off the designated road, the warning is given or automatic speed reduction is stopped or suppressed. Due to the foregoing, it is possible to prevent the own vehicle from being improperly controlled and it becomes possible for a driver from feeling a sense of incongruity.

Abstract: A steering system for vehicles can be operated in a normal mode, in which a steering handle actuated by the driver and steered vehicle wheels are connected to one another via a control system, and in an emergency mode, in which the steering handle and the steered vehicle wheels are positively coupled. To achieve a steering system which increases the operational reliability of the steering system by simple design measures, a steering-angle control unit for a steering-angle actuator actuates the steered vehicle wheels. The control unit contains a first steering-angle control system, and a manual-torque control unit for a manual-torque actuator actuates the steering handle for the purpose of simulating manual torques. The control unit also contains a first manual-torque control system, and the steering-angle control unit comprises a second manual-torque control system, which is connected redundantly with the first manual-torque control system of the manual-torque control unit.

Abstract: An arrangement for steering a motor vehicle having at least two steerable wheels including steering equipment for setting the position of the steerable wheels as a function of a desired steering angle signal and braking equipment which is present in the vehicle and which, in the event of a fault in the steering equipment, produces selectively different braking forces at the wheels as a function of the desired steering signal. A method for steering a motor vehicle in the event of failure of the steering equipment includes the step of applying different braking forces to the vehicle wheels in accordance with a desired steering angle signal.

Abstract: A steering system of a non-tracked motor vehicle has steered vehicle wheels are connected in normal operation with respect to the effect with a steering handle only by way of an electronic automatic control unit which continuously monitors itself with respect to a correct operation. As a function of a desired-value generator, which is operated by the steering handle, this automatic control system operates an adjusting drive for the steering adjustment of the steered vehicle wheels. In the event of a malfunctioning of the automatic control system, a forced coupling is automatically switched effective between the steering handle and the steered vehicle wheels. This also takes place if the performance limit of the adjusting drive is reached so that the driver is capable of assisting the adjusting drive by the driver's manual force on the steering handle.

Abstract: To keep low the cross frequency of current feedback control and provide a good steering feeling, a first operation expression is selected when a difference &xgr; between a current instruction value computed based on a steering state of a steering wheel and a traveling state of a vehicle and a motor drive current value supplied from a battery to a motor for providing assist force to a system for transmitting power from the steering wheel to the wheels is larger than a predetermined value Th1, a second operation expression is selected when the difference &xgr; is smaller than the predetermined value Th1, and the difference &xgr; is corrected using the selected operation expression.

Abstract: A controller for an electric power assisted steering system comprises a drive circuit (2) for controlling current to a motor (1) and a data processor (8) for controlling the motor current and hence assistance torque. A circuit (9) generates a current limit which is a monotonically decreasing function of vehicle speed. A comparator (6) compares motor current with the current limit and switches off the drive circuit (2) if the current limit is exceeded.

Abstract: An electric power steering apparatus for assisting steering based on an output of a torque sensor which detects a steering torque, the apparatus cumulates the outputs at each detection for a predetermined period of time, then compares the cumulated value with a predetermined value, and detects a displacement of the torque sensor's neutral point based on the comparison result. Therefore it is possible to detect even a small displacement of the torque-sensor neutral point.

Abstract: Control unit in an electric power steering apparatus includes a motor drive inhibition section for inhibiting output of a motor control signal on the basis of at least a steering torque signal supplied from a steering torque sensor. The control unit also includes a zero-value setting section for, when drive inhibition signals are output by the motor drive inhibition section, setting a target motor current signal to a zero value irrespective of a value of the steering torque signal, and an inhibition cancellation section for cancelling the drive inhibition signals when an offset between the target motor current signal and the detected motor current signal becomes zero after the target motor current signal is set to the zero value by the zero-value setting section.

Abstract: An electric power steering apparatus for a vehicle includes a protection circuit for stopping operation of an electric motor provided to apply a steering assist force to a steering system of the vehicle. The protection circuit is operable to stop operation of the electric motor when an ignition off signal is supplied from an ignition sensor and at least one of an engine speed signal supplied from an engine speed sensor and a vehicle velocity signal supplied from a vehicle velocity sensor falls below a corresponding predetermined value. Even if an ignition on signal is not supplied during movement of the vehicle due to a failure in the ignition sensor, when the engine speed signal or the vehicle velocity signal is above the predetermined value, the vehicle is regarded as being in the running state and operation of the electric motor is continued to apply the steering assist force to the steering system. With this arrangement, a good and stable steering feel can be obtained during movement of the vehicle.

Abstract: An electric power steering apparatus for a vehicle includes a fail-safe circuit for, on the basis of an engine running-state signal from an engine running-state sensor, enabling an electric motor to be driven by a motor drive unit so that a steering assist force from the electric motor is applied to the steering system of a vehicle. The fail-safe circuit, when the vehicle velocity detected by a vehicle velocity sensor is above a predetermined value, enables the electric motor to be driven by the motor drive unit even if the engine running-state sensor fails to detect the running state of the engine. Thus, even when a failure arises in the engine running-state sensor during movement of the vehicle, the motor can continue application of the steering assist force to the steering system. The electric power steering apparatus can always provide a good and stable steering feel as long as the vehicle is running even though the running state of the engine is not detected.

Abstract: A system and method for enabling an abrupt bias fault in a vehicle motion sensor (24), such as a yaw rate sensor or a lateral acceleration sensor to be both quickly and accurately diagnosed. When a potential fault is first indicated, it is signaled as true only if the vehicle is in a stable state and vehicle vibration is ruled out as a cause of abrupt signal change. Processing of signals is conducted by microprocessor.

Abstract: A system for controlling steering of a vehicle, including a steering unit having an electric motor which steers driven wheels of the vehicle, a first steering control unit (EPS ECU 76) for controlling the actuator, a CCD camera for detecting a condition of a lane on a road on which the vehicle travels, a steering assist torque determining unit for determining a steering assist torque necessary for holding a positional relationship between the vehicle and the lane condition, a torque sensor for detecting a steering torque manually applied to the steering unit by the driver, second steering control unit for calculating a torque command to be output to the first steering control unit based on the steering assist torque calculated by the steering assist torque calculating unit and the detected steering torque to control the motor such that the torque command decreases.

Abstract: The invention relates to a safety system having electrical consumers (18a, 18b) which are supplied with electrical energy in normal operation from an electrical energy source (2, 4, 6). The safety system includes an electrical energy store (14a, 14b) which supplies the electrical consumers (18a, 18b) with electrical energy when the instantaneous operating voltage at the energy source (2, 4, 6) drops below a limit value. The rated voltage of the energy store (14a, 14b) is less than the rated voltage of the electrical energy source (2, 4, 6) and the electrical energy store (14a, 14b) is connected to the electrical energy source (2, 4, 6) via a switchover element (16a, 16b) which assumes the function of a diode. The switchover element (16a, 16b) ensures that a switchover from normal operation to an emergency operation takes place automatically and that, during normal operation, the electrical energy store (14a, 14b) is not charged unintentionally by the electrical energy source (6).

Abstract: A steering apparatus for a vehicle comprising a reaction force control means for controlling an increase and decrease in a reaction force to be applied to a steering operating means on the basis of a reaction force instruction signal, a motor for applying the reaction force to a steering operating means with control of the reaction force control means, means for detecting an overload state of the motor, means for notifying a reaction force instruction means of the overload state when the overload state is detected, and a reaction force instruction means for decreasing to correct the reaction force instruction signal in a predetermined ratio when receiving the notification of the overload state from the reaction force control means.

Abstract: A drive system for utility vehicles, in particular for agricultural or industrial tractors, includes a generator driven by an internal combustion engine, a drive axle with wheels driven by associated electric motors which are powered by the generator, a steerable axle with wheels which are steerable together or individually by steering actuators, and manual operating control devices for vehicle operating functions such as steering and vehicle. The drive system includes a process computer which includes parallel and independently operating function modules for controlling high priority vehicle functions, such as steering, as well as function modules for low priority vehicle functions, such as speed input. The process computer transmits target value signals for actuator, such as electric wheel drive motors and steering actuators, in the form of a combined message communicated over a system bus. Information is exchanged between the function modules internally within the processor.

Abstract: An electric power steering apparatus having a control unit for controlling a motor for applying an assist torque to a steering system on the basis of a steering torque of the steering system. The control unit has a drive signal fading part for generating a drive current signal on the basis of a deviation signal expressing the deviation between a target current set in correspondence with a steering torque and a detected motor current detected by a motor current detector and gradually decreasing a drive current value with time to zero when a fadeout request signal is supplied to it. Thus in an electric power steering apparatus constructed to gradually decrease a steering assist force being supplied from a motor when an ignition switch is turned off, even if an error arises in a detected motor current value as a result of a fall in the voltage of a battery power supply, the steering assist force can be decreased correctly.

Abstract: A yaw-rate-sensor's anomaly detecting apparatus of the invention comprises a road-surface-condition determining device for determining a road surface condition and a yaw-rate-sensor's anomaly determining device for determining that a yaw rate sensor is abnormal, when a change amount of yaw rate outputted from the yaw rate sensor exceeds an anomaly determination threshold, wherein the yaw-rate-sensor's anomaly determining device sets one of different anomaly determination thresholds varying according to determination results by the road-surface-condition determining device. This can suppress erroneous determination of anomaly of the yaw rate sensor due to running on a bad road.

Abstract: According to the invention, there is provided is a vehicle steering system which can improve the resistance of a vehicle against external disturbances such as crosswind, and can prevent the operability of the steering system from being seriously affected by a failure in a part of the system related to the generation of steering reaction such as a lateral acceleration sensor, a yaw rate sensor or a reaction control unit. Because the assisting steering torque continues to be produced even when a failure has occurred in a part related to the generation of steering reaction. Therefore, a fail-safe feature can be obtained, and unnecessary loss of the operability of the steering system can be avoided. By reducing the assisting steering torque from the normal level, which is effective when the sensors are operating normally, at such a time, the driveability of the steering system similar to that under the normal condition can be ensured.