Jtekt Corporation

Toyota Jidosha Kabushiki Kaisha

Toyoda Koki Kabushiki Kaisha

Hirozumi Eki

Terutaka Tamaizumi

Masayuki Kita

Isao Namikawa

Jun Hasegawa

Hidenori Itamoto

Akihiko Nishimura

Gempei Nakasone

Takahiro Kojo

Hiroshi Suzuki

Masatoshi Nakatsu

Junji Kawamuro

Kazumasa Kodama

Michiyuki Sugiyama

Akira Ito

Satoru Mikamo

Shinya Aono

Tetsuya Nozawa

Kenji Nishimura

Provided is an electric power steering system that achieves a more appropriate steering feel. An ECU of the electric power steering system calculates a basic assist component and a target pinion angle based on at least steering torque. The ECU calculates a correction component for the basic assist component through feedback control in which an actual pinion angle is caused to match the target pinion angle. The ECU calculates an assist command value by adding the correction component to the basic assist component. The ECU corrects a hysteresis controlled variable and a viscosity component according to the rate of change (gradient) in a spring component with respect to a change in absolute value of the target pinion angle. Specifically, the ECU multiplies the hysteresis controlled variable and the viscosity component by gains that have a larger value as the rate of change in spring component increases.

Electric power steering system

An end determination unit determines that a steering apparatus is in an end touching state when an angle deviation, which is a difference between an actual turning angle and a target turning angle, exceeds a threshold. This angle deviation exceeds the threshold before a large axial force is generated in a steering shaft. Accordingly, is it possible to determine that the steering apparatus is in the end touching state more quickly.

Electric power steering apparatus

A control device in an electric power steering device calculates a first assist component based on steering torque and a vehicle speed. The control device also calculates a compensation component associated with an reverse input and calculates a steered angle command value based on an addition value of the compensation component and basic drive torque that is an addition value of the steering torque and the first assist component, produces a second assist component by performing steered angle feedback control that causes the steered angle of a vehicle to follow the steered angle command value. The control device controls drive of a motor based on an assist command value that is an addition value of the first assist component and the second assist component.

Electric power steering device

There is provided an electric power steering system that makes it possible to improve the driver's steering feel, and that includes a controller that controls driving of a motor. The controller computes a first assist component based on a steering torque. The controller computes a torque command value based on a basic drive torque that is the sum of the steering torque and the first assist component, and computes an assist compensation component through feedback control based on the torque command value. The controller computes a steered angle command value based on a value obtained by adding the assist compensation component to the basic drive torque, and computes a second assist component through feedback control based on the steered angle command value. The controller controls driving of the motor based on an assist command value that is the sum of the first assist component and the second assist component.

When only one of sensor signals generated by the plural systems and output from a torque sensor is normal, a control variable restriction processing part performs an assist restricting process for setting an upper limit value and a lower limit value of a basic assist control variable in accordance with at least one of the lateral acceleration, the steering angle, the steering speed, or the yaw rate.

Electronic power steering apparatus

In the vehicle power steering system, a first assist torque component is computed based on a steering torque and a vehicle speed. A target steered angle is computed based on the first assist torque component and the steering torque, and a second assist torque component is set based on the target steered angle and an actual steered angle. Then, the vehicle power steering system assists a steering operation by applying an assist torque Tas corresponding to the first assist torque component and the second assist torque component. Further, an ideal steered angle at which a vehicle is able to keep travelling in a lane is set based on image information on the lane captured by a camera, and a correction value is computed based on the deviation between the ideal steered angle and the actual steered angle. Then, the target steered angle is corrected by the correction value.

Vehicle power steering system

In an electric power steering system, a vehicle reactive force model computes a correction spring reactive torque in such a manner that an elasticity component included in a steering reactive force is increased with an increase in a lateral acceleration. As the lateral acceleration increases, an increase in a basic drive torque is suppressed by a larger amount. By an amount by which the magnitude of the basic drive torque is suppressed, a target pinion angle computed by a target pinion angle computing unit decreases and a correction component for a basic assist component is decreased. A steering assist force is decreased, and a steering reactive force is increased with a decrease in the steering assist force. Thus, it is possible to obtain an appropriate steering reactive force based on the magnitude of the lateral acceleration.

A controller of an electric power steering system includes: a basic assist component computing unit () that computes a first assist component (Ta*) based on a steering torque (Th); a steered angle command value computing unit () that computes a steered angle command value (&#x3b8;t*) based on the sum of the steering torque (Th) and the first assist component (Ta*); and a steered angle feedback controller () that computes a second assist component (Ta*) through feedback control on an actual steered angle (&#x3b8;t). The controller further includes: a correction component computing unit () that computes a correction component (Tc*) based on a steering angle (&#x3b8;s); and an assist command value computing unit () that computes an assist command value (Ta*) by subtracting the correction component (Tc*) from the sum of the first assist component (Ta*) and the second assist component (Ta*).

A zero point change model executes banked road correspondence control when a vehicle travels on a banked road. By this control, a target turning angle when the total torque is zero can be changed from a neutral turning angle to a lower side of an inclined road surface. Thus, a steering angle of a steering wheel according to a banked road can be realized even if the driver does not apply steering torque during traveling on a banked road. Accordingly, the driver can obtain a suitable steering feeling when traveling on a banked road while achieving the target turning angle according to the total torque.

An ECU controls the operation of an EPS actuator in order to periodically apply instantaneous motor torque to a steering system when assist continuation control is executed using a sensor signal (residual sensor signal) that is output by a sensor element in which an abnormality has not been detected, regardless of the application of an assist force. The ECU also detects an abnormality in the residual sensor signal based on whether the application of instantaneous motor torque is reflected in the residual sensor signal, which is the basis of the assist continuation control.

Electric power steering device and sensor abnormality detection device

An electric power steering system includes short-circuit determination means for determining whether a short-circuit between an energization failure phase and one of the two phases other than the energization failure phase has occurred while assist force is being generated using the two phases other than the energization failure phase as energization phases. When the short-circuit determination means determines that the short-circuit has occurred, generation of the assist force is stopped.

A target pinion angle computation unit computes a target pinion angle on the basis of a basic assist component and a steering torque, and computes the target pinion angle so as to rapidly increase a steering reaction force when it is determined based on the target pinion angle that a rack shaft of a rack-and-pinion mechanism reaches a position near a limit of a movable range of the rack shaft. In an EPS, a correction component for the basic assist component, which is necessary to increase the steering reaction force rapidly, is computed through execution of PID control for causing an actual pinion angle to coincide with the target pinion angle. Because the correction component is added to the basic assist component, the steering reaction force is increased rapidly when the rack shaft reaches the position near the limit of the movable range.

An assisting command value calculating unit calculates a first assisting factor on the basis of the value of a torque differential control volume added to a basic assist control volume based on a steering torque value, while increasing or decreasing, on the basis of an assisting gradient, the torque differential control volume based on a torque differential value. The pinion angle F/B control unit calculates a pinion angle command value, capable of being converted to a steering angle of the steering wheel, on the basis of the steering torque and the first assisting factor, and executes rotational angle feedback control. The assisting command value calculating unit calculates an assisting command value on the basis of the value of a second assisting factor, calculated by the pinion angle F/B control unit, added to the first assisting factor.

An electric power steering system includes a motor control device that controls, based on an assist command value, driving of a motor that gives an assist torque to a steering mechanism. The motor control device computes a first assist component based on a steering torque and a vehicle speed. A steered-angle command value is computed based on the steering torque and the first assist component, and a second assist component is computed by performing a feedback control that matches the steered angle with the steered-angle command value. The motor control device adds the second assist component to the first assist component so as to compute an assist command value. The motor control device includes a road information compensation portion that decreases an absolute value of the second assist component included in the assist command value when a skid is detected by a vehicle state detecting portion.

A current command value computing section includes an integration control computing section. Based on an integration of the steering torque &#x3c4;, the integration control computing section computes a steering torque integration control amount Iint*, which is a compensation component for increasing the assist force. The integration control computing section functions as a determining device that determines whether the vehicle is traveling forward in a straight line. When the determining device determines that the vehicle is traveling forward in a straight line, the integration control computing section outputs the steering torque integration control amount Iint* to an adder. The current command value computing section superimposes the steering torque integration control amount Iint* on a basic assist control amount Ias* computed by a basic assist control section, and outputs the obtained value, as a current command value Iq* corresponding to a target assist force, to an output section.

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Okazaki, Japan

Hirozumi Eki