Jtekt Corporation

Koyo Seiko Company, Ltd.

Toyoda Koki Kabushiki Kaisha

Favess Co., Ltd.

Nissan Motor Company Limited

Shinya Aono

Terutaka Tamaizumi

Masayuki Kita

Jun Hasegawa

Yoshinobu Shimizu

Akihiko Nishimura

Akira Nambu

Akihiro Nishiyama

Shingo Maeda

Takahiro Toko

Hirozumi Eki

Takayuki Ohta

Takanobu Takamatsu

Gempei Nakasone

Yuuichi Fukuyama

Tetsuya Nozawa

Tomohiko Usui

Takashi Sekiguchi

Tomoyuki Yamauchi

The actuator control device includes an assist control circuit for calculating a first assist component and an automatic steering control circuit for calculating a second assist component. The automatic steering control circuit is allowed to calculate the second assist component while a steering torque is less than a first threshold value. The automatic steering control circuit calculates the second assist component by performing PID control that uses an integral term obtained on the basis of an angle deviation. When the steering torque is less than the first threshold value but not less than a second threshold value, the automatic steering control circuit limits the integral term in such a manner that it is harder for the integral term to increase while the steering torque is not less than the second threshold value than while the steering torque is less than the second threshold value.

Actuator control device

An electric power steering apparatus includes a motor for applying assist torque to a vehicle steering mechanism and a controller, which controls driving of the motor to cause the assist torque to follow an assist command value. The controller calculates a basic assist command value based on steering torque applied to the steering mechanism and corrects the basic assist command value using a correction value, thereby setting the assist command value. If the steering torque has an absolute value greater than a threshold value when the vehicle is in a straight-line traveling state, the controller sets the correction value such that the absolute value of the steering torque is reduced. If the steering torque has an absolute value less than the threshold value when the vehicle is in a straight-line traveling state, the controller sets the correction value such that the absolute value of the assist command value is reduced.

Electric power steering apparatus

An electric power steering apparatus is provided which can suppress the difference in steering feel between before and after it is allowed to compute an absolute steering angle and which can improve the steering feel. A basic assist control unit sets a basic assist current value. An assist gain setting unit sets assist gain. The assist gain is fixed to a lower limit value less than one before it is allowed to compute the absolute steering angle, and is gradually increased from the lower limit value to one and is then fixed to one after it is allowed to compute the absolute steering angle. An assist gain multiplication unit corrects the basic assist current value by multiplying the basic assist current value by the assist gain.

An EPS includes a first rack and pinion mechanism that converts rotation of a pinion shaft due to a steering operation, to reciprocating motion of a rack shaft; and a steering force assist device that applies a motor torque of a motor as an assist force by using a second rack and pinion mechanism; and an ECU that controls an operation of the steering force assist device. Rack teeth of the rack shaft constituting the first rack and pinion mechanism are formed so that a steering gear ratio is changed depending on a steering angle. The ECU computes a motor neutral point by subtracting a conversion value from a motor angle detection value. The conversion value is computed based on a steering angle detection value by referring to a conversion map that is set taking into account the steering gear ratio corresponding to the steering angle.

Electric power steering system

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.

Electric power steering device and method for controlling the same

A steering torque shift control amount calculation unit () calculates the steering torque shift control amount (&#x3b5;ts) by multiplying the basic shift amount (&#x3b5;ts_b) used as the basic compensation component by the transition coefficient (Kss). Then, the steering torque shift control amount (&#x3b5;ts) is subjected to the low-pass filter process in an abrupt change prevention processing unit (). An abrupt change prevention processing unit () is provided in the steering torque shift control amount calculation unit (). The transition coefficient (Kss) is subjected to the low-pass filter process in the abrupt change prevention processing unit (). The cutoff frequency of the low-pass filter that forms the abrupt change prevention processing unit () is set to a value lower than the cutoff frequency of the low-pass filter that forms the abrupt change prevention processing unit () that executes the low-pass filter process on the torque shift control amount (&#x3b5;ts).

An electric power steering (EPS) apparatusincludes a motor, an EPS actuator, a torque sensor, and an ECU. The EPS actuatoruses the motoras a drive source to apply assist force to a steering system, thereby assisting a steering operation. The torque sensordetects a steering torque &#x3c4; of the steering system. The ECUcontrols the operation of the EPS actuator. Based on the steering torque &#x3c4; detected by the torque sensor, the ECUcomputes a basic shift amount &#x3b5;ts_b of the assist force applied to the steering system. The ECUdetermines which one of returning, holding, and turning is the state of the steering operation. When the state of the steering operation is returning or holding, the ECUexecutes compensation control for correcting the steering torque &#x3c4;, which is used in the computation of the basic shift amount &#x3b5;ts_b of the assist force, thereby increasing the assist force applied to the steering system. The ECUsubjects the steering torque shift control amount &#x3b5;ts to a filtering process using a low pass filter, thereby inhibiting the steering torque shift control amount &#x3b5;ts from sharply changing. When the state of the steering operation is turning, the ECUchanges a filter constant of the low pass filter so as to reduce the filtering effect.

In an electric power steering apparatus, steering torque of a steering wheel is detected by a torque sensor, and a motorfor generating steering assist power is controlled so that the steering assist power is generated according to a basic assist torque corresponding to the detected steering torque. A correspondence relationship between the steering torque and the basic assist torque is set such that an assist gradient that is a rate of change of the basic assist torque to the steering torque varies according to variation of the steering torque. A correction amount of an output of the motorvaries according to the variation of the assist gradient.

An electric power steering apparatus transmits a driving force of an electric motor to a steering mechanism for steering assist. The apparatus includes a torque sensor which detects a steering wheel torque; a basic assist characteristic determining section which determines a basic assist characteristic defining a basic characteristic of a motor driving target value for the steering torque; a motor driving target value determining section which determines the motor driving target value for the steering torque in accordance with a modified assist characteristic prepared by shifting the basic assist characteristic along a steering torque coordinate axis; a shift amount determining section which determines the amount of the shift from the basic assist characteristic to the modified assist characteristic on the basis of the steering torque; and a motor driving section which drives the electric motor on the basis of the motor driving target value.

The present invention provides an electric power steering device enabled to compensate for the influence of the inertia of a steering-assisting-force generating motor on steering with accurate timing even when a steering direction is reversed at high speed. Based on steering torque and a rotation angular speed of a steering-assisting-force generating motor, a steering angular acceleration correspondence value is obtained. The device has means for regulating a gain, which is multiplied to a change acceleration of the steering torque. The motor is controlled so that the steering assisting force is corrected according to a motor output correction value obtained on the basis of the relation between the motor output correction value and the steering angular acceleration correspondence value, which is preliminarily determined and stored in such a way as to compensate for the influence of the inertia on steering, and the obtained steering angular acceleration correspondence value.

An electric power steering apparatus has a motor controlled so as to generate steering assist power according to the steering torque required to operate a steering wheel. As a result of correction of the output of the motor in accordance with a value correlating with the rotation angular velocity correspondence value of the steering wheel, in the frequency response characteristic represented by the steering frequency of the steering wheel and the amplitude ratio of the steering torque relative to the steering angle of the steering wheel, the amplitude ratio is set within a setting range, at least within the steering frequency range when a person operates the steering wheel. As a result of correction of the output of the motor in accordance with a value directly correlating with the change velocity correspondence value of the steering torque, in the frequency response characteristic represented by the frequency of the disturbance torque input from the road surface to the steering system via vehicle wheels and the amplitude ratio of the steering torque relative to the disturbance torque, the amplitude ratio becomes smaller at the resonance frequency.

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Okazaki, Japan

Shinya Aono