JP2010076594A - Electric power steering system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To make it easy to return a steering wheel to a neutral position both in acceleration and deceleration. <P>SOLUTION: This electric power steering system 1 is equipped with a steering wheel returning control part 13 to control the steering wheel so as to return to the neutral position through an assist motor 9 by detecting a steering angle by a steering angle sensor 6. The steering wheel returning control part 13 increases controlled variable to return the steering wheel to the neutral position the more, the larger acceleration of a vehicle is and increases the controlled variable to return the steering wheel to the neutral position the more, the larger deceleration of the vehicle is. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an electric power steering apparatus including a handle return control unit.

  The vehicle steering mechanism is designed so that a self-aligning torque is applied to the straight-ahead steering state in response to the reaction force from the road surface.For example, the driver turns the steering wheel while driving, When released, the steering wheel returns to the neutral position.

Further, in a vehicle equipped with an electric power steering device, a target current (target steering assist amount) for a steering assist motor (hereinafter referred to as an assist motor) is set to a steering angle so as to compensate for excessive or insufficient self-aligning torque. There is known one that corrects according to the above (for example, see Patent Document 1).
JP 2005-271877 A

However, since the lateral force is reduced when the vehicle is accelerated or decelerated, the force to return the steering wheel to the neutral position (that is, self-aligning torque) is reduced, making it difficult to return, and the driver is also difficult to steer.
Accordingly, the present invention provides an electric power steering device that can easily return the steering wheel to the neutral position during acceleration and deceleration.

The electric power steering apparatus according to the present invention employs the following means in order to solve the above problems.
The invention according to claim 1 detects a steering angle, and controls a steering wheel return control unit (for example, described later) that controls the steering wheel to return to a neutral position via an actuator (for example, an assist motor 9 in an embodiment described later). In the electric power steering apparatus (for example, the electric power steering apparatus 1 in the embodiment described later) having the steering wheel return control unit 13) in the embodiment, the steering wheel return control unit neutralizes the steering wheel as the vehicle acceleration increases. An electric power steering apparatus characterized by increasing a control amount to be returned to a position.

  The invention according to claim 2 detects a steering angle, and controls a steering wheel return control unit (for example, described later) that controls the steering wheel to return to a neutral position via an actuator (for example, an assist motor 9 in an embodiment described later). In an electric power steering apparatus (for example, an electric power steering apparatus 1 in an embodiment to be described later) including the steering wheel return control unit 13) in the embodiment to be performed, the steering wheel return control unit causes the steering wheel to move as the vehicle deceleration increases. An electric power steering apparatus characterized by increasing a control amount to be returned to a neutral position.

  According to the first aspect of the present invention, the amount of control for returning the steering wheel to the neutral position when the vehicle is accelerated is increased. Therefore, the steering wheel can easily return to the neutral position even during acceleration, and the driver can easily steer.

  According to the second aspect of the invention, the amount of control for returning the steering wheel to the neutral position when the vehicle is decelerated is increased, so that the steering wheel can easily return to the neutral position even during deceleration, and the driver can easily steer.

  Embodiments of an electric power steering apparatus according to the present invention will be described below with reference to the drawings of FIGS.

As shown in the block diagram of FIG. 1, an electric power steering apparatus 1 for a vehicle includes an assist motor (actuator) 9 that generates steering assist torque, a motor rotation speed sensor 2 that detects the rotation speed of the assist motor 9, and a vehicle. A vehicle speed sensor 3 for detecting the vehicle speed (vehicle speed), a yaw rate sensor 4 for detecting a yaw rate generated in the vehicle, a steering torque sensor 5 for detecting a steering torque applied to a steering shaft (not shown), and a steering wheel ( The steering angle sensor 6 detects a steering angle (not shown), a drive circuit 8 that drives an assist motor 9, and an electronic control unit (hereinafter abbreviated as ECU) 10.
The motor rotation speed sensor 2, the vehicle speed sensor 3, the yaw rate sensor 4, the steering torque sensor 5, and the steering angle sensor 6 each output an output signal corresponding to the detected value to the ECU 10.

The ECU 10 includes an EPS basic control unit 11, a reaction force control unit 12, and a handle return control unit 13.
The EPS basic control unit 11 calculates a basic control amount Ib of the assist motor 9 based on output signals of the motor rotation speed sensor 2, the vehicle speed sensor 3, and the steering torque sensor 5. Since the calculation method of the basic control amount Ib is the same as that of a known electric power steering apparatus, detailed description thereof is omitted. However, as a general rule, the basic control amount Ib increases as the steering torque increases, and the rotation speed of the assist motor 9 increases. The basic control amount Ib is set to be smaller as the steering speed is increased (in other words, as the steering angular velocity is larger), and the basic control amount Ib is set to be smaller as the vehicle speed is increased.

  The reaction force control unit 12 calculates the reaction force correction amount Iy based on the output signal of the yaw rate sensor 4. The reaction force correction amount Iy is a reaction force component that generates torque in a direction to cancel the yaw rate when the yaw rate is generated, for example, when the vehicle is turning, and the reaction force correction amount Iy is increased as the yaw rate increases. It is set to be large.

  The steering wheel return control unit 13 calculates a steering wheel return control amount Ih based on output signals of the motor rotation speed sensor 2, the vehicle speed sensor 3, the steering torque sensor 5, and the steering angle sensor 6. The steering wheel return control amount Ih compensates for excessive or insufficient self-aligning torque. A method for calculating the handle return control amount Ih will be described in detail later.

  The ECU 10 subtracts the reaction force correction amount Iy calculated by the reaction force control unit 12 and the handle return control amount Ih calculated by the handle return control unit 13 from the basic control amount Ib calculated by the EPS basic control unit 11. Thus, the target current Io of the assist motor 9 is obtained, and this target current Io is output to the motor drive circuit 8. In the motor drive circuit 8, feedback control is performed so that the actual current of the assist motor 9 matches the target current Io.

Next, the handle return control amount calculation process executed in the handle return control unit 13 will be described with reference to the drawing of FIG.
First, the steering wheel return control unit 13 calculates the steering wheel return base control amount Ihb based on the output signal (steering angle) of the steering angle sensor 6 and the output signal (vehicle speed) of the vehicle speed sensor 3. More specifically, the steering angle offset amount corresponding to the vehicle speed is calculated with reference to the steering angle offset map 20 based on the output signal of the vehicle speed sensor 3. Further, the high-frequency component is removed from the output signal of the steering angle sensor 6 by the low-pass filter 21, and the steering angle offset amount is subtracted from the steering angle after the low-pass filter processing to calculate the steering angle STRoff after the offset. Further, with reference to the steering wheel return base control amount map 22, the steering wheel return base control amount Ihb corresponding to the steering angle STRoff after the offset is calculated.

  In the steering angle offset map 20, the steering angle offset amount is “0” until the vehicle speed reaches the first predetermined value, and the vehicle speed increases from the first predetermined value to the second predetermined value. Accordingly, the steering angle offset amount gradually increases, and when the vehicle speed becomes equal to or higher than the second predetermined value, the steering angle offset amount at the second predetermined value is maintained.

In the steering wheel return base control amount map 22, the steering wheel return base control amount Ihb is “0” until the steering angle after offset reaches the first predetermined value, and the steering angle after offset is the first predetermined angle. From the value to the second predetermined value, the steering wheel return base control amount Ihb gradually increases as the steering angle after offset increases, and when the steering angle after offset becomes equal to or greater than the second predetermined value, the second predetermined value is reached. The steering wheel return base control amount Ihb at this time is set to be maintained.
Therefore, the steering wheel return base control amount Ihb is basically set to a larger value as the steering angle increases.

  Further, the steering wheel return control unit 13 calculates the steering angular speed ratio Rm based on the output signal (motor speed) of the motor speed sensor 2 and the output signal (vehicle speed) of the vehicle speed sensor 3. More specifically, the steering angular velocity offset amount corresponding to the vehicle speed is calculated based on the output signal of the vehicle speed sensor 3 with reference to the steering angular velocity offset map 23, and the steering angular velocity offset amount is subtracted from the output signal of the motor rotation speed sensor 2. Thus, the motor rotation speed Mvo after the offset is calculated. Further, the acceleration / deceleration of the vehicle is calculated by time-differentiating the output signal of the motor rotation speed sensor 2 in the acceleration / deceleration calculation unit 30, and the first acceleration / deceleration ratio map 31 is referred to according to the acceleration or deceleration. The first acceleration / deceleration ratio Ra1 is calculated. Then, the corrected motor rotational speed Mv is calculated by multiplying the motor rotational speed Mvo after the offset by the first acceleration / deceleration ratio Ra1, and the steering angular speed ratio Rm corresponding to the corrected motor rotational speed Mv is obtained by referring to the steering angular speed ratio map 24. Is calculated.

  In the steering angular velocity offset map 23, the steering angular velocity offset amount is “0” until the vehicle speed reaches the first predetermined value, and the vehicle speed increases from the first predetermined value to the second predetermined value. Accordingly, the steering angular speed offset amount gradually increases, and when the vehicle speed becomes equal to or higher than the second predetermined value, the steering angular speed offset amount at the second predetermined value is maintained.

  The first acceleration / deceleration ratio map 31 is “1” when the acceleration and deceleration are 0, and the first acceleration / deceleration ratio Ra1 gradually increases as the deceleration increases, and when the deceleration becomes a predetermined value or more. The first acceleration / deceleration ratio Ra1 is set to be maintained at the predetermined value, and the first acceleration / deceleration ratio Ra1 gradually increases as the acceleration increases, and when the acceleration reaches a predetermined value or more, the predetermined acceleration / deceleration ratio Ra1 is set. The first acceleration / deceleration ratio Ra1 at the time of the value is set to be maintained. That is, when acceleration or deceleration is detected, the first acceleration / deceleration ratio Ra1 is a value greater than 1.

  Therefore, the rudder angular speed ratio Rm is basically set smaller as the rotation speed of the assist motor 9 is larger (in other words, as the steering speed is larger). This is to reduce the steering wheel return control amount Ih by estimating that the driver's steering intention is high when the rotational speed of the assist motor 9 is large. Further, the larger the acceleration and deceleration, the larger the steering angular speed ratio Rm is set.

  In this embodiment, the corrected motor rotational speed Mv is calculated by multiplying the motor rotational speed Mvo after the offset by the first acceleration / deceleration ratio Ra1, and the steering angular speed ratio Rm is calculated based on the corrected motor rotational speed Mv. However, the steering angular speed ratio Rm can be calculated based on the motor rotational speed Mvo after offset without multiplying the first acceleration / deceleration ratio Ra1 when calculating the steering angular speed ratio.

  Further, the steering wheel return control unit 13 refers to the second acceleration / deceleration ratio map 32 based on the acceleration or deceleration calculated by the acceleration / deceleration calculation unit 30, and the second acceleration / deceleration ratio Ra2 corresponding to the acceleration or deceleration. Is calculated.

  The second acceleration / deceleration ratio map 32 is “1” when the acceleration and deceleration are 0, and the second acceleration / deceleration ratio Ra2 gradually increases as the deceleration increases, and when the deceleration becomes a predetermined value or more. The second acceleration / deceleration ratio Ra2 is set to be maintained at the predetermined value, and the second acceleration / deceleration ratio Ra2 is gradually increased as the acceleration increases. The second acceleration / deceleration ratio Ra2 when the value is set is maintained. That is, when acceleration or deceleration is detected, the second acceleration / deceleration ratio Ra2 is a value greater than one.

  The steering wheel return control unit 13 calculates the vehicle speed ratio Rv with reference to the vehicle speed ratio map 26 based on the output signal (vehicle speed) of the vehicle speed sensor 3. The vehicle speed ratio map 26 shows that the vehicle speed ratio Rv is “0” when the vehicle speed is “0”, and the vehicle speed ratio Rv gradually increases as the vehicle speed increases until the vehicle speed reaches a predetermined speed from “0”. When the vehicle speed becomes equal to or higher than the predetermined value, the vehicle speed ratio Rv at the predetermined value is set to be maintained.

  Further, the steering wheel return control unit 13 calculates the torque ratio Rt with reference to the torque ratio map 27 based on the output signal (steering torque) of the steering torque sensor 5. The torque ratio map 27 indicates that the torque ratio Rt is a predetermined constant value until the steering torque reaches a first predetermined value, and when the steering torque exceeds the first predetermined value, the torque ratio Rt increases as the steering torque increases. Is set to gradually decrease. This is because when the steering torque is large, the steering wheel return control amount Ih is reduced by giving priority to the driver's steering intention.

  In addition, the steering wheel return control unit 13 uses the steering wheel steering state based on the output signal (steering angle) of the steering angle sensor 6 and the output signal (motor rotation number) of the motor rotation number sensor 2 in the switchback determination unit 25. Is in a state of rotating in a direction away from the neutral position (hereinafter referred to as a cutting state) or in a state of rotating in a direction of returning to the neutral position (hereinafter referred to as a returning state) To do. More specifically, the direction of the steering angle from the output signal of the steering angle sensor 6 (whether it is rotated clockwise or counterclockwise from the neutral position), and the motor rotation speed sensor If the direction of the steering speed (steering angular speed) calculated based on the output signal 2 (clockwise direction or counterclockwise direction) is the same direction, it is determined that the vehicle is in the cut state and is in a different direction. In this case, it is determined that the state is the return state. Then, the switchback determination unit 25 outputs “0” as the switchback determination value G when determining that the switch is in the cut state, and “1” as the switchback determination value G when determining that the switch is in the return state. Is output.

The steering wheel return control unit 13 multiplies the steering wheel return base control amount Ihb by the steering angular speed ratio Rm, the second acceleration / deceleration ratio Ra2, the vehicle speed ratio Rv, the torque ratio Rt, and the switchback determination value G, and returns the product to the steering wheel return. Output as control amount Ih.
Therefore, when the steering wheel is in the off state, the steering wheel return control amount Ih output from the steering wheel return control unit 13 is “0”. That is, substantial steering wheel return control is performed only when the steering wheel is in the return state.

According to the electric power steering apparatus 1 configured as described above, the second acceleration / deceleration ratio Ra2 is multiplied when the steering wheel return control amount Ih is obtained. As described above, the second acceleration / deceleration ratio Ra2 is accelerated and decelerated. Since the value is sometimes larger than 1, the steering wheel return control amount Ih at the time of acceleration and deceleration can be made larger than that at the constant speed. As a result, the steering wheel return control amount Ih can be increased during acceleration and deceleration when the self-aligning torque from the tire is reduced, so that the steering wheel can easily return to the neutral position and the driver can easily steer.
Moreover, since the second acceleration / deceleration ratio Ra2 increases as the acceleration and deceleration increase, the steering wheel easily returns to the neutral position as the acceleration and deceleration increase.

[Other Examples]
The present invention is not limited to the embodiment described above.
For example, the second acceleration / deceleration ratio map shown in FIG. 2 is an example, and the present invention is not limited to this.

It is a block diagram in the Example of the electric power steering device which concerns on this invention. It is a block diagram of the handle return control part in the embodiment.

Explanation of symbols

1 Electric power steering device 9 Assist motor (actuator)
13 Handle return control unit

Claims (2)

In the electric power steering apparatus including a steering wheel return control unit that detects the steering angle and performs control to return the steering wheel to the neutral position via the actuator.
The electric power steering apparatus according to claim 1, wherein the steering wheel return control unit increases a control amount for returning the steering wheel to a neutral position as the acceleration of the vehicle increases. In the electric power steering apparatus including a steering wheel return control unit that detects the steering angle and performs control to return the steering wheel to the neutral position via the actuator.
The electric power steering apparatus, wherein the steering wheel return control unit increases a control amount for returning the steering wheel to a neutral position as the deceleration of the vehicle increases.

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