JP2008265524A - Control device for electric power steering device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a control device for an electric power steering device easy to be tuned and capable of stabilizing vehicle action when moving a vehicle backward. <P>SOLUTION: The control device for an electric power steering device comprises a steering auxiliary command value computing section for computing a steering auxiliary command value based on the steering torque of the vehicle, a current control section for computing a voltage command value based on the steering auxiliary command value, a motor driving section for driving a motor based on the voltage command value, and a SAT estimating means for obtaining a SAT estimation value based on the angular velocity and angular acceleration of the motor, the steering auxiliary command value and the steering torque. The SAT estimation value is given to the steering auxiliary command value so as to drive the motor, and assist force by the motor is given to a steering system. This control device for an electric power steering device is provided with a function for changing a gain of the SAT estimation value when moving the vehicle forward and backward. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a control device for an electric power steering device, and more particularly to an electric power steering device that can change a gain of a self-aligning torque (hereinafter referred to as “SAT”) feedback value when a vehicle moves forward and backward to improve stability. The present invention relates to an apparatus control device.

  An electric power steering device that applies an assisting force (steering assisting force) to a steering device of a vehicle by a rotational force of a motor is applied to a steering shaft or rack by a transmission mechanism such as a gear or a belt via a reduction gear. An auxiliary force (assist force) is applied to the shaft.

  A general configuration example of such an electric power steering apparatus will be described with reference to FIG. A column shaft 2 of the steering wheel (handle) 1 is coupled to a tie rod 6 of a steered wheel via a reduction gear 3, universal joints 4A and 4B, and a pinion rack mechanism 5. The column shaft 2 is provided with a torque sensor 10 that detects the steering torque of the steering wheel 1, and a motor 20 that assists the steering force of the steering wheel 1 is connected to the column shaft 2 via the reduction gear 3. Yes. Electric power is supplied from the battery 14 to the control unit 100 that controls the power steering device, and an ignition key signal is input via the ignition key 11. The steering torque T and the vehicle speed from the torque sensor 10 are input to the control unit 100. The vehicle speed V detected by the sensor 12 is input, the steering assist command value I of the assist command is calculated based on the steering torque T and the vehicle speed V, and supplied to the motor 20 based on the calculated steering assist command value I. Control the current.

  An example of the configuration of the control device of the electric power steering apparatus configured as described above will be described with reference to FIG.

  The steering torque T from the torque sensor 10 and the vehicle speed V from the vehicle speed sensor 12 are input to the steering assist command value calculation unit 111 constituting the torque system 110, and the steering assist command value Ia calculated by the steering assist command value calculation unit 111. Is phase-compensated by the phase compensator 112 and input to the adder 107A. Further, the steering torque T is input to the differentiating unit 113 constituting the torque system 110, and the steering torque Ta subjected to differential compensation is input to the adding unit 107A.

  A compensation signal CM2 is also input to the adding unit 107A, and a current command value calculating unit 101 that calculates a current command value Id corresponding to the number of phases of the motor 20 by the steering assist command value Ic that is the addition result of the adding unit 107A. Is input. The current command value Id is input to the subtraction unit 121 constituting the current control system 120, and the motor current Im detected by the motor current detection unit 125 is fed back to the subtraction unit 121. The current command value Id and the motor current The deviation from Im (= Id−Im) is input to the PI control unit 122 of proportional integral control, and the current command value subjected to PI control is input to the PWM control unit 123 of pulse width control to become the voltage command value Ve. The motor 20 is driven via the inverter 124 by the command value Ve.

A rotation sensor 21 such as a resolver is attached to the motor 20. An angular velocity calculation unit 102 that inputs a signal from the rotation sensor 21 calculates an angular velocity ω of the motor 20. The angular velocity ω is calculated by the angular acceleration calculation unit 103 and the convergence control. Input to the unit 104 and the SAT estimation unit 106. The convergence control unit 104 applies a brake to the operation of the steering wheel in order to improve the yaw convergence of the vehicle. The angular acceleration ω ^* calculated by the angular acceleration calculation unit 103 is input to the inertia compensation unit 105 and the SAT estimation unit 106, and the steering torque T and the steering assist command value Ib are also input to the SAT estimation unit 106. The inertia compensation unit 105 assists the force equivalent generated by the inertia of the steering system, and prevents deterioration of the inertial feeling or control responsiveness.

On the other hand, the SAT estimated value SAT ^* estimated by the SAT estimation unit 106 is fed back to the subtraction unit 107C, subtracted from the inertia signal N1 from the inertia compensation unit 105 by the subtraction unit 107C, and a compensation signal CM1 as a result of the subtraction is obtained. The data is input to the adding unit 107B. The convergence signal N2 from the convergence control unit 104 is also input to the addition unit 107B, and the compensation signal CM2 obtained by adding the compensation signal CM1 by the addition unit 107B is input to the addition unit 107A. The motor 20 is driven and controlled by the steering assist command value Ic compensated or corrected as described above.

Here, the state of the torque generated between the road surface and the steering will be described with reference to FIG. 5. When the driver steers the steering wheel, the steering torque T is generated, and the motor 20 generates the assist torque Tm according to the steering torque T. Is generated. As a result, the wheels are steered and SAT is generated as a reaction force. Further, at that time, a torque that becomes a steering steering resistance is generated by the inertia J and the static friction Fr of the motor 20, and considering the balance of these forces, an equation of motion such as the following equation (1) is obtained.

J ・ ω ^* + Fr ・ sign (ω) + SAT = Tm + T (1)

Here, when the above equation (1) is Laplace transformed with an initial value of zero and solved for SAT, the following equation (2) is obtained.

SAT (s) = Tm (s) + T (s)-J · ω ^* (s) + Fr · sign (ω (s)) (2)

As can be seen from the above equation (2), the inertia J and static friction Fr of the motor 20 are obtained in advance as constants, so that the SAT can be determined from the motor rotational angular velocity ω, rotational angular acceleration ω ^* , steering assist command value, and steering torque T. Can be estimated.
In addition, if the SAT information estimated by the SAT estimation unit 106 is fed back as it is, the steering becomes too heavy and the steering feeling cannot be improved. Therefore, as shown in FIG. 6, a Q filter having a gain for reducing the estimated SAT size to a necessary and sufficient value and a gain unit having a gain K1 sensitive to the vehicle speed V as shown in FIG. Only SAT information necessary and sufficient to improve the steering feeling is fed back as the SAT estimated value SAT ^* .

  In such an electric power steering apparatus, conventionally, system stability and sensitivity characteristics of road surface information and disturbance information are designed simultaneously by robust stabilization compensation (for example, Japanese Patent Laid-Open No. 8-290778 (patent) Literature 1)). However, in this control device, since the reaction force at the time of steering near the steering neutral point is small, it is difficult to accurately convey the road surface information to the driver due to the influence of friction, and between the steering angle and the steering force. It is difficult to make the hysteresis characteristic comparable to that of hydraulic power steering.

  As a control device that solves such a problem, that is, a device that can be tuned easily and obtain a safe and comfortable steering performance by performing signal processing such as road surface information and disturbance in the frequency domain, Japanese Patent Application Laid-Open No. 2002-369565 ( There exists what was disclosed by patent document 2).

The control device disclosed in Patent Document 2 includes a SAT feedback unit that inputs a motor rotation angular velocity, a motor rotation angular acceleration, a steering assist force, and a steering signal and performs SAT estimation or sensor measurement, and is obtained by the SAT feedback unit. The obtained SAT value is fed back to the steering assist command value through the feedback filter.
JP-A-8-290778 JP 2002-369565 A

  The device of Patent Document 2 feeds back the SAT value obtained by the SAT feedback unit to the steering assist command value through the feedback filter, and corrects the compensation amount according to the vehicle behavior when the vehicle moves forward. Handle operation can be performed. However, the apparatus disclosed in Patent Document 2 does not take into account that the vehicle moves backward (back), and there is a problem that the vehicle behavior becomes unstable when the vehicle moves backward.

  The present invention has been made under the circumstances as described above, and an object of the present invention is to provide a control device for an electric power steering device that is easy to tune and that has stable vehicle behavior even when the vehicle is in reverse. .

  The present invention provides a steering assist command value calculation unit that calculates a steering assist command value based on a steering torque of a vehicle, a current control unit that calculates a voltage command value based on the steering assist command value, and a voltage command value A motor driving unit for driving the motor based on the motor, and SAT estimation means for obtaining a SAT estimation value based on the angular velocity and acceleration of the motor, the steering assist command value, and the steering torque, and The present invention relates to a control device for an electric power steering apparatus configured to apply a steering assist command value to drive the motor and apply an assist force by the motor to a steering system. This is achieved by providing a function of changing the gain of the vehicle between when the vehicle moves forward and when the vehicle moves backward.

  The object of the present invention is to increase the gain of the SAT estimated value when the vehicle moves backward, or to change the gain of the SAT estimated value according to the reverse speed of the vehicle. Or by using SAT measurement means instead of the SAT estimation means.

  According to the control device for the electric power steering apparatus according to the present invention, the feedback amount of the SAT estimated value or the SAT value measured by the sensor is varied between when the vehicle moves forward and when the vehicle moves backward, and is given to the steering assist command value. Therefore, there are advantages that tuning is easy and the vehicle behavior is stable even when the vehicle is moving backward.

  In the control device for the electric power steering apparatus according to the present invention, the estimated SAT value or the SAT value measured by the sensor is variably applied to the steering assist command value when the vehicle is moving forward and backward. That is, when the vehicle is moving backward, the gain of the SAT feedback amount is increased compared to when the vehicle is moving forward. For this reason, the vehicle behavior is stabilized both when the vehicle moves forward and when the vehicle moves backward.

  Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows an example of the configuration of the present invention corresponding to FIG. 4. In the present invention, the SAT estimated value SAT ^* estimated by the SAT estimation unit 106 is passed through a gain unit 130 having a variable gain K2 to the subtraction unit 107C. You are typing. Then, the gain K2 of the gain unit 130 is varied by the vehicle reverse signal B from the mission unit or CAN (Control Area Network). The gain unit 130 switches so that the gain K2 is reduced when the vehicle is moving forward or stopped when the vehicle reverse signal B is not input, and the gain K2 is increased when the vehicle reverse signal B is input. Other components and their operations are the same as in FIG.

As shown in FIG. 2, the characteristic of the gain unit 130 is a gain AK2 that changes in a mountain shape according to the forward speed when the vehicle moves forward, and is larger than the gain AK2 and becomes constant in a step shape when the vehicle moves backward. Gain BK2. Therefore, when the vehicle moves backward, the SAT estimated value SAT ^* is fed back to the subtracting unit 107C with a larger gain than when moving forward. That is, the amount of SAT feedback when the vehicle moves forward is

AK2 ・ SAT ^*・ ・ ・ (3)

On the other hand, the amount of SAT feedback when the vehicle reverses

BK2 / SAT ^* (> AK2 / SAT ^* ) (4)

It becomes. Thus, since the feedback amount of the SAT estimated value SAT ^* becomes large when the vehicle is reverse, the vehicle behavior is stabilized even when the vehicle is reverse.

Although an example in which the SAT estimated value SAT ^* estimated by the SAT estimating unit 106 is fed back has been described above, feedback may be performed by changing the gain with respect to the SAT value measured by the SAT sensor.

  The present invention can be applied not only to column-type and pinion-type electric power steering devices, but also to rack-assisted electric power steering devices.

It is a block diagram which shows the structural example of the control apparatus which concerns on this invention. It is a figure which shows the example of a characteristic of the gain part which concerns on this invention. It is a general block diagram of the conventional electric power steering device. It is a block diagram which shows an example of the control apparatus of the conventional electric power steering apparatus. It is a figure for demonstrating SAT. It is a block diagram which shows the structural example of a SAT estimation part. It is a figure which shows the example of a characteristic of a gain part.

Explanation of symbols

1 Steering wheel (handle)
3 Reduction gear 10 Torque sensor 12 Vehicle speed sensor 14 Battery 20 Motor 21 Rotation sensor 100 Control unit 101 Current command value calculation unit 102 Angular velocity calculation unit 103 Angular acceleration calculation unit 104 Convergence control unit 105 Inertial compensation unit 106 SAT estimation unit 110 Torque system 111 Steering assist command value calculation unit 112 Phase compensation unit 113 Differentiation unit 120 Current control system 121 Subtraction unit 122 PI control unit 123 PWM control unit 124 Inverter 125 Motor current detection unit 130 Gain unit

Claims (4)

A steering assist command value calculation unit that calculates a steering assist command value based on the steering torque of the vehicle, a current control unit that calculates a voltage command value based on the steering assist command value, and a motor based on the voltage command value A motor driving unit for driving, and SAT estimation means for obtaining a SAT estimated value based on the angular velocity and angular acceleration of the motor, the steering assist command value, and the steering torque, and the SAT estimated value is used as the steering assist command value. In the control device for the electric power steering apparatus, the gain of the SAT estimated value is set when the vehicle is moving forward and backward. A control device for an electric power steering device, characterized in that it has a function to change between. 2. The control device for an electric power steering apparatus according to claim 1, wherein the gain of the estimated SAT value is increased when the vehicle moves backward. The control device for an electric power steering apparatus according to claim 2, wherein a gain of the SAT estimated value is changed in accordance with a reverse speed of the vehicle. 4. The control device for an electric power steering apparatus according to claim 1, wherein SAT measurement means is used in place of the SAT estimation means.

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