JP2012171523A - Electric power steering device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electric power steering device capable of achieving comfortable steering feeling in the turning state of the steering.SOLUTION: It is determined to be in a turning state when steering torque is equal to or above a predetermined value and the differential value of the steering torque is larger than zero or when the steering torque is equal to or below the predetermined value and the differential value of the steering torque is smaller than zero; otherwise, it is determined to be in a returning state. Then, only when it is determined to be in the turning state, a damper compensation control and inertia compensation control are made effective.

Description

  The present invention relates to an electric power steering apparatus.

  Conventionally, in an electric power steering apparatus, a basic assist current is calculated from a steering torque and a vehicle speed, and a damper compensation current for limiting motor rotation and an inertia compensation current for canceling the inertia moment of the motor and system are added to the basic assist current. Control configuration is common.

  For example, in the electric power steering apparatus described in Patent Document 1, the motor rotation angular velocity necessary for the damper compensation current is calculated from the voltage equation of the motor. A high-accuracy damper compensation current is calculated by sampling a number of various motor parameters in advance as motor parameters used in the motor voltage equation.

  Further, for example, in the electric power steering apparatus described in Patent Document 2, when the steering torque and the inertia compensation control amount act in directions opposite to each other, a reduction in steering feeling is prevented by limiting the inertia compensation control amount. is doing.

JP 2004-066999 A JP 2001-114121 A JP 2003-182616 A

  However, in the case of Patent Document 1, when an offset occurs in the estimated motor rotation angular velocity according to the voltage equation of the motor, the damper compensation is performed despite the fact that the vehicle is running straight and in a state close to non-steering. There is a possibility that the steering feeling becomes effective and the steering feeling is lowered.

  In the case of Patent Document 2, when the steering torque and the inertia compensation control amount act in directions opposite to each other, the inertia compensation control amount is limited, so that a reduction in steering feeling can be avoided temporarily. There is no fear. In this regard, in the case of Patent Document 1 and Patent Document 2, there is still room for improvement.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide an electric power steering apparatus capable of obtaining a comfortable steering feeling particularly when the steering wheel is cut. .

  In order to solve the above problems, the invention according to claim 1 is directed to a motor (12) that applies a steering assist force to a steering system of a vehicle, a steering angle sensor (17) that detects a steering angle, and a steering torque. A torque sensor (15) to detect, a steering angular velocity obtained by differentiating the steering angle detected from the steering angle sensor (17), a steering angular acceleration obtained by differentiating the steering angular velocity, and a damper compensation control (microcomputer) according to the steering angular velocity 21) and the inertial compensation control (microcomputer, 21) corresponding to the steering angular acceleration in the electric power steering apparatus (1), the magnitude of the steering torque detected from the torque sensor (15), and Steering state determination means (microcomputer, 21) for determining a steering state in accordance with the direction of change of the steering torque, and the steering state determination means (microcomputer, 21) If there boss alone, the damper compensation control (microcomputer 21) and the inertia compensation control (microcomputer 21) enabling, and the gist.

  According to the above configuration, only when the steering state determination means that determines the steering state according to the magnitude of the absolute value of the steering torque detected from the torque sensor and the change direction of the absolute value of the steering torque determines that it is in the cut state. The damper compensation control and the inertia compensation control can be made effective. As a result, since it is possible to reduce the steering torque only when it is determined that the vehicle is in the cut state, a comfortable steering feeling can be obtained.

  According to a second aspect of the present invention, the steering state determination means (microcomputer, 21) is configured such that the steering torque is equal to or greater than a predetermined value and the differential value of the steering torque is greater than 0, or the steering torque Is not more than a predetermined value and the steering torque differential value is smaller than 0, it is determined as a cutting state, and when it is other than the conditions determined as the cutting state, it is determined as a switching back state. The gist.

According to the above configuration, when the steering torque is equal to or greater than the predetermined value and the differential value of the steering torque is greater than 0, or when the steering torque is equal to or less than the predetermined value and the differential value of the steering torque is smaller than 0. Is determined to be a cut-in state, and in a case other than the condition determined as the cut-in state, it is determined to be a cut-back state.
As a result, it is possible to accurately determine whether the cutting state or the switching back state.

  According to the present invention, it is possible to reduce the steering torque by enabling the damper compensation control and the inertia compensation control only when it is determined that the vehicle is in the cut state, so that a comfortable steering feeling can be obtained. .

The schematic block diagram of an electric power steering device (EPS). The block diagram which shows the electric constitution of EPS. The flowchart figure which shows the process sequence of the steering state determination part in the damper and inertia compensation calculating part of embodiment of this invention.

Hereinafter, an embodiment of the present invention embodied in a column type electric power steering apparatus 1 (hereinafter referred to as EPS) will be described with reference to the drawings.
As shown in FIG. 1, in the EPS 1 of the present embodiment, a steering shaft 3 to which a steering 2 is fixed is connected to a rack shaft 5 via a rack and pinion mechanism 4. The rotation of the steering shaft 3 accompanying the steering operation is converted into a reciprocating linear motion of the rack shaft 5 by the rack and pinion mechanism 4. The steering shaft 3 of this embodiment is formed by connecting a column shaft 8, an intermediate shaft 9, and a pinion shaft 10. Then, the reciprocating linear motion of the rack shaft 5 accompanying the rotation of the steering shaft 3 is transmitted to a knuckle (not shown) via tie rods 6 connected to both ends of the rack shaft 5, whereby the steering angle of the steered wheels 7. Is changed.

  Further, the EPS 1 includes an EPS actuator 13 that applies an assist force for assisting a steering operation to the steering system, and an ECU 11 that serves as a control unit that controls the operation of the EPS actuator 13.

  The EPS actuator 13 of the present embodiment is a column type EPS actuator, and the motor 12 that is a driving source thereof is drivingly connected to the column shaft 8 via a speed reduction mechanism 14. The EPS actuator 13 applies the motor torque as an assist force to the steering system by decelerating the rotation of the motor 12 by the speed reduction mechanism 14 and transmitting it to the column shaft 8.

  A vehicle speed sensor 16, a torque sensor 15, a steering angle sensor 17, and a motor rotation angle sensor 18 are connected to the ECU 11. The ECU 11 detects the vehicle speed V, the steering torque τ, the steering angle θs, and the motor rotation angle θm based on the output signals of these sensors. For example, the torque sensor 15 of the present embodiment is a twin resolver type torque sensor in which a pair of resolvers are provided at both ends of a torsion bar (not shown). Further, the ECU 11 calculates a target assist force based on each detected state quantity, and controls the operation of the EPS actuator 13, that is, the assist force applied to the steering system through the supply of drive power to the motor 12. To do.

Next, an aspect of assist control in the EPS of the present embodiment will be described.
As shown in FIG. 2, the ECU 11 includes a microcomputer 21 that outputs a motor control signal and a drive circuit 40 that supplies drive power to the motor 12 based on the motor control signal.

  In the present embodiment, the ECU 11 includes a current sensor 41 for detecting the actual current value Im supplied to the motor 12 and a motor rotation angle sensor 18 for detecting the rotation angle θm of the motor 12 (see FIG. 1). Is connected. The microcomputer 21 drives the drive circuit 40 based on the vehicle state quantities and the actual current value Im of the motor 12 and the motor rotation angle θm detected based on the output signals of the current sensor 41 and the motor rotation angle sensor 18. A motor control signal to be output to is generated.

  Each control block shown below is realized by a computer program executed by the microcomputer 21. Then, the microcomputer 21 detects each state quantity at a predetermined sampling period, and generates a motor control signal by executing each arithmetic processing shown in the following control blocks every predetermined period.

  Specifically, the microcomputer 21 calculates a current command value Ias * that calculates a current command value Ias *, which is a target value for power supply to the motor 12, and a current command value Ias * calculated by the current command value calculation unit 22. And a motor control signal output unit 35 for outputting a motor control signal based on the motor control signal.

  The current command value calculation unit 22 is provided with a basic assist control unit 24 that calculates a basic assist control amount Ias ** as a basic component of the assist force target value. In the present embodiment, this basic assist control unit The vehicle speed V and the steering torque τ are input to 24. The basic assist control unit 24 is configured to calculate a basic assist control amount Ias ** indicating that a larger assist force should be applied as the absolute value of the steering torque τ is larger and the vehicle speed V is smaller. ing.

  Further, in the present embodiment, the current command value calculation unit 22 calculates a damper / inertia for calculating the inertia compensation control amount Iah * and the damper compensation control amount Iad * based on the steering torque τ, the vehicle speed V, and the steering angle θs. A compensation calculation unit 23 is provided. When the steering wheel is cut, the current command value calculation unit 22 of the present embodiment is based on the inertia compensation control amount Iah * and the damper compensation control amount Iad * calculated by the damper / inertia compensation calculation unit 23. The value is added to the basic assist control amount Ias ** and is output to the motor control signal output unit 35 as a current command value Ias *.

Specifically, the steering torque τ, the vehicle speed V, and the steering angle θs are input to the damper / inertia compensation calculation unit 23 of the present embodiment. The damper / inertia compensation calculation unit 23 calculates the inertia compensation control amount Iah * by the inertia compensation control unit 25 and the damper compensation control amount Iad * by the damper compensation control unit 26 based on these state quantities. Execute.
For details of the calculation of the inertia compensation control amount Iah * and the damping compensation control amount Iad *, see, for example, the contents described in Patent Document 3.

  In addition to the inertia compensation control unit 25 and the damper compensation control unit 26, the damper / inertia compensation calculation unit 23 of the present embodiment is provided with a steering state determination unit 27 that determines a steering state. An inertia compensation switching control unit 28 is provided downstream of the inertia compensation control unit 25, and a damper compensation switching control unit 29 is provided downstream of the damper compensation control unit 26.

  Specifically, the steering torque τ is input to the steering state determination unit 27 of the present embodiment. The steering state determination unit 27 determines the steering state based on the magnitude of the steering torque τ and the change direction of the steering torque τ. Then, the steering state determination unit 27 outputs a steering state determination flag FLG1 that is a result of determining the steering state to the inertia compensation switching control unit 28 and the damper compensation switching control unit 29.

  More specifically, when the microcomputer 21 of the present embodiment determines that the steering state determination unit 27 is in the cut state, the steering state determination flag FLG1 is set to “1”, and the steering state determination unit 27 is in the cut state. If it is determined that the vehicle is in a state other than the above, the steering state determination flag FLG1 is set to “0”.

  When the microcomputer 21 of this embodiment determines that the steering state determination unit 27 is in the cut state (steering state determination flag FLG1 = "1"), the contact 28c and the contact 28a of the inertia compensation switching control unit 28 are used. And the inertia compensation control amount Iah * output from the inertia compensation controller 25 is output to the adder 34.

  On the other hand, when the steering state determination unit 27 determines that it is in a state other than the cutting state (steering state determination flag FLG1 = “0”), the contact 28c and the contact 28b of the inertia compensation switching control unit 28 are connected to the memory 30. The stored data “0” is output to the adder 34.

  In addition, when the microcomputer 21 of the present embodiment determines that the steering state determination unit 27 is in the cut state (steering state determination flag FLG1 = “1”), the contact 29c and the contact 29a of the damper compensation switching control unit 29 are used. And the damper compensation control amount Iad * output from the damper compensation control unit 26 is output to the adder 34.

  On the other hand, when the steering state determination unit 27 determines that the state is other than the cutting state (steering state determination flag FLG1 = “0”), the contact point 29c and the contact point 29b of the damper compensation switching control unit 29 are connected to the memory 31. The stored data “0” is output to the adder 34.

  That is, when the steering state determination unit 27 determines that the vehicle is in the cutting state (steering state determination flag FLG1 = “1”), the current command value Ias * includes the basic assist control amount Ias ** and the inertia compensation control amount. An added value of Iah * and damper compensation control amount Iad * is output to the motor control signal output unit 35.

  On the other hand, when the steering state determination unit 27 determines that it is in a state other than the cutting state (steering state determination flag FLG1 = “0”), the current command value Ias * is the value of only the basic assist control amount Ias **. It is output to the control signal output unit 35.

  The motor control signal output unit 35 includes the current command value Ias * output from the current command value calculation unit 22, the actual current value Im detected by the current sensor 41, and the motor detected by the rotation angle sensor 18. Twelve rotation angles θm are input. The motor control signal output unit 35 calculates a motor control signal by executing feedback control so that the actual current value Im follows the current command value Ias *.

  Specifically, in the present embodiment, a brushless motor that rotates by supplying three-phase (U, V, W) driving power is used as the motor 12. The motor control signal output unit 35 converts the phase current value (Iu, Iv, Iw) of the motor 12 detected as the actual current value Im into d and q axis current values in the d / q coordinate system (d / q The current feedback control is performed by performing conversion.

  That is, the current command value Ias * is input to the motor control signal output unit 35 as a q-axis current command value, and the motor control signal output unit 35 is based on the motor rotation angle rotation angle θm detected by the rotation angle sensor 18. Phase current values (Iu, Iv, Iw) are d / q converted. The motor control signal output unit 35 calculates the d and q-axis voltage command values based on the d and q-axis current values and the q-axis current command value. Then, the phase voltage command values (Vu *, Vv *, Vw *) are calculated by performing d / q inverse conversion on the d and q axis voltage command values, and a motor control signal is generated based on the phase voltage command values. To do.

  The motor control signal generated in this way is output from the microcomputer 21 to the drive circuit 40, and the drive circuit 40 supplies three-phase drive power based on the motor control signal to the motor 12. When the motor torque corresponding to the current command value Ias * as the assist force target value based on the steering torque τ is generated, the assist force corresponding to the assist force target value is applied to the steering system. ing.

Next, a processing procedure of the steering state determination unit 27 in the damping / inertia compensation calculation unit 23 configured as described above will be described.
As shown in the flowchart of FIG. 3, the microcomputer 21 reads the steering torque τ (step S101). Next, the read steering torque τ is differentiated to calculate the change amount dτ / dt of the steering torque τ (step S102). Then, it is determined whether or not the steering torque τ is equal to or greater than a predetermined steering torque value τ1 and the change amount dτ / dt of the steering torque τ is greater than 0 (step S103).

  When the steering torque τ is equal to or greater than the predetermined steering torque value τ1 and the change amount dτ / dt of the steering torque τ is greater than 0 (τ ≧ τ1 and dτ / dt> 0, step S103, YES), the steering state “1” is written to the determination flag FLG1 (FLG1 = “1”, step S104), and the process proceeds to step S105 and step S106.

  In step S105, the contact 28c and the contact 28a of the inertia compensation switching control unit 28 are connected, and in step S106, the contact 29c and the contact 29a of the damper compensation switching control unit 29 are connected, and the process ends. That is, since it is in the cut state, the inertia compensation control amount Iah * is added to the basic assist control amount Ias **, and the damper compensation control amount Iad * is subtracted.

  When the steering torque τ is equal to or greater than the predetermined steering torque value τ1 and the change amount dτ / dt of the steering torque τ is not greater than 0 (NO in step S103), the steering torque τ is equal to the predetermined steering torque value. It is determined whether or not −τ1 or less and the change amount dτ / dt of the steering torque τ is smaller than 0 (step S107).

  When the steering torque τ is equal to or smaller than the predetermined steering torque value −τ1 and the change amount dτ / dt of the steering torque τ is smaller than 0 (τ ≦ −τ1 and dτ / dt <0, step S107, YES), “1” is written in the steering state determination flag FLG1 (FLG1 = “1”, step S104), and the process proceeds to step S105 and step S106.

  Further, when the steering torque τ is equal to or smaller than the predetermined steering torque value −τ1 and the change amount dτ / dt of the steering torque τ is not smaller than 0 (step S107, NO), the steering state determination flag FLG1 is set to “0”. "(FLG1 =" 0 ", step S108), the process proceeds to step S109 and step S110.

  In step S109, the contact 28c and the contact 28b of the inertia compensation switching control unit 28 are connected, and in step S110, the contact 29c and the contact 29b of the damper compensation switching control unit 29 are connected, and the process ends. That is, since the state is other than the cutting state, the basic assist control amount Ias ** inertia compensation control amount Iah * (= 0) is added, and the damper compensation control amount Iad * (= 0) is subtracted.

As described above, according to the present embodiment, the following operations and effects can be obtained.
When the steering torque is equal to or greater than a predetermined value and the differential value of the steering torque is greater than 0, or when the steering torque is equal to or smaller than the predetermined value and the differential value of the steering torque is smaller than 0, If it is determined that the condition is other than the condition determined as the cut-in state, the switch-back state is determined. The damper compensation control and the inertia compensation control are made effective only when the cut state is determined.

  As a result, the steering state of the vehicle can be accurately determined, and the inertia compensation control amount Iah * and the damper compensation control amount Iad * can be output only when the steering wheel is turned, so that a comfortable steering feeling can be obtained. Can do.

In addition, you may change this embodiment as follows.
In each of the above embodiments, the present invention is embodied in a so-called column type EPS 1, but the present invention may be applied to a so-called pinion type or rack assist type EPS.

  In the above embodiment, the present invention is embodied in EPS using a brushless motor as a drive source. However, the present invention may be applied to EPS using a DC motor with a brush as a drive source.

1: Electric power steering device (EPS), 2: Steering,
3: Steering shaft, 4: Rack and pinion mechanism, 5: Rack shaft,
6: Tie rod, 7: Steering wheel, 8: Column shaft,
9: Intermediate shaft, 10: Pinion shaft, 11: ECU,
12: Motor, 13: EPS actuator, 14: Deceleration mechanism,
15: Torque sensor, 16: Vehicle speed sensor, 17: Steering angle sensor,
18: Motor rotation angle sensor, 21: Microcomputer, 22: Current command value calculation unit,
23: damper / inertia compensation calculation unit, 24: basic assist control unit,
25: inertia compensation control unit, 26: damper compensation control unit, 27: steering state determination unit,
28: Inertia compensation switching control unit, 29: Damper compensation switching control unit,
30, 31: memory, 34: adder, 35: motor control signal output unit,
40: drive circuit, 41: current sensor,
V: vehicle speed, τ: steering torque, θs: steering angle, θm: motor rotation angle,
ωm: motor rotation angular velocity, Im: actual current value, Ias *: current command value,
Ias **: Basic assist control amount, Iah *: Inertia compensation control amount,
Iad *: damper compensation control amount, FLG1: steering state determination flag,
28a, 28b, 28c, 29a, 29b, 29c: contact point, τ1: predetermined steering torque value

Claims (2)

A motor for applying a steering assist force to the vehicle steering system;
A steering angle sensor for detecting the steering angle;
A torque sensor for detecting steering torque;
Steering angular velocity obtained by differentiating the steering angle detected from the steering angle sensor;
Steering angular acceleration obtained by differentiating the steering angular velocity,
Damper compensation control according to the steering angular velocity;
In the electric power steering apparatus comprising the inertia compensation control according to the steering angular acceleration,
Steering state determination means for determining a steering state according to the magnitude of the steering torque detected from the torque sensor and the direction of change of the steering torque;
The electric power steering apparatus characterized by enabling the damper compensation control and the inertia compensation control only when the steering state determination means determines that the vehicle is in the cut state.   The steering state determination unit is configured such that the steering torque is equal to or greater than a predetermined value and the differential value of the steering torque is greater than 0, or the steering torque is equal to or less than the predetermined value and the differential value of the steering torque. 2. The electric power steering apparatus according to claim 1, wherein when the value is smaller than 0, it is determined as a cutting state, and when the condition other than the condition determined as the cutting state is determined, a switching back state is determined.

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