JP4618614B2 - Electric power steering control device - Google Patents

Description

  The present invention relates to an electric power steering control device that generates an assist torque for assisting a driver's steering torque by a motor.

  Conventionally, the target current for the motor is set based on the steering torque detected by the torque sensor and the vehicle speed detected by the vehicle speed sensor, and by the PI (proportional integral) control means or the PID (proportional integral derivative) control means, There is known an electric power steering that compensates for a phase lag and deviation between a target current and a drive current that is actually energized to the motor.

In this electric power steering, the gain is greatly improved in the region where the angular frequency is low, and the phase lag is greatly improved in the region where the angular frequency is high, but PI control or PID control is affected by noise mixed from outside. Easy to receive.
For this reason, there has been a problem that the vibration of the steering system is generated by noise from the outside, causing the driver to feel uncomfortable torque vibration.

  Therefore, in order to solve the above-described problems, the conventional electric power steering includes a steering torque sensor that detects the steering torque of the steering system, an electric motor that applies a steering assist force to the steering system, and steering from the steering torque sensor. Target current setting means for determining the target current of the motor based on the torque signal, motor current detection means for detecting the motor current flowing in the motor, and controlling the driving of the motor based on the deviation between the target current and the motor current, A control means having at least a proportional element and an integral element, a path connecting the motor current detection means and the control means, and a path connecting the control means and the target current setting means, respectively, and an attenuation means for attenuating high frequency noise (For example, refer to Patent Document 1).

Japanese Patent No. 2959957

In the conventional electric power steering, the damping means attenuates the high frequency noise, so that the vibration of the steering system is suppressed and unpleasant torque vibration for the driver is suppressed.
However, the attenuation means always attenuates high frequency noise regardless of the steering state.
Therefore, in a steering state where high responsiveness is required in motor driving (a vehicle speed or a high rotational speed of the motor), a desired responsiveness cannot be obtained due to the influence of the damping operation by the damping means, and the responsiveness is low. There was a problem of becoming.

  An object of the present invention is to solve the above-described problems, and an object thereof is to realize high responsiveness and high responsiveness in a steering state where high responsiveness is required. An object of the present invention is to provide an electric power steering control device capable of suppressing the vibration of the steering system due to noise and the unpleasant torque vibration for the driver in a steering state in which no is required.

An electric power steering control device according to the present invention generates a steering torque detecting means for detecting a steering torque by a vehicle driver, a vehicle speed detecting means for detecting a vehicle speed of the vehicle, and an auxiliary torque for assisting the steering torque. Motor, a rotation speed detection means for detecting the rotation speed of the motor, a current detection means for detecting a drive current applied to the motor, and a target current calculation means for calculating a target current for the motor based at least on the steering torque And a target current attenuating means for attenuating the target current and outputting the attenuated target current, and the target current attenuating means is less than a predetermined speed at which the rotational speed is zero or low and becomes a steering or fine steering . If, with attenuates at least high frequency components of the target current, when the rotational speed is greater than the predetermined speed, stop or suppress the attenuation of the target current Than is.

According to the electric power steering control device of the present invention, the target current attenuation means attenuates at least a high-frequency component of the target current according to at least one of the vehicle speed and the rotational speed.
Therefore, in a steering state where high responsiveness is required, high responsiveness is realized, and in a steering state where high responsiveness is not required, steering system vibration due to noise and unpleasant torque vibration to the driver are suppressed. can do.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the drawings, the same or corresponding members and parts will be described with the same reference numerals.

Embodiment 1 FIG.
FIG. 1 is a block diagram showing an electric power steering control apparatus according to Embodiment 1 of the present invention.
In FIG. 1, this electric power steering control device includes a torque sensor 1 (steering torque detection means), a vehicle speed sensor 2 (vehicle speed detection means), a motor 3, a current detector 4 (current detection means), and a rotation. A speed sensor 5 (rotational speed detection means) and a main control unit 6 are provided.

The torque sensor 1 detects a steering torque generated by the steering of the vehicle driver and outputs a steering torque signal. The vehicle speed sensor 2 detects the vehicle speed of the vehicle and outputs a vehicle speed signal. The motor 3 generates an auxiliary torque for assisting the steering torque.
The current detector 4 detects a drive current energized to the motor 3 and outputs a drive current signal. The rotation speed sensor 5 detects the rotation speed of the motor 3 and outputs a rotation speed signal.
The main control unit 6 takes in a steering torque signal, a vehicle speed signal, a drive current signal, and a rotation speed signal, performs A / D conversion, calculates a target voltage for the motor 3, and outputs a target voltage signal.

The main control unit 6 includes a target current calculation unit 7 (target current calculation unit), a target current attenuation unit 8 (target current attenuation unit), and a current control unit 9 (target voltage control unit).
Here, the main control unit 6 is composed of a microprocessor (not shown). The microprocessor includes a CPU that executes arithmetic processing, a ROM that stores program data and fixed value data, and a RAM that can rewrite stored data. Each block constituting the main control unit 6 is stored as software in the ROM.
ROM and RAM may be provided in each block constituting the electric power steering control device of FIG.

The target current calculation unit 7 calculates a target current for the motor 3 based on the steering torque signal and the vehicle speed signal, and outputs a target current signal.
That is, the target current calculation unit 7 stores a steering torque / vehicle speed-target current map in which the relationship between the steering torque and the vehicle speed and the target current is recorded in the ROM, and based on the steering torque signal and the vehicle speed signal, The target current is calculated from this map.

The target current attenuation unit 8 is provided between the target current calculation unit 7 and the current control unit 9, attenuates the target current signal in accordance with the vehicle speed signal and the rotation speed signal, and provides an attenuated target current signal (attenuated target current signal). Current).
The current controller 9 compares the drive current signal from the current detector 4 with the attenuated target current signal from the target current attenuator 8 so that the drive current of the motor 3 matches the attenuated target current. The target voltage applied to the terminal of the motor 3 is calculated by PI control or PID control, and the target voltage signal is output as, for example, a PWM signal.

The target current attenuator 8 includes an attenuation gain calculator 10 (subtraction gain calculator) and a coefficient multiplier 11 (coefficient multiplier).
The attenuation gain calculation unit 10 calculates an attenuation gain K (≦ 1) for attenuating the target current signal based on the vehicle speed signal and the rotation speed signal. The coefficient multiplier 11 multiplies the target current signal by a predetermined coefficient (1-K) corresponding to the attenuation gain K to attenuate the target current signal, and outputs the attenuated target current signal.

That is, the attenuation gain calculation unit 10 stores a vehicle speed / rotation speed-attenuation gain map in which the relationship between the vehicle speed and the rotation speed and the attenuation gain K is recorded in the ROM, and based on the vehicle speed signal and the rotation speed signal. The attenuation gain K is calculated from this map.
FIG. 2 is an explanatory diagram showing a vehicle speed / rotation speed-attenuation gain map provided in the attenuation gain calculation unit 10.

In FIG. 2, the attenuation gain calculation unit 10 is provided with three types of attenuation gain maps, a high-speed attenuation gain map A, a medium-speed attenuation gain map B, and a low-speed attenuation gain map C according to the vehicle speed.
In each attenuation gain map, the attenuation gain K is set so as to decrease as the rotational speed of the motor 3 increases as in the low-speed attenuation gain map C, for example.
The attenuation gain calculation unit 10 first selects one of the three types of attenuation gain maps based on the vehicle speed signal, and then calculates the attenuation gain K from the selected attenuation gain map based on the rotation speed signal.

Hereinafter, the operation of the main control unit 6 in the electric power steering control device having the above configuration will be described with reference to the flowchart of FIG.
First, the main control unit 6 reads the steering torque signal from the torque sensor 1 and stores it in the RAM every predetermined sampling period (step S21).
The main control unit 6 reads the rotation speed signal from the rotation speed sensor 5 and stores it in the RAM (step S22).
The main control unit 6 reads the vehicle speed signal from the vehicle speed sensor 2 and stores it in the RAM (step S23).
The main control unit 6 reads the drive current signal from the current detector 4 and stores it in the RAM (step S24).

Subsequently, the target current calculation unit 7 calculates a target current for the motor 3 from the above-described steering torque / vehicle speed-target current map based on the steering torque signal and the vehicle speed signal, and stores the target current signal in the RAM (step). S25).
Next, the attenuation gain calculator 10 calculates the attenuation gain K from the vehicle speed / rotation speed-attenuation gain map shown in FIG. 2 based on the vehicle speed signal and the rotation speed signal, and stores it in the RAM (step S26).

Subsequently, the coefficient multiplier 11 multiplies the target current signal by a predetermined coefficient (1-K) corresponding to the attenuation gain K to attenuate the target current signal, and stores the attenuated target current signal in the RAM (step S27). ).
Next, the current control unit 9 calculates a target voltage to be applied to the terminal of the motor 3 so that the drive current of the motor 3 matches the target current after attenuation based on the drive current signal and the target current signal after attenuation. The target voltage signal is stored in the RAM (step S28), and the process of FIG.

According to the electric power steering control device according to the first embodiment of the present invention, the attenuation gain calculation unit 10 is based on the vehicle speed signal and the rotation speed signal from the vehicle speed / rotation speed-attenuation gain map shown in FIG. The attenuation gain K (≦ 1) is calculated, and the coefficient multiplier 11 multiplies the target current signal by a predetermined coefficient (1-K) corresponding to the attenuation gain K to attenuate the target current signal.
Therefore, in a steering state where high responsiveness is required in motor driving, the attenuation gain K calculated by the attenuation gain calculation unit 10 becomes a low value (or zero), and the attenuation operation by the coefficient multiplication unit 11 is suppressed or stopped. Therefore, high responsiveness can be realized.
Further, a steering state in which high responsiveness is not required, that is, a state where the vehicle speed is low and the steering wheel of the vehicle is being steered (a state where the rotation speed of the motor 3 is zero, hereinafter referred to as “steering state”), or In a state where the steering wheel is being steered by a fine steering (a state where the rotational speed of the motor 3 is low, hereinafter referred to as “a fine steering state”), the attenuation gain K calculated by the attenuation gain calculating unit 10 is a high value. Therefore, the damping operation by the coefficient multiplication unit 11 can suppress the vibration of the steering system due to noise and the unpleasant torque vibration for the driver.

In addition, although the attenuation gain calculation part 10 of the said Embodiment 1 calculated the attenuation gain K based on the vehicle speed signal and the rotational speed signal, it is not limited to this, Based on either one of a vehicle speed signal and a rotational speed signal Thus, the attenuation gain K may be calculated.
At this time, the attenuation gain calculation unit 10 stores a map in which the relationship between the vehicle speed or the rotation speed and the attenuation gain K is stored in the ROM, and calculates the attenuation gain K from the map based on the vehicle speed signal or the rotation speed signal. Calculate.
Also in this case, the same effect as in the first embodiment can be obtained.

Embodiment 2. FIG.
In the first embodiment, the target current attenuation unit 8 calculates the attenuation gain K based on the vehicle speed signal and the rotation speed signal, attenuates the target current signal using the attenuation gain K, and outputs the attenuated target current signal. However, the present invention is not limited to this, and a low-pass filter (hereinafter referred to as “LPF”) may be used to remove only the high-frequency component of the target current signal and output the attenuated target current signal.

FIG. 4 is a block diagram showing an electric power steering control apparatus according to Embodiment 2 of the present invention.
In FIG. 4, the electric power steering control device includes a target current attenuation unit 8A instead of the target current attenuation unit 8 shown in FIG.

The target current attenuating unit 8A includes an LPF 12 (specific frequency component removing unit) and a switching unit 13 (switching unit).
The LPF 12 removes a high frequency component (specific frequency component) of the input target current signal. The switching unit 13 selects whether or not to enable the LPF 12 based on the vehicle speed signal and the rotation speed signal, and outputs an attenuated target current signal.

That is, the switching unit 13 enables the LPF 12 when the vehicle speed is equal to or lower than the predetermined vehicle speed and the rotational speed is equal to or lower than the predetermined speed, and outputs the target current signal from which the high frequency component has been removed by the LPF 12 as the attenuated target current signal. .
The switching unit 13 disables the LPF 12 when the vehicle speed is higher than the predetermined vehicle speed or the rotational speed is higher than the predetermined speed, and the target current signal from the target current calculation unit 7 is attenuated as it is. Output as.
Other configurations are the same as those of the first embodiment, and the description thereof is omitted.

Hereinafter, the operation of the main control unit 6A in the electric power steering control device having the above configuration will be described with reference to the flowchart of FIG.
Note that the description of the same operation as in the first embodiment is omitted.
First, the target current calculation unit 7 calculates a target current for the motor 3 from the steering torque / vehicle speed-target current map based on the steering torque signal and the vehicle speed signal, and stores the target current signal in the RAM (step S25). ).

Subsequently, the switching unit 13 determines whether or not the vehicle speed is equal to or lower than a predetermined vehicle speed based on the vehicle speed signal (step S31).
When it is determined in step S31 that the vehicle speed is equal to or lower than the predetermined vehicle speed (that is, Yes), the switching unit 13 determines whether the rotational speed is equal to or lower than the predetermined speed based on the rotational speed signal (step S31). S32).

  In step S32, when it is determined that the rotation speed is equal to or lower than the predetermined speed (that is, Yes), the switching unit 13 enables the LPF 12, and attenuates the target current signal from which the high-frequency component has been removed by the LPF 12 to the target current after attenuation. A signal is stored in the RAM (step S33).

  On the other hand, if it is determined in step S31 that the vehicle speed is greater than the predetermined vehicle speed (ie, No), or if it is determined in step S32 that the rotational speed is greater than the predetermined speed (ie, No), the switching unit. 13 invalidates the LPF 12 and stores the target current signal from the target current calculation unit 7 as it is in the RAM as an attenuated target current signal (step S34).

According to the electric power steering control apparatus according to Embodiment 2 of the present invention, the LPF 12 removes the high frequency component of the input target current signal, and the switching unit 13 is based on the vehicle speed signal and the rotational speed signal. Whether to enable the LPF 12 is selected, and a target current signal after attenuation is output.
Therefore, in a steering state where high responsiveness is required in motor driving, the target current signal from which the high frequency component has been removed by the LPF 12 is output from the switching unit 13 as the target current signal after attenuation, thereby realizing high responsiveness. can do.
Further, in a steering state where high responsiveness is not required, that is, in a steered state or a finely steered state, the target current signal calculated by the target current calculating unit 7 is directly output from the switching unit 13 as an attenuated target current signal. Therefore, vibrations of the steering system due to noise and unpleasant torque vibrations for the driver can be suppressed.

Note that the switching unit 13 of the second embodiment has selected whether to enable the LPF 12 based on the vehicle speed signal and the rotation speed signal, but is not limited to this, and either the vehicle speed signal or the rotation speed signal is selected. Whether to enable the LPF 12 may be selected based on one of them.
At this time, the switching unit 13 enables the LPF 12 when the vehicle speed is equal to or lower than the predetermined vehicle speed or when the rotational speed is equal to or lower than the predetermined speed.
Also in this case, the same effects as those of the second embodiment can be obtained.

Further, the LPF 12 of the second embodiment is configured as software, but may be configured as hardware.
Also in this case, the same effects as those of the second embodiment can be obtained.

Further, the target current attenuating unit 8A of the second embodiment uses the LPF 12 to remove the high frequency component of the target current signal, but is not limited to this.
The target current attenuator 8A replaces the LPF 12 and samples a plurality of values of the target current signal to calculate a moving average, thereby removing a high frequency component (specific high frequency component) of the target current signal. (Specific frequency component removing means) may be included.
Also in this case, the same effects as those of the second embodiment can be obtained.

Moreover, although the target current calculation part 7 of the said Embodiment 1, 2 calculated the target current with respect to the motor 3 based on a steering torque signal and a vehicle speed signal, it is not limited to this.
The target current calculation unit 7 may calculate the target current based only on the steering torque signal.
At this time, the target current calculation unit 7 stores a map in which the relationship between the steering torque and the target current is stored in the ROM, and calculates the target current from this map based on the steering torque signal.
Also in this case, the same effects as those of the first and second embodiments can be obtained.

In the first and second embodiments, the rotational speed of the motor 3 is detected using the rotational speed sensor 5, but the present invention is not limited to this.
The rotational speed of the motor 3 may be calculated by differentiating the amount of change in the position of the motor 3, or may be estimated from the relationship between the drive voltage and drive current applied to the motor 3.
In these cases, the same effects as those of the first and second embodiments can be obtained.

1 is a block diagram showing an electric power steering control device according to Embodiment 1 of the present invention. FIG. It is explanatory drawing which shows the vehicle speed and rotational speed-attenuation gain map provided in the attenuation gain calculating part of FIG. It is a flowchart which shows operation | movement of the main-control part by Embodiment 1 of this invention. It is a block diagram which shows the electric power steering control apparatus which concerns on Embodiment 2 of this invention. It is a flowchart which shows operation | movement of the main-control part by Embodiment 2 of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Torque sensor (steering torque detection means), 2 Vehicle speed sensor (vehicle speed detection means), 3 Motor, 4 Current detector (current detection means), 5 Rotational speed sensor (rotational speed detection means), 7 Target current calculation part (Target) Current calculation means), 8, 8A Target current attenuation section (target current attenuation means), 9 Current control section (target voltage control means), 10 Attenuation gain calculation section (subtraction gain calculation means), 11 Coefficient multiplication section (coefficient multiplication means) ), 12 LPF (specific frequency component removing means), 13 switching unit (switching means), K attenuation gain.

Claims (7)

Steering torque detection means for detecting steering torque by a driver of the vehicle;
Vehicle speed detecting means for detecting the vehicle speed of the vehicle;
A motor for generating an auxiliary torque for assisting the steering torque;
Rotation speed detection means for detecting the rotation speed of the motor;
Current detection means for detecting a drive current supplied to the motor;
Target current calculation means for calculating a target current for the motor based on at least the steering torque;
A target current attenuation means for attenuating the target current and outputting the target current after attenuation,
The target current attenuating means attenuates at least a high frequency component of the target current when the rotational speed is equal to or lower than a predetermined speed at which the rotational speed is zero or low and is maintained or finely steered, and the rotational speed is the predetermined speed. An electric power steering control device that stops or suppresses the attenuation of the target current when it is larger than The target current attenuating means is
An attenuation gain calculating means for calculating an attenuation gain for attenuating the target current based on at least one of the vehicle speed and the rotational speed;
The electric power steering control device according to claim 1, further comprising coefficient multiplying means for multiplying the target current by a predetermined coefficient corresponding to the attenuation gain.   The electric power steering control device according to claim 2, wherein the target current attenuation means further attenuates the target current when the vehicle speed is equal to or lower than a predetermined vehicle speed. The target current attenuating means is
Specific frequency component removing means for removing the high frequency component of the input signal;
2. The electric power steering according to claim 1, further comprising: a switching unit that selects whether or not to enable the specific frequency component removing unit based on at least one of the vehicle speed and the rotational speed. Control device.   5. The electric power steering control device according to claim 4, wherein the target current attenuating unit further attenuates the target current when the vehicle speed is equal to or lower than a predetermined vehicle speed.   6. The electric power steering control device according to claim 4, wherein the specific frequency component removing unit removes the high frequency component using a filter.   6. The electric power steering control device according to claim 4, wherein the specific frequency component removing unit removes the high-frequency component by calculating a moving average of the target current.

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