JP2006298002A - Electric power steering control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electric power steering control device capable of removing influence of the steering frequency associated with the steering operation made by a driver, suppressing oscillation generated in a steering control system by calculating the corrective current in accordance with the assist torque gradient, and suppressing a steering vibration uncomfortable for the driver. <P>SOLUTION: The electric power steering control device is equipped with a torque sensor 1 to sense the steering torque, a motor 2 to generate an assist torque to assist the steering torque, and a target current calculating means 3 to calculate the target current to be fed to the motor 2 on the basis of the steering torque, wherein the target current calculating means 3 comprises a torque control part 7 to calculate the assist torque current in accordance with the assist torque, an assist torque gradient sensing part 8 to sense the gradient of the assist torque from the assist torque current, a steering torque HPF 9 and a drive current HPF 10 to remove the frequency component associated with the steering operation made by the driver, an angle control part 13 to calculate the corrective current for suppressing the vibration generated in the steering control system of the vehicle, and an addition part 14 to calculate the target current. <P>COPYRIGHT: (C)2007,JPO&INPIT

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.

  The electric power steering device detects a steering torque generated when the driver rotates the steering wheel, and supplies an auxiliary torque current corresponding to the auxiliary torque for assisting the steering torque to a motor meshed with a gear of the steering mechanism. By doing so, an auxiliary torque is generated.

  However, when the vehicle is stopped and the vehicle is traveling at a low speed, the resistance force from the road surface is increased, so that it is necessary to increase the auxiliary torque gradient, which is the gradient of the auxiliary torque current with respect to the steering torque. When the auxiliary torque gradient is high, the steering control system oscillates, and the steering wheel tends to vibrate. This causes the driver to feel uncomfortable.

  Therefore, in order to solve the above-described problems, the conventional electric power steering control device is operated by steering torque detection means for detecting a steering torque by a driver and an auxiliary torque current calculated based on the steering torque. A motor that generates torque for assisting the torque, a rotational speed detecting means for estimating or measuring the rotational speed of the motor, and a steering component removing means for removing a speed component by steering from the estimated or measured motor rotational speed. Yes. The steering torque is reduced without causing the driver to feel uncomfortable steering wheel vibration by calculating the damping current using a signal obtained by removing the speed component due to steering from the signal obtained by measuring or estimating the rotational speed of the motor. (For example, refer to Patent Document 1).

  In addition, the conventional electric power steering device has a driving current of the electric motor for assisting steering (the “auxiliary torque current” of the present invention) according to the torque applied to the steering wheel (corresponding to the “steering torque” of the present invention). And an auxiliary torque gradient that is a rate of change of the drive current with respect to torque increases. Accordingly, the electric power steering apparatus includes a changing unit that changes the inertia compensation current so that the correction drive current decreases, and drives the electric motor with the correction drive current obtained by adding the inertia compensation current to the drive current. When the inertia compensation current increases, the steering control system easily oscillates. Therefore, when the auxiliary torque gradient is high, the inertia compensation current is reduced to suppress the steering control system oscillation (for example, Patent Documents). 2).

JP 2000-168600 A JP 2003-81102 A

  Since the conventional electric power steering control device does not consider the auxiliary torque gradient, the damping current is supplied to the motor even when the auxiliary torque gradient is low and the steering control system does not easily oscillate. Therefore, when noise is superimposed on the measured or estimated motor rotation speed signal, the auxiliary torque current including the noise is applied to the motor, resulting in uneven torque. When the auxiliary torque gradient is high, torque unevenness caused by noise can be suppressed. However, when the auxiliary torque gradient is low, there is a problem that the torque unevenness cannot be sufficiently suppressed.

  Further, in the conventional electric power steering apparatus, since the steering frequency accompanying the steering of the driver is not taken into consideration, when the assist torque gradient is high, the inertia in the steering frequency band increases, and the steering feeling of the driver is deteriorated. There was also a problem.

  An object of the present invention is to solve the above-described problems, and an object of the present invention is to eliminate the influence of the steering frequency accompanying the steering of the driver and to adjust the correction current according to the auxiliary torque gradient. An object of the present invention is to provide an electric power steering control device capable of suppressing oscillation generated in a steering control system and calculating unpleasant steering wheel vibration to a driver by calculating.

  An electric power steering control device according to the present invention includes a steering torque detecting means for detecting a steering torque by a driver of a vehicle, a motor for generating an auxiliary torque for assisting the steering torque, and a motor based on at least the steering torque. Target current calculation means for calculating a target current to be energized, the target current calculation means for calculating an auxiliary torque current according to the auxiliary torque based on the steering torque, and an auxiliary torque from the auxiliary torque current Auxiliary torque gradient detecting means for detecting the gradient of the vehicle, a steering component removing means for removing the frequency component accompanying the driver's steering, and a correction for suppressing the vibration generated in the steering control system of the vehicle according to the auxiliary torque gradient Vibration suppression control means for calculating the current, and addition means for calculating the target current by adding the auxiliary torque current and the correction current. Is Dressings.

  According to the electric power steering control device of the present invention, the influence of the steering frequency accompanying the steering of the driver is removed using the steering component removing means, and the vibration suppression control means calculates the correction current according to the auxiliary torque gradient. In any case, oscillation generated in the steering control system can be suppressed, and unpleasant steering wheel vibration to the driver can be suppressed.

  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.
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 detecting means) that detects a steering torque generated by a driver's steering and outputs a steering torque signal, and an auxiliary torque for assisting the steering torque. , A target current calculation means 3 for calculating a target current to be supplied to the motor 2 using a steering torque signal, and a drive current supplied to the motor 2 is detected and a motor drive current is output. The current detector 4 compares the target current with the motor drive current, sets the drive voltage command value to be applied to the terminal of the motor 2 so that the motor drive current matches the target current, and outputs, for example, a PWM signal And a current controller 5.

The target current calculation means 3 is composed of a microprocessor (not shown) having a storage unit storing a program and a CPU. Each block constituting the target current calculation means 3 is stored as software in the storage unit.
The target current calculation means 3 includes a phase compensation section 6, a torque control section 7 (torque control means), an auxiliary torque gradient detection section 8 (auxiliary torque gradient detection means), and a steering torque high-pass filter 9 (steering component removal). Means) (hereinafter abbreviated as “steering torque HPF9”), driving current high-pass filter 10 (steering component removing means) (hereinafter abbreviated as “driving current HPF10”), and rotational speed observer 11 (rotational speed detecting means). ), An integration unit 12 (rotation angle detection unit), an angle control unit 13 (vibration suppression control unit), and an addition unit 14.

The phase compensation unit 6 improves the frequency characteristics by phase compensation of the steering torque signal, and outputs a compensated torque signal.
The torque control unit 7 has a steering torque-auxiliary torque current map in which the relationship between the steering torque and the auxiliary torque current is described. The torque control unit 7 calculates an auxiliary torque current from the steering torque-auxiliary torque current map based on the compensated steering torque signal.

The auxiliary torque gradient detector 8 has an auxiliary torque current-auxiliary torque gradient map in which the relationship between the auxiliary torque current and the auxiliary torque gradient is described. The auxiliary torque gradient detection unit 8 detects the gradient of the auxiliary torque from the auxiliary torque current-auxiliary torque gradient map based on the auxiliary torque current, and outputs an auxiliary torque gradient signal.
The steering torque HPF 9 removes a steering frequency component related to the driver's steering from the steering torque signal and outputs a torque HPF signal. The drive current HPF10 removes a steering frequency component related to the driver's steering from the motor drive current and outputs a current HPF signal.

The rotational speed observer 11 incorporates a vibration equation in which the moment of inertia of the motor 2 is an inertia term and the rigidity of the torque sensor 1 is a spring term. The rotational speed observer 11 calculates a rotational speed estimation signal of the motor 2 based on the torque HPF signal and the current HPF signal.
The integrator 12 integrates the rotation speed estimation signal to calculate the rotation angle of the motor 2 and outputs a rotation angle signal.

The angle control unit 13 calculates an angle control current (correction current) for controlling the steering angle based on the auxiliary torque gradient signal and the rotation angle signal.
The adding unit 14 adds the auxiliary torque current and the angle control current, calculates a target current to be supplied to the motor 2, and outputs the target current to the current controller 5.

Hereinafter, the operation of the electric power steering control apparatus having the above configuration will be described with reference to the flowchart of FIG.
The difference between the present invention and the background art is an algorithm for calculating an angle control current using an auxiliary torque gradient and calculating a target current based on the auxiliary torque current and the angle control current. Only the above algorithm in the target current calculation means 3 will be described.

  The control of the current controller 5 for supplying the target current to the motor 2 is generally performed by digital control or analog control such as PID feedback control or open loop control based on the target current and the motor rotation signal. It is assumed that control is implemented.

  In addition, the operation of each block of the target current calculation unit 3 involves storing information in the storage unit and reading information from the storage unit.

First, the steering torque by the driver is detected by the torque sensor 1 at every control sampling period, and a steering torque signal is captured (step S31).
Further, the current detector 4 detects a current supplied to the motor 2 from the current controller 5 and outputs a motor drive current (step S32).

Subsequently, the phase compensation unit 6 performs a phase compensation calculation on the steering torque signal, and outputs a compensated torque signal with improved frequency characteristics (step S33).
The torque control unit 7 calculates an auxiliary torque current from the steering torque-auxiliary torque current map based on the compensated torque signal (step S34).

Next, in the steering torque HPF9, the steering frequency component is removed from the steering torque signal, and the torque HPF signal is output (step S35).
Further, in the drive current HPF10, the steering frequency component is removed from the motor drive current, and a current HPF signal is output (step S36).

Here, the steering torque HPF9 and the drive current HPF10 will be described in detail.
Generally, the steering frequency associated with the driver's steering is about 3 Hz or less. Further, for example, the steering frequency at the time of lane change is around 0.2 Hz, and usually such low frequency steering is often performed. On the other hand, the frequency band in which oscillation of the steering control system is likely to occur is 30 Hz or more. Therefore, frequency separation between the steering frequency and the frequency at which oscillation of the steering control system is likely to occur is possible.

  Therefore, by using the steering torque HPF 9 and the drive current HPF 10, the steering frequency components of the steering torque signal and the motor drive current can be removed, respectively, and the motor 2 steering speed estimation signal calculated by the rotation speed observer 11 is steered. It is possible to prevent frequency components from being superimposed.

Here, when the corner frequency of the steering torque HPF9 and the driving current HPF10 is set low, the steering frequency component tends to remain, and when it is set high, the signal obtained through the steering torque HPF9 and the driving current HPF10 The phase shift of the oscillation component of the steering control system becomes large.
Therefore, the steering control of the signal obtained through the steering torque HPF9 and the drive current HPF10 is performed by setting the breakpoint frequency to any value within the range from the steering frequency band to the frequency band causing oscillation of the steering control system. The steering frequency component can be removed while leaving the oscillation component of the system.

Subsequently, the rotational speed observer 11 calculates a rotational speed estimation signal of the motor 2 based on the torque HPF signal and the current HPF signal (step S37).
In the integrating unit 12, the rotation speed estimation signal is integrated, the rotation angle of the motor 2 is calculated, and the rotation angle signal is output. (Step S38).

The auxiliary torque gradient detector 8 detects the auxiliary torque gradient from the auxiliary torque current-auxiliary torque gradient map based on the auxiliary torque current, and outputs an auxiliary torque gradient signal (step S39).
Next, the angle control unit 13 calculates an angle control current for controlling the steering angle based on the auxiliary torque gradient signal and the rotation angle signal (step S40).

Here, the angle control unit 13 that calculates the angle control current using the auxiliary torque gradient signal will be described in detail.
An auxiliary torque gradient signal and a rotation angle signal are input to the angle control unit 13. The angle control unit 13 calculates a gain corresponding to the auxiliary torque gradient signal, and multiplies the rotation angle signal by this gain to calculate an angle control current.

  Here, when the auxiliary torque gradient is high and the steering control system easily oscillates, the gain is set high and the angle control current increases, and the oscillation of the steering control system unpleasant to the driver is suppressed. On the other hand, when the auxiliary torque gradient is low, the gain is set low and the angle control current becomes small, and adverse effects such as torque unevenness are suppressed.

  Subsequently, in the adding unit 14, the auxiliary torque current and the angle control current are added, and a target current to be supplied to the motor 2 is calculated (step S41).

  According to the electric power steering control apparatus according to the first embodiment of the present invention, the steering torque HPF9 and the driving current HPF10 are used to remove the influence of the steering frequency accompanying the steering of the driver, and the angle control unit 13 performs the auxiliary torque gradient. Accordingly, when the auxiliary torque gradient is high, the gain is set high, and when the auxiliary torque gradient is low, the gain is set low and the angle control current is calculated. Uncomfortable steering wheel vibration can be suppressed.

Embodiment 2. FIG.
FIG. 3 is a block diagram showing an electric power steering control apparatus according to Embodiment 2 of the present invention.
In FIG. 3, the target current calculation means 3A calculates a damping current (correction current) for controlling the damping characteristic of the steering based on the auxiliary torque gradient signal and the rotational speed estimation signal (vibration suppression control). Means). Here, for the same type as in the first embodiment, “A” is appended after the same reference numeral, and detailed description thereof is omitted.

  Hereinafter, the operation of the electric power steering control apparatus 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.

An auxiliary torque gradient signal and a rotational speed estimation signal are input to the damping control unit 15. The damping control unit 15 calculates a gain corresponding to the auxiliary torque gradient signal, and multiplies the rotation speed estimation signal by this gain to calculate a damping current (step S61).
Subsequently, the adding unit 14 adds the auxiliary torque current, the angle control current, and the damping current, and calculates a target current to be supplied to the motor 2 (step S62).

  According to the electric power steering control device according to the second embodiment of the present invention, the influence of the steering frequency accompanying the steering of the driver is removed using the steering torque HPF9 and the driving current HPF10, and the angle control unit 13 and the damping control unit. When the auxiliary torque gradient is high, the gain 15 is set high, and when the auxiliary torque gradient is low, the gain is set low to calculate the angle control current and the damping current. The oscillation generated in the vehicle can be further suppressed, and unpleasant steering wheel vibration to the driver can be suppressed.

Embodiment 3 FIG.
5 is a block diagram showing an electric power steering control apparatus according to Embodiment 3 of the present invention.
In FIG. 5, the electric power steering control device includes a vehicle speed detector 16 (vehicle speed detection means) that detects the vehicle speed of the vehicle and outputs a vehicle speed signal.

Further, the torque control unit 7 has a steering torque / vehicle speed-auxiliary torque current map in which the relationship between the steering torque, the vehicle speed, and the auxiliary torque current is described, and steering based on the steering torque signal and the vehicle speed signal. The auxiliary torque current is calculated from the torque / vehicle speed-auxiliary torque current map.
The auxiliary torque gradient detection unit 8 has an auxiliary torque current / vehicle speed-auxiliary torque gradient map in which the relationship between the auxiliary torque current and the vehicle speed and the auxiliary torque gradient is described, and based on the auxiliary torque current and the vehicle speed signal. The auxiliary torque gradient is detected from the auxiliary torque current / vehicle speed-auxiliary torque gradient map, and an auxiliary torque gradient signal is output. Here, for the same type as in the second embodiment, “B” is appended after the same reference numeral, and detailed description thereof is omitted.

  Hereinafter, the operation of the electric power steering control apparatus having the above configuration will be described with reference to the flowchart of FIG. Note that description of operations similar to those of the second embodiment is omitted.

The vehicle speed detector 16 detects the vehicle speed and outputs a vehicle speed signal (step S74).
Further, the torque control unit 7B calculates an auxiliary torque current from the steering torque / vehicle speed-auxiliary torque current map based on the steering torque signal and the vehicle speed signal (step S75).
In addition, the auxiliary torque gradient detector 8B detects the auxiliary torque gradient from the auxiliary torque current / vehicle speed-auxiliary torque gradient map based on the auxiliary torque current and the vehicle speed signal, and outputs the auxiliary torque gradient signal (step S80). ).

  According to the electric power steering control apparatus according to Embodiment 3 of the present invention, since the auxiliary torque current and the auxiliary torque gradient are obtained using the vehicle speed signal, it is possible to perform control more suitable for the actual driving situation.

  In the first to third embodiments, the auxiliary torque current is obtained by map calculation based on the steering torque signal, and the angle control current is obtained by calculation by multiplying the rotation angle signal by the gain. However, the auxiliary torque current and the angle control current may both be a map calculation or a calculation that multiplies a gain. In this case, the same effect as described above can be obtained.

Moreover, in the said Embodiment 1-3, although the phase compensation part 6 was memorize | stored as software in the memory | storage part, you may be comprised only with hardware.
In this case, step S33 shown in FIG. 2 is not necessary.

The phase compensation unit may be a multi-stage phase compensation unit that is a combination of software and hardware.
In this case, step S31 shown in FIG. 2 does not take in the steering torque signal, but takes in the output of the analog phase compensation unit that compensates the phase of the steering torque signal.

Further, the auxiliary torque current may be directly obtained from the output of the torque sensor 1 without the phase compensation unit.
In this case, the step S33 shown in FIG. 2 is eliminated, and the step S34 obtains the auxiliary torque current from the output of the torque sensor 1.

In the first to third embodiments, the rotation speed estimation signal calculated by the rotation speed observer 11 is integrated by the integration unit 12 to calculate the rotation angle of the motor 2. However, the present invention is not limited to this. For example, the rotation angle may be detected using a motor rotation speed sensor such as an tacho generator.
In this case, step S32 shown in FIG. 2 detects the rotational speed of the motor 2, and step S36 passes the rotational speed of the motor 2 through a high-pass filter. Further, step S35 and step S37 are not necessary.

In the first to third embodiments, the rotational speed is estimated by the rotational speed observer 11. However, the present invention is not limited to this. For example, the motor rotational angle signal is detected by a motor rotational angle sensor such as a rotary encoder. And the motor rotation speed may be obtained from the motor rotation angle signal by differential processing.
In this case, step S32 shown in FIG. 2 detects the rotation angle of the motor 2, and step S36 passes the rotation angle of the motor 2 through a high-pass filter. Further, step S35 and step S37 are not necessary.

In the first to third embodiments, the auxiliary torque gradient is calculated from the auxiliary torque current value by the auxiliary torque gradient detecting unit 8 that holds the auxiliary torque current-auxiliary torque gradient map. The map of the auxiliary torque gradient may be calculated from the output of the phase compensator by the auxiliary torque gradient detector that holds the auxiliary torque gradient map.
In this case, step S39 shown in FIG. 2 calculates the auxiliary torque gradient from the output of the phase compensation unit.

In the first to third embodiments, the auxiliary torque gradient detecting unit 8 that holds the auxiliary torque current-auxiliary torque gradient map calculates the auxiliary torque gradient from the auxiliary torque current value. The auxiliary torque gradient detection unit that holds the auxiliary torque gradient map may perform map calculation of the auxiliary torque gradient from the torque sensor output.
In this case, step S39 shown in FIG. 2 calculates an auxiliary torque gradient from the steering torque signal.

In the first to third embodiments, the auxiliary torque gradient detection value is obtained by map calculation. Of course, the present invention is not limited to this, and the target current calculation means 3 is the previous value of the auxiliary torque current. May be calculated from the difference processing between the previous value of the auxiliary torque current and the auxiliary torque current.
In this case, the same effect as described above can be obtained.

In the first to third embodiments, the gain of the angle control current is variable according to the auxiliary torque gradient. However, the gain may be decreased when the auxiliary torque gradient is equal to or less than a predetermined threshold value.
At this time, if the angle control current and the damping current are larger than a predetermined threshold that is arbitrarily set, the angle control current and the damping current are set to an arbitrary first level. The damping current is set to a second level that is lower than the first level. Note that the first level and the second level can be changed while maintaining the mutual relationship.
In this case, even when the auxiliary torque gradient is low, the occurrence of torque unevenness can be further suppressed.

In the first to third embodiments, the gain of the angle control current is variable according to the auxiliary torque gradient. However, the gain may be set to 0 when the auxiliary torque gradient is equal to or less than a predetermined threshold value.
In this case, similarly to the above, even when the auxiliary torque gradient is low, the occurrence of torque unevenness can be further suppressed.

In the first to third embodiments, the steering torque HPF9 and the drive current HPF10 are arranged before the input of the rotational speed observer 11. However, the present invention is not limited to this, and the steering torque HPF9 and the drive current HPF10 are not limited thereto. May be inserted anywhere before the adder 14.
In this case, the same effect as described above 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 a flowchart which shows operation | movement of the electric power steering control apparatus which concerns on 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 electric power steering control apparatus which concerns on Embodiment 2 of this invention. It is a block diagram which shows the electric power steering control apparatus which concerns on Embodiment 3 of this invention. It is a flowchart which shows operation | movement of the electric power steering control apparatus which concerns on Embodiment 3 of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Torque sensor (steering torque detection means) 2 Motor 3 Target current calculation means 7 Torque control part (torque control means) 8 Auxiliary torque gradient detection part (auxiliary torque gradient detection means) 9 Steering torque HPF (steering component) Removal means), 10 drive current HPF (steering component removal means), 11 rotation speed observer (rotation speed detection means), 12 integration section (rotation angle detection means), 13 angle control section (vibration suppression control means), 14 addition section (Addition means), 15 damping control section (vibration suppression control means), 16 vehicle speed detector (vehicle speed detection means).

Claims (7)

Steering torque detection means for detecting steering torque by a driver of the vehicle;
A motor for generating an auxiliary torque for assisting the steering torque;
A target current calculation means for calculating a target current to be supplied to the motor based on at least the steering torque;
The target current calculation means calculates torque control means for calculating auxiliary torque current according to the auxiliary torque based on the steering torque;
Auxiliary torque gradient detecting means for detecting a gradient of the auxiliary torque, which is a gradient of the auxiliary torque current with respect to the steering torque, from the auxiliary torque current;
Steering component removing means for removing a frequency component accompanying steering of the driver;
Vibration suppression control means for calculating a correction current for suppressing vibration generated in the steering control system of the vehicle according to the auxiliary torque gradient;
An electric power steering control device comprising: an adding means for adding the auxiliary torque current and the correction current to calculate the target current. The target current calculation means includes a rotation speed detection means for detecting the rotation speed of the motor,
The electric power steering control device according to claim 1, wherein the vibration suppression control unit calculates the correction current based on the rotation speed. The target current calculation means includes a rotation angle detection means for detecting a rotation angle of the motor,
The electric power steering control device according to claim 1, wherein the vibration suppression control unit calculates the correction current based on the rotation angle.   The vibration suppression control means sets the correction current to the first level when the auxiliary torque gradient is greater than a predetermined threshold value, and the auxiliary torque gradient is less than or equal to the threshold value. 4. The electric power steering control device according to claim 1, wherein the correction current is set to a second level lower than the first level. .   The electric power steering control device according to claim 4, wherein the vibration suppression control unit sets the second level to zero. Vehicle speed detecting means for detecting the speed of the vehicle,
6. The auxiliary torque gradient detection unit includes an auxiliary torque gradient map for calculating the auxiliary torque gradient from at least one of the steering torque and the vehicle speed of the vehicle. The electric power steering control device according to claim 1.   The auxiliary torque gradient detecting means includes a previous torque value storage means for storing the steering torque and a previous detected value of the auxiliary torque, and a difference between the steering torque and the current detected value of the auxiliary torque and the previous detected value. The electric power steering control device according to any one of claims 1 to 6, wherein the auxiliary torque gradient is calculated on the basis of the auxiliary torque gradient.

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