JP2003320951A - Motor control device of electric power steering device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent the occurrence of a difference in steering torque upon steering to the left and right on a vehicle in the midst of travelling even in the case when an offset error exists in the steering torque detected by a torque sensor upon a steering wheel to the left and right. <P>SOLUTION: Whether a steering angle θ is in a neutral steering state or not is judged while a vehicle travels at velocity V at which self alignment torque works on a front wheel. Thereafter, a torque detection value Tsp of a torque sensor in the neutral steering state when the vehicle is steered right or steered left in a steering angle speed area where steering reaction force is generated only by roughly the maximum static friction force of a steering system, is respectively acquired. An LPF after correction torque value Tn is provided by noise-removing the torque detection value Tsp, and a left and right average torque value Tm of right and left steering neutral torque values Tr. Tl annealing and treating this LPF after correction torque value Tn is found. A correction steering torque Ts* correcting the torque detection value Tsp is provided by using a torque offset value Tos annealing and treating the left and right average torque value Tm. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a motor control device for an electric power steering device which detects a steering torque applied to a steering wheel by a torque sensor and controls an assist torque supplied by an electric motor based on the detected torque value. It is about.

[0002]

2. Description of the Related Art Conventionally, in an electric power steering apparatus that assists steering of a steering wheel by the power of an electric motor, for example, the assist torque of the motor is based on the steering torque detected by a torque sensor and the vehicle speed detected by a vehicle speed sensor. Steering assist control for controlling

In this steering assist control, the assist torque is set based on the steering torque and the vehicle speed, and the motor is feedback-controlled so as to generate this assist torque.

The assist torque is shown in FIG.
As indicated by the chain double-dashed line, the same steering torque value Ts1 is set to the same magnitude during right steering and left steering.

Therefore, as shown by the chain double-dashed line in FIG.
The required value (absolute value) of the steering torque Ts becomes equal to the same steering steering angle value θ1 during rightward steering and leftward steering while the vehicle is traveling. It should be noted that this steering torque-steering angle characteristic is the reverse steering force based on the self-alignment torque acting on the steered wheel with respect to a certain steering steering angle value θ1 in a vehicle traveling at a certain vehicle speed at which the self-alignment torque acts on the steered wheel. On the other hand, the required steering torque Ts is shown.

[0006]

However, as shown by the solid line in FIG. 4, there is an offset error in the actual torque sensor, and the output value corresponding to the same steering torque value Ts1 during right steering and left steering. Difference occurs. Further, this offset error varies among the individual sensors and also drifts with a change in temperature.

When a torque sensor having an offset error is used in this way, as shown by the solid line in FIG. 5, an assist generated for the same steering torque value Ts1 during right steering and left steering. A difference occurs in the torque Ta.

As a result, as shown in FIG. 7, there is a difference in the value of the steering torque Ts required for the same steering steering angle θ between right steering and left steering in the running vehicle. It will give the driver a feeling of strangeness.

The present invention has been made to solve the above problems, and its object is to provide an offset error in the steering torque detected by the torque sensor during right steering and left steering of the steering wheel. An object of the present invention is to provide a motor control device of an electric power steering device that can prevent a difference in steering torque between left and right steering wheels in a running vehicle.

[0010]

In order to solve the above-mentioned problems, the invention according to claim 1 uses an assist torque generated by an electric motor as a detection value of a torque sensor for detecting a steering torque applied to a steering wheel. In a motor control device for an electric power steering device that is controlled by using the self-alignment torque on the steered wheels when the steering wheel is steered to the right when the vehicle speed is in a vehicle speed range where the self-alignment torque is applied to the steered wheels. The intermediate value between the detected value of the steering torque in the neutral steering state where it does not work at the time of right steering and the detected value of the steering torque at the time of left steering at the time of left steering at the steering angular velocity almost equal to that of right steering, The steering torque detection value is corrected using this intermediate value as the steering torque offset error, and the corrected torque detection value is used. And controlling the assist torque Te.

According to the first aspect of the present invention, when the vehicle speed of the running vehicle is in the vehicle speed range where the self-aligning torque is applied to the steered wheels, the steering torque required for steering the steering wheel is self-aligned. In addition to reverse steering force due to torque, steering reaction force due to friction resistance of the steering system,
Further, it is generated in opposition to the steering reaction force due to the viscous resistance of the steering system. On the other hand, when the vehicle speed range where the self-alignment torque does not almost work or the vehicle is stopped, the steering torque is the steering reaction force due to the road surface resistance received by the steered wheels,
It is generated against the steering reaction force due to the frictional resistance of the steering system and the steering reaction force due to the viscous resistance of the steering system.

Even in the vehicle speed range where the self-alignment torque is applied to the steered wheels, the steering torque when the steering angle is in the neutral steering state in which the self-alignment torque does not substantially act on the steered wheels is the steering reaction due to the friction resistance of the steering system. Power,
Further, it is generated in opposition to the steering reaction force due to the viscous resistance of the steering system. Further, the frictional resistance of the steering system is classified into static friction that acts when the steering wheel is not steered and kinetic friction that acts when the steering wheel is steered. The magnitude of the frictional resistance due to static friction changes according to the steering torque actually applied to the steering wheel, and the magnitude of the frictional resistance due to kinetic friction is substantially constant regardless of the steering angular velocity. Further, the viscous resistance acts when the steering wheel is steered, but is sufficiently smaller than the frictional resistance in a predetermined region where the steering angular velocity is low, but as the steering angular velocity increases, the steering reaction force along with the frictional resistance increases. To generate.

When the steering wheel is steered in the predetermined steering angular velocity range in which the frictional resistance is generated only by the kinetic friction, the steering torque in the neutral steering state is substantially equal in the right steering and the left steering. Although the steering reaction force due to the viscous resistance changes in magnitude according to the steering angular velocity of the steering wheel, when the steering angular velocity of the right steering and the left steering are almost equal, the steering torque in the neutral steering state is And when steering to the left are almost equal.
Further, when the vehicle speed is in a range where the self-alignment torque does not substantially work or the vehicle is stopped, the steering torque in the neutral steering state when the steering angle is steered depends on the steering angular velocity at that time. Different sizes. Therefore, if there is no offset error in the torque sensor, the detected value of the steering torque in both the right steering and the left steering when the vehicle is traveling at the vehicle speed at which the self-alignment torque acts on the steered wheels Are almost equal.

On the other hand, if there is an offset error in the torque sensor, the detected values of both steering torques in the neutral steering state shift together by the amount corresponding to the offset error. At this time, when one of the right steering detection value of the steering torque during right steering and the left steering detection value of the steering torque during left steering increases by the offset error, the other of the two detection values becomes the offset error. Get smaller.

Therefore, the intermediate value between the detected values of both steering torques in the neutral steering state at the time of right steering and left steering corresponds to the offset error of the steering torque corresponding to the offset error of the torque sensor. Therefore, if the detected value of the steering torque is corrected using the calculated offset error, the offset error of the steering torque based on the offset error of the torque sensor is removed.

According to the second aspect of the present invention, there is provided a motor control device for an electric power steering system, wherein an assist torque generated by an electric motor is controlled by using a detection value of a torque sensor for detecting a steering torque applied to a steering wheel. The steering angle determination means for determining whether or not the steering steering angle is in a neutral steering state in which the self-aligning torque hardly acts on the steered wheels, and the vehicle speed is a vehicle speed range in which the self-aligning torque acts on the steered wheels. A vehicle speed determining means for determining whether or not the steering wheel is in the right steering or a steering direction determining means for determining whether or not the steering wheel is in the left steering, and the vehicle speed is in the vehicle speed range. In addition, when the steering wheel is steered to the right, the steering torque in the neutral steering state at the time of steering to the right is almost equal to the steering value to the right. A correction value acquisition unit that obtains an intermediate value between the steering torque in the neutral steering state when the vehicle is steered to the left at a speed and the detected value during left steering, and the detected value of the steering torque with the intermediate value as an offset error of the steering torque The assist torque is controlled by using a correction torque detection value corrected by the correction means.

According to the invention of claim 2, claim 1
The same effect as the invention described in (1) can be obtained. According to a third aspect of the present invention, in the invention according to the second aspect, the correction value acquisition means is such that the steering angular velocity of the steering wheel is such that the steering reaction force generated by the steering is substantially dependent on the friction resistance of the steering system. Steering angular velocity determination means for determining whether or not it is in the generated steering angular velocity range, and a right steering detection value of the steering torque in the neutral steering state when steering to the right at a steering angular velocity in the steering angular velocity range, Similarly, it is characterized by comprising an intermediate value obtaining means for obtaining an intermediate value between the steering torque in the neutral steering state and the detected value during left steering when the steering wheel is steered to the left at the steering angular velocity in the steering angular velocity range.

According to the invention of claim 3, claim 2
In addition to the operation of the invention described in (1), in the vehicle speed range where the self-alignment torque does not substantially act on the steered wheels, the steering reaction force is almost due to the friction resistance of the steering system. When the wheel is steered, the steering reaction force due to the frictional resistance in the neutral steering state is almost equal between right steering and left steering. Therefore, even if the steering angular velocity during right steering is not substantially equal to the steering angular velocity during left steering, both steering torques in the neutral steering state are substantially equal within the predetermined steering angular velocity range. Therefore,
Since the opportunity to acquire the detected value of the steering torque in the neutral steering state at the time of right steering and left steering is expanded, the offset error of the steering torque based on the offset error of the torque sensor can be acquired more quickly.

According to a fourth aspect of the invention, in the invention of the second or third aspect, the correction value acquisition means is
When the vehicle speed is in the vehicle speed range, when the steering wheel is steered to the right, the steering torque in the neutral steering state when the steering wheel is steered to the left at a steering angular velocity that is substantially equal to the detection value when steering to the right, Sequentially obtaining an intermediate value between the steering torque in the neutral steering state and the detected value during left steering, the correction means
The detected value of the steering torque is sequentially corrected by using the newly obtained intermediate value as an offset error of the steering torque.

According to the invention of claim 4, claim 2
Alternatively, in addition to the effect of the invention described in claim 3, the offset error of the steering torque according to the latest offset error of the torque sensor is detected, and the detected value of the steering torque is corrected based on this offset error. Therefore, even if the offset error of the torque sensor fluctuates due to temperature drift or the like while the vehicle is traveling, the detected value of the steering torque is correctly corrected. As a result, it is possible to more reliably prevent a difference in steering torque between the running vehicles during left-right steering.

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment in which the present invention is embodied in a column assist type electric power steering apparatus will be described below with reference to FIGS.

As shown in FIG. 2, the electric power steering device 10 includes a motor control device 11 and a motor drive device 1.
2, an electric motor (hereinafter abbreviated as a motor) 13, a torque sensor 14, a vehicle speed sensor 15, a steering angle sensor 16,
The current sensor 17 and the like are used. In the present embodiment, the motor control device 11 is the steering angle determination means, the vehicle speed determination means, the steering direction determination means, the correction value acquisition means, the correction means, the steering angular velocity determination means, and the intermediate value acquisition means.

The torque sensor 14 detects the steering torque Ts applied to the steering wheel 20 from the torsion of the torsion bar 19 provided on the steering shaft 18, and outputs it to the motor control device 11. As shown by the chain double-dashed line in FIG. 4, the torque sensor 14 outputs a voltage signal that is substantially directly proportional to the steering torque Ts applied to the steering wheel 20 in accordance with right steering and left steering.

The vehicle speed sensor 15 detects the vehicle speed V from the rotation of the front wheels 28 and outputs it to the motor control device 11. The steering angle sensor 16 detects the steering angle θ of the steering wheel 20 and outputs it to the motor control device 11.
The current sensor 17 detects a motor current Id that changes according to the operating state of the motor 13 and outputs it to the motor control device 11.

The motor control device 11 is composed of a microcomputer, and based on the steering torque Ts, the vehicle speed V, the steering steering angle θ, and the motor current Id, the motor control signal I.
m is generated and output to the motor drive device 12.

The motor driving device 12 receives the motor control signal Im.
The motor 13 is driven and controlled based on The motor 13 is
Reduction gear 21 fixed to steering shaft 18
Are driven by the drive gear 22 fixed to the rotation shaft.
When the steering shaft 18 rotates along with the steering of the steering wheel 20, the pinion shaft 23 fixed to the reduction gear 21 integrally rotates, and the pinion gear 24 fixed to the tip of the pinion shaft 23 moves the rack 25.
Operate. The rack 25 rotates a knuckle 27 via a tie rod 26 and steers a front wheel 28 supported by the knuckle 27.

When the motor 13 rotates, the rotation is transmitted to the pinion shaft 23 via the reduction gear 21 and to the rack 25 via the pinion gear 24. Then, when the motor 13 is driven when the steering wheel 20 is steered, in addition to the steering force due to the steering torque Ts applied to the steering wheel 20,
The front wheels 28 are steered by the steering force by the assist torque supplied by the motor 13.

Next, the motor control device 11 will be described with reference to the block diagram of FIG. The motor control device 11 includes a torque correction unit 30, an assist torque calculation unit 31, a command current setting unit 32, a torque control unit 33, a motor control unit 34, a subtraction unit 35, and the like. Of these, the torque correction unit 30 is a novel component of the present invention, but the remaining components except the torque correction unit 30 are known.

The torque correction unit 30 generates a corrected steering torque (corrected torque detection value) Ts * obtained by correcting the steering torque Ts detected by the torque sensor 14 based on the vehicle speed V and the steering angle θ. This corrected steering torque Ts *
Is obtained by removing the offset error of the torque sensor 14 from the steering torque Ts. The torque correction unit 30 will be described in detail later.

The assist torque calculation unit 31 calculates the assist torque (target assist torque) Ta based on the corrected steering torque Ts * and the vehicle speed V. Assist torque Ta
Is set according to the vehicle speed V, and is set so as to progressively increase with a certain vehicle speed V as the steering torque Ts increases due to right steering or left steering, as shown in FIG. . Further, for a certain vehicle speed V, the same assist torque Ta is set for the same steering torque Ts during right steering and left steering.

The command current setting unit 32 uses the assist torque T
The command motor current Im * is set based on a. The subtraction unit 35 obtains a current difference value ΔIm between the command motor current Im * and the motor current Id.

The torque control unit 33 generates a motor voltage signal Vm based on the current difference value ΔIm by known feedback control such as PI control so that the motor current Id approaches the command motor current Im *.

The motor controller 34 controls the motor voltage signal Vm.
The motor control signal Im is generated based on the above, and is output to the motor drive device 12. The motor control device 11 configured as described above performs steering assist control for controlling the torque generated by the motor 13 to the assist torque Ta based on the steering torque Ts and the vehicle speed V.

By this steering assist control, the steering torque T with respect to the steering steering angle θ in the vehicle traveling at the vehicle speed V at which the self-aligning torque acts on the front wheels 28.
s changes as shown by the chain double-dashed line in FIG.

This is because the front wheels 2 in the steering state while the vehicle is traveling.
8 of the total steering force that balances the reverse steering force based on the self-aligning torque applied in a magnitude corresponding to the front wheel steering angle (slip angle) with respect to the steering steering angle θ of the steering torque Ts applied to the steering wheel 20. Show the relationship.

The self-alignment torque has a characteristic that it increases as the steering angle θ increases. Therefore, the steering torque Ts is the result of the assist torque Ta set with respect to the steering torque Ts as shown in FIG.
The characteristic is such that the larger the steering steering angle θ approaches “0”, the smaller the steering steering angle θ (absolute value) changes.

In practice, this steering torque-steering angle characteristic has a hysteresis based on the static friction force of the steering system, as shown by the solid line in FIG. That is, as the steering wheel 20 is steered, a steering reaction force in the direction opposite to the steering is generated by the frictional resistance of the steering system, and the steering torque Ts with respect to this frictional resistance is generated. As a result, even when the steering steering angle θ is in the neutral steering state in which the slip angle of the front wheels 28 is almost “0” and the self-alignment torque does not act on the front wheels 28, the steering angle θ is associated with the right steering and the left steering. Steering torque T in the neutral steering state
s is required. Steering torque Ts in this neutral steering state
Are almost equal during right steering and left steering. this is,
This is because the friction resistance of the steering system is substantially equal during right steering and left steering.

In a vehicle running at a vehicle speed V in which the self-alignment torque acting on the front wheels 28 is sufficiently smaller than the frictional resistance of the steering system, or in a stopped vehicle, the steering torque Ts with respect to the steering angle θ. The characteristics of
As shown in FIG. 8, it becomes almost constant regardless of the steering angle θ. This is because the steering reaction force generated by the steering of the steering wheel 20 is almost due to the frictional resistance with the road surface, and this frictional resistance is substantially constant regardless of the steering angle θ. Also,
In this state, when the steering wheel 20 is steered from a certain steering angle θ, the steering torque Ts is
As shown in FIG. 8, it rises from “0” regardless of the steering angle θ. Therefore, the steering angle θ
Is 0, the steering torque Ts has a different value depending on the steering angle θ at which steering is started.

Further, the steering torque-steering angle characteristic has a hysteresis based on the viscous resistance of grease or the like in the steering system, as shown by the broken line in FIG. Unlike the hysteresis based on the frictional resistance, this hysteresis increases as the steering angular velocity of the steering wheel 20 increases.

Here, if the torque sensor 14 has an offset error, for example, as shown by the solid line in FIG. 4, there is a difference between the output values for the same steering torque value Ts1 during right steering and left steering. Therefore, the relationship of the assist torque Ta generated with respect to the steering torque Ts is biased as shown by the solid line in FIG. 5, and the value of the assist torque Ta generated with respect to the same steering torque value Ts1 is changed to the right steering. There is a difference between time and left steering.

As a result, as shown in FIG. 7, the steering torque-steering angle characteristics are biased, and the same steering steering angle value θ1 is obtained.
On the other hand, the required value of the steering torque Ts can differ between right steering and left steering.

The torque correction unit 30 detects the steering torque Ts detected in the neutral steering state when the steering wheel 20 is steered to the right, and the steering value in the neutral steering state when the steering wheel 20 is steered to the left. The average value (intermediate value) of the torque Ts and the detected value during left steering is calculated. Then, the steering torque Ts is determined by using this average value as an offset error of the steering torque.
Correct the detected value of.

The torque correction unit 30 is in the steering angular velocity range in which the steering reaction force generated by the steering of the steering wheel 20 is generated only by the friction resistance of the steering system based on the steering steering angle θ and the vehicle speed V. Or not. Then, the right steering detection value of the steering torque Ts in the neutral steering state when the vehicle is steered to the right in the range of the steering angular velocity range, and the neutral steering state when the vehicle is steered to the left in the range of the steering angular velocity range as well. The average value of the steering torque Ts and the detected value during left steering is calculated.

Next, the steering torque correction processing performed by the motor control device 11 as the torque correction unit 30 will be described in detail.
In the steering torque correction processing, as shown in FIG.
At 100, the steering torque Ts detected by the torque sensor 14
LPF from which noise is removed by performing low-pass filter (LPF) processing on the detected torque value Tsp of
The post-correction torque value Tn is calculated.

Tn = Tsp · α + (1-α) T (n-1) (1) T (n-1): LPF corrected torque value α obtained in the previous process α: LPF time constant Next, S101 And the steering angle θ at that time
However, it is determined whether or not the self-aligning torque is not substantially applied to the front wheels 28 during the traveling of the vehicle within the range of the neutral steering state of −5 ° <θ <+ 5 °. The range of the neutral steering state is not limited to −5 ° <θ <+ 5 °, and may be a narrower range of ± 2 or ± 3, for example.

If an affirmative decision is made in S101, then S
At 102, the vehicle speed V at that time is the steering angle θ.
Regardless of the above, it is determined whether or not the vehicle speed range up to 20 km / h at which the self-aligning torque does not substantially act on the front wheels 28 is exceeded.

If an affirmative decision is made in S102, then S
At 103, the steering direction and the steering angular velocity ω are obtained from the rate of change of the steering angle θ, and the steering wheel 20 is operated at 1 rad / sec. <Ω <1.5 rad / se
c. It is determined whether or not the vehicle is being steered to the right at a steering angular velocity ω within the steering angular velocity range. The steering angular velocity range is a range in which the steering reaction force generated by the steering of the steering wheel 20 is generated only by the frictional resistance of the steering system. Further, in this steering angular velocity range, the behavior of the vehicle becomes stable, and the steering reaction force in the neutral steering state does not depend on the self-alignment torque.

If an affirmative decision is made in S103, then S
At 104, the corrected torque value T after LPF is calculated using the following equation (2).
A right steering neutral torque value (detection value at the time of right steering) Tr obtained by smoothing n is obtained, and then S107 is executed.

Tr = β · Tn + (1-β) · T (r-1) (2) T (r-1): previous right steering neutral torque value β: vehicle speed by the processing of forgetting factors S100 to S104 In the vehicle operating state where V is the vehicle speed range in which the self-alignment torque is applied to the front wheels 28, the right steering neutral torque value Tr of the steering torque Ts in the neutral steering state when the steering wheel 20 is steered to the right is obtained. This right steering neutral torque value Tr
Is a detected value of the steering torque Ts with respect to the steering reaction force generated only by the frictional resistance of the steering system in the neutral steering state during right steering.

On the other hand, when a negative decision is made in S103,
Next, in S105, the steering direction and the steering angular velocity ω are obtained from the rate of change of the steering angle θ, and the steering wheel 20 is operated at 1 rad / sec. <Ω <1.5 rad
/ Sec. Steering angular velocity ω within the steering angular velocity range of
It is determined whether or not the vehicle is being steered to the left.

If the determination in S105 is affirmative, then S
At 106, the corrected torque value T after LPF is calculated using the following equation (3).
A left steering neutral torque value (detection value during left steering) Tl obtained by smoothing n is obtained, and then S107 is executed.

Tl = β · Tn + (1-β) · T (l-1) (2) T (l-1): previous left steering neutral torque value β: forgetting factors S100 to S102, S105, S106 By the processing, the left steering neutral torque value Tl of the steering torque Ts in the neutral steering state when the steering wheel 20 is steered to the left in the operating state of the vehicle in which the vehicle speed V is the vehicle speed range in which the self-alignment torque is applied to the front wheels 28. Ask. The left steering neutral torque value Tl is a detected value of the steering torque Ts with respect to the steering reaction force generated only by the friction resistance of the steering system in the neutral steering state during left steering.

At S107, the right and left average torque value (intermediate value) of the right steering neutral torque value Tr and the left steering neutral torque value Tl.
Tm is calculated by the following equation (4). Tm = (Tr + Tl) / 2 (4) In S108 after S107, the torque offset value T obtained by smoothing the left-right average torque value Tm using the following equation (5) is used.
ask for os.

Tos = γ · Tm + (1-γ) T (os-1) (5) T (os-1): Previous torque offset value γ: Forgetting coefficient and right steering neutral by the processing of S107 and S108. The torque offset value Tos obtained from the left and right average torque value Tm of the torque value Tr and the left steering neutral torque value Tl is taken as the offset error of the steering torque Ts.

In S109 following S108, the corrected steering torque Ts * obtained by adding the torque offset value Tos to the detected torque value Tsp is calculated by the following equation (6). Ts * = Tsp + Tos (6) Next, the effects of the present embodiment described above will be listed.

(1) When the steering wheel 20 is steered to the right or left in a vehicle traveling at a vehicle speed V at which the self-alignment torque acts on the front wheels 28, the steering torque Ts in the neutral steering state in which the self-alignment torque does not act. Detected torque value Tsp (right steering neutral torque value T
r and the left steering neutral torque value Tl) are respectively acquired. Each steering torque Ts at this time has a magnitude necessary for the steering reaction force generated only by the frictional resistance of the steering system.

A left and right average torque value (intermediate value) Tm of the detected values of both steering torques Ts is obtained, and a value obtained by smoothing the left and right average torque value Tm is used as a torque offset value (offset error) Tos of the steering torque Ts. The detected torque value Tsp is corrected.

The assist torque Ta of the motor 13 is controlled based on the corrected steering torque Ts *. As a result, even if there is an offset error in the steering torque Ts detected by the torque sensor 14 during steering of the steering wheel 20 to the right and to the left, it is unlikely that there will be a difference between the steering torque Ts of the running vehicle during left-right steering. Can be Therefore, for example, the driver is unlikely to feel uncomfortable when steering.

(2) It is detected that the steering angular velocity ω of the steering wheel 20 is within the steering angular velocity range in which the steering reaction force generated by the steering is generated only by the frictional resistance of the steering system. The left and right of the torque detection value Tsp (right steering neutral torque value Tr, left steering neutral torque value Tl) in the respective neutral steering states when the steering wheel 20 is steered right and left in the range of the steering angular velocity range. The average torque value Tm is calculated.

Therefore, even if there is a difference in the steering angular velocity ω in the neutral steering state between the right steering and the left steering, if the steering angular velocity range is within the predetermined range, the actual steering in the neutral steering state is performed. The torque Ts becomes almost equal.

Therefore, the opportunities to acquire the torque detection value Tsp in the neutral steering state at the time of right steering and left steering are expanded, so that the offset error of the steering torque Ts based on the offset error of the torque sensor 14 can be eliminated more quickly. be able to.

(3) The steering steering angle θ is in the neutral steering state, and the self-alignment torque is the front wheel 2
Each time a condition that is a vehicle speed range that can work in 8 is satisfied, a new left-right average torque value Tm and a torque offset value are calculated from the detected torque value Tsp of the steering torque Ts in the neutral steering state when the vehicle is steered to the right and to the left. Tos was sequentially obtained. Then, the newly obtained torque offset value To
The torque detection value Tsp is corrected using s.
Therefore, while the vehicle is traveling, the torque sensor 14 at that time is
The torque offset value Tos of the steering torque Ts corresponding to the offset error is acquired, and the torque detection value Tsp is corrected using this new torque offset value Tos.

Therefore, even if there is a temperature drift in the offset error of the torque sensor 14, it is possible to prevent the steering torque Ts of the running vehicle from being different between the left and right steering directions.

Next, embodiments other than the above-mentioned one embodiment will be listed. In the above-described embodiment, the neutral torque correction process performed by the motor control device 11 as the torque correction unit 30 is performed by using a fixed torque offset value Tos preset for each individual torque sensor 14 The processing content is to correct the detected value of the steering torque Ts output by the controller 14. In this case, in addition to the effects described in (1) and (2) of the first embodiment, when the temperature drift of the offset error of the torque sensor 14 is not so large, the steering torque Ts with respect to the steering angle θ is changed. It is possible to prevent the difference between the right steering and the left steering from occurring easily.

In the neutral torque correction processing of the one embodiment, the steering angular velocity ω when the steering wheel 20 is steered to the right or left is the steering reaction force generated by the steering applied to the friction resistance of the steering system. Then, it is determined whether or not the steering angular velocity range is also generated by the viscous resistance of the steering system due to the lubricating grease or the like. When the steering angular velocity ω is within the range of the steering angular velocity range, the right steering neutral torque value Tr is changed according to the steering direction.
Alternatively, the left steering neutral torque value Tl is generated. Next, the steering torque T in the neutral steering state when steering in the opposite direction at the steering angular velocity ω equal to the steering angular velocity ω
A right steering neutral torque value Tr or a left steering neutral torque value Tl is generated from the detected value of s. Then, from the right steering neutral torque value Tr and the left steering neutral torque value Tl generated when the steering wheel is steered right and left at the same steering angular velocity ω, the left and right average torque value Tm and the torque offset value Tos are obtained.
To generate. In the case of such a configuration, there are the respective effects described in (1) and (2) of the one embodiment.

In the above embodiment, the steering wheel 20 may acquire the neutral steering state, the steering direction, and the steering angular velocity from the detection value of the steering angle sensor that detects the steering angle of the front wheels 28.

In the one embodiment, the motor control device 11 calculates the vehicle speed from the acceleration of the vehicle detected by the acceleration sensor. The type of the electric power steering device embodying the present invention is not limited to the column assist type, but may be the rack assist type or the pinion assist type.

The technical idea understood from each of the above embodiments will be described below. (1) In the invention according to any one of claims 1 to 4, the steering steering angle in the neutral steering state is an angle range of 5 ° to the left and right, and a motor for an electric power steering apparatus. Control device.

(2) In the invention according to any one of claims 1 to 4, the vehicle speed range is 20 km / h.
A motor control device for an electric power steering device, which is in the above vehicle speed range.

(3) In the invention described in claim 3,
The steering angular velocity range is 1 rad / sec. Over 1.5 rad / sec. A motor control device for an electric power steering device having an angular velocity range of less than 1.

(4) A motor control device for an electric power steering apparatus according to any one of claims 1 to 4 or any one of technical ideas (1) to (3), and an electric motor. Electric power steering including a motor (13), a torque sensor (14) that detects a steering torque (Ts), a steering angle sensor (16) that detects a steering angle (θ), and a vehicle speed sensor (15). apparatus.

[0072]

According to the invention described in claims 1 to 4, even when the steering torque detected by the torque sensor has an offset error when steering the steering wheel to the right and to the left, the vehicle that is traveling is running. It is possible to make it difficult for a difference in steering torque between the left and right steering wheels to occur.

[Brief description of drawings]

FIG. 1 is a flowchart showing a steering torque correction process performed by a motor control device of an electric power steering device according to an embodiment.

FIG. 2 is a schematic configuration diagram showing an electric power steering device.

FIG. 3 is a block diagram of a motor control device.

FIG. 4 is a graph showing an output-steering torque characteristic of a torque sensor.

FIG. 5 is a graph showing assist torque-steering torque characteristics.

FIG. 6 is a graph showing steering torque-steering angle characteristics.

FIG. 7 is a graph showing steering torque-steering angle characteristics.

FIG. 8 is a graph showing steering torque-steering angle characteristics.

[Explanation of symbols]

10 ... Electric power steering device, 11 ... Steering angle determination means, vehicle speed determination means, steering direction determination means, correction value acquisition means, correction means, steering angular velocity determination means and intermediate value acquisition means, 13 ... Electric motor , 14 ... Torque sensor, 15 ... Vehicle speed sensor, 16 ... Steering angle sensor,
20 ... Steering wheel, 28 ... Front wheel as steering wheel, 30 ... Torque correction unit, Ta ... Assist torque, Tm
... left / right average torque value as an intermediate value, Tl ... left steering neutral torque value as a detected value during left steering, Tr ... right steering neutral torque value as a detected value during right steering, Ts ... steering torque, T
s * ... corrected steering torque as a corrected torque detection value, V ...
Vehicle speed, θ ... Steering angle, ω ... Steering angular velocity.

Claims (4)

[Claims] 1. A motor control device of an electric power steering system, wherein an assist torque generated by an electric motor is controlled by using a detection value of a torque sensor for detecting a steering torque applied to a steering wheel. When the steering wheel is steered to the right when the self-alignment torque is in the vehicle speed range, the detected value of the steering torque at the time of the right steering in the neutral steering state in which the self-alignment torque hardly acts on the steered wheels,
An intermediate value between the steering torque in the neutral steering state and the detected value during left steering when the steering wheel is steered to the left at a steering angular velocity substantially equal to that to the right steering, and the steering torque is detected as an offset error of the steering torque. A motor control device for an electric power steering device, wherein a value is corrected and the assist torque is controlled by using the corrected torque detection value. 2. A motor control device for an electric power steering system, wherein an assist torque generated by an electric motor is controlled by using a detection value of a torque sensor for detecting a steering torque applied to a steering wheel. Steering angle determination means for determining whether or not the steering wheel is in a neutral steering state in which the self-aligning torque does not substantially act, and vehicle speed for determining whether or not the vehicle speed is in a vehicle speed range in which the self-aligning torque is applied to the steered wheels. The judging means and whether or not the steering wheel is being steered to the right, or
Steering direction determination means for determining whether or not left steering is in progress, and right steering detection value of steering torque in the neutral steering state when the steering wheel is steered to the right when the vehicle speed is in the vehicle speed range. And a correction value acquisition means for obtaining an intermediate value between the steering torque in the neutral steering state and the detected value during left steering when the steering wheel is steered to the left at a steering angular velocity substantially equal to that of the right steering, and the intermediate value is an offset error of the steering torque. And a correction unit that corrects the detected value of the steering torque, and the assist torque is controlled using the corrected torque detection value that is corrected by the correction unit. 3. The correction value acquisition means determines whether or not the steering angular velocity of the steering wheel is in a steering angular velocity range in which a steering reaction force generated by steering is generated only by friction resistance of the steering system. A steering angular velocity determination means, a steering torque detection value in the neutral steering state when the vehicle is steered to the right at a steering angular velocity in the steering angular velocity range, and a steering angle velocity in the steering angular velocity range is left-steered. The motor control device for an electric power steering device according to claim 2, further comprising: an intermediate value acquisition unit that obtains an intermediate value between the steering torque in the neutral steering state and the detected value during left steering. 4. The correction value acquisition means, when the vehicle speed is in the vehicle speed range, when the steering wheel is steered to the right, the detected value of steering torque in the neutral steering state at the time of right steering, and at the time of right steering. Sequentially obtaining an intermediate value between the steering torque in the neutral steering state and the detected value at the time of left steering when the steering wheel is steered to the left at a steering angular velocity substantially equal to, and the correction means sets the newly obtained intermediate value to the offset of the steering torque. The motor control device of the electric power steering device according to claim 2 or 3, wherein the detected value of the steering torque is sequentially corrected as an error.