JP6000222B2 - Steering control device and steering control method - Google Patents

Description

  The present invention relates to a steering control device and a steering control method that compensate for a friction equivalent component when performing steering torque control.

  Compensation of the friction equivalent component when steering torque control is performed by the steering control device changes the direction of torque application based on the sign of the rotational angular velocity of the steering shaft, as in the case of mechanical friction. Therefore, when the driver holds the steering wheel at a constant angle and the rotational angular velocity is close to zero, if the sign of the rotational angular velocity of the steering shaft changes repeatedly due to minute vibrations, etc. The direction in which compensation torque is applied may change, resulting in unpleasant vibration of the steering wheel.

  Therefore, in order to prevent the occurrence of such steering wheel vibration, by providing a dead zone in which the rotational angular velocity of the steering shaft is set to zero within a predetermined range near zero of the rotational angular velocity, the compensation torque for the friction equivalent component operates. There is known a steering control device that prevents this from occurring (see, for example, Patent Document 1).

JP 2007-137287 A

However, the prior art has the following problems.
In the conventional steering control device, in particular, when the rotational angular velocity is calculated by differentiating the detected value of the rotational angle sensor of the steering shaft without using the rotational angular velocity sensor of the steering shaft for cost reduction, the rotational angle sensor signal is used. The noise superimposed on is also differentiated. For this reason, the amplitude of the noise equivalent component of the rotational angular velocity becomes larger than the width of the dead zone, the dead zone effect becomes weak, and there is a problem that the steering wheel vibration cannot be sufficiently suppressed.

  In addition, if the dead zone width is set to be sufficiently larger than the amplitude of the noise equivalent component of the rotational angular velocity, the friction equivalent component compensation does not operate when the driver steers slowly, and the driver feels uncomfortable. There is also a problem of giving.

  When a low-pass filter is introduced to reduce the influence of noise, the compensation amount of the friction equivalent component rises with time regardless of the steering speed by the driver. Therefore, for example, when the driver turns the steering wheel up to a certain angle and then turns it back at an extremely slow speed to the extent that it can be assumed that the steering wheel is held at that angle, the steering wheel angle However, there is also a problem that the steering torque changes despite the fact that it is almost constant, giving the driver a sense of incongruity.

  The present invention has been made in order to solve the above-described problems. A friction equivalent component when steering torque control is performed without causing steering wheel vibration and without feeling uncomfortable to the driver. It is an object to obtain a steering control device and a steering control method capable of compensation.

  A steering control device according to the present invention includes a detection unit that detects a rotation angle and a rotation angular velocity of a steering shaft, and a friction compensation torque controller that adds a friction compensation torque for compensating a friction torque generated in the steering mechanism. The friction compensation torque controller includes a sign determination unit for determining the sign of the rotational angular velocity of the steering shaft detected by the detection unit, and a friction compensation torque target value that has reached a steady state based on the sign of the rotational angular velocity of the steering shaft. When the friction compensation torque steady value setter that sets a certain friction compensation torque steady value and the sign of the rotational angular velocity of the steering shaft are reversed, the initial value of the friction compensation torque target value is set, and the rotational angular velocity of the steering shaft As the absolute value of the relative angle with respect to the rotation angle of the steering shaft increases, the friction compensation is performed. The initial value of the torque target value, a change adjuster for calculating a friction compensation torque value to approach the friction compensation torque constant value, but having a.

  The steering control method according to the present invention includes a detection step for detecting a rotation angle and a rotation angular velocity of the steering shaft, and a friction compensation torque control step for adding a friction compensation torque for compensating the friction torque generated in the steering mechanism. The friction compensation torque control step includes a sign determination step for determining a sign of the rotational angular velocity of the steering shaft detected in the detection step, and a friction compensation torque target value that has reached a steady state based on the sign of the rotational angular velocity of the steering shaft. A friction compensation torque steady value setting step for setting the friction compensation torque steady value, a setting step for setting an initial value of the friction compensation torque target value when the sign of the rotational angular velocity of the steering shaft is inverted, and a steering shaft It corresponds to the rotation angle of the steering shaft when the sign of the rotation angular velocity is reversed. With increasing absolute value of the relative angle that includes the initial value of the friction compensation torque target value, the adjustment step of calculating a friction compensation torque value to approach the friction compensation torque constant value.

According to the steering control device and the steering control method of the present invention, the change adjuster (setting step and adjusting step) sets the initial value of the friction compensation torque target value when the sign of the rotational angular velocity of the steering shaft is reversed. In addition, as the absolute value of the relative angle with respect to the rotation angle of the steering shaft at the time when the sign of the rotational angular velocity of the steering shaft is reversed, the initial value of the friction compensation torque target value is adjusted so as to approach the steady value of the friction compensation torque. Compensation torque target value is calculated.
Thus, even without a dead zone or a low-pass filter, it is possible to prevent the occurrence of steering wheel vibrations due to repetitive changes in the rotational angular velocity code of the steering shaft due to minute fluctuations in the steering shaft rotational angle and noise.
Therefore, it is possible to compensate for a friction equivalent component when performing steering torque control without causing steering wheel vibration and without causing the driver to feel uncomfortable.

It is a block diagram which shows the friction compensation torque controller of the steering control apparatus which concerns on Embodiment 1 of this invention. It is a block diagram which shows the motor output controller of the steering control apparatus which concerns on Embodiment 1 of this invention. It is a flowchart which shows operation | movement of the friction compensation torque controller of the steering control apparatus which concerns on Embodiment 1 of this invention. It is explanatory drawing which shows the time response of the friction compensation torque in the steering control apparatus which concerns on Embodiment 1 of this invention. In the steering control device according to Embodiment 1 of the present invention, it is an explanatory diagram showing a response of a friction compensation torque to a steering shaft rotation angle when steering is performed at a low frequency. FIG. In the steering control device according to Embodiment 1 of the present invention, it is an explanatory diagram showing a response of a friction compensation torque to a steering shaft rotation angle when steering is performed at a high frequency. FIG. It is a flowchart which shows operation | movement of the friction compensation torque controller of the steering control apparatus which concerns on Embodiment 2 of this invention. In the steering control device according to Embodiment 3 of the present invention, it is an explanatory diagram showing friction compensation torque steady value setting when the friction torque existing in the steering mechanism itself is sufficiently small. In the steering control device according to Embodiment 3 of the present invention, it is an explanatory diagram showing friction compensation torque steady value setting when the friction torque existing in the steering mechanism itself cannot be ignored. In the steering control apparatus according to Embodiment 4 of the present invention, description will be made on the friction compensation torque steady value setting when the friction torque existing in the steering mechanism itself has the sign dependency of the steering shaft rotation angle and the steering shaft rotation speed. FIG. It is a flowchart which shows operation | movement of the friction compensation torque controller of the steering control apparatus which concerns on Embodiment 4 of this invention. It is a block diagram which shows the friction compensation torque controller of the steering control apparatus which concerns on Embodiment 5 of this invention. It is a flowchart which shows operation | movement of the friction compensation torque controller of the steering control apparatus which concerns on Embodiment 5 of this invention. It is explanatory drawing which shows the time response of the friction compensation torque in the steering control apparatus which concerns on Embodiment 5 of this invention. It is explanatory drawing which shows the response at the time of noise being applied to steering-shaft rotation angular velocity in the time response of the friction compensation torque in the steering control apparatus which concerns on Embodiment 5 of this invention. In the steering control device according to Embodiment 5 of the present invention, it is an explanatory diagram showing the response of the friction compensation torque to the steering shaft rotation angle when steering is performed at a low frequency. In the steering control device concerning Embodiment 5 of this invention, it is explanatory drawing which shows the response with respect to the steering shaft rotation angle of the friction compensation torque at the time of steering at a high frequency. It is a flowchart which shows operation | movement of the friction compensation torque controller of the steering control apparatus which concerns on Embodiment 6 of this invention. It is a flowchart which shows operation | movement of the friction compensation torque controller of the steering control apparatus which concerns on Embodiment 8 of this invention.

  Hereinafter, preferred embodiments of a steering control device and a steering control method according to the present invention will be described with reference to the drawings. In the drawings, the same or corresponding parts will be described with the same reference numerals.

Embodiment 1 FIG.
1 is a block diagram showing a friction compensation torque controller of a steering control device according to Embodiment 1 of the present invention. In FIG. 1, the friction compensation torque controller includes a sign discriminator 1, a friction compensation torque steady value setting device 2, and a change adjuster 3.

  The code discriminator 1 discriminates the sign of the rotational angular velocity, that is, the steering direction by the driver, based on the rotational angular velocity of the steering shaft detected by a detection unit (not shown) that detects the rotational angle and rotational angular velocity of the steering shaft. To do.

  The friction compensation torque steady value setting unit 2 sets the friction compensation torque steady value based on the output of the sign discriminator 1. The change adjuster 3 sets a friction compensation torque target value based on the friction compensation torque steady value set by the friction compensation torque steady value setter 2 and the steering shaft rotation angle detected by the detector.

  FIG. 2 is a block diagram showing a motor output controller of the steering control device according to Embodiment 1 of the present invention. In FIG. 2, the motor output controller includes an adder 4 and a motor torque controller 5.

  The adder 4 adds the friction compensation torque target value set by the change adjuster 3 and other compensation torque target values such as steering torque compensation and steering angle compensation well known in the steering control device, Calculate the motor output torque target value. The friction compensation torque target value may be directly used as the motor output torque target value.

  The motor torque controller 5 performs control so that the actual motor output torque matches the motor output torque target value by using current feedback or the like.

  Next, the operation of the friction compensation torque controller of the steering control device according to the first embodiment of the present invention will be described with reference to the flowchart of FIG. The operation of this flowchart is repeated at a predetermined cycle.

  First, the steering shaft rotation angle is detected (step S001), and the steering shaft rotation angular velocity is detected (step S002). Here, the steering shaft rotation angular velocity may be obtained by differentiating the output of the rotation angle sensor, or may be directly measured using the rotation angular velocity sensor.

  Subsequently, the sign of the steering shaft rotational angular velocity is determined (step S003), and it is determined whether or not the sign of the steering shaft rotational angular velocity is reversed (step S004).

  If it is determined in step S004 that the sign of the steering shaft rotation angular velocity has been reversed (that is, Yes), the steering shaft rotation angle at the time of sign reversal is updated from the previously stored value and stored. (Step S005).

  The initial value of the steering shaft rotation angle at the time of sign reversal, that is, the value until the first sign reversal occurs after the steering control device starts operating due to the ignition switch on by key operation of the automobile is set to zero. Keep it.

  Next, a predetermined friction compensation torque steady value is read and determined in accordance with the sign of the steering shaft rotation angular velocity (step S006). Here, the steady value of the friction compensation torque is set such that the absolute value thereof is set equal to the friction torque component in the steering torque characteristic of the target steering, that is, the amplitude of the target friction feeling, and the code corresponding to the sign of the steering shaft rotational angular velocity. It is determined and stored in advance so that changes.

  Subsequently, the friction compensation torque target value is set to a predetermined initial value after sign inversion (step S007), and the process proceeds to step S008. If it is determined in step S004 that the sign of the steering shaft rotation angular velocity is not reversed (that is, No), the process proceeds to step S008.

  Next, the stored steering shaft rotation angle at the time of sign inversion is subtracted from the detected value of the steering shaft rotation angle and the absolute value is calculated to obtain the absolute value of the relative angle (step S008).

  Subsequently, the friction compensation torque target value corresponding to the absolute value of the relative angle is calculated and stored (step S009), and the process of FIG. 3 ends.

  Hereinafter, a method of calculating the friction compensation torque target value corresponding to the absolute value of the relative angle in step S009 described above will be described in detail.

When the detected value of the steering shaft rotation angle is θ _sw and the stored steering shaft rotation angle at the time of sign inversion is θ _ch , the absolute value θ of the relative angle is expressed by the following equation (1).

θ = | θ _sw −θ _ch | Equation (1)

Here, the friction compensation torque steady value is T _fs , the friction compensation torque target value is T _fref , the angle constant set by the designer is θ _p , and the friction compensation torque target value T _fref for the absolute value θ of the relative angle is Calculated as the solution of the differential equation of equation (2).

Therefore, when the sign of the steering shaft rotational angular velocity changes, θ is set to zero, and according to the change of θ until the sign changes, friction compensation is performed by calculating the differential equation of Equation (2). A torque target value T _fref is obtained.

If the initial value after sign inversion is _Tf0 , an analytical solution represented by the following equation (3) is obtained for the differential equation of equation (2).

Therefore, when the sign of the steering shaft rotation angular velocity changes, θ is set to zero, and the calculation of equation (3) is performed according to the change of θ until the sign changes next, _{thereby obtaining the} friction compensation torque target value T _fref . Ask.

At this time, since the friction compensation torque target value T _fref of the equation (3) hardly _rises for a small change in the absolute value θ of the relative angle, the steering shaft rotation angle is hardly affected by noise and noise. Become.

When the initial T _f0 after sign inversion is set to zero, the friction compensation torque target value T _fref is expressed by the following equation (4).

In this case, when the sign of the steering shaft rotation angular velocity changes, the friction compensation torque target value T _fref becomes zero. For this reason, even when a _slight steering rotation angle fluctuation or noise that frequently changes in sign occurs, the friction compensation torque target value T _fref is always near zero, and the steering wheel vibration reduction effect is the highest.

When the steering shaft rotational angular velocity becomes zero, it is considered that the sign is reversed and the friction compensation torque target value T _fref is set to zero. By doing so, unnecessary friction compensation torque is not applied when the driver holds the steering wheel at a certain angle, for example, when the vehicle is traveling straight.

Here, the response will be described by taking as an example a case where the initial T _f0 after sign inversion is set to zero. For example, when the steering wheel is steered so that the rotational angular velocity becomes a sine wave at the lane change, as shown in FIG. 4, when the sign of the steering shaft rotational angular velocity is switched, the friction compensation torque target value T _fref is instantaneously changed. Becomes a waveform that rises from zero toward the friction compensation torque steady value _Tfs .

  This waveform rises in the same way even when a low-pass filter is used instead of Equation (4) when the horizontal axis is time. However, when the horizontal axis is the steering shaft rotation angle and the steering frequency is changed, the waveform is compared. , The difference becomes clear.

  FIG. 5 shows the response of the friction compensation torque to the steering shaft rotation angle when steering is performed at a low frequency in the steering control apparatus according to the first embodiment of the present invention. FIG. In such a steering control device, the response of the friction compensation torque to the steering shaft rotation angle when steering at a high frequency is shown. 5 and 6, the solid line indicates the friction compensation torque target value according to the first embodiment of the present invention, and the broken line indicates the case where a low-pass filter is used.

  As shown in FIG. 5, when the steering is performed at a low frequency, the waveform is the same in the case of the first embodiment of the present invention and the case where the low pass filter is used, that is, the solid line and the broken line are overlapped. As shown in FIG. 6, when steering is performed at a high frequency, if a low-pass filter is used, the waveform of the steering torque with respect to the steering shaft rotation angle changes.

  That is, the steering feeling changes depending on the steering frequency. On the other hand, in the case of Embodiment 1 of the present invention, there is no change in the waveform of the steering torque with respect to the steering shaft rotation angle, and the steering feeling is the same regardless of the steering frequency.

For the same reason, when the driver turns the steering wheel up to a certain angle and then turns it back at an extremely slow speed to the extent that it can be assumed that the steering wheel is held at that angle, the low-pass When the filter is used, the steering torque response waveform changes despite the almost constant angle of the steering wheel. On the other hand, in the first embodiment of the present invention, if the angle is substantially constant, the response waveform of the friction compensation torque target value T _fref hardly changes.

As described above, according to the first embodiment, when the sign of the rotational angular velocity of the steering shaft is reversed, the change adjuster sets the initial value of the friction compensation torque target value, and the rotational angular velocity of the steering shaft. The friction compensation torque target value is calculated so that the initial value of the friction compensation torque target value approaches the friction compensation torque steady value according to the increase in the absolute value of the relative angle with respect to the rotation angle of the steering shaft at the time when the sign is reversed.
The change adjuster sets the initial value of the friction compensation torque target value to the initial value after the sign inversion whose absolute value is smaller than the steady value of the friction compensation torque at the same time as the sign of the rotational angular velocity of the steering shaft is inverted.
As a result, even if there is no dead zone or low-pass filter that may give the driver a sense of incongruity, steering wheel vibration due to repetitive changes in the steering shaft rotation angular velocity code due to the influence of minute fluctuations in the steering shaft rotation angle and noise Occurrence can be prevented.
Therefore, it is possible to compensate for a friction equivalent component when performing steering torque control without causing steering wheel vibration and without causing the driver to feel uncomfortable.

The change adjuster calculates the friction compensation torque target value as a solution of the differential equation with the initial value after sign inversion as the initial value. The differential equation is the absolute value of the relative angle. The derivative to be differentiated and the equation obtained by subtracting the value obtained by subtracting the friction compensation torque target value from the friction compensation torque steady value by a preset angle constant are connected by an equal sign.
Therefore, the change adjuster can be easily designed.

Embodiment 2. FIG.
The second embodiment of the present invention relates to a method for calculating the target value of the friction compensation torque in the change adjuster 3.

  The operation of the friction compensation torque controller of the steering control device according to the second embodiment of the present invention will be described below with reference to the flowchart of FIG. The operation of this flowchart is repeated at a predetermined cycle. Since steps S101 to S108 are the same as steps S001 to 008 in FIG. 3 described above, description thereof is omitted.

Following step S108, it is determined whether or not the absolute value of the relative angle has changed by a preset angle θ _res (step S109).

If it is determined in step S109 that the absolute value of the relative angle has changed by a preset angle θ _res (ie, Yes), a friction compensation torque target value corresponding to the absolute value of the relative angle is calculated and stored. (Step S110), and the process of FIG. 7 ends.

On the other hand, if it is determined in step S109 that the absolute value of the relative angle has not changed by the preset angle θ _res (that is, No), the stored value of the friction compensation torque target value is updated. Instead, the process of FIG. 7 ends.

  Hereinafter, a method of calculating the friction compensation torque target value corresponding to the absolute value of the relative angle in step S110 described above will be described in detail.

  First, the above formula (2) can be expressed by the recurrence formula of the following formula (5) using the recurrence formula calculation step number k in which the sign inversion time is zero.

Here, the number k of the recurrence calculation steps increases by 1 each time it is determined in step S109 that the absolute value of the relative angle has changed by a preset angle θ _res . The initial value T _ref (0) of the initial friction compensation torque is set to the initial value T _f0 after sign inversion. At this time, the friction compensation torque steady value T _fs may be a different value each time the number of recurrence calculation steps is changed, for example, as a function of the steering rotation angle.

In calculation, when the sign of the steering shaft rotation angular velocity changes, the recurrence formula calculation step number is reset, and the target value T _ref of the friction compensation torque is set to the initial value T _f0 after sign inversion. Next, every time it is determined in step S109 that the absolute value of the relative angle has changed by the preset angle θ _res until the sign of the steering shaft rotational angular velocity changes, the calculation of equation (5) is performed. Then, a friction compensation torque target value T _fref is obtained.

Note that the preset angle θ _res may be equivalent to 1 bit of the rotation angle, for example, set to the resolution in detecting the steering shaft rotation angle, or may be set to 2 bits or more.

  In addition, since the following two values in the equation (5) are both constants (first constant and second constant), they may be calculated and stored in advance.

Further, when mounted on a microcomputer or the like, the above formula (5) does not need to store the calculation result for each number of recursive formula operation steps k, and the calculation of the right side of the above formula (5) and the left side of the calculation result When the assignment to is completed, the variables T _fref (k) and T _fs (k) on the right side are usually unnecessary. Therefore, the absolute value of the relative angle may be overwritten whenever it is determined that the preset angle θ _{res has} changed.

Further, the value of the recurrence formula operation step number k is reset every time the angle θ _res changes, and if k is treated as 0, k + 1 is treated as 1, etc., the storage amount in the microcomputer or the like can be saved.

As described above, according to the second embodiment, the change adjuster calculates the friction compensation torque target value after the change as a solution of the recurrence formula using the initial value after the sign inversion as the initial value. In the recurrence formula, when the absolute value of the relative angle at the time of digital calculation changes in a preset number of bits, a value obtained by multiplying the friction compensation torque target value before the change by the first constant, and the friction compensation torque steady state A value obtained by multiplying the value by a second constant is added.
Therefore, digital calculation can be easily performed by a microcomputer or the like frequently used in the steering control device.

Embodiment 3 FIG.
The third embodiment of the present invention relates to a method for calculating the friction compensation torque steady value T _{fs in} the friction compensation torque steady value setting device 2. Note that the operation of the friction compensation torque steady value setting unit 2 may be either step S006 or step S106 described above.

In the first and second embodiments described above, as shown in FIG. 8, it is assumed that the friction torque existing in the steering mechanism itself is sufficiently small, and the absolute value of the friction compensation torque steady value _Tfs is the target steering steering value. The steering torque characteristic was set equal to the amplitude of the target friction feeling.

On the other hand, in Embodiment 3 of the present invention, as shown in FIG. 9, assuming that the friction torque existing in the steering mechanism itself cannot be ignored, the absolute value of the friction compensation torque steady value T _fs is assumed to be the target. It is set by subtracting the amplitude of the friction torque existing in the steering mechanism itself from the amplitude of the target friction feeling in the steering torque characteristic of the steering.

As described above, according to the third embodiment, the friction compensation torque steady value setter subtracts the absolute value of the friction compensation torque steady value from the target friction torque amplitude. Set the value to
Therefore, even when the friction torque existing in the steering mechanism itself cannot be ignored, the target friction feeling can be realized.

Embodiment 4 FIG.
In the fourth embodiment of the present invention, as shown in FIG. 10, the friction compensation torque steady value _Tfs is changed according to the signs of the steering shaft rotation angle and the steering shaft rotation speed.

Here, for each sign of the steering shaft rotation angle and the steering shaft rotation angular velocity, the absolute value of the friction compensation torque steady value _Tfs is the amplitude of the target friction feeling in the steering torque characteristic of the target steering and the steering mechanism itself. Is stored in advance in a map so as to be different from the amplitude of the friction torque existing in

  The operation of the friction compensation torque controller of the steering control device according to the fourth embodiment of the present invention will be described below with reference to the flowchart of FIG. The operation of this flowchart is repeated at a predetermined cycle.

  First, the steering shaft rotation angle is detected (step S201), and the steering shaft rotation angular velocity is detected (step S202). Here, the steering shaft rotation angular velocity may be obtained by differentiating the output of the rotation angle sensor, or may be directly measured using the rotation angular velocity sensor.

  Subsequently, the sign of the steering shaft rotation angular velocity is determined (step S203), and it is determined whether or not the sign of the steering shaft rotation angular velocity is reversed (step S204).

  If it is determined in step S204 that the sign of the steering shaft rotation angular velocity has been reversed (that is, Yes), the steering shaft rotation angle at the time of sign reversal is updated from the previously stored value and stored. (Step S205).

  Subsequently, the friction compensation torque target value is set to a predetermined initial value after sign inversion (step S206), and the process proceeds to step S207. Further, when it is determined in step S204 that the sign of the steering shaft rotational angular velocity is not reversed (that is, No), the process proceeds to step S207.

  Next, the stored steering shaft rotation angle at the time of sign inversion is subtracted from the detected steering shaft rotation angle value, and the absolute value is calculated to obtain the absolute value of the relative angle (step S207).

Subsequently, it is determined whether or not the absolute value of the relative angle has changed by a preset angle θ _res (step S208).

If it is determined in step S208 that the absolute value of the relative angle has changed by a preset angle θ _res (ie, Yes), the steady value of the friction compensation torque is the sign of the steering shaft rotation angle and the steering shaft rotation angular velocity in advance. It is calculated and set from the map determined every time (step S209).

  Next, a friction compensation torque target value corresponding to the absolute value of the relative angle is calculated and stored (step S210), and the process of FIG. 11 ends.

On the other hand, if it is determined in step S208 that the absolute value of the relative angle has not changed by the preset angle θ _res (ie, No), the stored value of the friction compensation torque target value is updated. Instead, the process of FIG. 11 ends.

As described above, according to the fourth embodiment, the friction compensation torque steady value setter uses the absolute value of the friction compensation torque steady value as a map for each sign of the steering shaft rotation angle and the steering shaft rotation angular velocity. I remember it.
Therefore, even when the friction torque existing in the steering mechanism itself changes according to the steering shaft rotation angle and the sign of the steering shaft rotation speed, the target friction feeling can be realized.

Embodiment 5. FIG.
FIG. 12 is a block diagram showing a friction compensation torque controller of a steering control device according to Embodiment 5 of the present invention. In FIG. 12, the friction compensation torque controller includes a sign discriminator 11, a friction compensation torque steady value setting unit 12, a friction compensation torque initial value acquisition unit 13, and a change adjuster 14.

  The code discriminator 11 discriminates the sign of the rotational angular velocity, that is, the steering direction by the driver, based on the rotational angular velocity of the steering shaft detected by a detector (not shown) that detects the rotational angle and rotational angular velocity of the steering shaft. To do.

  The friction compensation torque steady value setting unit 12 sets the friction compensation torque steady value based on the output of the sign discriminator 11. The friction compensation torque initial value acquisition unit 13 acquires the friction compensation torque initial value when the steering direction reversal occurs based on the output of the sign discriminator 11.

  The change adjuster 14 includes the friction compensation torque steady value set by the friction compensation torque steady value setter 12, the friction compensation torque initial value obtained by the friction compensation torque initial value obtainer 13, and the steering detected by the detection unit. A friction compensation torque target value is set based on the shaft rotation angle.

  The friction compensation torque target value set by the change adjuster 14 is input to the motor output controller shown in FIG. 2, and the adder 4 adds the friction compensation torque target value set by the change adjuster 14 and the steering control. A motor output torque target value is calculated by adding the other compensation torque target values such as steering torque compensation and steering angle compensation well known in the apparatus.

  Further, the motor torque controller 5 controls the actual motor output torque so as to coincide with the motor output torque target value by using current feedback or the like.

  Next, the operation of the friction compensation torque controller of the steering control device according to the fifth embodiment of the present invention will be described with reference to the flowchart of FIG. The operation of this flowchart is repeated at a predetermined cycle.

  First, the steering shaft rotation angle is detected (step S301), and the steering shaft rotation angular velocity is detected (step S302). Here, the steering shaft rotation angular velocity may be obtained by differentiating the output of the rotation angle sensor, or may be directly measured using the rotation angular velocity sensor.

  Subsequently, the sign of the steering shaft rotational angular velocity is determined (step S303), and it is determined whether or not the sign of the steering shaft rotational angular velocity is reversed (step S304).

  If it is determined in step S304 that the sign of the steering shaft rotation angular velocity has been reversed (that is, Yes), the steering shaft rotation angle at the time of sign reversal is updated from the value stored so far and stored. (Step S305).

  The initial value of the steering shaft rotation angle at the time of sign reversal, that is, the value until the first sign reversal occurs after the steering control device starts operating due to the ignition switch on by key operation of the automobile is set to zero. Keep it.

  Next, a predetermined friction compensation torque steady value is read and determined according to the sign of the steering shaft rotation angular velocity (step S306). Here, the steady value of the friction compensation torque is set such that the absolute value thereof is set equal to the friction torque component in the steering torque characteristic of the target steering, that is, the amplitude of the target friction feeling, and the code corresponding to the sign of the steering shaft rotational angular velocity. It is determined and stored in advance so that changes.

  Subsequently, the friction compensation torque target value at the time of sign inversion is stored as an initial value for calculating the friction compensation torque target value (step S307), and the process proceeds to step S308. Further, when it is determined in step S304 that the sign of the steering shaft rotation angular velocity is not reversed (that is, No), the process proceeds to step S308.

  Next, the stored steering shaft rotation angle at the time of sign inversion is subtracted from the detected value of the steering shaft rotation angle, and the absolute value is calculated to obtain the absolute value of the relative angle (step S308).

  Subsequently, the friction compensation torque target value corresponding to the absolute value of the relative angle is calculated and stored (step S309), and the process of FIG. 13 ends.

  Hereinafter, a method of calculating the friction compensation torque target value according to the absolute value of the relative angle in step S309 described above will be described in detail.

If the detected value of the steering shaft rotation angle is θ _sw and the stored steering shaft rotation angle at the time of sign inversion is θ _ch , the absolute value θ of the relative angle is expressed by the above-described equation (1).

Here, the friction compensation torque steady value is T _fs , the friction compensation torque target value is T _fref , the angle constant set by the designer is θ _p , and the friction compensation torque target value T _fref for the absolute value θ of the relative angle is It calculates as a solution of the differential equation of the above-mentioned formula (2).

Therefore, when the sign of the steering shaft rotation angular velocity changes, θ is set to zero, the friction compensation torque target value T _ch at the time of sign inversion is set as the initial value of the friction compensation torque target value T _fref , and the sign changes until the next change. The friction compensation torque target value T _fref is obtained by performing an operation for _obtaining a solution of the differential equation of Expression (2) according to the change of θ.

Further, when the friction compensation torque target value at the time of sign inversion is _Tch , an analytical solution represented by the following equation (6) is obtained with respect to the differential equation of equation (2).

Therefore, when the sign of the steering shaft rotation angular velocity changes, θ is set to zero, and the calculation of equation (6) is performed according to the change of θ until the sign changes next, _{thereby obtaining the} friction compensation torque target value T _fref . Ask.

At this time, since the calculation is performed with the friction compensation torque target value _Tch at the time when the sign of the steering shaft rotation angular velocity is changed as an initial value, even when the sign of the steering shaft rotation angular velocity is changed, the friction compensation torque target value is discontinuous. There is no major change.

Further, since the friction compensation torque target value T _fref of the equation (6) hardly _rises for a small change in the absolute value θ of the relative angle, the steering shaft rotation angle is hardly affected by noise and noise. .

When the steering shaft rotation angular velocity becomes zero, it is considered that the sign is reversed, and the friction compensation torque steady value _Tfs is preferably set to zero. This makes it difficult for unnecessary friction compensation torque to be applied when the driver holds the steering wheel at a certain angle, for example, when the vehicle is traveling straight.

Here, the response according to the fifth embodiment of the present invention will be described. For example, when the steering wheel is steered so that the rotational angular velocity becomes a sine wave at the lane change, as shown in FIG. 14, when the sign of the steering shaft rotational angular velocity is switched, the friction compensation torque target value T _fref is The waveform rises from the friction compensation torque target value _Tch at the time of sign inversion toward the friction compensation torque steady value _Tfs .

Next, the response of the friction compensation torque target value when noise is applied to the steering shaft rotation angular velocity will be described with reference to FIG. In FIG. 15, when noise up to a level at which the sign of the steering shaft rotation speed is reversed, the sign of the friction compensation torque steady value T _fs is reversed.

Therefore, the calculation is performed using the friction compensation torque target value _Tch at the time when the sign of the steering shaft rotation angular velocity changes as an initial value, but the time during which the sign is reversed due to noise is extremely short, and the absolute value θ of the relative angle therebetween Therefore, when θ in the equation (6) is regarded as almost zero, the friction compensation torque target value T _fref hardly responds from the friction compensation torque target value T _ch at the time when the sign changes.

  The waveform shown in FIG. 14 is a waveform that rises in the same manner even when a low-pass filter is used instead of Equation (6) when the horizontal axis is time, but the horizontal axis is the steering shaft rotation angle, and the steering frequency is The difference becomes clear when you change and compare.

  FIG. 16 shows the response of the friction compensation torque to the steering shaft rotation angle when steering is performed at a low frequency in the steering control apparatus according to the fifth embodiment of the present invention, and FIG. 17 shows the fifth embodiment of the present invention. In such a steering control device, the response of the friction compensation torque to the steering shaft rotation angle when steering at a high frequency is shown. 16 and 17, the solid line indicates the friction compensation torque target value according to the fifth embodiment of the present invention, and the broken line indicates the case where a low-pass filter is used.

  As shown in FIG. 16, when steering is performed at a low frequency, in the case of the fifth embodiment of the present invention and when the low-pass filter is used, the waveform is set to be the same, that is, the solid line and the broken line are overlapped. As shown in FIG. 17, when steering is performed at a high frequency, when a low-pass filter is used, the waveform of the steering torque with respect to the steering shaft rotation angle changes.

  That is, the steering feeling changes depending on the steering frequency. On the other hand, in the case of Embodiment 5 of the present invention, there is no change in the waveform of the steering torque with respect to the steering shaft rotation angle, and the steering feeling is the same regardless of the steering frequency.

For the same reason, when the driver turns the steering wheel up to a certain angle and then turns it back at an extremely slow speed to the extent that it can be assumed that the steering wheel is held at that angle, the low-pass When the filter is used, the steering torque response waveform changes despite the almost constant angle of the steering wheel. On the other hand, in the fifth embodiment of the present invention, if the angle is substantially constant, the response waveform of the friction compensation torque target value T _fref hardly changes.

As described above, according to the fifth embodiment, when the sign of the rotational angular velocity of the steering shaft is reversed, the change adjuster sets the initial value of the friction compensation torque target value, and the rotational angular velocity of the steering shaft. The friction compensation torque target value is calculated so that the initial value of the friction compensation torque target value approaches the friction compensation torque steady value according to the increase in the absolute value of the relative angle with respect to the rotation angle of the steering shaft at the time when the sign is reversed.
In addition, at the same time as the sign of the rotational angular velocity of the steering shaft is reversed, the friction compensation torque initial value acquisition unit that acquires the friction compensation torque target value at that time as the initial value of the friction compensation torque is further provided. The initial value of the friction compensation torque is used as the initial value of the friction compensation torque, and the friction compensation torque target value is calculated so that the initial value of the friction compensation torque approaches the steady value of the friction compensation torque.
As a result, even if there is no dead zone or low-pass filter that may give the driver a sense of incongruity, the steering wheel vibration caused by repeated changes in the steering shaft rotational angular velocity code due to the slight fluctuation of the steering shaft rotational angle and the influence of noise. Occurrence can be prevented.
Therefore, it is possible to compensate for a friction equivalent component when performing steering torque control without causing steering wheel vibration and without causing the driver to feel uncomfortable.

The change regulator calculates the friction compensation torque target value as a solution of the differential equation with the initial value of the friction compensation torque as an initial value. The differential equation expresses the friction compensation torque target value as an absolute value of the relative angle. The derivative to be differentiated and the equation obtained by subtracting the value obtained by subtracting the friction compensation torque target value from the friction compensation torque steady value by a preset angle constant are connected by an equal sign.
Therefore, the change adjuster can be easily designed.

Embodiment 6 FIG.
The sixth embodiment of the present invention relates to a method for calculating the target value of the friction compensation torque in the change adjuster 14.

  The operation of the friction compensation torque controller of the steering control device according to the sixth embodiment of the present invention will be described below with reference to the flowchart of FIG. The operation of this flowchart is repeated at a predetermined cycle. Note that steps S401 to S408 are the same as steps S301 to S308 in FIG.

Following step S408, it is determined whether or not the absolute value of the relative angle has changed by a preset angle θ _res (step S409).

If it is determined in step S409 that the absolute value of the relative angle has changed by a preset angle θ _res (ie, Yes), a friction compensation torque target value corresponding to the absolute value of the relative angle is calculated and stored. (Step S410), and the process of FIG. 18 ends.

On the other hand, if it is determined in step S409 that the absolute value of the relative angle has not changed by the preset angle θ _res (that is, No), the stored value of the friction compensation torque target value is updated. Instead, the process of FIG. 18 ends.

  Hereinafter, a method of calculating the friction compensation torque target value corresponding to the absolute value of the relative angle in step S410 described above will be described in detail.

  First, the above formula (2) can be expressed by the recurrence formula of the following formula (7) using the recurrence formula calculation step number k in which the sign inversion time is zero.

Here, the number of recursive formula calculation steps k increases by 1 each time it is determined in step S409 that the absolute value of the relative angle has changed by a preset angle θ _res . The initial target value T _ref (0) of the friction compensation torque is set to the friction compensation torque target value T _ch at the time of sign inversion. At this time, the friction compensation torque steady value T _fs may be a different value each time the number of recurrence calculation steps is changed, for example, as a function of the steering rotation angle.

Further, in the calculation, when the sign of the steering shaft rotational angular velocity changes, the recurrence formula calculation step number is reset, and the friction compensation torque target value T _ref (0) is changed to the friction compensation torque target value T at the time of sign inversion. Set to _ch . Next, every time it is determined in step S409 that the absolute value of the relative angle has changed by the preset angle θ _res until the sign of the steering shaft rotational angular velocity changes, the calculation of equation (7) is performed. Then, a friction compensation torque target value T _fref is obtained.

Note that the preset angle θ _res may be equivalent to 1 bit of the rotation angle, for example, set to the resolution in detecting the steering shaft rotation angle, or may be set to 2 bits or more.

  In addition, the following two values in the equation (7) are both constants (first constant and second constant), so it is preferable to calculate and store them in advance.

Further, when mounted on a microcomputer or the like, the above equation (7) does not need to store the calculation result for each number of recursive equation calculation steps k, and the calculation of the right side of the above equation (7) and the left side of the calculation result When the assignment to is completed, the variables T _fref (k) and T _fs (k) on the right side are usually unnecessary. Therefore, the absolute value of the relative angle may be overwritten whenever it is determined that the preset angle θ _{res has} changed.

Further, the value of the recurrence formula operation step number k is reset every time the angle θ _res changes, and if k is treated as 0, k + 1 is treated as 1, etc., the storage amount in the microcomputer or the like can be saved.

As described above, according to the sixth embodiment, the change regulator calculates the friction compensation torque target value after the change as a solution of the recurrence formula with the friction compensation torque initial value as the initial value. In the recurrence formula, when the absolute value of the relative angle at the time of digital calculation changes in a preset number of bits, a value obtained by multiplying the friction compensation torque target value before the change by the first constant, and the friction compensation torque steady state A value obtained by multiplying the value by a second constant is added.
Therefore, digital calculation can be easily performed by a microcomputer or the like frequently used in the steering control device.

Embodiment 7 FIG.
The seventh embodiment of the present invention relates to a calculation method of the friction compensation torque steady value _{Tfs in} the friction compensation torque steady value setter 12. Note that the operation of the friction compensation torque steady value setting unit 12 may be either step S306 or step S406 described above.

In the fifth and sixth embodiments described above, as shown in FIG. 8, it is assumed that the friction torque existing in the steering mechanism itself is sufficiently small, and the absolute value of the friction compensation torque steady value _Tfs is the target steering steering value. The steering torque characteristic was set equal to the amplitude of the target friction feeling.

On the other hand, in the seventh embodiment of the present invention, as shown in FIG. 9, assuming that the friction torque existing in the steering mechanism itself cannot be ignored, the absolute value of the friction compensation torque steady value T _fs is aimed at. It is set by subtracting the amplitude of the friction torque existing in the steering mechanism itself from the amplitude of the target friction feeling in the steering torque characteristic of the steering.

As described above, according to the seventh embodiment, the friction compensation torque steady value setter subtracts the absolute value of the friction compensation torque steady value from the target friction torque amplitude. Set the value to
Therefore, even when the friction torque existing in the steering mechanism itself cannot be ignored, the target friction feeling can be realized.

Embodiment 8 FIG.
In the eighth embodiment of the present invention, as shown in FIG. 10, the friction compensation torque steady value _Tfs is changed according to the signs of the steering shaft rotation angle and the steering shaft rotation speed.

Here, for each sign of the steering shaft rotation angle and the steering shaft rotation angular velocity, the absolute value of the friction compensation torque steady value _Tfs is the amplitude of the target friction feeling in the steering torque characteristic of the target steering and the steering mechanism itself. Is stored in advance in a map so as to be different from the amplitude of the friction torque existing in

  The operation of the friction compensation torque controller of the steering control device according to the eighth embodiment of the present invention will be described below with reference to the flowchart of FIG. The operation of this flowchart is repeated at a predetermined cycle.

  First, the steering shaft rotation angle is detected (step S501), and the steering shaft rotation angular velocity is detected (step S502). Here, the steering shaft rotation angular velocity may be obtained by differentiating the output of the rotation angle sensor, or may be directly measured using the rotation angular velocity sensor.

  Subsequently, the sign of the steering shaft rotational angular velocity is determined (step S503), and it is determined whether or not the sign of the steering shaft rotational angular velocity is reversed (step S504).

  If it is determined in step S504 that the sign of the steering shaft rotation angular velocity has been reversed (that is, Yes), the steering shaft rotation angle at the time of sign reversal is updated from the previously stored value and stored. (Step S505).

  Subsequently, the friction compensation torque target value at the time of sign inversion is stored as the initial value of the friction compensation torque target value calculation (step S506), and the process proceeds to step S507. If it is determined in step S504 that the sign of the steering shaft rotation angular velocity is not reversed (that is, No), the process proceeds to step S507.

  Next, the stored steering shaft rotation angle at the time of sign inversion is subtracted from the detected steering shaft rotation angle value, and the absolute value is calculated to obtain the absolute value of the relative angle (step S507).

Subsequently, it is determined whether or not the absolute value of the relative angle has changed by a preset angle θ _res (step S508).

If it is determined in step S508 that the absolute value of the relative angle has changed by a preset angle θ _res (ie, Yes), the steady value of the friction compensation torque is determined in advance by the sign of the steering shaft rotation angle and the steering shaft rotation angular velocity. It is calculated and set from the map determined every time (step S509).

  Next, the friction compensation torque target value corresponding to the absolute value of the relative angle is calculated and stored (step S510), and the process of FIG. 19 ends.

On the other hand, if it is determined in step S508 that the absolute value of the relative angle has not changed by the preset angle θ _res (ie, No), the stored value of the friction compensation torque target value is updated. Instead, the process of FIG. 19 ends.

As described above, according to the eighth embodiment, the friction compensation torque steady value setter uses the absolute value of the friction compensation torque steady value as a map for each sign of the rotation angle of the steering shaft and the rotation angular velocity of the steering shaft. I remember it.
Therefore, even when the friction torque existing in the steering mechanism itself changes according to the steering shaft rotation angle and the sign of the steering shaft rotation speed, the target friction feeling can be realized.

  DESCRIPTION OF SYMBOLS 1 Sign discriminator, 2 Friction compensation torque steady value setter, 3 Change adjuster, 4 Adder, 5 Motor torque controller, 11 Sign discriminator, 12 Friction compensation torque steady value setter, 13 Friction compensation torque initial value acquisition 14 Change adjuster.

Claims (10)

A detection unit that detects a rotation angle and a rotation angular velocity of the steering shaft, and a friction compensation torque controller that adds a friction compensation torque for compensating the friction torque generated in the steering mechanism,
The friction compensation torque controller is
A sign determination unit for determining a sign of the rotational angular velocity of the steering shaft detected by the detection unit;
A friction compensation torque steady value setter that sets a friction compensation torque steady value that is a friction compensation torque target value that has reached a steady state, based on the sign of the rotational angular velocity of the steering shaft;
When the sign of the rotational angular velocity of the steering shaft is reversed, the initial value of the friction compensation torque target value is set, and the relative angle with respect to the rotational angle of the steering shaft at the time when the sign of the rotational angular velocity of the steering shaft is reversed A change adjuster that calculates the friction compensation torque target value so that an initial value of the friction compensation torque target value approaches the friction compensation torque steady value according to an increase in the absolute value of
A steering control device comprising: The change adjuster sets an initial value of the friction compensation torque target value to an initial value after sign inversion whose absolute value is smaller than the steady value of the friction compensation torque at the same time as the sign of the rotational angular velocity of the steering shaft is inverted. The steering control device according to claim 1. The change adjuster calculates the friction compensation torque target value as a solution of a differential equation having an initial value after the sign inversion as an initial value,
The differential equation includes a derivative that differentiates the friction compensation torque target value by the absolute value of the relative angle, and a value obtained by subtracting the friction compensation torque target value from the steady value of the friction compensation torque with a preset angle constant. The steering control device according to claim 1, wherein the divided expression is connected by an equal sign. The change adjuster calculates the friction compensation torque target value after the change as a solution of a recurrence formula with the initial value after the sign inversion as an initial value,
The recurrence formula is obtained by multiplying the friction compensation torque target value before the change by a first constant when the absolute value of the relative angle at the time of digital calculation changes in a preset number of bits, The steering control device according to claim 1 or 2, wherein a value obtained by multiplying a steady value of the friction compensation torque by a second constant is added. A friction compensation torque initial value acquisition unit that acquires the friction compensation torque target value at that time as the friction compensation torque initial value at the same time as the sign of the rotational angular velocity of the steering shaft is reversed;
The change adjuster uses the friction compensation torque initial value as an initial value of the friction compensation torque target value, and calculates the friction compensation torque target value so that the friction compensation torque initial value approaches the friction compensation torque steady value. The steering control device according to claim 1. The change adjuster calculates the friction compensation torque target value as a solution of a differential equation having the friction compensation torque initial value as an initial value,
The differential equation includes a derivative that differentiates the friction compensation torque target value by the absolute value of the relative angle, and a value obtained by subtracting the friction compensation torque target value from the steady value of the friction compensation torque with a preset angle constant. The steering control device according to claim 1 or 5, wherein the divided expression is connected by an equal sign. The change adjuster calculates the friction compensation torque target value after the change as a solution of a recurrence formula with the friction compensation torque initial value as an initial value.
The recurrence formula is obtained by multiplying the friction compensation torque target value before the change by a first constant when the absolute value of the relative angle at the time of digital calculation changes in a preset number of bits, The steering control device according to claim 1 or 5, wherein a value obtained by multiplying a steady value of the friction compensation torque by a second constant is added. 2. The friction compensation torque steady value setter sets the absolute value of the friction compensation torque steady value to a value obtained by subtracting the amplitude of the friction torque of the steering mechanism from the target amplitude of the friction torque. Item 8. The steering control device according to any one of Items 1 to 7. 9. The friction compensation torque steady value setter stores the absolute value of the friction compensation torque steady value as a map for each sign of the rotation angle of the steering shaft and the rotation angular velocity of the steering shaft. Steering control device. A detection step for detecting the rotation angle and rotation angular velocity of the steering shaft;
A friction compensation torque control step for adding a friction compensation torque for compensating the friction torque generated in the steering mechanism,
The friction compensation torque control step includes:
A sign determination step for determining a sign of the rotational angular velocity of the steering shaft detected in the detection step;
A friction compensation torque steady value setting step for setting a friction compensation torque steady value, which is a friction compensation torque target value that has reached a steady state, based on the sign of the rotational angular velocity of the steering shaft;
A setting step of setting an initial value of the friction compensation torque target value when the sign of the rotational angular velocity of the steering shaft is reversed;
As the absolute value of the relative angle with respect to the rotation angle of the steering shaft at the time when the sign of the rotational angular velocity of the steering shaft is reversed, the initial value of the friction compensation torque target value approaches the steady value of the friction compensation torque. An adjusting step for calculating the friction compensation torque target value;
A steering control method including:

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