JP2003267244A - Electric power steering device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To effectively prevent the resonance frequency of a vehicle in yaw direction and the resulting traveling stability of the vehicle from being lowered when a reciprocating steering is performed at a frequency in a yaw resonance frequency range without excessively increasing a steering reaction at normal steering. <P>SOLUTION: A steering frequency Pc is calculated by the detection of reversal in a steering direction to determine whether or not the steering frequency is within the range of a specified steering frequency and may cause the yaw resonance frequency on the vehicle (S30-100). If the yaw resonance frequency may occur, a viscosity compensating toque Td for preventing the yaw resonance oscillation of the vehicle based on a steering speed ω, a vehicle speed V, and the maximum value Tp of the magnitude of a steering torque Ts is calculated to a value larger than a value obtained at normal steering (S140-170). An electric motor 26 is controlled based on a target control toque Tc obtained as the sum of a supporting steering toque Ta based on the steering torque Ts and the viscosity compensating toque Tdf after the treatment of a low-pass filter (S180200). <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle power steering apparatus, and more particularly to an electric power steering apparatus.

[0002]

2. Description of the Related Art As one of electric power steering devices for vehicles such as automobiles, for example, as disclosed in Japanese Patent No. 2546673, a target assist for reducing a steering burden on a driver based on a steering torque. The steering torque is calculated, and the target viscosity compensation torque (target damping torque) is calculated based on the steering speed and the vehicle speed so that the higher the vehicle speed, the larger the target torque of the electric motor based on the target auxiliary steering torque and the target viscosity compensation torque. An electric power steering apparatus configured to calculate and to control an electric motor based on the target torque is conventionally known.

According to such an electric power steering system, the target viscosity compensation torque is calculated based on the steering speed and the vehicle speed so that the higher the vehicle speed, the larger the target auxiliary steering torque and the target torque based on the target viscosity compensation torque. Since the electric motor is controlled, compared to the case where the target viscosity compensation torque is calculated based only on the steering speed,
It is possible to secure a good parting stability during high-speed running and a preferable parting stability during low-speed running.

[0004]

Generally, a steering system equipped with an electric power steering apparatus has a resonance frequency of rotational vibration and a vehicle has a yaw resonance frequency, and these resonance frequencies are close to each other. Therefore, when reciprocal steering is performed at a frequency in the resonance frequency range of the rotational vibration of the steering system or the yaw resonance frequency range of the vehicle, the steering system vibrates rotationally and vibrates in the yaw direction, or the steering system vibrates. The vehicle may undergo resonant vibration in the yaw direction due to rotational resonant vibration, which may reduce the running stability of the vehicle. Therefore, in order to prevent the traveling stability of the vehicle from being deteriorated due to the reciprocal steering, the reciprocal steering is performed at a frequency in the rotational resonance frequency range of the steering system or the yaw resonance frequency range of the vehicle. It is preferable that the target viscosity compensating torque is set high and the resonance vibrations of the steering system and the vehicle are effectively damped.

However, in the conventional electric power steering apparatus as described above, the target viscosity compensating torque is calculated based on the steering speed and the vehicle speed without considering the steering frequency and the steering cycle. Rotational resonance vibration of the steering system and resonance vibration of the yaw direction of the vehicle when reciprocal steering is performed in the resonance frequency range or the yaw resonance frequency range of the vehicle, and deterioration of the running stability of the vehicle due to this There is a problem that it cannot be prevented.

According to the present invention, the target auxiliary steering torque is calculated based on the steering torque, the target viscosity compensation torque is calculated based on the steering speed and the vehicle speed, and the target auxiliary steering torque and the target viscosity based on the target viscosity compensation torque are calculated. The present invention has been made in view of the above-mentioned problems in the conventional electric power steering apparatus configured to control the electric motor based on the above. The main problem of the present invention is to perform reciprocal steering. By optimizing the target viscosity compensating torque according to the steering cycle, the viscosity compensating torque during normal steering and the steering reaction force resulting therefrom are not excessively increased, and the rotational resonance frequency range of the steering system or the vehicle When the reciprocal steering is performed at a frequency in the yaw resonance frequency range of the vehicle, the rotational resonance vibration of the steering system, the yaw direction resonance vibration of the vehicle, and the vehicle vibration resulting from this And to effectively prevent a decrease in the line stability.

[0007]

SUMMARY OF THE INVENTION According to the present invention, the above-mentioned main object is to provide an electric motor for generating an auxiliary steering torque, which is provided in a steering system between a steering wheel and a steering wheel. A motor, a means for detecting a steering torque, a means for detecting a steering speed, a target auxiliary steering torque based on the steering torque, and a target torque of the electric motor based on a target viscosity compensation torque based on the steering speed, and the target is calculated. In an electric power steering apparatus having a control means for controlling the electric motor on the basis of torque, the control means determines a steering cycle, and when the steering cycle is within a predetermined range, the steering cycle is the predetermined cycle. When the electric power system has a target viscosity compensating torque varying means for increasing the target viscosity compensating torque as compared with the case of being outside the range, It is achieved by the ring system.

Further, according to the present invention, in order to effectively achieve the above-mentioned main problem, in the structure of claim 1, the target viscosity compensation torque varying means has means for estimating a steering range. The larger the steering range, the larger the increase amount of the target viscosity compensation torque is configured (configuration of claim 2).

Further, according to the present invention, in order to effectively achieve the above-mentioned main problems, in the structure of the above-mentioned claim 1 or 2, the means for judging the steering cycle is means for detecting the steering speed. It is configured to determine the sign reversal of the steering speed detected by the above, and to determine twice the time interval between the sign reversals of the steering speeds as the steering cycle (configuration of claim 3).

[0010]

According to the constitution of the above-mentioned claim 1,
The steering cycle is determined not only when the target torque of the electric motor is calculated based on the target auxiliary steering torque based on the steering torque and the target viscosity compensation torque based on the steering speed, but when the steering cycle is within a predetermined range, the steering cycle is determined. Since the target viscosity compensation torque is increased as compared with when is outside the predetermined range, it is possible to prevent the viscosity compensation torque during normal steering and the steering reaction force resulting from this from becoming excessively high. When the steering cycle is within the predetermined range, the target viscosity compensation torque is increased to effectively damp the rotational vibration of the steering system and the yaw direction vibration of the vehicle, which causes the vehicle to resonate and vibrate in the yaw direction. It is possible to effectively prevent the traveling stability of the vehicle from decreasing.

According to the second aspect of the present invention, the steering range is estimated, and the larger the steering range is, the larger the increase amount of the target viscosity compensation torque is. Therefore, the reciprocal steering is performed in the steering cycle within the predetermined range. Even if it is performed, the target viscosity compensating torque is unnecessarily increased in a situation where the steering range is small and the steering system does not resonate rotationally or the vehicle does not resonate in the yaw direction. It is possible to reliably prevent the steering reaction force from unnecessarily becoming excessively high due to this.

According to the third aspect of the invention, the means for determining the steering cycle determines the sign reversal of the steering speed detected by the means for detecting the steering speed, and the time between the sign reversals of the steering speeds. Since the steering cycle is determined to be twice the target interval, no special detection means for determining the steering cycle is required. Therefore, compared with the case where a special detection means for determining the steering cycle is used. The structure can be simplified and the cost can be reduced.

[0013]

According to a preferred embodiment of the present invention, in the structure of claim 1, the predetermined range corresponds to the resonance frequency of the rotational vibration of the steering system and the yaw of the vehicle. It is configured to include a steering cycle corresponding to the resonance frequency (preferred aspect 1).

According to another preferred aspect of the present invention, in the structure of claim 1, the control means calculates the target auxiliary steering torque based on the steering torque, and the target viscosity compensation torque based on the steering speed. The target torque of the electric motor is calculated based on the target auxiliary steering torque and the low-pass filtered target viscosity compensation torque (preferred aspect 2).

According to another preferred aspect of the present invention, in the structure of claim 1, the control means calculates the target viscosity compensating torque based on the steering speed, and the magnitude of the steering speed is less than or equal to a reference value. In this case, the target viscosity compensation torque is set to 0, and the reference value when the steering cycle is within the predetermined range is configured to be smaller than the reference value when the steering speed is outside the predetermined range (preferred aspect 3 ).

According to another preferred aspect of the present invention, in the structure of claim 1, the target viscosity compensating torque varying means has a target viscosity compensating torque when the steering cycle is not judged by the steering cycle judging means. It is configured not to increase the torque (preferred aspect 4).

According to another preferred aspect of the present invention, in the structure of claim 1, the means for detecting the steering speed detects the voltage value and the current value of the drive current for the electric motor, and the drive current is detected. Is configured to calculate the rotation angular velocity of the electric motor based on the voltage value and the current value, and to calculate the steering speed based on the rotation angular velocity of the electric motor (preferred aspect 5).

According to another preferred aspect of the present invention, in the structure of claim 1, the means for estimating the steering range is operated within the time of the steering cycle determined by the means for determining the steering cycle. The steering range is estimated to be larger as the maximum value of the magnitude of the steering speed detected by the speed detecting means is larger (preferred mode 6).

According to another preferred aspect of the present invention, in the structure of claim 1, the means for estimating the steering range is operated within the time of the steering cycle determined by the means for determining the steering cycle. The steering range is estimated to be larger as the maximum value of the magnitude of the steering speed detected by the speed detecting means is larger (preferred mode 7).

According to another preferred aspect of the present invention, in the structure of claim 1, the control means calculates the target viscosity compensating torque on the basis of the steering speed and the vehicle speed, and when the vehicle speed is less than the reference value. The target viscosity compensation torque is set to 0, and the reference value when the steering cycle is within the predetermined range is configured to be larger than the reference value when the steering speed is outside the predetermined range (preferred aspect 8).

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1 is a schematic configuration diagram showing an embodiment of an electric power steering apparatus according to the present invention.

In FIG. 1, 10FL and 10FR respectively indicate left and right front wheels which are steering wheels.
FL and 10FR are steering wheel 12 by the driver
The tie rods 18L and 1L are driven by the rack-and-pinion type electric power steering unit 16 driven via the steering shaft 14 in response to the operation of
It is steered via 8R. The power steering unit 16 includes a pinion shaft 20 and a rack bar 22, and the pinion shaft 20 is the steering shaft 14.
The rotation is converted into reciprocating motion of the rack bar 22 by the steering gear box 24.

In the illustrated embodiment, the electric power steering unit 16 is a rack coaxial type electric power steering unit, and the electric motor 26 and the rotational torque of the electric motor 26 are applied to the reciprocating direction of the rack bar 22. And a conversion mechanism 28 of, for example, a ball screw type for generating an auxiliary steering force for driving the rack bar 22 relative to the rack housing 30, thereby reducing the steering burden on the driver. Generates auxiliary steering torque.
The electric power steering unit may be of any configuration known in the art, such as a pinion assist type or a column assist type, as long as it can generate an auxiliary steering torque.

In the illustrated embodiment, the steering shaft 14 is provided with a torque sensor 32 for detecting the torque of the steering shaft as steering torque Ts, and the output of the torque sensor 32 is a micro controller of the electronic control unit 34. It is supplied to the computer 36. A signal indicating the vehicle speed V detected by the vehicle speed sensor 38 is also input to the microcomputer 36.

The electronic control unit 34 has a microcomputer 36 and a drive circuit 40, and the microcomputer 3
Reference numeral 6 may have a general configuration including a CPU, a ROM, a RAM, and an input / output port device, which are connected to each other by a bidirectional common bus. The drive circuit 40 includes a voltmeter 42 for detecting the voltage value Vd and the current value Id of the drive current output from the drive circuit to the electric motor 26.
Also, a signal having a built-in ammeter 44 and showing the voltage value Vd detected by the voltmeter 42 and the current value Id detected by the ammeter 44 is also supplied to the microcomputer 36.

As will be described in detail later, the microcomputer 36 provides steering assist torque Ta and steering resistance according to the steering speed for reducing the steering burden on the driver according to the control routine shown in FIG. The viscosity compensation torque Td of the electric power steering unit 16 is calculated, and the electric motor 26 of the electric power steering unit 16 is controlled based on the target control torque Tc, which is the sum of these, to control the torque assist by the electric power steering unit 16. The torque sensor 32 detects the steering torque Ts when the steering in the left turning direction of the vehicle is positive.

Particularly in the illustrated embodiment, the microcomputer 36 is based on the voltage value Vd detected by the voltmeter 42 and the current value Id detected by the ammeter 44, and is well known in the art. At electric motor 26
The rotational angular velocity ωm of the
The steering speed ω is calculated as the rotational angular speed of the steering shaft 14 based on the gear ratio of the steering gear box 8 and the gear ratio of the steering gear box 24. The steering speed ω is also positive in the direction of increasing the left turn.

Next, the control routine of the electric power steering apparatus in the illustrated embodiment will be described with reference to the flow chart shown in FIG. The control according to the flowchart shown in FIG. 2 is started by closing an ignition switch (not shown) and is repeatedly executed at predetermined time intervals.

First, in step 10, the steering torque T
The signal indicating s is read, and in step 20, the auxiliary steering torque for reducing the steering burden on the driver is obtained from the map corresponding to the graph shown in FIG. 3 based on the steering torque Ts and the vehicle speed V. Ta is calculated and step 3
At 0, the voltage value Vd detected by the ammeter 42,
The steering speed ω is calculated based on the current value Id and the like detected by the ammeter 44.

In step 40, it is judged whether the steering direction is reversed or not by judging whether the sign of the steering speed ω is reversed from positive to negative or from negative to positive, and a negative judgment is made. If so, the process proceeds to step 110, and if an affirmative determination is made, the process proceeds to step 50.

In step 50, the elapsed time from the time when it is determined whether the timer is operating, that is, it is determined in step 40 that the steering direction is reversed, is counted. Whether or not it is determined, and when a negative determination is made, the timer count is started in step 60, and when an affirmative determination is made, the previous steering direction is determined based on the timer count value in step 70. The steering cycle Pc is calculated as twice the time (steering half cycle) from the time when the vehicle turns to the time when the steering direction turns this time.

In step 80, it is detected within the time corresponding to the steering half cycle calculated in step 70, that is, between the time point of the previous steering direction reversal and the time point of the current steering direction reversal. The torque peak Tp is calculated as the maximum value of the steering torque Ts, and in step 90, the count value of the timer is reset to 0 and then the timer is stopped.

Generally, if the steering cycle is the same, the larger the torque peak Tp, the larger the steering range (amplitude), and the maximum value of the magnitude of the steering speed ω detected within the steering half cycle, that is, the steering described later. Since the steering range (amplitude) increases as the speed peak ωp increases, the torque peak Tp and the steering speed peak ωp are values indicating the steering range when the driver repeatedly performs reciprocal steering.

In step 100, it is determined whether the steering cycle Pc is greater than or equal to the first reference value Pc1 and less than or equal to the second reference value Pc2, that is, the steering cycle Pc is due to rotational resonance vibration of the steering system. It is determined whether or not the vehicle is within a predetermined steering cycle range in which yaw resonance vibration may occur. If a positive determination is made, the process proceeds to step 140, and if a negative determination is made, step 110 is performed. Go to. The predetermined steering cycle range defined by the reference values Pc1 and Pc2 is a range including one or preferably both of the steering cycle corresponding to the rotational resonance frequency of the steering system and the steering cycle corresponding to the yaw resonance frequency of the vehicle. Is set to.

In step 110, the basic viscosity compensation torque Tdb during normal steering is calculated from the map corresponding to the graph shown in FIG. 4 based on the steering speed ω, and step 1
In step 20, the vehicle speed coefficient Kv is calculated from the map corresponding to the graph shown in FIG. 5 based on the vehicle speed V, and in step 130, the torque peak coefficient Kt is 0.5, for example.
Is set to a preset constant such as, and then the process proceeds to step 170.

At step 140, the basic viscosity compensation torque Tdb for preventing the rotational resonance vibration of the steering system and the yaw resonance vibration of the vehicle is determined from the map corresponding to the graph shown in FIG. 6 based on the steering speed ω. Calculated, step 15
At 0, the vehicle speed coefficient Kv is calculated based on the vehicle speed V,
In step 160, the torque peak coefficient Kt as a coefficient based on the steering range is calculated from the map corresponding to the graph shown in FIG. 8 based on the torque peak Tp.

In step 170, the viscosity compensation torque Td is calculated according to the following equation 1, and in step 180, the previous value and the present value of the viscosity compensation torque Td are Td (n-1) and Td (n), respectively. ) And the filter constant is R, and the low-pass filter processing is performed in accordance with the following equation 2 to obtain the viscosity compensation torque T after the low-pass filter processing.
df is calculated. Td = Kv · Kt · Tdb …… (1) Tdf = (1-R) Td (n-1) + R · Td (n) …… (2)

In step 190, the target control torque Tc is calculated as the sum of the auxiliary steering torque Ta and the viscosity compensating torque Tdf after the low pass filter processing according to the following equation 3, and in step 200 the target control torque Tc is calculated.
The target voltage of the drive current for the electric motor 26 is calculated based on the above, and the drive current for the electric motor 26 is controlled by PI based on the target voltage, for example, as well known in the art. Is controlled to a target control torque Tc. Tc = Ta + Tdf (3)

Thus, according to the illustrated embodiment, it is determined in steps 30 and 40 whether or not the steering direction is reversed based on the steering speed ω, and when it is determined that the steering direction is reversed, steps 50 and At 60, the timer starts counting. Then, when it is determined that the steering direction is further reversed, an affirmative determination is made in steps 40 and 50, the steering cycle Pc is calculated in step 70, and the steering cycle is determined by the rotational resonance vibration of the steering system. It is determined whether or not the vehicle is within a predetermined steering cycle range that may cause yaw resonance vibration of the vehicle.

When the steering cycle is not within the predetermined range,
Since there is no risk that the steering system will vibrate in rotational resonance or the yaw vibration in the vehicle, a negative determination is made in step 100, and in step 110 the basic viscosity compensation during normal steering is performed based on the steering speed ω. The torque Tdb is calculated, the vehicle speed coefficient Kv is calculated in step 120 so that the vehicle speed becomes higher as the vehicle speed increases, the torque peak coefficient Kt is set to a constant value in step 130, and the basic viscosity compensation is performed in step 170. The viscosity compensation torque Td is calculated as the product of the torque Tdb, the vehicle speed coefficient Kv, and the torque peak coefficient Kt.

Then, in step 180, the viscosity compensation torque Td is low-pass filtered, and step 190
In step 120, vehicle speed V and steering torque Ts
The target control torque Tc is calculated as the sum of the auxiliary steering torque Ta calculated on the basis of the above and the viscosity compensation torque Td after the low pass filter processing, and the electric motor 26 is controlled based on the target control torque Tc at step 200.

On the other hand, when the steering cycle is within a predetermined steering cycle range that may cause rotational resonance vibration of the steering system or yaw resonance vibration of the vehicle, a positive determination is made in step 100, Steering speed ω in step 140
Is calculated, a basic viscosity compensation torque Tdb for preventing yaw resonance vibration of the vehicle is calculated so that sufficient viscosity compensation is performed even in a region where the vehicle speed is relatively small, and the vehicle speed V is relatively high in step 150. In the region, the vehicle speed coefficient Kv is calculated so that the vehicle speed becomes higher as the vehicle speed becomes higher.
In this case, when the torque peak Tp is equal to or greater than the reference value, the torque peak coefficient Kt that is larger than 1 as the torque peak becomes higher is calculated, and steps 170 to 200 are executed as in the case of normal steering.

Therefore, when the driver repeatedly performs the reciprocal steering at the steering frequency that may cause the rotational resonance vibration of the steering system and the yaw resonance vibration of the vehicle, the viscosity compensation torque Td is lower than that in the normal steering. Since it is calculated to a large value, the subsequent rotational vibration of the steering system and the yaw direction vibration of the vehicle are effectively damped, which causes the steering system to rotationally vibrate and the vehicle to yaw and vibrate. It is possible to effectively prevent deterioration of running stability, and even if the driver repeatedly performs reciprocal steering, the steering frequency may cause rotational resonance vibration of the steering system or yaw resonance vibration of the vehicle. When the steering frequency does not exist, the viscosity compensating torque Td is calculated to the value at the time of normal steering, so that it is possible to reliably prevent the steering reaction force from becoming excessively high.

In particular, according to the illustrated embodiment, the steering cycle is determined by the reversal of the steering direction, and the reversal of the steering direction is determined by the sign reversal of the steering speed ω, and accordingly, the steering necessary for the calculation of the basic viscosity compensation torque Tdb. Since the steering cycle is determined by using the speed ω, it is not necessary to detect the steering angle by, for example, the steering angle sensor to determine the steering cycle. The structure of the power steering device can be simplified and the cost can be reduced.

According to the illustrated embodiment, the vehicle speed coefficient Kv is calculated based on the vehicle speed V, the torque peak coefficient Kt indicating the steering range as the degree of steering is calculated, and the viscosity compensation torque Td is the basic viscosity compensation torque Tdb. Is calculated as the product of the vehicle speed coefficient Kv and the torque peak coefficient Kt. The torque peak coefficient Kt is 1 when the torque peak Tp is less than or equal to the reference value.
When the torque peak Tp is greater than the reference value, the steering frequency is set to a value greater than 1. Therefore, the steering frequency is a steering frequency that may cause rotational resonance vibration of the steering system or yaw resonance vibration of the vehicle. However, when the steering range is small and there is no fear that the steering system will vibrate in rotational resonance or the vehicle will yaw in resonance, it is possible to reliably prevent the viscosity compensation torque Td from becoming excessively large. It is possible to reliably prevent the steering reaction force from becoming excessive.

According to the illustrated embodiment, the viscosity compensation torque Td is low-pass filtered, and the target control torque Tc is calculated as the sum of the auxiliary steering torque Ta and the low-pass filtered viscosity compensation torque Tdf. It is possible to reliably prevent the value of the basic viscosity compensation torque Tdb from abruptly changing due to the change of the determination in step 100, and to prevent the value of the viscosity compensation torque Td from abruptly changing due to this. It is possible to reliably prevent a sudden change in the reaction torque that the user feels.

According to the illustrated embodiment, the rotational angular velocity ωm of the electric motor 26 is calculated based on the voltage value Vd and the current value Id of the drive current output to the electric motor 26, and the rotational angular velocity ωm and the conversion mechanism 28 and Since the steering speed ω is calculated on the basis of the gear ratio of the steering gear box 24, a special sensor for detecting the steering speed is not necessary. Therefore, this also reduces the number of necessary sensors and reduces the electric power. The structure of the steering device can be simplified and the cost can be reduced.

Further, according to the illustrated embodiment, the basic viscosity compensation torque Tdb is calculated based on the steering speed ω, and is set to 0 when the magnitude of the steering speed ω is less than the reference value, and the steering cycle is within a predetermined range. Since the reference value when the steering speed is outside the predetermined range is smaller than the reference value when the steering speed is out of the predetermined range, there is a possibility that the steering cycle is within the predetermined range and rotational resonance vibration of the steering system and yaw resonance vibration of the vehicle occur. In a certain situation, it is possible to reliably secure the necessary viscosity compensating torque, so that the rotational resonance vibration of the steering system and the yaw resonance vibration of the vehicle can be reliably prevented.

In general, the yaw resonance vibration of the vehicle does not occur when the vehicle speed is low, but easily occurs in the high vehicle speed range. According to the illustrated embodiment, as can be seen from the comparison between FIG. 5 and FIG. 7, the reference vehicle speed at which the vehicle speed coefficient Kv is larger than 0 has a steering cycle within a predetermined range, and there is a risk of yaw resonance vibration of the vehicle. In some cases, the steering cycle is outside the predetermined range and is a larger value than in normal steering where there is no risk of yaw resonance vibration of the vehicle.Therefore, an appropriate steering reaction force is generated during normal steering during medium-high speed traveling. In addition, it is possible to effectively prevent yaw resonance vibration of the vehicle when reciprocating steering is performed in a steering cycle within a predetermined range in a high vehicle speed range, and at a steering cycle within a predetermined range. It is possible to reliably prevent the steering reaction force from unnecessarily becoming excessively high in a situation where the vehicle speed is in the medium to low speed range and there is no fear of yaw resonance vibration of the vehicle even when the reciprocal steering is performed.

Although the present invention has been described above in detail with respect to specific embodiments, the present invention is not limited to the above-mentioned embodiments, and various other embodiments are also possible within the scope of the present invention. It will be apparent to those skilled in the art that

For example, in the above-described embodiment, the steering cycle is determined by reversing the steering direction, and the reversal of the steering direction is determined by reversing the sign of the steering speed ω. May be determined based on information other than the sign reversal of the steering speed ω, and the steering cycle may be determined by a method other than the reversal determination of the steering direction.

Further, in the above embodiment, the voltage value Vd and the current value Id of the drive current output to the electric motor 26.
The rotational angular velocity ωm of the electric motor 26 is calculated based on
The steering speed ω is calculated on the basis of the rotation angular velocity ωm and the gear ratio of the conversion mechanism 28 and the steering gear box 24. For the steering velocity, for example, a method of detecting the steering angle and calculating the rate of change thereof or the steering shaft. It may be detected in any manner known in the art, such as the method of detecting the rotational angular velocity of 14.

In the above embodiment, the vehicle speed coefficient Kv is calculated based on the vehicle speed V, the torque peak coefficient Kt indicating the steering range as the degree of steering is calculated, and the viscosity compensation torque Td is the basic viscosity compensation torque. It is designed to be calculated as the product of Tdb, the vehicle speed coefficient Kv, and the torque peak coefficient Kt, but the steering speed peak ωp is the maximum value of the steering speed ω detected within the time corresponding to the steering half cycle.
Is calculated and the steering speed peak ωp is used as a value indicating the size of the steering range. Instead of the torque peak coefficient Kt, the steering speed peak coefficient Ks as a coefficient based on the steering range.
May be calculated from the map corresponding to the graph shown in FIG. 9, and the viscosity compensation torque Td may be modified to be calculated according to the following equation 4. Td = Kv / Ks / Tdb (4)

Further, in the above embodiment, the target control torque Tc is calculated as the sum of the auxiliary steering torque Ta and the viscosity compensation torque Tdf after the low pass filter processing. Is the auxiliary steering torque Ta
In addition to the viscosity compensation torque Tdf, the torque for compensating the inertia of the electric motor 26, the torque for returning the steering wheel 12 to the neutral position, the torque for compensating the friction force of the steering system, and the like are calculated. May be.

In the above embodiment, the viscosity compensation torque Td is low-pass filtered, but the target control torque Tc is calculated as the sum of the auxiliary steering torque Ta and the viscosity compensation torque Td. , The target control torque Tc may be low-pass filtered, step 1
The determination similar to the determination of 00 may be corrected so as to be performed for the steering half cycle.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing one embodiment of an electric power steering device according to the present invention.

FIG. 2 is a flowchart showing a control routine of the electric power steering apparatus in the embodiment.

[FIG. 3] Vehicle speed V, steering torque Ts, and auxiliary steering torque Ta
7 is a graph showing the relationship between and.

FIG. 4 is a graph showing the relationship between the steering speed ω and the basic viscosity compensation torque Tdb during normal steering.

FIG. 5 is a graph showing a relationship between a vehicle speed V and a vehicle speed coefficient Kv during normal steering.

FIG. 6 is a graph showing the relationship between the steering speed ω and the basic viscosity compensation torque Tdb when there is a possibility that yaw resonance vibration of the vehicle will occur.

FIG. 7 is a graph showing a relationship between a vehicle speed V and a vehicle speed coefficient Kv when yaw resonance vibration of the vehicle is likely to occur.

FIG. 8 is a graph showing a relationship between a torque peak Tp and a torque peak coefficient Kt when a yaw resonance vibration of a vehicle may occur.

FIG. 9 is a graph showing the relationship between the steering speed peak ωp and the steering speed peak coefficient Ks when there is a risk of yaw resonance vibration of the vehicle.

[Explanation of symbols]

14 ... Steering shaft 16 ... Electric power steering unit 26 ... Electric motor 32 ... Torque sensor 34 ... Electronic control unit 36 ... Microcomputer 38 ... Vehicle speed sensor 40 ... Drive circuit 42 ... Voltmeter 44 ... Ammeter

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Claims (3)

[Claims] 1. An electric motor provided in a steering system between a steering wheel and a steered wheel for generating an auxiliary steering torque, a means for detecting the steering torque, a means for detecting a steering speed, and a target based on the steering torque. An electric power steering apparatus comprising: a control means for calculating a target torque of the electric motor based on a target viscosity compensation torque based on an auxiliary steering torque and a steering speed, and controlling the electric motor based on the target torque. The control means determines the steering cycle and a target viscosity compensation torque varying means for increasing the target viscosity compensation torque when the steering cycle is within a predetermined range as compared with when the steering cycle is outside the predetermined range. An electric power steering device comprising: 2. The target viscosity compensation torque varying means has means for estimating a steering range, and the increase amount of the target viscosity compensation torque is increased as the steering range is increased. Electric power steering device. 3. The means for determining the steering cycle determines the sign reversal of the steering speed detected by the means for detecting the steering speed, and steers twice the time interval between the sign reversals of the steering speeds. The electric power steering device according to claim 1, wherein the electric power steering device is determined as a cycle.