JP2010274842A - Electric power steering device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electric power steering device capable of stably continuing to give an assist force even in an alternative assist control during malfunction of a torque sensor with a simple constitution. <P>SOLUTION: A self-steer restraining control part 52 is provided with a self-steer determining part 53 for determining generation of self-steer based on a rotation angle speed ωm of a motor 21. When it is determined that the self-steer is generated, a self-steer restraining control is executed for reducing an assist force applied to a steering system. The self-steer restraining control part 52 also comprises a steer-keeping continuing time measuring part 57 for determining whether a condition of a steering operation of an operator is a steer-keeping condition or not and measuring its duration Tstb, and a threshold calculation part 58 for calculating a threshold ωth used for determining the self-steer based on the duration Tstb. Then, the threshold calculation part 58 calculates the threshold ωth decreased according to increase of the duration Tstb of the steer-keeping condition. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an electric power steering apparatus.

  2. Description of the Related Art Conventionally, power steering apparatuses for vehicles include an electric power steering apparatus (EPS) using a motor as a drive source. Usually, in such EPS, a torque sensor is provided in the middle of the steering shaft, and the assist force applied to the steering system is controlled based on the detected steering torque. For this reason, if any abnormality occurs in the torque sensor, the power assist control must be stopped if there is nothing to do.

  Therefore, conventionally, various methods for executing alternative assist control based on the steering angle detected by the steering sensor when an abnormality occurs in the torque sensor are proposed.

  For example, the EPS described in Patent Document 1 calculates a control target value that substitutes for the steering torque based on the steering angle and the steering speed. Further, Patent Document 2 discloses a configuration in which the steering torque is alternatively detected by calculating the torsion bar twist angle from the steering angle and the motor angle. Then, by executing the alternative assist control based on such a steering angle, it is possible to continuously apply assist force to the steering system even when the torque sensor is abnormal.

JP 2004-338562 A JP 2005-219573 A JP 2009-12511 A

  By the way, normally, the detection accuracy of the steering angle by the steering sensor is significantly coarser than the detection accuracy of each rotation angle sensor constituting the torque sensor. This is because the influence of the minute change in the steering angle on the running state of the vehicle is extremely limited, and therefore, in general vehicle control, its detection accuracy is extremely rare. Therefore, if the torsion angle of the torsion bar is to be calculated from the steering angle as in Patent Document 2, the steering sensor must be required to have a detection accuracy that is normally excessive.

  On the other hand, in the configuration in which an alternative control target value is calculated based on the steering angle as in Patent Document 1, the calculation of the control target value is mainly indicated by the steering angle (and the steering speed and changes thereof). This is done by estimating the steering state. For this reason, as in the case of the general vehicle control described above, the steering sensor does not require excessive detection accuracy, and as a result, there is an advantage that an increase in cost for ensuring detection accuracy can be avoided.

  However, in the alternative assist control using the control target value based on the estimation of the steering state, the assist force applied to the steering system is not fed back to the control, and the assist force may be excessive or insufficient. In particular, when the assist force is excessive, the driver may be anxious due to the occurrence of so-called self-steering before the steering operation.

  Therefore, for example, the rotation angle on the steered wheel side of the torsion bar is detected using a rotation angle sensor or the like provided in a motor that is a drive source. If the change in the rotation angle precedes the change in the steering angle, it is possible to determine that the self-steering has occurred and reduce the assist force applied to the steering system.

  However, as described above, the detection accuracy of the steering angle detected by the steering sensor is rough in comparison with the rotation angle on the steered wheel side detected by the rotation angle sensor (mainly resolver) of the motor. Furthermore, because of the required detection accuracy, in many cases, the rotation angle sensor rotor (for example, a salient pole or magnet for a magnetic type, a slit plate for an optical type) and a steering shaft are often used. There is a gap in the circumferential direction between them, and in the detection of the rotation angle, the rotation play caused by this becomes obvious as a delay in rising. Therefore, in order to detect the occurrence of self-steer at an early stage and to quickly suppress and stably apply the assist force, there is a problem that the accuracy of the steering sensor cannot be avoided. In addition, there was room for improvement.

  The above-mentioned Patent Document 2 discloses a configuration for calculating the reference position of the steering angle and the rotation angle on the steered wheel side when the torque sensor is normal. Patent Document 3 discloses a configuration in which an amount obtained by replacing the amount of elastic deformation generated by the gear backlash and the damper mechanism with an angle is used as a correction value in the calculation of the alternative steering torque.

  However, the prior art disclosed in the above-mentioned Patent Document 2 merely confirms the reference position for calculating the torsion angle of the torsion bar, and the prior art disclosed in the above-mentioned Patent Document 3 does not use the EPS. An object of the present invention is to solve the problems existing in the speed change mechanism of the actuator. Therefore, none of these conventional techniques solves the problems caused by the roughness of the detection accuracy of the steering sensor and the presence of the rotation play as described above.

  The present invention has been made to solve the above-described problems, and its purpose is to continue providing assist force stably even during alternative assist control when the torque sensor is abnormal with a simple configuration. An object of the present invention is to provide an electric power steering that can be used.

  In order to solve the above-mentioned problems, the invention according to claim 1 is directed to a torque sensor that detects a steering torque based on a twist of a torsion bar provided in the middle of a steering shaft, and a steered wheel side of the torsion bar. A steering force assisting device for applying an assist force for assisting a steering operation to the steering system; a control means for controlling the operation of the steering force assisting device based on the detected steering torque; and detecting an abnormality in the torque sensor And a steering sensor that detects a rotation angle of the steering, and the control means executes alternative assist control based on the rotation angle of the steering when an abnormality of the torque sensor is detected. In an electric power steering device, a rotational angular velocity of a motor that is a drive source of the steering force assisting device is detected. A rotation angular velocity detection unit; and a determination unit that determines whether or not the steering operation state is a steered state based on a rotation state of the steering, and the control unit has the steering operation state in a steered state. In spite of this, the gist is to reduce the assisting force applied to the steering system when the rotational angular velocity of the motor exceeds a predetermined threshold.

That is, the self-steer becomes apparent when the driver recognizes the situation where the steering by the motor drive precedes the steering operation. The driver tends to feel the self-steer particularly when the steering angle (steering angle) is kept constant, that is, when the steering operation is in the steered state. Therefore, as in the above-described configuration, by focusing on the state where the steering operation is in the steered state, it is possible to accurately detect the occurrence of self-steer even when the detection accuracy of the steering sensor is low. Can do. As a result, with a simple configuration, the assist force can be stably applied even during alternative assist control when the torque sensor is abnormal.

  Invention of Claim 2 is provided with the measurement means which measures the duration of the said holding state, and the calculating means which calculates the threshold value which falls according to the length of the said duration, The said control means is the said The gist is to compare the rotational angular velocities of the motors using the threshold value calculated by the calculation means.

  In other words, the tendency for the driver to feel self-steering during steering is more prominent as the steering state lasts longer. In this regard, according to the above configuration, as the steering state continues, it becomes easier to determine that self-steering has occurred, and as a result, the occurrence of self-steering can be detected more accurately.

  According to a third aspect of the present invention, there is provided a torque sensor for detecting a steering torque based on a twist of a torsion bar provided in the middle of the steering shaft, and for assisting a steering system in a steering system on a steered wheel side with respect to the torsion bar. A steering force assisting device for applying an assist force, control means for controlling the operation of the steering force assisting device based on detected steering torque, an abnormality detecting means for detecting an abnormality of the torque sensor, and rotation of the steering wheel A steering sensor that detects an angle, and the control means, in the case where an abnormality of the torque sensor is detected, in the electric power steering apparatus that performs alternative assist control based on the rotation angle of the steering, Rotational angular velocity detection means for detecting the rotational angular velocity of a motor that is a drive source of the auxiliary device; Measuring means for determining whether or not the steering operation state is the steered state based on the rotation state of the tearing, and measuring the duration of the steered state, and the control means includes the length of the duration Accordingly, the gist is to reduce the assist force applied to the steering system.

  In other words, the driver tends to feel stronger self-steer as the steered state continues longer. Therefore, as in the above configuration, it is effective to reduce the assist force applied to the steering system in advance according to the high possibility of the occurrence of the self-steering, that is, the length of the duration of the steering holding state. In addition, self-steer can be suppressed. As a result, it is possible to continue the application of assist force even in alternative assist control when the torque sensor is abnormal in a simpler and more stable configuration.

The gist of the invention described in claim 4 is that the control means reduces the assist force applied to the steering system as the steering approaches the neutral position.
That is, as the steering approaches the neutral position, the road surface reaction force acting on the steered wheels decreases, and the assist force requirement also decreases. Therefore, according to the above configuration, self-steering can be more effectively suppressed without impairing the steering feeling.

  According to a fifth aspect of the present invention, the control means compares the degree of reduction of the assist force according to the length of the duration time and the degree of reduction of the assist force according to the proximity state to the neutral position of the steering. Then, the gist is to select and execute the smaller one of the reduction degree.

That is, the road surface reaction force acting on the steered wheels becomes larger as the steered angle is larger, that is, as the steering rotation angle (absolute value) is larger. Therefore, if the assist force is unconditionally reduced as the duration of the steered state increases, for example, during steady turning, particularly when the turning radius is small, the driver's burden is reduced due to the lack of assist force. May increase. However, according to the said structure, generation | occurrence | production of such insufficient assist force can be suppressed. As a result, the effectiveness of the self-steer suppression control can be enhanced.

  According to the present invention, it is possible to provide an electric power steering capable of stably continuing application of assist force with a simple configuration even during alternative assist control when the torque sensor is abnormal.

The schematic block diagram of an electric power steering device (EPS). The control block diagram of EPS in 1st Embodiment. The flowchart which shows the process sequence of a steering maintenance state continuation time measurement. Explanatory drawing which shows the relationship between a holding state continuation time and a motor rotation angular velocity threshold value. The flowchart which shows the process sequence of self-steer determination. The control block diagram of EPS in 2nd Embodiment. Explanatory drawing which shows the relationship between a holding state continuation time and a suppression gain. Explanatory drawing which shows the relationship between a steering angle and a steering angle gain. The block diagram which shows the structure of the self-steer suppression control part of another example. The block diagram which shows the structure of the self-steer suppression control part of another example. Explanatory drawing which shows the relationship between a vehicle speed and a vehicle speed gain.

[First Embodiment]
Hereinafter, a first embodiment in which the present invention is embodied in a column-type electric power steering apparatus (EPS) will be described with reference to the drawings.

  As shown in FIG. 1, in the electric power steering apparatus (EPS) 1 of the present embodiment, a steering shaft 3 to which a steering 2 is fixed is connected to a rack shaft 5 via a rack and pinion mechanism 4, and the steering The rotation of the steering shaft 3 accompanying the operation is converted into a reciprocating linear motion of the rack shaft 5 by the rack and pinion mechanism 4. The steering shaft 3 of this embodiment is formed by connecting a column shaft 8, an intermediate shaft 9, and a pinion shaft 10. The reciprocating linear motion of the rack shaft 5 accompanying the rotation of the steering shaft 3 is transmitted to a knuckle (not shown) via tie rods 11 connected to both ends of the rack shaft 5, whereby the steered angle of the steered wheels 12. Has been changed.

  The EPS 1 is an EPS actuator 22 serving as a steering force assisting device that applies an assist force for assisting a steering operation to the steering system using the motor 21 as a drive source, and a control unit that controls the operation of the EPS actuator 22. ECU23.

  The EPS actuator 22 of the present embodiment is a so-called column type EPS actuator, and a motor 21 as a driving source thereof is drivingly connected to the column shaft 8 via a speed reduction mechanism 24. The rotation of the motor 21 is decelerated by the speed reduction mechanism 24 and transmitted to the column shaft 8 so that the motor torque is applied as an assist force to the steering system.

On the other hand, a vehicle speed sensor 27, a torque sensor 28, and a steering sensor (steering angle sensor) 29 are connected to the ECU 23. The ECU 23 is based on output signals from these sensors, and the vehicle speed V, steering torque τ, and steering. 2 is detected, that is, the steering angle θs.

  More specifically, in the present embodiment, a torsion bar 30 is provided in the middle of the column shaft 8, specifically, closer to the steering 2 side than the speed reduction mechanism 24. The torque sensor 28 of this embodiment is configured as a so-called twin resolver type torque sensor including a pair of rotation angle sensors (resolvers) 31 and 32 provided at both ends of the torsion bar 30.

  That is, the ECU 23 detects the rotation angles at both ends of the torsion bar 30 based on the output signals Sa and Sb of the rotation angle sensors 31 and 32 constituting the torque sensor 28. Then, the steering torque τ is detected based on the difference between the two rotation angles, that is, the twist angle of the torsion bar 30.

  Further, the steering sensor 29 of the present embodiment includes a rotor 33 fixed to the column shaft 8 on the steering 2 side with respect to the torque sensor 28, and a Hall IC 34 that detects a change in magnetic flux accompanying the rotation of the rotor 33. And a magnetic rotation angle sensor. In the steering sensor 29 of the present embodiment, the rotor 33 is provided with a plurality of salient poles.

  Then, the ECU 23 calculates a target assist force based on each detected state quantity, and supplies the drive power to the motor 21 that is the drive source in order to cause the EPS actuator 22 to generate the target assist force. The operation of the EPS actuator 22, that is, the assist force applied to the steering system is controlled.

Next, an aspect of assist control in the EPS of the present embodiment will be described.
As shown in FIG. 2, the ECU 23 includes a microcomputer 41 that outputs a motor control signal, and a drive circuit 42 that supplies drive power to the motor 21 that is a drive source of the EPS actuator 22 based on the motor control signal. Configured.

In the present embodiment, the ECU 23 includes a current sensor 43 for detecting the actual current value I supplied to the motor 21 and a rotation angle sensor 44 (see FIG. 1) for detecting the rotation angle θm of the motor 21. It is connected. The microcomputer 41 outputs to the drive circuit 42 based on each vehicle state quantity and the actual current value I and the rotation angle θm of the motor 21 detected based on the output signals of the current sensor 43 and the rotation angle sensor 44. A motor control signal is generated.

  Each control block shown below is realized by a computer program executed by the microcomputer 41. Then, the microcomputer 41 detects each state quantity at a predetermined sampling period, and generates a motor control signal by executing each arithmetic processing shown in the following control blocks at every predetermined period.

  More specifically, the microcomputer 41 calculates a current command value calculation unit 45 that calculates a current command value Iq *, which is a target value for power supply to the motor 21, and a current command value Iq * calculated by the current command value calculation unit 45. And a motor control signal output unit 46 for outputting a motor control signal based on the motor control signal.

The current command value calculation unit 45 is provided with a basic assist control unit 47 that calculates a basic assist control amount Ias * as a basic component of the assist force target value. In this embodiment, the basic assist control unit 47 is provided. Is input with a vehicle speed V and a steering torque τ.

Here, in the present embodiment, the output signals Sa and Sb of the torque sensor 28 are input to a steering torque detection unit 49 provided in the microcomputer 41, and the basic assist control unit 47.
The steering torque detection unit 49 receives the steering torque τ detected based on the output signals Sa and Sb. The basic assist control unit 47 is configured to calculate a basic assist control amount Ias * indicating that a larger assist force should be applied as the absolute value of the steering torque τ is larger and the vehicle speed V is smaller. Yes.

In the present embodiment, the steering torque detector 49 is provided with a function as an abnormality detection means for detecting an abnormality of the torque sensor 28 based on the output signals Sa and Sb of the torque sensor 28. The torque detector 49 outputs an abnormality detection signal Str indicating the detection result to the current command value calculator 45. The current command value calculation unit 45 indicates that the input abnormality detection signal Str is normal, that is, when the torque sensor 28 is operating normally, the basic assist control amount Ias. A value based on * is output to the motor control signal output unit 46 as the current command value Iq *.

On the other hand, the motor control signal output unit 46 includes the current command value Iq * output from the current command value calculation unit 45, the actual current value I detected by the current sensor 43, and the motor detected by the rotation angle sensor 44. A rotation angle θm of 21 is input. The motor control signal output unit 4
6 calculates a motor control signal by executing feedback control so that the actual current value I follows the current command value Iq *.

Specifically, in the present embodiment, a brushless motor that rotates by supplying three-phase (U, V, W) driving power is used as the motor 21. Then, the motor control signal output unit 46 converts the phase current values (Iu, Iv, Iw) of the motor 21 detected as the actual current value I into d, q axis current values in the d / q coordinate system (d / q The current feedback control is performed by performing conversion.

That is, the current command value Iq * is input to the motor control signal output unit 46 as a q-axis current command value, and the motor control signal output unit 46 determines the phase current value based on the rotation angle θm detected by the rotation angle sensor 44. (Iu, Iv, Iw) is d / q converted. The motor control signal output unit 46
Based on the d and q-axis current values and the q-axis current command value, the d and q-axis voltage command values are calculated. Then, the phase voltage command values (Vu *, Vv *, Vw *) are calculated by performing d / q inverse conversion on the d and q axis voltage command values, and a motor control signal is generated based on the phase voltage command values. To do.

  The motor control signal generated in this way is output from the microcomputer 41 to the drive circuit 42, and the drive circuit 42 supplies three-phase drive power based on the motor control signal to the motor 21. When the motor torque corresponding to the current command value Iq * as the assist force target value based on the steering torque τ is generated, the assist force corresponding to the assist force target value is applied to the steering system. ing.

In the present embodiment, the current command value calculation unit 45 is provided with an alternative assist control unit 50 that calculates an alternative assist control amount Isb * based on the steering angle θs detected by the steering sensor 29. Then, the current command value calculation unit 45 of this embodiment, when any abnormality occurs in the torque sensor 28, sets a value based on the alternative assist control amount Isb * calculated by the alternative assist control unit 50 to the current command Motor control signal output unit 46 as value Iq *
Output.

Specifically, in addition to the steering angle θs, the steering speed ωs and the vehicle speed V are input to the alternative assist control unit 50 of the present embodiment. In the present embodiment, the steering speed ωs is calculated by differentiating the steering angle θs detected by the steering sensor 29. Then, the substitute assist control unit 50 calculates the substitute assist control amount Isb * based on these state quantities. For details of the calculation of this alternative assist control amount Isb *,
For example, see the contents described in Patent Document 1 above.

Further, the current command value calculation unit 45 of the present embodiment is provided with a switching control unit 51, and the substitute assist control amount Isb * calculated by the substitute assist control unit 50 is calculated by the basic assist control unit 47. Basic assist control amount Ias * and the steering torque detector 4
9 is input to the switching control unit 51 together with the abnormality detection signal Str output by the reference numeral 9. When the input abnormality detection signal Str indicates that the torque sensor 28 is abnormal, the switching control unit 51 replaces the basic assist control amount Isas * with the alternative assist control amount Isb *. It is the composition to output.

Here, as described above, the calculation of the alternative assist control amount Isb * based on the steering angle θs is basically based on the estimation of the steering state via the steering angle θs. For this reason, the assist force applied to the steering system is not fed back to the alternative assist control, and as a result, there is a possibility that so-called self-steering occurs due to excessive assist force application.

  Therefore, the current command value calculation unit 45 of the present embodiment is provided with a self-steer suppression control unit 52 in order to suppress the occurrence of such self-steer. When self-steer occurs, the self-steer suppression control executed by the self-steer suppression control unit 52 reduces the assist force applied to the steering system, thereby suppressing the occurrence of self-steer. .

More specifically, the self-steer suppression control unit 52 of this embodiment includes a self-steer determination unit 53 that determines whether or not self-steer has occurred, and a suppression gain calculation unit 54 that calculates a suppression gain Kslf according to the result of the self-steer determination. And. And the self-steer suppression control part 5
2 is configured to execute the self-steer suppression control by outputting the suppression gain Kslf to the multiplier 56 and multiplying it by the alternative assist control amount Isb * output from the alternative assist control unit 50.

More specifically, in this embodiment, the rotational angular velocity ωm of the motor 21 is input to the self-steer determination unit 53. In the present embodiment, the rotational angular velocity ωm is obtained by differentiating the rotational angle θm of the motor 21 detected by the rotational angle sensor 44. That is, in this embodiment, the rotational angular velocity detection means is formed in the microcomputer 41. Then, the self-steer determination unit 53 executes the self-steer determination based on the rotational angular velocity ωm.

Further, the self-steering suppression control unit 52 of the present embodiment determines whether or not the steering operation state (steering state) by the driver is the steering holding state, and measures the duration Tstb thereof. A measurement unit 57 and a threshold value calculation unit 58 as calculation means for calculating the threshold value ωth used for the self-steer determination based on the duration time Tstb are provided.

  Specifically, as shown in the flowchart of FIG. 3, the steering continuation time measurement unit 57 of the present embodiment that constitutes the determination unit and the measurement unit acquires the steering speed ωs as a signal indicating the rotation state of the steering 2. (Step 101, see FIG. 1), it is determined whether or not the absolute value (| ωs |) is smaller than a predetermined threshold value ω0 (Step 102).

Next, when the absolute value of the steering speed ωs is smaller than the predetermined threshold value ω0 (| ωs | <ω0, step 102: YES), it is subsequently determined whether or not the steering flag has already been set. (Step 103). If the steering flag has not been set yet (step 103: NO), the steering flag is set (step 104), and the counter for measuring the duration Tstb of the steering state is incremented. (Tstb = Tstb + 1, Step 1
05). If it is determined in step 103 that the steering flag has already been set (step 103: YES), that is, if the duration Tstb is already being measured, the processing in step 104 is executed. In step 105, the counter is incremented.

On the other hand, if the absolute value of the steering speed ωs is greater than or equal to the threshold value ω0 in step 102 (| ωs | ≧ ω0, step 102: NO), the steering flag is reset (step 1).
06) and clearing the counter (Tstb = 0, step 107).

Then, the steering continuation time measurement unit 57 outputs the counter value updated by the execution of step 105 or step 107 to the threshold value calculation unit 58 as the continuation time Tstb in the steering holding state (step 108).

In addition, the threshold value calculation unit 58 of the present embodiment performs the map calculation based on the duration time Tstb of the steered state measured by the steerage duration time measurement unit 57 as described above, thereby obtaining the length of the duration time Tstb. A threshold value ωth that decreases accordingly is calculated. In the present embodiment, the threshold value ωth calculated by the threshold value calculation unit 58 rapidly decreases after the shift to the steered state, and thereafter, as the duration time Tstb becomes longer, the decrease width of the value decreases. Set to be smaller (
(See FIG. 4).

Then, the self-steer determination unit 53 of the present embodiment performs the self-steer determination based on the comparison between the threshold value ωth thus calculated and the rotational angular velocity ωm of the motor 21.
That is, the self-steer becomes apparent when the driver recognizes the situation where the steering by the motor drive precedes the steering operation. When the driver keeps the steering angle θs constant, i.e., when the steering operation is in the steered state, the driver can easily feel the self-steer, and the tendency is that the steered state continues for a long time. The more it becomes more prominent.

In consideration of this point, the self-steer determination unit 53 of the present embodiment causes the motor 21 to rotate even though the steering operation state is the steered state (the rotation state of the steering wheel 2 is substantially stopped). If it is, it is determined that self-steering has occurred. And it is the structure which aims at the improvement of the determination precision by changing threshold value (omega) th used for the self-steer determination to a small value, so that the continuation time Tstb of a steered state is long.

Specifically, as shown in the flowchart of FIG. 5, the self-steer determination unit 53 acquires the threshold value ωth calculated according to the rotational angular velocity ωm of the motor 21 and the duration time Tstb of the steered state (step 201, 202), it is determined whether the rotational angular velocity ωm (the absolute value thereof) exceeds a threshold value ωth (step 203). If the absolute value (| ωm |) of the rotational angular velocity ωm exceeds the threshold value ωth (| ωm |> ωth, step 203: YES), it is determined that self-steering has occurred (step 204). If it is equal to or less than ωth (| ωm | ≦ ωth, step 203: NO), it is determined that self-steering has not occurred (step 205).

As shown in FIG. 2, in the present embodiment, the determination result by the self-steer determination unit 53 is input to the suppression gain calculation unit 54 as the determination signal Sslf. Then, when the input determination signal Sslf indicates the occurrence of self-steering, the suppression gain calculating unit 54 calculates “0” as the suppression gain Kslf and indicates that no self-steering has occurred. In some cases, “1” is calculated as the suppression gain Kslf.

In the present embodiment, the abnormality detection signal Str output from the steering torque detector 49 is input to the self-steer suppression controller 52. The self-steer suppression control unit 52 is configured to output “1” as the suppression gain Kslf when the abnormality detection signal Str does not indicate abnormality of the torque sensor.

With this configuration, when self-steering occurs, the alternative assist control amount Isb * after multiplication by the suppression gain Kslf becomes “0”, and as a result, the current command value output from the current command value calculation unit 45 Iq * is also basically “0”. That is, when the driving power supplied to the motor 21 is stopped, the assisting is stopped. And in this embodiment, by this, it becomes the structure which can suppress generation | occurrence | production of a self-steer and can continue stable assist force provision at the time of torque sensor abnormality.

As described above, according to the present embodiment, the following operations and effects can be obtained.
(1) The self-steer suppression control unit 52 includes a self-steer determination unit 53 that determines the occurrence of self-steer based on the rotational angular velocity ωm of the motor 21, and determines that the self-steer has occurred. Self-steer suppression control is performed to reduce the applied assist force. In addition, the self-steer suppression control unit 52 determines whether or not the state of the steering operation by the driver is the steered state, and measures the duration Tstb thereof, and the duration duration Tstb. And a threshold value calculation unit 58 for calculating the threshold value ωth used for the self-steer determination. Then, the threshold value calculation unit 58 calculates a threshold value ωth that decreases as the duration time Tstb of the steered state becomes longer.

That is, the self-steer becomes apparent when the driver recognizes the situation where the steering by the motor drive precedes the steering operation. The driver tends to feel the self-steering particularly when the steering angle θs is held constant, that is, when the steering operation is in the steering holding state. Accordingly, by paying attention to the state where the steering is maintained as in the above configuration, it is possible to accurately detect the occurrence of self-steer even when the detection accuracy of the steering angle θs by the steering sensor 29 is low. Can do. As a result, with a simple configuration, the assist force can be stably applied even during alternative assist control when the torque sensor is abnormal.

  (2) In addition, the tendency for the driver to feel self-steering at the time of such steering is more prominent as the steering state continues longer. In this regard, according to the above configuration, as the steering state continues, it becomes easier to determine that self-steering has occurred, and as a result, the occurrence of self-steering can be detected more accurately.

[Second Embodiment]
Hereinafter, a second embodiment of the present invention will be described with reference to the drawings. For convenience of explanation, the same parts as those in the first embodiment are denoted by the same reference numerals, and the explanation thereof is omitted.

As shown in FIG. 6, the self-steer suppression control unit 62 of the present embodiment includes a self-steer determination unit 53 and a threshold value calculation unit 58 as seen in the self-steer suppression control unit 52 of the first embodiment. It is not provided, and the hold time duration Tstb measured by the hold duration measurement unit 57 is directly input to the suppression gain calculation unit 64. Then, the suppression gain calculation unit 64 of the present embodiment enhances the self-steer suppression control according to the length of the input duration time Tstb, that is, greatly reduces the assist force applied to the steering system. The suppression gain Kslf is calculated.

Specifically, as shown in FIG. 7, the suppression gain calculation unit 64 of the present embodiment, when the duration Tstb is “0”, that is, when the state of the steering operation is not the steering holding state,
“1” is calculated as the suppression gain Kslf. The value is set so as to gradually decrease as the duration Tstb becomes longer, more specifically, the decrease width increases in an accelerated manner, and finally becomes “0”.

That is, as described above, the driver tends to feel stronger self-steer as the steered state continues longer. In this embodiment, paying attention to this point, the assist force to be applied to the steering system in advance is reduced according to the high possibility of the occurrence of self-steering, that is, the length of the duration time Tstb in the steered state. . As a result, self-steering is effectively suppressed.

Further, as shown in FIG. 2, the self-steer suppression control unit 62 of the present embodiment has a steering angle θs (
A steering angle gain calculating unit 65 that calculates a steering angle gain Kstr corresponding to the absolute value of the steering angle gain Kstr, and a comparison output unit 66 that compares the steering angle gain Kstr with the suppression gain Kslf and outputs one of them. And.

Specifically, as shown in FIG. 8, the steering angle gain calculation unit 65 of the present embodiment has a value of “1” or less, that is, multiplies the substitute assist control amount Isb * in the same manner as the suppression gain Kslf. Thus, the steering angle gain Kstr that can reduce the assist force applied to the steering system is calculated. The steering angle gain Kstr increases as the absolute value (| θs |) of the detected steering angle θs increases.
It is set to be a larger value. In other words, the steering angle gain calculation unit 65 of the present embodiment provides a steering angle gain Kstr that greatly reduces the assist force applied to the steering system as the steering 2 approaches the neutral position (θs = 0). Calculate.

  Further, the comparison output unit 66 compares the magnitudes of the steering angle gain Kstr and the suppression gain Kslf, that is, the degree of reduction of the assist force, and determines the larger one, that is, the smaller one of the degree of reduction of the assist force. Select and output. The self-steer suppression control unit 62 of the present embodiment is configured to execute the self-steer suppression control based on the output of the comparison output unit 66, that is, to output to the multiplier 56.

As described above, according to the present embodiment, the following operations and effects can be obtained.
(1) The hold time duration Tstb measured by the hold duration measurement unit 57 is input to the suppression gain calculation unit 64. Then, the suppression gain calculation unit 64 enhances the self-steer suppression control according to the length of the input duration Tstb, that is, the assist force applied to the steering system is greatly reduced as the duration Tstb becomes longer. Suppression gain Kslf
Is calculated.

In other words, the driver tends to feel stronger self-steer as the steered state continues longer. Therefore, as described above, the effect of reducing the assist force applied to the steering system in advance according to the high possibility of the occurrence of self-steering, that is, the length of the duration time Tstb in the steered state. In particular, self-steer can be suppressed. As a result, it is possible to continue the application of assist force even in alternative assist control when the torque sensor is abnormal in a simpler and more stable configuration.

(2) The self-steer suppression control unit 62 calculates a steering angle gain Kstr that is larger and reduces the assist force applied to the steering system as the steering 2 approaches the neutral position (θs = 0). A gain calculation unit 65 is provided. Further, the self-steer suppression control unit 62 compares the magnitudes of the steering angle gain Kstr and the suppression gain Kslf, that is, the degree of reduction of the assist force, and the larger one, that is, the degree of reduction of the assist force is small. A comparison output unit 66 is provided for selecting and outputting the method. The self-steer suppression control unit 62 executes the self-steer suppression control based on the output of the comparison output unit 66.

  That is, the road surface reaction force acting on the steered wheels 12 increases as the steered angle increases, that is, as the steering angle θs (absolute value) increases. For this reason, if the assist force is unconditionally reduced as the duration time Tstb of the steered state becomes longer, for example, during steady turning, particularly when the turning radius is small, the driver's burden is reduced due to the lack of assist force. May increase. However, according to the said structure, generation | occurrence | production of such insufficient assist force can be suppressed. As a result, the effectiveness of the self-steer suppression control can be enhanced.

In addition, you may change each said embodiment as follows.
In each of the above embodiments, the present invention is embodied in a so-called column type EPS 1, but the present invention may be applied to a so-called pinion type or rack assist type EPS.

  In each of the above embodiments, a magnetic rotation angle sensor using the Hall IC 34 is used as the steering sensor 29. However, other types of rotation angle sensors such as an optical type may be used. .

In the first embodiment, the self-steer suppression control unit 52 determines whether or not the state of the steering operation by the driver is the steered state and measures the duration Tstb thereof, and the steered duration measurement unit 57 and a threshold value calculation unit 58 for calculating a threshold value ωth that decreases as the duration time Tstb increases. Then, the self-steer determination unit 53 determines the occurrence of self-steer based on the comparison between the threshold value ωth and the rotational angular velocity ωm of the motor 21.

However, the present invention is not limited to this, and a steered state determination unit 71 that determines whether or not the steering operation state is the steered state is provided as in the self-steer suppression control unit 70 shown in FIG. The determination result (signal Sstb indicating) is input to the unit 72. And the self-steer determination part 72 is good also as a structure which determines generation | occurrence | production of self-steering based on the comparison with the rotation angular velocity (omega) m of the motor 21, and a predetermined threshold value, when the said determination result is a steering hold state. Thereby, even when the detection accuracy of the steering angle θs by the steering sensor 29 is low, the occurrence of self-steer can be detected with a simpler configuration.

In the second embodiment, the self-steer suppression control unit 62 compares the suppression gain Kslf with the rudder angle gain Kstr, and selects and outputs a comparison output unit 66 that selects and outputs the smaller assist force reduction degree. The self-steer suppression control is executed based on the output of the comparison output unit 66. However, the present invention is not limited to this, and a configuration may be adopted in which the multiplier 75 multiplies the suppression gain Kslf and the steering angle gain Kstr and outputs the same as in the self-steer suppression control unit 74 shown in FIG. In this case, it goes without saying that it is desirable to appropriately optimize the magnitude of the steering angle gain Kstr (the scale of the map as shown in FIG. 8).

Furthermore, in addition to the steering angle gain Kstr, as shown in FIG. 11, a vehicle speed gain Kv that increases as the vehicle speed V increases may be calculated. That is, the road surface reaction force acting on the steered wheels 12 also increases as the vehicle speed V increases. Therefore, with such a configuration, the effectiveness of the self-steer suppression control can be further enhanced.

In each of the embodiments described above, the steering speed ωs is used as a signal indicating the rotation state of the steering wheel 2. However, by monitoring the change using the steering angle θs, is the steering operation state maintained in the steered state? It may be determined whether or not.

The relationship between the duration Tstb of the steering holding state and the threshold value ωth related to the rotational angular velocity ωm of the motor 21, the relationship between the duration Tstb and the suppression gain Kslf, and the steering angle θs (vehicle speed V) and the steering angle gain Kstr (vehicle speed gain Kv) ) Does not necessarily change to the curve shape shown in each figure (FIGS. 4, 7, 8 (, 11)) used in the description of the above embodiments. That is, for example, it may be a linear change or a step change.

Next, technical ideas that can be grasped from the above embodiments will be described together with effects.
(A) In the electric power steering apparatus according to claim 4, suppression gain calculating means for calculating a suppression gain that increases the degree of reduction of the assist force according to the length of the duration, and the steering in the neutral position Steering angle gain calculation means for calculating a steering angle gain that increases the degree of reduction of the assist force as it approaches, and the control means uses at least one of the continuous gain and the steering angle gain for the alternative assist control. An electric power steering apparatus, wherein the assist force is reduced by multiplying a control target value. As a result, it is possible to continue the application of assist force with a simple configuration and more stably even during alternative assist control when the torque sensor is abnormal.

DESCRIPTION OF SYMBOLS 1 ... Electric power steering device (EPS), 2 ... Steering, 3 ... Steering shaft, 8 ... Column shaft, 12 ... Steering wheel, 21 ... Motor, 22 ... EPS actuator, 23 ... ECU, 28 ... Torque sensor, 29 ... Steering Sensor 30. Torsion bar 41. Microcomputer 42 Drive circuit 45 Current command value calculation unit 46 Motor control signal output unit 47 Basic assist control unit 49 Steering torque detection unit 50 Alternative assist Control unit 51 ... Switching control unit 52, 62, 70, 74 ... Self-steer suppression control unit, 53, 72 ... Self-steer determination unit, 54, 64 ... Suppression gain calculation unit, 56 ... Multiplier, 57 ... Steering Duration time measurement unit, 58... Threshold value calculation unit, 65... Steering angle gain calculation unit, 66... Comparison output unit, 71. Iq *: current command value, Ias *: basic assist control amount, Isb *: alternative assist control amount, Kslf: suppression gain, Kstr: rudder angle gain, Kv: vehicle speed gain, θs: steering angle, ωs: steering speed, ω0 ... threshold, θm ... motor rotation angle, ωm ... rotation angular velocity, ωth ...
Threshold, τ ... steering torque, Sa, Sb ... output signal, Str ... abnormality detection signal, Tstb ... duration,
Sslf: Determination signal.

Claims (5)

A torque sensor for detecting a steering torque based on a twist of a torsion bar provided in the middle of the steering shaft, and a steering force assist for providing an assist force for assisting a steering system on the steered wheel side of the torsion bar. A control means for controlling the operation of the steering force assisting device based on the detected steering torque, an abnormality detection means for detecting an abnormality of the torque sensor, and a steering sensor for detecting the rotation angle of the steering. In the electric power steering apparatus, when the abnormality of the torque sensor is detected, the control means executes alternative assist control based on the rotation angle of the steering wheel.
A rotational angular velocity detecting means for detecting a rotational angular velocity of a motor that is a drive source of the steering force assisting device;
Determination means for determining whether or not the steering operation state is a steering holding state based on the rotation state of the steering wheel,
The control means reduces the assisting force applied to the steering system when the rotational angular velocity of the motor exceeds a predetermined threshold even though the steering operation is in the steered state. An electric power steering device. The electric power steering apparatus according to claim 1, wherein
Measuring means for measuring the duration of the steering holding state;
Calculating means for calculating a threshold value that decreases according to the length of the duration,
The electric power steering apparatus characterized in that the control means compares the rotational angular velocities of the motor using a threshold value calculated by the calculating means. A torque sensor for detecting a steering torque based on a twist of a torsion bar provided in the middle of the steering shaft, and a steering force assist for providing an assist force for assisting a steering system on the steered wheel side of the torsion bar. A control means for controlling the operation of the steering force assisting device based on the detected steering torque, an abnormality detection means for detecting an abnormality of the torque sensor, and a steering sensor for detecting the rotation angle of the steering. In the electric power steering apparatus, when the abnormality of the torque sensor is detected, the control means executes alternative assist control based on the rotation angle of the steering wheel.
A rotational angular velocity detecting means for detecting a rotational angular velocity of a motor that is a drive source of the steering force assisting device;
Measuring means for determining whether or not the steering operation state is a steering holding state based on the rotation state of the steering and measuring the duration of the steering holding state;
The electric power steering apparatus characterized in that the control means reduces an assist force applied to the steering system in accordance with the length of the duration. In the electric power steering device according to claim 3,
The electric power steering device according to claim 1, wherein the control means reduces an assist force applied to the steering system as the steering approaches a neutral position. In the electric power steering apparatus according to claim 4,
The control means compares the degree of reduction of the assist force according to the length of the duration and the degree of reduction of the assist force according to the proximity state to the neutral position of the steering, and determines the smaller of the reduction degree. An electric power steering apparatus characterized by being selected and executed.

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