JP2010254178A - Electric power steering device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electric power steering device that effectively prevents deviation of a vehicle with a simple structure and stably maintains a behavior of the vehicle even when a factor inducing the deviation is reversed. <P>SOLUTION: A current command value calculating unit includes a lead pull correction controlling unit for controlling lead pull correction to reduce steering torque detected when determining that a vehicle is in a going-straight state. The lead pull correction controlling unit calculates a lead pull correction amount Ilp* in the same direction as a direction of the detected steering torque when determining that the lead pull correction should be executed. Also, the lead pull correction controlling unit determines whether a direction of the lead pull correction amount Ilp* and a direction of horizontal acceleration Fs are different or not (step 204). When the directions are the same (Ilp*, the same Fs direction, step 204:NO) clears a value of the lead pull correction amount Ilp* (Ilp*=0, step 206). <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, the basic component (basic assist control amount) of the assist force applied to the steering system is calculated based on the detected steering torque.

  By the way, during actual traveling, there is a situation in which a steering operation for suppressing the deflection (lead pull) of the vehicle is required even though the vehicle is in a straight traveling state. For example, as shown in FIG. 7, the traveling path 31 of the vehicle 30 is often inclined in the width direction for reasons such as improved drainage performance. When doing so, a steering torque is required to suppress the deflection due to gravity. And when such a cant road driving | running | working takes a long time, the continuous load will be accumulate | stored in a driver | operator as fatigue.

  In order to solve such problems, conventionally, a method has been proposed in which a cant state of a vehicle travel path is determined and a control component for suppressing the deflection of the vehicle is calculated based on the determination result. For example, the vehicle control device described in Patent Literature 1 learns a cant state of a vehicle travel path based on a plurality of detected state quantities such as vehicle speed, lateral acceleration, steering state, and travel environment information. A cant state is determined by performing a neural network calculation using the learning result, and a control component for suppressing the deflection of the vehicle due to the presence of the cant is calculated.

  However, in a configuration that performs precise cant state determination as in the above-described conventional example, an increase in cost due to an increase in the calculation load is unavoidable, and this is realistic if the complexity of the configuration is considered. It is hard to say that it is a solution.

  Therefore, when it is determined that the vehicle is in the straight traveling state, a method of calculating a correction component for reducing the steering torque and superimposing the correction component on the basic component for assisting the steering operation can be considered.

  Specifically, for example, as shown in FIG. 8, when it is determined that the vehicle is in a straight traveling state, a correction component for reducing the steering torque from that point (time t1 in the figure). The lead pull correction amount is gradually increased. That is, as the lead pull correction amount increases, the force (steering torque) required for the driver to suppress the deflection of the vehicle gradually decreases. Then, by controlling the steering torque to finally become “0” (at the time indicated by time t2 in the figure), the vehicle can be deflected with a simple configuration without causing the driver to feel uncomfortable. Can be suppressed.

  In addition to the inclination of the traveling road surface as described above, factors that induce such vehicle deflection include, for example, crosswinds or unbalance of axles and vehicle weights. This can effectively suppress the deflection of the vehicle as a factor.

JP 2007-22169 A

  By the way, normally, the cant road as described above has a substantially chevron shape (saddle shape) in which the central portion in the width direction is the highest (see FIG. 7, in FIG. Part). For this reason, when performing a lane change across two adjacent lanes (32, 33) across the center in the width direction, the lead pull correction control as described above is a factor that hinders the stability of the vehicle behavior. There is a possibility of becoming.

  Specifically, for example, as shown in FIG. 9, in a cant road 34 in which the central portion 34C in the width direction is higher than the peripheral portions 34L and 34R, the vehicle travels on the left lane 32 (the upper lane in the figure) ( Consider a case where a vehicle 30 that goes straight ahead changes its travel lane to the right lane (lower lane in the figure) 33.

  In such a case, in the vehicle 30 before the lane change, lead pull correction for suppressing deflection due to the inclination of the traveling lane is performed. That is, when driving in the left lane 32 that is inclined from the right side to the left side (lower side to the upper side in the figure) toward the traveling direction, the driver is deflected toward the left side (upper side in the figure) due to the inclination. In order to suppress the behavior of the vehicle 30 to be tried, a steering torque in the right direction (downward in the figure) is applied to the steering to maintain the steering neutral position. Then, in order to reduce the steering torque, lead pull correction is performed to apply assist force in the same direction as the steering torque, in other words, in the direction opposite to the vehicle deflection direction. In the figure, the vehicle deflection direction is indicated by a solid arrow, and the lead pull correction direction is indicated by a dashed-dotted arrow.

  Next, the lane change from the left lane 32 to the right lane 33 is started when the driver cuts the steering from the neutral position to the right side. Here, in general, a lane change refers to a driving operation that moves laterally by a lane width relatively slowly. That is, basically, the steering angle and the steering torque required for the lane change are extremely small, and the posture change in the turning direction (yaw direction) that occurs at the time of the lane change is also very small. Therefore, in the straight traveling determination, there is a high possibility that such a lane change is also included in the category of the straight traveling state. Accordingly, also in this example, the vehicle 30 moves from the left lane 32 to the right lane 33 while continuing the lead pull correction as described above.

  That is, the direction of the steering operation performed by the driver to start the lane change is the same as the direction of the steering operation for suppressing the deflection of the vehicle (both right in this example). While it is determined that the lead pull correction is not performed, the lead pull correction is not canceled.

  However, as shown in FIG. 9, in this example, the slope of the road surface is opposite in the left lane 32 before the lane change and the right lane 33 after the lane change. Therefore, when the vehicle 30 moves to the right lane 33 while the lead pull correction in the left lane 32 is continued, the direction of the lead pull correction is the same as the direction of deflection of the vehicle due to the inclination (right direction). It will end up.

  That is, in the lead pull correction described above, when a factor that induces vehicle deflection (in the above example, the slope of the road surface) is reversed, there is a possibility that an assist force is applied in a direction that promotes the deflection. . And this may be a factor that hinders the stability of the vehicle behavior. In this respect, there is still room for improvement.

  The present invention has been made to solve the above-described problems, and its object is to effectively suppress the deflection of the vehicle with a simple configuration and reverse the factor that induces the deflection. However, an object of the present invention is to provide an electric power steering device that can stably maintain the behavior of the vehicle.

  In order to solve the above-mentioned problems, the invention according to claim 1 includes a steering force assisting device provided to apply an assisting force for assisting a steering operation to a steering system, and a drive source of the steering force assisting device. Control means for controlling the operation of the steering force assisting device by supplying driving power to a certain motor, and whether the vehicle is in a straight traveling state based on the magnitude of the state quantity related to the turning motion of the vehicle Determining means for determining whether the vehicle is in a straight traveling state, the control means calculates a correction component for reducing a steering torque input to the steering and performs the steering operation. An electric power steering device for calculating a target assist force to be generated by the steering force assisting device by superimposing on a basic component calculated to assist, wherein A detection means for detecting a degree, the control unit, when the direction of the correction component to the direction of the lateral acceleration are the same, to initialize the correction component, and the gist.

  That is, when the factor that induces the deflection of the vehicle is “inclination of the traveling road surface”, the lateral acceleration in the same direction as the vehicle deflection direction is generated in the vehicle due to the influence of the gravity. Therefore, as in the above configuration, when the direction of the correction component and the direction of the lateral acceleration are the same direction, initialization of the correction component facilitates vehicle deflection based on the correction component. It is possible to prevent the direction assist force from being applied. As a result, while suppressing the deflection of the vehicle effectively with a simple configuration, even when the slope of the traveling road surface, which is a factor that induces the deflection of the vehicle, is reversed, for example, during a lane change, Can be stably maintained.

  According to a second aspect of the present invention, a driving force is supplied to a steering force assisting device provided to apply an assisting force for assisting a steering operation to a steering system, and a motor which is a drive source of the steering force assisting device. Control means for controlling the operation of the steering force assisting device, and determination means for determining whether or not the vehicle is in a straight traveling state based on the magnitude of the state quantity related to the turning motion of the vehicle. When it is determined that the vehicle is in a straight traveling state, the control means calculates a correction component that reduces the steering torque input to the steering and calculates a basic component that is calculated to assist the steering operation. An electric power steering device that calculates a target assist force to be generated by the steering force assisting device by superimposing the steering force assisting device, wherein the control means includes the direction of the steering torque and the correction In the case where the minute directions are different it is to initialize the correction component, and the gist.

  According to a third aspect of the present invention, a driving force is supplied to a steering force assisting device provided to apply an assisting force for assisting a steering operation to a steering system, and a motor that is a drive source of the steering force assisting device. Control means for controlling the operation of the steering force assisting device, and determination means for determining whether or not the vehicle is in a straight traveling state based on the magnitude of the state quantity related to the turning motion of the vehicle. When it is determined that the vehicle is in a straight traveling state, the control means calculates a correction component that reduces the steering torque input to the steering and calculates a basic component that is calculated to assist the steering operation. An electric power steering device that calculates a target assist force to be generated by the steering force assisting device by superimposing the detector, and includes a detecting unit that detects a steering angle of the steering. The control unit, when the direction of the steering angle and direction of the correction component are different is to initialize the correction component, and the gist.

  That is, even if the factor that induces the deflection of the vehicle is reversed, the correction component is initialized when the vehicle is in a non-straight running state by the driver's correction rudder. However, there is a time lag until it is determined that the vehicle is traveling straight in the straight traveling determination. And during this time lag, the assist force of the direction which promotes the deflection | deviation of a vehicle will be provided.

  In this regard, according to the above configuration, the correction component is initialized at the moment when the driver performs the correction rudder. As a result, even when the factor that induces the deflection of the vehicle is reversed, the behavior of the vehicle can be stably maintained. In addition, there is an advantage that it effectively functions even when a factor that induces the deflection, such as a crosswind, is other than “inclination of the traveling road surface”.

  According to the present invention, the electric power capable of stably maintaining the behavior of the vehicle even when the factor that induces the deflection is reversed while effectively suppressing the deflection of the vehicle with a simple configuration. A steering device can be provided.

The schematic block diagram of an electric power steering device (EPS). The control block diagram of EPS. Explanatory drawing which shows the aspect of a basic assist control calculation. The flowchart which shows the process sequence of lead pull correction amount calculation. The flowchart which shows the process sequence of lead pull correction control. The flowchart which shows the process sequence of the lead pull correction | amendment control of another example. Explanatory drawing which shows the inclination of a vehicle travel path. Explanatory drawing which shows an example of the lead pull correction amount computed in order to reduce steering torque. Explanatory drawing which shows the vehicle deflection | deviation direction and lead pull correction | amendment direction at the time of the lane change during cant road driving | running | working.

DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, an embodiment of the invention will be described with reference to the drawings.
FIG. 1 is a schematic configuration diagram of an electric power steering apparatus (EPS) 1 according to the present embodiment. As shown in the figure, the steering shaft 3 to which the steering wheel 2 is fixed is connected to a rack 5 via a rack and pinion mechanism 4, and the rotation of the steering shaft 3 accompanying the steering operation is performed by the rack and pinion mechanism 4. Is converted into a reciprocating linear motion of the rack 5. The steering angle of the steered wheels 6, that is, the steered angle is varied by the reciprocating linear motion of the rack 5, whereby the traveling direction of the vehicle is changed.

  The EPS 1 includes an EPS actuator 10 serving as a steering force assisting device that applies an assist force for assisting a steering operation to the steering system, and an ECU 11 serving as a control unit that controls the operation of the EPS actuator 10.

  The EPS actuator 10 of the present embodiment is a so-called rack assist type EPS actuator in which a motor 12 as a driving source thereof is arranged coaxially with the rack 5, and the motor torque generated by the motor 12 is a ball feed mechanism (not shown). ) Is transmitted to the rack 5. In addition, the motor 12 of this embodiment is a brushless motor, and rotates by receiving supply of three-phase (U, V, W) driving power from the ECU 11.

  On the other hand, a torque sensor 14, a vehicle speed sensor 15, and a steering angle sensor 16 are connected to the ECU 11, and the ECU 11 inputs the steering torque τ, the vehicle speed V, and the steering angle θs detected by these sensors. Is done. Further, the EPS 1 of the present embodiment is provided with a yaw rate sensor 17 and a lateral G sensor 18 as a detecting means, and the yaw rate γ and the lateral acceleration Fs of the vehicle are input to the ECU 11. Then, the ECU 11 of the present embodiment calculates a target assist force based on the vehicle state quantities detected by these sensors and causes the motor 12 that is a drive source to calculate the target assist force in the EPS actuator 10. By supplying driving power, the operation of the EPS actuator 10, 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.
FIG. 2 is a control block diagram of the EPS of this embodiment. As shown in the figure, the ECU 11 includes a microcomputer 21 that outputs a motor control signal, and a drive circuit 22 that supplies drive power to a motor 12 that is a drive source of the EPS actuator 10 based on the motor control signal. ing.

  In the present embodiment, the ECU 11 is connected to a current sensor 23 for detecting an actual current value I supplied to the motor 12 and a rotation angle sensor 24 for detecting the rotation angle θm of the motor 12. The microcomputer 21 outputs a motor control signal to the drive circuit 22 based on the actual current value I and the rotation angle θm of the motor 12 detected based on the output signals of these sensors, and the steering torque τ and the vehicle speed V. To do.

  The control blocks shown below are realized by a computer program executed by the microcomputer 21. Then, the microcomputer 21 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 every predetermined period.

  Specifically, the microcomputer 21 of the present embodiment is calculated by a current command value calculation unit 25 that calculates a current command value Iq * corresponding to a target assist force that should be generated by the EPS actuator 10, and a current command value calculation unit 25. And a motor control signal output unit 26 for outputting a motor control signal based on the current command value Iq *.

  The current command value calculation unit 25 includes a basic assist control unit 27 that calculates a basic assist control amount Ias * which is a basic component of the target assist force. The basic assist control unit 27 includes a steering torque τ and a vehicle speed V. Is entered. Based on the steering torque τ and the vehicle speed V, the basic assist control unit 27 calculates a larger basic assist control amount Ias * as the steering torque τ (the absolute value thereof) increases and as the vehicle speed V decreases. To do.

  In the present embodiment, as shown in FIG. 3, the region where the detected steering torque τ (absolute value) is equal to or smaller than a predetermined threshold (−τ0 <τ <τ0) is fundamental regardless of the steering torque τ. This is set as a so-called dead zone in which the value of the assist control amount Ias * is “zero”.

  Then, the current command value calculation unit 25 performs motor control using the control component based on the basic assist control amount Ias * calculated by the basic assist control unit 27 as the current command value Iq * that becomes the target assist force in the power assist control. The signal is output to the signal output unit 26.

  The motor control signal output unit 26 includes the current command value Iq * calculated by the current command value calculation unit 25, the actual current value I detected by the current sensor 23, and the motor 12 detected by the rotation angle sensor 24. The rotation angle θm is input. The motor control signal output unit 26 calculates a motor control signal by executing current feedback control so that the actual current value I follows the current command value Iq * corresponding to the target assist force.

  Specifically, in the present embodiment, the motor control signal output unit 26 converts the phase current value (Iu, Iv, Iw) of the motor 12 detected as the actual current value I into the d, q axes of the d / q coordinate system. The current feedback control is performed by converting into a current value (d / q conversion).

  That is, the current command value Iq * is input to the motor control signal output unit 26 as a q-axis current command value. The motor control signal output unit 26 performs d / q conversion on the phase current value (Iu, Iv, Iw) based on the rotation angle θm detected by the rotation angle sensor 24, and the d, q-axis current value and q Based on the shaft 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.

  In the ECU 11 of this embodiment, the microcomputer 21 outputs the motor control signal generated as described above to the drive circuit 22, and the drive circuit 22 supplies the three-phase drive power based on the motor control signal to the motor 12. By supplying, the operation of the EPS actuator 10 is controlled.

(Lead pull correction control)
Next, the aspect of the lead pull correction control in this embodiment will be described.
As described above, when the input of the steering torque for canceling the factor that induces the deflection of the vehicle, such as traveling on a cant road (for example, the inclination of the road surface), is continued for a long time as fatigue. It will be accumulated in the driver.

  Therefore, in the present embodiment, the current command value calculation unit 25 of the microcomputer 21 has the lead pull correction amount Ilp * as a correction component for reducing the steering torque τ detected when the vehicle is determined to be in the straight traveling state. There is provided a lead pull correction control unit 28 for calculating. Then, the current command value calculation unit 25 superimposes the lead pull correction amount Ilp * calculated by the lead pull correction control unit 28 on the basic assist control amount Ias * as the basic component calculated by the basic assist control unit 27 in the adder 29. Thus, the current command value Iq * as the target assist force in the power assist control is calculated.

  In this embodiment, the assist force generated based on the lead pull correction amount Ilp * suppresses the deflection by negating the influence (gravity) caused by the inclination of the traveling road surface, which is a factor that induces the deflection of the vehicle. It is designed to reduce the burden on the driver.

  More specifically, when the lead pull correction control unit 28 of this embodiment determines that the lead pull correction should be executed, the lead pull correction control unit 28 determines the direction (sign) of the detected steering torque τ, and the determined direction. The lead pull correction amount Ilp * is gradually increased in the same direction, that is, the direction in which the detected steering torque τ is reduced (see FIG. 8). In the present embodiment, the left direction is defined as “+” and the right direction is defined as “−” in the traveling direction of the vehicle. Then, the steering torque τ is gradually reduced and finally set to “0”, so that the lead pull correction is executed without causing the driver to feel uncomfortable.

  Specifically, as shown in the flowchart of FIG. 4, the lead pull correction control unit 28 first determines whether or not the sign of the detected steering torque τ is “+” (step 101). When the sign of the steering torque τ is “+” (τ> 0, step 101: YES), the predetermined value α is added to the previous value of the lead pull correction amount Ilp * to obtain “+”. A new lead pull correction amount Ilp * that gradually increases in the direction is calculated (Ilp * (current value) = Ilp * (previous value) + α, step 102).

  On the other hand, when it is determined in step 101 that the sign of the detected steering torque τ is not “+” (τ ≦ 0, step 101: NO), the sign of the steering torque τ is subsequently “−”. It is determined whether or not there is (step 103). When the sign of the steering torque τ is “−” (τ <0, step 103: YES), the predetermined value α is subtracted from the previous value of the lead pull correction amount Ilp * to obtain “−”. A new lead pull correction amount Ilp * that gradually increases in the direction is calculated (Ilp * (current value) = Ilp * (previous value) −α, step 104).

  When it is determined in step 103 that the sign of the steering torque τ is not “−”, that is, the value of the steering torque τ is “0” (τ = 0, step 103: NO), the lead pull correction is performed. By setting the previous value of the amount Ilp * as a new lead pull correction amount Ilp *, the value is held (Ilp * (current value) = Ilp * (previous value), step 105).

  The read pull correction control unit 28 of the present embodiment is configured to output the new read pull correction amount Ilp * calculated in any one of the above steps 102, 104, and 105 to the adder 29.

  By executing the lead pull correction control in this way, it is possible to effectively suppress the deflection of the vehicle with a simple configuration and without causing the driver to feel uncomfortable. However, as described above, in this lead pull correction control, when the inclination of the traveling road surface that is a factor that induces the deflection of the vehicle is reversed, an assist force may be applied in a direction that promotes the deflection. There is a possibility that this may become a factor that hinders the stability of the vehicle behavior.

  In view of this point, in this embodiment, the lead pull correction control unit 28 detects the direction of the lead pull correction amount Ilp * and the lateral G sensor 18 prior to the calculation of the lead pull correction amount Ilp * as described above. It is determined whether or not the direction of the lateral acceleration Fs differs. If it is determined that the two directions are not different, that is, they are the same, the lead-pull correction amount Ilp * is not executed without executing the gradual increase calculation (see FIG. 4) of the lead-pull correction amount Ilp * as described above. Is initialized, specifically, the value is cleared to “0”.

  That is, as described above, when the factor that induces the deflection of the vehicle is “inclination of the traveling road surface”, the vehicle has a lateral acceleration Fs in the same direction as the vehicle deflection direction due to the influence of the gravity. Therefore, as described above, when the direction of the lead pull correction amount Ilp * is the same as the direction of the lateral acceleration Fs, the value of the lead pull correction amount Ilp * is set to “0”. By the lead pull correction control, it is possible to prevent an assist force in a direction that promotes the deflection of the vehicle from being applied. And in this embodiment, by this, even if it is a case where the inclination of the driving | running | working road surface reverses, for example at the time of a lane change etc. (refer FIG. 9), It has become.

Next, the processing procedure of the lead pull correction control in this embodiment will be described.
As shown in the flowchart of FIG. 5, the lead pull correction control unit 28 first determines whether or not the vehicle is in a straight traveling state based on the magnitude of the state quantity related to the turning motion of the vehicle. Specifically, the lead-pull correction control unit 28 as a determination unit has a detected vehicle yaw rate γ (absolute value thereof) equal to or smaller than a predetermined threshold γ (| γ | ≦ γ0, step 201: YES), and When the detected lateral acceleration Fs (absolute value) of the vehicle is equal to or smaller than a predetermined threshold value F0 (| Fs | ≦ F0, Step 202: YES), it is determined that the vehicle is in a straight traveling state. When either the yaw rate γ or the lateral acceleration Fs exceeds the corresponding threshold value γ0, F0 (| γ |> γ0, step 201: NO, or | Fs |> F0, step 202: NO). It is determined that the vehicle is not in a straight traveling state, that is, in a non-linear state.

  Next, in the vehicle straight-ahead determination, when it is determined that the vehicle is in a straight-ahead state (step 202: YES), the lead pull correction control unit 28 subsequently determines whether or not the detected vehicle speed V exceeds a predetermined speed V0. (Step 203). When the vehicle speed V exceeds the predetermined speed V0 (V> V0, step 203: YES), it is further determined whether or not the direction of the lead pull correction amount Ilp * is different from the direction of the lateral acceleration Fs. (Step 204).

  If the two directions are different (Ilp *, Fs direction difference, step 204: YES), the lead pull correction amount Ilp * that gradually increases in the same direction as the steering torque τ is calculated as described above (step 205). If both directions are the same (Ilp *, Fs direction is the same, step 204: NO), the value of the lead pull correction amount Ilp * is cleared (Ilp * = 0, step 206).

  If it is determined in the above vehicle straight-ahead determination that the vehicle is not in a straight-ahead state (step 201: NO or step 202: NO), the value of the lead pull correction amount Ilp * is cleared by executing step 206. In this embodiment, when it is determined in step 203 that the vehicle speed V is equal to or lower than the predetermined speed V0 (V ≦ V0, step 203: YES), the vehicle is in a constant speed running state that does not require lead pull correction. And the value of the lead pull correction amount Ilp * is cleared by executing step 206.

  The lead pull correction control unit 28 is configured to output to the adder 29 a new read pull correction amount Ilp * that is calculated in step 205 as described above or whose value is cleared in the step.

As described above, according to the present embodiment, the following operations and effects can be obtained.
(1) The current command value calculation unit 25 includes a lead pull correction control unit 28 that performs lead pull correction control to reduce the steering torque τ detected when the vehicle is determined to be in a straight traveling state. When it is determined that the lead pull correction should be executed, the control unit 28 calculates the lead pull correction amount Ilp * in the same direction as the detected steering torque τ. Then, the current command value calculation unit 25 calculates the current command value Iq * by superimposing the lead pull correction amount Ilp * on the basic assist control amount Ias * as a basic component. Further, the lead pull correction control unit 28 determines whether or not the direction of the lead pull correction amount Ilp * is different from the direction of the lateral acceleration Fs. If both directions are the same, the value of the lead pull correction amount Ilp * is cleared (Ilp * = 0).

  That is, when the factor that induces the deflection of the vehicle is “inclination of the traveling road surface”, the vehicle has a lateral acceleration Fs in the same direction as the vehicle deflection direction due to the influence of gravity. Accordingly, when the direction of the lead pull correction amount Ilp * and the direction of the lateral acceleration Fs are the same as in the above configuration, the value of the lead pull correction amount Ilp * is set to “0”. Further, it is possible to prevent the assist force in the direction of promoting the deflection of the vehicle from being applied by the lead pull correction control. As a result, while suppressing the deflection of the vehicle effectively with a simple configuration, even when the slope of the traveling road surface, which is a factor that induces the deflection of the vehicle, is reversed, for example, during a lane change, Can be stably maintained.

  (2) When the lead pull correction control unit 28 determines that the lead pull correction should be executed, the lead pull correction control unit 28 gradually increases the lead pull correction amount Ilp *. As a result, the lead pull correction can be executed without giving a sense of discomfort to the steering feeling.

  (3) The basic assist control unit 27 calculates a basic assist control amount Ias * based on the steering torque τ. In a region where the steering torque τ (absolute value) is equal to or smaller than a predetermined threshold (−τ0 <τ <τ0), the so-called dead zone where the value of the basic assist control amount Ias * is “zero” regardless of the steering torque τ. Set as

  In other words, the presence of the dead zone forces the driver to continue the minute steering operation without receiving the benefits of the power assist. Therefore, by applying the invention of the above (1) to such a thing, a more remarkable effect can be obtained.

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

  In the above embodiment, it is determined whether or not the direction of the lead pull correction amount Ilp * is different from the direction of the lateral acceleration Fs (step 204). If both directions are the same (Ilp * and Fs directions are the same) , Step 204: NO), the value of the lead pull correction amount Ilp * is cleared (Ilp * = 0, Step 206). However, the present invention is not limited to this, and as shown in the flowchart of FIG. 6, it is determined whether the direction of the lead pull correction amount Ilp * is the same as the direction of the steering torque τ (step 304). If they are different (Ilp *, τ direction difference, step 304: NO), the read pull correction amount Ilp * may be cleared (Ilp * = 0, step 206).

  That is, even if the factor that induces the deflection of the vehicle is reversed, the lead pull correction is canceled when the vehicle is brought into a non-straight running state by the driver's correction rudder. However, there is a time lag until it is determined that the vehicle is traveling straight in the straight traveling determination. Therefore, during this time lag, an assist force in a direction that promotes the deflection of the vehicle is applied.

  In this regard, according to the above-described configuration, the value of the lead pull correction amount Ilp * is cleared, that is, the lead pull correction is canceled at the moment when the driver performs the correction rudder. As a result, even when the factor that induces the deflection of the vehicle is reversed, the behavior of the vehicle can be stably maintained. In addition, this configuration has an advantage that it functions effectively even when a factor that induces the deflection of the vehicle, such as a crosswind, is other than “inclination of the road surface”.

  In this case, the steering angle of the steering 2, that is, the steering angle θs may be used instead of the steering torque τ. In FIG. 6, the processes in steps 301 to 303 and steps 305 to 307 are the same as the processes in steps 201 to 203 and steps 205 to 207 in FIG. 5. Is omitted.

  In the above embodiment, the yaw rate γ and the lateral acceleration Fs are used for the straight traveling determination. However, the configuration is not limited to this, and the determination may be made using only one of them. In addition, as the state quantity related to the turning motion of the vehicle used for the vehicle straight traveling determination, for example, other state quantities such as the left and right wheel speed difference may be used, and the yaw rate γ and the lateral acceleration Fs are included. It is good also as a structure determined by arbitrary combinations.

  In the above embodiment, the lead pull correction amount Ilp * is gradually increased. However, the present invention is not limited to this, and there is no particular limitation on the method of calculating the absolute value, for example, calculating a constant value as the lead pull correction amount Ilp * or changing it stepwise.

  In the above embodiment, when it is determined that the vehicle speed V is equal to or less than the predetermined speed V0, it is determined that the vehicle is in a constant speed running state that does not require lead pull correction, and the value of the lead pull correction amount Ilp * is cleared. (See FIG. 5, step 204). However, the condition determination regarding the vehicle speed V is not necessarily performed.

  In the above embodiment, the initialization of the lead pull correction amount Ilp * is performed by clearing the value to “0”. However, the value of the read pull correction amount Ilp * after the initialization is not necessarily It may not be “0”. Specifically, for example, when there is an unbalance of the axle and the vehicle weight as a factor that induces the deflection of the vehicle, a value for canceling this may be set as the initial value of the lead pull correction amount Ilp *.

Next, technical ideas that can be grasped from the above embodiments will be described together with the effects thereof.
(Appendix 1) In the electric power steering apparatus according to any one of claims 1 to 3, the control means calculates a correction component that gradually increases until the steering torque becomes zero. Electric power steering device. Thereby, the deflection of the vehicle can be suppressed without giving a sense of incongruity of the steering feeling.

  (Appendix 2) In the electric power steering apparatus according to any one of claims 1 to 3, the basic component is calculated based on the steering torque, and a dead zone is present in a small region of the steering torque. An electric power steering apparatus characterized by being set. In other words, the presence of the dead zone forces the driver to continue the minute steering operation without receiving the benefits of the power assist. Therefore, by applying the invention of any one of claims 1 to 3 to such a thing, a more remarkable effect can be obtained.

  DESCRIPTION OF SYMBOLS 1 ... Electric power steering device (EPS), 2 ... Steering, 6 ... Steering wheel, 10 ... EPS actuator, 11 ... ECU, 12 ... Motor, 14 ... Torque sensor, 15 ... Vehicle speed sensor, 16 ... Steering angle sensor, 17 ... Yaw rate sensor, 18 ... lateral G sensor, 21 ... microcomputer, 22 ... drive circuit, 25 ... current command value calculation unit, 27 ... basic assist control unit, 28 ... lead pull correction control unit, 29 ... adder, 30 ... vehicle, Iq *: Current command value, Ias *: basic assist control amount, Ilp *: lead pull correction amount, γ: yaw rate, Fs: lateral acceleration, γ0, F0: threshold, τ: steering torque, θs: steering angle.

Claims (3)

A steering force assisting device provided to apply an assisting force for assisting a steering operation to the steering system, and by supplying driving power to a motor that is a drive source of the steering force assisting device, Control means for controlling the operation, and determination means for determining whether or not the vehicle is in a straight traveling state based on the magnitude of the state quantity related to the turning motion of the vehicle, the control means comprising: When it is determined that the vehicle is in the straight traveling state, the steering force assist is calculated by superimposing the correction component for reducing the steering torque input to the steering and superimposing on the basic component calculated to assist the steering operation. An electric power steering device for calculating a target assist force to be generated in the device,
Detecting means for detecting a lateral acceleration of the vehicle;
The electric power steering apparatus, wherein the control means initializes the correction component when the direction of the lateral acceleration and the direction of the correction component are the same. A steering force assisting device provided to apply an assisting force for assisting a steering operation to the steering system, and by supplying driving power to a motor that is a drive source of the steering force assisting device, Control means for controlling the operation, and determination means for determining whether or not the vehicle is in a straight traveling state based on the magnitude of the state quantity related to the turning motion of the vehicle, the control means comprising: When it is determined that the vehicle is in a straight traveling state, the steering force assist is calculated by superimposing the correction component for reducing the steering torque input to the steering and superimposing on the basic component calculated to assist the steering operation. An electric power steering device for calculating a target assist force to be generated in the device,
The control means initializes the correction component when the direction of the steering torque is different from the direction of the correction component. A steering force assisting device provided to apply an assisting force for assisting a steering operation to the steering system, and by supplying driving power to a motor that is a drive source of the steering force assisting device, Control means for controlling the operation, and determination means for determining whether or not the vehicle is in a straight traveling state based on the magnitude of the state quantity related to the turning motion of the vehicle, the control means comprising: When it is determined that the vehicle is in a straight traveling state, the steering force assist is calculated by superimposing the correction component for reducing the steering torque input to the steering and superimposing on the basic component calculated to assist the steering operation. An electric power steering device for calculating a target assist force to be generated in the device,
Detecting means for detecting a steering angle of the steering,
The control means initializes the correction component when the direction of the steering angle is different from the direction of the correction component.

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