JP5556219B2 - Electric power steering device - Google Patents

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. Normally, in such EPS, the torque generated is controlled by executing current control. Specifically, a current command value is calculated as a control target value of the assist force applied to the control system, and then a voltage command value corresponding to the deviation is calculated so that the actual current value follows the current command value. The Then, a motor control signal for operating the drive circuit to apply the voltage indicated by the voltage command value to the motor is generated. The motor applied voltage is generally adjusted by adjusting the duty ratio in PWM (pulse width modulation) control.

  By the way, in the steering device, the movable range of the steered wheels is determined, and the steering cannot be steered so that the steered wheels exceed the limit position of the movable range. For example, in a configuration employing a rack and pinion type steering mechanism, the end of the rack shaft comes into contact with the rack housing so that the movement of the rack shaft is mechanically constrained so that the movable range of the steered wheels can be increased. Is stipulated.

  For this reason, in the state where the steering is steered to the vicinity of the maximum steering angle (steering end) where the steering operation is allowed, that is, in the state where the steered wheels are steered to the vicinity of the movable limit, cutting is performed at a high steering angular velocity. When steering is performed, the rack shaft collides with the rack housing and an impact is applied to the steering system. Then, due to the impact caused by the so-called end contact, a reaction force in the direction opposite to the steering direction acts on the steering, thereby causing a problem that the steering feeling is deteriorated or a hitting sound is generated.

  Therefore, Patent Document 1 discloses an EPS in which the current command value is reduced based on the steering angle and the steering angular velocity of the steering, and the assist force is reduced to reduce the impact of the end contact. Specifically, for example, when the steering angle is near the steering end and the steering angular velocity is high, the current command value (assist force) is greatly reduced so that the driver cannot operate the steering at a high steering angular velocity. The impact of the end pad is mitigated. On the other hand, even when the steered wheels are in the vicinity of the steering end, when the steering angular velocity is low, the reduction amount of the current command value is reduced so that the influence on the assist force is reduced.

JP 2008-18865 A

  By the way, in recent years, in EPS, it is desired to realize a better steering feeling. However, since the assist force is reduced in the configuration of Patent Document 1 described above, depending on the load when steering the steering (turning the steered wheels), the impact of the end pad cannot be sufficiently reduced or sufficient. In some cases, the assist force could not be applied.

  Specifically, for example, when the vehicle is traveling on a low μ road and the load when steering the steering wheel is low, even if the current command value is reduced, the assist force corresponding to the current command value is used. Fast steering may be possible. In such a case, the steering angular velocity cannot be sufficiently suppressed, and the impact of the end contact cannot be sufficiently mitigated. On the other hand, if the current command value is reduced so that the impact of the end bumps can be sufficiently mitigated when the steering load is low, when steering the steering wheel when the vehicle is traveling on a high μ road, etc. There is a possibility that the assist force is insufficient in a situation where the load is high. As described above, in the above-described conventional configuration, the impact of the end pad is sufficiently mitigated in a state where the load when steering the steering is low, and sufficient assist force is applied in a situation where the load when steering the steering is high. This was difficult and there was still room for improvement in this regard.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide an electric power steering device capable of sufficiently mitigating the impact of the end pad and giving a sufficient assist force. There is to do.

In order to achieve the above object, the invention according to claim 1 is directed to a steering force assisting device that applies an assisting force for assisting a steering operation to a steering system using a motor as a driving source, and supply of driving power to the motor. Control means for controlling the operation of the steering force assisting device, steering angle detection means for detecting a steering angle generated in the steering, and steering angular velocity detection means for detecting the steering angular velocity of the steering , the control means The voltage command value is calculated by executing a current command value calculation unit that calculates a current command value based on the steering torque and the vehicle speed, and current feedback control that causes the current command value to follow the actual current value. A motor control signal generator for generating a motor control signal to apply a voltage indicated by a command value to the motor, and the motor control signal based on the motor control signal Comprising a driving circuit for supplying driving power to chromatography data, and a limit angular velocity calculating means for calculating a limit angular velocity of the upper limit of the steering angular velocity allowed according to the steering angle, the limiting angular velocity calculating means, the when the steering angle is equal to or greater than the predetermined steering angle of the maximum steering angle vicinity, which the limiting velocity is computed to be less on the basis of the increase in the steering angle, the motor control signal generating unit, the steering The gist is provided with an angular velocity limiting means for correcting the voltage command value so as to suppress the rotational angular velocity of the motor when the angular velocity is larger than the limiting angular velocity.

  According to the above configuration, when the steering angular velocity of the steering is larger than the limit angular velocity, the voltage command value is corrected and the rotational angular velocity of the motor is suppressed, so that the steering angular velocity of the steering can be suppressed. The limiting angular velocity is calculated so as to decrease based on the increase in the steering angle when the steering angle is equal to or greater than the predetermined steering angle in the vicinity of the steering end. Therefore, the steering angular velocity is sufficiently suppressed in the vicinity of the steering end. The impact of the end pad can be sufficiently mitigated. Note that the rotational angular velocity of the motor is suppressed by correcting the decrease in the absolute value of the voltage command value and reducing the applied voltage. Further, the rotational angular velocity of the motor is suppressed by applying the voltage for reversely rotating the motor by reversing the sign of the voltage command value.

  As described above, in the above configuration, since the steering angular velocity is controlled by controlling the rotational angular velocity of the motor, the load at the time of steering the steering is different from the case where the current command value calculated as the control target value of the assist force is reduced and corrected. Even when is small, the steering angular velocity can be suppressed and the impact of the end contact can be sufficiently mitigated. Further, since the current command value (assist force) is not reduced, a sufficient assist force can be applied to the steering system even when the load during steering is large. Therefore, it is possible to sufficiently reduce the impact of the end pad when the load when steering the steering is low, and to give a sufficient assist force when the load when steering the steering is high. Feeling can be realized.

  According to a second aspect of the present invention, in the electric power steering apparatus according to the first aspect, the angular velocity limiting means is configured such that when the steering state of the steering is a cut-in state that increases the absolute value of the steering angle, The gist is to correct the voltage command value.

  The impact due to the end contact becomes a problem when the steering state of the steering is a cut state in which the absolute value of the steering angle is increased. That is, even when the steering angle is in the vicinity of the steering end and the steering is steered at a high steering angular speed, for example, when the back-up steering is performed to reduce the absolute value of the steering angle, the end contact does not occur. Furthermore, if the voltage command value is corrected at the time of turning back the steering, the steering angular velocity is suppressed, which may cause a deterioration in steering feeling.

  In this regard, according to the above-described configuration, the voltage command value is corrected when the steering state of the steering is in the cut-in state, so that the steering angular velocity is suppressed and the steering feeling is deteriorated only when end contact is a problem. Can be prevented.

  According to a third aspect of the present invention, in the electric power steering apparatus according to the first or second aspect, the angular velocity limiting means superimposes a compensation voltage value having a sign opposite to the sign of the voltage command value on the voltage command value. Thus, the gist is to correct the voltage command value.

  According to the above configuration, in order to correct the voltage command value by superimposing the compensation voltage value of the sign of the voltage command value and the opposite sign so as to reduce the rotational angular velocity of the motor, for example, a predetermined compensation amount (gain) Unlike the case where the voltage command value is corrected by multiplying the voltage command value, the correction amount does not change depending on the magnitude of the voltage command value, so that an appropriate compensation voltage value (correction amount) can be easily calculated.

  The invention according to claim 4 is the electric power steering apparatus according to claim 3, wherein the angular velocity limiting means calculates the compensation voltage value based on a difference between the steering angular velocity and the limiting angular velocity. And

  According to the above configuration, since the compensation voltage value is calculated based on the difference between the steering angular velocity and the limit angular velocity, an appropriate compensation voltage value is calculated according to the magnitude of the steering angular velocity, and the impact of the end contact is preferably applied. Can be relaxed.

  According to a fifth aspect of the present invention, in the electric power steering device according to any one of the first to fourth aspects, the angular velocity limiting means is a minimum absolute value of a corrected voltage command value obtained by correcting the voltage command value. The gist is to make the value zero.

  According to the above configuration, since the minimum value of the absolute value of the corrected voltage command value corrected by the angular velocity limiting means is zero, the sign is not reversed even if the voltage command value is corrected, and the motor is rotated in the reverse direction. No voltage is applied. For this reason, even if the voltage command value is corrected by the angular velocity limiting means, the assist force from the steering force assisting device is not applied, and the driver does not apply the reaction force (force in the direction opposite to the steering direction) from the steering force assisting device. ), And an excellent steering feeling can be obtained.

  According to a sixth aspect of the present invention, in the electric power steering apparatus according to any one of the first to fifth aspects, the angular velocity limiting means includes a map showing a relationship between the steering angle and the limiting angular velocity. The gist is to calculate the limit angular velocity based on the map.

  According to the above configuration, since the angular velocity limiting means calculates the limiting angular velocity based on the map, it can easily calculate the limiting angular velocity.

  According to the present invention, it is possible to provide an electric power steering apparatus capable of sufficiently mitigating the impact of an end pad and applying a sufficient assist force.

The schematic block diagram of an electric power steering device (EPS). The control block diagram which shows the electric constitution of EPS. The graph which shows the relationship between a steering angle and a limit angular velocity. The flowchart which shows the process sequence of correction | amendment q-axis voltage command value calculation by a steering angular velocity restriction | limiting part.

DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, an embodiment of the invention will be described with reference to the drawings.
As shown in FIG. 1, in an electric power steering apparatus (EPS) 1, 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. Thereby, the rotation of the steering shaft 3 accompanying the steering operation is converted into a reciprocating linear motion of the rack shaft 5 by the rack and pinion mechanism 4. Note that the steering shaft 3 of the present embodiment is formed by connecting a column shaft 8, an intermediate shaft 9, and a pinion shaft 10. Then, 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, so that the steering angle of the steered wheels 12 is increased. 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 is configured as a so-called column type EPS actuator. Specifically, the motor 21 that is the drive source of the EPS actuator 22 is drivingly connected to the column shaft 8 via the speed reduction mechanism 24. The speed reduction mechanism 24 is configured by meshing a wheel gear 25 connected to the column shaft 8 and a worm gear 26 connected to the motor 21. The motor 21 is a brushless motor, and rotates by receiving supply of three-phase (U, V, W) driving power from the ECU 23. And ECU23 controls the assist force given to a steering system by controlling the assist torque which this motor 21 generate | occur | produces (power assist control).

  On the other hand, a vehicle speed sensor 31, a torque sensor 32, and a steering sensor (steering angle sensor) 33 as a steering angle detection unit are connected to the ECU 23. Then, the ECU 23 executes the operation of the EPS actuator 22, that is, power assist control, based on the vehicle speed SPD, the steering torque τ, and the steering angle θs detected by these sensors.

Next, the electrical configuration of the EPS of this embodiment will be described.
As shown in FIG. 2, the ECU 23 includes a microcomputer 41 as a motor control signal output unit that outputs a motor control signal, and a drive circuit 42 that supplies three-phase drive power to the motor 21 based on the motor control signal. ing.

  The drive circuit 42 is a known PWM inverter in which three arms corresponding to each phase are connected in parallel with a pair of switching elements (FET) connected in series as a basic unit (arm). The motor control signal that is output defines the on-duty ratio of each switching element that constitutes the drive circuit 42. Then, a motor control signal is applied to the gate terminal of each switching element, and each switching element is turned on / off in response to the motor control signal, so that the voltage of the in-vehicle power supply (not shown) becomes three-phase driving power. It is converted and supplied to the motor 21.

  The ECU 23 includes current sensors 43u, 43v, 43w for detecting the phase current values Iu, Iv, Iw energized to the motor 21 and a rotation angle sensor 45 for detecting the motor rotation angle θm of the motor 21. It is connected. The microcomputer 41 is based on the phase current values Iu, Iv, Iw and the motor rotation angle θm of the motor 21 detected based on the output signals of these sensors, and the steering torque τ, the vehicle speed SPD and the steering angle θs. A motor control signal is output to the drive circuit 42.

  More specifically, the microcomputer 41 generates a current command value calculation unit 46 for calculating a current command value as a control target value for assist force applied to the steering system, and a motor control signal for controlling the operation of the drive circuit 42. And a motor control signal generation unit 47 that performs the operation.

  The current command value calculation unit 46 calculates the q-axis current command value Iq * in the d / q coordinate system based on the steering torque τ and the vehicle speed SPD detected by the torque sensor 32 and the vehicle speed sensor 31. Further, the motor control signal generation unit 47 includes the q-axis current command value Iq * output from the current command value calculation unit 46 and the phase current values Iu, Iv, Iw detected by the current sensors 43u, 43v, 43w. , And the motor rotation angle θm detected by the rotation angle sensor 45 is input. In the present embodiment, “Id * = 0” is calculated in the motor control signal generation unit 47 for the d-axis current command value Id *. The motor control signal generation unit 47 performs motor feedback control by executing current feedback control in the d / q coordinate system based on the phase current values Iu, Iv, Iw and the motor rotation angle θm (electrical angle). Generate a signal.

  More specifically, in the motor control signal generation unit 47, the phase current values Iu, Iv, and Iw are input to the three-phase / two-phase conversion unit 51 together with the motor rotation angle θm. Then, the phase current values Iu, Iv, Iw are converted into the d-axis current value Id and the q-axis current value Iq in the d / q coordinate system by the three-phase / two-phase converter 51.

  The q-axis current command value Iq * input to the motor control signal generator 47 is input to the subtractor 52q together with the q-axis current value Iq. On the other hand, the d-axis current command value Id * is input to the subtractor 52d together with the d-axis current value Id. The subtracters 52d and 52q calculate the d-axis current deviation ΔId and the q-axis current deviation ΔIq, respectively. The d-axis current deviation ΔId and q-axis current deviation ΔIq calculated in this way are input to the corresponding F / B controllers 53d and 53q, respectively.

  In each of the F / B control units 53d and 53q, the d-axis current command value Id * and the q-axis current command value Iq * that are the control target values are added to the d-axis current value Id and the q-axis current value that are actual currents. Feedback control for following Iq is performed. Specifically, the F / B control units 53d and 53q multiply the input d-axis current deviation ΔId and q-axis current deviation ΔIq by a predetermined F / B gain (PI gain) to obtain a d-axis voltage command value. Vd * and q-axis voltage command value Vq * are calculated.

  In the present embodiment, the q-axis voltage command value Vq * is input to a steering angular velocity limiting unit 61 described later, and the corrected q-axis voltage command value Vq ** is calculated in the steering angular velocity limiting unit 61. The q-axis voltage command value Vq * corresponds to the voltage command value, and the corrected q-axis voltage command value Vq ** corresponds to the corrected voltage command value. The corrected q-axis voltage command value Vq ** is input to the 2-phase / 3-phase converter 55 together with the d-axis voltage command value Vd * and the motor rotation angle θm. Phase voltage command values Vu *, Vv *, and Vw *.

  Subsequently, the phase voltage command values Vu *, Vv *, and Vw * calculated in the 2-phase / 3-phase converter 55 are input to the PWM converter 56. In the PWM converter 56, duty command values corresponding to the phase voltage command values Vu *, Vv *, Vw * are generated, and a motor control signal having an on-duty ratio indicated by each duty command value is generated. Generated. Then, the microcomputer 41 outputs the motor control signal generated in this way to each switching element (the gate terminal thereof) constituting the drive circuit 42, whereby the operation of the drive circuit 42, that is, to the motor 21 is output. Controls the supply of drive power.

(Steering angular velocity suppression processing)
Next, the steering angular velocity suppression process by the steering angular velocity limiting unit of the present embodiment will be described in detail.

  As described above, in a state where the steering 2 is steered to the vicinity of the maximum steering angle (steering end), that is, in a state where the steered wheels 12 are steered to the vicinity of the movable limit, the steering angle θs has a fast steering angular velocity. When incision steering for increasing the absolute value is performed, the rack shaft 5 collides with a rack housing (not shown), and an impact is applied to the steering system. Therefore, it is conceivable to correct the current command value based on the steering angle generated in the steering 2 and the steering angular velocity in order to reduce the impact caused by the so-called end contact. However, with this configuration, depending on the load when steering the steering wheel 2 (turning the steered wheels 12), there is a possibility that the impact of the end pad cannot be sufficiently reduced or sufficient assist force cannot be applied.

  Therefore, the steering angular velocity limiting unit 61 provided in the microcomputer 41 of the present embodiment is configured such that the steering angular velocity ωs of the steering 2 is the upper limit of the steering angular velocity ωs allowed according to the steering angle θs (impact caused by end contact at the steering angle θs). The q-axis voltage command value Vq * is corrected to suppress the motor rotation angular velocity ωm when it is larger than the limit angular velocity ωlim as the maximum steering angular velocity ωs) that can sufficiently relax the motor.

  More specifically, in addition to the q-axis voltage command value Vq *, the steering angle θs detected by the steering sensor 33 and the steering angular velocity ωs of the steering 2 are input to the steering angular velocity limiter 61. In the present embodiment, the microcomputer 41 includes a rotation angular velocity conversion unit 62 that converts the differential value (motor rotation angular velocity ωm) of the motor rotation angle θm detected by the rotation angle sensor 45 into the steering angular velocity ωs of the steering 2. Yes. The steering angular velocity ωs converted by the rotational angular velocity converting unit 62 is input to the steering angular velocity limiting unit 61. That is, in the present embodiment, the rotation angle sensor 45 and the rotation angular velocity conversion unit 62 constitute a steering angular velocity detection means.

  Then, the steering angular velocity limiting unit 61 calculates the limiting angular velocity ωlim based on the steering angle θs, and when the steering angular velocity ωs is larger than the limiting angular velocity ωlim and the steering state of the steering 2 is in the cut state, q The shaft voltage command value Vq * is corrected. When the steering angular velocity ωs is equal to or lower than the limit angular velocity ωlim, and when the steering state is not the cut-in state, the value of the corrected q-axis voltage command value Vq ** is set as the q-axis voltage command value Vq *. The shaft voltage command value Vq * is not corrected. Therefore, in the present embodiment, the steering angular velocity limiting unit 61 functions as a limiting angular velocity calculating unit and an angular velocity limiting unit.

  Specifically, the steering angular velocity limiting unit 61 includes a limiting angular velocity map 63 indicating the relationship between the absolute value of the steering angle θs and the limiting angular velocity ωlim, and calculates the limiting angular velocity ωlim based on the map 63. As shown in FIG. 3, the limit angular velocity map 63 shows that the steering angle θs is greater than or equal to a predetermined steering angle θsth in the vicinity of the steering end so that the impact due to end contact is sufficiently mitigated if the steering angular velocity ωs is the limiting angular velocity ωlim. In some cases, the limit angular velocity ωlim is set to decrease in proportion to the increase in the steering angle θs.

  In the present embodiment, the predetermined steering angle θsth is, for example, from the predetermined steering angle θsth to the steering end when the steering wheel 2 is steered at the maximum steering angular velocity ωs that a general driver can steer. In the meantime, the steering angular velocity ωs is set to a value that can be suppressed to an angular velocity at which the impact due to end contact is sufficiently mitigated. Further, when the steering angle θs is less than the predetermined steering angle θsth, the limiting angular velocity ωlim is set to the maximum steering angular velocity ωs that can be steered by a general driver in order to prevent the steering angular velocity ωs from being limited. Is set.

  Further, the steering angular velocity limiting unit 61 superimposes a compensation voltage value α having a sign opposite to that of the q-axis voltage command value Vq * on the q-axis voltage command value Vq * so that the motor rotation angular velocity ωm is decelerated. The q-axis voltage command value Vq * is corrected. The sign of the q-axis voltage command value Vq * indicates the direction in which the motor 21 is rotated by the voltage indicated by the q-axis voltage command value Vq *. More specifically, the steering angular velocity limiting unit 61 calculates a compensation voltage value α (= K × (| ωp | −) by multiplying a value obtained by subtracting the limiting angular velocity ωlim from the absolute value of the steering angular velocity ωs by a predetermined coefficient K. ωlim)). Then, according to the sign of the q-axis voltage command value Vq *, the compensation voltage value α is added to or subtracted from the q-axis voltage command value Vq * so that the absolute value thereof decreases.

  Furthermore, the steering angular velocity limiting unit 61 of the present embodiment is configured such that the minimum absolute value of the corrected q-axis voltage command value Vq ** is zero. In other words, even if the q-axis voltage command value Vq * is corrected, the sign is not reversed, the signs of the q-axis voltage command value Vq * and the corrected q-axis voltage command value Vq ** match, and the motor 21 The reverse rotation voltage is not applied.

Next, a processing procedure for calculating a corrected q-axis voltage command value by the steering angular velocity limiting unit of the present embodiment will be described with reference to the flowchart shown in FIG.
As shown in the figure, when the steering angular velocity limiting unit 61 acquires the steering angle θs, the steering angular velocity ωs, and the q-axis voltage command value Vq * as vehicle state quantities (step 101), the signs of the steering angle θs and the steering angular velocity ωs are obtained. It is determined whether or not the steering state is a cut-in state based on whether or not they are the same (step 102). If the signs of the steering angle θs and the steering angular velocity ωs are the same, it is determined that the steering state is the cut state (step 102: YES), and the routine proceeds to step 103. The signs of the steering angle θs and the steering angular velocity ωs indicate the steering direction of the steering 2.

  In step 103, the steering angular velocity limiting unit 61 calculates absolute values (| θs |, | ωs |) of the steering angle θs and the steering angular velocity ωs, and then refers to the limiting angular velocity map 63 to calculate the absolute value of the steering angle θs. The limiting angular velocity ωlim according to the above is calculated (step 104). Then, it is determined whether or not the value obtained by subtracting the limit angular velocity ωlim from the absolute value of the steering angular velocity ωs is greater than zero, that is, whether or not the absolute value of the steering angular velocity ωs is greater than the limit angular velocity ωlim (step 105). When the steering angular velocity ωs is larger than the limit angular velocity ωlim (step 105: YES), the compensation voltage value α is calculated (step 106: α = K × (| ωp | −ωlim)).

  Subsequently, the steering angular velocity limiting unit 61 determines whether or not the q-axis voltage command value Vq * is zero or more (step 107). If the q-axis voltage command value Vq * is zero or more (step 107) 107: YES), the calculated value Vq * _a is calculated by subtracting the compensation voltage value α from the q-axis voltage command value Vq * (step 108: Vq * _a = Vq * −α). Then, it is determined whether or not the calculated value Vq * _a is equal to or greater than zero (step 109). If the calculated value Vq * _a is equal to or greater than zero (step 109: YES), the corrected q-axis voltage command value Vq is determined. The value of the calculation value Vq * _a is calculated as the value of ** (step: 110: Vq ** = Vq * _a). On the other hand, when the calculated value Vq * _a is less than zero (step 109: NO), zero is calculated as the corrected q-axis voltage command value Vq ** (step 111: Vq ** = 0).

  On the other hand, when the q-axis voltage command value Vq * is less than zero (step 107: NO), the steering angular velocity limiting unit 61 calculates by adding the compensation voltage value α to the q-axis voltage command value Vq *. The value Vq * _a is calculated (step 112: Vq * _a = Vq * + α). Then, it is determined whether or not the calculated value Vq * _a is equal to or less than zero (step 113). If the calculated value Vq * _a is equal to or less than zero (step 113: YES), the corrected q-axis voltage command value Vq is determined. The value of the calculation value Vq * _a is calculated as the value of ** (step: 114: Vq ** = Vq * _a). On the other hand, when the calculated value Vq * _a is larger than zero (step 113: NO), zero is calculated as the corrected q-axis voltage command value Vq ** (step 115: Vq ** = 0).

  If the signs of the steering angle θs and the steering angular speed ωs are different, that is, if the steering state is not the cut-in state (step 102: NO), the steering angular velocity limiting unit 61 determines the value of the corrected q-axis voltage command value Vq **. The q-axis voltage command value Vq * is calculated as follows (step 116), and the q-axis voltage command value Vq * is not corrected. When the steering angular velocity ωs is equal to or lower than the limit angular velocity ωlim (step 105: NO), the process similarly proceeds to step 116, and the q-axis voltage command value Vq * is not corrected.

  When the motor control signal is generated based on the corrected q-axis voltage command value Vq ** corrected so that the absolute value of the q-axis voltage command value Vq * is decreased by the steering angular velocity limiting unit 61 as described above, The voltage applied to the motor 21 is reduced. Here, since the motor rotational angular velocity ωm is proportional to the voltage applied to the motor 21, the motor rotational angular velocity ωm is slowed by correcting the q-axis voltage command value Vq * as described above. Since the motor 21 is connected to the steering shaft 3 via the speed reduction mechanism 24 as described above, the steering angular velocity ωs of the steering 2 is suppressed by decreasing the motor rotational angular velocity ωm.

As described above, according to the present embodiment, the following operational effects can be achieved.
(1) When the steering angle θs is equal to or greater than the predetermined steering angle θsth near the steering end, the microcomputer 41 calculates the limiting angular velocity ωlim so that the limiting angular velocity ωlim decreases as the steering angle θs increases. A steering angular velocity limiting unit 61 is provided. Then, the steering angular velocity limiting unit 61 corrects the q-axis voltage command value Vq * to suppress the motor rotation angular velocity ωm when the steering angular velocity ωs is larger than the limiting angular velocity ωlim.

  According to the above configuration, when the steering angular velocity ωs of the steering 2 is larger than the limit angular velocity ωlim, the q-axis voltage command value Vq * is corrected and the motor rotational angular velocity ωm is suppressed. Can be suppressed. The limiting angular velocity ωlim is calculated so as to decrease based on the increase in the steering angle θs when the steering angle θs is equal to or greater than the predetermined steering angle θsth near the steering end. Therefore, the steering angular velocity ωs near the steering end is calculated. Is sufficiently suppressed, and the impact of the end pad can be sufficiently mitigated.

  Thus, in the above configuration, since the steering angular velocity ωs is suppressed by controlling the motor rotational angular velocity ωm, the steering 2 is different from the case where the q-axis current command value Iq * calculated as the control target value of the assist force is reduced. Even when the load during steering is small, the steering angular velocity ωs can be suppressed and the impact of the end contact can be sufficiently mitigated. In addition, since the q-axis current command value Iq * (assist force) is not reduced, a sufficient assist force can be applied to the steering system even when the load on steering the steering wheel 2 is large. Therefore, it is possible to sufficiently reduce the impact of the end pad when the load when steering the steering wheel 2 is low, and to apply a sufficient assist force when the load when steering the steering wheel 2 is high. Steering feeling can be realized.

(2) The steering angular velocity limiting unit 61 corrects the q-axis voltage command value Vq * when the steering state of the steering 2 is a cut-in state that increases the absolute value of the steering angle θs.
Here, the impact caused by the end contact becomes a problem when the steering state of the steering wheel 2 is a cut state. That is, even when the steering angle θs is in the vicinity of the steering end and the steering 2 is steered at a high steering angular velocity ωs, for example, in the case of performing the return steering that decreases the absolute value of the steering angle θs, the end contact is applied. Does not occur. Furthermore, if the q-axis voltage command value Vq * is corrected when the steering wheel 2 is switched back, the steering angular velocity ωs may be suppressed, leading to a deterioration in steering feeling. In this regard, according to the above configuration, when the steering state of the steering wheel 2 is the cut-in state, the q-axis voltage command value is corrected. Therefore, the steering angular velocity ωs is suppressed and steering is performed only when end contact becomes a problem. Feeling can be prevented from deteriorating.

  (3) The steering angular velocity limiting unit 61 superimposes the q-axis voltage command value Vq * on the q-axis voltage command value Vq * by superimposing a compensation voltage value α having a sign opposite to that of the q-axis voltage command value Vq *. I corrected it. According to the above configuration, for example, unlike the case of correcting by multiplying a predetermined compensation amount (gain) by the q-axis voltage command value Vq *, the correction amount does not change depending on the magnitude of the q-axis voltage command value Vq *. An appropriate compensation voltage value α (correction amount) can be easily calculated.

  (4) Since the steering angular velocity limiting unit 61 calculates the compensation voltage value α based on the difference between the steering angular velocity ωs and the limiting angular velocity ωlim, the q-axis voltage command value Vq * is appropriately set according to the magnitude of the steering angular velocity ωs. Thus, the compensation voltage value α is calculated to suitably reduce the impact of the end contact.

  (5) The steering angular velocity limiting unit 61 corrects the q-axis voltage command value Vq * because the minimum value of the absolute value of the corrected q-axis voltage command value Vq ** obtained by correcting the q-axis voltage command value Vq * is zero. However, the sign is not reversed, and a voltage that reversely rotates the motor 21 is not applied. Therefore, even if the q-axis voltage command value Vq * is corrected, the assist force from the EPS actuator 22 is not applied, and the driver applies a reaction force (force in the direction opposite to the steering direction) from the EPS actuator 22. It is possible to obtain an excellent steering feeling by preventing it from being received.

  (6) The steering angular velocity limiting unit 61 includes a limiting angular velocity map 63 showing the relationship between the steering angle θs and the limiting angular velocity ωlim, and calculates the limiting angular velocity ωlim based on the map 63. Can be calculated.

In addition, the said embodiment can also be implemented in the following aspects which changed this suitably.
In the above embodiment, the steering angle θs generated in the steering wheel 2 is detected by the steering sensor 33. However, the present invention is not limited to this. For example, the steering angle is based on the steering neutral position and the motor rotation angle θm detected by the rotation angle sensor 45. You may make it estimate (theta) s. Further, the pinion angle θp of the pinion shaft 10 may be detected as the steering angle θs generated in the steering 2.

  In the above embodiment, the rotational angular velocity conversion unit 62 detects the steering angular velocity by converting the differential value (motor rotational angular velocity ωm) of the motor rotational angle θm detected by the rotational angle sensor 45 into the steering angular velocity ωs of the steering 2. did. However, the present invention is not limited to this, and the steering angular velocity ωs may be detected in another manner, for example, the steering angle θs detected by the steering sensor 33 is differentiated to detect the steering angular velocity ωs.

  In the above embodiment, the steering angular velocity limiting unit 61 changes the value of the q-axis voltage command value Vq * when the steering state of the steering wheel 2 is the cut-in state. Regardless of the steering state, the value of the q-axis voltage command value Vq * may be changed.

  In the above embodiment, the compensation voltage value α (= K × (| ωp | −ωlim)) is calculated based on the difference between the steering angular velocity ωs and the limiting angular velocity ωlim. May be calculated in other manners, such as a predetermined value set in advance.

  In the above embodiment, the steering angular velocity limiting unit 61 is configured such that the minimum absolute value of the corrected q-axis voltage command value Vq ** is zero. However, the present invention is not limited to this, and the q-axis voltage command value Vq * is As a result of the correction, the sign may be inverted, and the signs of the q-axis voltage command value Vq * and the corrected q-axis voltage command value Vq ** may be reversed. In this case, the motor rotational angular velocity ωm is suppressed by applying a voltage that reversely rotates the motor 21.

  In the above embodiment, the q-axis voltage command value Vq * is corrected by superimposing the compensation voltage value α having the opposite sign and the sign of the q-axis voltage command value Vq * on the q-axis voltage command value Vq *. However, the present invention is not limited to this. For example, the q-axis voltage command value Vq * is corrected by multiplying the q-axis voltage command value Vq * by a compensation amount (gain) less than “1” (including zero or less). It may be.

  In the above embodiment, when the steering angle θs is equal to or greater than the predetermined steering angle θsth near the steering end, the limiting angular velocity map 63 is set so that the limiting angular velocity ωlim decreases in proportion to the increase in the steering angle θs. However, the present invention is not limited to this. For example, the limit angular velocity ωlim may be set to be reduced stepwise based on the increase in the steering angle θs.

  In the above embodiment, the steering angular velocity limiting unit 61 calculates the limiting angular velocity ωlim based on the limiting angular velocity map 63, but other configurations may be used. For example, if the relationship between the absolute value of the steering angle θs and the limiting angular velocity ωlim can be approximated by a function equation or the like, it may be calculated using a function equation.

  In the above embodiment, the three current sensors 43u, 43v, and 43w are used. However, the present invention is not limited to this, and each phase current value Iu using two current sensors (for example, the current sensors 43u and 43v). , Iv, Iw may be detected.

  In the above embodiment, a brushless motor is used as the motor 21 that is the drive source of the EPS actuator 22. However, the present invention is not limited to this, and the present invention may be applied to one using a brushless DC motor.

  In the above embodiment, 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.

  DESCRIPTION OF SYMBOLS 1 ... Electric power steering apparatus (EPS), 2 ... Steering, 21 ... Motor, 22 ... EPS actuator, 23 ... EPS, 33 ... Steering sensor, 41 ... Microcomputer, 42 ... Drive circuit, 45 ... Rotation angle sensor, 46 ... Current Command value calculation unit 47: Motor control signal generation unit 61: Steering angular velocity limiting unit 62: Rotational angular velocity conversion unit 63: Limiting angular velocity map Vd * ... d-axis voltage command value Vq * ... q-axis voltage command value , Vq ** ... corrected q-axis voltage command value, Vq * _a ... calculated value, .alpha .... compensation voltage value, .theta.s ... steering angle, .omega.s ... steering angular velocity, .omega.lim ... limit angular velocity.

Claims (6)

A steering force assisting device for applying an assisting force for assisting a steering operation to a steering system using a motor as a drive source;
Control means for controlling operation of the steering force assisting device through supply of driving power to the motor ;
Steering angle detecting means for detecting a steering angle generated in the steering;
Steering angular velocity detection means for detecting the steering angular velocity of the steering ,
The control means includes
A current command value calculation unit for calculating a current command value based on the steering torque and the vehicle speed;
A motor control signal that calculates a voltage command value by executing current feedback control that causes an actual current value to follow the current command value, and generates a motor control signal to apply a voltage indicated by the voltage command value to the motor A generator,
A drive circuit for supplying drive power to the motor based on the motor control signal;
And a limiting angular velocity calculating means for calculating a limit angular velocity of the upper limit of the steering angular velocity allowed according to the steering angle,
The limiting angular velocity calculating means calculates, when the steering angle is equal to or greater than a predetermined steering angle near the maximum steering angle, so that the limiting angular velocity is reduced based on an increase in the steering angle,
The motor control signal generator includes an electric power limiting unit that corrects the voltage command value so as to suppress the rotational angular velocity of the motor when the steering angular velocity is larger than the limiting angular velocity. Steering device. The electric power steering apparatus according to claim 1, wherein
The electric power steering device, wherein the angular velocity limiting means corrects the voltage command value when a steering state of the steering is a cut-in state that increases an absolute value of the steering angle. In the electric power steering apparatus according to claim 1 or 2,
The electric power steering apparatus, wherein the angular velocity limiting means corrects the voltage command value by superimposing a compensation voltage value having a sign opposite to that of the voltage command value on the voltage command value. In the electric power steering device according to claim 3,
The electric power steering device, wherein the angular velocity limiting means calculates the compensation voltage value based on a difference between the steering angular velocity and the limiting angular velocity. In the electric power steering apparatus according to any one of claims 1 to 4,
The electric power steering apparatus, wherein the angular velocity limiting means sets a minimum absolute value of a corrected voltage command value obtained by correcting the voltage command value to zero. In the electric power steering device according to any one of claims 1 to 5,
The electric power steering apparatus, wherein the angular velocity limiting means includes a map showing a relationship between the steering angle and the limiting angular velocity, and calculates the limiting angular velocity based on the map.

Images