JP7014029B2 - Steering control device - Google Patents

Description

The present invention relates to a steering control device.

Conventionally, in a steering control device, when a large assist torque is applied from a motor, a large impact is applied to the rack end mechanism, which causes a large impact sound or damage or deformation of components of the rack end mechanism. It has been pointed out that there is a risk.

To solve this problem, for example, the control device disclosed in Patent Document 1 limits the assist torque by multiplying the steering torque by the gain calculated from the absolute value of the steering angle and the absolute value of the steering speed near the end. .. That is, the hitting noise countermeasure unit of this control device has a gain g1 output corresponding to the absolute value | θ | of the steering angle and a gain g2 output corresponding to the absolute value | ω | of the steering speed. The gain signal G1 is calculated based on the product of. Since the steering torque value T from the torque sensor is multiplied by the gain K1 according to the gain signal G1, the assist torque near the end is limited at the time of turning.

Japanese Patent No. 4639861

When the steering angle or the steering speed changes abruptly, the control of Patent Document 1 has a problem that vibration is likely to occur because the stabilization process is not performed, and the degree of freedom of adaptation is small.

The present invention has been created in view of these points, and an object of the present invention is to provide a steering control device that stabilizes impact mitigation control at the time of end contact and increases the degree of freedom of adaptation.

The steering control device of the present invention includes a base assist unit (40) and an impact reduction control unit (200) at the time of end contact. The base assist unit generates an assist torque (Ta) output by the steering assist motor (80) according to the steering torque (Ts) of the driver. The impact mitigation control unit at the time of hitting the end reduces the steering angle and steering so as to reduce the absolute value of the assist torque generated by the base assist unit when the absolute value of the steering angle approaches the end, which is the upper limit value, and exceeds the angle threshold. A predetermined amount of operation is corrected based on the angular velocity.

The impact mitigation control unit at the time of end contact uses the input value as it is for the "amount that changes according to the steering angle", and the value that is filtered so as to remove the high frequency component for the "amount that changes according to the steering angular velocity". Is used to correct the predetermined operation amount. As the steering angular velocity, for example, the steering angular velocity after sign multiplication obtained by multiplying the sign of the steering angle is used.

In order to enable the driver to steer to the vicinity of the end with an appropriate steering feeling in the impact reduction control at the time of hitting the end, it is preferable not to reduce the assist torque until just before the end, and it is necessary to reduce the steering angular velocity in a short time from the start of control. There is. Therefore, the assist characteristic is suddenly changed near the end, causing vibration.

Therefore, in the present invention, the impact reduction control at the time of end contact is stabilized by performing filter processing on the steering angular velocity gain and the basic assist limit correction torque, which are quantities that change according to the steering angular velocity, and removing the high frequency component. The degree of adaptability can be increased.

On the other hand, if the filtering process is performed on the amount that changes according to the steering angle, there is a possibility that the end may collide with the end before the end protection is performed due to the delay in the response. Therefore, by using the input value as it is without filtering the amount that changes according to the steering angle, collision with the end can be prevented and end protection can be suitably performed.

Schematic diagram of the electric power steering system. The whole block diagram of the assist control part of the steering apparatus of one Embodiment. Configuration diagram of the impact reduction control unit when hitting the end. Configuration diagram of the base assist unit. The block diagram of the steering torque correction part. (A) Example of steering torque correction steering angle gain map, (b) Example of steering torque correction steering angular velocity gain map, (c) Example of frequency characteristic diagram of filter. Configuration diagram of the end assist limit control unit. (A) Example of assist limit correction steering angle gain map, (b) Example of basic assist limit correction torque map, (c) Example of filter frequency characteristic diagram. The figure which shows the vibration generation example in the actual vehicle by the impact reduction control at the time of end hitting. The figure explaining the influence of the filter processing on the steering angle gain.

Hereinafter, an embodiment of the steering control device will be described with reference to the drawings. The ECU as a "steering control device" is applied to the electric power steering system of the vehicle and controls the assist torque output by the steering assist motor.

[Configuration of electric power steering system]
As shown in FIG. 1, the electric power steering system 1 is a system that assists the driver in operating the steering wheel 91 by the drive torque of the steering assist motor (hereinafter, simply “motor”) 80. A handle 91 is fixed to one end of the steering shaft 92, and an intermediate shaft 93 is provided on the other end side of the steering shaft 92. The steering shaft 92 and the intermediate shaft 93 are connected by a torsion bar of the torque sensor 94, and the steering shaft 95 is formed by these. The torque sensor 94 detects the steering torque Ts based on the torsion angle of the torsion bar.

A gearbox 96 including a pinion gear 961 and a rack 962 is provided at an end of the intermediate shaft 93 opposite to the torque sensor 94. When the driver turns the handle 91, the pinion gear 961 rotates together with the intermediate shaft 93, and the rack 962 moves left and right as the pinion gear 961 rotates. Tie rods 97 provided at both ends of the rack 962 are connected to the tire 99 via a knuckle arm 98. The tie rod 97 reciprocates left and right, and the direction of the tire 99 changes by pulling or pushing the knuckle arm 98.

The motor 80 is, for example, a three-phase AC brushless motor, and outputs an assist torque that assists the steering force of the steering wheel 91 according to the drive voltage Vd output from the ECU 10. In the case of a three-phase AC motor, the drive voltage Vd means each phase voltage of U phase, V phase, and W phase. The rotation of the motor 80 is transmitted to the intermediate shaft 93 via the reduction mechanism 85 composed of the worm gear 86, the worm wheel 87, and the like. Further, the steering of the steering wheel 91 and the rotation of the intermediate shaft 93 due to the reaction force from the road surface are transmitted to the motor 80 via the reduction mechanism 85.

The electric power steering system 1 shown in FIG. 1 is a column assist type in which the rotation of the motor 80 is transmitted to the steering shaft 95, but the ECU 10 of the present embodiment is a rack assist type electric power steering system or a rack assist type. It is also applicable to a steer-by-wire system in which the steering wheel and the steering wheel are mechanically separated. Further, in another embodiment, a multi-phase AC motor other than the three-phase or a DC motor with a brush may be used as the steering assist motor.

Here, the entire mechanism from which the steering wheel 91 to the tire 99 to which the steering force of the steering wheel 91 is transmitted is referred to as "steering system mechanism 100". The ECU 10 controls the steering torque Ts generated by the steering system mechanism 100 by controlling the drive torque output by the motor 80 to the steering system mechanism 100. Further, the ECU 10 acquires the steering torque Ts, the steering angle θ, and the steering angular velocity ω from the steering system mechanism 100. Further, the ECU 10 acquires the vehicle speed V detected by the vehicle speed sensor 71 provided at a predetermined portion of the vehicle.

The ECU 10 includes an assist control unit 15 and a current feedback unit 70, and operates by electric power from an in-vehicle battery (not shown). The assist control unit 15 calculates an assist torque Ta that assists the driver in steering. The current feedback unit 70 calculates the drive voltage Vd applied to the motor 80 by feedback-controlling the actual current flowing through the motor 80 with respect to the target current based on the assist torque Ta. By applying the drive voltage Vd to the motor 80, the ECU 10 generates steering torque Ts in the steering system mechanism 100 to be controlled.

The various arithmetic processes in the ECU 10 may be software processes by executing a program stored in advance in a substantive memory device such as a ROM on the CPU, or hardware processes by a dedicated electronic circuit. ..

[ECU configuration]
(One embodiment)
First, with reference to FIGS. 2 to 4, a schematic configuration of an assist control unit in the ECU 10 of the embodiment will be described. As shown in FIG. 2, the assist control unit 15 includes an impact reduction control unit 200 at the time of end contact and a base assist unit 40, and outputs an assist torque Ta to the vehicle 100. The "end contact" means a collision at the rotation limit position of the handle 91, which will be described in detail later.

The impact reduction control unit 200 at the time of end contact reduces the assist torque Ta and the steering angular velocity ω at the time of end contact, and reduces the impact load applied to the intermediate shaft 93. Steering torque Ts, steering angle θ, and steering angular velocity ω are input to the end-hit impact reduction control unit 200. The end-hit impact mitigation control unit 200 has a "predetermined amount of operation" based on the steering angle θ and the steering angular velocity ω so as to reduce the absolute value of the assist torque Ta generated by the base assist unit 40 at the time of end-hit. Make corrections.

As shown in FIG. 3, the end-hit impact reduction control unit 200 includes a steering torque correction unit 20 and an end assist limit control unit 30. The steering torque correction unit 20 corrects the detected value of the steering torque Ts as a predetermined operation amount based on the steering torque Ts, the steering angle θ, and the steering angular velocity ω, and calculates the “steering torque after end contact correction”. Details will be described later with reference to FIGS. 5 and 6. The end assist limit control unit 30 corrects the assist torque limit value as a predetermined operation amount based on the steering angle θ and the steering angular velocity ω, and calculates the “end contact corrected assist torque limit value”. Details will be described later with reference to FIGS. 7 and 8.

Returning to FIG. 2, in addition to the steering angle θ and the steering angular velocity ω, the base assist unit 40 has the “steering torque after end contact correction” and the “assist torque limit value after end application correction” acquired from the impact reduction control unit 200 at the time of end application. ], The assist torque Ta is generated. The final assist torque Ta, in which the correction torque is further added to the output of the base assist unit 40, may be output to the current feedback control unit 70. In that configuration, the output of the base assist unit 40 before the correction torque is added can be rephrased as "basic assist torque Tb". In the following, the correction torque is not considered and the basic assist torque Tb is treated as equal to the final assist torque Ta.

FIG. 4 shows a configuration example of the base assist unit 40. The base assist unit 40 has an appropriate steering feeling such as "the steering wheel is heavy / light", "there is a response / no response", and "there is a viscous feeling / no" that the driver feels when operating the steering wheel 91. The target steering torque Ts ^* is set as described above, and the assist torque Ta that realizes the target steering torque Ts * is calculated.

The base assist unit 40 includes an input adder 41, a filter 42, a target steering torque calculation unit 44, a torque deviation calculator 50, and a servo controller 55. The input adder 41 adds the assist torque Ta, which is the output of the servo controller 55, and the target steering torque Ts ^* . In another embodiment, the assist torque Ta and the steering torque Ts, which are the outputs of the servo controller 55, may be added. Further, when the output of the servo controller 55 is the basic assist torque Tb, the input adder 41 adds the basic assist torque Tb and the target steering torque Ts ^* or the steering torque Ts.

The filter 42 extracts a component in a band having a predetermined frequency, for example, 10 Hz or less from the added torque, and outputs it as an estimated load Tx. The target steering torque calculation unit 44 calculates the target steering torque Ts ^* based on the estimated load Tx. The target steering torque calculation unit 44 may further calculate the target steering torque Ts ^* according to the vehicle speed.

The torque deviation calculator 50 calculates the torque deviation ΔTs by subtracting the steering torque after the end contact correction from the target steering torque Ts ^* . The servo controller 55 calculates the assist torque Ta so that the target steering torque Ts ^* follows the steering torque after the end hit correction, that is, the torque deviation ΔTs approaches zero. The absolute value of the assist torque Ta calculated by the servo controller 55 is limited by the assist torque limit value after the end contact correction.

Next, the detailed configurations of the steering torque correction unit 20 and the end assist limit control unit 30 of the end-hit impact reduction control unit 200 will be described with reference to FIGS. 5 to 8.

Here, the definitions of the symbols of the steering angle θ, the steering angular velocity ω, and the steering torque Ts will be described. The sign of the steering angle θ is defined by the current position of the steering wheel 91 with respect to the neutral position. For example, the steering angle θ on the left side with respect to the neutral position is defined as positive, and the steering angle θ on the right side with respect to the neutral position is defined as negative. The sign of the steering angular velocity ω is defined by the rotation direction corresponding to the sign of the steering angle θ. That is, when the sign of the steering angle θ is defined as described above, the steering angular velocity ω in the left rotation direction is defined as positive, and the steering angular velocity ω in the right rotation direction is defined as negative.

The sign of the steering torque Ts is defined in the same manner as the sign of the steering angular velocity ω. Here, the sign of the steering torque Ts represents the direction in which the torque is applied, regardless of whether or not the steering wheel 91 is actually rotating in that direction. For example, due to a road surface load, inertial torque, or the like, the steering wheel 91 may be stopped even if the steering torque Ts is applied, or the steering wheel 91 may be rotated in the direction opposite to the steering torque Ts.

In another embodiment, contrary to the above, the steering angle θ on the right side with respect to the neutral position, the steering speed ω in the right rotation direction, and the steering torque Ts are defined as positive, and the steering angle θ on the left side with respect to the neutral position is defined as positive. , Steering speed ω in the counterclockwise direction and steering torque Ts may be defined as negative.

Hereinafter, the upper limit of the absolute value of the steering angle θ, that is, the rotation limit position of the steering wheel 91 is referred to as an “end”. The end corresponds to, for example, the position where the end of the rack 962 mechanically collides with the mating component. Further, the movement of the handle 91 in the rotational direction from the neutral position toward the end is called "cutting". The movement in the direction of rotation from the end to the neutral position is called "cutback". The state of turning or turning back can be determined by the signs of the steering angle θ, the steering angular velocity ω, and the steering torque Ts.

For example, when the steering angle θ and the steering angular velocity ω have the same sign, it is determined to be in the cut state, and when the steering angle θ and the steering angular velocity ω have different signs, it is determined to be in the cutback state. Similarly, the determination can be made by using a combination of the steering angle θ and the steering torque Ts, the steering angular velocity ω and the steering torque Ts, and the steering angle θ and the steering angular velocity ω and the steering torque Ts.

By the way, conventionally, as a technique for reducing the impact of hitting the end and protecting the end, the assist torque is limited by multiplying the steering torque by the gain calculated from the absolute value of the steering angle and the absolute value of the steering speed near the end. The technology to do is known. However, since the control of the prior art does not perform the stabilization process, there is a problem that vibration is likely to occur and the degree of freedom of adaptation is small. Therefore, it is an object of the present embodiment to stabilize the impact mitigation control at the time of hitting the end, suppress the vibration, and increase the degree of freedom of adaptation.

FIG. 5 shows a configuration example of the steering torque correction unit 20. The steering torque correction unit 20 includes a steering torque correction steering angular velocity gain calculation unit 23 and a steering torque correction steering angle gain calculation unit 24 for correcting the detected value of the steering torque Ts. Steering torque correction The steering angular velocity gain calculation unit 23 calculates the steering angular velocity gain gωs that changes according to the steering angular velocity ω. The steering torque correction steering angle gain calculation unit 24 calculates the steering angle gain gθs that changes according to the steering angle θ.

The steering angular velocity ω is multiplied by the sign of the steering angle θ acquired by the code acquisition unit 21 by the code multiplier 22. Then, the steering angular velocity ωsgn after sign multiplication is input to the steering torque correction steering angular velocity gain calculation unit 23. That is, the steering angular velocity gain gωs changes according to the steering angular velocity ωsgn after sign multiplication. When the steering angle θ and the steering angular velocity ω have the same sign and the steering angular velocity ωsgn after multiplication is positive, it means that the handle 91 is in a cut state in which the handle 91 is rotated in the end direction. On the other hand, when the steering angle θ and the steering angular velocity ω have different signs and the steering angular velocity ωsgn after sign multiplication is negative, it means that the handle 91 is rotating in the neutral position direction and is in a turning-back state.

In this way, the steering torque correction unit 20 determines whether the cutting state or the turning back state, that is, whether or not there is a possibility of collision with the end, by using the steering angular velocity ωsgn after sign multiplication. Then, in the case of a cut state where there is a possibility of collision with the end, the steering torque correction unit 20 outputs the steering torque after the end hit correction corrected by reducing the absolute value of the detected value of the steering torque Ts as described below. , Suppresses the impact at the time of end collision. On the other hand, in the case of a switchback state in which there is no possibility of collision with the end, the steering torque correction unit 20 does not perform reduction correction and outputs the detected value of the steering torque Ts as it is. Therefore, it is possible to avoid unnecessarily increasing the steering torque Ts at the time of turning back.

The steering angular velocity gain gωs and the steering angular velocity gain gθs are set in the range of 0 to 1, and are 0 when the steering torque Ts is not reduced and corrected, and greater than 0 and 1 or less depending on the amount of decrease when the steering torque Ts is reduced and corrected. Take the value of. The filter 25 removes the high frequency component of the steering angular velocity gain gωs by the filter processing and attenuates the high frequency fluctuation. The product gain calculator 26 multiplies the filtered steering angular velocity gain gωs and the steering angular velocity gain gθs to calculate the product gain gms. Here, as indicated by (x) in the figure, the steering angle gain gθs and the product gain gms are not filtered, and the input values are used as they are. The reason will be described later.

The gain subtractor 27 calculates the steering torque correction gain by subtracting the product gain gms from 1, and the correction gain multiplier 29 calculates the steering torque after the end hit correction by multiplying the steering torque Ts by the steering torque correction gain. .. That is, when the product gain gms increases, the steering torque correction gain decreases, and as a result, the steering torque after end contact correction decreases.

6 (a) and 6 (b) show map examples of the steering angular velocity gain gθs and the steering angular velocity gain gωs, respectively. In the example of FIG. 6A, the position where the steering angle θ is ± 460 [deg] is the end, and ± 400 [deg] is the angle threshold value. The steering angle gain gθs is 0 when the absolute value of the steering angle θ is 400 [deg] or less, and increases from 0 to 1 in the section from 400 [deg] to 420 [deg] approaching the end to 420 [deg]. deg] or more, it is 1. Therefore, when the absolute value of the steering angle θ approaches the end and exceeds the angle threshold value, the steering torque correction unit 20 reduces the absolute value of the steering torque after the end contact correction.

In the example of FIG. 6B, the steering angular velocity gain gωs is 0 when the steering angular velocity ωsgn after sign multiplication is 300 [deg / s] or less, and is a section from 300 [deg / s] to 400 [deg / s]. It increases from 0 to 1 and is 1 when it is 400 [deg / s] or more.

Based on such a map, the steering torque correction unit 20 determines the absolute value of the steering torque after end contact correction as the absolute value of the steering angle θ is closer to the end and the absolute value of the steering angular velocity ω toward the end is larger. Reduce. That is, the steering torque after the end contact correction is a value that has been reduced and corrected so that the absolute value is smaller than the absolute value of the detected value of the steering torque Ts.

FIG. 6C shows a frequency characteristic diagram of the first-order lag type of the filter 25. The cutoff frequency f _CO at which the gain is -3 dB is about 5 Hz, and is set to "10 Hz to several tens of Hz" or less, which corresponds to the resonance frequency of the steering system mechanism 100. As a result, delay compensation is appropriately performed for the resonance frequency of the steering system mechanism 100, and stabilization is realized.

FIG. 7 shows a configuration example of the end assist limit control unit 30. The end assist limit control unit 30 has a basic assist limit correction torque calculation unit 33 and an assist limit correction steering angle gain calculation unit 34 for correcting the assist torque limit value. The basic assist limit correction torque calculation unit 33 calculates the basic assist limit correction torque that changes according to the steering angular velocity ω.

Similar to the steering torque correction unit 20, the steering angular velocity ω is obtained by multiplying the sign of the steering angle θ acquired by the code acquisition unit 31 by the code multiplier 32, and the steering angular velocity ωsgn after the code multiplication is the basic assist limit correction torque calculation unit. It is input to 33. That is, the basic assist limit correction torque changes according to the steering angular velocity ωsgn after sign multiplication. As a result, similarly to the steering torque correction unit 20, it is determined whether it is in the cut state or the cut back state, and the impact reduction control at the time of end contact is executed only in the cut state.

The assist limit correction steering angle gain calculation unit 34 calculates the assist limit correction steering angle gain gθlim that changes according to the steering angle θ. The gain gθlim is set in the range of 0 to 1, and takes 0 when the steering torque Ts is not reduced and corrected, and takes a value larger than 0 and 1 or less depending on the amount of reduction when the steering torque Ts is reduced and corrected.

The filter 35 removes the high frequency component of the basic assist limit correction torque by the filter processing and attenuates the high frequency fluctuation. The multiplier 36 calculates the assist limit correction torque by multiplying the basic assist limit correction torque after the filter by the assist limit correction steering angle gain gθlim. Similar to the steering torque correction unit 20, as indicated by the (x) mark in the figure, the steering angle gain gθlim and the assist limit correction torque are not filtered, and the input values are used as they are. The reason will be described later.

The limit value calculator 39 subtracts the assist limit correction torque from the product of the motor rated torque calculated by the multiplier 38 and the gear ratio, and calculates the assist torque limit value after the end contact correction. That is, when the absolute value of the assist limit correction torque increases, the absolute value of the assist torque limit value after the end hit correction decreases.

FIG. 8A shows the same map as the map of the steering angle gain gθs of the steering torque correction unit 20 shown in FIG. 6A as a map example of the steering angle gain gθlim. However, a map having characteristics different from those shown in FIG. 6A may be used. The end assist limit control unit 30 reduces the absolute value of the assist torque limit value after end contact correction when the absolute value of the steering angle θ approaches the end and exceeds the angle threshold value.

In the example of FIG. 8B, the basic assist limit correction torque is 0 [Nm] when the steering angular velocity ωsgn after sign multiplication is 300 [deg / s] or less, and is from 300 [deg / s] to 400 [deg / s]. ], It increases from 0 to 50 [Nm], and when it is 400 [deg / s] or more, it is 50 [Nm].

Based on the map of such characteristics, the end assist limit control unit 30 has the absolute value of the assist limit correction torque as the absolute value of the steering angle θ is closer to the end and the absolute value of the steering angular velocity ω toward the end is larger. As a result, the absolute value of the assist torque limit value after end contact correction is decreased.

FIG. 8C shows the same diagram as the frequency characteristic diagram of the filter 25 shown in FIG. 6C as an example of the frequency characteristic diagram of the first-order lag type of the filter 35. However, a frequency characteristic diagram different from that shown in FIG. 6 (c) may be used. The cutoff frequency f _CO is about 5 Hz, and is set to "10 Hz to several tens of Hz" or less, which corresponds to the resonance frequency of the steering system mechanism 100. As a result, delay compensation is appropriately performed for the resonance frequency of the steering system mechanism 100, and stabilization is realized.

Next, regarding the significance of providing the filters 25 and 35 in the steering torque correction unit 20 and the end assist limit control unit 30, the steering angle gain map of FIGS. 6A and 8A and the actual vehicle data of FIG. 9 are shown. It will be explained with reference to.

As shown in FIGS. 6A and 8A, the steering angle gain is 0 to 1 in the section from 400 [deg] to 420 [deg] in which the absolute value | θ | of the steering angle is the angle threshold. Increases to. In this way, by making the gradient of the steering angle gain during the transition from the control non-operating region to the controlling operating region steep, the driver can steer to the vicinity of the end with an appropriate steering feeling. The steering angular velocity when the driver steers the large steering angle is about 600 [deg / s] at the maximum. If the section of 20 [deg] is steered without decelerating at a steering angular velocity of 600 [deg / s], the time during which the control is completely operating is about 0.07 [s]. In order to reduce the steering angular velocity in a short time of 0.07 [s], it is necessary to suddenly change the assist characteristic near the end, which causes vibration.

FIG. 9 shows an example of vibration generation in an actual vehicle by impact reduction control at the time of end contact. In this example, the steering angle θ is a negative value, and the steering angular velocity ω and the steering torque Ts are also negative values. By the end contact control at time te, the absolute value of the assist torque Ta decreases, and the steering angular velocity ω shifts to deceleration. After that, vibration of 10 to several tens of Hz, which is the resonance frequency of the steering system mechanism 100, is generated in the assist torque Ta.

Therefore, in the end-hit impact reduction control unit 200 of the present embodiment, the steering torque correction unit 20 and the end assist limit control unit 30 have a steering angular velocity gain gωs and a basic assist limit correction torque, which are quantities that change according to the steering angular velocity ω. To filter. In this way, the generation of vibration is suppressed by removing the high frequency component, attenuating the fluctuation and stabilizing it. Therefore, the degree of freedom of conformity can be increased. On the other hand, the steering torque correction unit 20 and the end assist limit control unit 30 do not filter the steering angle gains gθs and gθlim that change according to the steering angle θ, and use the input values as they are.

Subsequently, with reference to FIG. 10, the reason why the steering angle gains of the steering torque correction unit 20 and the end assist limit control unit 30 are not filtered by the LPF (low-pass filter) will be described. The solid line shows the simulation result of the gain response when there is no LPF, and the broken line shows the case where the LPF having a cutoff frequency of 5 Hz is used. The position of about 0.75 seconds corresponds to the end collision time.

Without the LPF, the steering angle gain reaches 1 before the end collision time, and the assist torque is sufficiently suppressed before the end collision. On the other hand, when the LPF is used, the rise of the steering angle gain is delayed and the end collision time is reached before reaching 1, so that a sufficient protection effect cannot be obtained at the time of the end collision.

Therefore, as the amount that changes according to the steering angular velocity ω, only the steering angular velocity gain gωs is filtered by the steering angular velocity correction unit 20, and only the basic assist limit correction torque is filtered by the end assist limitation control unit 30, and the steering angular velocity gains gθs and gθlim are obtained. Do not filter. Thereby, in the present embodiment, when the steering angle gains gθs and gθlim rise, the end collision before reaching 1 can be avoided, and both stabilization and end protection can be realized.

(Other embodiments)
(A) The impact reduction control unit 200 at the time of hitting the end is not limited to the configuration including both the steering torque correction unit 20 and the end assist limit control unit 30, and may include only one of them. Further, the method of limiting the assist torque in the end assist limit control unit 30 is not limited to the method of guarding the upper limit of the absolute value by the limit value. For example, the configuration may be such that the gain is multiplied by the assist torque or the steering torque, or the configuration is limited by adding the assist torque.

(B) The base assist unit 40 does not have to include the servo controller 55 that calculates the assist torque Ta so that the target steering torque Ts ^* follows the steering torque after the end contact correction, and "according to the steering torque Ts". Anything that "generates the assist torque Ta output by the steering assist motor 80" may be used. The specific configuration is not limited to that of the above embodiment.

As described above, the present invention is not limited to the above embodiment, and can be implemented in various embodiments without departing from the spirit of the present invention.

10 ... ECU (steering control unit),
200 ... Impact reduction control unit when hitting the end,
20 ... Steering torque correction unit,
30 ... End assist limit control unit,
40 ... Base assist section,
80 ... Steering assist motor.

Claims (6)

A base assist unit (40) that generates an assist torque (Ta) output by the steering assist motor (80) according to the steering torque (Ts) of the driver.
A predetermined amount of operation based on the steering angle and steering angular velocity so as to reduce the absolute value of the assist torque generated by the base assist unit when the absolute value of the steering angle approaches the end which is the upper limit value and exceeds the angle threshold value. Impact reduction control unit (200) when hitting the end, which corrects
Equipped with
The impact reduction control unit at the time of end contact uses the input value as it is for the amount that changes according to the steering angle, and uses the value that has been filtered so as to remove the high frequency component for the amount that changes according to the steering angular velocity. A steering control device that corrects the predetermined operation amount. The impact reduction control unit at the time of hitting the end increases the amount of reduction correction of the absolute value of the assist torque as the absolute value of the steering angle is closer to the end and the absolute value of the steering angular velocity toward the end is larger. The steering control device according to claim 1, wherein the steering control device for correcting the predetermined operation amount. The steering control device according to claim 1 or 2, wherein the end-hit impact reduction control unit filters an amount that changes according to the steering angular velocity after sign multiplication by which the sign of the steering angle is multiplied. The end-hit impact reduction control unit includes a steering torque correction unit (20) that corrects a detection value of steering torque as the predetermined operation amount.
The steering control device according to any one of claims 1 to 3, wherein the absolute value of the assist torque generated by the base assist unit is reduced and corrected by the reduction correction of the absolute value of the steering torque detection value. The end-hit impact reduction control unit includes an end assist limit control unit (30) that corrects an assist torque limit value, which is a limit value of the assist torque generated by the base assist unit, as the predetermined operation amount.
The steering control device according to any one of claims 1 to 4, wherein the absolute value of the assist torque generated by the base assist unit is reduced and corrected by the reduction correction of the absolute value of the assist torque limit value. The cutoff frequency of the filter that removes the amount of high-frequency components that change according to the steering angular velocity in the end-applying impact reduction control unit is set to be equal to or lower than the resonance frequency of the steering system mechanism on which the steering control device is mounted. Item 6. The steering control device according to any one of Items 1 to 5.

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