JP5446444B2 - Vehicle steering control device and vehicle with steering control device - Google Patents

Description

  The present invention relates to a vehicle steering control device that controls steering of a vehicle, and a vehicle with a steering control device.

  As this type of technology, the technology described in Patent Document 1 below is disclosed. In this publication, a transmission ratio (also referred to as a steering angle ratio), which is a ratio between a steering operation angle (steering angle) and a steering angle of a steering wheel, is variable in a transmission system between a steering wheel (steering wheel) and a steering wheel. There is disclosed a vehicle steering apparatus that includes a transmission ratio variable mechanism (transmission ratio variable means) that controls a transmission ratio by driving a motor (actuator) provided in the transmission ratio variable mechanism. In the vehicle steering apparatus described in Patent Document 1, when the motor of the transmission ratio variable mechanism is overheated, the transmission ratio is locked (fixed) to a predetermined transmission ratio. .

JP 2001-270453 A

  In the above-described prior art, when the motor of the transmission ratio variable mechanism is overheated, the ratio of the rotation angle (steering angle) of the steering wheel (steering wheel) and the steering angle of the steered wheels, that is, the transmission ratio is fixed. The vehicle behavior with respect to the steering angle changes greatly before and after the transmission ratio is fixed. In particular, in the above-described prior art, since the transmission ratio is fixed after detecting overheating of the motor, the vehicle behavior with respect to steering of the steering wheel is drastically changed, which may cause the driver to feel uncomfortable.

  The present invention has been made paying attention to the above problems, and an object of the present invention is to provide a vehicle steering apparatus that can prevent the driver from feeling uncomfortable.

In order to achieve the above object, in the present invention, the load of the front wheel steering actuator that drives the steering angle ratio variable means for changing the steering angle ratio, which is the ratio of the steering angle of the steering wheel and the steering angle of the front wheels, is determined in advance. When the state higher than the predetermined threshold value continues for a set time or longer, the front wheel steering actuator is controlled so as to be a value closer to 1 than the steering angle ratio at that time.
Further, when the load of the rear wheel steering actuator that gives the rear wheel steering angle to the rear wheel continues to be higher than a predetermined threshold value for a set time or longer, the rear wheel steering angle is reduced. The rear wheel steering actuator was controlled.

  Therefore, compared to the case where the steering actuator is stopped and the steering angle ratio is fixed after the steering actuator is overheated, the steering angle ratio is set to the steering angle ratio at that time before the steering actuator is overheated. By controlling the steering actuator so that it becomes a value closer to 1 than the ratio, the steering actuator can be prevented from becoming overheated and the change in vehicle behavior can be reduced, reducing the sense of incongruity given to the driver can do.

1 is an overall system diagram of a vehicle steering apparatus for a vehicle according to a first embodiment. FIG. 2 is a control block diagram of the vehicle steering apparatus according to the first embodiment. FIG. 6 is a diagram illustrating a correction gain map according to the first embodiment. It is a schematic diagram which shows the range which sets the correction gain of Example 1 small. FIG. 5 is a diagram illustrating a numerical example of a correction gain according to the first embodiment. It is a schematic diagram which shows the range which sets the correction gain of Example 2 small. FIG. 10 is a diagram illustrating a numerical example of a correction gain according to the second embodiment. It is a schematic diagram which shows the range which sets the correction gain of Example 3 small. FIG. 10 is a diagram illustrating a numerical example of correction gain according to the third embodiment.

[Example 1]
〔overall structure〕
FIG. 1 is an overall system diagram of the vehicle steering apparatus 1 mounted on the vehicle 15 of the first embodiment. The vehicle steering apparatus 1 can change the steering angle ratio, which is the ratio of the steering angle of the front wheels 4 to the steering angle of the steering wheel 2, and can also steer the rear wheels 8. It is.

  The vehicle steering apparatus 1 includes a steering wheel 2 as a front wheel side mechanism, a front wheel steering mechanism 5 including a rack 5a connected to the front wheel 4, and a pinion gear 6c geared to a rack gear provided on the rack 5a. A pinion shaft 6b connected to the pinion gear 6c, a steering shaft 6a connected to the handle 2, and a steering angle ratio variable mechanism 20 (steering angle ratio variable) provided between the pinion shaft 6b and the steering shaft 6a. Means), a front wheel steering actuator 7 that drives the steering angle ratio variable mechanism to vary the steering angle ratio, and a power steering actuator 18 that applies a steering assist torque to the front wheel steering mechanism 5. In addition, the vehicle steering apparatus 1 includes a rear wheel steering mechanism 9 that steers the rear wheel 8 and a rear wheel steering actuator 10 that is connected to the rear wheel steering mechanism 9 as a rear wheel side mechanism.

  The front wheel steering actuator 7 includes, for example, a motor and a speed reducer, and is driven by a command current from the front wheel steering actuator control unit 11. The steering angle ratio variable mechanism 20 inputs the steering angle, which is the rotation angle of the steering shaft 6a by the steering of the handle 2 by driving the front wheel steering actuator 7, and adjusts the front wheel auxiliary steering angle with respect to the input steering angle. By outputting the rotation angle to the pinion shaft 6b, the ratio of the rotation angle of the pinion shaft 6b to the steering angle of the handle 2 is made variable. Since the relationship between the rotation angle of the pinion shaft 6b and the turning angle of the front wheel 4 is uniquely determined by the gear ratio between the pinion gear 6c and the rack gear (that is, the gear ratio of the so-called rack and pinion mechanism), the pinion shaft Hereinafter, the rotation angle of 6b is referred to as a steering angle, and the ratio of the rotation angle (steering angle) of the pinion shaft 6b to the rotation angle (steering angle) of the steering shaft 6a is referred to as a steering angle ratio.

  The rear wheel turning actuator 10 has an output shaft connected to a rack shaft of a rear wheel turning mechanism 9 for turning the rear wheel 8 via a speed reducer. The rear wheel steering actuator 10 is driven by a command current from a four-wheel active steering control unit 12 (steering angle ratio control means). The rear wheel steering actuator 10 gives the rear wheel 8 a steering angle in the same phase as or opposite to the steering direction of the front wheel 4 by giving a rear wheel steering angle to the rear wheel 8.

  As a control system of the vehicle steering apparatus 1, a steering angle sensor 3 (steering angle detection means) that detects the steering angle γ of the handle 2 and a lateral acceleration sensor 16 (lateral acceleration detection) that detects a lateral acceleration Gy acting on the vehicle 15. Means), a vehicle speed sensor 14 for detecting the vehicle speed V, a front wheel steering actuator control unit 11 for controlling the front wheel steering actuator 7, a rear wheel steering actuator control unit 12e for controlling the rear wheel steering actuator 10, and a front wheel rotation. A four-wheel active steering control unit 12 (steering angle ratio control means) that calculates control amounts of the rudder actuator 7 and the rear wheel steering actuator 10 and a power steering actuator control unit 17 that controls the power steering actuator 18 are provided. .

  The steering angle sensor 3, the lateral acceleration sensor 16, the vehicle speed sensor 14, the four-wheel active steering control unit 12, and the power steering actuator control unit 17 are connected to the low-speed vehicle CAN 13 and share various information via the low-speed vehicle CAN 13. doing. The front wheel steering actuator control unit 11 (front wheel steering actuator control means) and the four-wheel active steering control unit 12 are connected by a high-speed dedicated CAN 19 and share information with each other.

ここで、

である。 [Control block]
FIG. 2 is a control block diagram of the vehicle steering apparatus 1.
The four-wheel active steering control unit 12 includes a target value generation unit 12a, a target output generation unit 12b (target front wheel turning angle calculation means, target rear wheel turning angle calculation means), and an output correction unit 12c (target front wheel turning angle). A correction means, a target rear wheel turning angle correction means), a traveling state determination unit 12d (load detection means), and a rear wheel turning actuator control unit 12e (rear wheel turning actuator control means).
(Vehicle model)
The target value generation unit 12a calculates vehicle parameters using the vehicle model shown below. In general, assuming a two-wheel model, the yaw rate and lateral speed of the vehicle can be expressed by the following equation (1).

here,

It is.

となる。

Obtaining the transfer function of the yaw rate and lateral velocity for front wheel steering from the state equation,

It becomes.

ここで、

The yaw rate transfer function is expressed by the following equation (5) from equation (3).

here,

ここで、

Similarly, the lateral velocity transfer function is expressed by the following equation (7) from equation (4).

here,

が求められる。 From the above, vehicle parameters

Is required.

(Target value generator)
The target value generation unit 12a obtains the target yaw rate ψ ′ * and the target lateral velocity Vy * from the steering angle γ and the vehicle speed V.

The target yaw rate ψ ′ * is expressed by the following equation (9).

The target lateral speed Vy * is expressed by the following equation (10).

ただし、yrate_gain_map，yrate_omegn_map，yrate_zeta_map，yrate_zero_mapはチューニングパラメータである。 Here, the parameter of the target yaw rate ψ ′ * is expressed by the following equation (11).

However, yrate_gain_map, yrate_omegn_map, yrate_zeta_map, and yrate_zero_map are tuning parameters.

ただし、vy_gain_map，vy_omegn_map，vy_zeta_map，vy_zero_mapはチューニングパラメータである。 The parameter of the target lateral speed Vy * is expressed by the following equation (12).

However, vy_gain_map, vy_omegn_map, vy_zeta_map, and vy_zero_map are tuning parameters.

このモデルから下記の式(14)を得る。

よって、目標後輪転舵角δ*は、下記の式(15)となる。

目標ヨーレートと目標横速度Vy*から、下記の式(16)を用いて目標前輪転舵角θ*を算出する。

(Target output generator)
The target output generator 12b calculates a target rear wheel turning angle δ * and a target front wheel turning angle θ * based on the target yaw rate ψ ′ * and the target lateral speed Vy *.

From this model, the following equation (14) is obtained.

Therefore, the target rear wheel turning angle Δ * is expressed by the following equation (15).

The target front wheel turning angle θ * is calculated from the target yaw rate and the target lateral velocity Vy * using the following equation (16).

(Running state determination unit)
The traveling state determination unit 12d calculates a load L (γ ′, Gy) acting on the front wheel steering actuator 7 and the rear wheel steering actuator 10. The load L (γ ′, Gy) acting on the front wheel steering actuator 7 and the rear wheel steering actuator 10 is obtained from the steering angular velocity γ ′ and the lateral acceleration Gy. The higher the steering angular velocity γ ′, the larger the lateral acceleration Gy. It is calculated so high. Then, a correction gain Xij is obtained according to the calculated load L (γ ′, Gy). When the load L (γ ′, Gy) is higher than the threshold value L1 for a set time or longer, the correction gain Xij decreases as the load L (γ ′, Gy) increases. It is set. The correction gain Xij is used for calculation in the output correction unit 12c described later, and is set according to the loads on the front wheel steering actuator 7 and the rear wheel steering actuator 10. The smaller the correction gain Xij, the smaller the front wheel auxiliary turning angle given by the front wheel turning actuator 7 and the rear wheel turning angle given by the rear wheel turning actuator 10.

  The correction gain Xij is obtained using a map. FIG. 3 is a diagram showing a map of the correction gain Xij. As shown in FIG. 3, the correction gain Xij is set according to the steering angular velocity γ ′ and the lateral acceleration Gy. Here, the steering angular velocity γ ′ and the lateral acceleration Gy used when obtaining the correction gain Xij are those that maintain values over the set time and beyond. That is, the vehicle behavior is prevented from frequently changing by performing correction by instantaneously increasing the steering angular velocity γ ′ or increasing the lateral acceleration Gy.

  FIG. 4 is a schematic diagram showing a range in which the correction gain Xij is set small. As shown in FIG. 4, it can be divided into four regions according to the lateral acceleration Gy and the steering angular velocity γ ′. The first region is a region where the lateral acceleration Gy is small and the steering angular velocity γ ′ is slow, that is, a normal traveling region for the vehicle 15, and a steering wheel operation is performed slowly. In this first region, the correction gain Xij is set to “1” so that the front wheel auxiliary turning angle and the rear wheel turning angle are not reduced. The second region is a region where the lateral acceleration Gy is large and the steering angular velocity γ ′ is slow, that is, a limit traveling region for the vehicle 15 and a steering operation is performed slowly. In this second region, the correction gain Xij is set to “1” or less to reduce the front wheel auxiliary turning angle and the rear wheel turning angle.

  The third region is a region where the lateral acceleration Gy is small and the steering angular velocity γ ′ is fast, that is, a normal traveling region for the vehicle 15, and a steering wheel operation is busy. In the third region, the correction gain Xij is set to “1” or less to reduce the front wheel auxiliary turning angle and the rear wheel turning angle. The fourth region is a region where the lateral acceleration Gy is large and the steering angular velocity γ ′ is fast, that is, a limit traveling region for the vehicle 15, and a steering wheel operation is busy. In the fourth region, the correction gain Xij is set to “1” or less to reduce the front wheel auxiliary turning angle and the rear wheel turning angle.

  FIG. 5 shows an example of specific values of the correction gain Xij. In FIG. 5, the correction gain Xij is decreased as the steering angular velocity γ ′ and the lateral acceleration Gy increase. That is, when the load L (γ ′, Gy) obtained from the steering angular velocity γ ′ and the lateral acceleration Gy is higher than the threshold L1, the higher the steering angular velocity γ ′, the higher the driving frequency, and the front wheel steering actuator 7 and the rear wheel rotation. It is determined that the load on the rudder actuator 10 is high, and as the lateral acceleration Gy increases, the road surface reaction force increases, and it is determined that the load on the front wheel steering actuator 7 and the rear wheel steering actuator 10 is high. Use a small value for Xij.

… (17)

… (18) (Output correction unit)
The output correction unit 12c corrects the target front wheel turning angle θc and the target rear wheel turning angle δ * according to the steering angular velocity γ ′ and the lateral acceleration Gy, and the corrected target front wheel turning angle θc * and the corrected target. The rear wheel turning angle δc * is obtained. The corrected target front wheel turning angle θc * and the corrected target rear wheel turning angle Δc * are calculated using the following equations (17) and (18).

… (17)

… (18)

  Here, θ (γ) represents the turning angle of the front wheels 4 given by the steering of the steering wheel 2. The target front wheel turning angle θ * is the difference between the turning angle θ (γ) of the front wheel 4 given by steering the handle 2 and the front wheel auxiliary turning angle of the front wheel 4 given by driving the front wheel turning actuator 7. It is the sum. Since it is only necessary to apply the correction gain Xij to the front wheel auxiliary turning angle, in equation (17), the difference between the target front wheel turning angle θ * and the turning angle θ (γ) is corrected by applying the correction gain Xij. The rear target front wheel turning angle θc * is obtained. Further, since the rear wheel 8 is steered only by the rear wheel steering actuator 10, the steering angle δ of the rear wheel 8 is the same as the rear wheel steering angle, and the correction gain Xij is set for the target rear wheel steering angle δ *. To obtain the corrected target rear wheel turning angle δc *.

(Rear wheel steering actuator control unit)
In the rear wheel steering actuator control unit 12e, the corrected target rear wheel steering angle δc * and the steering angle δ of the rear wheel 8 by the rear wheel steering actuator 10 are input and detected by a rear wheel steering angle sensor (not shown). A command current Ir * for driving the rear wheel turning actuator 10 is calculated so that the turning angle δ of the rear wheel 8 becomes the corrected target rear wheel turning angle δc *.

(Front wheel steering actuator control unit)
The front wheel turning actuator control unit 11 inputs the corrected target front wheel turning angle θc * and the turning angle θ of the front wheel 4 detected by a front wheel turning angle sensor (not shown), and the turning angle θ is corrected. A command current If * for driving the front wheel steering actuator 7 is calculated so as to achieve the target front wheel steering angle θc *. Specifically, as described above, the target front wheel turning angle θ * is determined by the steering angle θ (γ) of the front wheel 4 given by steering the steering wheel 2 at the steering angle γ, and the front wheel turning actuator 7. Since this is the sum of the front wheel auxiliary turning angle of the front wheel 4 given by driving, when the driver steers the steering wheel 2 at the steering angle γ, the steering angle ratio variable mechanism 20 steers the steering wheel 2 at the steering angle γ. The pinion shaft 6b is rotated at a rotation angle obtained by adding the front wheel auxiliary turning angle to the turning angle θ (γ) given by the above. That is, when the steering angle ratio is not changed by the steering angle ratio variable mechanism 20, when the steering wheel 2 is steered at the steering angle γ, the turning angle of the pinion shaft 6b becomes the turning angle θ (γ), and the steering angle ratio is 1. However, the front wheel auxiliary turning angle is added to the turning angle θ (γ) by the steering angle ratio variable mechanism 20 (added if the front wheel auxiliary turning angle is a positive value, subtracted if the front wheel auxiliary turning angle is a negative value) ) Will change the rudder angle ratio.

(Power steering control unit)
The power steering actuator control unit 17 calculates a target auxiliary torque T * for assisting the driver's steering torque according to the vehicle speed V, and command current It * for driving the power steering actuator 18 according to the target auxiliary torque T *. Is calculated.

[Action]
The vehicle steering apparatus 1 according to the first embodiment adds and subtracts the steering angle ratio, which is the ratio of the steering angle of the front wheels 4 with respect to the steering angle of the handle 2, by adding and subtracting the front wheel auxiliary steering angle by the front wheel steering actuator 7. Can be variable. When the front wheel steering actuator 7 stops driving due to overheating or the like, the steering angle ratio changes from variable to fixed before and after the driving stops, so that the vehicle behavior with respect to steering of the steering wheel changes greatly, which may give the driver a sense of incongruity. It was.

  Therefore, in the vehicle steering apparatus 1 according to the first embodiment, the steering angular velocity γ ′ obtained from the steering angle γ detected by the steering angle sensor 3 and the load L (γ ′, Gy obtained from the lateral acceleration Gy detected by the lateral acceleration sensor 16. ) Is higher than the threshold value L1, the front wheel auxiliary turning angle to be added / subtracted by the front wheel turning actuator 7 is reduced when the state continues for a set time or longer.

  That is, by reducing the front wheel auxiliary turning angle, it is possible to suppress the heat generation of the front wheel turning actuator 7 and make it difficult to stop driving the front wheel turning actuator 7. Therefore, compared with the case where the driving of the front wheel steering actuator 7 is stopped after the front wheel steering actuator 7 is overheated, the change in the vehicle behavior can be reduced, and the uncomfortable feeling given to the driver can be suppressed. .

  In the vehicle steering apparatus 1 according to the first embodiment, a load acting on the front wheel steering actuator 7 is detected from the steering angular velocity γ ′ and the lateral acceleration Gy. The heat generation amount and current value of the actuator are parameters that change as a result of the load acting on the actuator, and do not indicate the load acting directly on the actuator. Therefore, the amount of heat generated by the actuator and the current value are delayed with respect to the load acting on the actuator.

  In particular, in the case where it is difficult to stop driving the front wheel steering actuator 7 as in the first embodiment, the parameter change is slow with the amount of heat generated by the actuator and the current value. Considering this, it is also conceivable to set the threshold value of the heat generation amount or current value of the actuator low. However, if the load decreases after the heat generation amount or current value of the actuator exceeds a low threshold, the front wheel auxiliary turning angle will be reduced unnecessarily, resulting in frequent changes in vehicle behavior. It becomes. In the first embodiment, the load acting on the front wheel steering actuator 7 is detected from the steering angular velocity γ ′ and the lateral acceleration Gy, so that the timing for reducing the front wheel auxiliary steering angle is not delayed and the front wheel auxiliary steering is performed. It is possible to suppress frequent occurrence of control for reducing the angle.

  Further, in the vehicle steering apparatus 1 according to the first embodiment, the steering angular velocity γ ′ obtained from the steering angle γ ′ detected by the steering angle sensor 3 and the load L (γ ′, When the state where Gy) is higher than the threshold value L1 continues for the set time or longer, the rear wheel turning angle added by the rear wheel turning actuator 10 is made smaller.

  That is, by reducing the rear wheel turning angle, it is possible to suppress the heat generation of the rear wheel turning actuator 10 and make it difficult to stop driving the rear wheel turning actuator 10. Therefore, the change in the vehicle behavior can be made smaller than when the rear wheel steering actuator 10 is stopped driving, and the uncomfortable feeling given to the driver can be suppressed.

Further, in the vehicle steering apparatus 1 according to the first embodiment, when the load load L (γ ′, Gy) is higher than the threshold value L1 continues for the set time or longer, the front wheel auxiliary turning angle and the rear wheel are increased as the load increases. The wheel auxiliary rudder angle was corrected to be small.
That is, when the load is relatively low, by reducing the correction amount of the front wheel auxiliary steering angle and the rear wheel auxiliary steering angle, it is possible to reduce the change in vehicle behavior and suppress the driver's uncomfortable feeling. On the other hand, when the load is relatively high, it is possible to make it difficult to stop driving the front wheel steering actuator 7 and the rear wheel steering actuator 10 by increasing the correction amounts of the front wheel auxiliary steering angle and the rear wheel auxiliary steering angle.

〔effect〕
Next, effects of the vehicle steering apparatus 1 of the first embodiment are listed below.

  (1) A steering angle ratio variable mechanism 20 that changes a steering angle ratio that is a ratio between the steering angle γ of the handle 2 and the steering angle θ of the front wheels 4 that are steered in accordance with the steering of the handle 2, and the steering angle A front wheel steering actuator 7 that drives the variable ratio mechanism 20, a four-wheel active steering control unit 12 that controls the front wheel steering actuator 7 to control the steering angle ratio, and a lateral acceleration sensor that detects the lateral acceleration of the vehicle 15. 16, the steering angle sensor 3 for detecting the steering angle γ of the steering wheel 2, and the higher the lateral acceleration detected by the lateral acceleration sensor 16 and the higher the speed of the steering angle γ detected by the steering angle sensor 3, A four-wheel active steering control unit 12 is provided in the traveling state determination unit 12d. The traveling state determination unit 12d calculates a load L (γ ′, Gy) acting on the rudder actuator 7 to be high. When the calculated load L (γ ′, Gy) is higher than a predetermined threshold value for a set time or longer, the front wheel steering actuator 7 is controlled so that the steering angle ratio approaches 1 I made it.

  Therefore, by reducing the steering angle ratio, it is possible to suppress the heat generation of the front wheel steering actuator 7 and make it difficult to stop driving the front wheel steering actuator 7. Therefore, the change in the vehicle behavior can be made smaller than when the front wheel steering actuator 7 is stopped driving, and the uncomfortable feeling given to the driver can be suppressed.

  (2) The rudder angle ratio variable mechanism 20 varies the rudder angle ratio by adjusting the front wheel auxiliary turning angle with respect to the turning angle θ of the front wheel 4 corresponding to the steering angle γ of the steering wheel 2 to activate the four wheel active. When the load L (γ ′, Gy) calculated by the traveling state determination unit 12d is higher than the threshold value continues for a set time or longer, the steering control unit 12 adjusts the front wheel auxiliary rotation that is adjusted by the steering angle ratio variable mechanism 20. By controlling the front wheel steering actuator 7 so that the rudder angle becomes smaller, the rudder angle ratio is made closer to 1.

  Therefore, by reducing the front wheel auxiliary turning angle, it is possible to suppress the heat generation of the front wheel turning actuator 7 and make it difficult to stop driving the front wheel turning actuator 7. Therefore, the change in the vehicle behavior can be made smaller than when the front wheel steering actuator 7 is stopped driving, and the uncomfortable feeling given to the driver can be suppressed.

  (3) The steering angle sensor 3 and the vehicle speed sensor 14 for detecting the vehicle behavior are provided, and the four-wheel active steering control unit 12 includes the vehicle behavior (steering angle γ, vehicle speed V) detected by the steering angle sensor 3 and the vehicle speed sensor 14. The target value generation unit 12a, the target output generation unit 12b that calculates the target front wheel turning angle based on the above, and the state in which L (γ ′, Gy) calculated in the traveling state determination unit 12d is higher than the threshold value is set time When the operation is continued, the target value generation unit 12a and the output correction unit 12c for correcting the target front wheel turning angle calculated by the target output generation unit 12b are provided so that the steering angle ratio approaches 1, and the output correction unit 12c corrects the steering angle ratio. The front wheel steering actuator 7 is controlled based on the corrected target front wheel steering angle θc *.

  Therefore, by reducing the front wheel auxiliary turning angle, it is possible to suppress the heat generation of the front wheel turning actuator 7 and make it difficult to stop driving the front wheel turning actuator 7. Therefore, the change in the vehicle behavior can be made smaller than when the front wheel steering actuator 7 is stopped driving, and the uncomfortable feeling given to the driver can be suppressed.

  (4) Target rear wheel steering according to the vehicle behavior (steering angle γ, vehicle speed V) detected by the rear wheel steering actuator 10 that gives the rear wheel steering angle δ to the rear wheel 8, the steering angle sensor 3, and the vehicle speed sensor 14. When a state in which L (γ ′, Gy) detected by the target value generation unit 12a, the target output generation unit 12b, and the traveling state determination unit 12d for calculating the angle is higher than a threshold value continues for a set time or longer, the rear wheel An output correction unit 12c that corrects the target rear wheel turning angle to obtain a corrected target rear wheel turning angle so as to reduce the steering angle, and a correction in which the turning angle δ of the rear wheel 8 is corrected by the output correction unit 12c. A rear wheel turning actuator control unit 12e for controlling the rear wheel turning actuator 10 so as to be the rear target rear wheel turning angle is provided.

  Therefore, by reducing the rear wheel turning angle δ, it is possible to suppress the heat generation of the rear wheel turning actuator 10 and make it difficult to stop the driving of the rear wheel turning actuator 10. Therefore, the change in the vehicle behavior can be made smaller than when the rear wheel steering actuator 10 is stopped driving, and the uncomfortable feeling given to the driver can be suppressed.

(5) The four-wheel active steering control unit 12 determines that the load L (γ ′, Gy) when the load L (γ ′, Gy) detected by the traveling state determination unit 12d is higher than the threshold value continues for a set time or longer. The front wheel steering actuator 7 is controlled so that the steering angle ratio approaches 1 as Gy) increases.
Therefore, when the load L (γ ′, Gy) is relatively low, by reducing the correction amount of the front wheel auxiliary turning angle, it is possible to reduce the change in vehicle behavior and suppress a sense of discomfort to the driver. On the other hand, when the load L (γ ′, Gy) is relatively high, the front wheel steering actuator 7 can be made difficult to stop driving by increasing the correction amount of the front wheel auxiliary turning angle.

(6) When the load L (γ ′, Gy) detected by the traveling state determination unit 12d continues to be higher than the threshold value L1 for the set time or longer, the output correction unit 12c loads L (γ ′, Gy). The corrected target rear wheel turning angle δc * is obtained by correcting the target rear wheel turning angle δ * so as to decrease the rear wheel turning angle as the value increases.
Therefore, when the load L (γ ′, Gy) is relatively low, by reducing the correction amount of the rear wheel turning angle, it is possible to reduce the change in vehicle behavior and suppress the driver's uncomfortable feeling. On the other hand, when the load L (γ ′, Gy) is relatively high, the rear wheel turning actuator 10 can be made difficult to stop driving by increasing the correction amount of the rear wheel turning angle.

[Example 2]
In the first embodiment, the load L (γ ′, Gy) is obtained from the steering angular velocity γ ′ and the lateral acceleration Gy. The second embodiment is different from the first embodiment in that the load L (Gy) is obtained from the lateral acceleration Gy. The second embodiment is different from the first embodiment in the configuration of the traveling state determination unit.

[Control block]
FIG. 2 is a control block diagram of the vehicle steering apparatus 1.
The four-wheel active steering control unit 12 includes a target value generation unit 12a, a target output generation unit 12b, an output correction unit 12c, a traveling state determination unit 12d, and a rear wheel steering actuator control unit 12e.

(Running state determination unit)
The traveling state determination unit 12d calculates a load L (Gy) acting on the front wheel steering actuator 7 and the rear wheel steering actuator 10. The load L (Gy) acting on the front wheel steering actuator 7 and the rear wheel steering actuator 10 is obtained from the lateral acceleration Gy, and is calculated to be higher as the lateral acceleration Gy is larger. Then, a correction gain Xij is obtained according to the calculated load L (Gy). The correction gain Xij is set such that the value of the correction gain Xij decreases as the load L (Gy) increases when the load L (Gy) is higher than the threshold value L1 for a set time or longer.

  The correction gain Xij is obtained using a map. FIG. 6 is a schematic diagram showing a range in which the correction gain Xij is set to be small. As shown in FIG. 6, it can be divided into four regions according to the lateral acceleration Gy and the steering angular velocity γ ′. The first region is a region where the lateral acceleration Gy is small and the steering angular velocity γ ′ is slow, that is, a normal traveling region for the vehicle 15, and a steering wheel operation is performed slowly. In this first region, the correction gain Xij is set to “1” so that the front wheel auxiliary turning angle and the rear wheel turning angle are not reduced. The second region is a region where the lateral acceleration Gy is large and the steering angular velocity γ ′ is slow, that is, a limit traveling region for the vehicle 15 and a steering operation is performed slowly. In this second region, the correction gain Xij is set to “1” or less to reduce the front wheel auxiliary turning angle and the rear wheel turning angle.

  The third region is a region where the lateral acceleration Gy is small and the steering angular velocity γ ′ is fast, that is, a normal traveling region for the vehicle 15, and a steering wheel operation is busy. In the third region, the correction gain Xij is set to “1” so that the front wheel auxiliary turning angle and the rear wheel turning angle are not reduced. The fourth region is a region where the lateral acceleration Gy is large and the steering angular velocity γ ′ is fast, that is, a limit traveling region for the vehicle 15, and a steering wheel operation is busy. In the fourth region, the correction gain Xij is set to “1” or less to reduce the front wheel auxiliary turning angle and the rear wheel turning angle.

  FIG. 7 is a diagram showing an example of specific numerical values of the correction gain Xij. In FIG. 7, the correction gain Xij is decreased as the lateral acceleration Gy increases. That is, when the load L (Gy) obtained from the lateral acceleration Gy is higher than the threshold value L1, the road surface reaction force increases as the lateral acceleration Gy increases, and the loads on the front wheel steering actuator 7 and the rear wheel steering actuator 10 increase. A small value is used as the correction gain Xij by determining that it is in the state.

[Action]
The vehicle steering apparatus 1 according to the second embodiment makes the steering angle ratio, which is the ratio of the steering angle of the front wheels 4 to the steering angle of the steering wheel 2, variable by adding and subtracting the steering angle by the front wheel steering actuator 7. can do. When the front wheel steering actuator 7 stops driving due to heat generation or the like, the steering angle ratio changes from variable to fixed before and after the driving stops, so that the vehicle behavior with respect to steering of the steering wheel changes greatly, which may cause the driver to feel uncomfortable. It was.

  Therefore, in the vehicle steering apparatus 1 according to the second embodiment, when the load L (Gy) obtained from the lateral acceleration Gy detected by the lateral acceleration sensor 16 is higher than the threshold value L1, the front wheel steering is performed. The front wheel auxiliary turning angle to be added / subtracted by the actuator 7 is reduced.

  That is, by reducing the front wheel auxiliary turning angle, it is possible to suppress the heat generation of the front wheel turning actuator 7 and make it difficult to stop driving the front wheel turning actuator 7. Therefore, the change in the vehicle behavior can be made smaller than when the front wheel steering actuator 7 is stopped driving, and the uncomfortable feeling given to the driver can be suppressed.

〔effect〕
Next, effects of the vehicle steering apparatus 1 according to the second embodiment will be listed below.

  (7) Steering angle ratio variable mechanism 20 that varies the steering angle ratio, which is the ratio between the steering angle γ of the handle 2 and the steering angle θ of the front wheels 4 that are steered in accordance with the steering of the handle 2, and the steering angle A front wheel steering actuator 7 that drives the variable ratio mechanism 20, a four-wheel active steering control unit 12 that controls the front wheel steering actuator 7 to control the steering angle ratio, and a lateral acceleration that detects the lateral acceleration Gy of the vehicle 15. A four-wheel active steer control including a sensor 16 and a traveling state determination unit 12d that calculates a load L (Gy) acting on the front wheel steering actuator 7 as the lateral acceleration Gy detected by the lateral acceleration sensor 16 increases. The unit 12 brings the rudder angle ratio closer to 1 when the load calculated by the traveling state determination unit 12d is higher than a predetermined threshold value L1 for a set time or longer. Thus, the front wheel steering actuator 7 is controlled.

  Therefore, by reducing the steering angle ratio, it is possible to suppress the heat generation of the front wheel steering actuator 7 and make it difficult to stop driving the front wheel steering actuator 7. Therefore, the change in the vehicle behavior can be made smaller than when the front wheel steering actuator 7 is stopped driving, and the uncomfortable feeling given to the driver can be suppressed.

  (8) In the vehicle 15, the steering angle ratio variable mechanism 20 that varies the steering angle ratio, which is the ratio of the steering angle γ of the steering wheel 2 and the steering angle θ of the front wheels 4 that are steered with the steering of the steering wheel 2; , The front wheel steering actuator 7 that drives the steering angle ratio variable mechanism 20, the four-wheel active steering control unit 12 that controls the front wheel steering actuator 7 to control the steering angle ratio, and the lateral acceleration Gy of the vehicle 15. A lateral acceleration sensor 16 to be detected, and a traveling state determination unit 12d that calculates a higher load L (Gy) acting on the front wheel steering actuator 7 as the lateral acceleration Gy detected by the lateral acceleration sensor 16 increases. The wheel active steering control unit 12 controls the rudder when the load calculated by the running state determination unit 12d is higher than a predetermined threshold value L1 for a set time or longer. And to control the wheel turning actuator 7 so as to approach a ratio to 1.

  Therefore, by reducing the steering angle ratio, it is possible to suppress the heat generation of the front wheel steering actuator 7 and make it difficult to stop driving the front wheel steering actuator 7. Therefore, the change in the vehicle behavior can be made smaller than when the front wheel steering actuator 7 is stopped driving, and the uncomfortable feeling given to the driver can be suppressed.

[Example 3]
In the first embodiment, the load L (γ ′, Gy) is obtained from the steering angular velocity γ ′ and the lateral acceleration Gy. The third embodiment is different from the first embodiment in that the load L (γ ′) is obtained from the steering angular velocity γ ′. The third embodiment is different from the first embodiment in the configuration of the traveling state determination unit.

[Control block]
FIG. 2 is a control block diagram of the vehicle steering apparatus 1.
The four-wheel active steering control unit 12 includes a target value generation unit 12a, a target output generation unit 12b, an output correction unit 12c, a traveling state determination unit 12d, and a rear wheel steering actuator control unit 12e.

(Running state determination unit)
In the traveling state determination unit 12d, a load L (γ ′) acting on the front wheel steering actuator 7 and the rear wheel steering actuator 10 is calculated. The load L (γ ′) acting on the front wheel steering actuator 7 and the rear wheel steering actuator 10 is obtained from the steering angular velocity γ ′, and is calculated to be higher as the steering angular velocity γ ′ increases. Then, a correction gain Xij is obtained according to the calculated load L (γ ′). The correction gain Xij is set such that the value of the correction gain Xij decreases as the load L (γ ′) increases when the load L (γ ′) is higher than the threshold value L1 for a set time or longer. .

  The correction gain Xij is obtained using a map. FIG. 8 is a schematic diagram showing a range in which the correction gain Xij is set to be small. As shown in FIG. 8, it can be divided into four regions according to the lateral acceleration Gy and the steering angular velocity γ ′. The first region is a region where the lateral acceleration Gy is small and the steering angular velocity γ ′ is slow, that is, a normal traveling region for the vehicle 15, and a steering wheel operation is performed slowly. In this first region, the correction gain Xij is set to “1” so that the front wheel auxiliary turning angle and the rear wheel turning angle are not reduced. The second region is a region where the lateral acceleration Gy is large and the steering angular velocity γ ′ is slow, that is, a limit traveling region for the vehicle 15 and a steering operation is performed slowly. In this second region, the correction gain Xij is set to “1” so that the front wheel auxiliary turning angle and the rear wheel turning angle are not reduced.

  The third region is a region where the lateral acceleration Gy is small and the steering angular velocity γ ′ is fast, that is, a normal traveling region for the vehicle 15, and a steering wheel operation is busy. In the third region, the correction gain Xij is set to “1” or less to reduce the front wheel auxiliary turning angle and the rear wheel turning angle. The fourth region is a region where the lateral acceleration Gy is large and the steering angular velocity γ ′ is fast, that is, a limit traveling region for the vehicle 15, and a steering wheel operation is busy. In the fourth region, the correction gain Xij is set to “1” or less to reduce the front wheel auxiliary turning angle and the rear wheel turning angle.

  FIG. 9 is a diagram showing an example of specific numerical values of the correction gain Xij. In FIG. 9, the correction gain Xij is decreased as the steering angular velocity γ ′ increases. That is, when the load L (γ ′) obtained from the steering angular velocity γ ′ is higher than the threshold value L1, the higher the steering angular velocity γ ′, the higher the driving frequency and the loads on the front wheel steering actuator 7 and the rear wheel steering actuator 10. It is determined that the state is high, and a small value is used as the correction gain Xij.

[Action]
The vehicle steering apparatus 1 according to the third embodiment variably changes the steering angle ratio, which is the ratio of the steering angle of the front wheels 4 to the steering angle of the steering wheel 2, by adding and subtracting the steering angle by the front wheel steering actuator 7. can do. When the front wheel steering actuator 7 stops driving due to heat generation or the like, the steering angle ratio changes from variable to fixed before and after the driving stops, so that the vehicle behavior with respect to steering of the steering wheel changes greatly, which may cause the driver to feel uncomfortable. It was.

  Therefore, in the vehicle steering apparatus 1 according to the third embodiment, there is a state in which the load L (γ ′) calculated according to the steering angular velocity γ ′ obtained from the steering angle γ detected by the steering angle sensor 3 is higher than the threshold value L1. When continuing for more than the set time, the front wheel auxiliary turning angle added or subtracted by the front wheel turning actuator 7 is reduced.

  That is, by reducing the front wheel auxiliary turning angle, it is possible to suppress the heat generation of the front wheel turning actuator 7 and make it difficult to stop driving the front wheel turning actuator 7. Therefore, the change in the vehicle behavior can be made smaller than when the front wheel steering actuator 7 is stopped driving, and the uncomfortable feeling given to the driver can be suppressed.

〔effect〕
Next, effects of the vehicle steering apparatus 1 according to the third embodiment will be listed below.

  (9) The front wheel steering actuator 7 that drives the steering angle ratio variable mechanism 20 that changes the steering angle ratio, which is the ratio of the steering angle γ of the handle 2 and the steering angle θ of the front wheels 4, and the steering actuator 7 are controlled. Thus, the faster the four-wheel active steering control unit 12 that controls the steering angle ratio, the steering angle sensor 3 that detects the steering angle γ of the steering wheel 2, and the faster the speed γ ′ of the steering angle γ detected by the steering angle sensor 3. And a traveling state determination unit 12d that calculates a load L (γ ′) acting on the front wheel steering actuator 7 to be high, the four-wheel active steering control unit 12 has a calculated load L (γ ′) determined in advance. When the state higher than the predetermined threshold L1 continues for a set time or longer, the front wheel steering actuator 7 is controlled so that the steering angle ratio approaches 1.

  Therefore, by reducing the steering angle ratio, it is possible to suppress the heat generation of the front wheel steering actuator 7 and make it difficult to stop driving the front wheel steering actuator 7. Therefore, the change in the vehicle behavior can be made smaller than when the front wheel steering actuator 7 is stopped driving, and the uncomfortable feeling given to the driver can be suppressed.

  (10) In the vehicle 15, the front wheel steering actuator 7 that drives the steering angle ratio variable mechanism 20 that changes the steering angle ratio that is the ratio of the steering angle γ of the steering wheel 2 and the steering angle θ of the front wheels 4, and steering A four-wheel active steering control unit 12 that controls the steering angle ratio by controlling the actuator 7, a steering angle sensor 3 that detects the steering angle γ of the steering wheel 2, and a speed γ of the steering angle γ detected by the steering angle sensor 3. And the traveling state determination unit 12d that calculates the load L (γ ′) acting on the front wheel steering actuator 7 as the speed increases, the four-wheel active steering control unit 12 has the calculated load L (γ ′) When a state higher than a predetermined threshold value L1 continues for a set time or longer, the front wheel steering actuator 7 is controlled so that the steering angle ratio approaches 1.

  Therefore, by reducing the front wheel auxiliary turning angle, it is possible to suppress the heat generation of the front wheel turning actuator 7 and make it difficult to stop driving the front wheel turning actuator 7. Therefore, the change in the vehicle behavior can be made smaller than when the front wheel steering actuator 7 is stopped driving, and the uncomfortable feeling given to the driver can be suppressed.

[Other embodiments]
The best mode for carrying out the present invention has been described based on the first to third embodiments. However, the specific configuration of the present invention is not limited to the first to third embodiments. The present invention includes any design changes that do not depart from the spirit of the invention.

In the vehicle steering apparatus 1 according to the first embodiment, the correction gain Xij is obtained from a map, but may be obtained by calculation.
Further, the vehicle steering apparatus 1 according to the first embodiment is a four-wheel active steering system that makes the rudder angles of the front wheels 4 and the rear wheels 8 variable. However, the steering device 1 for the front wheels 4 may be made variable. .

  In the vehicle steering apparatus 1 according to the first embodiment, the lateral acceleration Gy is detected by the lateral acceleration sensor 16, but may be estimated from the steering angle γ and the vehicle speed V.

DESCRIPTION OF SYMBOLS 1 Vehicle steering device 2 Handle 3 Steering angle sensor (vehicle behavior detection means, steering angle detection means)
4 front wheel 7 front wheel steering actuator 8 rear wheel 10 rear wheel steering actuator 11 front wheel steering actuator control unit (front wheel actuator control means)
12 Four-wheel active steering control unit 12b Target output generator (target front wheel turning angle calculation means, target rear wheel turning angle calculation means)
12c Output correction unit (target front wheel turning angle correction means, target rear wheel turning angle correction means)
12d Traveling state determination unit (load detection means)
12e Rear wheel steering actuator control unit (rear wheel actuator control means)
14 Vehicle speed sensor (vehicle behavior detection means)
15 Vehicle 16 Lateral acceleration sensor (lateral acceleration detecting means)

Claims (10)

A steering angle ratio varying means for steering angle ratio variable is the ratio between the front wheel turning angle of steered with the steering angle and the steering of the handle of the handle,
A front wheel steering actuator that drives the steering angle ratio variable means;
A rear wheel steering actuator for imparting a rear wheel steering angle to the rear wheels;
A steering angle ratio control means for controlling the steering angle ratio by controlling the front wheel steering actuator;
A rear wheel turning actuator control means for controlling the rear wheel turning angle actuator to control the rear wheel turning angle;
Lateral acceleration detecting means for detecting the lateral acceleration of the vehicle;
Load calculating means for calculating a higher load acting on the front wheel steering actuator and the rear wheel turning actuator as the lateral acceleration detected by the lateral acceleration detecting means is larger;
With
The steering angle ratio control means, when the load operation the load computed in means is higher than a predetermined threshold a predetermined state continues set time or more, said the steering angle ratio as close to 1 A vehicle steering control apparatus that controls a front wheel steering actuator and controls the rear wheel steering actuator to reduce the rear wheel steering angle . A steering angle ratio varying means for steering angle ratio variable is the ratio between the front wheel turning angle of steered with the steering angle and the steering of the handle of the handle,
A front wheel steering actuator that drives the steering angle ratio variable means ;
A rear wheel steering actuator for imparting a rear wheel steering angle to the rear wheels;
A steering angle ratio control means for controlling the steering angle ratio by controlling the front wheel steering actuator;
A rear wheel turning actuator control means for controlling the rear wheel turning angle actuator to control the rear wheel turning angle;
Steering angle detection means for detecting the steering angle of the steering wheel;
Load calculating means for calculating a higher load acting on the front wheel steering actuator and the rear wheel steering actuator as the speed of the steering angle detected by the steering angle detection means is higher;
With
The steering angle ratio control means, when the load operation the load computed in means is higher than a predetermined threshold a predetermined state continues set time or more, said the steering angle ratio as close to 1 A vehicle steering control apparatus that controls a front wheel steering actuator and controls the rear wheel steering actuator to reduce the rear wheel steering angle . In the vehicle steering control device according to claim 1 or claim 2,
The steering angle ratio varying means, and varies the steering ratio by adjusting the front wheel auxiliary steering angle to the steering angle of the front wheels corresponding to the steering angle of the steering wheel,
The steering angle ratio control means, when the load calculated continues high state set time or more than the threshold value in the load calculating means, the front wheel auxiliary steering angle is small to moderate by the steering angle ratio varying means The vehicle steering control device is characterized in that the steering angle ratio is made close to 1 by controlling the front wheel steering actuator. In the vehicle steering control device according to claim 1 or claim 2,
Vehicle behavior detection means for detecting vehicle behavior is provided;
The steering angle ratio control means, the target front-wheel steering angle calculating means for calculating the target front wheel steering angle based on the vehicle behavior detected by said vehicle behavior detection means, the load is computed in said load calculating means target front wheel steering angle to correct the target front wheel steering angle calculated by the target front wheel steering angle calculating means and said steering angle ratio is closer to 1 when the state higher than the threshold continues for a set time or more A vehicle steering control device, comprising: a correction means, wherein the front wheel steering actuator is controlled based on the corrected target front wheel turning angle corrected by the target front wheel turning angle correction means. In the vehicle steering control device according to any one of claims 1 to 4,
Lateral acceleration detecting means for detecting the lateral acceleration of the vehicle;
Steering angle detection means for detecting the steering angle of the steering wheel;
Provided,
The load calculation means is configured such that the greater the lateral acceleration detected by the lateral acceleration detection means and the faster the steering angle detected by the steering angle detection means, the faster the front wheel steering actuator and the rear wheel steering actuator. A vehicle steering control device characterized by being a means for calculating a high load acting on the vehicle. An apparatus as claimed in any one of claims 1 to claim 5,
Vehicle behavior detection means for detecting vehicle behavior is provided;
The rear wheel steering actuator, a target rear wheel turning angle calculation means for calculating a target rear wheel steering angle based on the vehicle behavior detected by the vehicle behavior detection unit, the load was calculated in the load calculation means threshold target rear wheel steering to correct the target rear wheel turning angle calculated by the target rear wheel turning angle calculation means so as to reduce the pre-Symbol rear wheel turning angle when the is higher than the value state continues for a set time or more and a corner correction means, before Symbol target rear wheel steering angle correction means thus corrected vehicular steering control apparatus characterized by controlling the rear wheel steering actuator based on the target rear wheel turning angle corrected. The vehicle steering apparatus according to any one of claims 1 to 6 ,
Before Symbol steering angle ratio control means, said when the load computed in load operation means continues a state higher than the threshold value set time or more, the steering angle ratio the higher the load increases so as to approach to 1 A vehicle steering control device that controls the front wheel steering actuator. In the vehicle steering device according to claim 6,
The target rear wheel turning angle correcting means reduces the rear wheel turning angle as the load is higher when the load calculated by the load calculating means is higher than the threshold for a set time or longer. And correcting the target rear wheel turning angle to obtain the corrected target rear wheel turning angle. A steering angle ratio varying means for steering angle ratio variable is the ratio between the front wheel turning angle of steered with the steering angle and the steering of the handle of the handle,
A front wheel steering actuator that drives the steering angle ratio variable means;
A rear wheel steering actuator for imparting a rear wheel steering angle to the rear wheels;
A steering angle ratio control means for controlling the steering angle ratio by controlling the front wheel steering actuator;
A rear wheel turning actuator control means for controlling the rear wheel turning angle actuator to control the rear wheel turning angle;
Lateral acceleration detecting means for detecting the lateral acceleration of the vehicle;
Load calculating means for calculating a higher load acting on the front wheel steering actuator and the rear wheel turning actuator as the lateral acceleration detected by the lateral acceleration detecting means is larger;
With
The rudder angle ratio control unit is configured to reduce the rudder angle ratio so that the rudder angle ratio approaches 1 when the load calculated by the load calculation unit is higher than a predetermined threshold value for a set time or longer. A vehicle with a steering control device that controls a wheel steering actuator and controls the rear wheel steering actuator so as to reduce the rear wheel steering angle . A steering angle ratio varying means for steering angle ratio variable is the ratio between the front wheel turning angle of steered with the steering angle and the steering of the handle of the handle,
A front wheel steering actuator that drives the steering angle ratio variable means ;
A rear wheel steering actuator for imparting a rear wheel steering angle to the rear wheels;
A steering angle ratio control means for controlling the steering angle ratio by controlling the front wheel steering actuator;
A rear wheel turning actuator control means for controlling the rear wheel turning angle actuator to control the rear wheel turning angle;
Steering angle detection means for detecting the steering angle of the steering wheel;
Load calculating means for calculating a higher load acting on the front wheel steering actuator and the rear wheel steering actuator as the speed of the steering angle detected by the steering angle detection means is higher;
With
The steering angle ratio control means, when the load operation the load computed in means is higher than a predetermined threshold a predetermined state continues set time or more, said the steering angle ratio as close to 1 A vehicle with a vehicle steering control device , wherein the vehicle controls a front wheel steering actuator and controls the rear wheel steering actuator so as to reduce the rear wheel steering angle .

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