JP4811188B2 - Vehicle steering control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To optimize turning responsiveness of a vehicle felt by a driver even when a traveling road is a meandering traveling road by changing a phase of variation of a steering angle of a steering wheel relative to variation of a steering operation amount of the driver to an advancement side when width of the traveling road is small and a steering gear ratio is controlled to a large value. <P>SOLUTION: The steering controller for the vehicle has a turned angle variable device 14 as a steering gear ratio variable means; and an electronic control device 16 for controlling the steering gear ratio by controlling the turned angle variable device 14. When the width Wd of the traveling road detected by CCD cameras 58 and 60 is small, a proportional gain of the control of the steering gear ratio is increased as compared with the case where the width of the traveling road is large, and when the width of the traveling road is small, a differential gain of the control of the steering gear ratio is increased as compared with the case where the width of the traveling road is large. Thereby, the phase of variation of the steering angle of the steering wheel relative to the variation of the steering operation amount is advanced. <P>COPYRIGHT: (C)2008,JPO&amp;INPIT

Description

  The present invention relates to a vehicle steering control device, and more particularly to a vehicle steering control device that includes a steering gear ratio variable device and controls a steering gear ratio.

As one of steering control devices for vehicles such as automobiles, there are a steering gear ratio variable device, a control means for controlling the steering gear ratio by controlling the steering gear ratio variable device, and a means for detecting the traveling road width. When the vehicle width is small, the control means increases the steering gear ratio compared to when the vehicle road width is large, and thus the vehicle steering control device configured to improve the vehicle's narrow road driving performance has already been provided. For example, it is described in Patent Document 1 below.
JP 2004-306717 A

  In general, the turning response of the vehicle is delayed with respect to the driver's steering operation, and the speed of the driver's steering operation is limited. Therefore, when the steering gear ratio is large, the travel path meanders greatly. In a situation where the driver has to steer quickly, the driver tends to feel a delay in turning response of the vehicle and feels that the turning response of the vehicle has deteriorated. Therefore, in the conventional steering control device as described above that controls the steering gear ratio according to the travel path width, the travel path width is small in a situation where the vehicle travels on a narrow meandering road. Correspondingly, when the steering gear ratio is controlled to a large value, there is a problem that the driver feels that the turning responsiveness of the vehicle is lowered and it is difficult to perform the driving operation.

  In addition, in order to solve the above problem, if the steering gear ratio controlled according to the road width is set to a small value, the driver can turn the vehicle in a situation where the vehicle travels on a narrow road. It is felt that the vehicle is too high, and the narrow road traveling performance of the vehicle by controlling the steering gear ratio according to the traveling road width cannot be improved effectively.

  The present invention has been made in view of the above-described problems in the conventional steering control device that controls the steering gear ratio in accordance with the travel path width. The main problem of the present invention is that the travel path width is small. When the steering gear ratio is controlled to a large value, the phase of the change in the steering angle of the steered wheel with respect to the change of the steering operation amount of the driver is compared with the case where the traveling road width is large and the steering gear ratio is controlled to a small value. By changing to the advancing side, not only when the traveling path is a straight traveling path but also when the traveling path is a meandering traveling path, the turning response of the vehicle felt by the driver when traveling on a narrow road is optimized.

[Means for Solving the Problems and Effects of the Invention]
The main problems described above are the structure of claim 1, that is, the steering gear ratio variable means, the control means for controlling the steering gear ratio by controlling the steering gear ratio variable means, and the means for detecting the travel path width. In the vehicle steering control device in which the control means increases the steering gear ratio when the travel path width is small compared to when the travel path width is large. This is achieved by a vehicle steering control device characterized in that the differential gain of the steering transmission ratio is increased as compared with when the travel path width is large.

  According to the first aspect of the present invention, when the travel path width is small, not only the steering gear ratio is increased but also the differential gain of the steering transmission ratio is increased compared to when the travel path width is large. When the driver performs a steering operation with a high steering speed in a situation where the vehicle travels on a narrow meandering road, the steerable wheels can be steered with high responsiveness. While the vehicle travels along a meandering road while ensuring a stable running of the vehicle when traveling substantially straight ahead on the road, the driver performs a driving operation because the turning response of the vehicle decreases. This makes it possible to prevent the driver from feeling that it has become difficult, and therefore optimizes the vehicle turning response felt by the driver when driving on narrow roads, not only when the road is a straight road but also when the road is a meandering road. can do.

  According to the present invention, in order to effectively achieve the main problems described above, in the configuration of claim 1, the control means can be used even if the travel path width varies as the vehicle travels. When the magnitude of the steering operation amount is equal to or greater than the straight travel determination reference value, the steering gear ratio and the differential gain are not changed based on the travel path width (configuration of claim 2).

  According to the configuration of the second aspect, the steering gear based on the road width is used when the magnitude of the steering operation amount of the driver is equal to or greater than the straight traveling determination reference value even if the road width varies as the vehicle travels. Since the ratio and the differential gain are not changed, in the situation where the steering operation is performed by the driver, the driver changes the steering gear ratio and the differential gain and the turning characteristic of the vehicle changes. It can be surely prevented from feeling uncomfortable.

  According to the present invention, in order to effectively achieve the main problems described above, in the configuration of claim 1 or 2, the control means determines whether or not the driver is performing a steering operation for changing the course. And determining that the driver is performing a steering operation for changing the course, the steering gear ratio is configured to be controlled to a value smaller than a value changed based on the travel path width ( Configuration of claim 3).

  According to the third aspect of the present invention, when it is determined that the driver is performing a steering operation for changing the course, at least the steering gear ratio is controlled to a value smaller than a value controlled based on the travel path width. Therefore, in the situation where the driver performs the steering operation for changing the course, it is possible to prevent the turning response of the vehicle from being insufficient due to the large steering gear ratio, and to easily and reliably change the course. Can be.

  Further, according to the present invention, in the configuration of the above-mentioned claim 3, when the change rate of the driver's steering operation amount is equal to or greater than the course change determination reference value, the control means It is configured to determine that the steering operation is being performed (configuration of claim 4).

  According to the fourth aspect of the present invention, when the change rate of the steering operation amount of the driver is equal to or greater than the course change determination reference value, it is determined that the driver is performing the course change steering operation. Therefore, when the driver is performing a steering operation for changing the course, it is possible to reliably determine that, and at least the steering gear ratio can be controlled to a value smaller than the value controlled based on the travel path width.

  According to the present invention, in order to effectively achieve the main problems described above, in the configuration of claim 1 or 2, the control means may cause the vehicle to collide with an obstacle in front of the vehicle. If it is determined that there is a possibility that the vehicle may collide with an obstacle in front of the vehicle, at least the steering gear ratio is controlled to a value smaller than a value changed based on the travel path width. (Structure of claim 5).

  According to the fifth aspect of the present invention, when it is determined that the vehicle may collide with an obstacle ahead of the vehicle, at least the steering gear ratio is set to a value smaller than a value changed based on the travel path width. Therefore, when the driver starts the steering operation for changing the course for avoiding the collision, it is possible to prevent the turning response of the vehicle from being insufficient due to the large steering gear ratio, and easily and It is possible to reliably change the course for avoiding a collision.

  According to the present invention, in the configuration according to any one of the first to fifth aspects, when the magnitude of the steering operation amount of the driver is small, the control means is when the magnitude of the steering operation amount of the driver is small. The steering gear ratio is configured to be controlled to a small value at least as compared with the above (structure of claim 6).

  According to the configuration of the sixth aspect, when the magnitude of the steering operation amount of the driver is large, at least the steering gear ratio is controlled to a value smaller than when the magnitude of the steering operation amount of the driver is small. Therefore, at least the steering gear ratio can be controlled in accordance with the driver's request for changing the course, and thus the turning response of the vehicle can be controlled in accordance with the driver's request for changing the course.

[Preferred embodiment of problem solving means]
According to one preferred aspect of the present invention, in the configuration according to any one of claims 1 to 6, the control means calculates a basic target steering gear ratio and a basic target differential gain based at least on the vehicle speed, and When the width is small, the correction coefficient for calculating the target steering gear ratio and the correction coefficient for calculating the target differential gain are larger than those when the road width is large. The differential gain calculation correction coefficient is calculated, the target steering gear ratio is calculated as the product of the basic target steering gear ratio and the target steering gear ratio calculation correction coefficient, and the basic target differential gain and the target differential gain calculation correction coefficient are calculated. By calculating the target differential gain as the product of Tearingugiya ratio and configured to increase the differential gain (preferred embodiments 1).

  According to another preferred aspect of the present invention, in the configuration of the preferred aspect 1, the control means calculates a target steering gear ratio calculation correction coefficient and a target differential gain calculation correction coefficient at predetermined time intervals. If the magnitude of the steering operation amount by the driver is equal to or greater than the straight-running determination reference value even if the travel path width changes as the vehicle travels, the target steering gear ratio calculation correction coefficient and the target differential gain calculation correction coefficient Is maintained at the previous value so that the steering gear ratio and the differential gain based on the travel path width are not changed (preferred aspect 2).

  According to one preferred aspect of the present invention, in the configuration according to any one of claims 1 to 6, the control means calculates a basic target steering gear ratio and a basic target differential gain based at least on the vehicle speed, and When the width is small, the first target steering gear ratio based on the travel path width is such that the first target steering gear ratio calculation correction coefficient and the target differential gain calculation correction coefficient are larger than when the travel path width is large. The calculation target correction coefficient and the target differential gain calculation correction coefficient are calculated, and the second target steering gear is greater when the driver's steering operation amount is larger than when the driver's steering operation amount is smaller. The second target steering gear ratio calculation correction coefficient is calculated based on the driver's steering operation amount so that the ratio calculation correction coefficient becomes small, and the basic target steering gear ratio is calculated. The target steering gear ratio is calculated as the product of the first target steering gear ratio calculation correction coefficient and the second target steering gear ratio calculation correction coefficient, and the basic target differential gain and the target differential gain calculation correction coefficient By calculating the target differential gain as the product, the steering gear ratio and the differential gain are increased when the traveling road width is small compared to when the traveling road width is large, and the steering of the driver is performed when the driver's steering operation amount is large. The steering gear ratio is configured to be smaller than when the operation amount is small (preferred aspect 3).

  According to another preferred aspect of the present invention, in the configuration of the preferred aspect 3 described above, the control means performs the first and second target steering gear ratio calculation correction coefficients and the target differential gain calculation every predetermined time. The first and second target steering gear ratios are calculated when the amount of steering operation by the driver is equal to or greater than the straight-running determination reference value even when the travel path width varies as the vehicle travels. By maintaining the calculation correction coefficient and the target differential gain calculation correction coefficient at the previous values, the steering gear ratio and the differential gain based on the travel path width are not changed (preferred aspect 4).

  According to another preferred aspect of the present invention, in the configuration of the preferred aspect 3 or 4, the control means performs the second target steering gear ratio calculation correction when the vehicle speed is low compared to when the vehicle speed is high. The second target steering gear ratio calculation correction coefficient is calculated based on the driver's steering operation amount and vehicle speed so that the coefficient becomes smaller (preferable aspect 5).

  According to another preferred aspect of the present invention, in any one of the preferred aspects 1 to 5, the control means sets the target steering gear ratio to the basic target steering when the traveling road width is equal to or larger than the reference value. The gear ratio is set and the target differential gain is set to the basic target differential gain (preferred aspect 6).

  According to another preferred aspect of the present invention, in any one of the third to fifth aspects or the preferred aspects 1 to 6, the control means determines the steering gear ratio and the differential gain based on the travel path width. It is configured to control to a value smaller than the value to be changed (preferred aspect 7).

  According to another preferred aspect of the present invention, in the structure according to claim 6 or any of preferred aspects 1 to 7, the control means is configured to control the steering gear ratio and the differential gain to a small value. (Preferred embodiment 8).

  According to another preferred aspect of the present invention, in any one of the first to sixth aspects or the preferred aspects 1 to 8, the vehicle has steering assist torque control means, and the control means is steering. When the differential gain of the gear ratio and the steering transmission ratio is increased, the steering assist torque generated by the steering assist torque control means is reduced (preferred aspect 9).

  The present invention will now be described in detail with reference to the accompanying drawings.

  FIG. 1 is a schematic configuration diagram showing one embodiment of a vehicle steering control device according to the present invention applied to a vehicle equipped with an electric power steering device.

  In FIG. 1, a steering control device 10 is mounted on a vehicle 12 and includes a turning angle varying device 14 and an electronic control device 16 that controls the turning angle varying device 14. In FIG. 1, 18FL and 18FR indicate left and right front wheels as steering wheels of the vehicle 12, and 18RL and 18RR indicate left and right rear wheels, respectively. The left and right front wheels 18FL and 18FR, which are the steering wheels, are driven via a rack bar 24 and tie rods 26L and 26R by a rack and pinion type electric power steering device 22 driven in response to an operation of the steering wheel 20 by a driver. Steered.

  The steering wheel 20 is drivingly connected to a pinion shaft 34 of the power steering device 22 through an upper steering shaft 28, a turning angle varying device 14, a lower steering shaft 30, and a universal joint 32. In the illustrated embodiment, the turning angle varying device 14 is connected to the lower end of the upper steering shaft 28 on the housing 14A side, and the auxiliary is connected to the upper end of the lower steering shaft 30 on the rotor 14B side. A motor 36 for turning driving is included.

  Thus, the turning angle varying device 14 rotationally drives the lower steering shaft 30 relative to the upper steering shaft 28, thereby driving the left and right front wheels 18 FL and 18 FR relative to the steering wheel 20 by auxiliary steering. It functions as a steering gear ratio variable means for increasing or decreasing the steering gear ratio, and is controlled by the steering angle control unit of the electronic control unit 16.

  If an abnormality in which the lower steering shaft 30 cannot be driven to rotate relative to the upper steering shaft 28 occurs in the turning angle varying device 14, a lock device not shown in FIG. The relative rotation of the housing 14A and the rotor 14B is mechanically prevented so that the relative rotation angle of the lower steering shaft 30 with respect to 28 does not change.

  In the illustrated embodiment, the electric power steering device 22 is a rack coaxial type electric power steering device, and converts the electric motor 38 and the rotational torque of the electric motor 38 into a force in the reciprocating direction of the rack bar 24. For example, a ball screw type conversion mechanism 40 is included. The electric power steering device 22 is controlled by an electric power steering device (EPS) control unit of the electronic control device 16, and generates an auxiliary steering force that drives the rack bar 24 relative to the housing 44. It functions as an auxiliary steering assist force generator that reduces the steering burden. The auxiliary steering assist force generator may have any configuration known in the art.

  In the illustrated embodiment, the upper steering shaft 28 is provided with a steering angle sensor 50 for detecting the rotation angle of the upper steering shaft as the steering angle θ and a steering torque sensor 52 for detecting the steering torque Ts. Signals indicating the steering angle θ and the steering torque Ts are input to the electronic control unit 16. The electronic control unit 16 detects the relative rotation angle θre of the turning angle varying device 14 detected by the rotation angle sensor 54, that is, a signal indicating the relative rotation angle of the lower steering shaft 30 with respect to the upper steering shaft 28, and is detected by the vehicle speed sensor 56. A signal indicating the vehicle speed V is input.

  Also, CCD cameras 58 and 60 for photographing the front of the vehicle are provided at the front end of the vehicle 12, and a signal indicating image information ahead of the vehicle photographed by the CCD cameras 58 and 60 is input to the electronic control device 16. Is done. The electronic control unit 16 calculates the traveling road width Wd as a range in which the own vehicle can move laterally in the traveling road using the parallax based on the image information in front of the vehicle input from the CCD cameras 58 and 60. To do. For example, the traveling road width Wd is the width of the entire plurality of lanes when the traveling road is a multi-lane road, and the width of the single lane when the traveling road is a one-lane, one-lane driving road. If the road is a road without a central separation line, it is the road width.

  Further, a radar sensor 62 is provided at the front end of the vehicle 12, and the radar sensor 62 is a millimeter wave radar that radiates a millimeter wave as a detection wave to the front of the vehicle, for example, an obstacle such as a vehicle ahead or a road sign. The relative distance Lre and the relative speed Vre between the obstacle and the vehicle 12 are detected, and the detected values are sent as signals to the electronic control unit 16. The electronic control unit 16 determines whether there is an obstacle ahead of the traveling direction of the vehicle 12 based on signals from the radar sensor 62 and the CCD cameras 58 and 60.

  When it is determined that there is an obstacle ahead of the vehicle, the electronic control unit 16 determines whether the vehicle 12 may collide with the obstacle, for example, by dividing the relative distance Lre by the relative speed Vre. When it is determined that the vehicle 12 may collide with an obstacle, the vehicle is automatically decelerated by outputting a command signal to a braking / driving force control device not shown in FIG.

  Each control unit of the electronic control device 16 may include a microcomputer having a CPU, a ROM, a RAM, and an input / output port device, which are connected to each other via a bidirectional common bus. Further, the steering angle sensor 50, the steering torque sensor 52, and the rotation angle sensor 54 detect the steering angle θ, the steering torque Ts, and the relative rotation angle θre, respectively, with the case of steering or turning in the left turning direction of the vehicle as positive.

  As will be described in detail later, the electronic control unit 16 has a basic target steering gain ratio Rsbt and a basic target differential gain of the steering transmission ratio for achieving a predetermined steering characteristic based on the vehicle speed V so that it increases as the vehicle speed V increases. Calculate Gdbt. Further, the electronic control unit 16 calculates the narrow road correction coefficient Ks for the target steering gear ratio and the narrow road correction coefficient Kd for the target differential gain based on the travel road width Wd so as to increase as the travel road width Wd decreases. . Further, the electronic control unit 16 calculates a correction coefficient Kn for the target steering gear ratio based on the absolute value of the steering angle θ so that the absolute value of the steering angle θ becomes smaller.

  The electronic control unit 16 calculates the target steering gear ratio Rst as the product of the basic target steering gear ratio Rsbt, the narrow path correction coefficient Ks, and the correction coefficient Kn, and calculates the basic target differential gain Gdbt and the narrow path correction coefficient Kd. The target differential gain Gdt is calculated as the product. Further, the electronic control unit 16 calculates the sum of the value obtained by dividing the steering angle θ by the target steering gear ratio Rst and the product of the target differential gain Gdt and the steering angular velocity θd as the target pinion angle θpt, and the target pinion angle θpt. The target relative rotation angle θret of the turning angle varying device 14 is calculated as a deviation between the steering angle θ and the steering angle varying device 14 so that the relative rotation angle θre of the turning angle varying device 14 becomes the target relative rotation angle θret. To control.

  Further, the electronic control unit 16 changes the traveling road width Wd as the vehicle travels, and the vehicle is in a turning state even when the narrow road correction coefficient Ks, the correction coefficient Kn, and the narrow road correction coefficient Kd should be changed. In some cases, the narrow road correction coefficient Ks, the correction coefficient Kn, and the narrow road correction coefficient Kd are not changed, thereby changing the target steering gear ratio Rst and the target differential gain Gdt of the steering transmission ratio in a situation where the vehicle is turning. This prevents the turning response of the vehicle from changing.

  Further, the electronic control unit 16 determines the target steering gear ratio Rst and the steering based on the travel path width Wd when there is a possibility that the vehicle 12 may collide with an obstacle ahead or when the driver is performing a steering operation for changing the lane. Without correcting the target differential gain Gdt of the transmission ratio or the target steering gear ratio Rst based on the absolute value of the steering angle θ, the target steering gear ratio Rst and the target differential gain Gdt of the steering transmission ratio are respectively set to the basic target steering gear ratio. Rsbt and the basic target differential gain Gdbt are set so that the driver can easily change the course or lane of the collision avoidance.

  Further, the electronic control device 16 calculates a target assist torque Ta for generating a steering assist force based on the steering torque Ts and the vehicle speed V, and controls the electric power steering device 22 so that the assist torque becomes the target assist torque Ta. This reduces the driver's steering burden. The electronic control unit 16 reduces the steering assist torque generated by the electric power steering device 22 when correcting the target steering gear ratio Rst and the target differential gain Gdt of the steering transmission ratio based on the travel path width Wd. As a result, the steering reaction force when the vehicle travels on the narrow road is relatively increased, so that the driver can easily drive the vehicle on the narrow road.

  Note that the basic target steering gear ratio Rsbt and basic target differential gain Gdbt are calculated. The steering assist force control itself does not form the gist of the present invention, and these controls may be executed in any manner known in the art.

  Next, the steering control of the vehicle in the illustrated embodiment will be described with reference to the flowcharts shown in FIGS. 2 is a flowchart showing a main routine of the steering control. FIG. 3 is a flowchart showing a calculation routine of the narrow path correction coefficients Ks and Kd in step 300 of the flowchart shown in FIG. 4 is a flowchart showing a steering assist torque control routine. The control according to the flowcharts shown in FIGS. 2 and 4 is started by closing an ignition switch (not shown) and is repeatedly executed at predetermined time intervals.

  In step 210 of the main routine of the steering control shown in FIG. 2, a signal indicating the steering angle θ is read, and in step 220, based on the vehicle speed V, the map shown in FIG. The basic target steering gear ratio Rsbt is calculated, and in step 230, the basic target differential gain Gdbt is calculated from the map shown in FIG.

  In step 300, a narrow road correction coefficient Ks and a correction coefficient Kn for the target steering gear ratio are calculated according to the flowchart shown in FIG. 3, and a narrow road correction coefficient Kd for the target differential gain is calculated. In step 510, the target steering gear ratio Rst is calculated as the product of the basic target steering gear ratio Rsbt, the narrow road correction coefficient Ks, and the correction coefficient Kn. In step 520, the basic target differential gain Gdbt is narrowed. The target differential gain Gdt is calculated as the product of the road correction coefficient Kd.

In step 530, the target pinion angle θpt is calculated according to the following equation 1 using the time differential value of the steering angle θ as the steering angular velocity θd, and the deviation between the target pinion angle θpt and the steering angle θ according to the following equation 2. The target relative rotation angle θret of the turning angle varying device 14 is calculated as follows. In step 540, the turning angle varying device 14 is set so that the relative rotation angle θre of the turning angle varying device 14 becomes the target relative rotation angle θret. By being controlled, the steering gear ratio is controlled.
θpt = θ / Rst + Gdt · θd (1)
θret = θpt−θ (2)

  In step 310 of the correction coefficient Ks, Kn, and Kd calculation routine shown in FIG. 3, it is determined whether or not the vehicle 12 may collide with an obstacle ahead of it, that is, the driver can A determination is made as to whether or not there is a possibility of performing a rapid course change steering operation for collision avoidance. When an affirmative determination is made, the process proceeds to step 370, and when a negative determination is made, the process proceeds to step 315. move on.

  In step 315, the reference value θds for the driver's sudden steering determination is calculated based on the vehicle speed V so that the vehicle speed V becomes higher, and the absolute value of the steering angular velocity θd is the reference for the driver's sudden steering determination. It is determined whether or not the value is greater than or equal to the value θds, that is, whether or not the driver wants to turn by sudden steering for avoiding danger or the like. If an affirmative determination is made, go to Step 370. If the determination is negative, the process proceeds to step 320.

  In step 320, a reference value Wdo for narrow road determination is calculated based on the vehicle speed V so as to increase as the vehicle speed V increases, and whether or not the traveling road width Wd is equal to or smaller than the reference value Wdo for narrow road determination. When a negative determination is made, the process proceeds to step 360. When an affirmative determination is made, the process proceeds to step 325.

  In step 325, it is determined whether or not the vehicle speed V is equal to or lower than a reference value Vo (positive constant) for determining low speed travel. If a negative determination is made, the process proceeds to step 360, where an affirmative determination is made. If so, go to Step 330.

  In step 330, it is determined whether or not the flag F is 0, that is, whether or not the narrow path correction has not been executed for the target steering gear ratio Rst and the target differential gain Gdt. That is, when it is determined that narrow path correction is being performed, the process proceeds to step 340, and when an affirmative determination is performed, the process proceeds to step 335.

  In step 335, it is determined whether or not the absolute value of the steering angle θ is equal to or less than a reference value θo (positive constant smaller than θs) for determining whether the vehicle is traveling straight, that is, the steering wheel 20 is substantially at the straight traveling position. If a negative determination is made, the flag F and the correction coefficients Ks, Kn, Kd remain unchanged at the previous values without changing, and the process proceeds to step 510, where an affirmative determination is made. If so, the flag F is set to 1 in step 340.

  In step 345, the narrow road correction coefficient Ks for the target steering gear ratio is calculated from the map shown in FIG. 7 based on the travel road width Wd. In step 350, the narrow road correction coefficient Ks is calculated based on the steering angle θ and the vehicle speed V. 8, the correction coefficient Kn for the target steering gear ratio is calculated. In step 355, the narrow path correction coefficient Kd for the target differential gain is calculated from the map shown in FIG. 9 based on the travel path width Wd. Is calculated, and then the routine proceeds to step 510.

  In step 360, it is determined whether or not the flag F is 1, that is, whether or not the narrow road correction is being performed for the target steering gear ratio Rst and the target differential gain Gdt. When it is determined that the narrow road correction has not been performed, the process proceeds to step 370. When the determination is positive, the process proceeds to step 365.

  In step 365, as in step 335, it is determined whether or not the absolute value of the steering angle θ is equal to or less than the reference value θo for determining whether the vehicle is going straight, and if a negative determination is made, a flag is set. F and correction coefficients Ks, Kn, and Kd are maintained unchanged at the previous values without proceeding to step 510. If an affirmative determination is made, flag F is reset to 0 at step 370, and step 375 is entered. Then, the narrow road correction coefficient Ks and the correction coefficient Kn for the target steering gear ratio and the narrow road correction coefficient Kd for the target differential gain are set to 1, respectively, and then the process proceeds to step 510.

  In step 410 of the steering assist torque control routine shown in FIG. 4, a signal indicating the steering torque Ts is read, and in step 420, the signal shown in FIG. 10 is shown based on the steering torque Ts. The basic assist torque Tab is calculated from the map corresponding to the graph, and in step 430, the vehicle speed coefficient Kv is calculated from the map corresponding to the graph shown in FIG.

  In step 440, it is determined whether or not the flag F is 1, that is, whether or not narrow path correction is being performed for the target steering gear ratio Rst and the target differential gain Gdt, and a negative determination is made. In step 450, the correction coefficient Kt is set to 1 in step 450, and then the process proceeds to step 470. If a positive determination is made, in step 460, the map shown in FIG. After the correction coefficient Kt is calculated, the process proceeds to step 470.

  In step 470, the target assist torque Ta is calculated as the product of the correction coefficient Kt, the vehicle speed coefficient Kv, and the basic assist torque Tab, and in step 480, a control signal corresponding to the target assist torque Ta is output to the motor 38. Thus, the assist torque is controlled so that the assist torque becomes the target assist torque Ta.

  Next, the control of the steering gear ratio and the steering assist torque in the embodiment configured as described above will be described in various cases.

(1) When the vehicle travels on a wide travel path When the vehicle travels on a wide travel path, there is no fear of the driver's steering operation, and the driver's steering operation speed is low, FIG. In steps 310 to 320 of the flowchart shown in FIG. 4, a negative determination is made, a negative determination is made in step 360, and a narrow road correction coefficient Ks and a correction coefficient for the target steering gear ratio are determined in step 375. The narrow path correction coefficient Kd for Kn and the target differential gain is set to 1, respectively.

  In addition, when the vehicle travels on a wide road and there is a possibility of the driver's steering operation or when the driver's steering operation speed is high, an affirmative determination is made in step 310 or 315. Also in this case, in step 375, the narrow road correction coefficient Ks and correction coefficient Kn for the target steering gear ratio and the narrow road correction coefficient Kd for the target differential gain are set to 1, respectively.

  Therefore, when the vehicle travels on a wide traveling road, the target steering gear ratio Rst is not corrected for increase regardless of whether or not the driver is performing a steering operation. The basic target steering gear ratio Rsbt is set to the same value, and the target differential gain Gdt is also set to the same value as the basic target differential gain Gdbt without being corrected for increase.

(2) When the vehicle travels substantially straight at a low speed on a narrow travel path In this case, a negative determination is made in steps 310 and 315, but an affirmative determination is made in steps 320 and 325. First, an affirmative determination is made in steps 330 and 335, whereby the flag F is set to 1 in step 340, and in step 345, the smaller the traveling road width Wd, the more about the target steering gear ratio. The narrow road correction coefficient Ks is calculated in accordance with the travel road width Wd so that the narrow road correction coefficient Ks is increased. In step 350, the absolute value of the steering angle θ is increased and is decreased as the vehicle speed V is increased. Accordingly, the correction coefficient Kn is calculated. In step 355, the travel path is set so that the narrow path correction coefficient Kd for the target differential gain increases as the travel path width Wd decreases. A narrow path correction coefficient Kd is calculated according to the width Wd.

  Further, once the flag F is set to 1, a negative determination is made in step 330, and in step 345 and 355 without making the determination in step 335, narrow road correction is performed according to the traveling road width Wd, respectively. The coefficients Ks and Kd are calculated, and in step 350, the correction coefficient Kn is calculated according to the absolute value of the steering angle θ and the vehicle speed V.

  When the narrow road correction coefficient Ks or the correction coefficient Kn is set to a large value, the target steering gear ratio Rst increases, and the ratio of the amount of change in the steering angle of the left and right front wheels with respect to the rotation angle of the steering wheel 20 decreases. The ratio of the amount of lateral movement of the vehicle with respect to the amount of steering operation by the driver is reduced, and the driver can easily drive the vehicle along a narrow travel path.

  In general, when the target steering gear ratio Rst is increased, the ratio of the turning movement amount in the lateral direction of the vehicle with respect to the driver's steering operation amount is reduced. Therefore, particularly in a situation where the travel path is meandering greatly. Therefore, it is necessary to steer quickly and greatly, so that the driver feels that the turning response of the vehicle has been lowered.

  According to the illustrated embodiment, when the vehicle travels in a straight line at a low speed on a narrow road and then turns or meanders, the vehicle travels on a narrow road at a low speed. Since the flag F is set to 1 when traveling straight, even if the vehicle subsequently turns or meanders, the narrow path correction coefficient Ks is set to a large value and the narrow path for the target differential gain is set. When the target steering gear ratio Rst increases, the target differential gain Gdt is also increased by this so that the correction coefficient Kd is increased. As a result, the phase of the change in the steering angle of the left and right front wheels with respect to the change in the rotation angle of the steering wheel 20 It is advanced. Therefore, it is possible to prevent the driver from feeling that the turning responsiveness of the vehicle has deteriorated in a situation where the vehicle travels on a largely meandering road after traveling straight ahead.

  When the target steering gear ratio Rst is corrected to increase, the target differential gain Gdt is also corrected to increase at the same time. However, when the vehicle is in a substantially straight traveling state, the driver performs a steering operation at a high steering speed. Therefore, even if the target differential gain Gdt is increased, the straight running stability of the vehicle on the narrow road is not deteriorated by this.

(3) When the vehicle is turning or meandering along a traveling path at a low speed on a narrow traveling path In this case, a negative determination is made in steps 310 and 315, and an affirmative is determined in steps 320 to 330. A determination is made, but a negative determination is made in step 335, the flag F is maintained at 0, and the narrow path correction coefficients Ks and Kd and the correction coefficient Kn are maintained at 1, respectively.

  Therefore, even when the vehicle is traveling on a narrow road at low speed, the correction coefficients Ks, Kn, and Kd are changed when the vehicle turns or meanders and the steering angle θ is large. As a result, it is possible to prevent the target steering gear ratio Rst and the target differential gain Gdt from being increased and corrected, so that the vehicle turns or meanders by changing the target steering gear ratio Rst and the target differential gain Gdt. It is possible to reliably prevent the turning characteristic of the vehicle from changing when the vehicle is driven and the driver from feeling uncomfortable due to this.

(4) When the vehicle travels on a narrow traveling road at medium to high speed In general, when the width of the traveling road is narrow, it is difficult for the vehicle to travel at medium to high speed. Therefore, if an affirmative determination is made in step 320, an affirmative determination is also made in step 325, so step 325 ensures the determination of whether or not the vehicle is traveling on a narrow road. Is for.

  However, it is not completely impossible for the vehicle to travel on a narrow road at medium and high speeds. In this case, a negative determination is made in steps 310 and 315, and an affirmative determination is made in step 320. However, since a negative determination is made at step 325 and the flag F is 0 unless the increase of the target steering gear ratio Rst and the target differential gain Gdt is being corrected, a negative determination is made at step 360. In 375, the narrow path correction coefficients Ks and Kd and the correction coefficient Kn are maintained at 1, respectively, and the target steering gear ratio Rst and the target differential gain Gdt are not corrected for increase.

  If the target steering gear ratio Rst and the target differential gain Gdt are being corrected for increase, an affirmative determination is first made in step 360. If the vehicle is not turning, an affirmative determination is made in step 365. In step 375, the narrow path correction coefficients Ks and Kd and the correction coefficient Kn are returned to 1, respectively, thereby completing the increase correction of the target steering gear ratio Rst and the target differential gain Gdt.

(5) When the vehicle moves to a wider traveling path than a narrow traveling path In this case, a negative determination is made in steps 310 and 315, but at the stage when the vehicle goes out to a wider traveling path. In step 320, a negative determination is made, and in step 360, an affirmative determination is made.

  When the vehicle moves from a narrow travel path to a wider travel path in a substantially straight traveling state, an affirmative determination is made in step 365, so in step 375 the narrow road correction coefficient Ks, Kd and the correction coefficient Kn are each returned to 1, thereby completing the increase correction of the target steering gear ratio Rst and the target differential gain Gdt.

  On the other hand, if the vehicle moves while slowly turning to a wider travel path than a narrow travel path, a negative determination is made in step 365, so the flag F and correction coefficients Ks, Kn, Kd are determined. Remains unchanged from the previous value. Therefore, when the vehicle moves while slowly turning from a narrow travel path to a wider travel path, the correction coefficients Ks, Kn, Kd are changed, and thereby the target steering gear ratio Rst and the target differential gain Gdt. Is prevented from being corrected, thereby changing the turning characteristics of the vehicle when moving while turning slowly to a wider road than a narrow road and It is possible to reliably prevent the user from feeling uncomfortable.

(6) When the vehicle moves to a narrower traveling path than a wider traveling path In this case as well, a negative determination is made in steps 310 and 315, but at the stage when the vehicle has entered a narrower traveling path. An affirmative determination is made at step 320 and an affirmative determination is made at step 330.

  When the vehicle moves in a substantially straight state from a wide travel path to a narrow travel path, an affirmative determination is made in step 335, so that the travel path width in steps 345 and 355, respectively. The narrow road correction coefficients Ks and Kd are calculated according to Wd, and the correction coefficient Kn is calculated according to the absolute value of the steering angle θ and the vehicle speed V at step 350, whereby the target steering gear ratio Rst and the target differential gain are calculated. Gdt increase correction is started.

  On the other hand, if the vehicle moves while turning slowly to a narrower traveling path than a wider traveling path, a negative determination is made in step 335, so the flag F is maintained at 0 and the correction coefficient Ks and Kd are maintained at 1 which is the previous value without being changed. Therefore, when the vehicle moves while turning slowly to a narrower traveling path than a wider traveling path, the narrow path correction coefficients Ks, Kn, and Kd are changed, and thereby the target steering gear ratio Rst and the target differential are changed. The gain Gdt is prevented from being corrected to increase, thereby changing the turning characteristics of the vehicle when moving while turning slowly to a narrower traveling path than a wider traveling path, and driving due to this. It is possible to surely prevent a person from feeling uncomfortable.

(7) When the driver suddenly changes the course of the vehicle The driver suddenly changes the course of the vehicle, such as when the driver performs a sudden steering operation to avoid a collision with an obstacle ahead of the vehicle. In this case, the differential gain of the steering gear ratio and the steering transmission ratio is preferably controlled to a value that does not hinder the driver's course change of the vehicle.

  In general, when the driver changes the course of the vehicle abruptly, the steering operation of the driver becomes a fast and transient steering operation, and the magnitude of the steering operation speed is larger than when the vehicle travels along the road. Therefore, an affirmative determination is made in step 315 regardless of the width of the travel path, the flag F is maintained at 0 in step 370, and the correction coefficient Ks, Kn and Kd are maintained at 1, respectively, so that increase correction of the target steering gear ratio Rst and the target differential gain Gdt is not performed.

  Therefore, when the driver suddenly changes the course of the vehicle, the steering gear ratio and the differential gain do not increase, so the steering gear ratio makes it difficult for the driver to change the course of the vehicle, or the differential gain is high. Thus, it is possible to reliably prevent the turning responsiveness from being too high and feeling that the running stability of the vehicle has deteriorated.

(8) When the driver wants to gently change the course of the vehicle The driver performs a gentle steering operation from a state where the vehicle is traveling on a narrow road at a low speed (the flag F is 1). When the vehicle course is to be changed gently by turning left or right or entering the garage, the driver's steering operation does not become a fast steering operation, so a negative determination is made in step 315, and steps 320- At 330, an affirmative determination is made.

  However, since the magnitude of the steering angle θ is increased, the correction coefficient Kn is calculated to a smaller value in step 350 than when the magnitude of the steering angle θ is small. Therefore, even if the width of the travel path is narrow and the correction coefficient Ks is a large value, the target steering gear ratio Rst is reduced, so that it is difficult for the driver to change the course of the vehicle due to the large steering gear ratio. It can be surely prevented.

(9) When there is a possibility that the vehicle will collide with a front obstacle When there is a possibility that the vehicle will collide with a front obstacle, there is a possibility that the driver will make a sudden course change by a steering operation for avoiding the collision thereafter. Therefore, it is preferable that the differential gains of the steering gear ratio and the steering transmission ratio are controlled to values that do not hinder the course change of the vehicle as in the case of (7) above.

  In this case, since an affirmative determination is made in step 310 regardless of the width of the travel path, the flag F is maintained at 0 in step 370 as in the case of (7) above. In step 375, the correction coefficients Ks, Kn, and Kd are maintained at 1, respectively, so that the target steering gear ratio Rst and the target differential gain Gdt are not corrected to increase.

  Therefore, since the steering gear ratio and the differential gain do not increase when the driver starts changing the course of the vehicle to avoid a collision, the driver can change the course of the vehicle to avoid a collision because the steering gear ratio is large. It is possible to surely prevent a situation where it is impossible to start automatically.

  As can be understood from the above description, according to the illustrated embodiment, when the vehicle travels on a narrow road, the steering gear ratio is increased and corrected so that the vehicle can travel stably along the travel path. Not only can the differential gain of the steering transmission ratio be increased, but the turning response of the vehicle can be improved when the vehicle turns or meanders along the road. Therefore, it is possible to improve the driving feeling when traveling on a narrow road as compared with the conventional case.

  In particular, according to the illustrated embodiment, the width of the travel path changes as the vehicle travels, so that even if the target steering gear ratio Rst and the target differential gain Gdt should be increased and changed, the driver can steer. When the operation is performed and the vehicle is in a turning state, a negative determination is made in step 335 or 365, so that the target steering gear ratio Rst and the target differential gain Gdt are not increased and changed. It is possible to reliably prevent the turning response of the vehicle from changing while the driver is feeling uncomfortable due to this change.

  When the driver performs a steering operation and the vehicle is in a turning state, the target steering gear ratio Rst and the target differential gain Gdt are not increased or changed. However, in steps 220 and 230, the basic target steering gear ratio Rsbt and the basic target differential gain are not changed. Since Gdbt is variably set according to the vehicle speed V, the optimization of the steering characteristics according to the vehicle speed V is continued.

  Further, according to the illustrated embodiment, even when the vehicle travels on a narrow road, when the driver is performing a steering operation for a sudden course change, an affirmative determination is made in step 315. As a result, the target steering gear ratio Rst and the target differential gain Gdt are not corrected to increase, so that it is possible to prevent the turning response of the vehicle from being insufficient, thereby changing the lane to the adjacent lane by emergency steering to avoid danger such as a collision. Thus, it is possible to ensure a situation in which the course can be easily and reliably changed.

  Further, according to the illustrated embodiment, when the driver is performing a gentle course change steering operation in a situation where the vehicle travels on a narrow road at a low speed, the magnitude of the steering angle θ is determined in step 350. A correction coefficient Kn for the target steering gear ratio is calculated so as to decrease as the vehicle speed V decreases and as the vehicle speed V decreases. In step 510, the product of the basic target steering gear ratio Rsbt, the narrow road correction coefficient Ks, and the correction coefficient Kn. Since the target steering gear ratio Rst is calculated as follows, it is possible to easily and reliably change the course of the vehicle by a steering operation with a large steering angle such as a left or right turn travel path change, garage entry, and width adjustment. Can be secured.

  Further, according to the illustrated embodiment, when there is a possibility that the vehicle 12 may collide with an obstacle in front of the vehicle 12, an affirmative determination is made in step 310, so that the driver can perform a steering operation for abrupt course change. As in the case where the driving is performed, the target steering gear ratio Rst and the target differential gain Gdt are not corrected to increase, so that the steering gear ratio and the differential gain are high when the driver starts changing the course of the vehicle to avoid a collision. Thus, it can be ensured that the driver can reliably and effectively start the course change of the vehicle for avoiding the collision.

  Further, according to the illustrated embodiment, when the target steering gear ratio Rst is increased and corrected, the target differential gain Gdt is also increased and corrected simultaneously. Therefore, the target steering gear ratio Rst and the target differential gain Gdt are increased and corrected under different conditions. Control of these increase corrections can be simplified compared to what is done.

    Further, according to the illustrated embodiment, when the driver is performing a steering operation for sudden change of course and when there is a possibility that the vehicle 12 may collide with an obstacle in front of the vehicle 12, in step 375. Since both the narrow road correction coefficients Ks and Kd are set to 1, and both the target steering gear ratio Rst and the target differential gain Gdt are controlled to values smaller than the values that are increased and corrected according to the travel road width, for example, The driver can easily and reliably change the course of the vehicle as compared with the case where only the target steering gear ratio Rst is controlled to a small value.

  Further, according to the illustrated embodiment, when the target steering gear ratio Rst and the target differential gain Gdt are increased and corrected when the vehicle is traveling on a narrow road, the steering assist torque generated by the electric power steering device 22 is reduced. Since the steering reaction force of the steering wheel 20 increases, this also improves the running stability when the vehicle runs on a narrow road.

  Although the present invention has been described in detail with reference to specific embodiments, the present invention is not limited to the above-described embodiments, and various other embodiments are possible within the scope of the present invention. It will be apparent to those skilled in the art.

For example, in the above-described embodiment, the target differential gain Gdt is a differential gain of the steering transmission ratio. However, the target differential gain may be the target differential gain Gst of the steering gear ratio. Gst is calculated to be smaller as the traveling road width Wd is smaller. In that case, the above equation 1 is changed to the following equation 3.
θpt = θ / Rst + θd / Gst (3)

  Further, in the above-described embodiment, even if the travel path width changes when the vehicle is traveling on a narrow road, the target steering gear ratio Rst and the target are not affected by the vehicle speed V when the vehicle is turning. Although the differential gain Gdt is not changed, it may be modified so that only the target differential gain Gdt is not changed.

  Further, in the above-described embodiment, the target steering gear ratio Rst is used when the driver suddenly changes the course or when the vehicle 12 may collide with an obstacle ahead. Although the target differential gain Gdt is not corrected to increase, the target differential gain Gdt is corrected to increase without correcting the target steering gear ratio Rst, thereby making it easier and more reliable for the driver It may be modified to change.

  Also, in the above-described embodiment, when the driver performs a gentle course change steering operation, the smaller the steering angle θ is, the smaller the steering angle θ is, and the smaller the vehicle speed V is, the smaller is the step 350. Thus, the correction coefficient Kn for the target steering gear ratio is calculated, but it may be modified so that the correction coefficient for the target differential gain Gdt is also calculated.

  In the above-described embodiment, the determinations in steps 335 and 365 are performed, so that the target steering gear ratio Rst and the target differential gain Gdt can be obtained when the vehicle is turning even if the vehicle is traveling on a narrow road. However, Steps 330 to 340 and Steps 360 to 370 may be omitted.

  In the above-described embodiment, the horizontal axis of the map shown in FIG. 9 for calculating the narrow road correction coefficient Kd is the travel road width Wd, but the correction coefficient Kd is shown in FIG. As described above, the calculation may be made based on the narrow path correction coefficient Ks.

  In the above embodiment, the traveling road width Wd is calculated based on the image information in front of the vehicle taken by the CCD cameras 58 and 60. Information on the traveling road width Wd may be acquired in any manner known in the art.

  In the above-described embodiment, the electric power steering device 22 is mounted on the vehicle 12, and when the target steering gear ratio Rst and the target differential gain Gdt are increased and corrected when the vehicle is traveling on a narrow road, Although the steering assist torque generated by the power steering device 22 is reduced, the reduction of the steering assist torque may be omitted, and the steering control torque of the present invention is not controlled to increase or decrease the steering assist torque. It may be applied to a vehicle.

  Further, in the above-described embodiment, the turning angle varying device 14 as the steering gear ratio varying means depends on the driver's steering operation by rotating the lower steering shaft 30 relative to the upper steering shaft 28. The steering gear ratio is increased or decreased by automatically turning the left and right front wheels 18FL and 18FR, but the steering gear ratio variable means steers the steered wheels independently of the driver's steering operation. As long as it can be obtained, it may be of any construction known in the art, such as, for example, a steering angle varying device of the type that expands and contracts the tie rods 26L and 26R.

It is a schematic block diagram which shows one Example of the steering control apparatus of the vehicle by this invention applied to the vehicle carrying an electric power steering device. It is a flowchart which shows the main routine of the steering control in an Example. FIG. 3 is a flowchart showing a routine for calculating narrow path correction coefficients Ks and Kd in step 300 of the flowchart shown in FIG. 2. It is a flowchart which shows the control routine of the steering assist torque in an Example. FIG. 6 is a diagram showing a map for calculating a basic target steering gear ratio Rsbt based on the vehicle speed V. It is a figure which shows the map for calculating the basic target differential gain Gdbt based on the vehicle speed V. FIG. It is a figure which shows the map for calculating the narrow road correction coefficient Ks about a target steering gear ratio based on the traveling road width Wd. FIG. 5 is a diagram showing a map for calculating a correction coefficient Kn for a target steering gear ratio based on the absolute value of the steering angle θ and the vehicle speed V. It is a figure which shows the map for calculating the narrow path correction coefficient Kd about a target differential gain based on the travel path width Wd. It is a figure which shows the map for calculating the basic assist torque Tab based on the steering torque Ts. It is a figure which shows the map for calculating the vehicle speed coefficient Kv based on the vehicle speed V. FIG. It is a figure which shows the map for calculating the correction coefficient Kt about target assist torque based on the travel path width Wd. It is a figure which shows the map for calculating the narrow path correction coefficient Kd about a target differential gain based on the narrow path correction coefficient Ks.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Steering control device, 14 ... Steering angle variable device, 16 ... Electronic control device, 20 ... Steering wheel, 22 ... Electric power steering device, 50 ... Steering angle sensor, 52 ... Steering torque sensor, 54 ... Rotation angle sensor 56 ... Vehicle speed sensor, 58, 60 ... CCD camera, 62 ... Radar sensor

Claims (6)

  Steering gear ratio variable means, control means for controlling the steering gear ratio by controlling the steering gear ratio variable means, and means for detecting the travel path width, the control means when the travel path width is small In a vehicle steering control device that increases the steering gear ratio as compared with a case where the travel path width is large, the control means is configured such that when the travel path width is small, the steering transmission ratio is larger than when the travel path width is large. A steering control device for a vehicle, wherein a differential gain is increased.   Even if the travel path width fluctuates as the vehicle travels, the control means is configured such that the steering gear ratio and the differential based on the travel path width are greater when the magnitude of the steering operation amount of the driver is equal to or greater than the straight travel determination reference value. 2. The vehicle steering control device according to claim 1, wherein the gain is not changed.   The control means determines whether or not the driver is performing a steering operation for changing the course, and if it is determined that the driver is performing a steering operation for changing the course, at least the steering gear ratio is set to the travel path width. The vehicle steering control device according to claim 1, wherein the vehicle steering control device is controlled to a value smaller than a value changed based on the value.   The control means, when the magnitude of the change rate of the driver's steering operation amount is equal to or greater than a course change determination reference value, determines that the driver is performing a course change steering operation. The vehicle steering control device according to claim 3.   The control means determines whether or not the vehicle may collide with an obstacle in front of the vehicle, and when determining that the vehicle may collide with an obstacle in front of the vehicle, at least the steering gear ratio is set. The vehicle steering control device according to claim 1, wherein the vehicle steering control device is controlled to a value smaller than a value changed based on the travel path width. The control means controls at least the steering gear ratio to a smaller value when the magnitude of the steering operation amount of the driver is larger than when the magnitude of the steering operation amount of the driver is small. Item 6. The vehicle steering control device according to any one of Items 1 to 5.

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