JP2012116430A - Steering apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform steering control adapted to sensory properties of a driver, when, for example, a vehicle travels straight on a slant road.SOLUTION: A steering apparatus includes: a first specifying device for specifying a road width of a road where the vehicle travels, on the basis of an operation amount on which the driver operates a steering wheel; a second specifying device for specifying a slant of the road in a road width direction; and a controller of controlling assist torque for assisting steering of the vehicle by the driver, on the basis of the specified road width and the specified slant.

Description

  The present invention relates to a technical field of a steering device that is mounted on a vehicle and steers steered wheels according to an operation of a steering handle by a driver.

  With regard to this type of steering device, for example, Patent Document 1 discloses an assist generated by a motor in accordance with the road environment (for example, road width) in front of the vehicle obtained from the road map information of the navigation device. A technique for adjusting the force is disclosed. Further, for example, in Patent Document 2, a road surface inclination in a road width direction of a road in a traveling direction of a vehicle is calculated based on an image captured by an in-vehicle camera, and a motor operation amount is calculated according to the calculated road surface inclination. Techniques for controlling are disclosed. Further, for example, Patent Literature 3 discloses a technique for detecting a slope in a width direction of a road on which a vehicle travels from a navigation system and controlling a steering torque in accordance with the detected slope. Further, for example, Patent Document 4 discloses a technique for applying an additional friction torque according to the steering angle and the vehicle speed to the steering (that is, the steering wheel) in order to reduce the holding force and improve the stability during steering holding. It is disclosed.

JP 2007-22373 A JP 2009-255878 A JP 2007-106250 A JP 2009-126244 A

  The driver's perceptual characteristics may differ depending on the driver, and the way the user feels about the road environment (for example, whether the road is felt narrow or wide) may differ depending on the driver. However, the techniques disclosed in, for example, Patent Documents 1 to 4 described above do not take into account the driver's perceptual characteristics, and thus may not be able to perform steering control suitable for the driver's perceptual characteristics. There is a problem.

  On the other hand, when the vehicle travels straight on a road inclined in the width direction of the road (hereinafter referred to as “slant road” as appropriate), a gravity component directed downward of the inclination in the width direction of the road (that is, the gradient) acts on the vehicle. Therefore, there is a possibility that it is a burden for the driver to hold the steering wheel at the intended steering angle (that is, to hold the steering wheel).

  The present invention has been made in view of the above-described problems, for example, and provides a steering apparatus capable of performing steering control suitable for a driver's perceptual characteristics when a vehicle travels straight on a slant road, for example. Is an issue.

  In order to solve the above problems, a steering device of the present invention is a steering device that is mounted on a vehicle and steers steered wheels in response to an operation of a steering wheel by a driver, and the driver operates the steering wheel. First specifying means for specifying the road width of the road on which the vehicle travels, second specifying means for specifying the inclination of the road in the road width direction, the specified road width, Control means for controlling assist torque for assisting steering of the vehicle by the driver based on the specified inclination.

  According to the steering device of the present invention, for example, when the vehicle is traveling, the first specifying means calculates the operation amount (for example, the value of the steering angle, the steering torque, the steering speed, or the like by the driver operating the steering wheel). The road width of the road on which the vehicle is traveling is specified based on the calculated value or the time-dependent change or frequency change). Here, normally, the driver changes the amount of operation of the steering wheel unconsciously or consciously according to the width of the road recognized visually. That is, the amount of steering by which the driver operates the steering wheel (in other words, the amount of operation of the steering wheel by the driver) changes depending on the road width of the road regardless of whether the driver is aware of it. That is, the operation amount of the steering wheel changes depending on the road width. Therefore, by acquiring the relationship between the operation amount of the steering wheel and the road width in advance by, for example, experiments, the road width can be specified based on the change in the operation amount of the steering wheel. For example, when the road width of the road on which the vehicle is traveling is relatively wide, the operation amount of the steering wheel is relatively small. When the road width of the road on which the vehicle is traveling is relatively narrow, the operation amount of the steering wheel is It has been confirmed by experiments by the inventors of the present application that the size is relatively large. Therefore, when the operation amount of the steering wheel is relatively small, it can be specified that the road width is relatively wide. When the operation amount of the steering wheel is relatively large, it is specified that the road width is relatively narrow. be able to.

  The second specifying means specifies, for example, the inclination in the road width direction of the road on which the vehicle travels based on a lateral force (that is, lateral G) acting on the vehicle. For example, when the vehicle travels straight on a road, the lateral force acting on the vehicle increases as the inclination of the road in the road width direction increases. Therefore, the inclination in the road width direction of the road on which the vehicle travels can be specified based on the lateral force acting on the vehicle.

  The control means controls an assist torque for assisting the steering of the vehicle by the driver based on the road width specified by the first specifying means and the inclination specified by the second specifying means. Specifically, for example, when the slope specified by the second specifying unit is equal to or greater than a predetermined threshold, the control unit increases the assist torque as the road width specified by the first specifying unit is narrower. Therefore, for example, when the vehicle travels straight on a road inclined in the road width direction (that is, a slant road), it is possible for the driver to easily hold the steering wheel (that is, to easily hold the steering wheel). In other words, when the vehicle travels straight on a slant road, it is possible to reduce the steering torque (hereinafter referred to as “steering torque” as appropriate) that the driver should apply to the steering wheel for steering. The steering feeling can be improved. The “assist torque” is torque applied to the steered wheels from, for example, a motor to assist the driver in steering the vehicle. Basically, the “assist torque” is the steering torque applied to the steering wheel by the driver. Determined based on.

  Here, if no measures are taken, if the vehicle is traveling straight on a slant road, the vehicle will be placed below the slope in the road width direction due to the slope in the road width direction of the road. Since a gravitational component is generated, the steering handle easily rotates in the steering angle direction corresponding to the lower side of the inclination in the road width direction, which may make it difficult for the driver to hold the steering handle. That is, the driver's steering feeling may be deteriorated. Furthermore, the steering width of the vehicle becomes more important as the road width of the road becomes narrower.

  In the present invention, as described above, the assist torque is controlled based on the road width specified by the first specifying means and the slope specified by the second specifying means. For example, the vehicle travels straight on a slant road. It is possible to improve the steering feeling of the driver when the vehicle is in the middle. Here, in the present invention, in particular, the road width of the road on which the vehicle travels is specified based on the amount of operation of the steering wheel by the driver. In other words, the road width of the road is specified based on the characteristics of the steering wheel operation by the driver (that is, the steering characteristics of the driver). Therefore, the steering characteristic according to the driver's perceptual characteristic is reflected in the road width of the road specified by the first specifying means. Therefore, by controlling the assist torque in accordance with the road width specified by the first specifying means, it is possible to perform the steering control suitable for the driver's perceptual characteristics.

  As described above, according to the steering device of the present invention, it is possible to perform the steering control suitable for the driver's perceptual characteristics, and for example, improve the steering feeling of the vehicle when the vehicle travels straight on the slant road. Can be made.

  In one aspect of the steering apparatus of the present invention, the first specifying means specifies the road width as one of a narrow road width and a wide road width, and the control means is a road with the specified road width being the narrow road. When the width is a width, the assist torque is set larger than when the specified road width is the wide road width.

  According to this aspect, for example, when the vehicle is traveling straight on a slant road having a narrow road width, the driver's steering feeling can be reliably improved. In particular, when the road width is narrow, the assist torque becomes larger than when the road width is wide, so that the steering torque is reduced and the driver can feel that the steering wheel is easily held.

  The control means can determine that the road on which the vehicle is traveling is a slant road, for example, when the slope specified by the second specifying means is greater than or equal to a predetermined threshold. When the slope specified by the means is smaller than a predetermined threshold, it can be determined that the road on which the vehicle is traveling is not a slant road.

  In another aspect of the steering apparatus of the present invention, the control means increases the assist torque as the identified road width is narrower.

  According to this aspect, for example, when the vehicle is traveling straight on a slant road, the driver's steering feeling can be improved more reliably.

  In another aspect of the steering apparatus of the present invention, the control means sets a basic assist torque that is a basis of the assist torque based on a steering torque applied to the steering handle and a vehicle speed of the vehicle. And first correction means for correcting the set basic assist torque based on the specified road width and the specified slope.

  According to this aspect, the assist torque is set by correcting the basic assist torque set by the first setting means by the first correction means based on the road width and the inclination in the road width direction. Therefore, for example, when the vehicle travels straight on a slant road, assist torque suitable for the road width and the inclination in the road width direction can be generated, and the driver's steering feeling can be improved.

  In the aspect in which the control means includes the first setting means and the first correction means, the first correction means is configured such that the basic assist torque increases as the identified road width decreases. The basic assist torque is corrected so that the magnitude of the basic assist torque increases as the specified inclination increases.

  According to this aspect, for example, when the vehicle travels straight on a slant road, assist torque more suitable for the road width and the inclination in the road width direction can be generated, and the driver's steering feeling can be more reliably ensured. Can be improved.

  In another aspect of the steering apparatus of the present invention, the control means sets an additional friction torque that simulates a frictional resistance based on a steering angle applied to the steering handle and a vehicle speed of the vehicle. And a second correction means for correcting the set additional friction torque based on the specified road width and the specified inclination, and the corrected additional friction torque is applied to the steering wheel. The assist torque is controlled so as to be generated.

  According to this aspect, for example, when the vehicle travels straight on a slant road, an additional friction torque suitable for the road width and the inclination in the road width direction can be generated in the steering handle, and the driver's steering fee can be increased. The ring can be improved. The “additional friction torque” according to the present invention is a torque generated in the steering handle by simulating the frictional resistance generated in the steering system from the steering handle to the steered wheels. What is the steering direction of the steering handle by the driver? Torque acting in the opposite direction.

  In the aspect in which the control unit includes the second setting unit and the second correction unit, the second correction unit increases the magnitude of the additional friction torque as the identified road width decreases. The additional friction torque is corrected so that the magnitude of the additional friction torque increases as the specified inclination increases.

  According to this aspect, for example, when the vehicle travels straight on a slant road, it is possible to generate additional friction torque on the steering wheel that is more suitable for the road width and the inclination in the road width direction. The ring can be improved more reliably.

  The effect | action and other gain of this invention are clarified from the form for implementing invention demonstrated below.

1 is a block diagram illustrating an overall configuration of a vehicle including a steering device according to a first embodiment. 3 is a flowchart conceptually showing a flow of assist torque control according to the first embodiment. It is a flowchart which shows notionally the flow of the road width determination process which concerns on 1st Embodiment. It is a figure for demonstrating the road width determination process which concerns on 1st Embodiment. It is a figure for demonstrating the slant path straight travel determination process which concerns on 1st Embodiment. It is a figure which shows notionally the assist torque control only for a slant road which concerns on 1st Embodiment. It is the figure which showed an example of the method of calculating | requiring the friction torque Tt. It is a figure which shows an example of the characteristic of additional friction torque Tc. It is an image figure showing the characteristic of additional friction torque Tc with a visible model. It is a schematic diagram which shows the state which the vehicle which concerns on a comparative example is drive | working the slant road. It is a graph which shows an example of the relationship between the steering torque which the driver | operator of the vehicle which concerns on a comparative example provides to a steering wheel, and a steering angle. It is a graph which shows an example of the effect by assist torque control concerning this embodiment.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

<First Embodiment>
A steering apparatus according to a first embodiment will be described with reference to FIGS.

  First, an overall configuration of a vehicle including a steering device according to the present embodiment will be described with reference to FIG.

  FIG. 1 is a block diagram illustrating an overall configuration of a vehicle including a steering apparatus according to the present embodiment.

  As shown in FIG. 1, the vehicle 1 includes a front wheel 5 and a steering device 10 for steering the front wheel 5. The steering device 10 is an electric power steering (EPS) device that steers the front wheels 5 in accordance with the operation of the steering wheel 11, and includes a steering wheel 11, a steering shaft 12, a pinion shaft 19, and a steering angle. A sensor 13, a torque sensor 14, a motor 15, a rack and pinion mechanism 16, a tie rod 17, a knuckle arm 18, a vehicle speed sensor 41, a lateral G sensor 42, a yaw rate sensor 43, and a controller 100 are provided. ing.

  The steering wheel 11 is an example of a “steering handle” according to the present invention, and is operated by a driver (driver) to turn the vehicle 1 or the like. The steering wheel 11 is connected to a rack and pinion mechanism 16 via a steering shaft 12 and a pinion shaft 19. The steering shaft 12 is provided with a steering angle sensor 13 and a torque sensor 14.

  The steering angle sensor 13 detects the steering angle SWA (that is, the rotation angle of the steering wheel 11) corresponding to the operation of the steering wheel 11 by the driver. The steering angle sensor 13 supplies a detection signal corresponding to the detected steering angle SWA to the controller 100.

  The torque sensor 14 detects a steering torque SWT applied to the steering shaft 12 via the steering wheel 11. The torque sensor 22 supplies a detection signal corresponding to the detected steering torque SWT to the controller 100.

  One end of the pinion shaft 19 is connected to the rack and pinion mechanism 16, and the other end is connected to the steering shaft 12 via the torque sensor 14. The pinion shaft 19 is configured to be able to rotate in the same direction as the steering shaft 12. The pinion shaft 19 is provided with a motor 15.

  The motor 15 is configured by a speed reducer, an electric motor, or the like, and applies torque to the pinion shaft 19 under the control of the controller 100. The torque applied to the pinion shaft 19 by the motor 15 is an example of the “assist torque” according to the present invention. Hereinafter, the torque applied by the motor 15 to the pinion shaft 19 is appropriately referred to as “assist torque”.

  The vehicle speed sensor 41 detects the vehicle speed of the vehicle 1 and supplies a detection signal corresponding to the detected vehicle speed V to the controller 100.

  The lateral G sensor 42 detects a lateral G acting on the vehicle 1 (that is, a force acting in the vehicle width direction), and supplies a detection signal corresponding to the detected lateral G to the controller 100.

  The yaw rate sensor 43 detects the yaw rate of the vehicle 1 (that is, the changing speed of the rotation angle in the turning direction), and supplies a detection signal corresponding to the detected yaw rate to the controller 100.

  The rack and pinion mechanism 16 is constituted by a rack and a pinion, and operates by transmitting rotation from the steering shaft 12 via the pinion shaft 19. A tie rod 17 and a knuckle arm 18 are connected to the rack and pinion mechanism 16, and the front wheel 5 is connected to the knuckle arm 18. In this case, when the tie rod 17 and the knuckle arm 18 are operated by the rack and pinion mechanism 16, the front wheel 5 connected to the knuckle arm 18 is steered.

  The controller 100 is an electronic control unit including a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and the like. The controller 100 sets assist torque that the motor 15 should apply to the pinion shaft 19, and performs assist torque control that controls the motor 15 so that the set assist torque is applied to the pinion shaft 19. The controller 100 functions as “first specifying means”, “second specifying means”, and “control means” according to the present invention. As will be described in detail later, in the present embodiment, in particular, the controller 100 uses an operation amount per unit time of the steering wheel 11 based on detection signals supplied from the steering angle sensor 13 and the torque sensor 14. A certain steering power P is calculated, and a road width determination process for determining the road width of the road on which the vehicle 1 travels is performed based on the calculated steering power P. Further, the controller 100 determines whether or not the vehicle 1 is traveling straight on a slant road (that is, a road inclined in the road width direction) based on detection signals supplied from the lateral G sensor 42 and the yaw rate sensor 43. Determine whether.

  Next, assist torque control according to the present embodiment will be described with reference to FIGS.

  FIG. 2 is a flowchart conceptually showing a flow of assist torque control according to the present embodiment.

  In the assist torque control according to the present embodiment, different control is performed when the vehicle 1 travels straight on a slant road and when it does not. That is, in the present embodiment, when the vehicle 1 is traveling straight on a slant road, a slant road-specific assist torque control described later is performed, and in other cases, normal assist torque control is performed. That is, normal assist torque control is basically performed except when the slant road-specific assist torque control is performed. Note that various assist torque controls that are generally performed can be applied as the normal assist torque control.

  In FIG. 2, in the assist torque control according to the present embodiment, first, a road width determination process is performed by the controller 100 (step S10).

  FIG. 3 is a flowchart conceptually showing a flow of the road width determination process.

  In FIG. 3, in the road width determination process, first, initial setting is performed by the controller 100 (step S110). Specifically, the controller 100 sets predetermined initial values for predetermined threshold values SWAt and SWTt, a predetermined determination reference value Pt, a dead zone D width δ, a predetermined time Ta, and a road width determination value, which will be described later. For example, the controller 100 sets “wide” as the initial value for the road width determination value.

  Next, an input signal is acquired by the controller 100 (step S120). Specifically, the controller 100 acquires, as input signals, a detection signal corresponding to the steering angle SWA and a detection signal corresponding to the steering torque SWT from the steering angle sensor 13 and the torque sensor 14, respectively. Information regarding the steering angle SWA may be acquired from the rotation angle of the EPS motor (that is, the motor 15) or the tire turning angle (that is, the turning angle of the front wheels 5) instead of the steering angle sensor 13.

  Acquisition of the input signal by the controller 100 is performed every predetermined sampling time Ts. At this time, the controller 100 calculates the steering speed SWV by dividing the steering angle SWA by the sampling time Ts. That is, the controller 100 calculates the steering speed SWV according to the following equation (1).

Steering speed SWV = (steering angle SWA (n) −steering angle SWA (n−1)) / sampling time Ts (1)
However, n is a natural number, and the steering angle SWA (n) represents the nth acquired steering angle SWA.

  Note that when the input signal is acquired, a low-pass filter process for removing a high-frequency component of the input signal is performed.

  Next, the steering power P is calculated by the controller 100 (step S130). That is, the controller 100 calculates the steering power P based on the steering torque SWT and the steering speed SWV. The steering work rate P means work done per unit time by the driver on the steering wheel 11.

  Specifically, the controller 100 first calculates the average values SWTmean and SWVmean of the steering torque SWT and the steering speed SWV acquired for each sampling time Ts from the present time to the past by a predetermined time Ta. Next, an average value SWTa of a difference between the steering torque SWT and the average value SWTmean at a predetermined time Ta, and an average value SWVa of the difference between the steering speed SWV and the average value SWVmean at a predetermined time Ta are calculated. . Next, the steering power P is calculated by multiplying the average value SWTa and the average value SWVa. That is, the controller 100 calculates the steering power P according to the following equation (2).

Steering power P = steering torque average value SWTa × steering angle average value SWVa (2)
That is, the controller 100 calculates the average value of the change amount (or the change amount) for each of the steering torque SWT and the steering speed SWV acquired up to the past for the predetermined time Ta from the present time, and steers the product of the calculated average values. Calculated as the work rate P.

  Next, it is determined by the controller 100 whether or not the steering power P is not less than the determination reference value Pt + δ / 2 (step S140).

  FIG. 4 is a diagram for explaining the road width determination process according to the present embodiment. The steering angle SWA and the steering torque SWT acquired by the controller 100 and the steering work rate P calculated by the controller 100 are respectively changed over time. An example is shown. In the present embodiment, as shown in FIG. 4, the direction of the steering angle SWA and the direction of the steering torque SWT are represented by positive and negative, for example, a positive value is the left rotation direction of the steering wheel 11, and a negative value is the steering wheel. 11 is the right rotation direction.

  That is, in FIGS. 3 and 4, the controller 100 determines whether or not the steering power P is equal to or greater than the determination reference value Pt + δ / 2 at the current time Tp (step S140). That is, the controller 100 determines whether or not the following equation (3) is satisfied.

Steering power P ≧ determination reference value Pt + δ / 2 (3)
Here, the determination reference value Pt is a value of the steering power P that serves as a boundary for distinguishing whether the road width of the road on which the vehicle 1 travels is wide or narrow, and is set in advance by, for example, experiments. Specifically, the determination reference value Pt is set as the minimum steering power P that can be determined that the road width of the road on which the vehicle 1 travels is narrow. Here, when the road width of the road on which the vehicle 1 travels is wide, the steering power P is small, and when the road width of the road on which the vehicle 1 travels is narrow, the steering power P is large. This has been confirmed by the inventors' experiments. Therefore, it is possible to detect a change over time in the width of the road on which the vehicle 1 travels based on the change over time in the steering power P. Therefore, in the present embodiment, for two different road widths having a significant difference in the steering power P by experiment or the like in advance, one is set as a wide road width and the other is set as a narrow road width. The steering power P that can distinguish a narrow road width is set as the determination reference value Pt.

  As shown in FIG. 4, a dead zone D having a width δ is set with respect to the determination reference value Pt. The dead zone D is set as a range of the steering power P in which it is not determined whether or not the steering power P is larger than the determination reference value Pt. The dead zone D has a width δ with the determination reference value Pt as the center value. That is, the upper limit value of the dead zone D is a value obtained by adding the determination reference value Pt and the width δ / 2 (that is, ½ times the width δ of the dead zone D), and the lower limit value of the dead zone D is the determination reference value. This is a value obtained by subtracting the width δ / 2 from Pt.

  When it is determined that the steering power P is equal to or greater than the determination reference value Pt + δ / 2 (step S140: YES), the controller 100 determines that the road width on which the vehicle 1 is traveling is narrow, and the road width The determination value is set to “narrow” (step S160).

  Here, the road width determination value is a value indicating the road width determined by the controller 100. When the road width is determined to be narrow, the road width determination value is set to “narrow”, and when the road width is determined to be wide. Is set to “wide”. As described above, in the initial setting (step S110), “wide” is set as the road width determination value.

  On the other hand, when it is determined that the steering power P is not equal to or greater than the determination reference value Pt + δ / 2 (that is, the steering power P is smaller than the determination reference value Pt + δ / 2) (step S140: NO), the steering power is determined. The controller 100 determines whether or not P is equal to or less than the determination reference value Pt−δ / 2 (step S150).

  That is, in FIG. 4, the controller 100 determines whether or not the steering power P is equal to or less than the determination reference value Pt−δ / 2 at the current time Tp (step S150). That is, the controller 100 determines whether or not the following equation (4) is satisfied.

Steering power P ≦ determination reference value Pt−δ / 2 (4)
When it is determined that the steering power P is equal to or less than the determination reference value Pt−δ / 2 (step S150: YES), the controller 100 determines that the road width on which the vehicle 1 is traveling is wide. The road width determination value is set to “wide” (step S170).

  On the other hand, when it is determined that the steering power P is not equal to or less than the determination reference value Pt−δ / 2 (that is, the steering power P is larger than the determination reference value Pt−δ / 2) (step S150: NO). The road width determination value is maintained as it is by the controller 100.

  The determination reference value Pt may be changed by the controller 100 according to the vehicle speed. In this case, it is possible to more accurately determine whether the road on which the vehicle 1 travels is wide or narrow based on the steering power P.

  In the present embodiment, as described above, since the dead zone D is set with respect to the determination reference value Pt, the road width determination result by the controller 100 even though the road width of the actual road has not changed. Can be prevented from changing.

  As described above, in the road width determination process, the road width of the road on which the vehicle 1 is traveling is determined, and the road width determination value is “wide” according to the road width of the road on which the vehicle 1 is traveling. Or it is set to “narrow”.

  Returning to FIG. 2, after the road width determination process (step S10) is performed, the controller 100 determines whether or not the road width determination value is set to “narrow” (step S20).

  When it is determined that the road width determination value is not set to “narrow” (step S20: NO), the road width determination process is performed again after a predetermined time (step S10).

  When it is determined that the road width determination value is set to “narrow” (step S20: YES), the controller 100 determines whether the vehicle 1 is traveling straight on the slant road (step S30). ). That is, the controller 100 determines whether or not the vehicle 1 is traveling straight and the road on which the vehicle 1 travels is a slant road. Hereinafter, the process of determining whether or not the vehicle 1 is traveling straight on the slant road (that is, the process related to step S30) is appropriately referred to as “slant road straight travel determination process”.

  FIG. 5 is a diagram for explaining the slant road straight traveling determination process, and shows an example of temporal changes of the lateral G and yaw rates respectively acquired by the controller 100 from the lateral G sensor 42 and the yaw rate sensor 43, respectively. In the present embodiment, as shown in FIG. 5, the direction of the lateral G and the direction of the yaw rate are represented by positive and negative, for example, a positive value is the left direction or left turn direction of the vehicle 1, and a negative value is the right side of the vehicle 1. Direction or right turn direction. For example, when the vehicle 1 travels on a slant road having a downward slope, the lateral G acting in the right direction acts on the vehicle 1, so that the lateral G has a negative value, and the slant road having a downward slope is left. When the vehicle 1 travels, since the lateral G acting in the left direction acts on the vehicle 1, the lateral G has a positive value.

  In FIG. 5, the controller 100 determines whether or not the vehicle 1 is traveling straight on a slant road based on the yaw rate detected by the yaw rate sensor 43 and the lateral G detected by the lateral G sensor 42. . More specifically, the controller 100 determines that the magnitude of the yaw rate detected by the yaw rate sensor 43 is equal to or less than a predetermined threshold YRa, and the magnitude of the lateral G detected by the lateral G sensor 42 is equal to or greater than the predetermined threshold LGa. Is continued for a predetermined time Tb or longer, it is determined that the vehicle 1 is traveling straight on the slant road. As a method for determining whether or not the vehicle 1 is traveling straight on a slant road, another determination method may be used.

  Returning to FIG. 2, if it is determined that the vehicle 1 is not traveling straight on the slant road (step S30: NO), the road width determination process is performed again after a predetermined time (step S10).

  When it is determined that the vehicle 1 is traveling straight on the slant road (step S30: YES), slant road dedicated assist torque control is performed (step S40).

  FIG. 6 is a diagram conceptually illustrating the assist torque control dedicated to the slant road.

  In FIG. 6, the controller 100 includes a basic assist torque setting unit 110, gain setting units 120 and 130, an additional friction torque setting unit 140, and gain setting units 150 and 160.

  The basic assist torque setting unit 110 sets the basic assist torque based on the vehicle speed V and the steering torque SWT. Here, the basic assist torque is a basic amount of assist torque that the motor 15 should apply to the pinion shaft 19. The basic assist torque setting unit 110 has a map that defines the relationship among the vehicle speed V, the steering torque SWT, and the basic assist torque, and sets the basic assist torque by referring to this map. For example, the basic assist torque setting unit 110 sets the basic assist torque to a larger value as the steering torque SWT is larger, and sets the basic assist torque to a larger value as the vehicle speed V is lower. The controller 100 corrects the basic assist torque set by the basic assist torque setting unit 110 based on gains Ga1 and Ga2 or additional friction torque described later, thereby assisting the motor 15 to apply to the pinion shaft 19. Set.

  The gain setting unit 120 sets the gain Ga1 according to the slope in the road width direction of the slant road on which the vehicle 1 travels straight (that is, the slant slope). The slant gradient is calculated based on the lateral G detected by the lateral G sensor 42. The gain setting unit 120 has a map Ma1 that defines the relationship between the slant gradient and the gain Ga1, and sets the gain Ga1 based on the map Ma1 and the slant gradient. Specifically, the gain setting unit 120 sets the gain Ga1 to a larger value as the slant gradient increases. The gain Ga1 is set to a value of 1 or more.

  The gain setting unit 130 sets the gain Ga2 in accordance with the road width (that is, the road width) of the slant road on which the vehicle 1 travels straight. The gain setting unit 130 has a map Ma2 that defines the relationship between the road width and the gain Ga2, and sets the gain Ga2 based on the map Ma2 and the road width. Specifically, the gain setting unit 130 sets the gain Ga2 to a larger value as the road width is narrower. Here, the width of the road on which the vehicle 1 travels straight can be specified based on the steering power P. For example, for a plurality of roads having mutually different road widths, an average value of the steering power P when the vehicle 1 travels straight ahead is acquired in advance by experiments or the like, and the relationship between the road width and the average value of the steering power P is shown. By creating a map, it is possible to specify the width of the road on the basis of the steering power P calculated during the travel.

  The additional friction torque setting unit 140 sets the additional friction torque based on the steering angle SWT and the vehicle speed V. The additional friction torque is a torque generated in the steering wheel 11 by simulating a frictional resistance generated in the steering system from the steering wheel 11 to the front wheel 5, and is a torque acting in a direction opposite to the steering direction of the steering wheel 11 by the driver. It is.

  Specifically, the additional friction torque setting unit 140 first obtains the friction torque Tt to be applied to the steering wheel 11 based on the steering angle SWA and the vehicle speed V. Next, the additional friction torque setting unit 140 obtains a target steering angle SWAta based on the steering angle SWA and the friction torque Tt. Next, the additional friction torque setting unit 140 obtains the additional friction torque Tc based on the deviation ΔSWA between the target steering angle SWAta and the steering angle SWA. That is, the additional friction torque setting unit 140 corrects the friction torque Tt based on the target steering angle SWAta and sets the corrected friction torque to the additional friction torque Tc.

  Here, the setting of the additional friction torque by the additional friction torque setting unit 140 will be described in detail with reference to FIGS.

  FIG. 7 is a diagram showing an example of a method for obtaining the friction torque Tt. FIG. 7 shows the steering angle SWA on the horizontal axis and the friction torque Tt on the vertical axis. More specifically, FIG. 7 corresponds to a map in which the friction torque Tt to be set with respect to the steering angle SWA according to the vehicle speed V is defined. In FIG. 7, as an example, a map corresponding to each of the high speed region V2, the medium speed region V1, and the low speed region V0 is shown. The additional friction torque setting unit 140 obtains the friction torque Tt corresponding to the current steering angle SWA and the vehicle speed V by referring to such a map.

  According to the map shown in FIG. 7, in the case of the same steering angle SWA, the friction torque Tt having a larger value is set as the vehicle speed increases. This is because, in the high speed region V2 and the medium speed region V1, it is preferable to generate a certain amount of friction torque from the viewpoint of improving the straight running stability and reducing the steering holding force and improving the stability at the time of steering. This is because at V0, if the friction torque is large, the driver may feel uncomfortable and the steering feeling may deteriorate. Further, according to the map shown in FIG. 7, when the vehicle speed is the same or in the same vehicle speed range, the friction torque Tt having a larger value is set as the steering angle SWA is larger. This is because when the steering angle SWA is large, the steered angle of the front wheels 5 is large, so that a large lateral force is likely to be generated, and from the viewpoint of reducing the holding force and improving the stability during steering holding, a greater friction This is because torque is required.

  Next, a method for obtaining the target steering angle SWAta from the friction torque Tt obtained as described above will be described. The additional friction torque setting unit 140 sets the deviation ΔSWA (= SWATA−SWA) between the target steering angle SWAta and the steering angle SWA and the deviation upper limit value Δ (= Tt / K) defined by the friction torque Tt and the gain K. Based on this, the target steering angle SWAta is obtained. Specifically, the additional friction torque setting unit 140 first initializes the target steering angle SWAta to SWA (not initialized if initialized), then obtains a deviation ΔSWA (= SWAta−SWA), and “ΔSWA> Δ ”, The target steering angle SWAta is changed to“ SWATA = SWA + Δ ”, and when“ ΔSWA <−Δ ”, the target steering angle SWAta is changed to“ SWATA = SWA−Δ ”, and“ −Δ When ≦ ΔSWA ≦ Δ ”, the target steering angle SWAta is not changed. The gain K is a value determined in consideration of the rigidity of the steering system, for example.

  Next, a method for obtaining the additional friction torque Tc from the target steering angle SWAta obtained as described above will be described. The additional friction torque setting unit 140 obtains the additional friction torque Tc from the deviation ΔSWA (= SWata−SWA) obtained from the target steering angle SWAta and the gain K (= Tt / Δ). Specifically, the additional friction torque setting unit 140 obtains the additional friction torque Tc from “Tc = K · ΔSWA”, that is, “Tc = K (SWAta−SWA)”.

  FIG. 8 is a diagram illustrating an example of the characteristic of the additional friction torque Tc. FIG. 8 shows the steering angle SWA on the horizontal axis and the additional friction torque Tc on the vertical axis (the counterclockwise torque direction is positive and the clockwise torque direction is negative). Here, the cases where the friction torque Tt is “Tt1” and “Tt2” (Tt2 <Tt1) are shown as examples. For example, the friction torque Tt1 when the vehicle speed is the high speed region V2 or the medium speed region V1 and the friction torque Tt2 when the vehicle speed is the low speed region V0 are shown (see FIG. 7). In FIG. 8, in both cases of “Tt1” and “Tt2”, for the sake of easy understanding, it is assumed for convenience that the target steering angle SWAt is the same and does not change according to the change of the steering angle SWA. When the target steering angle SWAt changes, the graph simply translates in the horizontal axis direction around the new target steering angle SWAta accordingly.

  As shown in FIG. 8, since the deviation upper limit value Δ is “Δ = Tt / K”, it increases as the friction torque Tt increases (for example, the deviation upper limit value Δ1 in the case of “Tt1” is “Tt2”). In this case, the deviation upper limit value Δ2 is larger). Further, in the range of “−Δ ≦ ΔSWA ≦ Δ”, the target steering angle SWAta is maintained without being changed, and “Tc = K · ΔSWA”, that is, “Tc = K (SWAta−SWA)”, the additional friction torque. The magnitude of Tc increases in proportion to the deviation ΔSWA. In the range of “ΔSWA> Δ” and “ΔSWA <−Δ”, the target steering angle SWAta is changed as described above and the magnitude of the deviation ΔSWA becomes constant, so that “Tc = K · ΔSWA”, that is, From “Tc = K (SWAta−SWA)”, the magnitude of the additional friction torque Tc becomes a constant value corresponding to the friction torque Tt. In this case, in the range of “−Δ ≦ ΔSWA ≦ Δ”, the friction torque Tt to be applied to the steering wheel 11 is not actually applied to the steering wheel 11, and the absolute value of the deviation ΔSWA is the deviation upper limit value Δ For the first time, the magnitude of the additional friction torque Tc is set to the magnitude of the friction torque Tt to be applied to the steering wheel 11. That is, the gain K is a parameter for determining the rising characteristic of the additional friction torque Tc (here, the ratio of the change in the additional friction torque Tc with respect to the deviation ΔSWA). The reason why the friction torque Tt is not applied in the range of “−Δ ≦ ΔSWA ≦ Δ” is to prevent the friction torque from varying and the steering feeling from deteriorating.

  FIG. 9 is an image diagram showing the characteristic of the additional friction torque Tc by a visible model. FIG. 9A is an image diagram corresponding to the range of “−Δ ≦ ΔSWA ≦ Δ”. In this case, the target steering angle SWAta does not change, and a force that balances the force T (for example, an external force generated due to input to the wheel), that is, a spring with a spring constant K (= gain K) An elastic force (= K · ΔSWA) when displaced by the displacement amount SWAta−SWA is generated. FIG. 9B is an image diagram corresponding to ranges of “ΔSWA> Δ” and “ΔSWA <−Δ”. In this case, the target steering angle SWAta changes in a direction to receive the force T, and a constant frictional force Tt ′ (<force T) is generated in a direction opposite to the force T. The frictional force Tt ′ corresponds to a value obtained by converting the frictional force Tt into a force.

  Returning to FIG. 6, the gain setting unit 150 sets the gain Gb1 according to the slant gradient of the slant road on which the vehicle 1 travels straight. The gain setting unit 150 has a map Mb1 that defines the relationship between the slant gradient and the gain Gb1, and sets the gain Gb1 based on the map Mb1 and the slant gradient. Specifically, the gain setting unit 150 sets the gain Gb1 to a larger value as the slant gradient increases. The gain Gb1 is set to a value of 1 or more.

  The gain setting unit 160 sets the gain Gb2 according to the width of the slant road on which the vehicle 1 travels straight. The gain setting unit 160 has a map Mb2 that defines the relationship between the road width and the gain Gb2, and sets the gain Gb2 based on the map Mb2 and the road width. Specifically, the gain setting unit 160 sets the gain Gb2 to a larger value as the road width is narrower.

  The controller 100 corrects the basic assist torque by multiplying the basic assist torque set by the basic assist torque setting unit 110 by gains Ga1 and Ga2. That is, the controller 100 sets the product of the basic assist torque set by the basic assist torque setting unit 110, the gain Ga1, and the gain Ga2 as the corrected basic assist torque.

  Further, the controller 100 corrects the additional friction torque by multiplying the additional friction torque set by the additional friction torque setting unit 140 by gains Gb1 and Gb2. That is, the controller 100 sets the product of the additional friction torque set by the additional friction torque setting unit 140, the gain Gb1, and the gain Gb2 as the corrected additional friction torque.

  Further, the controller 100 sets the sum of the corrected basic assist torque and the corrected additional friction torque as the assist torque (assist amount) that the motor 15 should apply to the pinion shaft 19. That is, the controller 100 multiplies the product of the basic assist torque set by the basic assist torque setting unit 110 and the gains Ga1 and Ga2, and the product of the additional friction torque set by the additional friction torque setting unit 140 and the gains Gb1 and Gb2. To set the assist torque.

  Particularly in the present embodiment, as described above, the gain Ga1 is set to a larger value as the slant gradient is larger by the gain setting unit 120, and the gain Ga2 is set to a larger value as the road width is narrower by the gain setting unit 130. Is done. That is, the corrected basic assist torque (that is, the product of the basic assist torque set by the basic assist torque setting unit 110 and the gains Ga1 and Ga2) increases as the slant gradient increases or the road width decreases. Set to Therefore, the larger the slant gradient or the narrower the road width, the larger assist torque is applied from the motor 15 to the pinion shaft 19.

  Here, when the vehicle 1 travels straight on the slant road, a gravitational component toward the lower side of the slant gradient of the slant road (that is, the inclination in the road width direction) acts on the vehicle 1. The steering wheel 11 is held by applying a steering torque to the steering wheel 11 in the steering angle direction corresponding to the upper side of the gradient. If no countermeasure is taken, when the vehicle 1 travels straight on the slant road, the steering torque (that is, the steering torque) that the driver should apply to the steering wheel 11 to maintain the steering is generated in the vehicle 1. Due to the gravitational component toward the lower side of the slant gradient, the larger the slant gradient, the larger the slant gradient, so that the driver may have difficulty holding the steering wheel 11, that is, the steering feeling of the vehicle 1. May get worse. Furthermore, the steering feeling of the vehicle 1 becomes more important as the slant road width is narrower.

  However, according to the present embodiment, as described above, the greater the slant gradient or the narrower the road width, the greater assist torque is applied from the motor 15 to the pinion shaft 19. Therefore, when the vehicle 1 travels straight on the slant road, the driver can easily hold the steering wheel 11 (that is, can easily hold the steering wheel). That is, the driver's steering feeling can be improved.

  Further, in the present embodiment, as described above, the gain Gb1 is set to a larger value as the slant gradient is larger by the gain setting unit 150, and the gain Gb2 is set to a larger value as the road width is narrowed by the gain setting unit 160. Is set. That is, the corrected additional friction torque (that is, the product of the additional friction torque set by the additional friction torque setting unit 140 and the gains Gb1 and Gb2) increases as the slant gradient increases or the road width decreases. Set to That is, the assist torque is applied from the motor 15 to the pinion shaft 19 so that the larger the slant gradient or the narrower the road width, the greater the additional friction torque is generated in the steering wheel 11. Therefore, the driver can more easily hold the steering wheel 11 when the vehicle 1 travels straight on the slant road. That is, the driver's steering feeling can be further improved.

  In the present embodiment, the configuration in which both the basic assist torque and the additional friction torque are corrected according to the slant gradient and the road width is taken as an example. However, only one of the basic assist torque and the additional friction torque is slant gradient. And you may comprise so that it may correct | amend according to a road width. Even if comprised in this way, a driver | operator's steering feeling in the case of the vehicle 1 carrying out a straight drive on the slant road can be improved.

  In addition, in this embodiment, as described above with reference to FIGS. 3 and 4, the road width of the road on which the vehicle 1 travels is determined based on the steering power P. In other words, the road width of the road is specified based on the characteristic of the operation of the steering wheel 11 by the driver (that is, the steering characteristic of the driver). Therefore, the road width specified based on the steering power P reflects the steering characteristics corresponding to the driver's perceptual characteristics. Therefore, by controlling the assist torque in accordance with the road width specified based on the steering power P, steering control suitable for the driver's perceptual characteristics can be performed.

  Next, with reference to FIG. 10 to FIG. 12, a description will be given of effects by the assist torque control according to the present embodiment.

  FIG. 10 is a schematic diagram illustrating a state where the vehicle 1b according to the comparative example is traveling on the slant road 900. As illustrated in FIG. FIG. 10A is a view of a state in which the vehicle 1b is traveling on the slant road 900 as viewed from above the vehicle 1b. FIG. 10B is a view of the state in which the vehicle 1b is traveling on the slant road 900 as seen from the back side of the vehicle 1b. FIG. 10C conceptually shows the driver's steering feeling in a state where the vehicle 1b is traveling on the slant road 900. FIG.

  As shown in FIGS. 10A and 10B, when a vehicle 1b travels on a slant road 900 having a slope (gradient) having a high left side and a low right side, the vehicle 1b has a right side resulting from the slope of the slant road 900. Since a lateral force toward the vehicle acts, the vehicle 1b easily flows to the right side. For this reason, the driver of the vehicle 1b becomes burdensome to hold the steering wheel 11b (see FIG. 10C) in order to make the vehicle 1b travel straight ahead. In other words, as shown in FIG. 10C, in this case, when the driver of the vehicle 1b operates the steering wheel 11b in the right rotation direction corresponding to the right side, which is the lower side of the slant road 900, the steering wheel While the wheel 11b is felt light, when the steering wheel 11b is operated in the left rotation direction corresponding to the left side, which is the upper side of the slant road 900, the steering wheel 11b is felt heavy. In order to drive the vehicle 1b straight on the slant road 900, the driver of the vehicle 1b must apply the steering torque toward the left rotation direction to hold the steering wheel 11b. The larger the is, the greater the steering torque must be applied. Therefore, if no measures are taken, when the vehicle 1b travels straight on a slant road, for example, the vehicle 1b travels on a flat road (that is, a road having a relatively small or almost zero inclination in the road width direction). There is a possibility that the driver's steering feeling may be deteriorated as compared with the case of traveling straight ahead.

  FIG. 11 is a graph showing an example of the relationship between the steering torque applied to the steering wheel 11b by the driver of the vehicle 1b and the steering angle.

  In FIG. 11, the broken line L1 indicates an example of the relationship between the steering torque and the steering angle when the vehicle 1b travels straight on a flat road, and the solid line L2 indicates the steering torque when the vehicle 1b travels straight on the slant road 900. 2 shows an example of the relationship between the steering angle and the steering angle.

  When the driver holds the steering wheel 11b in a state where the steering angle SWA becomes the steering angle SWAe so that the vehicle 1b travels straight, the vehicle 1b travels on the slant road 900 more than on the flat road. However, it is necessary to apply a larger steering torque to the steering wheel 11b. That is, when the vehicle 1b travels straight on the slant road 900 (see the solid line L2), the steering torque SWT_B that the driver should apply to the steering wheel 11b so that the steering angle SWA becomes the steering angle SWAe is When traveling straight on the road (see broken line L3), the steering angle SWA is larger than the steering torque SWT_A that the driver should apply to the steering wheel 11b so that the steering angle SWA becomes the steering angle SWAe. Therefore, when the vehicle 1b travels straight on the slant road 900, the driver returns the steering wheel 11b (that is, the direction intended by the driver), compared to when the vehicle 1b travels straight on the flat road. The steering wheel 11b tends to rotate in the opposite direction). Further, the feeling of returning as if the steering wheel 11b is returned may become stronger as the road width of the road on which the vehicle 1b travels becomes narrower.

  FIG. 12 is a graph showing an example of the effect by the assist torque control according to the present embodiment. In FIG. 12, a thick line L3 shows an example of the relationship between the steering torque and the steering angle when the vehicle 1 according to the present embodiment travels straight on the slant road. The thick line L3 has a first thick line portion L3a and a second thick line portion L3b. The first thick line portion L3a indicates the relationship between the steering torque and the steering angle when the steering wheel 11 is turned back (that is, the steering wheel 11 is operated so that the steering angle SWA is reduced). An example is shown, and the second thick line portion L3b represents the steering torque and the steering angle when the steering wheel 11 is turned (that is, the steering wheel 11 is operated so that the magnitude of the steering angle SWA is increased). An example of the relationship is shown.

  As shown in FIG. 12, according to the assist torque control according to the present embodiment, as described above, when the vehicle 1 travels on the slant road, the larger the slant gradient, the larger the basic assist torque is generated. Thus, since the assist torque is applied from the motor 15 to the pinion shaft 19 so that a larger additional friction torque is generated, the driver applies the steering wheel 11 so that the steering angle SWA becomes the steering angle SWAe. The steering torques SWT_Ca and SWT_Cb to be made can be made smaller than the steering torque SWT_B according to the comparative example. Note that the steering torque SWT_Ca is a steering torque that should be applied to the steering wheel 11 when the driver performs the switchback operation of the steering wheel 11 (see the solid line L3a). The steering torque SWT_Cb is a steering torque to be applied to the steering wheel 11 when the driver performs a cutting operation of the steering wheel 11 (see the solid line L3b).

  Therefore, when the vehicle 1 travels straight on the slant road, the driver can easily hold the steering wheel 11. That is, the driver's steering feeling can be improved.

  As described above, according to the present embodiment, it is possible to improve the driver's steering feeling when the vehicle 1 travels straight on the slant road. Furthermore, steering control adapted to the driver's perceptual characteristics can be performed.

  The present invention is not limited to the above-described embodiments, and can be appropriately changed without departing from the spirit or concept of the invention that can be read from the claims and the entire specification. Moreover, it is included in the technical scope of the present invention.

  DESCRIPTION OF SYMBOLS 5 ... Front wheel, 11 ... Steering wheel, 12 ... Steering shaft, 13 ... Steering angle sensor, 14 ... Torque sensor, 15 ... Motor, 19 ... Pinion shaft, 41 ... Vehicle speed sensor, 42 ... Lateral G sensor, 43 ... Yaw rate sensor, DESCRIPTION OF SYMBOLS 100 ... Controller, 110 ... Basic assist torque setting part, 120, 130 ... Gain setting part, 140 ... Additional friction torque setting part, 150, 160 ... Gain setting part,

Claims (7)

A steering device that is mounted on a vehicle and steers steered wheels in response to an operation of a steering wheel by a driver,
First specifying means for specifying a road width of a road on which the vehicle travels based on an operation amount by which the driver operates the steering handle;
Second specifying means for specifying the inclination of the road in the road width direction;
A steering device comprising: control means for controlling an assist torque for assisting steering of the vehicle by the driver based on the specified road width and the specified inclination. The first specifying means specifies the road width as one of a narrow road width and a wide road width,
The said control means makes the said assist torque larger when the specified road width is the narrow road width than when the specified road width is the wide road width. Steering device.   The steering device according to claim 1, wherein the control means increases the assist torque as the identified road width is narrower. The control means includes
First setting means for setting a basic assist torque that is a basis of the assist torque based on a steering torque applied to the steering wheel and a vehicle speed of the vehicle;
The steering apparatus according to any one of claims 1 to 3, further comprising: a first correction unit that corrects the set basic assist torque based on the specified road width and the specified inclination. The first correction means includes
The basic assist torque is such that the smaller the specified road width is, the larger the basic assist torque is, and the larger the specified inclination is, the larger the basic assist torque is. The steering apparatus according to claim 4, wherein torque is corrected. The control means includes
A second setting means for setting an additional friction torque simulating a frictional resistance based on a steering angle applied to the steering wheel and a vehicle speed of the vehicle;
Second correction means for correcting the set additional friction torque based on the specified road width and the specified slope;
The steering device according to any one of claims 1 to 5, wherein the assist torque is controlled so that the corrected additional friction torque is generated in the steering handle. The second correction means includes
The additional friction torque is such that the smaller the specified road width is, the larger the additional friction torque is, and the larger the specified inclination is, the larger the additional friction torque is. The steering apparatus according to claim 6, wherein torque is corrected.

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