JP5291640B2 - Steering device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To achieve steering that fits a feeling of a driver without deteriorating stability of the driver. <P>SOLUTION: According to a map indicating a relation of a predetermined vehicle speed and a yaw angular velocity gain, a target value of the yaw angular velocity gain is calculated and a steering gear ratio is controlled. Accordingly, a direction of a target arrival point after a predetermined forward gaze time on a target course along which the vehicle travels and a direction of a reference point of a handle seen from the driver's point of view are matched. In a low vehicle speed area, the direction of the target arrival point on a parting line of the forward gaze from the driver is matched to the direction of the reference point of the handle. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a steering device, and more particularly to a steering device that realizes a relationship between a steering angle of a steering wheel and a yaw angular velocity.

  Conventionally, based on experimental data, “When driving into a corner, the driver is gazing at a point that should be reached after about 1.2 seconds on the target route regardless of the vehicle speed.” A technique for setting the steering gear ratio so that the angle formed by the viewpoint is proportional to the steering wheel angle is known (Non-Patent Document 1).

  At low speeds, pay attention to the fact that the vehicle traveling direction and the vehicle forward direction differ by the vehicle body slip angle, and the line-of-sight deflection angle is obtained by adding the vehicle body slip angle to the angle formed by the current vehicle traveling direction and the gazing point. A technique for setting the steering gear ratio so that is proportional to the steering wheel angle is known (Patent Document 1).

Yasuo Shimizu et al., “Steering system in which gear ratio changes as a function of vehicle speed and steering angle and its effect”, Japan Society for Automotive Engineers, Preprint of Scientific Lecture, No. 21-99, 1999

JP 2001-151133 A

  However, the above Non-Patent Document 1 only discloses the “proportional steering gear ratio”, and does not disclose a specific setting method such as a proportional gain. If the gear ratio is too small, There is a problem that the steering angle is too large and quick, and the stability of driving decreases.

  Further, in the technique described in Patent Document 1, since the vehicle body slip angle is taken into account, the yaw angular velocity gain at low speed (gain from the steering angle to the yaw angular velocity) is lowered, and the gear ratio becomes too quick. However, the yaw angular velocity gain in the very low speed region is not sufficiently suppressed by considering only the vehicle body slip angle, the gear ratio becomes too quick, and the driving stability is reduced. There is a problem that.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a steering device that can perform steering in accordance with a driver's feeling without deteriorating driving stability. .

  In order to achieve the above object, the steering device according to the present invention provides a target after a predetermined forward gaze time on a target course on which the vehicle travels, as viewed from the driver's viewpoint, in a region where the vehicle speed is a predetermined value or more. The direction of the arrival point corresponds to the direction of the reference position of the handle, and in the region where the vehicle speed is less than the predetermined value, the direction of the target arrival point on the parting line of the front view from the driver, and the direction of the reference position of the handle The relationship between the steering angle of the steering wheel and the yaw angular velocity generated in the vehicle, which is determined in advance so as to correspond to each other, is realized.

  According to the steering apparatus according to the present invention, by realizing a relationship between a predetermined steering angle of the steering wheel and a yaw angular velocity generated in the vehicle, in a region where the vehicle speed is equal to or higher than a predetermined value, as viewed from the driver's viewpoint, The direction of the target arrival point after a predetermined forward gazing time on the target course on which the vehicle travels is made to correspond to the direction of the reference position of the steering wheel, and the front view from the driver in an area where the vehicle speed is less than a predetermined value. The direction of the target reaching point on the parting line is made to correspond to the direction of the reference position of the handle.

  In this way, in the region where the vehicle speed is equal to or higher than the predetermined value, the direction of the target arrival point after the forward gaze time corresponds to the direction of the reference position of the steering wheel, and in the region where the vehicle speed is less than the predetermined value, the target on the parting line By realizing the relationship between the steering angle determined to match the direction of the arrival point and the direction of the reference position of the steering wheel and the yaw angular velocity generated in the vehicle, without reducing the stability of driving Steering that matches the driver's feeling can be performed.

  In the steering apparatus according to the present invention, the relationship between the steering angle of the steering wheel and the yaw angular velocity generated in the vehicle is a yaw angular velocity gain from the steering angle of the steering wheel to the yaw angular velocity generated in the vehicle, and a predetermined yaw angular velocity gain and The relationship with the vehicle speed can be realized.

  In the relationship between the yaw angular velocity gain and the vehicle speed according to the present invention, the yaw angular velocity gain is proportional to the vehicle speed in a region where the vehicle speed is less than a predetermined value, and the yaw angular velocity gain is Only the constant term has a negative coefficient, and the other numerator and denominator terms have values calculated by a function of vehicle speed, which is a first-order rational function having a positive coefficient. Can be determined.

  The relationship between the yaw angular velocity gain and the vehicle speed according to the present invention is such that, in a region where the vehicle speed is less than a predetermined value, the relative depression angle between the depression angle from the driver to the center of the steering wheel and the depression angle from the front view to the parting line is viewed from the driver. As a factor, the yaw angular velocity gain is calculated by dividing the half of the distance between the road surface position on the parting line of the forward field of view and the driver position by the sum of the distance between the vehicle center of gravity and the rear axle. The product of the coefficient and the vehicle speed can be determined.

  The steering apparatus according to the present invention can realize the relationship between the steering angle of the steering wheel and the yaw angular velocity according to the steering gear ratio of the vehicle.

  The forward gaze time can be set to 2.5 seconds to 3.5 seconds.

  Said predetermined value can be made into the vehicle speed when the target arrival point after the front gaze time is located on the parting line of the front view from a driver.

  A steering apparatus according to the present invention is configured to detect a vehicle speed of a vehicle, a vehicle speed detected by the vehicle speed detection means, and a yaw angular velocity gain based on a relationship between a steering angle and a yaw angular velocity of a predetermined steering wheel. The yaw angular velocity gain calculating means for calculating and the control means for controlling the steering gear ratio so as to realize the yaw angular velocity gain calculated by the yaw angular velocity gain calculating means can be configured.

  The steering device according to the present invention determines a target yaw angular velocity based on a vehicle speed detecting means for detecting a vehicle speed of the vehicle, a vehicle speed detected by the vehicle speed detecting means, and a relationship between a predetermined steering angle and yaw angular velocity. The yaw angular velocity calculating means for calculating and the control means for controlling the steering gear ratio so as to realize the target yaw angular velocity calculated by the yaw angular velocity calculating means can be configured.

  As described above, according to the steering device of the present invention, in the region where the vehicle speed is equal to or higher than the predetermined value, the direction of the target arrival point after the forward gaze time corresponds to the direction of the reference position of the steering wheel, and the vehicle speed is To realize the relationship between the steering angle of the steering wheel and the yaw angular velocity generated in the vehicle so as to correspond to the direction of the target reaching point on the parting line and the direction of the reference position of the steering wheel in an area below the predetermined value Thus, it is possible to obtain an effect that steering suitable for the driver's feeling can be performed without deteriorating driving stability.

1 is a schematic diagram showing a configuration of a vehicle steering apparatus according to a first embodiment of the present invention. It is a block diagram which shows the structure of the computer of the vehicle steering apparatus which concerns on the 1st Embodiment of this invention. It is an image figure which shows the deflection angle of the advancing direction of a vehicle, and the direction of a target arrival point. (A) The image figure which shows a relative depression angle, (B) The image figure which shows the declination of the vehicle front-back direction and the direction of a target arrival point. (A) Image diagram showing how the driver's head has moved, (B) Image diagram showing the distance between the driver's head and the handle center, and (C) Steering angle of the handle when the driver's head has moved It is an image figure which shows the relationship between a front gaze angle and a relative depression angle. (A) The figure for demonstrating the relative depression angle of a handle | steering-wheel center depression angle and a parting line depression angle, and (B) The image figure which shows the case where a front gaze point exists above a parting line. It is a graph which shows the relationship between a vehicle speed and a yaw angular velocity gain. It is a flowchart which shows the content of the gear ratio control processing routine of the vehicle steering apparatus which concerns on the 1st Embodiment of this invention. It is a graph which shows the relationship between the vehicle speed in the case of the 1st Embodiment of this invention, and the case of a fixed gear ratio, and a yaw angular velocity gain. It is a block diagram which shows the structure of the computer of the vehicle steering apparatus which concerns on the 2nd Embodiment of this invention. It is a graph which shows the relationship between the vehicle speed and yaw angular velocity gain in 4WD and 2WD. It is the schematic which shows the structure of the vehicle steering apparatus which concerns on the 4th Embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the present embodiment, a case where the present invention is applied to a vehicle steering apparatus that is mounted on a vehicle and controls the steering gear ratio of the vehicle will be described as an example.

  As shown in FIG. 1, in the vehicle steering apparatus 10 according to the first embodiment, a steering gear ratio variable mechanism 16 is connected to a rotating shaft 14 that is interlocked with a steering wheel 12. An output shaft 18 protrudes from the steering gear ratio variable mechanism 16, and a pinion 20 connected to the output shaft 18 meshes with a rack shaft 22 connected to a steering wheel (not shown).

  Therefore, the rotation of the steering wheel 12 is transmitted to the pinion 20 via the steering gear ratio variable mechanism 16, and the rack shaft 22 moves in the axial direction (arrow W direction in FIG. 1), so that the steered wheels are steered. It is supposed to be.

  The steering gear ratio variable mechanism 16 is connected to the computer 24. The steering gear ratio variable mechanism 16 has a conventionally well-known structure, and changes the steering gear ratio of the steering gear ratio variable mechanism 16 based on a gear ratio command signal output from the computer 24. .

  As shown in FIG. 2, the computer 24 is connected to a vehicle speed sensor 26 that detects the vehicle speed of the host vehicle.

  The computer 24 includes a CPU, a RAM, and a ROM that stores a program for executing a gear ratio control processing routine to be described later, and is functionally configured as follows. The computer 24 stores the map indicating the relationship between the vehicle speed and the yaw angular velocity gain in advance, and the target yaw angular velocity gain according to the map stored in the map storage device 30 based on the vehicle speed from the vehicle speed sensor 26. A yaw gain calculating means 32 for calculating a value, a gear ratio calculating means 34 for calculating a steering gear ratio for realizing a target value of the calculated yaw angular velocity gain, and a gear ratio command signal so as to change to the calculated steering gear ratio. And a gear ratio control means 36 for outputting.

  Next, the principle of this embodiment will be described.

  First, regarding the driver model, from the description in the specification of Japanese Patent Application No. 2009-9863, the deviation between the traveling direction of the vehicle and the direction of the target reaching point after a predetermined forward gaze time on the target course on which the vehicle travels is described. It is known that the forward gaze angle, which is an angle, and the yaw angular velocity after a certain time have a proportional relationship without depending on the vehicle speed.

That is, the driver operates the steering wheel from the deviation angle _θgaze (see FIGS. 3A and 3B) between the traveling direction of the vehicle (the direction of the velocity vector) and the direction of the target arrival point of the vehicle after the forward gaze time T. A predicted value r _pre of the yaw angular velocity as a vehicle motion predicted value realized by doing is calculated by the following equation (1).

However, k _r is the transfer gain from forward gaze angle theta _gaze to yaw velocity r, tau is the dead time. Here, the dead time τ is a time for matching the timing of the change of the vehicle motion and the timing of the change of the curvature of the traveling course, and is a predetermined time.

  The above equation (1) is a result indicating that the driver is operating the handle based on the forward gaze angle.

As a result of theoretical analysis, between the transfer gain k _r from forward fixed point time T _gaze and forward gaze angle theta _gaze to yaw velocity r, the relationship expressed by the following equation (2) is satisfied I know.

In the present embodiment, the forward gaze time _Tgaze is set as a fixed time of 2.5 seconds to 3.5 seconds.

Further, it is known that a relationship represented by the following expression (3) is established between the forward gaze time _Tgaze and the dead time τ.

  Since the driver operates the steering wheel based on the front gaze angle in this way, the direction of the front gaze, which is the driver's intention and is also the output of the vehicle motion in the sense of passing this position after the front gaze time In order to improve the sense of unity, operability, agility, etc. between the vehicle and the driver by matching the direction of the reference position of the handle, which is the driver's operation amount, as shown in FIG. It paid attention in the embodiment.

  By the way, although the forward gaze angle defined in FIGS. 3A and 3B is based on the traveling direction of the automobile, the driver is seated in order to match the relationship with the steering angle of the steering wheel. It is necessary to use the vehicle longitudinal direction as a reference. Therefore, in the present embodiment, as shown in the following formula (4), an angle obtained by adding a vehicle body slip angle to a front gaze angle (a vehicle front-rear direction and a predetermined front gaze time on a target course on which the vehicle travels) Let us consider matching the steering angle of the steering wheel (the relative angle between the reference position in the neutral position of the steering wheel and the current reference position of the steering wheel) with a deviation angle from the direction of the subsequent target arrival point.

Further, as shown in FIG. 4A, when the relative depression angle between the steering wheel center and the front gazing point is θ _z , the condition for the steering angle δ _sw to coincide with the direction of the gazing point is as follows (5) The formula is obtained.

In the above equation (5), it is considered that the handle angle is apparently cut back by the roll angle due to the roll motion. K _roll is a roll rate.

Incidentally, the forward fixed point time T _gaze, between the transfer gain k _r from forward gaze angle theta _gaze to the yaw angular velocity r, since the equation (2) of relation is established, the forward gaze angle theta _gaze, It is described by the following equation (6).

  Further, the vehicle body slip angle β is described by the following equation (7) from a linear model of vehicle motion.

  From the above formulas (6) and (7), the above formula (5) can be rewritten into the following formula (8).

Here, _Cr is the rear wheel cornering power, l is the wheel base, and l _r is the center-to-rear axle distance. M is the vehicle mass, and v is the vehicle speed.

By the way, the relationship of the above equation (8) is a relationship under the assumption that the viewpoint position of the driver does not change, but the driver posture, that is, the position of the viewpoint changes due to the influence of the lateral acceleration when the vehicle is running. It is necessary to consider what to do. 5 the head of the proportional drivers lateral acceleration of the vehicle as shown in (A) is h _y moves in a direction against the lateral acceleration, the center of the handle as seen from the driver, by the following equation (9) It moves outward by the required θ _d .

Here, h _x is the distance between the driver's head and the center of the handle (see FIG. 5B).

Accordingly, from FIG. 5C, the condition for the direction of the steering angle δ _sw when the driver head is moved (the direction of the reference position of the steering wheel) to coincide with the direction of the forward gazing point is the following equation (10) It is represented by

In the present embodiment, θ _d is formulated as shown in the following equation (11), _assuming that h _y = _{hy max} moves when the lateral acceleration is generated at 9.8 [m / s ² ].

  Furthermore, the relationship between the lateral acceleration and the yaw angular velocity (conditions for preventing the slip angle from increasing) is expressed by the following equation (12).

  Taking the above equations (11) and (12) into consideration, a relational expression represented by the following equation (13) is derived.

Further, the relative depression angle θ _z has a relationship expressed by the following expression (14) based on the steering wheel center depression angle θ _zsw from the driver's viewpoint to the steering wheel center, the forward gaze time T _gaze and the eye point height h _eye. To do.

  From the above equation (14), the above equation (13) can be described by the following equation (15).

  Here, assuming a small steering angle region where the steering angle of the steering wheel is 10 degrees or less, a yaw angular velocity gain k that is a gain from the steering angle of the steering wheel to the yaw angular velocity is approximately derived as in the following equation (16). Is done.

  The above equation (16) is a function of vehicle speed that is a rational function of the first-order second order in which only the constant term of the numerator has a negative coefficient, and the other term of the numerator and the denominator term have a positive coefficient. Represents.

Note that, as shown in FIG. 6B, the above equation (16) is established only in the vehicle speed region in which the forward gazing point corresponding to the forward gazing time T _gaze exists above the parting line in the forward visual field from the driver. To do. In a vehicle speed region lower than the vehicle speed, the driver cannot see the front gazing point corresponding to the forward gazing time T _gaze , and performs steering on the basis of visual information above the parting line.

  Therefore, in this vehicle speed region, assuming a forward gazing point on the parting line, the yaw angular velocity gain that matches the direction of the predicted arrival point (front gazing point on the parting line) with the direction of the reference position of the steering wheel Ask for.

Here, the vehicle speed v ₀ when the predicted arrival point (target arrival point on the target course) after the forward gaze time T _{gaze is} on the parting line in the forward visual field from the driver is the parting line depression angle θ _zfview (FIG. _6A )) And eye point height h _eye can be described as the following equation (17).

Below the vehicle speed v ₀ expressed by the above equation (17), the following gaze time T _gaze in the above equation (16) can be replaced by the following equation (18) to be expressed by the following equation (19): The direction of the arrival prediction point (front gaze point on the parting line) disappearing to the parting line can be matched with the direction of the reference position of the handle.

  Note that since the above equation (19) is a relational expression used in a region where the speed is low, the square term of the vehicle speed in the denominator can be ignored, and the relational expression represented by the following expression (20): Can be approximated.

L _fview is the distance between the road surface position on the parting line of the forward view from the driver and the driver position.

  The above equation (20) indicates that the relative depression angle between the depression angle to the handle center viewed from the driver and the depression angle to the parting line of the front view is the road surface position and the driver position on the parting line of the front view seen from the driver. The yaw angular velocity gain is the product of the coefficient and the vehicle speed, with the value obtained by dividing the length of the distance between the vehicle center of gravity and the distance between the center of gravity of the vehicle and the rear axle as a coefficient.

  By setting the characteristics of the yaw angular velocity with respect to the steering angle of the steering wheel as described above, in the vehicle speed region where the forward gazing point is above the parting line in the forward visual field from the driver, the steering wheel reference viewed from the driver's viewpoint The direction of the position and the direction of the forward gazing point can be matched, and in the vehicle speed range lower than the vehicle speed range, the direction of the reference position of the steering wheel and the direction of the forward gazing point assumed on the parting line can be matched. Desirable vehicle motion characteristics are always obtained from a very low speed to a high speed range, and a sense of unity with the vehicle is improved. Further, in the very low speed region set on the parting line for the forward gazing point, the forward gazing time is a value inversely proportional to the vehicle speed by setting the vehicle arrival point a certain distance ahead as the forward gazing point regardless of the speed. This solves the problem that, unlike the conventional technology that assumes a constant forward gaze time, a yaw angular velocity gain proportional to the vehicle speed is realized by setting a forward gaze time proportional to the vehicle speed, and the gear ratio becomes too quick. To do.

  In this embodiment, in order to obtain a map showing the relationship between the yaw angular velocity gain k (yaw angular velocity gain from the steering angle of the steering wheel to the yaw angular velocity), which is the ratio of the yaw angular velocity and the steering angle of the steering wheel, and the vehicle speed v, In the vehicle speed region where the forward gazing point is above the parting line in the forward visual field from the driver, the yaw angular velocity gain is calculated based on the above equation (16), and in the vehicle speed region lower than the vehicle speed region, the above (20 ) To calculate the yaw angular velocity gain. As a result, a map showing the relationship between the yaw angular velocity gain k and the vehicle speed v as shown in FIG. 7 is obtained. Note that the equations in FIG. 7 simply describe the above equations (16) and (20) as a function of vehicle speed.

  Based on the principle described above, the map storage means 30 of the vehicle steering apparatus 10 according to the present embodiment stores a map that defines the relationship between the vehicle speed and the yaw angular velocity gain as shown in FIG. Yes.

  The yaw gain calculation means 32 calculates the target value of the yaw angular speed gain corresponding to the vehicle speed detected by the vehicle speed sensor 26 according to the map stored in the map storage means 30.

  Next, a control method for realizing a target yaw angular velocity gain calculated based on the map will be described.

The target yaw angular velocity gain is realized by actively changing the characteristic of the steering gear ratio variable mechanism 16 provided between the steering wheel and the mechanism that steers the actual steering angle of the front wheels according to the vehicle speed. If the dynamic characteristic of the vehicle motion is ignored between the actual steering angle δ _{f of the} front wheels and the yaw angular velocity r, a relationship represented by the following equation (21) is established.

Here, C _f is the front wheel cornering power. When the steering gear ratio between the steering angle δ _sw of the steering wheel and the actual steering angle δ _{f of the} front wheels is g _sw , the following relationship (22) is obtained.

The steering gear ratio g _sw for realizing the yaw angular velocity gain k calculated from the map shown in FIG. 7 by the equations (21) and (22) is expressed by the following equation (23).

  The gear ratio calculation means 34 calculates the steering gear ratio based on the target yaw angular velocity gain k calculated by the yaw gain calculation means 32 and the vehicle speed v detected by the vehicle speed sensor 26 according to the above equation (23). To do.

  The gear ratio control means 36 outputs a gear ratio command signal to the steering gear ratio variable mechanism 16 so as to change to the calculated steering gear ratio, thereby controlling the steering gear ratio.

  Next, the operation of the vehicle steering apparatus 10 according to the present embodiment will be described. A gear ratio control processing routine shown in FIG. 8 is executed in the computer 24 while the vehicle equipped with the vehicle steering device 10 is traveling.

  First, in step 100, the vehicle speed detected by the vehicle speed sensor 26 is acquired. In step 102, the target value of the yaw angular velocity gain is calculated from the vehicle speed acquired in step 100 according to the map stored in the map storage unit 30.

  In the next step 104, the steering gear for realizing the target value of the yaw angular velocity gain according to the above equation (23) from the vehicle speed acquired in step 100 and the target value of the yaw angular velocity gain calculated in step 102. Calculate the ratio. In step 106, a gear ratio command signal is output to the steering gear ratio variable mechanism 16 so as to change to the steering gear ratio calculated in step 104, the steering gear ratio is controlled, and the process returns to step 100.

  By repeatedly executing the above processing, the repeatedly calculated yaw angular velocity gain target values are realized.

  Next, the result of comparing the target characteristics of the vehicle speed and the yaw angular velocity gain in the present embodiment with those of the prior art will be described.

  In FIG. 9, the relationship between the vehicle speed and the yaw angular velocity gain is shown by comparing the characteristic when a vehicle with a fixed gear ratio is used as the prior art and the target characteristic proposed in the present embodiment. The control law of the above equation (23) is a gear ratio for changing the characteristic at the fixed gear ratio indicated by the broken line to the target characteristic indicated by the solid line. By setting the yaw angular velocity gain in this way, the direction of the forward gazing point on the predicted arrival trajectory (on the target course) and the direction of the reference position of the steering wheel are achieved. Smooth operation can be realized by the natural operation of “turning the steering wheel toward the vehicle”, and the evaluation of unity and operability with the vehicle can be improved. In addition, it is possible to reduce the correction steering due to excessive turning of the steering wheel or insufficient steering and improve the stability of the vehicle.

  As described above, according to the vehicle steering apparatus according to the first embodiment, in a region where the vehicle speed is equal to or higher than the predetermined value, the predetermined front on the target course on which the vehicle travels is viewed from the viewpoint of the driver. The direction of the target reaching point set on the parting line as seen from the driver's viewpoint in the area where the vehicle speed is less than the predetermined value while matching the direction of the target reaching point after the gaze time and the direction of the reference position of the steering wheel According to a map showing the relationship between the vehicle speed and the yaw angular velocity gain determined so that the direction of the steering wheel and the reference position of the steering wheel coincide with each other, the target value of the yaw angular velocity gain is calculated, and the steering gear ratio is controlled, thereby driving the vehicle. Without lowering the stability of the vehicle, it is possible to improve the sense of unity between the vehicle and the driver, and it is possible to perform steering in accordance with the driver's feeling.

  Also, focusing on the fact that the sense of unity with the vehicle is improved by matching the direction of the reference position of the steering wheel as seen from the driver with the direction of the forward gazing point, the direction of the forward gazing point visible from the driver and the reference of the steering wheel The yaw angular velocity gain is set so that the direction of the position (steering direction) matches. Further, when it is assumed that the forward gaze time is constant, the front gaze point is hidden by the front parting line from the driver at a very low speed. In such a very low speed range, the driver focuses on the point of gaze on the parting line as a result of trying to look as close as possible to the vehicle, and the front gazing point on the parting line, that is, the direction of the point where the vehicle will reach from now and the steering wheel The yaw angular velocity gain is set so as to match the direction of the reference position. By setting such a yaw angular velocity gain, desirable vehicle motion characteristics can be obtained from a very low speed to a high speed region, and the sense of unity with the vehicle is improved.

  Next, a vehicle steering apparatus according to a second embodiment will be described. In addition, about the part which becomes the structure similar to 1st Embodiment, the same code | symbol is attached | subjected and description is abbreviate | omitted.

  The second embodiment is different from the first embodiment mainly in that the target value of the yaw angular velocity is calculated and the steering gear ratio is controlled so as to realize the target value of the yaw angular velocity. Yes.

  As shown in FIG. 10, the computer 224 of the vehicle steering apparatus according to the second embodiment stores the map on the basis of the map storage means 30, the vehicle speed from the vehicle speed sensor 26 and the steering angle from the steering angle sensor 228. According to the map stored in the means 30, the yaw rate calculation means 232 for calculating the target value of the yaw angular velocity, the gear ratio calculation means 234 for calculating the steering gear ratio for realizing the calculated yaw angular velocity, the gear ratio control means 36, It has.

  The yaw rate calculation means 232 calculates a yaw angular speed gain corresponding to the vehicle speed detected by the vehicle speed sensor 26 according to the map stored in the map storage means 30, and is calculated by the calculated yaw angular speed gain and the steering angle sensor 228. Based on the steering angle of the steering wheel, a target value of the yaw angular velocity is calculated.

The gear ratio calculation unit 234 calculates the target yaw angular velocity r according to the above equation (21) based on the target yaw angular velocity r calculated by the yaw rate calculation unit 232 and the vehicle speed v detected by the vehicle speed sensor 26. The actual front wheel steering angle δ _f for realizing the above is calculated, and the calculated actual front wheel steering angle δ _f and the steering angle δ _sw of the steering wheel detected by the steering angle sensor 228, according to the above equation (22), Calculate the steering gear ratio.

  Next, a gear ratio control processing routine according to the second embodiment will be described.

  First, the vehicle speed detected by the vehicle speed sensor 26 and the steering angle of the steering wheel detected by the steering angle sensor 228 are acquired. And according to the map memorize | stored in the map memory | storage means 30, the target value of yaw angular velocity is calculated from the vehicle speed and steering angle which were acquired above.

  Next, the steering gear ratio for realizing the target value of the yaw angular velocity is calculated from the vehicle speed acquired above and the target value of the yaw angular velocity calculated above according to the above formulas (21) and (22). . Then, a gear ratio command signal is output to the steering gear ratio variable mechanism 16 so as to change to the steering gear ratio calculated above, the steering gear ratio is controlled, and the process returns to the first process.

  By repeatedly executing the above processing, the repeatedly calculated yaw angular velocity target values are realized.

  As described above, according to the vehicle steering apparatus according to the second embodiment, in a region where the vehicle speed is equal to or higher than the predetermined value, the predetermined front on the target course on which the vehicle travels is viewed from the viewpoint of the driver. The direction of the target reaching point set on the parting line as seen from the driver's viewpoint in the area where the vehicle speed is less than the predetermined value while matching the direction of the target reaching point after the gaze time and the direction of the reference position of the steering wheel According to a map showing the relationship between the vehicle speed and the yaw angular speed gain determined so as to match the direction of the reference position of the steering wheel, by calculating the target value of the yaw angular speed and controlling the steering gear ratio, The sense of unity between the vehicle and the driver can be improved without lowering the stability, and steering suitable for the driver's feeling can be performed.

  Next, a vehicle steering apparatus according to a third embodiment will be described. In addition, since the structure of the vehicle steering device which concerns on 3rd Embodiment becomes a structure similar to 1st Embodiment, it attaches | subjects the same code | symbol and abbreviate | omits description.

  The third embodiment is mainly different from the first embodiment in that the vehicle steering device is mounted on the rear wheel steering vehicle.

The rear wheel steering vehicle can freely set the characteristic of the vehicle body slip angle with respect to the yaw angular velocity by controlling the steering angle of the rear wheel. Therefore, in the third embodiment, for example, the above equation (7) indicating the characteristics of the yaw angular velocity and the lateral slip angle when the rear wheel is not steered is multiplied by a gain k _β (v) corresponding to the vehicle speed. The following equation (24) is substituted into the above equation (5).

  By performing the same arrangement as in the first embodiment, the target characteristic of the yaw angular velocity gain expressed by the following equations (25) and (26) can be obtained.

  As described above, in the present embodiment, in order to obtain a map showing the relationship between the yaw angular velocity gain k, which is the ratio of the yaw angular velocity and the steering angle of the steering wheel, and the vehicle speed v, the front gazing point is the front view from the driver. In the vehicle speed region existing above the parting line in FIG. 5, the yaw angular velocity gain is calculated based on the above equation (25), and in the vehicle speed region lower than the vehicle speed region, the yaw angular velocity gain is calculated based on the above equation (26). A map indicating the relationship between the yaw angular velocity gain k and the vehicle speed v is calculated and stored in the map storage means 30.

  In addition, about the other structure and effect | action of the vehicle steering apparatus which concern on 3rd Embodiment, since it is the same as that of 1st Embodiment, description is abbreviate | omitted.

  Next, the result of comparing the target characteristics of the vehicle speed and the yaw angular velocity gain in the third embodiment with those of a front wheel steering vehicle (2WS vehicle) will be described.

  FIG. 11 shows the vehicle speed and the target yaw angular velocity gain of the rear wheel steering vehicle when the rear wheel is controlled so that a vehicle body slip angle that is half the vehicle body slip angle generated in a vehicle that does not steer the rear wheel in all vehicle speed ranges is generated. It is the figure which showed the characteristic (refer the broken line of FIG. 11) compared with the case (refer the continuous line of FIG. 11) of 2WS vehicle. That is, it is a diagram showing the characteristics of the vehicle speed and the target yaw angular velocity gain in the rear wheel steering vehicle when the gain of the vehicle body slip angle is set as in the following equation (27), compared with the case of the 2WS vehicle.

  In the low speed region where the vehicle body slip angle is generated in the outward direction of the turn, the target value of the yaw angular velocity gain is increased as compared with the 2WS vehicle, and in the high speed region where the vehicle body slip angle is generated in the direction of the turn inward, the yaw is compared with the 2WS vehicle. By setting the target value of the angular velocity gain to be small, it is achieved that the direction of the forward gazing point on the arrival prediction locus coincides with the direction of the reference position of the handle. Accordingly, the driver can realize a smooth driving by a natural operation of “turning the steering wheel in a target direction that he or she wants to face”, and can improve evaluation of unity with the vehicle and operability.

  Next, a vehicle steering apparatus according to a fourth embodiment will be described. In addition, about the part which becomes the structure similar to 1st Embodiment, the same code | symbol is attached | subjected and description is abbreviate | omitted.

  The fourth embodiment is mainly different from the first embodiment in that the steering gear ratio according to the vehicle speed is mechanically realized.

  As shown in FIG. 12, a vehicle steering apparatus 410 according to an embodiment of the fourth invention has a pinion 420 connected to a rotating shaft 14 that is linked to the steering wheel 12 connected to a steering wheel (not shown). Meshed with the rack shaft 22.

  Accordingly, the rotation of the steering wheel 12 is transmitted to the pinion 420 via the rotation shaft 14, and the steering wheel is steered by the rack shaft 22 moving in the axial direction (the direction of arrow W in FIG. 1). It has become.

  In the fourth embodiment, the structure of the vehicle is designed as follows.

  First, the following equation (28) is obtained from the above equations (21) and (22).

  Further, the following equation (29) is established between the yaw angular velocity and the steering angle of the steering wheel.

Then, according to the equations (28) and (29), the characteristic when the steering gear ratio is fixed (the vehicle speed dependence of the yaw angular velocity gain) is shown by the solid line in FIG. 7 described in the first embodiment. The vehicle design parameters l _f , C _f , l _r , C _r and the fixed steering gear ratio g _sw are calculated so as to approximate the relationship between the vehicle speed v and the yaw angular velocity gain k shown in FIG.

Design parameters l _f of the vehicle obtained, C _f, l _r, while designing the structure of a vehicle according to C _r, designing the pinion gear of the pinion 420 so as to realize the steering gear ratio g _sw fixed obtained.

  A vehicle equipped with the vehicle steering device 410 according to the present embodiment can achieve characteristics close to the target value of the yaw angular velocity gain according to the vehicle speed by the pinion gear of the pinion 420 and various sources of the vehicle.

  In the first to fourth embodiments, the case where the steering of the front wheels or the rear wheels is controlled has been described as an example. However, the present invention is not limited to this. You may make it control both steering.

DESCRIPTION OF SYMBOLS 10,410 Vehicle steering device 12 Steering wheel 16 Steering gear ratio variable mechanism 20, 420 Pinion 24, 224 Computer 26 Vehicle speed sensor 30 Map storage means 32 Yaw gain calculation means 34, 234 Gear ratio calculation means 36 Gear ratio control means 228 Steering angle sensor 232 Yaw rate calculation means

Claims (9)

  In a region where the vehicle speed is equal to or higher than a predetermined value, the direction of the target arrival point after a predetermined forward gaze time on the target course on which the vehicle travels is associated with the direction of the reference position of the steering wheel as viewed from the driver's viewpoint In addition, in the region where the vehicle speed is less than a predetermined value, the steering angle of the steering wheel, which is determined in advance so as to correspond the direction of the target reaching point on the parting line of the forward view from the driver and the direction of the reference position of the steering wheel A steering device that realizes a relationship with a yaw angular velocity generated in a vehicle. The relationship between the steering angle of the steering wheel and the yaw angular velocity generated in the vehicle is a yaw angular velocity gain from the steering angle of the steering wheel to the yaw angular velocity generated in the vehicle,
The steering apparatus according to claim 1, wherein a predetermined relationship between the yaw angular velocity gain and the vehicle speed is realized. The relationship between the yaw angular velocity gain and the vehicle speed is
In the region where the vehicle speed is less than the predetermined value, the yaw angular velocity gain is proportional to the vehicle speed, and in the region where the vehicle speed is equal to or greater than the predetermined value, the yaw angular velocity gain has a negative coefficient only in the numerator constant term, and 3. The steering apparatus according to claim 2, wherein the other term and the denominator term are determined to be values calculated by a function of vehicle speed, which is a rational function of the second-order linear having a positive coefficient.     The relationship between the yaw angular velocity gain and the vehicle speed is such that, in a region where the vehicle speed is less than a predetermined value, the relative depression angle between the depression angle to the handle center viewed from the driver and the depression angle to the parting line of the front view is the front view seen from the driver. The yaw angular velocity gain is calculated by dividing the length of half the distance between the road surface position on the parting line and the driver's position by the sum of the distance between the center of gravity of the vehicle and the rear axle as a coefficient. The steering apparatus according to claim 3, wherein the steering apparatus is determined to be a product of a vehicle speed and a vehicle speed.   The steering apparatus according to any one of claims 1 to 4, wherein a relationship between a steering angle of the steering wheel and a yaw angular velocity is realized by a steering gear ratio of the vehicle.   The steering apparatus according to any one of claims 1 to 5, wherein the forward gaze time is 2.5 seconds to 3.5 seconds.   The steering apparatus according to any one of claims 1 to 6, wherein the predetermined value is a vehicle speed when a target arrival point after the forward gazing time is located on a parting line of a forward view from a driver. Vehicle speed detecting means for detecting the vehicle speed of the vehicle;
A yaw angular speed gain calculating means for calculating a yaw angular speed gain based on the vehicle speed detected by the vehicle speed detecting means and the predetermined relationship between the steering angle of the steering wheel and the yaw angular speed;
Control means for controlling the steering gear ratio so as to realize the yaw angular speed gain calculated by the yaw angular speed gain calculating means;
The steering apparatus according to claim 1, comprising: Vehicle speed detecting means for detecting the vehicle speed of the vehicle;
Yaw angular velocity calculating means for calculating a target yaw angular velocity based on the vehicle speed detected by the vehicle speed detecting means and the predetermined relationship between the steering angle of the steering wheel and the yaw angular velocity;
Control means for controlling the steering gear ratio so as to realize the target yaw angular speed calculated by the yaw angular speed calculating means;
The steering apparatus according to claim 1, comprising:

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