JP4850435B2 - Vehicle steering control device - Google Patents

Description

  The present invention relates to a steering control device for a vehicle of a steering mechanism using a so-called steer-by-wire system in which a relationship between a steering angle of a steering wheel and a turning angle of a steered wheel can be arbitrarily set.

  In general, the steering reaction force is very important as information from the vehicle to the driver. This is presumably because the driver judges the ground contact state of the front tire by the steering reaction force. Actually, the reaction force of the steering in a vehicle without power steering is the magnitude obtained by dividing the tire self-aligning torque by the steering gear ratio, and the self-aligning torque varies greatly due to the influence of the road surface μ between the road surface and the tire. It is known to do.

For example, in Japanese Patent Application Laid-Open No. 2004-130965, the front wheel slip angle is estimated from the yaw rate, lateral acceleration, rudder angle, and vehicle speed, and based on the front wheel slip angle, the load movement of the vehicle and the change in the road surface μ are considered. Techniques for performing various corrections and estimating self-aligning torque are disclosed.
JP 2004-130965 A

  On the other hand, the self-aligning torque estimated in the above-described Patent Document 1 also changes when a driving force and a braking force are applied to the front wheels. Therefore, when a differential limiting device is attached to the front wheel or when the yaw moment control is operated by the braking force control device, the self-aligning torque does not necessarily reflect the ground contact state between the road surface and the tire. Must not. Even though the vehicle limit is improved by these devices, this information is not reflected in the self-aligning torque, so it is difficult for the driver to grasp the vehicle limit and it is difficult to determine how far the vehicle can turn. This makes vehicle control particularly difficult near the limits. Further, in Patent Document 1 described above, the steering reaction force of the steering mechanism by the steer-by-wire method is applied based on the self-aligning torque estimated as described above. Therefore, the responsiveness is inferior, and there is a possibility that an accurate value cannot be obtained.

  The present invention has been made in view of the above circumstances, and even when various vehicle behavior controls are activated, the driver can accurately grasp the vehicle limit with good response, and can easily perform vehicle control. An object of the present invention is to provide a steering control device.

The present invention provides an operation force detection for detecting a force acting on each wheel of a vehicle in a vehicle steering control device having a steering mechanism capable of arbitrarily setting a relationship between a steering amount of a steering wheel and a steering wheel turning amount. Means, yaw moment calculating means for calculating the yaw moment acting on the vehicle based on the force acting on each wheel, and lateral force calculating for calculating the lateral force acting on the vehicle based on the force acting on each wheel Means, and at least the yaw moment and the lateral force as parameters , obtain an equivalent lateral force generated in the steered wheel when the yaw moment and the lateral force are generated by a steering operation, and according to the equivalent lateral force The steering reaction force calculating means for calculating the steering reaction force and the steering reaction force generating means for generating the steering reaction force in the steering are provided.

  The vehicle steering control device according to the present invention makes it possible for the driver to accurately grasp the vehicle limit with good response even when various vehicle behavior controls are activated, and to facilitate vehicle control.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
1 and 2 show a first embodiment of the present invention. FIG. 1 is a configuration diagram of a vehicle provided with a steer-by-wire steering mechanism, and FIG. 2 is a functional block diagram of a steering control device.

  In FIG. 1, reference numeral 1 denotes a vehicle such as an automobile. The vehicle 1 includes a steering mechanism 2 of a steer-by-wire electric power steering device, a steering control device 3 for controlling the steering mechanism 2, and a yaw moment control. A braking force control device 4 is mounted.

  The steering mechanism 2 includes a steering mechanism unit 5 that performs steering input from a driver, and a steering mechanism unit 6 that steers the front wheels 7fl and 7fr that are steered wheels, and these are controlled in conjunction with each other. A so-called steer-by-wire type electric power steering apparatus is realized.

  The steering mechanism unit 5 includes a steering handle 8, a steering shaft 9 connected to the steering handle 8, and a reaction force motor 10 as a steering reaction force generating means that is coaxially incorporated in the middle of the steering shaft 9. Configured. The reaction force motor 10 is driven and controlled by a steering control device 3 described later, and the driving force of the reaction force motor 10 is transmitted to the steering handle 8 via the steering shaft 9.

  The steered mechanism 6 includes a rack shaft 11 that extends in the left-right direction of the vehicle body, and knuckle arms 13fl and 13fr that are connected to both ends of the rack shaft 11 via tie rods 12fl and 12fr, respectively. The front wheels 7fl and 7fr are connected to the knuckle arms 13fl and 13fr, respectively.

  The rack shaft 11 is supported via a housing 14 so as to be movable in the left-right direction of the vehicle body. A rack gear 15 is provided on the rack shaft 11, and a pinion gear 16 is engaged with the rack gear 15. Further, a pinion shaft 17 is connected to the pinion gear 16, and a steering motor 18 is coaxially incorporated in the middle of the pinion shaft 17. The steered motor 18 is driven and controlled by the steering control device 3, and the driving force of the steered motor 18 is transmitted to the rack shaft 11 via the pinion shaft 17, the pinion gear 16, and the rack gear 15 to roll the front wheels 7fl and 7fr. Rudder.

  In the figure, reference numeral 19 denotes a clutch mechanism portion interposed between the steering shaft 9 and the pinion shaft 17, and this clutch mechanism portion 19 is provided when the reaction force motor 10 or the steering motor 18 fails (failure). Etc.) and the steering control is performed by the steering control device 3.

  On the other hand, reference numeral 20 denotes a brake drive unit of the vehicle, and a master cylinder (not shown) connected to a brake pedal operated by a driver is connected to the brake drive unit 20. When the driver operates the brake pedal, the master cylinder introduces brake pressure to the wheel cylinders 21fl, 21fr, 21rl, 21rr of the four wheels 7fl, 7fr, 7rl, 7rr through the brake drive unit 20, thereby The brakes are applied to the brakes.

  The brake drive unit 20 is a hydraulic unit including a pressurizing source, a pressure reducing valve, a pressure increasing valve, and the like. In addition to the brake operation by the driver described above, each brake driving unit 20 is configured according to an input signal from a braking force control device 4 described later. A brake pressure can be introduced independently to each of the wheel cylinders 21fl, 21fr, 21rl, and 21rr.

Next, each sensor mounted on the vehicle 1 will be described.
In the vehicle 1, wheel speed sensors 25fl, 25fr, 25rl, 25rr for detecting wheel speeds ωfl, ωfr, ωrl, ωrr of each wheel, and axle housings 26fl, 26fr, 26rl, 26rr of each wheel are embedded in each wheel. Acting force detection sensors 27fl, 27fr, 27rl, 27rr for detecting the acting force, rudder angle sensor 28 for detecting the steering angle δf, stroke position sensor 29 for detecting the stroke position SR of the rack shaft 11, and yaw rate (dφ / dt) Is provided.

  The wheel speeds ωfl, ωfr, ωrl, ωrr detected by the wheel speed sensors 25fl, 25fr, 25rl, 25rr are input to the steering control device 3 and the braking force control device 4.

  Further, the acting force detection sensors 27fl, 27fr, 27rl, and 27rr are for acting force detecting means, and are, for example, sensors disclosed in Japanese Patent Laid-Open No. 9-2240. Hereinafter, each force in the x direction) and the left and right direction (hereinafter, y direction) is detected based on the amount of displacement generated in each axle housing 26fl, 26fr, 26rl, 26rr. Specifically, Fflx and Ffly are applied from the acting force detection sensor 27fl, Ffrx and Ffry are applied from the acting force detection sensor 27fr, Frlx and Frly are applied from the acting force detection sensor 27rl, and Frrx and Frr are applied from the acting force detection sensor 27rr. Frry is input to the steering control device 3, respectively.

  Further, the steering angle δf detected by the steering angle sensor 28 is input to the steering control device 3 and the braking force control device 4, and the stroke position SR detected by the stroke position sensor 29 is input to the steering control device 3. The yaw rate (dφ / dt) detected by the yaw rate sensor 30 is input to the braking force control device 4.

  The braking force control device 4 to which the wheel speeds ωfl, ωfr, ωrl, ωrr, the steering angle δf, and the yaw rate (dφ / dt) of each wheel are input is based on the vehicle specifications, for example, yaw moment control as follows. To do.

  Calculates the differential value of the target yaw rate, the differential value of the predicted yaw rate for low-μ road driving, and the deviation of both differential values, and calculates the deviation between the actual yaw rate and the target yaw rate, and based on these values, the vehicle's understeer tendency Alternatively, a target braking force for correcting the oversteer tendency is calculated. Then, in order to correct the understeer tendency of the vehicle, the rear wheel in the turning direction is selected as the braking wheel to which the braking force is applied, and the front wheel in the turning direction is corrected as the braking wheel to apply the braking force. Is output and the target braking force is added to the selected wheel to control the braking force.

  Steering control in which wheel speeds ωfl, ωfr, ωrl, ωrr of each wheel, forces Fflx, Ffly, Ffrx, Ffry, Frlx, Frly, Frrx, Frry, steering angle δf, and stroke position SR acting on each wheel are input. The device 3 performs drive control (steer-by-wire control) on the reaction force motor 10 of the steering mechanism unit 5 and the steering motor 18 of the steering mechanism unit 6 based on the inputs of these sensors.

  In other words, the steering control device 3 is mainly composed of a microcomputer and its peripheral devices. As shown in FIG. 2, the vehicle speed calculation unit 3a, the yaw moment calculation unit 3b, the lateral force calculation unit 3c, and the front wheel side slip angle calculation unit 3d. The steering reaction force torque calculation unit 3e, the reaction force motor control amount calculation unit 3f, the steering angle control amount calculation unit 3g, and the steered motor control amount calculation unit 3h are mainly configured.

  The vehicle speed calculation unit 3a receives the wheel speeds ωfl, ωfr, ωrl, and ωrr of each wheel from the wheel speed sensors 25fl, 25fr, 25rl, and 25rr, and calculates the average of these, for example ((ωfl + ωfr + ωrl + ωrr) / 4). The vehicle speed V is calculated and output to the front wheel side slip angle calculation unit 3d and the steering angle control amount calculation unit 3g.

The yaw moment calculator 3b receives front and rear and left and right forces Fflx, Ffly, Ffrx, Ffry, Frlx, Frly, Frrx, Frry acting on each wheel from the acting force detection sensors 27fl, 27fr, 27rl, 27rr. . Then, the yaw moment Mz acting on the vehicle is calculated by the following equation (1), and this yaw moment Mz is output to the front wheel side slip angle calculation unit 3d and the steering reaction force torque calculation unit 3e. That is, the yaw moment calculator 3b is provided as a yaw moment calculator.
Mz = lf. (Ffly + Ffry) -lr. (Frly + Frry)
+ (Df / 2). (Ffrx-Fflx) + (dr / 2). (Frrx-Frlx) (1)
Here, lf is the length from the center of gravity position of the vehicle to the front axle, rr is the length from the center of gravity position of the vehicle to the rear axle, df is the tread of the front wheel, and dr is the tread of the rear wheel.

The lateral force calculator 3c receives lateral forces Ffly, Ffry, Frly, Frry acting on the wheels from the applied force detection sensors 27fl, 27fr, 27rl, 27rr. Then, the lateral force Fy acting on the vehicle is calculated by the following equation (2), and this lateral force Fy is output to the front wheel side slip angle calculating unit 3d and the steering reaction force torque calculating unit 3e. That is, the lateral force calculation unit 3c is provided as a lateral force calculation means.
Fy = Ffly + Ffry + Frly + Frry (2)

  The front wheel side slip angle calculator 3d receives the steering angle δf from the steering angle sensor 28, the vehicle speed V from the vehicle speed calculator 3a, the yaw moment Mz from the yaw moment calculator 3b, and the lateral force calculator 3c. Lateral force Fy is input.

Then, the side slip angle β of the vehicle body is calculated by the following equation (3), and the front wheel side slip angle βf is calculated by the following equation (4) using the vehicle body side slip angle β and is output to the steering reaction force torque calculating unit 3e. .
β = ∫ ((1 / V) · (Fy / m) −∫ (Mz / Iz) dt) dt (3)
Here, m is the vehicle mass, and Iz is the yaw moment of inertia.
βf = β + (lf / V) · ∫ (Mz / Iz) dt−δf (4)

The vehicle body side slip angle β and front wheel side slip angle βf use a sensor value (d ² y / dt ² ) from a lateral acceleration sensor (not shown) and a sensor value (dφ / dt) from a yaw rate sensor 30. The calculation may be performed by the following equations (5) and (6).
β = ∫ (((d ² y / dt ² ) / V) − (dφ / dt)) dt (5)
βf = β + (lf / V) · (dφ / dt) −δf (6)

  As described above, the front wheel side slip angle βf calculated by the front wheel side slip angle calculation unit 3d is derived based on the sensor information, and thus includes the effect of the vehicle behavior control device (the braking force control device 4 in the present embodiment). It becomes the value.

The steering reaction force torque calculator 3e receives the yaw moment Mz from the yaw moment calculator 3b, the lateral force Fy from the lateral force calculator 3c, and the front wheel side slip angle βf from the front wheel side slip angle calculator 3d. . First, assuming that the yaw moment Mz and the lateral force Fy are generated only by the steering operation, an equivalent front wheel lateral force Ffy is calculated by the following equation (7).
Ffy = (lr · Fy + Mz) / (lf + lr) (7)

Next, the steering reaction force torque Th is calculated by the following equation (8), and the steering reaction force torque Th is output to the reaction force motor control amount calculation unit 3f.
Th = Kh · (∂Ffy / ∂βf) (8)
Here, Kh is a constant set in advance in consideration of the steering gear ratio and the like.

  Thus, by calculating the steering reaction force torque Th, it is not affected by various vehicle behavior control devices (braking force control device 4 in the present embodiment), and the performance improvement by the various vehicle behavior control devices is improved. The reflected information is transmitted to the driver.

Further, since the steering reaction torque Th calculated in the above equation (8) is a value considering the front wheel side slip angle βf, it is simply compared with the steering reaction torque Th calculated by Th = Kh · Ffy. The change in lateral force can be transmitted to the driver in more detail. Thus, the steering reaction force torque calculator 3e functions as a steering reaction force calculator.
The reaction force motor control amount calculation unit 3f receives the steering reaction force torque Th from the steering reaction force torque calculation unit 3e, calculates the reaction force motor control amount based on the steering reaction force torque Th, and sets the reaction force motor 10 to Drive control.

  The steering angle control amount calculation unit 3g receives the steering angle δf from the steering angle sensor 28, the stroke position SR from the stroke position sensor 29, and the vehicle speed V from the vehicle speed calculation unit 3a. Then, the value of the transmission ratio Pw (= δf / θw) for transmitting the steering angle δf as the turning angle θw of the front wheels 7fl, 7fr as the steered wheels is set in advance according to the steering angle δf and the vehicle speed V. The transmission ratio Pw corresponding to the steering angle δf and the vehicle speed V is set with reference to the map. Thus, based on the set transmission ratio Pw and the steering angle δf, the steering angle δf is divided by the transmission ratio Pw, and the calculation result is set as the target stroke position SRt of the rack shaft 11. Then, based on the stroke position SR and the target stroke position SRt, for example, the steered control amount Tw for the steered motor 18 is obtained by the following equation (9), and is output to the steered motor control amount calculation unit 3h.

Tw = Kp · (SRt−SR) + Kd · (d (SRt−SR) / dt)
+ Ki · ∫ (SRt−SR) dt (9)
Here, Kp, Kd, and Ki are constants.

  The steered motor control amount calculating unit 3h receives the steered control amount Tw from the steered angle control amount computing unit 3g, calculates the steered motor control amount based on the steered control amount Tw, Drive control.

  As described above, according to the first embodiment, the yaw moment Mz obtained from the steering reaction force torque Th based on the force values from the acting force detection sensors 27fl, 27fr, 27rl, and 27rr, and the lateral force Fy. Therefore, even when various vehicle behavior controls (braking force control device 4 in the present embodiment) are activated, they are not affected by these, and the performance is improved by the various vehicle behavior control devices. The information reflecting the above is transmitted to the driver, so that the driver can accurately grasp the vehicle limit and can easily perform vehicle control.

  In addition, since the steering reaction force torque Th is calculated in consideration of the front wheel side slip angle βf in addition to the yaw moment Mz and the side force Fy, the change in the side force can be transmitted to the driver in more detail. It can be done.

  The steering reaction force torque Th is set based on the force values from the acting force detection sensors 27fl, 27fr, 27rl, and 27rr, not based on the estimated values obtained by a plurality of sensors. It is possible to set a value that is excellent and has a high accuracy with little error.

  Next, FIGS. 3 and 4 show a second embodiment of the present invention, FIG. 3 is a configuration diagram of a vehicle provided with a steering mechanism by a steer-by-wire system, and FIG. 4 is a functional block diagram of a steering control device. In the second embodiment, not only the steering reaction force is calculated based on the yaw moment and the lateral force, but also the steering reaction force can be calculated based on the yaw rate and the lateral acceleration. Unlike the first embodiment, the other components are the same as those in the first embodiment, so that the same reference numerals are used and description thereof is omitted.

Therefore, as shown in FIG. 3, the steering control device 50 according to the second embodiment has inputs from the sensors described in the first embodiment (the wheel speeds ωfl, ωfr, ωrl, ωrr, In addition to the forces Fflx, Ffly, Ffrx, Ffry, Frlx, Frly, Frrx, Fry, steering angle δf, stroke position SR) acting on each wheel, the yaw rate (dφ / dt) is input from the yaw rate sensor 30, and the lateral acceleration sensor Lateral acceleration (d ² y / dt ² ) is input from 51. A signal for the driver to select a desired steering reaction force torque characteristic is input by a steering mode changeover switch 52 as a steering reaction force selection means.

  As shown in FIG. 4, the steering control device 50 includes a vehicle speed calculation unit 3a, a yaw moment calculation unit 3b, a lateral force calculation unit 3c, a front wheel side slip angle calculation unit 3d, a steering reaction force torque calculation unit (the first embodiment). In the second embodiment, it is read as the first steering reaction force torque calculation unit: provided as first steering reaction force calculation means) 3e, reaction force motor control amount calculation unit 3f, steering angle control amount calculation unit 3g, steering motor In addition to the control amount calculation unit 3h, a second steering reaction torque calculation unit 50a is provided.

  The front wheel side slip angle βf calculated by the front wheel side slip angle calculation unit 3d is also output to the second steering reaction force torque calculation unit 50a in addition to the steering reaction force torque calculation unit 3e.

  In addition, when a selection or non-selection signal is input from the steering mode changeover switch 52 to the first steering reaction force torque calculation unit 3e and the selection signal is input, the first steering reaction force torque is calculated. The steering reaction force torque Th calculated by the torque calculation unit 3e is output to the reaction force motor control amount calculation unit 3f.

The second steering reaction force torque calculation unit 50a is provided as a second steering reaction force calculation unit. The yaw rate (dφ / dt) is input from the yaw rate sensor 30, and the lateral acceleration (d ² y / dt ² ), the front wheel side slip angle βf is input from the front wheel side slip angle calculation unit 3d, and a selection or non-selection signal is input from the steering mode changeover switch 52. Then, an equivalent front wheel lateral force Ffy is calculated by the following equation (10), and the steering reaction force torque Th is calculated by applying this equivalent front wheel lateral force Ffy to the above-described equation (8). When a selection signal is input from the changeover switch 52, the steering reaction force torque Th calculated by the second steering reaction force torque calculation unit 50a is output to the reaction force motor control amount calculation unit 3f.
Ffy = (lr · m · (d ² y / dt ² ) + Iz · (d ² φ / dt ² ))
/ (Lf + lr) (10)
The equivalent front wheel lateral force Ffy calculated by the equation (10) is the yaw rate (dφ / dt) from the yaw rate sensor 30 and the lateral acceleration (d ² y / dt ² ) from the lateral acceleration sensor 51. Therefore, the value includes the effects of various vehicle behavior controls (braking force control device 4 in the present embodiment).

  That is, information that does not appear as actual behavior is not reflected in the yaw rate (dφ / dt) from the yaw rate sensor 30. Therefore, for example, when steering or yaw moment control is performed on a narrow road or a split μ road, the front wheel steering information is not reflected as a steering reaction force. In addition, since the steering reaction force torque Th calculated by the second steering reaction force torque calculation unit 50a may be desirable when traveling straight ahead, the driver can select the vehicle according to the driving conditions. The switching between the steering reaction force torque calculated by the first steering reaction force torque calculation unit 3e and the steering reaction force torque Th calculated by the second steering reaction force torque calculation unit 50a is performed by a road surface μ estimation device (not shown). For example, it may be configured to be automatically selected.

  As described above, according to the second embodiment, in addition to the effects described in the first embodiment, it is possible to select the steering reaction force characteristic according to the preference of the driver, and more accurate information according to the driving state. The driver will be able to get.

  In the first and second embodiments of the present invention, the vehicle equipped with the braking force control device 4 is described as an example of vehicle behavior control. However, the present invention is not limited to this. The same effect can be obtained even in a vehicle equipped with a left / right driving force distribution control device that can control the driving force distribution.

The block diagram of the vehicle provided with the steering mechanism by a steer-by-wire system by 1st Embodiment of this invention Same as above, functional block diagram of steering control device The block diagram of the vehicle provided with the steering mechanism by a steer-by-wire system by 2nd Embodiment of this invention Same as above, functional block diagram of steering control device

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Vehicle 2 Steering mechanism of electric power steering device 3 Steering control device 3a Vehicle speed calculation unit 3b Yaw moment calculation unit (yaw moment calculation means)
3c Lateral force calculation unit (lateral force calculation means)
3d Front wheel side slip angle calculation unit 3e Steering reaction force torque calculation unit (steering reaction force calculation means)
3f Reaction force motor control amount calculation unit 3g Steering angle control amount calculation unit 3h Steering motor control amount calculation unit 4 Braking force control device 5 Steering mechanism unit 6 Steering mechanism unit 7fl, 7fr, 7rl, 7rr Wheel 8 Steering handle 9 Steering Shaft 10 Reaction force motor (steering reaction force generating means)
18 Steering motor 25fl, 25fr, 25rl, 25rr Wheel speed sensor 27fl, 27fr, 27rl, 27rr Acting force detection sensor (acting force detecting means)
28 Rudder angle sensor 29 Stroke position sensor 30 Yaw rate sensor

Claims (5)

In a vehicle steering control device having a steering mechanism that can freely set the relationship between the steering amount of a steering wheel and the steering wheel steering amount,
Acting force detection means for detecting the force acting on each wheel of the vehicle;
A yaw moment calculating means for calculating a yaw moment acting on the vehicle based on the force acting on each wheel;
Lateral force calculating means for calculating the lateral force acting on the vehicle based on the force acting on each wheel;
Using at least the yaw moment and the lateral force as parameters , an equivalent lateral force generated on the steered wheel when the yaw moment and the lateral force are generated by a steering operation is obtained, and a steering reaction corresponding to the equivalent lateral force is obtained. Steering reaction force calculating means for calculating force,
Steering reaction force generating means for generating the steering reaction force in the steering;
A vehicle steering control device comprising: In a vehicle steering control device having a steering mechanism that can freely set the relationship between the steering amount of a steering wheel and the steering wheel steering amount,
Acting force detection means for detecting the force acting on each wheel of the vehicle;
A yaw moment calculating means for calculating a yaw moment acting on the vehicle based on the force acting on each wheel;
Lateral force calculating means for calculating the lateral force acting on the vehicle based on the force acting on each wheel;
A first steering reaction force calculating means for calculating a steering reaction force using at least the yaw moment and the lateral force as parameters;
A second steering reaction force calculating means for calculating a steering reaction force using at least the yaw rate and the lateral acceleration as parameters ;
The first steering reaction force steering reaction force calculated by the calculating means and the second steering reaction force computation unit you selected in response to an input of either the selection signal of the calculated steering reaction force in the steering reaction force selection means When,
Steering reaction force generating means for causing the steering to generate a steering reaction force selected by the steering reaction force selection means;
A vehicle steering control device comprising:   3. The vehicle steering control device according to claim 1, wherein the steering reaction force is calculated based on a side slip angle of a steered wheel in addition to the parameter.   4. The vehicle steering control device according to claim 3, wherein the side slip angle of the steered wheel is calculated based on a vehicle speed, a steering angle, the yaw moment, and the lateral force.   4. The vehicle steering control device according to claim 3, wherein the side slip angle of the steered wheel is calculated based on a vehicle speed, a steering angle, a lateral acceleration, and a yaw rate.

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