JP4948794B2 - Vehicle steering control device - Google Patents

Description

The present invention relates to a steering rudder control apparatus for a vehicle for adding the front wheel steering angle by an electric motor or the like to the front wheel steering angle by the driver.

Conventionally, various techniques have been proposed for correcting the front wheel steering angle by the driver. For example, in Japanese Patent Application Laid-Open No. 2004-168166, the steering gear ratio is determined based on the sum of a proportional term that depends on the steering angle and a differential term that depends on the steering angular velocity, and the differential term is determined according to an increase in vehicle speed. Thus, there is disclosed a steering gear ratio variable type steering control device that shifts from a positive region to a negative region.
JP 2004-168166 A

  However, in the steering control in which the correction is made only by the vehicle speed and the front wheel steering angle by the driver as disclosed in Patent Document 1 described above, only the steering input of the driver according to the vehicle speed state at that time is corrected. There is a problem that it is insufficient in terms of suppressing unstable vehicle behavior due to resonance of yaw motion with respect to steering while improving yaw response.

  The present invention has been made in view of the above circumstances, and provides a vehicle steering control device capable of reliably suppressing unstable vehicle behavior due to resonance of yaw motion with respect to steering while improving the yaw response of the vehicle. For the purpose.

The present invention includes a front wheel steering angle correction unit that calculates a front wheel steering angle correction amount to be added to the input front wheel steering angle, and operates the front wheel steering angle correction mechanism to add the front wheel steering angle correction amount. In the steering control device for a vehicle, the front wheel steering angle correction unit is configured to multiply a value obtained by multiplying a vehicle slip angular velocity by a control gain calculated based on a change in a yaw rate gain with respect to a steering angle according to a vehicle speed. It is characterized by calculating as

  According to the vehicle steering control device of the present invention, it is possible to reliably suppress unstable vehicle behavior due to resonance of yaw motion with respect to steering while improving the yaw response of the vehicle.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
1 to 6 show a first embodiment of the present invention, FIG. 1 is an explanatory diagram showing a schematic configuration of a front wheel steering device for a vehicle, FIG. 2 is a functional block diagram of a steering control unit, and FIG. 3 is a steering control program. 4 is a characteristic diagram of the vehicle speed sensitive steering gear ratio, FIG. 5 is a characteristic diagram of the first control gain, and FIG. 6 is a characteristic diagram of the second control gain.

  In FIG. 1, reference numeral 1 denotes a front wheel steering device for a vehicle. In the front wheel steering device 1, a steering shaft 3 is extended from a steering wheel 2, and a front end of the steering shaft 3 includes universal joints 4 a, 4 a and It is connected to a pinion shaft 6 protruding from the steering gear box 5 through a joint portion 4 comprising a joint shaft 4b.

  From the steering gear box 5, a tie rod 8fl extends toward the left front wheel 7fl, while a tie rod 8fr extends toward the right front wheel 7fr.

  The tie rod ends of the tie rods 8fl and 8fr are connected to axle housings 10fl and 10fr that rotatably support the wheels 7fl and 7fr on the respective sides via knuckle arms 9fl and 9fr.

  A front wheel rudder angle correction mechanism 11 that varies the steering gear ratio is interposed in the middle of the steering shaft 3. The steering shaft 3 has an upper shaft that extends upward from the front wheel rudder angle correction mechanism 11. A shaft portion extending downward from the 3U front wheel steering angle correction mechanism 11 is configured as a lower shaft 3L.

  The structure of the front wheel steering angle correction mechanism 11 will be described below. A pair of sun gears 12U, 12L is fixed on the same rotational axis at the lower end of the upper shaft 3U and the upper end of the lower shaft 3L, and a plurality of (for example, three) sun gears 12U, 12L are provided. ) Meshed with planetary gears 14U and 14L fixed to the provided pinion shaft 13, respectively.

  The pair of sun gears 12U and 12L are both housed inside a carrier 15 that rotatably supports the pinion shaft 13, and a drive fixed to an output shaft 16a of the electric motor 16 is provided on the outer periphery of the upper end of the carrier 15. A driven gear 18 that meshes with the gear 17 is provided.

  The electric motor 16 is driven by the motor drive unit 21, and the motor drive unit 21 rotates the electric motor 16 based on a signal corresponding to the motor rotation angle input from the steering control unit 20 as the front wheel steering angle correction means. It is configured to let you.

  On the other hand, the vehicle is equipped with a vehicle behavior control device 40 as vehicle behavior control means for controlling the vehicle behavior. The vehicle behavior control device 40 is, for example, a braking force control device that adds a braking force to a selected wheel and generates a yaw moment in the vehicle. Specifically, a target yaw rate (target yaw rate) is calculated based on the vehicle motion equation based on the vehicle speed and the front wheel steering angle. Then, the target yaw rate is compared with the actual yaw rate (actual yaw rate) to determine whether the current vehicle state is an oversteer tendency or an understeer tendency. As a result, in order to correct the oversteer tendency, a braking force is applied to the front outer wheel in the turning direction, and in order to correct the understeer tendency, the braking force is applied to the inner rear wheel in the turning direction. The vehicle behavior control device 40 is not limited to the braking force control device described above, and may be a device that controls the distribution of driving force between the left and right wheels.

In the vehicle, a vehicle speed sensor 31 that detects a vehicle speed V, a handle angle sensor 32 that detects a steering angle θHd by a driver, a yaw rate sensor 33 that detects an actual yaw rate γ, and an actual lateral acceleration (d ² y / dt ² ) are detected. A lateral acceleration sensor 34 is provided, and signals from these sensors 31, 32, 33, 34 are input to the steering control unit 20.

  Then, the steering control unit 20 calculates a correction amount of the front wheel steering angle to be added in order to keep the vehicle behavior appropriately, in addition to steering by the driver, in accordance with a steering control program to be described later, based on each input signal described above. Then, a signal of the motor rotation angle θM is output to the motor drive unit 21.

  That is, as shown in FIG. 2, the steering control unit 20 includes a first front wheel steering angle correction amount calculation unit 20a, a second front wheel steering angle correction amount calculation unit 20b, a motor rotation angle calculation unit 20c, a steering wheel angle output value. The calculation unit 20d is mainly configured.

The first front wheel steering angle correction amount calculation unit 20 a receives the vehicle speed V from the vehicle speed sensor 31 and the handle angle θHd from the handle angle sensor 32. Then, the first front wheel steering angle correction amount δHc1 is calculated by the following equation (1), and is output to the motor rotation angle calculation unit 20c and the steering wheel angle output value calculation unit 20d.
δHc1 = ((θHd / ndc1) − (θHd / nd)) · nc (1)
Here, nd is a driver-side steering gear ratio (a steering gear ratio that affects the steering operation of the driver when the electric motor 16 is stopped; a pair of sun gears 12U and 12L, a pair of planetary gears 14U and 14L, and a steering wheel Steering gear ratio determined by the gear box 5). Also, nc is determined by the front wheel steering angle correction mechanism 11 side steering gear ratio (the steering gear ratio that is affected when the electric motor 16 rotates while the driver is not operating the steering wheel; the drive gear 17 and the driven gear 18 (carrier)). Steering gear ratio). Further, ndc1 is a vehicle speed sensitive steering gear ratio obtained by a preset map or arithmetic expression. The vehicle speed sensitive steering gear ratio ndc1 is set, for example, as shown in FIG. 4. When the vehicle speed V is low, the vehicle speed sensitive steering gear ratio ndc1 has a quick characteristic with respect to the driver side steering gear ratio nd. The characteristic is determined to be slow with respect to the ratio nd.

The second front wheel steering angle correction amount calculation unit 20b receives the vehicle speed V from the vehicle speed sensor 31, the actual yaw rate γ from the yaw rate sensor 33, and the actual lateral acceleration (d ² y / dt ² ) from the lateral acceleration sensor 34. Is entered. Then, the second front wheel steering angle correction amount δHc2 is calculated by the following equation (2) and output to the motor rotation angle calculation unit 20c.
δHc2 = −Gcg1 · Gcg2 · (dβ / dt) (2)
Here, (dβ / dt) is a vehicle slip angular velocity, and this vehicle slip angular velocity (dβ / dt) is calculated by, for example, the following equation (3).
(Dβ / dt) = γ − ((d ² y / dt ² ) / V) (3)

Gcg1 is a first control gain. The first control gain Gcg1 is determined in advance by experiments, calculations, etc. as shown in FIG. 5, for example. This map is set by the following equation (4) in the region where the vehicle speed V is Vcl or higher.
Gcg1 = 1 / Gγ (4)
Here, Gγ is a yaw rate gain with respect to the turning angle, and is calculated by the following equation (5).
Gγ = (1 / (1 + A · V ² )) · (V / (l · nc)) (5)
Here, A is a stability factor, and l is a wheelbase.

  Further, the region below Vcl in the map of the first control gain Gcg1 is set linearly so as to be small. This is because the yaw rate gain Gγ becomes small in the low speed range, and if it is left as it is, the first control gain Gcg1 becomes too large and the calculation accuracy of the vehicle slip angle becomes low.

  As described above, the first control gain Gcg1 is basically set in consideration of the yaw rate gain Gγ with respect to the turning angle, so that the yaw rate gain per unit correction rudder angle becomes constant, and at high speed and low speed. The degree of control interference with steering can be made constant.

  In the above equation (2), Gcg2 is the second control gain. The second control gain Gcg2 is determined in advance by experiments, calculations, etc. as shown in FIG. 6, for example. This map is set according to the vehicle slip angular velocity (dβ / dt), and is set to 0 in a region where the absolute value of the vehicle slip angular velocity (dβ / dt) is small. Therefore, when the second control gain Gcg2 is multiplied, the second front wheel steering angle correction amount δHc2 becomes 0, in other words, an equation that has a dead zone for the vehicle slip angular velocity (dβ / dt). By providing the dead zone in such a small vehicle slip angular velocity (dβ / dt) region, unnecessary control can be prevented.

The motor rotation angle calculation unit 20c receives the first front wheel steering angle correction amount δHc1 from the first front wheel steering angle correction amount calculation unit 20a and the second front wheel steering angle correction amount calculation unit 20b from the second front wheel steering angle correction amount calculation unit 20b. The quantity δHc2 is input. Then, the motor rotation angle θM is calculated by the following equation (6) and output to the motor drive unit 21.
θM = (δHc1 + δHc2) · nc (6)

The steering wheel angle output value calculation unit 20d receives the steering wheel angle θHd from the steering wheel angle sensor 32 and the first front wheel steering angle correction amount δHc1 from the first front wheel steering angle correction amount calculation unit 20a. Then, the steering wheel angle θHout for output to the vehicle behavior control device 40 is calculated and output by the following equation (7).
θHout = θHd + δHc1 · nc (7)

  That is, the above equation (7) does not include δHc2 · nc (a correction amount according to the vehicle slip angular velocity (dβ / dt)), which interferes with the correction control by the steering control unit 20. This is because the control by the vehicle behavior control device 40 is appropriately performed.

Next, a steering control program executed by the steering control unit 20 will be described with reference to the flowchart of FIG.
First, in step (hereinafter abbreviated as “S”) 101, necessary parameters, that is, the vehicle speed V, the steering angle θHd by the driver, the actual yaw rate γ, and the actual lateral acceleration (d ² y / dt ² ) are read.

  Next, the process proceeds to S102, where the vehicle speed sensitive steering gear ratio ndc1 is calculated according to a map or calculation formula set in advance in the first front wheel steering angle correction amount calculation unit 20a.

  Next, proceeding to S103, the first front wheel steering angle correction amount calculation unit 20a calculates the first front wheel steering angle correction amount δHc1 according to the above equation (1).

  Next, the process proceeds to S104, and the second front wheel steering angle correction amount calculation unit 20b calculates the vehicle slip angular velocity (dβ / dt) by the above-described equation (3).

  Next, the process proceeds to S105, where the second front wheel steering angle correction amount calculation unit 20b calculates the first control gain Gcg1 based on a map determined in advance through experiments, calculations, and the like.

  Next, the process proceeds to S106, and the second front wheel steering angle correction amount calculation unit 20b calculates the second control gain Gcg2 based on a map determined in advance by experiment, calculation, or the like.

  Next, the process proceeds to S107, and the second front wheel steering angle correction amount calculation unit 20b calculates the second front wheel steering angle correction amount δHc2 by the above-described equation (2).

  Next, in S108, the motor rotation angle calculation unit 20c calculates the motor rotation angle θM according to the above equation (6) and outputs it to the motor drive unit 21.

  In step S109, the steering wheel angle output value calculation unit 20d calculates the steering wheel angle θHout to be output to the vehicle behavior control device 40 according to the above equation (7), and outputs the calculation result to the vehicle behavior control device 40. Exit.

  Thus, according to the first embodiment of the present invention, the first front wheel steering angle correction amount δHc1 based on the vehicle speed V and the second front wheel steering angle correction amount δHc2 based on the vehicle slip angular velocity (dβ / dt) Therefore, the unstable vehicle behavior due to the resonance of the yaw motion with respect to the steering can be reliably suppressed while improving the yaw response of the vehicle. Further, since the steering wheel angle θHout for output to the vehicle behavior control device 40 does not include the second front wheel steering angle correction amount δHc2 based on the vehicle slip angular velocity (dβ / dt), the vehicle behavior control is performed. The control by the device 40 and the control by the steering control unit 20 do not interfere with each other, and efficient and stable vehicle control is possible.

  7 and 8 show a second embodiment of the present invention, FIG. 7 is a functional block diagram of the steering control unit, and FIG. 8 is a flowchart of the steering control program. In the second embodiment of the present invention, the second front wheel steering angle correction amount is obtained based on the actual yaw rate γ, and other configurations and operations are the same as those in the first embodiment. The same components are denoted by the same reference numerals, and description thereof is omitted.

  That is, the vehicle speed V from the vehicle speed sensor 31, the steering angle θHd by the driver from the steering wheel angle sensor 32, and the actual yaw rate γ from the yaw rate sensor 33 are input to the steering control unit 25 according to the second embodiment.

  Then, the steering control unit 25 calculates a correction amount of the front wheel steering angle to be added in order to keep the vehicle behavior appropriately, in addition to steering by the driver, in accordance with a steering control program described later, based on each input signal described above. Then, a signal of the motor rotation angle θM is output to the motor drive unit 21.

  As shown in FIG. 7, the steering control unit 25 includes a first front wheel steering angle correction amount calculation unit 20a, a second front wheel steering angle correction amount calculation unit 25a, a motor rotation angle calculation unit 20c, and a steering wheel angle output value calculation unit. Mainly composed of 20d.

The second front wheel steering angle correction amount calculation unit 25 a receives the vehicle speed V from the vehicle speed sensor 31 and the actual yaw rate γ from the yaw rate sensor 32. Then, the second front wheel steering angle correction amount δHc2 is calculated by the following equation (8) and output to the motor rotation angle calculation unit 20c.
δHc2 = −Gcg1 · γ (8)

  Then, the steering control program executed by the steering control unit 25 proceeds to S201 after calculating the first front wheel steering angle correction amount δHc1 in S103, as shown in the flowchart of FIG. In the angle correction amount calculation unit 25a, the first control gain Gcg1 is calculated based on a map previously determined by experiments, calculations, and the like (similar to the first embodiment).

  Next, in S202, the second front wheel steering angle correction amount calculation unit 25a calculates the second front wheel steering angle correction amount δHc2 by the above-described equation (8), and proceeds to S108, in which the motor rotation angle calculation unit is calculated. 20 c calculates the motor rotation angle θM according to the above equation (6) and outputs it to the motor drive unit 21.

  In step S109, the steering wheel angle output value calculation unit 20d calculates the steering wheel angle θHout to be output to the vehicle behavior control device 40 according to the above equation (7), and outputs the calculation result to the vehicle behavior control device 40. Exit.

  Thus, also by the second embodiment, the same effect as that of the first embodiment can be obtained.

  In the first and second embodiments of the present invention, the steering wheel angle θHout is output to the vehicle behavior control device 40, but a vehicle in which the vehicle behavior control device 40 is not mounted, or a steering control unit In the case where the interference with the corrections 20 and 25 is negligible, the steering wheel angle θHout including the second front wheel steering angle correction amount δHc2 may be output.

Explanatory drawing which shows schematic structure of the front-wheel steering apparatus of the vehicle by 1st Embodiment of this invention. Same as above, functional block diagram of steering control unit Same as above, steering control program flowchart Same as above, characteristic chart of vehicle speed sensitive steering gear ratio Same as above, characteristic diagram of first control gain Same as above, characteristic diagram of second control gain The functional block diagram of the steering control part by the 2nd Embodiment of this invention Same as above, steering control program flowchart

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Front wheel steering device 2 Steering wheel 3 Steering shaft 4 Joint part 5 Steering gear box 7fl, 7fr Front wheel 11 Front wheel rudder angle correction mechanism 16 Electric motor 20 Steering control part (front wheel rudder angle correction means)
20a First front wheel steering angle correction amount calculation unit 20b Second front wheel steering angle correction amount calculation unit 20c Motor rotation angle calculation unit 20d Handle angle output value calculation unit 21 Motor drive unit 40 Vehicle behavior control device (vehicle behavior control means)

Claims (6)

Steering control of a vehicle provided with front wheel steering angle correction means for calculating a front wheel steering angle correction amount to be added to the input front wheel steering angle and operating the front wheel steering angle correction mechanism to add the front wheel steering angle correction amount In the device
The front wheel steering angle correction means calculates a value obtained by multiplying a vehicle slip angular velocity by a control gain calculated based on a change in yaw rate gain with respect to a steering angle corresponding to a vehicle speed, as the front wheel steering angle correction amount. A vehicle steering control device. The front wheel rudder angle correction means calculates, as the front wheel rudder angle correction amount, a value obtained by adding a front wheel rudder angle correction amount based on a vehicle speed to a value obtained by multiplying the vehicle slip angular velocity by the control gain. Item 2. The vehicle steering control device according to Item 1.   3. The vehicle steering control device according to claim 1, wherein a value obtained by multiplying the vehicle slip angular velocity by the control gain gives a dead zone in a preset region of the vehicle slip angular velocity. Steering control of a vehicle provided with front wheel steering angle correction means for calculating a front wheel steering angle correction amount to be added to the input front wheel steering angle and operating the front wheel steering angle correction mechanism to add the front wheel steering angle correction amount In the device
The front wheel steering angle correction means calculates a value obtained by multiplying a yaw rate by a control gain calculated based on a change in yaw rate gain with respect to a steering angle corresponding to a vehicle speed, as the front wheel steering angle correction amount. Steering control device. The front wheel rudder angle correction means calculates, as the front wheel rudder angle correction amount, a value obtained by adding a front wheel rudder angle correction amount based on a vehicle speed to a value obtained by multiplying the vehicle slip angular velocity by the control gain. Item 5. The vehicle steering control device according to Item 4. A vehicle behavior control means for calculating a control amount based on at least the front wheel steering angle and generating a yaw moment in the vehicle by braking force control or driving force control based on the control amount to control the vehicle behavior;
6. The front wheel rudder angle correcting means outputs a front wheel rudder angle excluding a value obtained by multiplying the vehicle body slip angular velocity by the control gain to the vehicle behavior control means. The vehicle steering control device according to any one of the above.

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