JP2008068661A - Steering angle control device, automobile and steering angle control method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent a situation of giving a sense of incongruity to a driver while suppressing vibration generated in a steering wheel relating to steering speed, in an automobile having a variable steering angle mechanism and capable of turning front and rear wheels. <P>SOLUTION: A front wheel steering angle control means calculates a front wheel target steering angle according to a steering operation while suppressing high-frequency component of a front wheel steered angle, a rear wheel steering angle control means calculates a rear wheel target steering angle based on the front wheel target steering angle, and the front wheel steering angle control means and the rear wheel steering angle control means drive a motor for varying steering angle ratio and a motor for turning the rear wheel so as to be the front wheel target steering angle and the rear wheel target steering angle. Therefore, even if a high-speed steering operation is performed by the driver, the vibration of the steering wheel can be suppressed by a reaction force of the motor, and the situation of giving the sense of incongruity to the driver can be prevented, since a steering angle control between the front and rear wheels are corresponding to each other. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a steering angle control device, an automobile, and a steering angle control method for controlling a steering angle of a vehicle.

2. Description of the Related Art Conventionally, an automobile having a variable steering angle mechanism that makes a steering angle ratio of steered wheels variable is known.
In an automobile equipped with such a variable steering angle mechanism, when a steering input is made by the driver, the target steering angle is output by adjusting and outputting the steering angle amount by an actuator (motor). Is controlled.

However, in such a variable rudder angle mechanism, when the driver performs a high-speed steering operation, the actuator operates at a high speed, and the reaction force is transmitted to the steering wheel. As a result, the steering wheel may vibrate. There is sex.
In order to prevent such a situation, in the technique described in Patent Document 1, the control amount of the component corresponding to the steering speed is attenuated, thereby preventing the vibration generated in the steering wheel.
JP 2001-138936 A

By the way, an automobile capable of turning a rear wheel in addition to a front wheel is known, and it is conceivable to install a variable steering angle mechanism on the front wheel even in such a vehicle.
However, when the technology described in Patent Document 1 is applied to an automobile that can steer front and rear wheels, the response characteristics of the output steering angle are different between the front wheels and the rear wheels, and the vehicle response characteristics and the turning trajectory are the target. It may change from the movement characteristics and may give the driver a sense of incongruity.
An object of the present invention is to prevent a situation in which an uncomfortable feeling is given to a driver while suppressing vibration generated in a steering wheel due to a steering speed in an automobile having a variable steering angle mechanism and capable of steering front and rear wheels. That is.

In order to solve the above problems, the rudder angle control device according to the present invention,
The steering angle ratio input by the steering angle ratio variable motor that drives the steering angle ratio variable mechanism provided between the steering input and output shafts while transmitting the steering angle input to the steering input shaft by the steering operation to the steering output shaft. The front wheel steering mechanism that steers and outputs the front wheels, the rear wheel steering mechanism that steers the rear wheels by the rear wheel steering motor, and the high frequency component of the steering angle output from the steering output shaft is suppressed. A front wheel rudder angle control means for calculating a front wheel target rudder angle according to a steering operation, and a rear wheel rudder angle for calculating a rear wheel target rudder angle based on the front wheel target rudder angle calculated by the front wheel rudder angle control means. Control means, the front wheel rudder angle control means drives the rudder angle ratio variable motor so as to achieve the calculated front wheel target rudder angle, and the rear wheel rudder angle control means calculates the calculated rear wheel target rudder angle. The rear wheel steering motor is driven so that That.

In addition, the automobile according to the present invention is
A steering wheel connected to the steering input shaft and performing a steering operation, and a steering angle input to the steering input shaft by a steering operation on the steering wheel is transmitted to the steering output shaft, and provided between the steering input and output shafts A front wheel steering mechanism that changes the input / output rudder angle ratio by a steering angle ratio variable motor that drives the steering angle ratio variable mechanism and outputs the steering to the front wheels, and a rear wheel steering that steers the rear wheels by the rear wheel steering motor. Calculated by the front wheel steering angle control means for calculating the front wheel target steering angle according to the steering operation while suppressing the high frequency component of the steering angle output from the mechanism, the steering output shaft, and the front wheel steering angle control means A front wheel steering angle control means for calculating a rear wheel target steering angle based on a front wheel target steering angle; and a vehicle body on which the front wheel steering mechanism and the rear wheel steering mechanism are installed. Calculated The rudder angle ratio variable motor is driven so as to be a wheel target rudder angle, and the rear wheel rudder angle control means drives the rear wheel steering motor so as to be a calculated rear wheel target rudder angle. Yes.

Further, the rudder angle control method according to the present invention includes:
The steering angle ratio input by the steering angle ratio variable motor that drives the steering angle ratio variable mechanism provided between the steering input and output shafts while transmitting the steering angle input to the steering input shaft by the steering operation to the steering output shaft. Including a front wheel steering step for steering output to the front wheels and a rear wheel steering step for steering the rear wheels by the rear wheel steering motor to suppress high frequency components of the steering angle output from the steering output shaft However, a front wheel rudder angle control step for calculating a front wheel target rudder angle according to a steering operation, a rear wheel rudder angle control step for calculating a rear wheel target rudder angle based on the front wheel target rudder angle, and the front wheel target rudder Steering angle ratio variable motor driving step for driving the steering angle ratio variable motor so as to achieve a steering angle, and rear wheel steering motor driving step for driving the rear wheel steering motor so as to achieve the rear wheel target steering angle And further comprising There.

According to the steering angle control device of the present invention, the front wheel steering angle control means calculates the front wheel target steering angle according to the steering operation while suppressing the high frequency component of the front wheel steering angle, and the rear wheel steering angle control means. However, based on the front wheel target rudder angle, the rear wheel target rudder angle is calculated, and the front wheel rudder angle control means and the rear wheel rudder angle control means steer so that the front wheel target rudder angle and the rear wheel target rudder angle become the same. The motor for variable angle ratio and the motor for rear wheel steering are driven.
Therefore, even when a high-speed steering operation is performed by the driver, the steering wheel can be prevented from vibrating due to the reaction force of the motor, and the steering angle control between the front and rear wheels is made compatible, which makes the driver feel uncomfortable. The situation can be prevented.

  According to the vehicle of the present invention, the front wheel steering angle control means calculates the front wheel target steering angle corresponding to the steering operation while suppressing the high frequency component of the front wheel steering angle with respect to the steering operation input to the steering wheel. The rear wheel rudder angle control means calculates the rear wheel target rudder angle based on the front wheel target rudder angle, and the front wheel rudder angle control means and the rear wheel rudder angle control means Since the steering angle ratio variable motor and the rear wheel steering motor are driven so as to achieve the target steering angle, it is possible to prevent the steering wheel from vibrating due to the reaction force of the motor even if the driver performs a high-speed steering operation. In addition, since the steering angle control between the front and rear wheels is made to correspond, it is possible to prevent the driver from feeling uncomfortable.

  According to the rudder angle control method according to the present invention, the front wheel rudder angle control step of calculating the front wheel target rudder angle according to the steering operation while suppressing the high frequency component of the steered angle output from the steering output shaft, And a rear wheel rudder angle control step for calculating a rear wheel target rudder angle based on the front wheel target rudder angle, so that the steering wheel is driven by the reaction force of the motor even if a high-speed steering operation is performed by the driver. Since vibration can be suppressed and the steering angle control between the front and rear wheels is made compatible, it is possible to prevent the driver from feeling uncomfortable.

Embodiments of an automobile to which the present invention is applied will be described below with reference to the drawings.
(First embodiment)
(Constitution)
FIG. 1 is a diagram showing a configuration of an automobile 1 according to the present invention.
In FIG. 1, an automobile 1 includes a steering wheel 2, a steering input shaft 3, a VGR (Variable Gear Ratio) 4, a steering output shaft 5, a pinion gear 6, a steering rack 7, and tie rods 8FR, 8FL, 8RR. , 8RL, wheels 9FR, 9FL, 9RR, 9RL, wheel speed sensors 10FR, 10FL, 10RR, 10RL, a rear wheel steering motor 11, a rear wheel steering rack 12, a steering controller 13, and an interface 14 And a control unit 15.

The steering operation input to the steering wheel 2 is transmitted to the VGR 4 via the steering input shaft 3.
A steering angle sensor constituted by an encoder, a potentiometer or the like is installed on the steering input shaft 3, and a detection signal thereof is output to the control unit 15 via the interface 14.

  The VGR 4 has a two-stage planetary gear mechanism on the input side and output side that uses the sun gear in common, the ring gear of the input-side planetary gear mechanism is fixed to the vehicle body, and the ring gear of the output-side planetary gear mechanism is It is configured to be rotatable by a steering angle ratio variable motor. The steering input shaft 3 is connected to the shaft of the planetary gear on the input side, and the steering output shaft 5 is connected to the shaft of the planetary gear on the output side. With this configuration, when the input-side planetary gear is rotated by the steering input shaft 3, the rotation is transmitted to the sun gear, and the output-side planetary gear is rotated by the rotation of the sun gear. At this time, by rotating the rudder angle ratio variable motor, the ring gear of the planetary gear mechanism on the output side is rotated, and the steering output shaft 5 has the rotation angle inputted from the steering input shaft 3 and the rudder. A rotation angle obtained by adding the rotation angle input by the angle ratio variable motor is output. That is, the steering gear ratio is made variable by VGR4.

The VGR 4 steering angle ratio variable motor is provided with a rotation angle sensor 4a for detecting the motor rotation angle. The rotation angle sensor 4a sends a signal indicating the detected motor rotation angle via the interface 14. Output to the control unit 15.
A pinion gear 6 is provided at the tip of the steering output shaft 5, and the pinion gear 6 meshes with a rack gear formed on the steering rack 7. Therefore, when the steering output shaft 5 rotates, the pinion gear 6 rotates while meshing with the rack gear, thereby moving the steering rack 7 in the vehicle width direction.

  The front end of the steering rack 7 is connected to one end of the tie rods 8FL, 8FR, and the other end of the tie rods 8FL, 8FR is connected to the knuckle arms of the left and right wheels 10FL, 10FR. Therefore, when the steering rack 7 is moved in the vehicle width direction, the movement is transmitted to the knuckle arms on the left and right front wheels via the tie rods 8FL, 8FR, and the wheels 9FL, 9FR are steered.

  The rear wheel steering motor 11 is driven by a drive command signal input from the steering controller 13. Further, the rear wheel steering motor 11 includes a pinion gear on a rotating shaft, and the pinion gear meshes with a rack gear formed on the rear wheel steering rack 12. Therefore, when the rear wheel steering motor 11 is driven by the steering controller 13, the pinion gear rotates while meshing with the rack gear, thereby moving the rear wheel steering rack 12 in the vehicle width direction.

The rear wheel steering motor 11 is provided with a rear wheel motor angle sensor 11a for detecting the motor rotation angle. The rear wheel motor angle sensor 11a sends a signal indicating the detected motor rotation angle to the interface 14. To the control unit 15.
The front end of the rear wheel steering rack 12 is connected to one end of the tie rods 8RL, 8RR, and the other end of the tie rods 8RL, 8RR is connected to the knuckle arms of the left and right wheels 10RL, 10RR. Therefore, when the rear wheel steering rack 12 is moved in the vehicle width direction, the movement is transmitted to the knuckle arms on the left and right front wheels via the tie rods 8RL and 8RR, and the wheels 9RL and 9RR are steered.

The steering controller 13 is based on the front and rear wheel steering angle command values input from the control unit 15 via the interface 14, and the steering angle ratio variable motor and the rear wheel steering motor 11 corresponding to the steering angle. And a drive command signal for driving the drive amount is output to the steering angle ratio variable motor and the rear wheel steering motor 11.
The interface 14 converts the signal format or adjusts the transmission / reception timing of various signals input from the rotation angle sensor 4a, the steering angle sensor, the rear wheel motor angle sensor 11a, and the wheel speed sensors 10FR, 10FL, 10RR, 10RL. These signals are output to the control unit 15 or output to the steering controller 13, and the front and rear wheel steering angle command values input from the control unit 15 are output to the steering angle controller 13. To do.

The control unit 15 receives various signals from the rotation angle sensor 4a, the steering angle sensor, the rear wheel motor angle sensor 11a, and the wheel speed sensors 10FR, 10FL, 10RR, and 10RL via the interface 14.
The control unit 15 then sets a transfer function L set in advance based on the vehicle speed V calculated from the detection signals of the wheel speed sensors 10FR, 10FL, 10RR, 10RL and the steering angle θ detected by the steering angle sensor. The target vehicle motion is calculated using (s), and the target slip angle β and the target yaw rate γ are calculated as the calculation results.

Further, the control unit 15 calculates a reference steering angle for the front and rear wheels (hereinafter referred to as “first front and rear wheel target steering angle”) based on the calculated target slip angle β and target yaw rate γ.
Then, the control unit 15 performs a front and rear wheel steering angle calculation process, which will be described later, for the purpose of suppressing steering wheel vibration and reducing the driver's uncomfortable feeling, and corrects the first front and rear wheel target steering angle.

Furthermore, the control unit 15 sends a turning angle command value indicating the front and rear wheel steering angles (hereinafter referred to as “second front and rear wheel target steering angles”) after correction by the front and rear wheel steering angle calculation processing via the interface 14. Output to the steering controller 13.
After that, the steering controller 13 detects the motor rotation angle detected by the rotation angle sensor 4a of the VGR 4 and the rear wheel motor angle sensor 11a so that the steering angle of the front and rear wheels becomes the second front and rear wheel target steering angle. The steering amount is controlled while referring to FIG.

(Calculation method of target slip angle β and target yaw rate γ)
Next, a specific calculation method of the target slip angle β and the target yaw rate γ in the control unit 15 will be described.
The control unit 15 includes a target vehicle motion calculation unit A101 that calculates a target value of vehicle motion from the vehicle speed V and the steering angle θ according to a preset transfer function L (s).

  In the present embodiment, the target vehicle motion calculation unit A101 calculates a target yaw rate γ (standard yaw rate) and a target slip angle β (standard vehicle body slip angle) according to the steering angle θ. The response characteristic L (s) of the target yaw rate γ and the target slip angle β can be set arbitrarily. Here, the response characteristic L (s) to the steering using the linear two-wheel model is set to each of the target slip angle β and the target yaw rate γ. Is set as follows.

In the above equations, V is the vehicle speed, A is the vehicle stability factor, m is the vehicle mass, l _z is the vehicle yaw moment of inertia, _cf is the front wheel equivalent cornering power, _cr is the rear wheel equivalent cornering power, l _f is the distance between the center of gravity and the front axis, l _r is the distance between the center of gravity and the rear axis, l is the wheelbase, and s is the Laplace operator.

(Calculation method of first front and rear wheel target rudder angle)
Next, a specific method for calculating the first front and rear wheel target rudder angle in the control unit 15 will be described.
The control unit 15 includes a first front and rear wheel steering angle calculation unit A102 that calculates the front and rear wheel steering angles using the reverse system V ^-1 (s) of the host vehicle model.
When the linear two-degree-of-freedom model is used, the first front and rear wheel target rudder angle is calculated by the following arithmetic expression.
First, when the first front wheel target rudder angle is δ _f (s) and the first rear wheel target rudder angle is δ _r (s), the target yaw rate γ and the target slip angle β calculated by the target vehicle motion calculation unit A101 are calculated. The front and rear wheel rudder angles to be realized are calculated according to the following equation representing the reverse system V ^-1 (s) of the host vehicle model.

  By calculating the front and rear wheel steering angles according to the equation (3) and controlling the steering angle, the feedforward control can be performed so as to satisfy the target yaw rate γ and the target slip angle β.

(Front and rear wheel steering angle calculation processing in the control unit 15)
Next, the front and rear wheel steering angle calculation processing executed by the control unit 15 will be described.
The control unit 15 includes a second front wheel steering angle calculation unit A103 that calculates the second front wheel steering angle, and a second rear wheel steering angle calculation unit A104 that calculates the second rear wheel steering angle.
Then, the control unit 15 performs front and rear wheel steering angle calculation processing for correcting the first front and rear wheel target steering angle by the second front wheel steering angle calculation unit A103 and the second rear wheel steering angle calculation unit A104.

FIG. 2 is a flowchart showing the front and rear wheel steering angle calculation processing. The front and rear wheel steering angle calculation processing is started with the ignition on, and is repeatedly executed until the ignition is turned off.
In FIG. 2, when the front and rear wheel steering angle calculation processing is started, the control unit 15 reads the first front wheel target steering angle δ _f (s) into the second front wheel steering angle calculation unit A103 (step S1), and 2 The first rear wheel target steering angle δ _r (s) is read into the rear wheel steering angle calculation unit A104 (step S2).
Next, the control unit 15 uses the second front wheel steering angle calculation unit A103 to perform a calculation for applying a low-pass filter Hf (s) represented by the following equation to the first front wheel target steering angle in order to suppress high-frequency signals. The second front wheel target rudder angle δ _f ′ (s) is calculated (step S3).

However, τ ₁ is an arbitrary constant.
FIG. 3 is a diagram showing the filter characteristics of the low-pass filter Hf (s) shown in the equation (4). As shown in FIG. 3, by applying Hf (s), control is performed such that the higher the steering frequency, the smaller the gain of the second front wheel target rudder angle with respect to the steering input.

Returning to Figure 2, the control unit 15, the second rear-wheel steering angle calculation unit A 104, to match a front wheel steering control is corrected steering control of the rear wheels, rear first wheel target steering angle [delta] _r (S) is subjected to an operation for applying a transfer function Hf (s) · Gf (s) · Gr ⁻¹ (s) to calculate a second rear wheel target rudder angle δ _r ′ (s) (step S4). . Here, Hf (s) in the transfer function Hf (s) · Gf (s) · Gr ⁻¹ (s) is Hf (s) shown in the equation (4), and Gf (s) is the front wheel steering system. Gr (s) is a model of the rear wheel steering system.

Then, the control unit 15 outputs the second front wheel target rudder angle δ _f ′ (s) calculated in step S3 from the second front wheel rudder angle calculation unit A103 to the front wheel steering system (step S5), and calculates in step S4. The second rear wheel target rudder angle δ _r ′ (s) is output from the second rear wheel rudder angle calculation unit A104 to the rear wheel steering system (step S6).
Thereafter, the control unit 15 repeats the front and rear wheel steering angle calculation processing.

Such processing results, 'to (s), after the second wheel target steering angle [delta] _r' first rear wheel target steering angle [delta] _r with suppressed high-frequency signal (s) also suppress the high-frequency signal Is output in the same state.
Furthermore, for the front wheel steering system model Gf (s) and the rear wheel steering system model Gr (s), the control accuracy can be improved by designing the response characteristics of the motor control system as follows. .
That is,

However, when the model follow-up control (two-degree-of-freedom control system) shown in FIG. 4 is performed with a control system showing a first-order lag response such that τ ₂ becomes an arbitrary constant as a reference model, the second rear wheel steering angle The transfer function of the arithmetic unit A104 is

Thus, the response characteristics of the rear wheels and the response characteristics of the front wheels can be matched.

(Operation)
Then, operation | movement of the motor vehicle 1 which concerns on this embodiment is demonstrated.
FIG. 5 is a block diagram showing a control operation of the automobile 1.
Assuming that the automobile 1 is traveling at the vehicle speed V and the steering input of the steering angle θ is performed, first, the target vehicle motion calculation unit A101 first calculates the target yaw rate γ and the target slip angle β according to the expressions (1) and (2). And calculate.

Next, the first front and rear wheel rudder angle calculation unit A102 calculates the first front wheel target rudder angle δ _f (s) and the target yaw rate γ and the target slip angle β according to the reverse system V ⁻¹ (s) of the host vehicle model. A first rear wheel target rudder angle δ _r (s) is calculated.
The second front wheel steering angle calculator A103 corrects the first front wheel target rudder angle δ _f (s) by suppressing the high-frequency signal based on the transfer function Hf (s). A target rudder angle δ _f ′ (s) is calculated. For the first rear wheel target rudder angle δ _r (s), the second rear wheel rudder angle calculation unit A104 is based on the transfer function Hf (s) · Gf (s) · Gr ⁻¹ (s), The second rear wheel target rudder angle δ _r ′ (s) is calculated by performing a correction in accordance with the correction of the front wheel rudder angle.

The second front wheel target rudder angle δ _f ′ (s) and the second rear wheel target rudder angle δ _r ′ (s) are output from the control unit 15 to the steering controller 13 as a turning angle command value.
Then, through the front wheel steering system and the rear wheel steering system, the front wheel actual steering angle δ _f ″ (s) and the rear wheel actual steering angle δ _r ″ (s) are given as actual steering amounts, and the steering is performed. The actual slip angle β _y and the actual yaw rate γ _y defined by the vehicle characteristic V (s) appear depending on the amount.

As described above, the vehicle 1 according to the present embodiment has the first front wheel target rudder angle δ _f (s) and the first target after the target slip angle β and the target yaw rate γ determined according to the steering angle θ and the vehicle speed V. The wheel steering angle δ _r (s) is calculated, and the second front wheel target steering angle δ _f ′ (s) in which the control amount of the high frequency component at the first front wheel target steering angle δ _f (s) is suppressed is output. while being suppressed the control amount of high frequency components in accordance with the first front wheel target steering angle δ _f (s), the second rear wheel target steering which is the corresponding response to the first front wheel target steering angle [delta] _f (s) The angle δ _r ′ (s) is output, and the steering angle control is performed using these target steering angles as steering angle command values.

  Therefore, even when a high-speed steering operation is performed by the driver, the steering wheel can be prevented from vibrating due to the reaction force of the motor, and the steering angle control between the front and rear wheels is made compatible, which makes the driver feel uncomfortable. The situation can be prevented. Further, in the conventional processing procedure, functions can be easily realized by interposing processes in the second front wheel steering angle calculation unit A103 and the second rear wheel steering angle calculation unit A104 in series.

FIG. 6 is a control block diagram including a driver in a conventional automobile.
As shown in FIG. 6, when the driver performs a high-speed steering operation, the first front wheel target rudder angle is calculated thereby, and high-speed operation is performed in the motor. Then, the reaction force due to the operation of the motor is transmitted to the handle, and the handle vibrates.
On the other hand, as shown in the present embodiment, by suppressing a high-frequency signal at the first front wheel target rudder angle, high-speed operation in the motor is suppressed, so that vibration of the steering wheel is prevented.

FIG. 7 is a diagram illustrating response characteristics with respect to the target rudder angle when the high-frequency component is not suppressed at the first front and rear wheel target rudder angle. FIG. 8 is a diagram showing response characteristics with respect to the target rudder angle in the case of suppressing high frequency components at the first front and rear wheel target rudder angle.
In FIG. 7, the difference between the front and rear wheel gains in the high frequency region is large, whereas in FIG. 8, the gains between the front and rear wheels match up to the high frequency region, which gives the driver a sense of incongruity. Is prevented.

  In this embodiment, the steering input shaft 3, the VGR 4, the steering output shaft 5, the pinion gear 6, the steering rack 7, and the tie rods 8FR, 8FL constitute a front wheel steering mechanism, a rear wheel steering motor 11, and a rear wheel steering rack. 12 and tie rods 8RR, 8RL constitute a rear wheel steering mechanism, and the turning controller 13, the interface 14 and the control unit 15 constitute front wheel steering angle control means and rear wheel steering angle control means. The first front and rear wheel rudder angle calculation unit A102 constitutes first front wheel target rudder angle calculation means and first rear wheel target rudder angle calculation means, and the second front wheel rudder angle calculation unit A103 calculates second front wheel target rudder angle calculation means. The second rear wheel rudder angle calculation unit A104 constitutes second rear wheel target rudder angle calculation means.

(Effect of 1st Embodiment)
(1) The front wheel rudder angle control means calculates the front wheel target rudder angle according to the steering operation while suppressing the high frequency component of the front wheel rudder angle, and the rear wheel rudder angle control means is based on the front wheel target rudder angle. The rear wheel target rudder angle is calculated, and the front wheel rudder angle control means and the rear wheel rudder angle control means control the rudder angle ratio variable motor and the rear wheel steering so that these front wheel target rudder angle and rear wheel target rudder angle become the same. Drive motor.
Therefore, even when a high-speed steering operation is performed by the driver, the steering wheel can be prevented from vibrating due to the reaction force of the motor, and the steering angle control between the front and rear wheels is made compatible, which makes the driver feel uncomfortable. The situation can be prevented.

(2) The first front wheel target rudder angle calculation means calculates the first front wheel target rudder angle based on the rudder angle input by the steering operation, and the second front wheel target rudder angle calculation means calculates the first front wheel target rudder angle at the first front wheel target rudder angle. The second front wheel target rudder angle is calculated by suppressing the high frequency component, and the first rear wheel target rudder angle calculating means calculates the first rear wheel target rudder angle based on the rudder angle input by the steering operation. The second rear wheel target rudder angle calculating means corrects the first rear wheel target rudder angle with the output response characteristic of the second front wheel target rudder angle to obtain the second rear wheel target rudder angle. The front wheel rudder angle control means and the rear wheel rudder angle control means drive the rudder angle ratio variable motor and the rear wheel steer motor so that these second front wheel target rudder angle and second rear wheel target rudder angle become the same. .

  Therefore, the front wheel target rudder angle in which the high-frequency component of the front wheel turning angle is suppressed and the rear wheel target rudder angle corresponding to the output response characteristic are controlled based on the target rudder angle of the front and rear wheels corresponding to the steering operation. Therefore, it is possible to prevent the driver from feeling uncomfortable, and to prevent the steering wheel from being vibrated due to the motor reaction force due to the high-speed steering operation.

(3) A front wheel steering model in which the second front wheel target rudder angle calculating means corrects the first front wheel target rudder angle in accordance with the set correction characteristic, and the second rear wheel target rudder angle calculating means models the front wheel steering mechanism. Then, based on the rear wheel steering model that models the rear wheel steering mechanism and the correction characteristic, correction is performed so that the first rear wheel target rudder angle corresponds to the output response characteristic of the second front wheel target rudder angle.
Therefore, the second rear wheel target rudder angle can be more accurately associated with the output response characteristic of the second front wheel target rudder angle.

(4) Correction that the second front wheel target rudder angle calculating means suppresses a high-frequency component for the entire output rudder angle by the steering operation at the first front wheel target rudder angle and the output rudder angle by the rudder angle ratio variable motor. Therefore, the function of suppressing the vibration of the steering wheel due to the reaction force of the motor and the function of corresponding the steering angle control between the front and rear wheels can be easily realized.

(5) For the steering operation input to the steering wheel, the front wheel steering angle control means calculates the front wheel target steering angle according to the steering operation while suppressing the high frequency component of the front wheel steering angle, and the rear wheel steering angle. The control means calculates the rear wheel target rudder angle based on the front wheel target rudder angle so that the front wheel rudder angle control means and the rear wheel rudder angle control means have these front wheel target rudder angle and rear wheel target rudder angle. In addition, the steering wheel ratio variable motor and the rear wheel steering motor are driven by an automobile, so that the steering wheel can be prevented from vibrating due to the reaction force of the motor even when the driver performs a high-speed steering operation. Since the steering angle control between the wheels is made compatible, it is possible to prevent the driver from feeling uncomfortable.

(6) A front wheel rudder angle control step for calculating a front wheel target rudder angle according to a steering operation while suppressing a high frequency component of a steered angle output from the steering output shaft, and a rear wheel based on the front wheel target rudder angle Since the steering angle control method includes the rear wheel steering angle control step for calculating the wheel target steering angle, it is possible to prevent the steering wheel from vibrating due to the reaction force of the motor even if the driver performs a high-speed steering operation. In addition, since the steering angle control between the front and rear wheels is made to correspond, it is possible to prevent the driver from feeling uncomfortable.

(Second Embodiment)
Next, a second embodiment of the present invention will be described.
(Constitution)
In the vehicle 1 according to this embodiment, the calculation method of the second front wheel target rudder angle in the first embodiment is different.
That is, in the first embodiment, the high-frequency signal at the first front wheel target rudder angle δ _f (s) is suppressed, and the steering amount corresponding to the driver's high-speed steering operation is suppressed. In this embodiment, the reaction force of the VGR 4 steering angle ratio variable motor is selectively reduced.
Therefore, since the configuration of the control unit 15 of the vehicle 1 according to the present embodiment is different from that of the first embodiment, the configuration of the control unit 15 will be described, and the description of FIG. And

(Calculation method of target slip angle β and target yaw rate γ)
The control unit 15 includes a target vehicle motion calculation unit B101 that calculates a target value of vehicle motion from the vehicle speed V and the steering angle θ according to a preset transfer function L (s).
The specific calculation method of the target slip angle β and the target yaw rate γ in the target vehicle motion calculation unit B101 is the same as that of the target vehicle motion calculation unit A101 in the first embodiment.
That is, the target vehicle motion calculation unit B101 receives the vehicle speed V and the steering angle θ, and calculates the target slip angle β and the target yaw rate γ according to the response characteristic L (s).

(Calculation method of first front and rear wheel target rudder angle)
The control unit 15 includes a first front and rear wheel steering angle calculation unit B102 that calculates the front and rear wheel steering angles using the reverse system V ^-1 (s) of the host vehicle model.
The specific calculation method of the first front and rear wheel target rudder angle in the first front and rear wheel rudder angle calculation unit B102 is the same as that of the target vehicle motion calculation unit A101 in the first embodiment.
In other words, the first front / rear wheel steering angle calculation unit B102 receives the target yaw rate γ and the target slip angle β calculated by the target vehicle motion calculation unit B101 as inputs, and follows the inverse system V ⁻¹ (s) of the host vehicle model. The front and rear wheel steering angles that realize the yaw rate γ and the target slip angle β are calculated.

(Front and rear wheel steering angle calculation processing in the control unit 15)
The control unit 15 includes a second front wheel steering angle calculation unit B103 that calculates the second front wheel steering angle and a second rear wheel steering angle calculation unit B104 that calculates the second rear wheel steering angle.
Then, the control unit 15 performs front and rear wheel steering angle calculation processing for correcting the first front and rear wheel target steering angle by the second front wheel steering angle calculation unit B103 and the second rear wheel steering angle calculation unit B104.

FIG. 9 is a flowchart showing front and rear wheel steering angle calculation processing according to the second embodiment. The front and rear wheel steering angle calculation processing is started with the ignition on, and is repeatedly executed until the ignition is turned off.
In FIG. 9, when the front and rear wheel steering angle calculation processing is started, the control unit 15 reads the steering angle θ into the second front wheel steering angle calculation unit B103 (step S101), and further, the first front wheel target steering angle δ _f. (S) is read (step S102), and the first rear wheel target rudder angle δ _r (s) is read into the second rear wheel rudder angle calculation unit B104 (step S103).

Next, the control unit 15 calculates the steering angle θ _h of the driver at the steering angle θ (the steering angle corresponding to the manual operation of the driver) by the second front wheel steering angle calculation unit B103 according to the following equation (step S104). .
θ _h = θ / Gr (7)
However, Gr is a steering overall gear ratio.

Subsequently, the control unit 15, the second front-wheel steering angle calculation unit B 103, subtracts the steering angle theta _h of the driver from the first front wheel target steering angle _{δ f (s) (θ m} = δ f (s) - θ _h ) to calculate the target steering angle (hereinafter referred to as “front wheel motor target steering angle”) θ _m of the VGR 4 steering angle ratio variable motor (step S105).
Next, the control unit 15 uses the second front wheel rudder angle calculation unit B103 to suppress a high frequency signal at the front wheel motor target rudder angle θ _{m, with} respect to the first front wheel target rudder angle, a low-pass filter represented by the following equation: An operation for applying Mf (s) (θ _m ′ = Mf (s) · θ _m ) is performed to calculate a front wheel motor target rudder angle θ _m ′ corrected to suppress the high-frequency signal (step S106).

However, Ts is a time constant, and here, Ts is set as a fixed value and Ts = 0.04 [sec].
Further, the control unit 15, the second front-wheel steering angle calculation unit B 103, 'by adding the steering angle theta _h of the driver ([delta] _f' front wheel motor target steering angle theta _m calculated in step S106 (s ) = Θ _h + θ _m ′), the second front wheel target rudder angle δ _f ′ (s) is calculated and output to the front wheel steering system (step S107).

Further, the control unit 15 adjusts the rear wheel steering control to the corrected front wheel steering control by the second rear wheel steering angle calculation unit B104, so that the first rear wheel target steering angle δ _r (s) is set. On the other hand, an operation for applying the transfer function Mr (s) is performed to calculate the second rear wheel target steering angle δ _r ′ (s) (step S108). Here, the transfer function Mr (s) is expressed by the following equation using a front wheel steering system model Gf (s) that models the front wheel steering system and a rear wheel steering system model Gr (s) that models the rear wheel steering system. It is expressed as

Further, the control unit 15 outputs the second rear wheel target rudder angle δ _r ′ (s) calculated in step S108 from the second rear wheel rudder angle calculation unit B104 to the rear wheel steering system (step S109).
Thereafter, the control unit 15 repeats the front and rear wheel steering angle calculation processing.
As a result of such processing, it is possible to selectively reduce the reaction force of the steering angle ratio variable motor that directly causes the steering wheel to vibrate. In addition, since the front wheel turning amount by the driver steering at high frequency is output without being suppressed, the first front wheel target rudder angle increases proportionally or differentially as the steering angle increases. In such a case, it is possible to maintain high-frequency steering angle responsiveness.

(Operation)
Then, operation | movement of the motor vehicle 1 which concerns on this embodiment is demonstrated.
FIG. 10 is a block diagram illustrating a control operation of the automobile 1.
Assuming that the automobile 1 is traveling at the vehicle speed V and the steering input of the steering angle θ is performed, first, the target vehicle motion calculation unit B101 performs the target yaw rate γ and the target slip angle β according to the equations (1) and (2). And calculate.
Next, the first front and rear wheel rudder angle calculation unit B102 calculates the first front wheel target rudder angle δ _f (s) and the target yaw rate γ and the target slip angle β according to the reverse system V ⁻¹ (s) of the host vehicle model. A first rear wheel target rudder angle δ _r (s) is calculated.

The second front-wheel steering angle calculation section B103 calculates the front wheel motor target steering angle theta _m by subtracting the steering angle theta _h of the driver from the first front wheel target steering angle δ _f (s). And 2nd front wheel steering angle calculating part B103 suppressed the high frequency signal by performing the correction which suppresses a high frequency signal based on transfer function Mf (s) with respect to front-wheel motor target steering angle (theta) _m . 'it is calculated, and the second front wheel target steering angle [delta] _f by adding the steering angle theta _h of the driver on the front wheel motor target steering angle theta _m' front wheel motor target steering angle theta _m to calculate the (s).

Further, the second rear wheel rudder angle calculation unit B104 performs a calculation for applying the transfer function Mr (s) to the first rear wheel target rudder angle δ _r (s), and performs a correction in accordance with the correction of the front wheel rudder angle. As a result, the second rear wheel target rudder angle δ _r ′ (s) is calculated.
The second front wheel target rudder angle δ _f ′ (s) and the second rear wheel target rudder angle δ _r ′ (s) are output from the control unit 15 to the steering controller 13 as a turning angle command value.
Then, through the front wheel steering system and the rear wheel steering system, the front wheel actual steering angle δ _f ″ (s) and the rear wheel actual steering angle δ _r ″ (s) are given as actual steering amounts, and the steering is performed. The actual slip angle β _y and the actual yaw rate γ _y defined by the vehicle characteristic V (s) appear depending on the amount.

As described above, the vehicle 1 according to the present embodiment has the first front wheel target rudder angle δ _f (s) and the first target after the target slip angle β and the target yaw rate γ determined according to the steering angle θ and the vehicle speed V. A wheel steering angle δ _r (s) is calculated, and a front wheel motor target steering angle θ _m is calculated by subtracting the driver's steering angle θ _h from the first front wheel target steering angle δ _f (s). Then, with respect to the front wheel motor target steering angle theta _m, by adding the steering angle theta _h of the driver and calculates the front wheel motor target steering angle theta _m 'which suppresses the control amount of high frequency components, for variable steering ratio The second front wheel target rudder angle δ _f ′ (s) in a state where the reaction force of the motor is selectively reduced is output. In addition, the automobile 1 is controlled in response to the first front wheel target rudder angle δ _f (s) while the control amount of the high frequency component is suppressed in accordance with the first front wheel target rudder angle δ _f (s). The second rear wheel target rudder angle δ _r ′ (s) is output, and the rudder angle control is performed using these target rudder angles as turning angle command values.

  Therefore, even when a high-speed steering operation is performed by the driver, the steering wheel can be prevented from vibrating due to the reaction force of the motor, and the steering angle control between the front and rear wheels is made compatible, which makes the driver feel uncomfortable. The situation can be prevented. In addition, since the amount of steering of the front wheels caused by the driver steering at high frequency is output without being suppressed, high-frequency steering angle responsiveness can be maintained.

FIG. 11 is a diagram illustrating response characteristics with respect to a target rudder angle in the automobile 1 of the present embodiment. FIG. 12 is a diagram showing a lateral acceleration response characteristic with respect to a steering input in the automobile 1 of the present embodiment, and FIG. 13 is a diagram showing a vehicle locus in the automobile 1 of the present embodiment.
As shown in FIG. 11, compared with the case where the high frequency component is not suppressed at the first front and rear wheel target rudder angle (see FIG. 7), in the vehicle 1 of the present embodiment, the gain between the front and rear wheels is one up to the high frequency region. This prevents the driver from feeling uncomfortable.

Further, as shown in FIG. 12, the response of the lateral acceleration to the steering input also matches the target value up to the high frequency region. Therefore, as shown in FIG. 13, compared with the case where the suppression of the high frequency component at the first front and rear wheel target rudder angle is not performed, it matches the target vehicle trajectory.
In the present embodiment, the steering controller 13, the interface 14, and the control unit 15 constitute front wheel steering angle control means. The first front and rear wheel steering angle calculation unit B102 constitutes a first front wheel target steering angle calculation unit and a first rear wheel target steering angle calculation unit, and the second front wheel steering angle calculation unit B103 calculates a second front wheel target steering angle calculation unit. The second rear wheel rudder angle calculation unit B104 constitutes second rear wheel target rudder angle calculation means.

(Effect of 2nd Embodiment)
(1) Since the second front wheel target rudder angle calculating means performs correction for suppressing a high frequency component with respect to the output rudder angle by the rudder angle ratio variable motor at the first front wheel target rudder angle, the driver can operate at a high frequency. Since the front wheel turning amount by steering is output without being suppressed, high-frequency steering angle responsiveness can be maintained.

(Application examples)
In the first and second embodiments described above, the high-frequency signal is suppressed regardless of the vehicle speed with respect to the first front and rear wheel target rudder angle, but in this application example, the first front and rear wheels are controlled according to the vehicle speed. The degree to which the high frequency signal of the wheel target rudder angle is suppressed is changed.
That is, in the low vehicle speed range, the influence of the steering speed on the vehicle motion is relatively smaller than in the middle vehicle speed range and higher. Therefore, in the low vehicle speed range, at the first front and rear wheel target rudder angle. The high frequency component is greatly suppressed, and the vibration of the steering wheel due to the reaction force of the steering angle ratio variable motor is suppressed.

Specifically, in the control unit 15 of the first and second embodiments, the time constant τ ₁ of the low-pass filter Hf (s) and the time constant Ts of Mf (s) are made dependent on the vehicle speed to suppress high-frequency components. The gain to be changed is assumed to be changed.
FIG. 14 is a diagram showing a map that defines the relationship between the vehicle speed V and the time constant Ts of the low-pass filter.
As shown in FIG. 14, by defining the time constant to be smaller as the vehicle speed is smaller and to increase as the vehicle speed increases, the high frequency component of the first front and rear wheel target rudder angle is reduced in the low vehicle speed range. In the middle vehicle speed range or higher, the degree of suppression of the high-frequency component of the first front and rear wheel target rudder angle is reduced depending on the vehicle speed.

  As a result, the vibration of the steering wheel due to the reaction force of the motor can be more reliably prevented in the low vehicle speed range where the magnitude of the steering speed hardly affects the vehicle motion, and the first front and rear wheel target rudder is in the region above the middle vehicle speed range. It is possible to prevent the vibration of the steering wheel due to the reaction force of the motor while suppressing the influence on the vehicle motion due to the suppression of the high frequency component at the corner.

(Effects of application examples)
(1) Since the front wheel steering angle control means increases the degree of suppressing the high frequency component of the turning angle output from the steering output shaft as the vehicle speed is higher, the magnitude of the steering speed is less likely to affect the vehicle motion. In the vehicle speed range, the vibration of the steering wheel due to the motor reaction force can be prevented more reliably, and in the region above the middle vehicle speed range, the influence on the vehicle motion by suppressing the high frequency component at the first front and rear wheel target rudder angle is suppressed. However, the vibration of the handle due to the motor reaction force can be prevented.

1 is a diagram illustrating a configuration of an automobile 1 according to a first embodiment. It is a flowchart which shows the front-and-rear wheel steering angle calculation process which concerns on 1st Embodiment. It is a figure which shows the filter characteristic of the low-pass filter Hf (s). It is a block diagram which shows the control system structure of model follow-up control. It is a block diagram which shows the control action of the motor vehicle 1 in 1st Embodiment. It is a control block diagram including the driver | operator in the conventional motor vehicle. It is a figure which shows the response characteristic with respect to a target steering angle when not suppressing the high frequency component in a 1st front-and-rear wheel target steering angle. It is a figure which shows the response characteristic with respect to a target steering angle in the case of suppressing the high frequency component in a 1st front-and-rear wheel target steering angle. It is a flowchart which shows the front-and-rear wheel steering angle calculation process which concerns on 2nd Embodiment. It is a block diagram which shows the control action of the motor vehicle 1 in 2nd Embodiment. It is a figure which shows the response characteristic with respect to the target steering angle in the motor vehicle 1 of 2nd Embodiment. It is a figure which shows the lateral acceleration response characteristic with respect to the steering input in the motor vehicle 1 of 2nd Embodiment. It is a figure which shows the vehicle locus | trajectory in the motor vehicle 1 of 2nd Embodiment. It is a figure which shows the map which prescribes | regulates the relationship between a vehicle speed and the time constant of a low-pass filter.

Explanation of symbols

1 Automobile, 2 Steering wheel, 3 Steering input shaft, 4 VGR, 4a Rotation angle sensor, 5 Steering output shaft, 6 Pinion gear, 7 Steering rack, 8FR, 8FL, 8RR, 8RL Tie rod, 9FR, 9FL, 9RR, 9RL Wheel 10FR, 10FL, 10RR, 10RL Wheel speed sensor, 11 Rear wheel steering motor, 11a Rear wheel motor angle sensor, 12 Rear wheel steering rack, 13 Steering controller, 14 Interface, 15 Control unit, A101, B101 Target vehicle motion Calculation unit, A102, B102 First front and rear wheel steering angle calculation unit, A103, B103 Second front wheel steering angle calculation unit, A104, B104 Second rear wheel steering angle calculation unit

Claims (8)

The steering angle ratio input by the steering angle ratio variable motor that drives the steering angle ratio variable mechanism provided between the steering input and output shafts while transmitting the steering angle input to the steering input shaft by the steering operation to the steering output shaft. A front wheel steering mechanism that changes the steering and outputs to the front wheels,
A rear wheel steering mechanism that steers the rear wheels by a rear wheel steering motor;
Front wheel rudder angle control means for calculating a front wheel target rudder angle according to a steering operation while suppressing a high frequency component of a steered angle output from a steering output shaft;
Rear wheel steering angle control means for calculating a rear wheel target steering angle based on the front wheel target steering angle calculated by the front wheel steering angle control means;
With
The front wheel rudder angle control means drives the rudder angle ratio variable motor to obtain the calculated front wheel target rudder angle, and the rear wheel rudder angle control means has the rear wheel rotation to obtain the calculated rear wheel target rudder angle. A rudder angle control device that drives a rudder motor. The front wheel rudder angle control means includes
First front wheel target rudder angle calculating means for calculating a first front wheel target rudder angle based on the rudder angle input to the steering input shaft by the steering operation;
A second front wheel target rudder angle calculating means for performing correction for suppressing a high frequency component in the first front wheel target rudder angle and calculating the correction result as a second front wheel target rudder angle;
The rear wheel steering angle control means includes:
First rear wheel target rudder angle calculating means for calculating a first rear wheel target rudder angle based on the rudder angle input to the steering input shaft by the steering operation;
The second rear wheel target rudder angle is obtained by correcting the first rear wheel target rudder angle in correspondence with the output response characteristic of the second front wheel target rudder angle and calculating the correction result as the second rear wheel target rudder angle. Computing means,
The front wheel rudder angle control means drives the rudder angle ratio variable motor so as to be the calculated second front wheel target rudder angle, and the rear wheel rudder angle control means has the calculated second rear wheel target rudder angle. The rudder angle control device according to claim 1, wherein the rear wheel steering motor is driven. The second front wheel target rudder angle calculating means corrects the first front wheel target rudder angle according to the set correction characteristic,
The second rear wheel target rudder angle calculating means is based on the front wheel steering model that models the front wheel steering mechanism, the rear wheel steering model that models the rear wheel steering mechanism, and the correction characteristics. The rudder angle control apparatus according to claim 2, wherein correction is performed so that the wheel target rudder angle corresponds to the output response characteristic of the second front wheel target rudder angle.   The front wheel rudder angle control means, with the second front wheel target rudder angle calculating means, with respect to the entire output rudder angle by the steering operation at the first front wheel target rudder angle and the output rudder angle by the rudder angle ratio variable motor, The rudder angle control device according to claim 2 or 3, wherein correction for suppressing a high frequency component is performed.   The front wheel rudder angle control means performs correction for suppressing a high frequency component with respect to the output rudder angle by the rudder angle ratio variable motor at the first front wheel target rudder angle by the second front wheel target rudder angle calculating means. The rudder angle control device according to claim 2 or 3, wherein   The said front wheel steering angle control means raises the degree which suppresses the high frequency component of the turning angle output from a steering output shaft, so that a vehicle speed is high. Rudder angle control device. A steering wheel connected to a steering input shaft and performing a steering operation;
The steering angle input to the steering input shaft by the steering operation with respect to the steering wheel is transmitted to the steering output shaft, and input by a steering angle ratio variable motor that drives a steering angle ratio variable mechanism provided between the steering input and output shafts. A front wheel steering mechanism that changes the output rudder angle ratio and outputs the steering to the front wheels;
A rear wheel steering mechanism that steers the rear wheels by a rear wheel steering motor;
Front wheel rudder angle control means for calculating a front wheel target rudder angle according to a steering operation while suppressing a high frequency component of a steered angle output from a steering output shaft;
Rear wheel steering angle control means for calculating a rear wheel target steering angle based on the front wheel target steering angle calculated by the front wheel steering angle control means;
A vehicle body on which the front wheel steering mechanism and the rear wheel steering mechanism are installed;
With
The front wheel rudder angle control means drives the rudder angle ratio variable motor to obtain the calculated front wheel target rudder angle, and the rear wheel rudder angle control means has the rear wheel rotation to obtain the calculated rear wheel target rudder angle. An automobile characterized by driving a rudder motor. The steering angle ratio input by the steering angle ratio variable motor that drives the steering angle ratio variable mechanism provided between the steering input and output shafts while transmitting the steering angle input to the steering input shaft by the steering operation to the steering output shaft. A front wheel steering step for changing the wheel to output the steering to the front wheels,
A rear wheel steering step of steering the rear wheels by a rear wheel steering motor,
A front wheel rudder angle control step for calculating a front wheel target rudder angle according to a steering operation while suppressing a high frequency component of a steered angle output from a steering output shaft;
A rear wheel steering angle control step for calculating a rear wheel target steering angle based on the front wheel target steering angle;
Rudder angle ratio variable motor driving step for driving the rudder angle ratio variable motor to be the front wheel target rudder angle;
A steering angle control method, further comprising: a rear wheel steering motor driving step of driving the rear wheel steering motor to achieve the rear wheel target steering angle.

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