JP3252707B2 - Front wheel steering correction device control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a front wheel steering correction device control device for controlling a front wheel steering correction device of a vehicle direction control device including a front wheel steering device and a front wheel steering correction device.

[0002]

2. Description of the Related Art This type of vehicle direction control device is already known. The apparatus described in Japanese Patent Application Laid-Open No. 3-74265 is one example. In this vehicle direction control device, two steering controls are performed. One is to make the traveling direction of the vehicle coincide with the front-rear direction of the vehicle, and to obtain a rear wheel steering angle that makes a side slip angle (referred to as a vehicle side slip angle) of a vehicle center of gravity, which is an angle formed by the directions, zero ( The other is control for correcting the front wheel steering angle so as to suppress a change in the steering characteristic caused by the rear wheel steering angle changed by the rear wheel steering control (front wheel steering correction control). ).

The rear wheel steering angle in the device described in the above publication is determined as a product of a coefficient k, which is a function of the vehicle speed, and the front wheel steering angle. That is, a so-called vehicle speed sensitive type front wheel steering angle proportional rear wheel steering control is employed. The coefficient k is negative when the vehicle speed is lower than a certain speed (referred to as a threshold speed),
If it is equal to the threshold speed, it is set to zero, and if it is higher than the threshold speed, it is set to positive. Therefore, when the vehicle speed is lower than the threshold speed, the rear wheel steering angle is controlled in a direction opposite to the direction of the front wheel steering angle, for example, a sharp turn often performed at a low speed, such as running on a crank road or a U-turn. The turning radius at the time becomes smaller. If the vehicle speed is higher than the threshold speed, the rear wheel steering angle is controlled to the same direction as the front wheel steering angle,
For example, a change in the direction of the vehicle during a lane change during high-speed traveling can be suppressed.

When the rear wheel steering angle control is performed, the vehicle may exhibit undesirable behavior. For example, if the vehicle speed is increased while performing a steady circular turn at a certain vehicle speed,
The rear wheel steering angle in the same direction as the front wheel steering angle is increased, and the steer characteristics of the vehicle show the understeer characteristics. This is because the rear wheel steering angle promotes understeer characteristics in order to match the attitude of the vehicle with respect to changes in the direction of travel of the vehicle caused by the increase in centrifugal force caused by the increase in vehicle speed and to reduce the vehicle's sideslip angle to zero. This is because it is changed to Further, when the vehicle speed is reduced in a state where the vehicle is performing a steady circular turning at a constant vehicle speed, the rear wheel steering angle in the same direction as the front wheel steering angle is reduced, so that a so-called oversteer characteristic is obtained. Typically,
It is desirable that the vehicle exhibit weak understeer characteristics under all circumstances, and it is not desirable that the steer characteristics change with a change in vehicle speed. Such an undesired situation is also similar to the case where a method of determining the rear wheel steering angle as a value proportional to the yaw rate, which is different from the vehicle speed sensitive front wheel steering angle proportional rear wheel steering control, is also used. appear. In this case, a change in the vehicle speed during turning changes the value of the yaw rate, so that the steering characteristic changes.

Therefore, in the apparatus described in the above publication, the front wheel steering angle is always corrected in the same direction and the same magnitude as the rear wheel steering angle, so that the speed-responsive front wheel steering angle proportional rear wheel is used. The influence of the steering control on the steering characteristic is eliminated. In other words, the magnitude of the front wheel steering angle is increased for the rear wheel steering angle having the understeer characteristic, and the magnitude of the front wheel steering angle is decreased for the rear wheel steering angle having the oversteer characteristic. Understeer characteristics are obtained.

[0006]

In a conventional device represented by the device described in the above publication, the front wheel steering correction control is always performed based on a fixed correction rule, but this is not desirable. It has been found. For example, when only the rear wheel steering control is performed, the side slip angle that becomes zero does not become zero due to the execution of the front wheel steering correction control. In other words, the front wheel steering correction control reduces the effect of rear wheel steering and changes the front-rear direction of the vehicle with respect to the traveling direction of the vehicle, that is, the direction of the driver, giving the driver a sense of incompatibility. Even if the front-rear direction of the vehicle does not coincide with the traveling direction of the vehicle, the driver feels uncomfortable, but if the vehicle speed changes, the forward-rearward direction of the vehicle and the traveling direction of the vehicle are not steered even though the steering wheel is not steered. Since the degree of disagreement changes, the user feels more uncomfortable. Therefore, it is better to suppress or prohibit the front wheel steering correction control unless the front wheel steering correction control is required for another reason, for example, for ensuring the steering stability of the vehicle.

Further, the front wheel steering correction control is disclosed in
It can be used for purposes other than those described in Japanese Patent No. 4265. For example, as described later, in a rear-wheel drive vehicle, when the absolute value of the front wheel steering angle is large and the frictional force between the rear wheel and the road surface is small, it is necessary to prevent the vehicle from easily spinning. Alternatively, it is desirable to reduce the magnitude of the front wheel steering angle in order to suppress the spin that has begun to occur, and for that purpose, the front wheel steering correction control can be used. Also in this case, it is not desirable that the front wheel steering correction control is always performed based on a certain rule.

Therefore, a first invention according to claim 1 of the present application has been made to solve the problem that the steering correction control can be appropriately performed based on the magnitude of the steering instability index. An object of the second invention according to claim 2 is to eliminate particularly undesired effects of the front wheel steering correction control, and to perform front wheel steering correction control in a region where the driver is likely to feel discomfort and the necessity is low. In particular, it is to be strongly suppressed. Challenge of the third invention according to claim 3, in operator is less likely and the need to feel uncomfortable region is to the front wheel steering correction control is not performed. Problems of the fourth aspect of the present invention according to claim 4 is made as a problem that the steering instability indicator is adapted to be appropriately performed steering correction control by paying attention to whether an indication whether drift-out side shows the spin side It is a thing.

[0009]

According to a first aspect of the present invention, a front wheel steering device for changing a front wheel steering angle based on a steering angle of a steering wheel and a front wheel steering angle changed by the front wheel steering device are provided. vehicle direction control device comprising a front wheel steering correction device for correcting the front-wheel steering correction apparatus control device that controls the front wheel steering correction device, the front wheel steering correction
The correction angle of the front wheel steering angle corrected by the device is determined based on a correction rule.
Correction angle determining means for determining the
The difference between the target value and the actual value of the vehicle direction related amount, and the difference is large.
And at least one of the front and rear wheels
Less of the magnitude of the nonlinearity of the
Are determined based on one of them, and indicate steering instability,
First, maneuvering instability is an indicator that has at least a magnitude
Maneuvering instability index obtaining means for obtaining an index, and its operation
Steering instability finger obtained by the instability index obtaining means
When the absolute value of the target is small, the correction rule is applied when the index value is small.
As a correction rule, when the absolute value is large, the index value
The absolute value of the correction angle of the front wheel steering angle is larger than the small correction rule.
And a correction rule changing means for making the index value large-time correction rule
It is resolved by including. Here, the steering instability index is a value indicating the steering instability, and is a vehicle direction related amount related to the direction of the vehicle, for example, a vehicle side slip angle which is an angle formed between the front-rear direction and the traveling direction of the vehicle, and a vehicle slip angle. This is a quantity that indicates the difference between the target value and the actual value such as yaw rate and steering characteristics, and the magnitude of the possibility that the difference becomes large. It is intended to be used only in situations where the steering stability is not always good. Not something. The steering instability index may have a sign or may not have a sign. In the former case, for example, the understeer side or the drift-out side is represented by positive, and the oversteer side or the spin side is represented by negative.In the latter case, both sides are represented by a positive value. The instability is assumed to be large. Also, steering instability indicator can also be an amount which represents the nonlinearity or the like of at least one of cornering force of the front wheels and the rear wheels.

[0010]

In the second invention, the small correction value of the index value is set so that the maximum correction angle, which is the maximum absolute value of the correction angle, is smaller when the absolute value of the steering instability index is small than when the absolute value is large. The problem is solved by including a maximum correction angle decreasing rule.

In the third invention, the small index value correction rule includes a correction prohibition rule that sets the absolute value of the correction angle of the front wheel to zero when the absolute value of the steering instability index is less than a preset allowable correction value. It is solved by including.

Further, in the fourth invention, the front wheel steering correction device control device includes a correction angle determination means for determining a correction angle of the front wheel steering angle corrected by the front wheel steering correction device based on a correction rule, It is determined based on at least one of the difference between the target value and the actual value of the vehicle direction related amount related to the direction, and the possibility that the difference becomes large, and is a value indicating the steering instability, and Maneuvering instability index obtaining means for obtaining a maneuvering instability index whose sign is reversed on the spin side, and a sign of the maneuvering instability index obtained by the maneuvering instability index obtaining means is positive and negative. This is solved by including an index code corresponding correction rule changing means for changing the correction rule depending on the case.

[0014]

[0015]

According to the first aspect of the present invention, there is provided a control device for a front wheel steering correction device.
The correction rules used to determine the correction angle for the front wheel steering angle
However, the correction rule change means and the index value
It is changed to the big value correction rule. The small index value correction rule is a correction rule suitable for the case where the absolute value of the steering instability index is small, and the large index value correction rule is a correction rule suitable for the case where the absolute value of the steering stability index is large. In the case of the small index value correction rule, the absolute value of the correction angle of the front wheel steering angle is determined to be smaller than that in the case of the large index value correction rule. Therefore, when the absolute value of the steering stability index is small, the front wheel steering correction control is prohibited or suppressed to prevent the driver from feeling uncomfortable, while the understeer and oversteer become large, and In situations where steering stability should be emphasized, or in situations where the driver no longer feels uncomfortable with front wheel steering correction control, front wheel steering correction control is performed, and steering stability is improved. .

In the control device for a front wheel steering correction device according to the second invention, the small correction value for the index value is such that the maximum correction angle is made smaller when the absolute value of the steering instability index is smaller than when the absolute value is larger. Since it is assumed that the reduction rule is included, among the undesired effects of the front wheel steering correction control, particularly large ones are eliminated, and the front wheel steering correction control is particularly performed in an area where the driver is likely to feel discomfort and the necessity is low. It will be strongly suppressed. In order to prevent the correction angle of the front wheel steering angle from exceeding the maximum correction angle, for example, a temporary target value of the correction angle is first determined based on a certain rule, and the absolute value of the determined temporary target value is determined. If the value does not exceed the maximum correction angle, the actual correction angle is used as it is, and if it exceeds the maximum correction angle, the absolute value of the actual correction angle may be limited to the maximum correction angle.

In the front wheel steering correction device control device according to the third aspect of the present invention, since the small index value correction rule includes the correction prohibition rule, the absolute value of the steering instability index is less than the preset correction allowable value. In this case, the absolute value of the front wheel correction angle is set to zero, and the front wheel steering correction control is not performed. This corresponds to that the maximum correction angle is set to zero in the third invention.

In the front wheel steering correction device control device according to the fourth aspect of the invention, the correction rule changing means includes an index code corresponding correction rule changing means, so that the steering instability index indicates the drift-out side or the spin side. Is displayed, the correction rule is changed, and the front wheel steering correction control suitable for each case is performed. Changes to the correction rules can be
Allowing / prohibiting rudder correction control
Selecting the correction rule and adjusting the gain of the front wheel steering correction control
Change, change the direction of correction, etc.
Includes changes.

[0019]

As apparent from the above description, the first embodiment
Front-wheel steering correction control is prohibited when the absolute value of the steering instability indicator according to the light is small, or while being suppressed, sufficient front-wheel steering correction control line when steering is large absolute value of the stability index Therefore, it is possible to improve the steering stability while preventing the driver from feeling uncomfortable due to the front wheel steering correction control. When it is not desirable to perform the front wheel steering correction control, suppressing the control also reduces unnecessary energy consumption. According to the second aspect, it is possible to eliminate particularly undesired effects of the front wheel steering correction control, and to particularly strongly suppress the front wheel steering correction control in an area where the driver is likely to feel uncomfortable and the necessity is low. Can be. According to the third invention, when the absolute value of the steering stability index is small, it is possible to completely prevent the front wheel steering correction control from being performed, so that the driver's uncomfortable feeling due to the front wheel steering correction control is completely eliminated. be able to. According to the fourth aspect, since the correction rule can be changed depending on whether the steering instability index indicates the drift-out side or the spin side, the steering stability on both the drift-out side and the spin side is respectively improved. Can be improved by appropriate control.

[0020]

Supplementary Description of the Invention The present invention can be carried out in the following embodiments in addition to the embodiments described in the claims. The embodiments are conveniently described as an embodiment of the same type as the claims. (1) The steering instability index obtaining means is obtained by a yaw rate sensor for obtaining an actual yaw rate of the vehicle, target yaw rate determining means for determining a target yaw rate based on a steering angle and a vehicle speed of a steering wheel, and a yaw rate sensor. A yaw rate-dependent steering instability that obtains the absolute value of the steering instability index as a larger value when the absolute value of the difference between the actual yaw rate and the target yaw rate determined by the target yaw rate determination means is larger than when the absolute value is smaller. The front wheel steering correction device control device according to any one of claims 1 to 4 , further comprising an index acquisition unit. (2) The vehicle direction control device includes a vehicle speed sensitive type rear wheel steering device that changes a rear wheel steering angle based on the steering angle of the steering wheel and the traveling speed of the vehicle, and the steering instability index obtaining means However, if the absolute value of the rear wheel steering angle changed by the rear wheel steering device is greater than or equal to a preset absolute rear wheel steering angle, and if the steering characteristic shows oversteer characteristics, compared claim 1-4 comprising a wheel steering angle relying type steering instability indicator acquiring means after acquiring a greater value of the absolute value of the steering instability indicators, the front wheels according to any one of embodiments to claim 1 Steering correction device control device. (3) The steering instability index acquiring means determines that the slip state of the rear wheels is worse than a preset slip state and that the steering angle of the steering wheel is a preset steering wheel steering angle. If it is more, according to claim 1-4 comprising a slip condition relying type steering instability index acquisition means for acquiring as a large value of the absolute value of the steering instability indicator than otherwise, embodiments claim 1, 3. The control device for a front wheel steering correction device according to any one of 2. As an example of a case where the front wheel steering correction device control device of this aspect is effective, in a rear-wheel drive vehicle,
In some cases, the absolute value of the front wheel steering angle is large and the frictional force between the rear wheel and the road surface is small. In such a case, since the vehicle is likely to spin, when the absolute value of the steering instability index is large enough to spin the vehicle, the front wheel steering correction control is performed to suppress the spin, Otherwise, the control is not performed, or the control amount of the front wheel steering correction control is reduced. As described in the embodiment, the front wheel steering correction device control device according to the first to third embodiments acquires the steering instability index by different methods. (4) The vehicle direction control device includes a vehicle speed-responsive rear wheel steering device that changes a rear wheel steering angle based on a steering angle of the steering wheel and a traveling speed of the vehicle, and the correction rule changing unit includes: The index value small correction rule when the absolute value of the steering instability index is small and the index value large correction rule when the absolute value of the steering stability index is large are compared with the index value large correction rule when the small index value correction rule is used. 2. The front wheel steering correction device control device according to claim 1, wherein the control unit changes the absolute value of the correction angle of the front wheel steering angle to be smaller than that in the case of the correction rule. In the front-wheel steering correction device control device of this aspect, when the running speed of the vehicle is increased or decreased while the steering angle of the steering wheel is kept constant, the side slip angle of the vehicle may change. It is suppressed and the driver's discomfort is reduced. In other words, especially when there is a possibility that the steering stability of the vehicle may be deteriorated, priority is given to the front wheel steering correction control, and when there is no such fear, priority is given not to giving the driver an uncomfortable feeling.

[0021]

FIG. 1 is a diagram showing the configuration of a vehicle direction control device including a front wheel steering correction device control device according to an embodiment of the present invention. In FIG. 1, reference numeral 10 denotes an AFS (Active) which is a main component of the front wheel steering correction device.
(Front Steer) actuator. ARS 12 is a main component of the rear wheel steering system.
(Active Rear Steer) actuator. The steering control device shown in FIG. 1 can execute both rear wheel steering control and front wheel steering correction control. Since the AFS actuator 10 and the ARS actuator 12 are substantially the same, only the configuration of the AFS actuator 10 will be representatively described.

As shown in FIG. 2, the AFS actuator 10 has a hollow cylindrical housing 52. The housing 52 is configured by closing both ends of a thin cylindrical main body 54 (for example, made of a pipe) having the same diameter and extending straight, with a pair of closing members 56 and 58. A drive shaft 60 passes coaxially through the housing 52. The drive shaft 60 is positioned by the closing members 56 and 58 so as to be coaxial with the housing 52, and is supported so as to be slidable in the axial direction. Also,
The drive shaft 60 is spline-fitted with the closing member 56, and is prevented from rotating with respect to the housing 52.

A brushless motor 64 (hereinafter simply referred to as a motor) is provided in the housing 52. The motor 64 includes a rotor 66 and a stator 6 which are both cylindrical.
8 are arranged coaxially and in such a manner that their positions in the thrust direction coincide with each other. The rotor 66 is of a four-pole type in which permanent magnets are mounted in such a manner that the polarity alternates between the north pole and the south pole in the circumferential direction. Further, the stator 68 corresponds to the rotor 66 and the armature coil 7
0 is a three-pole type mounted in a state in which the polarity alternates between the north pole and the south pole in the circumferential direction. Stator 68 is located outside rotor 66 with a suitable magnetic gap. On the other hand, the drive shaft 60 is coaxially inserted into the hollow hole of the rotor 66. The rotor 66 is disposed on the outer peripheral surface of the drive shaft 60 with a suitable gap therebetween, and both ends are supported by a pair of bearing mechanisms 74 mounted on the housing 52 so as to be rotatable and immovable in the axial direction. Therefore, if the armature coils 70 of the stator 68 are sequentially excited, the rotor 66 is rotated accordingly. It should be noted that the rotor 66 may use less than four permanent magnets, may use more than four permanent magnets, or may use a brushless motor 64.
Alternatively, a motor with a brush can be used.

The rotation of the motor 64 is converted into linear motion by a screw mechanism 78 as a motion conversion mechanism,
Is transmitted to A screw 80 is provided on a part of the outer peripheral surface of the drive shaft 60.
Is formed, and a nut 82 screwed with the external thread 80 is supported by the housing 52 so as to be rotatable and immovable in the axial direction. The screw mechanism 78 is formed by screwing the male screw 80 and the nut 82 together. In this embodiment, both the male screw 80 and the nut 82 are trapezoidal screws. Further, the rotation of the motor 64 is not directly transmitted to the screw mechanism 78,
Is transmitted via the speed reducer 90 in order to boost the rotational force of the motor. The reduction gear transmission 90 includes two planetary reduction gears 9.
2, 94 are connected in series with each other.
The planetary speed reducers 92 and 94 include (a) one sun gear 100, (b) one ring gear 102, and (c) a plurality of planetary gears 104 arranged between the sun gear 100 and the ring gear 102. And (d) a carrier 106 that supports each of the planetary gears 104 so as to be able to rotate while maintaining their relative positional relationship constant.

The two ring gears 102 are connected to the housing 52
It is fixed to. The two sun gears 100 are both hollow, and both of them are coaxially penetrated by the drive shaft 60. As a result, the two planetary speed reducers 92 and 94 are arranged side by side in the axial direction of the drive shaft 60. ing.
Among the planetary speed reducers 92 and 94, the rotor 66
Are referred to as an input-side reduction gear 92 and those close to the screw mechanism 78 are referred to as an output-side reduction gear 94. In the input side reduction gear 92, the sun gear 100 is rotatable integrally with the rotor 66. On the other hand, in the output side reduction gear 94, the sun gear 100 is connected to the carrier 10 of the input side reduction gear 92.
6 and can be rotated integrally with the output side speed reducer 9
The fourth carrier 106 is rotatable integrally with the nut 82.

Therefore, when the rotor 66 rotates, the sun gear 100 and the planetary gear 104 rotate in the input side reduction gear 92, and the sun gear 100
Is reduced and transmitted to the carrier 106.
Further, with the rotation of the carrier 106, the output side reduction gear 9
4, the sun gear 100 and the planetary gear 104
Rotate, and the rotation speed of the sun gear 100 is reduced and transmitted to the carrier 106. The nut 82 rotates with the rotation of the carrier 106 of the output side reduction gear 94, and the rotation is converted into linear motion by the screw mechanism 78, and the drive shaft 60 moves in the axial direction.

The AFS actuator 10 further includes a rotation position sensor 110 for detecting the rotation position of the rotor 66.
And an axial position sensor 112 for detecting the axial position of the drive shaft 60. In the present embodiment, the rotation position sensor 110 is a magnetic type (an example of a non-contact type), and the permanent magnet 11 that rotates together with the rotor 66.
6 and three magnetic detection elements 118 whose positions are fixed. The magnetic detection element 118 is disposed close to the permanent magnet 116 and outputs a pulse signal that changes in response to detecting the passage of the permanent magnet 116, thereby detecting the rotational position (relative position) of the rotor 66. Is done. One example of the magnetic sensing element 118 is a Hall element.
The rotation position sensor 110 detects the motor 6 during the rear wheel steering control.
4 is used to make the rotation angle change amount equal to the command value. In contrast, the axial position sensor 112
In the present embodiment, a potentiometer type (contact type)
It has been. The axial position sensor 112 is connected to the drive shaft 60.
And a linearly displaced slider and a fixed position electrical resistor. The electric resistor is provided so as to always contact the slider, the electric resistance value changes according to the position of the slider, and outputs an electric signal according to the change, whereby the position of the drive shaft 60 in the axial direction ( Absolute position) is detected. The axial position sensor 112 is used to initialize the rotational position of the motor 64 (return to the origin) prior to the rear wheel steering control.

As shown in FIG. 1, connecting portions 130, 132, 134 and 136 are formed at both ends of the drive shaft 60 of the AFS actuator 10 and the ARS actuator 12, respectively. The tie rod arms 138, 139, and 14 are connected to the connecting portions 130, 132, 134, and 136, respectively.
0, 141 are connected, and the tie rod arms 138, 139, 140, 141 are connected to knuckle arms 142, 143, 144, 145, respectively. Knuckle arms 142, 143, 144, 1
45 is a steering shaft 146, 148, 150, 15
2 and attached to the vehicle so as to be rotatable around the center. Therefore, AFS, ARS actuator 10,
When the drive shaft 60 moves in the left-right direction of the vehicle body by operating the twelve motors 64, the knuckle arms 142, 143, 1
The steering angles of the front and rear wheels are changed by rotating the wheels 44 and 145, respectively. Thus, the AFS actuator 1
0, tie rod arms 138 and 139 and knuckle arms 142 and 143 constitute a front wheel steering correction device.
0, 141 and the knuckle arms 144, 145 constitute a rear wheel steering device.

The AFS actuator 10 is held by a holding mechanism 160 at two positions separated in the axial direction of the main body 54 so as to be able to translate in the left-right direction of the vehicle body and not to rotate. Also, the main body 5 of the AFS actuator 10
A male screw member 162 is integrally attached to the outer circumference of the fourth member 4. The male screw member 162 is screwed with the female screw member 164. The male screw member 162 and the female screw member 164 constitute a screw mechanism with zero reverse efficiency. A screw mechanism with zero reverse efficiency is provided with a male screw member and a female screw member screwed to each other, and by applying a rotational force to one of the two screw members, the two screw members can be relatively moved in the axial direction, This is a screw mechanism that cannot rotate relative to each other even when an axial force is applied to the two screw members. For example, the screw mechanism is constituted by a trapezoidal screw in which the lead angle of the screws of the two screw members is less than the friction angle. A gear 166 is formed at one end of the female screw member 164 in the axial direction, and is engaged with the gear 168.

The female screw member 164 is prevented from moving in the axial direction by the engagement of the gear portion 166 with the gear 168 and the abutment of the end surface 170 on the side opposite to the gear portion 166 with the abutment portion 172. At the same time, it is held by a holding mechanism 174 so as to be rotatable around a rotation axis parallel to the left-right direction of the vehicle body. The gear 168 is the steering shaft 18
0 is fixed to the lower end of the steering shaft 18.
The steering wheel 182 is fixed to the upper end of the zero. When the steering wheel 182 is rotated, the steering shaft 180, the gear 168, and the female screw member 164 are respectively rotated, and the male screw member 162 is rotated.
The whole of the AFS actuator 10 integrally mounted with the is moved in the left-right direction of the vehicle. By this movement, the left and right front wheels FL and FR are steered as in the case where the motor 64 in the AFS actuator 10 is operated. AFS actuator 10, tie rod arms 138, 139, knuckle arms 142, 143,
Male screw member 162, female screw member 164, gear 168, steering shaft 180, steering wheel 18
2 and the like constitute a front wheel steering device.

Further, an electric power steering device 186 is attached to the steering shaft 180. The electric power steering device 186 includes a motor 188 (not shown) inside, and can apply a rotational torque to the steering shaft 180 via a screw mechanism 190 (not shown). The magnitude of the applied torque is determined based on the magnitude of the torque _Trq detected by the torque sensor 192, based on the AFS / PS ECU (Ele).
(Ctronic Control Unit) 200.

The AFS / PS ECU 200 includes a motor 188 (not shown) in the electric power steering device 186.
The power steering device is controlled by controlling the supply voltage and current to the motor, and the front wheel steering correction control is performed by controlling the supply voltage and current to the motor 64 in the AFS actuator 10. The operation as the power steering device is the same as that of the conventional device, and the description is omitted. In order to perform the front wheel steering correction control, the data acquired by the AFS / PS ECU 200 includes (1) a correction angle Δ determined based on the output of the rotational position sensor 110 in the AFS actuator 10.
θ _f , (2) actual rear wheel steering angle θ _r output from the ARS ECU 202, (3) steering steering angle δ _f determined based on the output of the steering angle sensor 204 (the direction in which the vehicle turns left is (4) the actual yaw rate γ output by the yaw rate sensor 206, and (5) the rotational speeds of the left and right front wheels FL and FR obtained based on the signals output by the wheel rotation sensors 208 and 210, respectively. V _L and V _R. AFS based on these data
The rotation control of the motor 64 inside the actuator 10 is performed according to a procedure described later, and the front wheel steering correction control is performed. Note that the steering angle δ _f directly obtained from the output of the steering angle sensor 204 is different from the position sensor 21.
Front wheel steering angle θ _f ′ (= δ _f / N,
N: steering steering angle front wheel steering angle ratio). Moreover, the actual front wheel steering angle theta _f which is the sum of the front wheel steering angle theta _f 'obtained from the output, the correction angle [Delta] [theta] _f which is determined from the output of the rotational position sensor 110 of the position sensor 212, the output of the position sensor 214 It may be an embodiment obtained directly from. In FIG.
The positions where the position sensors 212 and 214 are attached are also shown.

The ARS ECU 202 acquires various data from the rotational position sensor 110, the yaw rate sensor 206, and the wheel rotation sensors 208 and 210 in the ARS actuator 12, and based on these data, the motor 64 in the ARS actuator 12 The rear wheel steering control is performed by performing the rotation control of the vehicle according to a procedure described later. Note that wheel steering angle theta _r after obtained from the output of the rotational position sensor 110 may be an embodiment that is acquired by the position sensor 216. FIG. 1 also shows the mounting position of the position sensor 216.

FIG. 3 shows the AFS / PS ECU 200.
4 is a flowchart illustrating a program of rear wheel steering control and front wheel steering correction control stored in a ROM of a computer serving as a main body of the ARS ECU 202. In FIG. 3, first, in step 100 (hereinafter simply referred to as S100; the same applies to other steps), a target rear wheel steering angle θ _r ^* is calculated based on the following equation. ^{_{θ r * = k r · γ}} ··· (1) k r = ^{_{[L f · m · V 2 -2}} · L · L r · K r) ] _{/ 2 · L · K r ·} V ··· ( 2) it should be noted that equation (2), (in the yaw rate proportional rear wheel steering control based on the 1), is a formula showing the condition that the steering angle [delta] _f is the side slip angle is zero in certain cases, the steering it may perform a calculation based on the more general expression that the steering angle [delta] _f is satisfied even if not constant. γ is the actual yaw rate acquired by the yaw rate sensor 206. That is, yaw rate proportional rear wheel steering control is performed. M is the vehicle weight, V is the vehicle speed,
_Lf is the distance between the vehicle center of gravity and the front wheel axle, _Lr is the distance between the vehicle center of gravity and the rear wheel axle, L (= _Lf +
L _r ) is the wheelbase, and K _r is the cornering power of the rear wheel. Vehicle speed V, for example, left and right front wheels rotational speed V _L, is the value of the larger of V _R. In the present embodiment, the yaw rate proportional rear wheel steering control is used as the rear wheel steering control, but the steering wheel angle proportional rear wheel steering control for making the steering wheel angle and the rear wheel steering angle proportional, and the front wheel Other rear wheel steering control such as front wheel steering force proportional rear wheel steering control for making the steering force proportional to the rear wheel steering angle may be used.

Next, in S102, the target rear wheel steering angle θ _r ^* calculated in S100 and the ARS actuator 1
So that the difference between the wheel steering angle theta _r after is obtained based on the output of the second inner rotational position sensor 110 is zero, ARS
The motor 64 in the actuator 12 is an ARS ECU
202 is activated by the rear wheel steering angle theta _r is changed. Next, in S104, the gain K and the code SI
The value with GN is determined. The size of the gain K determines the size of the correction angle [Delta] [theta] _f, sign SIGN value (± 1
Take the only) is to determine the orientation of the correction angle [Delta] [theta] _f, for a method of determining these values will be described later. Based on the values of the gain K and the sign SIGN, S106
The target front wheel steering angle θ _f ^* is calculated by the following equation. θ _f ^* = θ ′ + Δθ _f = δ _f / N + SIGN · K · δ _f (3) where θ ′ = δ _f / N is a front wheel steering angle determined only by the front wheel steering device, and Δθ _f = SIGN ・ K ・ δ
_f is a correction angle by the front wheel steering correction device.

Next, in S108, a maximum correction angle limiting process is performed. This process (3) of the second term on the right side value, i.e., if it exceeds the maximum correction angle correction angle [Delta] [theta] _f is predetermined, a process to limit the correction angle to the maximum correction angle, wherein This corresponds to the maximum correction angle reduction rule. When the maximum correction angle limiting process is performed, the formula (3) does not necessarily have to be used as a method of calculating the target front wheel steering angle θ _f ^* . as correction angle [Delta] [theta] _f may be equal to the rear wheel steering angle theta _{r. ^{θ f * = δ f / N}} + k r · γ ··· (4) Conversely, if the target front wheel steering angle theta _f ^* is calculated by the equation (3), the correction angle [Delta] [theta] _f by (3) The size is
It depends on the value of the gain K, as will be described later, the value of the gain K is changeable as necessary to suppress the magnitude of the correction angle [Delta] [theta] _f by suppressing the magnitude of the gain K Can be. Therefore, in this case, the maximum correction angle limitation processing is not necessarily required.

Next, in S110, the target front wheel steering angle θ _f ^* calculated in S108 and the AFS actuator 1
0, the front wheel steering angle θ _f determined by the outputs of the rotational position sensor 110 and the steering angle sensor 204.
AFS / PS ECU 20 so that the difference from
0 the motor 64 in the AFS actuator 10 is actuated by the front wheel steering angle theta _f is changed, then, S
The process from 100 is repeated. Note that S10 in FIG.
The front wheel steering correction control executed in 4-S110 is as follows.
This can be performed independently of the rear wheel steering control executed in S100 and S102. Depending on the content of the front wheel steering correction control, the rear wheel steering control is not necessarily indispensable, and only the front wheel steering correction control may be performed.

FIG. 4 is a graph showing one mode of changing the correction rule. The absolute value of the steering instability index β ' is a threshold
In the case where it is smaller than β ′ ₀ (| β ′ | <β ′ ₀ ) , the gain K is determined by the gain line K _I , and when the absolute value of the steering instability index β ′ is equal to or larger than the threshold value β ′ ₀ ( |
β ′ | ≧ β ′ ₀ ) is determined by the gain line K _II . " The absolute value of the steering instability index β '
Threshold beta _'0 is smaller than (| β' | <β ' 0) to is the index value small when the correction rule is that the gain K is determined by a gain linearly K _I "," steering instability index
When the absolute value of β ′ is equal to or greater than the threshold β ′ ₀ (| β ′ | ≧
β ′ ₀ ), the gain K is determined by the gain straight line K _II ”. Although the intercept of the gain straight lines K _I and K _{II in} FIG. 4 is zero, the intercept may be other than zero, and the gain K is smaller than that when the steering instability index β ′ is less than β ′ _0. Then, the magnitude of the correction angle Δθ _f of the front wheel steering angle θ _f may be reduced.

FIG. 5 is a graph showing another modification of the correction rule. In this embodiment, the gain straight line K _I and the gain straight line K _II in the embodiment shown in FIG. 4 are smoothly connected so that the gain K is continuous in the entire section of the steering instability index β ′. The following equation can be used as an example of a method for smoothly connecting two gain straight lines. K = {K _I ( | β ′ | ≦ β ′ ₋₁ ), K _II (β ′ ₁ ≦ | β ′ | ), K _III (β ′ ₋₁ ≦ | β ′ | ≦ β ′ ₁ )} · (5) K _III = | β '| · {dK _I / d | β' | + S · (dK _I / d | β '| -dK _II / d | β' | )} (6) S = [2 · {(| β '| -β' -1) / (β '1 -β' -1)} 2 (β '-1 ≦ | β' | ≦ β '0), 1-2 · { ( | Β ′ | −β ′ ₁ ) / (β ′ ₁ −β ′ ₋₁ )｝ ² (β ′ ₀ ≦ | β ′ | ≦ β ′ ₁ )] (7) It can be considered to include three correction rules. {K _I ( | β '| ≤β'- ₁ )} and {K _II
(Β ′ ₁ ≦ | β ′ | )} between the two correction rules,
By inserting a correction rule represented by {K _III (β ′ ₋₁ ≦ | β ′ | ≦ β ′ ₁ )}, the driving instability index β ′
When the absolute value | β ′ | of the value fluctuates around β ′ ₀ , it is possible to prevent the gain K from changing discontinuously. In addition,
In the equations (5) to (7), β ′ ₁ −β ′ ₀ = β ′ ₀
Although -β'- ₁ is assumed, this assumption need not be used.

FIG. 6 is a graph showing still another embodiment in which the correction rule is changed according to the absolute value of the steering instability index β '. The gain K is increased stepwise as the absolute value of the steering instability index β 'increases. β ′ ₀ ,
The values of β ′ ₁ , β ′ _2, etc. and K ₁ , K ₂ , K _3, etc. are arbitrary. This aspect indicates that the modification of the correction rule may be made by switching between three or more different correction rules. Even at the time of switching the correction rule, another correction rule is inserted to prevent the change in the gain K from being discontinuous when switching to each correction rule, as in the method of changing the correction rule shown in FIG. May be. FIG.
In the case of | β ′ | <β ′ ₀ , the gain K is set to zero and the correction of the front wheel steering angle is prohibited. That is,
β ′ ₀ includes the correction prohibition rule set as the correction allowable value. Correction rules other than those shown in FIGS. 4 to 6 and methods for changing them may be used.

Next, a specific example of the steering instability index β 'will be described. As steering instability indicator beta ', it can be used yaw rate deviation [Delta] [gamma]. This is represented by the following equation. β '= Δγ = γ · ( γ * -γ) ··· (8) γ * = V · δ f / {N · L · (1 + K h · V 2)} ··· (9) K h = - {M / (2 · L ² )} · (L _f · K _f −L _r · K _r ) / (K _f · K _r ) (10) where γ ^* is the steering angle δ _f target yaw rate that changes depending on the vehicle speed V and, the K _f is the front wheel cornering power.

K_hIs the stability factor.
If the value is positive, the vehicle steer characteristics are understeer characteristics
And if it is negative, it has oversteer characteristics. However
And stability factor K_hIs only vehicle design variables?
This value is always calculated from the actual vehicle
It does not always show tare characteristics. On the other hand,
It can be seen that the sign of the deviation Δγ represents the steering characteristics of the vehicle.
It is clear from FIG. According to FIG. 7, the vehicle is viewed from above.
When the counterclockwise yaw rate is positive, the yaw rate
If the value of the difference Δγ is positive, the vehicle shows understeer characteristics.
If it is negative, it indicates that it exhibits oversteer characteristics.
I understand. Note that this target yaw rate γ ^*The value of
Constant front wheel steering angle θ_f(Correction angle Δθ_fIs not taken into account
Yaw rate γ and vehicle speed V when making a steady circular turn
Is derived theoretically, for example, the front wheel
Steering angle θ_fIs more general, even if
Expressions may be used.

The yaw rate deviation Δγ expressed by the equations (8) to (10) becomes larger as the difference between the target yaw rate γ ^* and the actual yaw rate γ increases when the actual yaw rate is the same . In this example, the yaw rate deviation Δγ that increases as the difference between the theoretically derived target yaw rate γ ^* and the actual yaw rate γ increases is used as the steering instability index β ′. When the target front wheel steering angle θ _f ^* is calculated using Expression (3), the sign SIGN is the same as the sign of the yaw rate deviation Δγ. SIGN = sgn (Δγ) (11) That is, in the cases (i) and (iii) shown in FIG.
The correction angle Δθ _f is positive, and in the cases (ii) and (iv) , it is negative. In the case of (i) and (iii), the front wheel steering angle θ _f
Is increased, and in cases (ii) and (iv), the front wheel
Is the absolute value of the steering angle theta _f is reduced. (8),
The value of β ′, SIGN calculated by equation (11) is
Substituting into equation (3), the target front wheel steering angle θ _f ^* is calculated. Thus, since SIGN is used in S106 of FIG. 3, the present embodiment includes the index code corresponding correction rule changing means.

FIG. 8 is a graph showing a mode in which a different amount from the yaw rate deviation Δγ is used as the steering instability index β ′. In this embodiment, the rear wheel slip ratio ρ _r , which is an example of the amount indicating that the rear wheel slip state is deteriorating, is larger than a predetermined rear wheel slip ratio threshold ρ _rth (positive value). _If the steering steering angle _δf is large and the absolute value of the steering angle _δf is larger than a preset absolute steering angle threshold _δfth (positive value), the steering instability index β ′ is determined to be large. That is, when the rear wheel is large steering angle [delta] _f by state easy to slip, as a likely vehicle lateral slip of the rear wheels is further increased, it being the steering instability indicator beta 'is large.

Determining whether the steering instability index β 'of the vehicle is large by this method is particularly effective when the traction of the rear wheels is reduced due to a sudden start or the like in a rear-wheel drive vehicle. is there. In Figure 8, in response to changes in the rear wheel slip ratio [rho _r and steering angle [delta] _f, but steering instability indicator beta 'it is smoothly changed, may be being changed stepwise. When the target front wheel steering angle θ _f ^* is calculated using the equation (3), the sign SIGN is used.
, As corrected orientation the absolute value of the front wheel steering angle theta _f is smaller is performed, are those represented by the following equation. SIGN = −sgn (δ _f ) (12)

FIG. 9 is a graph showing a mode in which another amount is used as the steering instability index β '. This mode is based on the premise that rear wheel steering control is performed, and the yaw rate deviation Δγ is negative, and the absolute value of the yaw rate deviation Δγ is a predetermined yaw rate deviation threshold Δγ _th (negative value) . larger than the absolute value, further, the absolute value of the rear wheel steering angle theta _r is preset rear wheel steering angle threshold theta _rth (positive value)
If it is larger, the steering instability index β 'is determined to be large. When the yaw rate deviation Δγ is negative and its absolute value is large, the vehicle's steering characteristics show strong understeering characteristics.

[0047] In such a case, by the rear wheel steering control, should deli, the absolute value of a certain size of the rear wheel steering angle theta _r of the rear wheel steering angle is controlled such that slip angle approaches zero It should be. The absolute value of the rear wheel steering angle theta _r so that they become really large, even though the amount of control by the rear-wheel steering control is large, if more understeer characteristic is strong, slip angle of the vehicle is increased It is said that the tendency is large. When the target front wheel steering angle θ _f ^* is calculated using the equation (3), the sign SIGN is:
As correction of the same direction as the rear wheel steering angle theta _r is made, it is to be determined by the following equation. SIGN = sgn (θ _f ) (13)

The steering instability index β 'may be obtained based on an amount other than the above amounts. For example, a mode in which the steering instability index β ′ is determined as a larger value when the absolute value of the difference between the target sideslip angle of the vehicle and the actual sideslip angle is larger than when the absolute value is smaller, or at least for the front and rear wheels. Focusing on the relationship between the cornering force and the sideslip angle, it is possible to adopt a mode in which the steering instability index β ′ is determined as a smaller value in a situation where these relationships are nearly linear than in a situation where the relationship is nearly nonlinear. .

In still another embodiment, a plurality of the above-described modes of obtaining the steering instability index β ′ may be simultaneously employed in any combination. In this case, a plurality of values of the steering instability index β 'that are different for each acquisition mode are acquired. Therefore, for example, the front wheel steering correction control corresponding to the situation where the largest one of the plurality of values of the steering instability index β ′ is selected and the maximum steering instability index β ′ is obtained is performed. You can make it happen. The steering instability index β ′ obtained in the various aspects described above can be used as the steering instability index β ′ shown in FIGS. 4 to 6, 8, and 9, and thereby various embodiments can be used. The control device for the front wheel steering correction device is obtained.

FIG. 10 shows the maximum absolute value shown in S108 of FIG.
FIG. 9 is a graph for explaining an example of a correction angle limiting process.
You. This process is corrected by using the maximum correction angle
Angle Δθ _fAll of the above
It can be used in common in the embodiments. In addition,
In the following description, the target front wheel steering angle θ_f ^*Is the formula (3)
It is assumed to be calculated using FIG. 10 shows the following equation.
Is shown. θ_f ^* _{max (+/-)}= Δ_f/ N ± | K_max│ ・ δ_f (Same order as double sign) ... (14) Two straight lines (simply θ_f ^* _{max +}Ma
Or θ_f ^* _max-Is the goal determined by equation (3).
Front wheel steering angle θ_f ^*Indicates the boundary of the range. Note that K
_maxIs the maximum value of the gain K. FIGS.
According to the method of determining the gain K shown in FIG.
Since there is no maximum value, the steering instability index β 'is large.
Then, the two straight lines θ shown in FIG._f ^* _{max +}, Θ_f
^* _max-(Straight line δ_f/ N)
Becomes larger, and the correction angle Δθ_fThe size of
May be unnecessarily large.

Accordingly, the correction angle Δθ _f is limited to the range of ± θ _M and the target front wheel steering angle θ _f ^* is offset from the straight line δ _f / N by ± θ _M, respectively, expressed by the following equation: The value is limited to a value within an area between the straight lines of the book. ^{_{θ f * M (+/-) =}} δ f / N ± θ M ( double signs in same order) (15) that is, is calculated based on the equation (3), 2 represented by equation (14) The target front wheel steering angle θ _f ^* limited to the range sandwiched by the two straight lines is expressed by two straight lines θ _f indicated by Expression (15).
If ^* _{M +} and theta _f ^* _M- value of sandwiched within the area, it is adopted as the actual target front wheel steering angle theta _f ^*, otherwise corresponding to the steering angle [delta] _f value at that time One of the two values calculated by the equation (15) is adopted as the target front wheel steering angle θ _f ^* . In other words, the absolute value of the correction angle Δθ _f becomes the maximum value θ _M
It is not to be increased beyond.

In this way, the value of the target front wheel steering angle θ _f ^* calculated using the equation (3) is a temporary value. The method of calculating the provisional target front wheel steering angle θ _f ^* is not limited to the method using the equation (3), and for example, a method similar to the apparatus described in the above publication may be used. However, the maximum value theta _M has to be smaller than the greater when steering instability indicator beta 'is small. As a method of determining the maximum value θ _M , for example, a method of setting the gain K to the maximum value θ _M shown in FIGS. 4 to 6, 8, and 9 can be used. Is also good.

FIG. 11 is a graph showing another mode of the maximum absolute correction angle limiting process in S108 of FIG. FIG.
While the mode shown in FIG. 0 suppresses the front wheel steering correction control by limiting the magnitude of the correction angle Δθ _f , this mode is used when the steering instability index β ′ exceeds β ′ _1. By limiting the value of the gain K to the maximum value _KMAX and using the value of the gain K to determine the correction angle Δθ _f by, for example, the second term on the right side of the equation (3), the correction angle Δ
It is to limit the size of the theta _f. FIG. 11 shows a mode based on the correction rule of FIG. 4. The correction angle Δθ _f based on the magnitude of the gain K is shown in FIGS. 5, 6, 8 and 9.
Is determined, the maximum absolute correction angle limiting process similar to the present embodiment can be performed.

Although some embodiments of the present invention have been described with reference to the drawings, various modifications and improvements may be made based on the knowledge of those skilled in the art without departing from the scope of the claims. The present invention can be carried out in the form in which is performed.

[Brief description of the drawings]

FIG. 1 is a system diagram showing a configuration of a vehicle equipped with a vehicle direction control device including a front wheel steering correction device control device according to an embodiment of the present invention.

FIG. 2 is a front sectional view showing a configuration of an AFS actuator 10 and an ARS actuator 12 in the vehicle direction control device.

FIG. 3 is a flowchart showing a control program in the vehicle direction control device.

FIG. 4 is a graph showing one mode of changing a correction rule in the front wheel steering correction device control device.

FIG. 5 is a graph showing another mode of changing a correction rule.

FIG. 6 is a graph showing still another mode for changing a correction rule.

FIG. 7 is a diagram showing a relationship between a yaw rate deviation Δγ and a steering characteristic of a vehicle.

FIG. 8 is a graph showing one mode of acquiring a steering instability index β ′ in the front wheel steering correction device control device.

FIG. 9 is a graph showing another mode for obtaining the steering instability index β ′.

FIG. 10 is a graph showing one mode of a maximum absolute correction angle limiting process in S108 of FIG. 3;

FIG. 11 is a graph showing an embodiment in which the magnitude of the correction angle Δθ _f is limited without using the maximum absolute correction angle limiting process in S108 of FIG. 3;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 AFS actuator 12 ARS actuator 52 Housing 54 Body part 60 Drive shaft 64 Brushless motor or just motor 78 Screw mechanism 90 Reduction mechanism 92, 94 Planetary reduction gear 110 Rotational position sensor 112 Axial position sensor 130-136 Connection part 138-144 Tie rod arms 146 to 152 Knuckle arm 160 Holding mechanism 162, 164 Screw member 166 Gear part 168 Gear 180 Steering shaft 182 Steering wheel 186 Electric power steering device 192 Torque sensor 200 AFS / PS ECU 202 ARS ECU 204 Steering steering angle sensor 206 Yaw rate sensor 208, 210 Wheel rotation sensor 212-216 Position sensor

Claims (4)

(57) [Claims] 1. A vehicle direction control device comprising: a front wheel steering device that changes a front wheel steering angle based on a steering angle of a steering wheel; and a front wheel steering correction device that corrects a front wheel steering angle changed by the front wheel steering device. A front wheel steering correction device control device that controls the front wheel steering correction device, wherein a correction angle determination unit that determines a correction angle of the front wheel steering angle corrected by the front wheel steering correction device based on a correction rule; At least one of the difference between the target value and the actual value of the vehicle direction related amount related to the direction, the magnitude of the possibility that the difference becomes large, and the magnitude of the non-linearity of at least one cornering force of the front wheels and the rear wheels. Determined based on one,
Maneuvering instability index acquisition means that represents maneuvering instability, and acquires at least a maneuvering instability index that is an index having a magnitude, and the absolute value of the maneuvering instability index acquired by the maneuvering instability index acquiring means is When smaller, the correction rule is an index value small correction rule, and when the absolute value is large, an index value large correction rule in which the absolute value of the correction angle of the front wheel steering angle is larger than the small index value correction rule. And control means for changing the correction rule. 2. The maximum value correction rule which is the maximum value of the absolute value of the correction angle is smaller when the absolute value of the steering instability index is smaller than when the absolute value of the steering instability index is larger. The control apparatus according to claim 1 , further comprising a correction angle reduction rule. 3. The small correction value for index value includes a correction prohibition rule that sets the absolute value of the correction angle of the front wheel to zero when the absolute value of the steering instability index is smaller than a preset allowable correction value. The control device for a front wheel steering correction device according to claim 1 or 2 , wherein: 4. A vehicle direction control device comprising: a front wheel steering device that changes a front wheel steering angle based on a steering angle of a steering wheel; and a front wheel steering correction device that corrects a front wheel steering angle changed by the front wheel steering device. A front wheel steering correction device control device that controls the front wheel steering correction device, wherein a correction angle determination unit that determines a correction angle of the front wheel steering angle corrected by the front wheel steering correction device based on a correction rule; A difference between the target value and the actual value of the vehicle direction related amount related to the direction, and a value representing the steering instability, which is determined based on at least one of the possibility that the difference becomes large, and
Maneuvering instability index obtaining means for obtaining a steering instability index in which the signs are opposite on the drift-out side and the spin side, and the sign of the steering instability index obtained by the steering instability index obtaining means is positive And an index code corresponding correction rule changing means for changing the correction rule between a negative case and a negative case.