JP2003175853A - Steering controller - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a steering controller capable of ensuring a favorable feeling of steering by generating an appropriate steering reaction irrespective of the vehicle speed in a steering-by-wire operation. <P>SOLUTION: A steering reaction F, which is a target generating force by a reaction actuator 18, can be calculated by the formula of F=K1×F1+K2×F 2+K3×F3, by using a steering reaction F1 calculated in accordance with a steered angle θ, a steering reaction F2 calculated by the linear sum of the reaction component of a lateral acceleration Yg and the reaction component of a yaw rate ϕ, a steering reaction F3 calculated in accordance with a steering speed dθ, and coefficients K1, K2 and K3. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to steering by a steering-by-wire operation in which a steering input mechanism for inputting an operation to a steering wheel and a steering wheel steering mechanism for steering a steered wheel are mechanically disconnected. It belongs to the technical field of control devices.

[0002]

2. Description of the Related Art Conventionally, as a steering control device using a steering-by-wire operation, for example, Japanese Patent Laid-Open No. 2000-10 is used.
The one described in Japanese Patent No. 8914 is known.

In this prior art publication, the control amount Th for the reaction force imparting means is defined as steering angle θ, steering angular velocity dθ / dt, steering angular acceleration d ² θ / dt ² , detected values of vehicle behavior state (yaw rate, lateral acceleration). , Rack axial force, load current, etc.) are described. Also, the gain K for the steering angle θ
p, the gain Kd for the steering angular velocity dθ / dt, and the gain Kdd for the steering angular acceleration d ² θ / dt ² are constant values,
The gain Ky for the detected value of the vehicle behavior state is set to increase as the vehicle speed V increases.

[0004]

However, the yaw rate has a relatively large value when traveling at a low vehicle speed, but the yaw rate hardly occurs when traveling at a high vehicle speed. On the other hand, the lateral acceleration produces a large value when traveling at a high vehicle speed, but produces only a small value when traveling at a low vehicle speed.

Therefore, the conventional steering control device has the problems listed below. (1) When the yaw rate is used as the detection value of the vehicle behavior state, the resolution of the yaw rate detection value in the high vehicle speed range decreases and the S / N ratio deteriorates. Therefore, increase the gain at high vehicle speed. However, it is difficult to improve the steering feeling due to the noise component. (2) When the lateral acceleration is used as the detection value of the vehicle behavior state, since only a small lateral acceleration occurs in the low vehicle speed range, the resolution of the detection value decreases and the S / N ratio deteriorates. Even if the gain is increased at a low vehicle speed, it is difficult to improve the steering feeling due to the noise component. (3) When the lateral acceleration is used as the detection value of the vehicle behavior state, the lateral acceleration sensor attached to the vehicle is tilted during traveling on a sloped road, so that the lateral acceleration cannot be detected correctly and the steering feeling is reduced. Hard to improve.

The present invention has been made in view of the above problems, and an object of the present invention is to generate a suitable steering reaction force regardless of whether the vehicle speed is high or low at the time of steering-by-wire operation. It is to provide a steering control device that can secure a ring.

[0007]

In order to achieve the above object, in the invention according to claim 1, a steering input mechanism for inputting an operation to a steering wheel and a steering wheel steering mechanism for steering a steered wheel are provided. Is mechanically uncoupled, and a steering control device is provided with steering control means for controlling a reaction force actuator provided in the steering input mechanism and a steering actuator provided in the steered wheel steering mechanism. Steering angle detecting means for detecting the lateral acceleration, lateral acceleration detecting means for detecting the lateral acceleration, yaw rate detecting means or yaw rate estimating means for detecting or estimating the yaw rate, driving operation detecting means for detecting the driving operation of the driver, and steering. The steering reaction force F1 calculated according to the angle, the steering reaction force F2 calculated by the linear sum of the reaction force component due to the lateral acceleration and the reaction force component due to the yaw rate, and A steering reaction force F3 that is calculated in accordance with the rolling operation, using the coefficients K1, K2, K3, the steering reaction force F is a target generating force of the reaction force actuator, F = K
Steering reaction force calculating means for calculating by a formula of 1 × F1 + K2 × F2 + K3 × F3.

Here, the driving operation of the driver means a steering speed, a steering angular speed, and the like.

According to the invention of claim 2, the invention of claim 1
In the steering control device according to, a vehicle speed detecting means is provided,
The larger the deviation between the lateral acceleration estimated value calculating means and the lateral acceleration estimated value calculating the lateral acceleration estimated value using the yaw rate detection or the estimated value and the vehicle speed detected value, the larger the first coefficient K1 becomes. And a second coefficient correcting means for decreasing the second coefficient K2 as the deviation between the lateral acceleration estimated value and the lateral acceleration detected value increases.

Here, as the yaw rate information, the yaw rate estimated value may be calculated using a steering angle detection value, a vehicle speed detection value, and a mathematical model of vehicle motion without using the yaw rate detection means.

In order to suppress the driver's visual discomfort, the larger the deviation between the estimated lateral acceleration value and the detected lateral acceleration value, the larger the third coefficient K3 may be corrected.

[0012]

In the invention according to claim 1, in the steering reaction force calculating means, the steering reaction force F2 due to the vehicle motion state is a linear sum of the reaction force due to the lateral acceleration and the reaction force due to the yaw rate. Is calculated by

Therefore, at a low speed, the yaw rate resolution> the lateral acceleration resolution, so that a reaction force according to the yaw rate can be generated, and at a high speed, the lateral acceleration resolution> the yaw rate resolution, so that a reaction force according to the lateral acceleration can be generated. The ratio of the yaw rate and the lateral acceleration to the force can be changed automatically depending on the vehicle speed, which is preferable to the case where only one of the lateral acceleration and yaw rate is used, or when both are not used. Will occur.

Therefore, it is possible to secure a good steering feeling by generating a suitable steering reaction force regardless of the vehicle speed when steering by wire.

In the invention according to claim 2, the lateral acceleration estimated value calculating means calculates the lateral acceleration estimated value using the relational expression between the yaw rate detection or estimated value and the vehicle speed detected value, and the first coefficient correction In the means, the larger the deviation between the lateral acceleration estimated value and the lateral acceleration detected value, the larger the first coefficient K1 is corrected. In the second coefficient correction means, the lateral acceleration estimated value and the lateral acceleration detected value are combined. The larger the deviation is, the smaller the second coefficient K2 is corrected.

For this reason, the steering reaction force component K2 × F2 calculated by the linear sum of the reaction force component due to the lateral acceleration and the reaction force component due to the yaw rate is corrected so as to be reduced, so that the lateral acceleration detected value during traveling on a sloped road surface. Of the steering reaction force due to the influence of the inclination of the road surface is reduced, while the steering reaction force component K1 × F1 corresponding to the steering angle is corrected to be increased so that the steering reaction force The reduced amount of the component K2 × F2 is compensated for, and thereby the unnaturalness of the steering reaction force is eliminated while suppressing the change in the steering reaction force.

Therefore, it is possible to suppress the uncomfortable feeling of the steering reaction force due to the lateral acceleration detection value being influenced by the inclination of the road surface when traveling on the inclined road surface.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, an embodiment for realizing a steering control device of the present invention will be described as a first embodiment corresponding to the invention according to claims 1 and 2 and a first embodiment corresponding to the invention according to claim 3. A description will be given based on the second embodiment and the third embodiment corresponding to the invention according to claim 4.

(First Embodiment) First, the structure will be described. FIG. 1 is an overall system diagram showing a steering control device according to a first embodiment,
FIG. 2 is a block diagram showing the front wheel steering system of the steering control device of the first embodiment, and FIG. 3 is a block diagram showing the electronic control system of the steering control device of the first embodiment.

In FIG. 1, 1 is a steering wheel, 2 is a steering input mechanism, 3 is a front wheel steering mechanism (steering wheel steering mechanism), 4 and 5 are front wheels, 6 and 7 are rear wheels, and 8 is a steering angle sensor ( Steering angle detecting means), 9 is a second steering angle sensor (steering angle detecting means), 10 is a pinion angle sensor, 11 is a rack stroke sensor, 12 is a steering torque sensor, 13 is a vehicle speed sensor, and 14 is a lateral acceleration sensor ( Lateral acceleration detecting means), 15 is a yaw rate sensor (yaw rate detecting means), 16 is an electronic control unit (steering control means: abbreviated as ECU in the drawing), 17 is a steering actuator, 18 is a reaction force actuator, 19 Is an electromagnetic clutch.

The steering input mechanism 2 is a mechanism for inputting a steering operation of the driver from the steering wheel 1 and generating a steering reaction force according to the steering operation. As shown in FIG. A reaction force actuator 18 is attached to a first column shaft 20 between the electromagnetic clutch 19 and a reduction gear 21. A steering angle sensor 8 for detecting the rotation angle of the steering wheel 1 is mounted between the reaction force actuator 18 and the electromagnetic clutch 19. The reaction force actuator 18 is provided with a second steering angle sensor 9 for detecting the rotation angle of the reaction force actuator 18, that is, the second steering angle via the reduction gear 21. Further, a steering torque sensor 12 that detects a steering force or a steering reaction force is attached between the steering wheel 1 and the reduction gear attachment portion of the reaction force actuator 18.

The front wheel steering mechanism 3 includes left and right front wheels 4, 5
As shown in FIG. 2, the steering rack 22 has tie rods 23, 2 at the left and right ends, respectively.
The knuckle arms 25 and 26 and the front wheels 4 and 5 are connected to each other via 4. Screw 27 on steering rack 22
Is cut, meshes with the pinion gear 28 to form a rack and pinion, and when the pinion shaft 29 rotates, the steering rack 22 moves left and right, and the left and right tie rods 23, 24 are moved. And the tie rods 23, 24
The knuckle arms 25 and 26 move together therewith, and the knuckle rotates about the kingpin to steer the front wheels 4 and 5.

As shown in FIG. 2, the steering actuator 1 is attached to the pinion shaft 29 through a reduction gear 30.
7 is attached to the steering actuator 17
Thus, the pinion shaft 29 can be rotated to steer the left and right front wheels 4, 5. A pinion angle sensor 10 for detecting the shaft rotation angle is attached to the tip of the pinion shaft 29.
A rack stroke sensor 11 that detects the amount of movement of the steering rack 22 is attached to the end of the steering rack 22. Since the steering rack stroke is obtained by converting the rotation angle of the pinion shaft 29 via the rack and pinion, the rack stroke sensor 11 can be referred to as a second pinion angle sensor. In addition, the pinion shaft 29
A second column shaft 31 and a third column shaft 32 are connected to.

As shown in FIG. 2, the electromagnetic clutch 19 includes a first column shaft 20 and a third column shaft 32.
In a state in which the electromagnetic clutch 19 is disengaged and the steering clutch 31 disengages the steering clutch, a steering-by-wire operation for steering the left and right front wheels 4 and 5 is performed. Further, in the state where the electromagnetic clutch 19 is engaged,
The steering wheel 1 and the left and right front wheels 4, 5 function as a normal steering mechanically connected. Then, when the sensor, the actuator and the control device are out of order, the steering function is performed as a normal steering.

As shown in FIG. 1, a vehicle equipped with the present steering control device includes a vehicle speed sensor 13 for detecting a vehicle speed, a lateral acceleration sensor 14 for detecting a lateral acceleration, and a yaw rate sensor 15 for detecting a yaw rate. Installed,
These sensor signals are also input to the electronic control unit 16.

As shown in FIG. 3, the electronic control unit 16 has an input interface 16a having a decoder, an A / D converter and a counter, a CPU 16b as a central processing unit, and an output interface 16c having a relay and a driver. It has and.

The outputs from the steering angle sensor 8, the second steering angle sensor 9 and the pinion angle sensor 10 which are composed of encoders are input to the decoder of the input interface 16a, and the up / down counter responds to the rotation angle. The number of pulses is counted. The output voltages from the rack stroke sensor 11 and the steering torque sensor 12 are
It is converted into a digital numerical value by the A / D converter of the input interface 16a. Further, the pulse signal from the vehicle speed sensor 13 is counted by the counter of the input interface 16a and the pulse cycle is calculated. Output voltages from the lateral acceleration sensor 14 and the yaw rate sensor 15 are converted into digital numerical values by the A / D converter of the input interface 16a. In this way, the output signal from each sensor is processed by the input interface 16a,
It is input to the CPU 16b.

The CPU 16b calculates output command values to the steering actuator 17 and the reaction force actuator 18 based on these processing signals. The calculated output command value is input to the driver (driving circuit) of the output interface 16c, converted into a current value by this driver, and the current is supplied to the steering actuator 17 and the reaction force actuator 18. Works. Further, the CPU 16b determines whether the steering-by-wire operation and the normal steering operation are switched, and the CPU 16b
A command signal is output from 16b. This output signal is converted into a current command value by the driver (driving circuit) of the output interface 16c and supplied to the electromagnetic clutch 19, whereby the electromagnetic clutch 19 operates. Power is supplied to each driver of the steering actuator 17, the reaction force actuator 18, and the electromagnetic clutch 19 via a relay. This relay is turned on / off by the command signal from CPU16b.
To be done.

When the system is out of order, the relay supplying power to the steering actuator 17 and the reaction force actuator 18 is turned off, and the current to both actuators 17 and 18 is cut off. Then, a command value is output to connect the electromagnetic clutch 19 so that the electromagnetic clutch 19 functions as a normal steering wheel.

Here, as a sensor for detecting the steering angle,
A dual system including the steering angle sensor 8 and the second steering angle sensor 9 is configured, and a dual system including the pinion angle sensor 10 and the rack stroke sensor 11 is configured as a sensor that detects a turning angle. The reason is that the failure of the sensor can be reliably determined by comparing the outputs of the two sensors.

Next, the operation will be described.

As described above, the CPU 16b calculates the output command value to the reaction force actuator 18,
The calculation process of the steering reaction force F which is the reference value for obtaining the output command value will be described below.

The steering reaction force F is calculated using the equation F = K1 × F1 + K2 × F2 + K3 × F3 (1) (steering reaction force calculation means). Here, F1 is the first steering reaction force calculated from the steering angle θ,
F2 is the second steering reaction force calculated from the vehicle motion state (yaw rate φ and lateral acceleration Yg), and F3 is the third steering reaction force calculated from the steering operation (steering speed dθ). Further, K1, K2 and K3 are steering reaction forces F1 and F, respectively.
2 and F3.

That is, the first steering reaction force F1 simulates the steering reaction force generated by the deformation of the ground contact surface of the tire due to the steering angle θ when the vehicle is stopped and at extremely low speed. The reaction force for simulating the cornering force generated between and is calculated.

The second steering reaction force F2 generates a steering reaction force corresponding to the yaw rate φ and the lateral acceleration Yg, which are the motion states of the vehicle during traveling, to inform the driver of the vehicle motion state information to the steering information. The reaction force given as is calculated.

The third steering reaction force F3 is controlled by the steering speed dθ to simulate the reaction force of the friction fr of the gear portion and the reaction force of the hysteresis hys of the frictional force generated in the tire and bush. Calculate the reaction force.

Thus, the steering reaction force F is calculated by the above equation (1).
By calculating, the optimum steering reaction force is simulated and generated even during the steering-by-wire operation in which the mechanical connection is broken, and a comfortable driving feeling is realized.

The specific calculation of the steering reaction force F will be described below. First, the steering reaction forces F1, F2, F3 are obtained as follows using the functions shown in FIGS. 4 and 5.

The first steering reaction force F1 is calculated by substituting the detected steering angle θ into the following functional expression (2) for the steering angle θ shown in FIG. F1 = Func_h (θ) (2) That is, as shown in FIG. 4A, the steering angle θ is −θ1 to
In the low steering angle range of + θ1, the first steering reaction force F1 is calculated by the steep change gradient, and in the middle steering angle range of the steering angle θ of + θ1 to + θ2 or −θ1 to −θ2, the first change is made by the gentle change gradient. The steering reaction force F1 is calculated, and in the high steering angle range where the steering angle θ is equal to or greater than + θ2 or equal to or less than −θ2, the first constant value
The steering reaction force F1 of is calculated.

The second steering reaction force F2 is obtained by substituting the detected yaw rate φ into the function Func_yaw (φ) for the yaw rate φ shown in FIG. 4B, and detecting the detected lateral acceleration Yg.
Is the function Func for the lateral acceleration Yg shown in FIG.
Substituting into _yg (Yg), it is calculated by the following formula (3) as the sum of the steering reaction forces obtained from each. F2 = Func_yaw (φ) + Func_yg (Yg) (3) That is, the yaw rate of the second steering reaction force F2 is calculated by a steep change gradient in the low yaw rate range where the yaw rate φ is −φ1 to + φ1. In the yaw rate region where the yaw rate φ is + φ1 or more or −φ1 or less, it is calculated by a gradual change gradient. Further, the lateral acceleration of the second steering reaction force F2 is calculated by a steep change gradient in the low lateral acceleration region where the lateral acceleration Yg is −Yg1 to + Yg1, and the lateral acceleration Yg is greater than + Yg1 or less than −Yg1. In the region, it is calculated by a gradual change gradient.

The third steering reaction force F3 is the friction of the steering speed dθ (driving operation detecting means) calculated by differentiating the steering angle θ with respect to the steering speed dθ shown in FIG. Substitute into the minute function Func_fr (dθ),
Substituting the steering speed dθ into the hysteresis component function Func_hys (dθ) for the steering speed dθ shown in FIG.
The following formula is the sum of the steering reaction forces obtained from each
Calculated according to (4). F2 = Func_fr (dθ) + Func_hys (dθ) (4) That is, although the positive / negative value of the friction of the third steering reaction force F3 differs depending on the steering direction, it is calculated as a constant value regardless of the steering speed dθ. To be done. In addition, the third steering reaction force F
For the hysteresis amount of 3, the steering speed dθ is −dθ1 to + d
In the low steering speed range of θ1, it is calculated by a steep change gradient,
In the steering speed range where the steering speed dθ is equal to or greater than + dθ1 or equal to or less than −dθ1, it is calculated by a gradual change gradient.

By the way, the lateral acceleration Yg and the yaw rate φ are
Using the vehicle speed V, the relationship of Yg = φ × V ... (5) holds. Therefore, ideally, the lateral acceleration Yg
It suffices to detect only one of the two and the yaw rate φ, and the other can be estimated using the equation (5).
However, as can be seen from the influence of the vehicle speed V in the equation (5), the lateral acceleration Yg is calculated from the small output of the yaw rate sensor 15 at high speed, and the S / N ratio of the yaw rate sensor output becomes a problem. come. Therefore, the respective outputs of the lateral acceleration sensor 14 and the yaw rate sensor 15 are used.

Further, by calculating the force (F2) simulating the steering reaction force by the linear sum of the reaction force due to the lateral acceleration Yg and the yaw rate φ, the yaw rate becomes greater than the yaw rate resolution at the low speed> the lateral acceleration resolution. Depending on the vehicle speed, the reaction force corresponding to the lateral acceleration can be generated because the reaction force corresponding to the lateral acceleration can be generated> the resolution of the yaw rate> the resolution of the yaw rate at high speed. It is possible to generate a preferable steering reaction force as compared with the case where only one of the lateral acceleration and the yaw rate is used, or the case where both are not used.

FIG. 6 shows a state in which the vehicle is traveling on an inclined road surface. A vehicle on a road with an inclination angle δ has an attitude of δ
Therefore, the lateral acceleration sensor 14 attached so as to detect the lateral acceleration of the vehicle includes the gravitational acceleration VG × sin (δ). Further, when the centripetal acceleration during turning is LG when the vehicle is turning, the value detected by the lateral acceleration sensor 14 is LG × sin
(Δ). That is, when the vehicle is traveling on an inclined road surface, the output of the lateral acceleration sensor 14 contains a component irrelevant to the motion state of the vehicle. Therefore, if the steering reaction force is generated according to the output of the lateral acceleration sensor 14, the driver feels uncomfortable.

In order to reduce the uncomfortable feeling of the steering reaction force due to the influence of the inclination of the road surface on the output of the lateral acceleration sensor 14 when traveling on a sloped road surface, the first coefficient K1 is set as shown in FIG.
7B, the second coefficient K2 is changed as shown in FIG. That is, the yaw rate φ, the vehicle speed V, the lateral acceleration estimated value Yg ^ (corresponding to the lateral acceleration estimated value calculation means in claim 2) calculated from the above equation (5), and the lateral acceleration sensor output value from the lateral acceleration sensor 14. According to the deviation of Yg, that is, the degree of influence of the inclination of the road surface on the output of the lateral acceleration sensor, the values of K1 and K2 are K1 = K1 ₀ + Func1 (Yg ^ −Yg) (6) K2 = K2 ₀ The above problem is solved by changing -Func2 (Yg ^ -Yg) ... (7). In addition,
The equation (6) corresponds to the first coefficient correcting means, and the equation (7) corresponds to the second coefficient correcting means. Where Function Func1 and Function Func2
Are Func1 (x) = (K1max−K1 ₀ ) / A * x ... (8) Func2 (x) = K2 ₀ / A * x ... (9), respectively. In addition, the maximum coefficient K1max is the following formula that equalizes the increment and decrement of the steering reaction force, Func_yg (A) × K2 ₀ = (K1max−K1) × Func_h (θ) ... (10), and A Is set to a value such as A = 9.8 m / sec ² × sin (30 °) = 4.9 m / sec ² when the maximum road inclination is considered to be 30 degrees.

Therefore, the maximum coefficient K depends on the steering angle θ.
As the value of 1max changes, the coefficients K1 and K2 are changed according to the deviation between the lateral acceleration estimated value Yg ^ and the lateral acceleration sensor output value Yg.
When the value of changes, the change in the steering reaction force is suppressed to be small even if the turning radius is different, and the discomfort can be eliminated.

Next, the effect will be described.

(1) The steering reaction force F1 calculated according to the steering angle θ, the steering reaction force F2 calculated by the linear sum of the reaction force component due to the lateral acceleration Yg and the reaction force component due to the yaw rate φ, and the steering speed. Steering reaction force F3 calculated according to dθ and coefficient K
1, K2, K3, the steering reaction force F, which is the target generated force of the reaction force actuator 18, is F = K1 × F1 + K2 ×
Since it is calculated by the formula of F2 + K3 × F3,
A good steering feeling can be secured by generating a suitable steering reaction force regardless of the vehicle speed during steering by wire operation.

(2) The lateral acceleration estimated value Yg ^ is calculated using the equation of yaw rate φ, vehicle speed V and Yg = φ × V, and the deviation (Yg) between the lateral acceleration estimated value Yg ^ and the lateral acceleration sensor output value Yg is calculated. ^ −Yg) is larger, the first coefficient K1 is corrected to be larger, and the deviation (Y) between the estimated lateral acceleration value Yg ^ and the lateral acceleration sensor output value Yg
The larger the value of g ^ -Yg) is, the smaller the second coefficient K2 is made. Therefore, the feeling of strangeness in the steering reaction force caused by the influence of the inclination of the road surface on the output of the lateral acceleration sensor 14 during traveling on an inclined road surface is reduced. Can be suppressed.

(Second Embodiment) In the second embodiment, as shown in FIG. 8, the yaw rate sensor 15 is omitted from the first embodiment, and the yaw rate φ is calculated by the mathematical model of the steering angle θ, the vehicle speed V and the vehicle motion. Is an example in which is estimated.

First, the structure will be described. The structure of the second embodiment differs from that of the first embodiment in FIG. 8 only in that the yaw rate sensor 15 is omitted. Since FIG. 2 of the first embodiment is the same as that of the second embodiment, illustration and description thereof will be omitted. 9 of the second embodiment, the yaw rate sensor 15 is different from that of FIG. 3 of the first embodiment.
And A / D converter are omitted.

Next, the operation will be described.

The yaw rate φ is φ = {G · ωn ² · Tr (s + 1 / Tr) · θ} / (s ² + 2ζωns + ω ² ) according to the steering angle θ, the vehicle speed V and the mathematical model of the vehicle motion. ... (11) G = {1 / (1 + A ・ V ² )} ・ (V / L) ... (12) Tr = (2Lr ・ Kr) / (m ・ Lf ・ V) ... (13) a = - (m / 2L 2) · {(Lf · Kf-Lr · Kr) / (Kf · Kr)} ... according formula to be (claim 3 obtained using a (14) Equivalent to yaw rate estimation means). However, L: wheel base Lf: distance from the center of gravity to the front axle Lr: distance from the center of gravity to the rear axle Kf: cornering power of the front wheels Kr: cornering power of the rear wheels m: vehicle weight s: Laplace operator

Therefore, from the estimated value of the yaw rate φ obtained by the equation (11) and the vehicle speed V, the lateral acceleration estimated value Yg ^ is obtained by using the equation (5), and the lateral acceleration estimated value Yg ^ and the lateral acceleration estimated. The deviation from the sensor output value Yg is obtained (corresponding to the lateral acceleration estimated value calculating means in claim 3). In accordance with this deviation, the values of the coefficients K1 and K2 are changed as in the first embodiment.

Next, the effect will be described.

In the steering control system of the second embodiment, the yaw rate sensor 15 is omitted from the first embodiment,
Since the yaw rate φ is estimated based on the steering angle θ, the vehicle speed V, and the mathematical model of the vehicle motion, a simple system that does not require a yaw rate sensor is used.
The effects of (1) and (2) can be obtained.

(Third Embodiment) In the third embodiment, in order to reduce the uncomfortable feeling of the steering reaction force due to the influence of the inclination of the road surface on the output of the lateral acceleration sensor 14 during traveling on the inclined road surface, the inclination of the road surface and the lateral In this example, the relationship with the acceleration deviation is measured in advance and the coefficients K1, K2, K3 are determined according to the lateral acceleration deviation.

First, the structure will be described. The structure of the third embodiment is similar to that of the first embodiment shown in FIGS.

Next, the operation will be described.

FIG. 6 shows a state in which the vehicle is traveling on an inclined road surface. A vehicle on a road with an inclination angle δ has an attitude of δ
Therefore, the lateral acceleration sensor 14 attached so as to detect the lateral acceleration of the vehicle includes the gravitational acceleration VG × sin (δ). Further, when the centripetal acceleration during turning is LG when the vehicle is turning, the value detected by the lateral acceleration sensor 14 is LG × sin
(Δ). That is, when the vehicle is traveling on an inclined road surface, the output of the lateral acceleration sensor 14 contains a component irrelevant to the motion state of the vehicle.

The output of the yaw rate sensor of the vehicle has a value different from that when turning on a plane because the detection axis of the yaw rate sensor 15 is inclined. That is, when the detection axis is tilted, the vehicle turns = (rotation around the detection axis + rotation of the detection axis itself), and the rotation amount of the detection axis itself becomes a value deviated from the value representing the turning movement itself of the vehicle.

As described above, when traveling on an inclined road surface, the sensor output values of the lateral acceleration Yg and the yaw rate φ are different from those when moving on a plane, but such values are used as they are. When the steering reaction force is obtained by, for example, as shown in FIG. 10, the steering reaction force increases as the road surface inclination increases from 0 [deg] to the negative direction, and the road surface inclination increases from 0 [deg] to the positive direction. The steering reaction force decreases with increasing direction, and when the road surface inclination exceeds +20 [deg], the steering reaction force is generated in the opposite direction. For example, if the vehicle is making a right turn, the steering reaction force should be originally leftward, that is, the steering reaction force should return to the tall state. Force is generated, which gives the driver a feeling of strangeness.

By the way, on a two-dimensional plane, the lateral acceleration Yg
The yaw rate φ and the vehicle speed V are Y as shown in the above equation (5).
The relationship of g = φ × V holds. Therefore, when the vehicle is traveling on an inclined road surface, the difference (= lateral acceleration deviation) between the lateral acceleration estimated value Yg ^ estimated from the yaw rate sensor output value and the vehicle speed and the lateral acceleration sensor output value Yg is examined. I found out.

Therefore, by correcting the steering reaction force component (K2 × F2) corresponding to the vehicle motion (lateral acceleration Yg and yaw rate φ) according to the lateral acceleration deviation, the steering reaction force becomes unnatural. I thought it could be reduced. On the other hand,
The steering reaction force component (K1 × F1) corresponding to the steering angle θ is increased in accordance with the lateral acceleration deviation to compensate for the decrease in the steering reaction force component corresponding to the vehicle motion. As a result, it is possible to eliminate the unnaturalness of the steering reaction force while suppressing changes in the steering reaction force.

Furthermore, since a sloped road surface having a large degree of inclination is a rare occurrence in a normal running condition,
In addition to the steering reaction force, the driver may feel a sense of discomfort visually. The visual discomfort cannot be eliminated by the steering reaction force, but by increasing the third steering reaction force F3, that is, the steering reaction force component (K3 × F3) corresponding to the steering speed dθ,
Since it is possible to suppress a sudden change in the steering angle θ, it is possible to stabilize the behavior of the vehicle and enhance the driver's sense of security. That is, in F = K1 × F1 + K2 × F2 + K3 × F3 (1), K1: increase according to the lateral acceleration deviation K2: decrease according to the lateral acceleration deviation K3: increase according to the lateral acceleration deviation .

Here, as shown in FIG. 12, the third coefficient K3 is not increased in the small region where the lateral acceleration deviation (Yg ^ -Yg) is B or less because the road surface inclination is small and K3 = K3.
_The constant value is ₀ , and the lateral acceleration deviation (Yg ^ −Yg) is from B to A.
In a relatively large region up to K3, K3 is increased in accordance with the lateral acceleration deviation (Yg ^ −Yg), and the lateral acceleration deviation (Y
In the large error region where g ^ −Yg) is A or more, K3 = K3ma
Let x be a constant value. It should be noted that the value of the lateral acceleration deviation B is a value of the lateral acceleration deviation corresponding to a road surface traveling at a road surface inclination angle (for example, 10 °) which is assumed that many drivers start to feel visually uncomfortable.

Next, the effect will be described.

In the steering control device of the third embodiment, the larger the deviation (Yg ^ -Yg) between the lateral acceleration estimated value Yg ^ and the lateral acceleration sensor output value Yg, the larger the third coefficient K3. The first embodiment and the second embodiment
In addition to the effect of the embodiment, it is possible to suppress a sudden change in the steering angle θ and stabilize the behavior of the vehicle on a sloped road surface having a large degree of inclination, which eliminates the driver's visual discomfort. it can.

(Other Embodiments) The steering control device of the present invention has been described above based on the first to third embodiments, but the specific configuration is not limited to these embodiments. Nonetheless, design changes and additions are allowed without departing from the gist of the invention according to each claim of the claims.

For example, although the encoder is used as the steering angle detecting means in the first embodiment, other means such as a potentiometer may be used.

In the first embodiment, an example in which the steering speed is obtained by time-differentiating the detected steering angle value has been shown. However, the steering speed may be directly obtained using a tacho generator.

Although the steering torque sensor is used as the steering torque detecting means in the first embodiment, the steering torque may be estimated by using the actual current value to the motor of the reaction force actuator.

[Brief description of drawings]

FIG. 1 is an overall system diagram showing a steering control device according to a first embodiment.

FIG. 2 is a configuration diagram showing a front wheel steering system of the steering control device of the first embodiment.

FIG. 3 is a block diagram showing an electronic control system of the steering control device of the first embodiment.

FIG. 4 is a characteristic diagram showing a steering reaction force function formula for a steering angle θ, a steering reaction force function formula for a yaw rate φ, and a steering reaction force function formula for a lateral acceleration Yg, which are used in the first embodiment device.

FIG. 5 is a characteristic diagram showing a steering reaction force function formula for friction and a steering reaction force function formula for hysteresis with respect to a steering speed dθ used in the first embodiment device.

FIG. 6 is a diagram showing an influence of a gravitational acceleration and a centripetal acceleration on a lateral acceleration sensor when a vehicle travels on an inclined road surface.

FIG. 7 is a diagram showing correction characteristics of a first coefficient K1 and a second coefficient K2 with respect to a lateral acceleration deviation in the steering reaction force calculation formula of the first embodiment device.

FIG. 8 is an overall system diagram showing a steering control device of a second embodiment.

FIG. 9 is a block diagram showing an electronic control system of a steering control device according to a second embodiment.

FIG. 10 is a steering reaction force characteristic diagram with respect to a road surface inclination.

FIG. 11 is a lateral acceleration deviation characteristic diagram with respect to a road surface inclination.

FIG. 12 is a diagram showing a correction characteristic of a third coefficient K3 with respect to a lateral acceleration deviation in the steering reaction force calculation formula of the third embodiment device.

[Explanation of symbols]

1 steering wheel 2 Steering input mechanism 3 Front wheel steering mechanism (steering wheel steering mechanism) 4,5 front wheels (steering wheels) 6,7 rear wheels 8 Steering angle sensor (steering angle detection means) 9 Second steering angle sensor (steering angle detecting means) 10 Pinion angle sensor 11 Rack stroke sensor 12 Steering torque sensor 13 Vehicle speed sensor (vehicle speed detection means) 14 Lateral acceleration sensor (lateral acceleration detection means) 15 Yaw rate sensor (yaw rate detection means) 16 Electronic control unit (steering control means) 17 Steering actuator 18 Reaction force actuator 19 Electromagnetic clutch

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) B62D 119: 00 B62D 119: 00 137: 00 137: 00 F term (reference) 3D032 CC05 CC27 CC32 DA03 DA15 DA23 DA29 DA33 DA83 DD02 EB04 EB12 EB16 EB17 EC27 EC29 3D033 CA03 CA13 CA14 CA16 CA17 CA18 CA21

Claims (4)

[Claims] 1. A reaction force actuator provided in the steering input mechanism, wherein a steering input mechanism for inputting an operation to a steering wheel and a steering wheel steering mechanism for steering a steered wheel are mechanically uncoupled. When,
A steering control device including steering control means for controlling a steering actuator provided in the steered wheel steering mechanism, comprising: a steering angle detection means for detecting a steering angle; a lateral acceleration detection means for detecting a lateral acceleration; and a yaw rate. Yaw rate detecting means or yaw rate estimating means for detecting or estimating the driving force, driving operation detecting means for detecting the driving operation of the driver, steering reaction force F1 calculated according to the steering angle, reaction force component due to lateral acceleration, and yaw rate. The target of the reaction force actuator is calculated by using the steering reaction force F2 calculated by the linear sum of the reaction force components by F, the steering reaction force F3 calculated according to the driving operation of the driver, and the coefficients K1, K2, K3. A steering control device comprising: steering reaction force calculation means for calculating a steering reaction force F, which is a generated force, according to the formula F = K1 × F1 + K2 × F2 + K3 × F3. . 2. The steering control device according to claim 1, further comprising vehicle speed detection means, lateral acceleration estimated value calculation means for calculating lateral acceleration estimated value using yaw rate detection or estimated value and vehicle speed detection value, The larger the deviation between the estimated acceleration value and the detected lateral acceleration value, the first coefficient correction means for increasing the first coefficient K1; and the larger the deviation between the estimated lateral acceleration value and the detected lateral acceleration value, the second A steering control device, comprising: a second coefficient correcting means for reducing the coefficient K2; 3. The steering control device according to claim 1, wherein the yaw rate estimating means estimates the yaw rate using a steering angle detection value, a vehicle speed detection value, and a mathematical model of vehicle motion. Steering control device. 4. The steering control device according to claim 1, wherein the larger the deviation between the estimated lateral acceleration value and the detected lateral acceleration value, the larger the third coefficient K3. A steering control device comprising coefficient correction means.