KR102438570B1 - Apparatus for controling vehicle - Google Patents

Abstract

The present invention relates to an apparatus and a method for controlling the steering of a rear wheel of a vehicle. The apparatus includes: a rear wheel angle setting part setting a target value of the rear wheel angle; a displacement commanding part commanding the displacement of the rear wheel angle; a limiting part limiting the displacement of the rear wheel angle to the upper limit; a steering control part controlling the steering of a rear wheel auxiliary shaft with the displacement of the rear wheel angle; a steering driving part driving the steering of the rear wheel auxiliary shaft with the displacement of the rear wheel angle; a steering shaft part steered with the displacement of the rear wheel angle; a rear wheel angle sensing part sensing the displacement of the rear wheel angle; and a rear wheel angle calculation part calculating the upper limit of the rear wheel angle to compare the upper limit to the sensed rear wheel angle. Therefore, the present invention can provide an effect of preventing a sharp curve in which a turning radius becomes smaller, by preventing an excess of the upper limit of a corresponding size value of the rear wheel angle pre-calculated with the front wheel angle and vehicle speed separately from the displacement command value of output.

Description

Steering control device and steering control method of rear wheel of vehicle

The present invention relates to a steering control apparatus and a steering control method for a rear wheel of a vehicle, and more particularly, to a steering control apparatus and a steering control method for a rear wheel of a vehicle for controlling the steering of a rear wheel auxiliary shaft of the vehicle.

In general, trucks that are heavier than passenger cars have much greater scale and damage. In particular, heavy commercial trucks have an increased braking distance of about 40% compared to regular passenger cars, so the rate of involvement in fatal accidents is significantly higher than other vehicles.

Therefore, control methods and devices related to driving stability of commercial trucks as well as general passenger cars are being studied in various ways.

The electric steering device of a commercial vehicle includes a torque sensor that detects torsion of a steering shaft connected to a steering wheel, an electric motor that rotates/moves a steering output shaft or a rack bar in conjunction with a steering output shaft or a rack bar, and a steering torque value measured from the torque sensor. It is configured to include a steering ECU that controls the rotation of the electric motor according to the present invention.

The electric steering device basically rotates the electric motor by generating a steering assist current in proportion to the steering torque according to the driver's manipulation of the steering wheel. That is, a basic operation that assists the driver's steering force is performed.

Meanwhile, a trailer hitch to which a trailer or the like can be mounted is provided at the rear of the vehicle, and other vehicles or trailers may be connected to the hitch.

In such a state in which the hitch trailer is connected, the behavior of the vehicle may become unstable, and in particular, it may affect the electric steering system, making it difficult to properly control the steering.

More specifically, when the hitch trailer is mounted on the vehicle, the load on the rear wheels is increased and the load on the front wheels is reduced by the weight of the trailer, so that the steering feel is changed compared to the case where the trailer is not mounted.

As such, when the hitch trailer is connected, slip occurs or the front wheel load is changed by various additional loads generated in the vehicle.

In particular, due to the change in steering force due to the hitch trailer connection, understeer, in which steering is less than the driver's steering intention, may occur, and furthermore, slip may occur, and compensation for this is required.

In addition, in order to detect an abnormal steering state such as understeer or oversteer or a slip phenomenon resulting therefrom, a complicated method such as comparing the rotational speed of the left and right wheels is used in the existing technology, which is inconvenient.

As such, a commercial vehicle is a vehicle manufactured to transport a large number of people or cargo or perform special-purpose tasks. This is a system for improving the driving and steering safety of the vehicle and improving the steering function by preventing over-steering and braking distance increase that may occur during driving and excessive axle load.

However, the conventional auxiliary shaft steering system operates as a PI control method in which a target value is created at the front wheel angle and vehicle speed, the rear wheel angle displacement command value is compared with the rear wheel angle feedback to the controller, and the error between the command value and the feedback is compensated. There was a problem in that if the feedback is controlled within the error range, it operates normally, and the value of the command value (rear wheel angle) for each speed is not verified.

therefore. Since the conventional auxiliary shaft steering system controls only the error rate with respect to the target value, there is a problem that a sharp curve may occur because the rear wheel angle becomes large when the feedback value, which is the front wheel angle or the vehicle speed, is input.

Republic of Korea Patent Publication No. 10-2017-0082355 (July 14, 2017) Republic of Korea Patent Publication No. 10-2017-0082718 (July 17, 2017) Republic of Korea Patent Registration No. 10-1875490 (August 02, 2018)

The present invention has been devised to solve the conventional problems as described above, and when the rear wheel angle command value exceeds the calculated rear wheel angle value for each speed during the auxiliary shaft steering operation, it is limited to the calculated upper limit of the rear wheel angle for each speed. Provide a steering control device and steering control method for the rear wheel of a vehicle that can prevent a sharp curve in which the turning radius becomes smaller by not exceeding the upper limit of the size of the size of the rear wheel angle calculated in advance at the front wheel angle and vehicle speed separately from the displacement command value to do that for that purpose.

In addition, the present invention reduces the turning radius by controlling the rear wheel steering angle to be in the opposite phase to the front wheel steering angle at low speed, and also improves driving stability by controlling the rear wheel steering angle to be in phase with the front wheel steering angle at high speed. Another object of the present invention is to provide a steering control device and a steering control method for a rear wheel of a vehicle that can be operated.

In addition, the present invention steers the rear wheels according to the front wheel angle and vehicle speed so that the lateral force generation time of the front and rear wheels coincides, and the traveling direction of the vehicle and the driver's gaze direction are matched so that the body slip angle of the vehicle becomes zero. Another object of the present invention is to provide a steering control apparatus and a steering control method for a rear wheel of a vehicle capable of improving the maneuverability of the vehicle at low speed and improving driving stability of the vehicle at high speed.

Another object of the present invention is to provide a steering control apparatus and a steering control method for a rear wheel of a vehicle capable of preventing a sudden curve by limiting a rear wheel angle value according to a front wheel angle and vehicle speed.

The present invention for achieving the above object is a steering control device for a rear wheel of a vehicle for controlling the steering of a rear wheel auxiliary shaft of a vehicle, and a rear wheel angle setting unit ( 10); a displacement command unit 20 installed downstream of the rear wheel angle setting unit 10 to instruct the rear wheel angle displacement; a limiting unit 30 installed downstream of the displacement command unit 20 to limit the displacement of the rear wheel angle to an upper limit; a steering control unit 40 which is installed downstream of the limiting unit 30 and controls the steering of the rear wheel auxiliary shaft by the displacement of the rear wheel angle; a steering driving unit 50 installed downstream of the steering control unit 40 to drive the steering of the rear wheel auxiliary shaft by displacement of the rear wheel angle; a steering shaft part 60 installed downstream of the steering drive part 50 and steered by the displacement of the rear wheel angle; a rear wheel angle sensing unit 70 connected to the steering shaft unit 60 to detect a displacement of the rear wheel angle in the steering shaft unit 60; and a rear wheel angle calculation unit installed downstream of the rear wheel angle sensing unit 70 to calculate the upper limit of the rear wheel angle based on the front wheel angle and vehicle speed and compare it with the rear wheel angle detected by the rear wheel angle sensing unit 70 (80);

The limiting unit 30 of the present invention is characterized in that based on the comparison result of the rear wheel angle calculation unit 80, the displacement of the rear wheel angle is limited to less than or equal to the upper limit of the rear wheel angle.

The rear wheel angle detection unit 70 of the present invention is characterized in that it detects the displacement of the rear wheel angle in real time and feeds it back to the rear wheel angle calculation unit 80 .

The rear wheel angle calculation unit 80 of the present invention, according to the specifications of the vehicle, the following equation

,

,

( L2: distance between the first and second drive axle),

L3: distance between the second drive axle and tag axle,

L4: distance between tag axle and kingpins,

L5: turning radius measured from mid truck,

β1: rear wheel left steering angle (RL Steering angle),

β1+β2: It is characterized in that the upper limit of the rear wheel angle is calculated by the rear wheel right steering angle (RR Steering angle).

In addition, the present invention provides a steering control method of a rear wheel of a vehicle for controlling the steering of a rear wheel auxiliary shaft of the vehicle, the method comprising: setting a target value of a rear wheel angle based on a front wheel angle and a vehicle speed; commanding the displacement of the rear wheel angle based on the set target value of the rear wheel angle; comparing the commanded displacement of the rear wheel angle with an upper limit of the rear wheel angle; limiting the displacement of the rear wheel angle to less than or equal to the upper limit of the rear wheel angle based on the comparison result; controlling and driving the steering of the rear wheel auxiliary shaft with the displacement of the rear wheel angle limited to the upper limit or less; and confirming the completion of steering of the rear wheel auxiliary shaft, and returning to the step of setting the target value of the rear wheel angle when not completed.

As described above, in the present invention, when the rear wheel angle command value exceeds the calculated rear wheel angle value for each speed during the auxiliary shaft steering operation, the present invention limits the calculated rear wheel angle by speed upper limit to the front wheel angle and vehicle separately from the displacement command value of the output. It provides the effect of preventing a sharp curve in which the turning radius becomes smaller by not exceeding the upper limit of the value of the size of the rear wheel angle calculated in advance at the speed.

In addition, at low speed, the turning radius is reduced by controlling the rear wheel steering angle to be in phase opposite to the front wheel steering angle, and at high speed, driving stability can be improved by controlling the rear wheel steering angle to be in phase with the front wheel steering angle. provides an effect.

In addition, the rear wheels are steered according to the front wheel angle and vehicle speed to match the lateral force generation time of the front and rear wheels, and the traveling direction of the vehicle and the driver's gaze direction are matched so that the body slip angle of the vehicle becomes zero. It provides the effect of improving the maneuverability of the vehicle and improving the driving stability of the vehicle at high speed.

In addition, by limiting the angle value of the rear wheel according to the angle of the front wheel and the vehicle speed, it is possible to prevent the occurrence of a sharp curve.

1 is a block diagram illustrating an apparatus for controlling steering of a rear wheel of a vehicle according to an embodiment of the present invention;
FIG. 2 is a graph showing an example of setting a rear wheel angle setting unit of a steering control apparatus for a rear wheel of a vehicle according to an embodiment of the present invention; FIG.
3 is a flowchart illustrating a method for controlling steering of a rear wheel of a vehicle according to an embodiment of the present invention;
4 and 5 are block diagrams illustrating a calculation example of a rear wheel angle calculation unit of a steering control apparatus for a rear wheel of a vehicle according to an embodiment of the present invention;
6 is a flowchart illustrating another example of a method for controlling steering of a rear wheel of a vehicle according to an embodiment of the present invention;
7 is a graph illustrating a calculation example of a rear wheel angle calculation unit of the apparatus for controlling steering of a rear wheel of a vehicle according to an embodiment of the present invention;

Hereinafter, a preferred embodiment of the present invention will be described in more detail with reference to the accompanying drawings.

1 is a block diagram illustrating an apparatus for controlling steering of a rear wheel of a vehicle according to an embodiment of the present invention, and FIG. 2 is a graph showing an example of setting a rear wheel angle setting unit of the apparatus for controlling steering of a rear wheel of a vehicle according to an embodiment of the present invention 3 is a flowchart illustrating a method for controlling steering of a rear wheel of a vehicle according to an embodiment of the present invention, and FIGS. 4 and 5 are calculation of a rear wheel angle calculation unit of the apparatus for controlling steering of a rear wheel of a vehicle according to an embodiment of the present invention. It is a block diagram showing an example, and FIG. 6 is a flowchart showing another example of a method for controlling a steering of a rear wheel of a vehicle according to an embodiment of the present invention, and FIG. 6 is a control apparatus for steering a rear wheel of a vehicle according to an embodiment of the present invention It is a graph showing a calculation example of the rear wheel angle calculation unit.

As shown in FIG. 1 , the steering control device for the rear wheel of a vehicle according to an embodiment of the present invention includes a rear wheel angle setting unit 10 , a displacement command unit 20 , a limiting unit 30 , a steering control unit 40 , and a steering A driving unit 50, a steering shaft unit 60, a rear wheel angle sensing unit 70 and a rear wheel angle calculating unit 80 are included, and it is a steering control device of the rear wheel of the vehicle that controls the steering of the auxiliary rear wheel of the vehicle.

It goes without saying that the apparatus for controlling the steering of the rear wheel of the vehicle according to the present embodiment may be applied to a commercial vehicle such as a truck or a trailer to control the steering of an auxiliary shaft installed on the rear wheel of the commercial vehicle.

The rear wheel angle setting unit 10 is a rear wheel angle setting means for setting a target value of the rear wheel angle based on the front wheel angle and the vehicle speed. The calculated target value of the rear wheel angle is created as a table.

For example, the rear wheel angle setting unit 10 generates the target value of the rear wheel angle according to the front wheel angle and the vehicle speed based on the vehicle specifications in Table 1 below as the graph of FIG. 2 and the table of Table 2 do.

The displacement command unit 20 is installed downstream of the rear wheel angle setting unit 10 and is a displacement command means for instructing the displacement of the rear wheel angle. The target value of the rear wheel angle set in the rear wheel angle setting unit 10 and the rear wheel angle The difference value between the displacement of the rear wheel angle sensed in real time by the sensing unit 70 is commanded as a command value of the displacement of the rear wheel angle.

The limiting unit 30 is installed downstream of the displacement command unit 20 and is a limiting means for limiting the command value of the displacement of the rear wheel angle to the upper limit value. The command value of displacement is limited to less than the upper limit of the rear wheel angle.

The steering control unit 40 is installed downstream of the limiting unit 30 and is a steering control means for controlling the steering of the rear wheel auxiliary shaft with a command value of the displacement of the rear wheel angle. .

The steering drive unit 50 is installed downstream of the steering control unit 40 to drive the steering of the rear wheel auxiliary shaft with the command value of the displacement of the rear wheel angle. It is used to provide steering drive.

The steering shaft part 60 is a steering shaft means installed downstream of the steering drive part 50 and steered by the command value of the displacement of the rear wheel angle, and consists of a rear wheel auxiliary shaft steered by a hydraulic mechanism power mechanism.

The rear wheel angle sensing unit 70 is connected to one side of the steering shaft unit 60 and is a rear wheel angle sensing means for detecting the displacement of the rear wheel angle in the steering shaft unit 60. An angle sensor and the like to detect the displacement of the rear wheel angle in real time. It consists of a variety of sensors.

The rear wheel angle detection unit 70 includes a rear wheel angle displacement sensor that detects the displacement of the rear wheel angle in real time, and feedbacks the displacement of the detected rear wheel angle to the displacement command unit 20 and the rear wheel angle calculation unit 80 in real time. will make it

The rear wheel angle calculation unit 80 is installed downstream of the rear wheel angle detection unit 70, calculates the upper limit of the rear wheel angle based on the front wheel angle and vehicle speed, and the rear wheel angle detection unit 70 detects the displacement of the rear wheel angle. It consists of a rear wheel angle calculation means to compare with .

The rear wheel angle calculation unit 80 is a means for calculating the upper limit of the rear wheel angle based on the front wheel angle and the vehicle speed according to the specifications of the vehicle, and the vehicle speed and the front wheel steering angle using Ackermann steering geometry The upper limit of the steering angle of the auxiliary shaft according to the figure is calculated and controlled.

As such, in order to derive the rear wheel steering angle according to the front wheel steering angle for the optimal turning radius of the vehicle, it is preferable to apply the trigonometric function principle to the kinematic characteristics of Ackermann steering.

First, the variables for calculating the rear wheel steering angle are as follows.

Applicable vehicle: 10x4 Tag truck

Vehicle specification variables: L1, L2, L3, L4

Vehicle speed gain function: a. b

Input value: α1+α2 (front steering angle FR), vehicle speed Vx

Output value: β1+β2 (rear right steering angle RR Steering angle), β1 (rear left steering angle RL steering angle), L5.

In addition, if the term of the variable is specifically defined,

L1 : Wheel base,

L2: distance between the first and second drive axle,

L3: distance between the second drive axle and tag axle,

L4: distance between tag axle and kingpins,

L5: turning radius measured from mid truck,

α1+α2: steering angle to the front-wheel driver, Vx: vehicle speed,

β1+β2 : rear right steering angle (RR Steering angle),

β1 : Rear wheel left steering angle (RL Steering angle).

As shown in FIG. 4, when the rear wheel steering angle according to the front wheel steering angle is derived using the Ackermann steering geometry, the following formula 1 is applied when the trigonometric function is applied to the Ackermann geometry to derive L5 is calculated as

[Formula 1]

[Formula 2]

In the same manner as above, β1+β2 and β1 are calculated as in Equations 3 and 4.

[Formula 3]

[Formula 4]

Assuming that the value of the rear wheel steering angle decreases according to the speed according to a specific function, it can be calculated by Equation 4 When defined (a=0, b=1/40), the rear wheel steering angle RR according to the speed is defined as follows.

1) In case the steering wheel turns left (Calculation 1 is applied when deriving L5)

① If Vx ≤ 30km/h,

[Formula 5]

to be.

② If 30km/h<Vx ≤ 40km/h,

[Formula 6]

to be.

③ If 40km/h<Vx,

is 0.

2) When steering wheel turns right (Calculation 2 is applied when deriving L5)

However, depending on the steering wheel steering, β1+β2 -> β1 changes, and α1+α2 -> α1 changes.

① If Vx ≤ 30km/h,

[Formula 7]

to be.

② If 30km/h<Vx ≤ 40km/h,

[Formula 8]

to be.

③ If 40km/h<Vx,

0.

Hereinafter, an example of the method for controlling the steering of the rear wheel of the vehicle according to the present embodiment will be described in more detail with reference to the accompanying drawings.

1 to 3, the steering control method of the rear wheel of the vehicle of this embodiment includes a setting step (S10), a command step (S20), a comparison step (S30), a limiting step (S40), and a control and driving step ( S50) and a completion confirmation step (S60), it is a steering control method of the rear wheel of the vehicle for controlling the steering of the auxiliary axle of the rear wheel of the vehicle.

Of course, the method for controlling the steering of the rear wheel of the vehicle according to the present embodiment may be applied to a commercial vehicle such as a truck or a trailer to control the steering of an auxiliary shaft installed on the rear wheel of the commercial vehicle.

The setting step (S10) is a step of setting a target value of the rear wheel angle based on the front wheel angle and the vehicle speed. The target values are created as a table.

The command step (S20) is a step of commanding the displacement of the rear wheel angle based on the set target value of the rear wheel angle. The target value of the rear wheel angle set in the setting step (S10) and the rear wheel angle sensor 70 in real time The difference value between the detected and fed back rear wheel angle displacement is commanded as the rear wheel angle displacement command value.

The comparison step (S30) is a step of comparing the commanded rear wheel angle displacement command value with the upper limit value of the rear wheel angle for each speed. The upper limit of the calculated rear wheel angle is compared accordingly.

In this comparison step (S30), when the command value is greater than the upper limit, the limiting step (S40) is moved, and when the command value is not greater than the upper limit, the control and driving step (S50) is moved.

The limiting step (S40) is a step of limiting the command value of the displacement of the rear wheel angle to less than or equal to the upper limit of the rear wheel angle based on the comparison result.

The control and driving step (S50) is a step of controlling and driving the steering of the rear wheel auxiliary shaft with the command value of the displacement of the rear wheel angle limited to the upper limit or less. will do

The completion confirmation step (S60) is a step of confirming the completion of the steering of the rear wheel auxiliary shaft. When the rear wheel auxiliary shaft steering is not completed, the setting step (S10) of setting the target value of the rear wheel angle is returned to the setting step (S10), command The step S20, the comparison step S30, the limiting step S40, and the control and driving step S50 are carried out, and when the steering of the rear wheel auxiliary shaft is completed, the control of the rear wheel auxiliary shaft steering is ended.

Hereinafter, another example of the method for controlling the steering of the rear wheel of the vehicle according to the present embodiment will be described in more detail with reference to the accompanying drawings.

As shown in FIGS. 3 and 6 to 7 , the steering control method of the rear wheel of the vehicle of the present embodiment includes an arrangement step (S110), a setting step (S120), a command step (S130), a comparison step (S140), and a limiting step (S150), a control and driving step (S160), and a completion confirmation step (S170), is a steering control method of the rear wheel of the vehicle to control the steering of the auxiliary axle of the rear wheel of the vehicle.

Of course, the method for controlling the steering of the rear wheel of the vehicle according to the present embodiment may be applied to a commercial vehicle such as a truck or a trailer to control the steering of an auxiliary shaft installed on the rear wheel of the commercial vehicle.

The arranging step (S110) is a step of arranging the rear wheel angle value and the stored array a[n] value at the vehicle speed (0<Vx≤40km/h) when the front wheel angle is 5 degrees, and the rear wheel angle value and the stored array a [n] values are arranged as shown in Table 3.

The setting step (S120) is a step of setting a target value of the rear wheel angle based on the front wheel angle and the vehicle speed. The target values are created as a table.

The command step (S130) is a step of commanding the displacement of the rear wheel angle based on the set target value of the rear wheel angle. The target value of the rear wheel angle set in the setting step (S120) and the rear wheel angle sensor 70 in real time The difference value between the detected and fed back rear wheel angle displacement is commanded as the rear wheel angle displacement command value.

The comparison step (S140) is a step of comparing the commanded rear wheel angle displacement command value with the upper limit value of the rear wheel angle for each speed. The upper limit of the calculated rear wheel angle is compared accordingly.

In this comparison step (S140), when the command value is greater than the upper limit, the limit step (S150) is moved, and when the command value is not greater than the upper limit value, the control and driving step (S160) is moved.

The limiting step S150 is a step of limiting the command value of the displacement of the rear wheel angle to less than or equal to the upper limit of the rear wheel angle based on the comparison result.

The control and driving step (S160) is a step of controlling and driving the steering of the rear wheel auxiliary shaft with the command value of the displacement of the rear wheel angle limited to the upper limit or less. will do

The completion confirmation step (S170) is a step of confirming the completion of steering of the rear wheel auxiliary shaft. When the rear wheel auxiliary shaft steering is not completed, the setting step (S120) of setting the target value of the rear wheel angle is returned to the setting step (S120), command The step S130, the comparison step S140, the limiting step S150, and the control and driving step S160 are performed, and when the steering of the rear wheel auxiliary shaft is completed, the control of the rear auxiliary shaft steering is ended.

Specifically, in another example of the method for controlling the steering of the rear wheels of the vehicle according to this embodiment, L5 is calculated by Equation 1 because one front wheel steering angle sensor is installed in the driver's seat, and the turning radius of the truck is determined by the front wheel steering angle (α1+α2). L5 is determined, and the larger the steering angle, the smaller the turning radius L5 value.

[Formula 1]

In the case of left and right turns, the front wheel steering angle of the driver's seat is one, so the left and right rear wheel steering angle values are the same. Therefore, by Equation 4, the rear wheel steering angle is equally applied to the left and right rear wheel steering angles.

[Formula 4]

The front wheel angle is 5 degrees, and the rear wheel angle when Vx ≤ 30 km/h is 1.34 degrees in Table 2. Table 4 shows the ratio of the rear wheel angle according to the increase in the front wheel angle.

Since the front wheel angle ∝ the rear wheel angle, the upper limit of the rear wheel angle is calculated when the front wheel angle is input in a proportional relationship. In Table 2, the proportional relationship between the front wheel angle and the rear wheel angle at a vehicle speed between 0 < Vx ≤ 40 km/h is shown in FIG. 7 .

For the operation of the auxiliary shaft steering system, when the front wheel angle is 5 degrees at the initial stage, calculate the rear wheel angle value for each speed in Table 3 first. During real-time operation of the auxiliary shaft steering system, the upper limit of rear wheel angle displacement is set at 5-degree intervals of front wheel angle. If the upper limit is exceeded, the rear wheel angle command value is input as the upper limit value.

When the front wheel angle is 5 degrees, prepare a table array a[n] of the reference value for each vehicle speed, set the front wheel angle multiplier γ and the margin ratio as the front wheel angle value during the auxiliary shaft steering operation, and determine the array a[n] according to the speed to determine the rear wheel Each upper limit is calculated.

By applying the calculated upper limit value in real time, the rear wheel angle is limited according to the vehicle speed and the front wheel angle so that oversteer (rapid acceleration) does not occur. Table 3 is a table showing the rear wheel angle values and the stored array a[n] values at the vehicle speed (0<Vx≤40km/h) when the front wheel angle is 5 degrees.

The increase rate in Table 3 is defined as %, and it is defined as the margin ratio [%] for calculating the upper limit of the rear wheel angle according to the front wheel angle. When the front wheel angle increases by 5 degrees, the upper limit of the rear wheel angle is rounded up to the first decimal place when the remainder occurs at the front wheel angle multiplier γ = ROUNDUP(front wheel angle/5,0).

Reference value array a[n] = Rear wheel angle value at 5º front wheel angle according to vehicle speed Vx.

For example, if Vx =37km/h then array a[7] = 0.40.

Front wheel angle of 30 degrees or less: Upper limit of rear wheel angle β_limit = γ* a[n] * 1.1 (margin ratio)

Front wheel angle of 40 degrees or less: Upper limit of rear wheel angle β_limit = γ* a[n] * 1.2 (margin ratio)

Front wheel angle of 45 degrees or less: Upper limit of rear wheel angle β_limit = γ* a[n] * 1.25 (tolerance factor)

[Calculation Example 1]

When the front wheel angle is 27 degrees and the speed is 35 km/h

Rear wheel angle multiplier γ = ROUNDUP(27/5,0) = 6, if 35km/h n=5 a[n]=0.67,

The upper limit of the rear wheel angle β_limit =6*0.67*1.1=4.42.

If the value calculated in Equation 4 is 3.88, the calculated result is applied, and if β_limit is exceeded, the rear wheel angle command value is limited to β_limit.

[Calculation Example 2]

When the front wheel angle is 35 degrees and the speed is 10 km/h

Rear wheel angle multiplier γ = ROUNDUP(35/5,0) = 7 If 10km/h, n=0 a[n]=1.34,

The upper limit of the rear wheel angle β_limit =7 *1.34 *1.2 = 11.26.

If the value calculated in Equation 4 is 10.61 (Table 2), the calculated result is applied. If β_limit is exceeded, the rear wheel angle command value is limited to β_limit.

As described above, according to the present invention, when the rear wheel angle command value exceeds the calculated rear wheel angle value for each speed during the auxiliary shaft steering operation, the rear wheel angle is limited to the calculated upper limit of the rear wheel angle for each speed. It provides the effect of preventing a sharp curve in which the turning radius becomes smaller by not exceeding the upper limit of the value of the size of the rear wheel angle calculated in advance at the speed.

In addition, at low speed, the turning radius is reduced by controlling the rear wheel steering angle to be in phase opposite to the front wheel steering angle, and at high speed, driving stability can be improved by controlling the rear wheel steering angle to be in phase with the front wheel steering angle. provides an effect.

In addition, the rear wheels are steered according to the front wheel angle and vehicle speed to match the lateral force generation time of the front and rear wheels, and the traveling direction of the vehicle and the driver's gaze direction are matched so that the body slip angle of the vehicle becomes zero. It provides the effect of improving the maneuverability of the vehicle and improving the driving stability of the vehicle at high speed.

In addition, by limiting the angle value of the rear wheel according to the angle of the front wheel and the vehicle speed, it is possible to prevent the occurrence of a sharp curve.

The present invention described above can be embodied in various other forms without departing from the technical spirit or main characteristics thereof. Accordingly, the above embodiments are merely examples in all respects and should not be construed as limiting.

10: rear wheel angle setting unit 20: displacement command unit
30: limiting unit 40: steering control unit
50: steering drive part 60: steering shaft part
70: rear wheel angle detection unit 80: rear wheel angle calculation unit

Claims (5)

A steering control device for a rear wheel of a vehicle for controlling the steering of a rear wheel auxiliary shaft of the vehicle,
a rear wheel angle setting unit 10 for setting a target value of the rear wheel angle based on the front wheel angle and the vehicle speed;
a displacement command unit 20 installed downstream of the rear wheel angle setting unit 10 to instruct the rear wheel angle displacement;
a limiting unit 30 installed downstream of the displacement command unit 20 to limit the displacement of the rear wheel angle to an upper limit;
a steering control unit 40 which is installed downstream of the limiting unit 30 and controls the steering of the rear wheel auxiliary shaft by the displacement of the rear wheel angle;
a steering driving unit 50 installed downstream of the steering control unit 40 to drive the steering of the rear wheel auxiliary shaft by displacement of the rear wheel angle;
a steering shaft part 60 installed downstream of the steering drive part 50 and steered by the displacement of the rear wheel angle;
a rear wheel angle sensing unit 70 connected to the steering shaft unit 60 to detect a displacement of the rear wheel angle in the steering shaft unit 60; and
A rear wheel angle calculation unit installed downstream of the rear wheel angle sensing unit 70, calculating the upper limit of the rear wheel angle based on the front wheel angle and the vehicle speed, and comparing it with the rear wheel angle detected by the rear wheel angle sensing unit 70 ( 80); including;
The rear wheel angle calculation unit 80, according to the specifications of the vehicle, the following equation

,

( L2: distance between the first and second drive axle),
L3: distance between the second drive axle and tag axle,
L4: distance between tag axle kingpins,
L5: turning radius measured from mid truck,
β1: rear wheel left steering angle (RL Steering angle),
β1+β2: by the right rear wheel steering angle (RR Steering angle),
A steering control device for a rear wheel of a vehicle, characterized in that calculating an upper limit value of the rear wheel angle. The method of claim 1,
The limiting unit 30 limits the displacement of the rear wheel angle to below the upper limit of the rear wheel angle based on the comparison result of the rear wheel angle calculation unit 80. The method of claim 1,
The rear wheel angle sensing unit (70) detects the displacement of the rear wheel angle in real time and feeds it back to the displacement command unit (20) and the rear wheel angle calculation unit (80). delete A method for controlling the steering of a rear wheel of a vehicle for controlling the steering of an auxiliary shaft of a rear wheel of a vehicle using the steering control device for the rear wheel of the vehicle according to claim 1,
setting a target value of the rear wheel angle based on the front wheel angle and the vehicle speed;
commanding the displacement of the rear wheel angle based on the set target value of the rear wheel angle;
comparing the commanded displacement of the rear wheel angle with an upper limit of the rear wheel angle;
limiting the displacement of the rear wheel angle to less than or equal to the upper limit of the rear wheel angle based on the comparison result;
controlling and driving the steering of the rear wheel auxiliary shaft with the displacement of the rear wheel angle limited to the upper limit or less; and
and confirming the completion of steering of the rear wheel auxiliary shaft, and returning to the step of setting a target value of the rear wheel angle if not completed.

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