KR102056111B1 - Control Method for Four Wheel Drive - Google Patents

Abstract

The present invention is provided to solve the above problems of the prior art. The object of the present invention is to prevent the occurrence of a wheel slip as quickly as possible depending on the driving condition of a vehicle, to block other side effects even if the wheel slip occurs to some extent, to compensate for the disadvantages of each control method by changing a slip control method according to the driving condition, and to maximize the performance of a four-wheel drive vehicle.

Description

Control method for four wheel drive vehicle {Control Method for Four Wheel Drive}

The present invention relates to a control method of a four-wheel drive vehicle, and more particularly, to a method of supplementing the disadvantages of each control method by selecting a control method according to the driving state of the four-wheel drive vehicle.

In general, the control of the four-wheel drive system achieves optimal front and rear wheel driving force distribution to ensure normal starting and acceleration and climbing performance when the vehicle starts or accelerates on slippery roads, especially when the speed difference between the front and rear wheels occurs during climbing. Slip control to lose, and handling control to achieve the optimum front and rear wheel drive force distribution to suppress the understeer or oversteer when turning the vehicle and to ensure normal turning performance.

As known in the art, a control method for securing driving stability in a vehicle is largely configured to match the dynamic characteristics of each system to a target performance based on the driving, braking, steering, and suspension systems of the vehicle. In addition, these control methods are independently implemented, and priorities in terms of stability are assigned according to driving conditions and driving conditions of the vehicle, and the corresponding control methods are sequentially entered according to the assigned priorities. In addition, the four-wheel drive slip control and the handling control are operated according to a similar cooperative control strategy. In general, the handling control enters and operates in advance of the slip control.

However, this single control on / off method has a limitation in securing stability in a complex driving situation such as slip oscillation in a circuit, and in case of a transition between frequent control modes, This may cause a problem in response performance.

To this end, a method of simultaneously obtaining slip control and handling control effects on rear wheels during four-wheel drive driving has been proposed. In the related art, a specific method for slip control has not been proposed. There is no suggestion to solve the problem.

In addition, no control scheme is proposed for the traction control for preventing the static frictional force loss of the vehicle wheels.

The present invention is to solve the above-mentioned problems of the prior art, the purpose of which is to prevent the occurrence of wheel slip as quickly as possible according to the driving state of the vehicle, and to prevent some side effects even if the wheel slip occurs to some extent, driving state The purpose is to supplement the disadvantages of each control method by maximizing the slip control method and to maximize the performance of the four-wheel drive vehicle.

The four-wheel drive vehicle control method according to the present invention for achieving the above object, in the four-wheel drive vehicle control method consisting of the four-wheel drive vehicle control system and the vehicle CAN communication, the wheel slip amount calculation and wheel from the information collected from the vehicle during four-wheel drive driving Wheel slip amount calculating unit for determining the slip state, driving state determination unit for determining the driving state according to the reference values for the driver input signal and the vehicle sensor signal during four-wheel drive driving, determination of the driving state determination unit and the wheel slip amount during four-wheel drive driving And a wheel slip control unit for controlling the four-wheel drive vehicle according to the calculated value of the calculation unit.

In addition, the wheel slip amount calculation step of collecting the information of the drive wheel drive unit information from the wheel slip amount calculation unit, the wheel slip amount calculation step of calculating the wheel slip amount from the information obtained in the drive wheel unit information collection step, the wheel slip amount is normal The final wheel slip amount for calculating the final wheel slip amount through the calculation value of the wheel slip amount calculation step (S40), the wheel slip amount step and the wheel slip amount calculation step when the wheel is calculated by the formula according to the steering angle when turning. It is characterized by determining whether the slip control intervention in the calculation step.

The driving state determining unit may include a control situation determination step of determining whether the driving state is the traction control state or the handling control state according to the reference values of the driver input signal and the vehicle sensor signal.

The control reference slip amount setting step of setting a control reference slip amount based on the calculated value of the final wheel slip amount calculation step according to the control situation determination step in the wheel slip control unit, and the wheel slip in the traction control situation. An integral control step of performing integral control according to the amount, and in the case of the handling control situation, characterized in that the PID control step of performing a proportional control, integral control, derivative control according to the wheel slip amount.

According to the present invention, according to the driving situation of the vehicle, through the integral control in the traction control situation, it is possible to minimize problems such as noise or vibration when the wheel slip occurs, to prevent slip, proportional control, integral control, derivative in the handling situation Through control, it is possible to improve response in case of instant slip and prevent torque ripple.

1 is a flow chart of a front wheel rear wheel torque distribution control method of a four-wheel drive vehicle according to the prior art.
2 is a flowchart of a driving state determination unit of a four-wheel drive vehicle control method according to an embodiment of the present invention.
3 is a flow chart of a four-wheel drive vehicle control method according to an embodiment of the present invention.

Hereinafter, with reference to Figures 2 and 3 attached to the specific content for practicing the present invention will be described in detail.

The four-wheel drive vehicle control method according to the present invention, in a four-wheel drive vehicle control method comprising a four-wheel drive vehicle control system and the vehicle CAN communication, the wheel to calculate the wheel slip amount and the wheel slip state from the information collected from the vehicle during four-wheel drive driving The slip amount calculation unit 200, the driving state determination unit 100 for determining the driving state according to the reference value for the driver input signal and the vehicle sensor signal during the four-wheel drive driving, and the determination of the driving state determination unit 100 during the four-wheel drive driving and It includes a wheel slip control unit 300 for controlling the four-wheel drive vehicle in accordance with the calculated value of the wheel slip amount calculation unit 200.

Also, the wheel slip amount information collecting step (S20) for collecting the information of the housewife driving wheel part in the wheel slip amount calculating unit 200, the wheel slip amount for calculating the wheel slip amount with the information obtained in the driving wheel information collecting step (S20). Calculation step (S30), the wheel slip amount calculation step (S40), the wheel slip amount step and the wheel slip amount calculation step (S40) of the turning to calculate the wheel slip amount by the formula according to the steering angle during normal turning The final wheel slip amount calculation step (S50) of calculating the final wheel slip amount through the calculated value is characterized in that it is determined whether the slip control intervention.

In addition, the driving state determination unit 100 is characterized in that it comprises a control situation determination step (S10) for determining whether the traction control situation or the handling control situation according to the reference value for the driver input signal and the vehicle sensor signal.

In addition, the control step slip amount setting step (S60) of setting the control reference slip amount based on the calculated value of the final wheel slip amount calculation step according to the control situation determination step (S10) in the wheel slip control unit 300, Integral control step of performing integral control according to the wheel slip amount in the case of the traction control situation, PID control step (S80) of performing proportional control, integral control and derivative control according to the wheel slip amount in the handling control situation. Characterized in that made.

More specifically, in the traction control situation, which is a step for determining driving conditions, if wheel slip of the front and rear wheels is applied by applying proportional control in a general driving situation, torque to prevent wheel slip is applied accordingly. do. At this time, as the torque is applied, the wheel slip will also be reduced.

However, if the road surface of the front and rear wheels is in a situation of escaping or driving other complex roads, the wheel slips again when the torque is released again because the wheel slip is prevented at the moment, and the torque is applied again. The torque ripple phenomenon disappears again, causing noise or vibration to occur in the vehicle, and the performance of the four-wheel drive will deteriorate. Accordingly, in the traction control situation, it is appropriate to apply torque after the wheel slip is generated and to apply the integral control capable of maintaining the torque to some extent even if the wheel slip is reduced.

On the other hand, in the case of the handling control situation, the wheel slip of the front wheel and the rear wheel can be grasped rapidly according to the development direction of the vehicle to maintain a stable turning state, and it is possible to operate with a sense of operation while allowing wheel slip of the front and rear wheels in the turning state. Can also be set to enable. Accordingly, the PID control (hereinafter referred to as proportional control, integral control, and derivative control) compensates for the disadvantages of integral control and proportional control in handling control situations, and wheelslip in handling control situations according to the intervention weight of wheel slip control depending on the driving mode. The torque control intervention amount will be determined when it occurs.

In the wheel slip amount calculating unit 200, the wheel slip amount is a value obtained by subtracting the slip amount generated during normal turning again from the value obtained by subtracting the average wheel speed of the rear wheel from the average wheel speed of the front wheel. In addition, the slip amount generated during the normal turning is calculated by the formula according to the steering angle, and the reference value is set by the previously calculated wheel slip amount to determine whether slip control is involved.

On the other hand, the driving state determination unit 100 receives the information on the steering angle through the driver's input signal, and receives information such as lateral acceleration, yaw rate sensor, vehicle speed through the vehicle sensor signal. By using the four signals described above, a specific reference value is set, and a control situation determination is performed to determine whether the driving state of the vehicle is a traction control situation or a handling control situation according to the reference value.

The wheel slip amount calculating unit 200 and the driving state determining unit 100 set the wheel slip control reference slip amount according to the driving state, and perform integral control or PID control according to the slip amount. In this case, the equation applied when integral control is as follows.

는 슬립량,

는 적분제어 게인(gain), λ는 망각인자(forgetting factor)를 의미한다.Where u is the torque,

Is the slip amount,

Is an integral control gain, and λ is a forgetting factor.

In addition, the integral control gain and the forgetting factor may be set to a map-type calibration value according to the wheel slip amount, so that the control value may be different according to the vehicle. In the case of gain here, in other words, it means a gain value.

On the other hand, in the handling control situation, as described above, the PID control, that is, the proportional control, the integral control, and the derivative control compensate for the disadvantages of other control methods.In the case of the proportional control, the proportional control gain variable is set according to the wheel slip amount, and the integral is integrated. In the case of control, the above-described traction control method is controlled.In the case of derivative control, the value obtained by subtracting the previous wheel slip amount from the current wheel slip amount by time is obtained by a formula of a value multiplied by the differential control gain, and handling control torque In the case of, it can be obtained by the sum of each torque amount calculated through PID control.

Through the present invention described above, according to the driving situation of the vehicle, through the integral control of the integral control step (S70) in the traction control situation, it is possible to minimize problems such as noise or vibration when the wheel slip occurs, to prevent slip, handling In the situation, the PID control step (S80) may increase the responsiveness during instantaneous slip and prevent the torque ripple phenomenon as described above.

Although the present invention has been described with reference to the embodiments illustrated in the drawings, those skilled in the art will understand that various modifications and equivalent other embodiments are possible therefrom. Therefore, the technical protection scope of the present invention will be defined by the claims below.

100: driving state determination unit S40: wheel slip amount calculation when turning
200: wheel slip amount calculation unit S50: final wheel slip amount calculation
300: wheel slip amount control unit S60: control reference slip amount setting
S10: Control situation judgment S70: Integral control
S20: Drive wheel unit information collection S80: PID control
S30: Wheel slip amount calculation S90: Torque calculation

Claims (4)

In the four-wheel drive vehicle control method comprising the four-wheel drive vehicle control system and the vehicle CAN communication,
Wheel slip amount calculation unit for calculating the wheel slip amount and the wheel slip state from the information collected from the vehicle during four-wheel drive driving,
A driving state determination unit determining a driving state according to a reference value for a driver input signal and a vehicle sensor signal during four-wheel driving;
Including a wheel slip control unit for controlling a four-wheel drive vehicle in accordance with the determination of the driving state determination unit and the calculation value of the wheel slip amount calculator during four-wheel drive driving,
A driving wheel information collecting step of collecting information of a housewife driving wheel part by the wheel slip amount calculating unit, a wheel slip amount calculating step of calculating a wheel slip amount using the information obtained from the driving wheel information collecting step, and when the wheel slip amount is normally turned Slip to the final wheel slip amount calculation step of calculating the final wheel slip amount through the calculation value of the wheel slip amount calculation step, the wheel slip amount calculation step and the wheel slip amount calculation step when the swing is calculated by the formula according to the steering angle. Judging control intervention,
And a control situation determination step of determining, by the driving state determination unit, whether a traction control situation or a handling control situation is based on reference values for the driver input signal and the vehicle sensor signal.
Setting a control reference slip amount based on the calculated value of the final wheel slip amount calculation step according to the control situation determination step in the wheel slip control unit; and performing the integral control according to the wheel slip amount in the traction control situation Integrating control step, the four-wheel drive vehicle control method comprising a PID control step of performing a proportional control, integral control, derivative control according to the wheel slip amount in the handling control situation.
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