KR20080111284A - Active control system control method - Google Patents

Abstract

A control method of active roll control system for the vehicles is provided that the roll angle is more reduced and the ride comfort of the vehicles is improved. A control method of active roll control system for the vehicles comprises following steps: a step for producing the theoretical reference yaw-rate which is input and the car speed and steering angle; a step for saving the yaw rate difference about the reference yaw-rate it is input the measured value of the yaw rate sensor; a step that determines whether the vehicle is understeer or oversteer using the difference of steering angle and yaw rate; a step for operating the hydraulic actuator which is connected to both sides front-wheel in case of being the oversteer state.

Description

Active roll control system control method of vehicle

1 is a graph illustrating the operating characteristics of a conventional active roll control system;

2 is a view for explaining an active roll control system control method for a vehicle according to the present invention.

The present invention relates to a method for controlling an active roll control system of a vehicle. More particularly, the present invention relates to a technique for improving the maneuverability of a vehicle in addition to reducing the rolling of the vehicle by the active roll control system.

In the conventional active roll control system, a controller receiving inputs of a steering angle sensor and a lateral acceleration sensor operates a hydraulic actuator installed between a stabilizer bar and a lower arm, thereby forcibly lifting the vehicle body when a roll of the vehicle is generated to minimize roll movement. It is a device to control.

However, the conventional active roll control device performs only a function of reducing the roll behavior of the vehicle body as described above, and its utilization is relatively large and limited.

The following are the characteristics of the conventional active roll control system which enable the present invention.

1 illustrates the relationship between the vertical force and the lateral force of the tire when the vehicle is turning. The lateral force with respect to the vertical force of the tire when the vehicle is turning has a nonlinear characteristic, and a difference occurs in the vertical force acting on the turning outer ring and the turning inner ring. This indicates that the lateral force changes accordingly.

Line segment P1-P2 describes the relationship between the vertical force and the lateral force applied to the turning outer ring and the turning inner ring when the vehicle turns. When the vertical force acting on the wheel in the straight driving state is W, the vertical force acting on the turning outer ring is W + ΔW, the vertical force acting on the turning inner ring is W-ΔW, and as a result, the load of ΔW to be rotated on the turning inner ring is moved to the turning outer ring, which means that the average of the left and right lateral forces becomes b.

When the active roll control system operates the hydraulic actuator in order to reduce the roll of the vehicle body in the above state, the load transfer phenomenon is further increased, resulting in the same state as the line segments Q1-Q2, and the average of the left and right lateral forces is means c.

From the above-described line segments P1-P2 and line segments Q1-Q2 of FIG. 1, it can be seen that if the active roll control system is actuated during the turning of the vehicle, an intentional change in the magnitude of the vertical force acting on the wheels can be brought about. It can be seen that this results in the load moving further toward the actuator acting.

On the other hand, in the vehicle, there is a tendency of understeer when the load is applied to the front wheel more than the rear wheel, and on the contrary, when the load is applied to the rear wheel, the oversteer tends to occur.

The present invention utilizes the operation characteristics of the conventional active roll control system as described above and the oversteer and understeer characteristics according to the weight distribution state of the front and rear wheels of a general vehicle, so that the conventional active control device has its own function. It is an object of the present invention to provide a method for controlling an active roll control system of a vehicle that can exhibit not only a roll suppression function but also a function of controlling a vehicle attitude.

Active roll control system control method for a vehicle of the present invention for achieving the above object is

Calculating a theoretical reference yaw rate by receiving the vehicle speed and the steering angle;

Obtaining a yaw rate difference with respect to the reference yaw rate by receiving a measurement value of the yaw rate sensor;

Determining whether the vehicle is in an oversteer or understeer state by using a steering angle and the yaw rate difference;

Driving the hydraulic actuators connected to both rear wheels in the understeer state, and driving the hydraulic actuators connected to both front wheels in the oversteer state:

Characterized in that configured to include.

Hereinafter, exemplary embodiments of the present invention will be described with reference to the accompanying drawings.

2 is a diagram illustrating a control method of the present invention, comprising: calculating a theoretical reference yaw rate by receiving a vehicle speed and a steering angle; Obtaining a yaw rate difference with respect to the reference yaw rate by receiving a measurement value of the yaw rate sensor; Determining whether the vehicle is in an oversteer or understeer state by using a steering angle and the yaw rate difference; The determination result includes driving the hydraulic actuators connected to both rear wheels in the understeer state, and driving the hydraulic actuators connected to both front wheels in the oversteer state.

That is, the controller receives each signal from the steering angle sensor, the vehicle speed sensor, the yaw rate sensor, and the lateral acceleration sensor, and can control two hydraulic actuators on the front wheel side and two hydraulic actuators on the rear wheel side of the vehicle body.

Here, the hydraulic actuators, as well as the components constituting the conventional active roll control system, the other sensors and controllers can adopt the conventional configuration as it is, and only the control method according to the present invention can be used by applying the program to the controller. .

The controller calculates a theoretical reference yaw rate by receiving the vehicle speed and the steering angle from the vehicle speed sensor and the steering angle sensor.

In other words, when the vehicle is in a normal turning state, the current yaw rate at the current vehicle speed and steering angle is estimated to take as a reference yaw rate.

Subsequently, the controller receives the measured value of the yaw rate sensor to obtain a yaw rate difference with respect to the reference yaw rate, and in this embodiment, the reference yaw rate is subtracted from the measured value.

The step of determining whether the vehicle is in an oversteer state or an understeer state may include steering angle information if the information indicating the steering angle and the information indicating the yaw rate indicate a positive number when the vehicle is turned right, a negative value when the vehicle is turned left, and a zero value when the vehicle is turned straight. Is positive, and if the yaw rate difference is greater than the first preset value, the oversteer state; and if the yaw rate difference is less than the preset second preset value, determine the understeer state;

If the steering angle information is negative and the yaw rate difference is smaller than the third preset value, the steering wheel information is oversteer. If the yaw rate difference is larger than the fourth preset value, the steering angle information is determined as an understeer state.

At this time, the first set value is a positive number, the absolute value of the third set value is the same and the sign is opposite, the second set value is negative, the fourth set value and the absolute value is the same sign and the opposite.

For example, if the vehicle is in a right turn, the calculated yaw rate is 5, the first set value is 2, and the second set value is -3, the yaw rate is 9 when the measured value measured by the yaw rate sensor is 9; The difference is 9-5 = 4 and 4 is greater than the first set value 2 and is determined to be oversteer;

When the measured value measured by the yaw rate sensor is 1.5, the yaw rate difference is 1.5-5 = -3.5, and -3.5 is determined as understeer since the second set value is smaller than -3.

On the contrary, when the vehicle is in a left turn state, when the calculated reference yaw rate is -5, the third set value is -2, and the fourth set value is 3, the measured value measured by the yaw rate sensor is -9, The yaw rate difference becomes -9-(-5) =-4, and -4 is determined as an oversteer since it is smaller than the third set value -2;

When the measured value measured by the yaw rate sensor is -1.5, the yaw rate difference is -1.5-(-5) = 3.5, and 3.5 is determined as understeer because it is larger than the fourth set value 3.

If it is determined as the oversteer or understeer in the above manner, the hydraulic actuator on the front wheel side or the rear wheel side is controlled as described above to reduce the oversteer or understeer phenomenon.

That is, the determination results in driving the hydraulic actuators connected to both rear wheels in the understeer state and driving the hydraulic actuators connected to both front wheels in the oversteer state.

In the step of driving the hydraulic actuator of the front wheel or the rear wheel, the control amount of the hydraulic actuator is determined in consideration of the yaw rate difference, the rate of change over the time of the yaw rate difference and the lateral acceleration, it is determined by the following equation (1) .

here,

G _Actuator : _Control amount of hydraulic actuator,

: 요레이트 차이,

: Urine rate difference,

: 요레이트 차이의 시간에 대한 변화율,

: Rate of change of time of difference in urine rate,

Ay: lateral acceleration,

K ₁ , K ₂ , K ₃ , K ₄ : Tuning value.

Here, if the oversteer or understeer does not occur during the turning of the vehicle, since the rate of change of the yaw rate difference and the yaw rate difference with respect to time is both zero, the control amount is dependent only on the lateral acceleration.

When the vehicle is in an understeer state, when the two hydraulic actuators of the rear wheels are operated at the control amount as described above, the load is moved to the rear wheel side due to the characteristic that the load is moved toward the hydraulic actuator operating in the active roll control system as described above. This results in the same effect, and it can be seen that when the load on the rear wheel becomes relatively large, the vehicle cancels out the current understeer phenomenon in view of the general characteristic of the vehicle having an oversteer tendency.

On the contrary, when the vehicle is in an oversteer state, if two hydraulic actuators of the front wheel are operated with the control amount calculated by Equation 1 as described above, the load has the same effect as moving to the front wheel side, thereby canceling the current oversteer phenomenon. It is to be made.

In other words, the present invention allows the active roll control system to control the relationship between the front wheel and the rear wheel, as compared with the control of adjusting the relationship between the left and right wheels, thereby oversteering or understeering the vehicle. It is also possible to control the vehicle attitude to reduce the weight.

As described above, according to the present invention, by utilizing the operating characteristics of the conventional active roll control system and the oversteer and understeer characteristics according to the front and rear wheel weight distribution state of the general vehicle, the conventional active control apparatus is its own function. In addition to the roll suppression function of the vehicle body, it is possible to suppress the oversteer and understeer phenomena to control the attitude of the vehicle.

On the other hand, if the control as described above is made, the attitude of the vehicle is stabilized, thereby improving the maneuverability of the vehicle during turning, and further reducing the roll angle, thereby improving the riding comfort of the vehicle.

Claims (3)

Calculating a theoretical reference yaw rate by receiving the vehicle speed and the steering angle; Obtaining a yaw rate difference with respect to the reference yaw rate by receiving a measurement value of the yaw rate sensor; Determining whether the vehicle is in an oversteer or understeer state by using a steering angle and the yaw rate difference; Driving the hydraulic actuators connected to both rear wheels in the understeer state, and driving the hydraulic actuators connected to both front wheels in the oversteer state: Active roll control system control method of a vehicle comprising a. The method according to claim 1, Determining whether the vehicle is in an oversteer or understeer state If the information indicating the steering angle and the information indicating the yaw rate indicate positive when the vehicle is turned right, negative when it is left, and zero when going straight, If the steering angle information is positive and the yaw rate difference is greater than the first preset value, the oversteer state; and if the yaw rate difference is less than the second preset value, the steering angle information is determined as an understeer state; If the steering angle information is negative and the yaw rate difference is smaller than the third preset value, the steering wheel information is oversteer; and if the yaw rate difference is larger than the fourth preset value, the steering angle information is determined as an understeer state; The first set value is a positive number, the absolute value of which is equal to the third set value and the sign is opposite, and the second set value is negative, the absolute value of the fourth set value is the same and the sign is opposite. An active roll control system control method for a vehicle, characterized in that the. The method according to claim 1, In the step of driving the hydraulic actuator of the front wheel or the rear wheel, the control amount of the hydraulic actuator is determined in consideration of the yaw rate difference, the rate of change over the time of the yaw rate difference and the lateral acceleration, the following equation

here, G _Actuator : _Control amount of hydraulic actuator,

: Urine rate difference,

: Rate of change of time of difference in urine rate, Ay: lateral acceleration, K ₁ , K ₂ , K ₃ , K ₄ : Tuning Value The method of controlling the active roll control system of the vehicle, characterized in that determined by.

Images