KR101103531B1 - Method to control stability of vehicle - Google Patents

Abstract

The present invention relates to a vehicle stability control method, and to obtain a parameter for determining an oversteer and understeer situation of a vehicle using a measured value of a vehicle stability control device. The aim is to increase the reliability of control performance through the obtained parameters.

To this end, the present invention, in the method for controlling the vehicle stability using the steering angle, wheel speed and yaw rate sensor for detecting the movement information of the vehicle, the steering angle size, vehicle longitudinal speed from the steering angle, wheel speed and yaw rate sensor And reading the measured value of yaw velocity; And determining a situation of the vehicle based on sensor readings of the steering angle size, the vehicle longitudinal speed, and the yaw speed.

Description

Method to control stability of vehicle

1 is a conceptual diagram illustrating an oversteer situation when a vehicle is traveling in a circle;

2 is a conceptual diagram illustrating an understeer situation when the vehicle is traveling in a circle;

3 is a conceptual diagram illustrating a situation in which the oversteer and understeer behaviors appear in a complex manner when the vehicle is turning;

4 is a block diagram of a vehicle stability control apparatus according to the present invention;

5 is an operation flowchart of a vehicle stability control method according to the present invention.

Explanation of symbols on the main parts of the drawings

10: steering angle sensor 20: wheel speed sensor

30: yaw rate sensor 40: ESP controller

41: axis distance information storage unit 42: oversteer / understeer determination unit

43: oversteer / understeer control unit 50: brake control unit

60 engine control unit

The present invention relates to a vehicle stability control method, and more particularly, to a vehicle stability control method for determining the oversteer and understeer situation of the vehicle using the measured value of the vehicle stability control device.

In general, the electronic control system of a vehicle is to obtain a strong and stable braking force by effectively preventing the slip phenomenon of the vehicle, an anti-lock brake system (hereinafter referred to as ABS) to prevent the sliding of the wheel during braking. ), A traction control system (hereinafter referred to as TCS) that prevents slippage of the drive wheel during sudden start or acceleration of the vehicle, and ABS and TCS are combined to control brake hydraulic pressure to improve driving stability of the vehicle. A vehicle stability control apparatus (Electronic Stability Program; hereinafter referred to as ESP) and the like are disclosed.

Among these, ESP is basically to control the yaw behavior of the vehicle, and it controls the braking system and the engine in the dangerous driving situation that reaches the contact limit of the tire when turning the vehicle so that the driver can turn to the desired trajectory. Device.

In general, when the vehicle is turning, as shown in FIGS. 1 and 2, an over steer is a spin out in which the vehicle is rolled inward based on a stable turning trajectory, or vice versa. Understeer, which is a drift out, is pushed out, which impairs the stability of the vehicle.

In order to prevent this, as shown in FIG. 1, the ESP applies a braking force to the outer wheels of the front wheels during the oversteer when the vehicle is rolled inwards and spins as compared to the trajectory desired by the driver. By generating an acting compensation moment, the vehicle is prevented from inwardly shifting in the driving trajectory, and as shown in FIG. 2, the rear wheel at the understeer is pushed out of the trajectory desired by the driver as the rotation radius of the vehicle increases. By applying a braking force to the inner wheel to create a compensating moment acting inwardly of the vehicle, it prevents the vehicle from being pushed outward from the desired trajectory, thereby keeping the trajectory of the vehicle stable.

As such, it is very important for the ESP to determine whether the vehicle currently being driven is drawing a stable trajectory or oversteer or understeer in order to secure stability of the turning vehicle.

Therefore, in the related art, a yaw rate model that uses the steering input of the driver and the driving speed of the vehicle as an input value is created, and the value obtained from the model is compared with the yaw rate value measured by the yaw rate sensor to determine the oversteer and understeer situation. Judging.

However, the conventional vehicle stability control method is relatively easy to determine the situation using a yaw rate model in the case of high friction road surface, but in the case of low friction road surface margin margin is very small compared to the high friction road surface Figure 3 As shown in Fig. 2, the oversteer and understeer behaviors are combined to make it difficult to accurately determine the situation of the vehicle using only the existing yaw rate model.

Therefore, in the case of low friction road surface, efforts have been made to more accurately determine the vehicle situation by using vehicle slip angle information in addition to the yaw rate model, but the value of the vehicle slip angle information is not a measured value such as the yaw rate. It is a value that can only be obtained through the change of the reliability depending on the driving situation has the disadvantage that can not secure the control performance of the ESP.

Accordingly, the present invention has been made to solve the above-described problems, an object of the present invention is to provide a vehicle stability control method that can determine the oversteer and understeer situation of the vehicle using only the sensor value that can be measured in the ESP. To provide.

Another object of the present invention is to provide a vehicle stability control method that can increase the reliability of the ESP control performance because it is possible to determine the oversteer and understeer situation of the vehicle through the parameters obtained by a combination of sensor measurements rather than an estimated value. To provide.

In order to achieve the above object, the present invention provides a method for controlling vehicle stability by using a steering angle, a wheel speed, and a yaw rate sensor that detects motion information of a vehicle, wherein the steering angle, wheel speed, and yaw rate sensor are used to control the size of the vehicle. Reading measured values of the vehicle longitudinal speed and yaw speed; And determining a situation of the vehicle based on sensor readings of the steering angle size, the vehicle longitudinal speed, and the yaw speed.

In addition, the present invention further comprises the step of reading the distance information between the front wheel and the rear wheel stored for each vehicle; The determining of the situation of the vehicle may include determining whether the situation of the vehicle is oversteer or understeer according to the result obtained by substituting the inter-axis distance information and the sensor measurement value read into [Formula] below in which the vehicle slip angle information is erased. It is characterized by determining the recognition.

Formula ( γ / V _x ) x ( l _f + l _r ) -δ

Where δ is the steering angle magnitude, V _x is the vehicle longitudinal speed, γ is the yaw speed, and l _f and l _r are the distance between the front and rear wheels.

The determining of the situation of the vehicle may include determining that the vehicle is oversteer if the result value obtained by substituting [formula] is positive, and understeer if it is negative.

Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings.

4 is a block diagram of a vehicle stability control apparatus according to the present invention, the ESP of the present invention is a steering angle sensor 10, wheel speed sensor 20, yaw rate sensor 30, ESP controller 40, brake control unit 50 and the engine control part 60 are comprised.

The steering angle sensor 10 detects the steering angle steering angle δ of the steering wheel at the time of steering, and the wheel speed sensor 20 is installed on a plurality of wheels (for example, four wheels), so that the vehicle's longitudinal speed V _x ), the yaw rate sensor 30 detects the yaw speed (γ) of the vehicle.

The ESP controller 40 receives signals detected from the steering angle sensor 10, the wheel speed sensor 20, and the yaw rate sensor 30 to determine whether the situation of the vehicle is oversteer or understeer. By controlling the braking pressure and the engine torque, the interaxial distance information storage unit 41, the oversteer / understeer determination unit 42, and the oversteer / understeer control unit 43 are included.

The interaxial distance information storage unit 41 stores the front wheel shaft distance l _f , which is the distance between the center of the front wheel shaft of the vehicle, and the rear wheel shaft distance l _r , which is the distance between the center of the rear wheel shaft of the vehicle. ( l _f , l _r ) The information is a predetermined constant value for each vehicle.

The oversteer / understeer determination unit 42 may include sensor measurement values input from the steering angle sensor 10, the wheel speed sensor 20, and the yaw rate sensor 30, and the inter-axis distance information storage unit 41. Distance ( l _f , l _r ) constant values are used to determine whether the vehicle is oversteer or understeer.

In addition, the oversteer / understeer determination unit 42 may determine the oversteer and understeer conditions of the vehicle using only the measured values generally obtained from the ESP and the constant values stored in advance. After calculating the equation for comparing the rear slip angle, it is determined whether the situation of the vehicle is oversteer or understeer according to the result obtained by substituting the measured values and constant values into the calculated equation.

The oversteer / understeer control unit 43 may include the brake control unit 50, the engine torque control unit 60 alone or the ABS control block 51 and the TCS control block 61 according to the determined oversteer or understeer situation. Cooperative control to control the braking force or the driving force of the engine to ensure the stability of the vehicle.

The brake control unit 50 controls the brake hydraulic pressure supplied to the wheel cylinder according to the braking signal output from the ESP controller 40 to cooperatively control the ABS control block 51 to generate the braking pressure. In addition, the engine controller 60 controls the engine torque according to the engine control signal output from the ESP controller 40 to cooperatively control the driving force of the engine by cooperatively controlling the TCS control block 61 to secure the maximum stability of the vehicle.

Hereinafter, the operation process and the effect of the vehicle stability control method of the present invention configured as described above will be described.

5 is an operation flowchart of a vehicle stability control method according to the present invention.

In FIG. 5, the oversteer / understeer determination unit 42 of the ESP controller 40 reads the steering angle δ size from the steering angle sensor 10, and the longitudinal speed V of the vehicle from the wheel speed sensor 20. _x ) is read, and the yaw speed γ of the vehicle is read from the yaw rate sensor 30 (S100).

In addition, the oversteer / understeer determination unit 42 reads constant values between the front wheel and the rear wheel ( l _f , l _r ) constants previously stored for each vehicle in the inter-axis distance information storage unit 41 (S110).

In general, before the vehicle enters into an unstable area based on the vehicle dynamics, the rear wheel is oversteered on the contrary, when the tire slip angle α _f of the front wheel is larger than the tire slip angle α _{r of the} rear wheel as shown below. The case where the tire slip angle α _r is larger than the tire slip angle α _f of the front wheel is defined as an understeer situation.

Vehicle situation = α _f - α _r > 0: oversteer

Vehicle Situation = α _r - α _f > 0: Understeer

Here, α _f is the tire slip angle of the front wheel (hereinafter referred to as front wheel slip angle) and α _r is the tire slip angle of the rear wheel (hereinafter referred to as rear wheel slip angle).

Therefore, to determine the front wheel slip angle ( α _f ) and the rear wheel slip angle ( α _r ) to determine the situation of such a vehicle, as shown in [Equation 1] and [Equation 2] below, some information including vehicle slip angle ( β ) information is available. You need information.

α _f = β + l _f γ / V _x - δ ...... [Equation 1]

α _r = β - l _r γ / V _x ...... [Equation 2]

Here, the steering angle δ and yaw velocity γ can be obtained directly by the sensor measurement value, and the vehicle longitudinal speed V _x can be assumed to be known because it can estimate a relatively accurate value. In addition, the distance between the wheels ( l _f , l _r ) is a constant value stored for each vehicle.

However, the vehicle slip angle β can be obtained by using a fairly complicated algorithm, but since the reliability varies depending on the driving situation, the front wheel slip angle α _f is obtained by the same method as in Equations 1 and 2. And after calculating the rear wheel slip angle α _r , the vehicle slip angle β information can be erased by comparing this value.

That is, when [Equation 1] and [Equation 2] are substituted into the equation of the vehicle situation, an equation for determining the vehicle situation is calculated as shown in [Equation 3] below.

Vehicle Situation = α _f - α _r = ( γ / V _x ) x ( l _f + l _r ) -δ ...... [Equation 3]

Therefore, in the present invention, as shown in the above [Equation 3], without using the vehicle slip angle ( β ) information, only the sensor measurement values ( δ , V _x , γ) and the constant values ( l _f , l _r ) are used. We would like to propose an expression that can be determined.

In conclusion, in order to determine the vehicle situation, the difference between the two values is actually needed, rather than the exact value of each of the front wheel slip angle α _f and the rear wheel slip angle α _r . The reliability of control performance is improved by using a new equation that eliminates vehicle slip angle ( β ) information that should be estimated.

Accordingly, if the result value of the calculation result obtained by substituting the sensor measurement values ( δ , V _x , γ) and the constant values ( l _f , l _r ) in the equation of [Equation 3] (S120) is oversteer / The understeer determining unit 42 determines that the vehicle situation at that time is an oversteer, and conversely, if the result value of the arithmetic expression is negative, it determines that it is understeer (S130).

The brake control unit 50, the engine control unit 60 alone or the ABS control block 51 in the oversteer / understeer control unit 43 according to the oversteer or understeer determination unit determined by the oversteer / understeer determining unit 42. And cooperative control with the TCS control block 61 controls the braking force or the driving force of the engine to secure the stability of the vehicle (S140).

As such, by controlling the engine using measured values generally obtained in the ESP, it is possible to secure the maximum stability of the vehicle even in a dangerous situation such as the control of the ESP.

As described above, according to the vehicle stability control method according to the present invention, a parameter for determining the oversteer and understeer conditions of the vehicle is obtained by using measured values generally obtained in the ESP. Since it is a parameter obtained by a combination of sensor measurement values rather than values, it is possible to increase the reliability of the ESP control performance by eliminating vehicle slip angle information that needs to be estimated.

What has been described above is only one embodiment for implementing the vehicle stability control method according to the present invention, the present invention is not limited to the above-described embodiment, the general knowledge of the art within the technical spirit of the present invention Of course, various modifications are possible by those who have.

Claims (4)

In the method of controlling the vehicle stability by using a steering angle, wheel speed and yaw rate sensor for detecting the movement information of the vehicle, Reading measured values of steering angle magnitude, vehicle longitudinal speed and yaw speed from the steering angle, wheel speed and yaw rate sensors; Determining a situation of the vehicle based on sensor readings of the steering angle size, the vehicle longitudinal speed, and the yaw velocity read; And Reading distance information between the front wheels and the rear wheels stored for each vehicle; Determining the situation of the vehicle, Vehicle stability control, characterized in that it is determined whether the situation of the vehicle is oversteer or understeer according to the result obtained by substituting the inter-axial distance information and the sensor measurement value read into [formula] in which the vehicle slip angle information is erased. Way. Formula ( γ / V _x ) x ( l _f + l _r ) -δ Where δ is the steering angle magnitude, V _x is the vehicle longitudinal speed, γ is the yaw speed, and l _f and l _r are the distance between the front and rear wheels. delete The method of claim 1, Determining the situation of the vehicle, And if the result value obtained by substituting the above formula is a positive number, determining the vehicle situation as oversteer. The method of claim 1, Determining the situation of the vehicle, And if the result value obtained by substituting the above formula is negative, determine the situation of the vehicle as understeer.

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