KR20070105130A - Method to control engine of electronic stability program - Google Patents

Abstract

An engine control method of an ESP(Electronic Stability Program) system is provided to stabilize the yaw motion of a vehicle by compensating engine torque according to gear ratio, acceleration, and yaw motion information of the vehicle. An engine control method for controlling target torque for performing TCS(Traction Control System) controls in an ESP system comprises the steps of: setting the target torque by detecting the acceleration of the vehicle and the gear level(S100,S110); estimating yaw rate that a driver wants, by detecting vehicle speed and steering angle(S120,S130); measuring the yaw rate of the vehicle by detecting the yaw rate(S140); computing a yaw rate error according to the measured yaw rate and estimated yaw rate(S150); and calibrating the target torque set on the basis of the computed yaw rate error(S180,S200,S210).

Description

Engine control method of vehicle stability control system {Method to control engine of Electronic Stability Program}

1 is a block diagram of a vehicle stability control system according to the present invention;

2 is an operation flowchart of an engine control method of a vehicle stability control system according to the present invention;

3 is a graph showing a method of setting a target torque according to vehicle acceleration and gear number in engine control of a vehicle stability control system according to the present invention;

Figure 4 is a graph showing a method for correcting the target torque using the vehicle yaw behavior in the engine control of the vehicle stability control system 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: acceleration sensor

50: gear stage reading unit 60: ESP controller

61: yaw rate estimating unit 62: yaw rate error calculating unit

63: target torque setting unit 66: oversteer / understeer control unit

70: brake control unit 80: engine control unit

The present invention relates to an engine control method of a vehicle stability control system for stabilizing yaw motion of a vehicle through TCS engine torque control in a vehicle stability control system.

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 slip 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 system (hereinafter referred to as an ESP system) is disclosed.

Among them, the ESP system is basically to control the yaw behavior of the vehicle, and to control the braking system and the engine in a dangerous driving situation that reaches the tire contact limit when the vehicle is turning, inducing the driver to turn to the desired trajectory. Is a device that

In general, when the vehicle is turning, an oversteer, which is a spin out that is rolled inward based on a stable turning trajectory, or an drift out, which is pushed outward, is reversed. Is generated, which impairs the stability of the vehicle.

To prevent this, the ESP system generates a compensating moment that acts outward of the vehicle by applying braking force to the outer wheels of the front wheel during oversteer, when the vehicle's rotation radius decreases sharply and the vehicle is rolled inward relative to the desired trajectory. This prevents the vehicle from biasing inward from the driving trajectory.In contrast, when the understeer is pushed out of the desired trajectory as the rotation radius of the vehicle increases, the moment of compensation applied to the inside of the vehicle is applied by applying braking force to the inner wheel of the rear wheel. This prevents the vehicle from being pushed outward from the desired trajectory and keeps the trajectory of the vehicle stable.

As such, the ESP system applies a proper braking pressure to the front wheels and the rear wheels to secure the stability of the turning vehicle and secures the turning stability by controlling the TCS engine torque.

In calculating the target torque of the TCS engine control in such an ESP system, a target torque that increases linearly with the gear ratio and the vehicle acceleration is used. As a result, in the process of calculating the optimum torque according to the road surface change, the target torque value set on the ice road surface is often not appropriate on snow road or wet asphalt road surface.

Therefore, a method of using the target torque set according to the gear ratio and the acceleration of the vehicle by using the road surface information has been proposed, but this method also does not consider the yaw behavior of the vehicle, so that the driver's desired vehicle behavior can be smoothly controlled. There was a problem that could not be achieved.

In addition, when the engine torque is controlled by yaw control in the ESP system, there is a problem in that yaw behavior or RPM behavior frequently fluctuates because the frictional force of the road surface is not properly reflected.

Accordingly, the present invention has been made to solve the above-mentioned conventional problems, and an object of the present invention is to calculate the target torque for the TCS engine control in the ESP system. Accordingly, an engine control method of a vehicle stability control system for compensating engine torque and stabilizing yaw motion of a vehicle is provided.

According to an aspect of the present invention, there is provided a method of controlling a target torque of TCS engine control in a vehicle stability control system, the method comprising: setting a target torque of TCS engine control by detecting vehicle acceleration and a gear stage; Estimating a yaw rate desired by the driver by detecting the vehicle speed and the steering angle; Detecting the yaw rate and measuring the yaw rate of the vehicle; Calculating a yaw rate error according to the difference between the measured yaw rate and the estimated yaw rate; And correcting the target torque of the TCS engine control set based on the calculated yaw rate error.

The step of correcting the target torque of the TCS engine control may include determining whether the situation of the vehicle is oversteer or understeer according to the calculated result of the yaw rate error, and according to the calculated amount of the yaw rate error. The target torque of the control is adjusted.

The adjusting of the target torque of the TCS engine control may include setting a target torque of the TCS engine control lower than the oversteer to adjust the target torque according to the calculated variation in the yaw rate error when the vehicle is understeer. .

The adjusting of the target torque of the TCS engine control may include comparing the calculated absolute value of the yaw rate error with a predetermined reference value and lowering the target torque of the TCS engine control if the absolute value of the yaw rate error is larger than the reference value. It features.

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

1 is a block diagram of a vehicle stability control system according to the present invention, ESP of the present invention is a steering angle sensor 10, wheel speed sensor 20, yaw rate sensor 30, acceleration sensor 40, gear stage The reading unit 50 is configured to include an ESP controller 60, a brake control unit 70, and an engine control unit 80.

The steering angle sensor 10 detects the steering angle of the steering wheel during steering, and the wheel speed sensor 20 is installed on a plurality of wheels (for example, four) to detect the vehicle speed.

The yaw rate sensor 30 detects the yaw rate (MY; turning speed) of the vehicle, the acceleration sensor 40 detects the acceleration Ax of the vehicle, and the gear stage reading unit 50 measures the gear stage of the vehicle. (Gear ratio of 1st, 2nd, 3rd, and 4th stage) is read.

The ESP controller 40 receives signals detected from the steering angle sensor 10, the wheel speed sensor 20, the yaw rate sensor 30, the acceleration sensor 40, and the gear stage reading unit 50. The yaw rate estimating unit 61 and the yaw rate error are determined by controlling the brake control unit 70 and the engine control unit 80 for determining whether this is oversteer or understeer and controlling the braking pressure and engine torque of each wheel. The calculator 62, the target torque setting unit 63, the spin amount calculation unit 64, the road surface determination unit 65, and the oversteer / understeer control unit 66 are included.

The yaw rate estimator 61 estimates a yaw rate (CY) desired by the driver from the vehicle model by using the steering angle and the vehicle speed detected by the steering angle sensor 10 and the wheel speed sensor 20, and the yaw rate. The error calculating unit 62 compares the yaw rate MY detected by the yaw rate sensor 30 with the yaw rate CY estimated by the yaw rate estimating unit 61, and thus the yaw rate error. (DY) is calculated.

The target torque setting unit 63 sets the target torque of the vehicle according to the vehicle acceleration detected from the acceleration sensor 40 and the gear stage read from the gear stage reading unit 50, and the spin amount calculation unit 64 includes a plurality of target torques. The amount of spin generated in each drive wheel is calculated by measuring the speed of each drive wheel with the value detected from the wheel speed sensor 20 of the.

The road surface determination unit 65 may determine a value detected from the steering angle sensor 10, the wheel speed sensor 20, the yaw rate sensor 30, and the acceleration sensor 40 with a predetermined threshold value (the ESP control start value). In comparison, the road friction coefficient of the vehicle, that is, the road surface state is determined.

The oversteer / understeer controller 66 determines whether the state of the vehicle is oversteer or understeer by using the difference value of the yaw rate calculated by the yaw rate error calculator 62, and determines the oversteer or understeer. By adjusting the brake control unit 70, the engine torque control unit 80 alone or cooperative control with the ABS control block 71 and the TCS control block 81 according to the steer, the target torque of the TCS engine control to secure the stability of the vehicle is corrected. Decide

The brake control unit 70 controls the brake hydraulic pressure supplied to the wheel cylinder according to the braking signal output from the ESP controller 60 to cooperatively control the ABS control block 71 to generate the braking pressure so as to ensure the stability of the vehicle. In addition, the engine controller 80 controls the engine torque according to the engine control signal output from the ESP controller 60 to cooperatively control the driving force of the engine by cooperatively controlling the TCS control block 81 to secure the maximum stability of the vehicle.

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

The present invention is to control to stabilize the spin of the drive wheel by using the gear ratio and acceleration of the vehicle, the yaw behavior information of the vehicle in calculating the target torque of the TCS engine control in the ESP system.

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

In FIG. 2, the acceleration Ax of the vehicle being driven is read by the acceleration sensor 40, and the gear stage (gear ratio of the first, second, third, and fourth stages) of the vehicle is read by the gear stage reading unit 50. Read from (S100).

The target torque of the vehicle to be controlled is set by receiving the read-in vehicle acceleration Ax and the gear stage from the target torque setting unit 63 of the ESP controller 60 (S110).

This is because the amount of engine torque to be controlled varies depending on the number of gears.

For example, in the first gear, spin occurs at the wheel of the vehicle at a smaller torque level, and a larger amount of torque down is required to secure the traction of the vehicle.

As the number of gears goes up, less torque down is required than in the case of the first gear, but the amount of torque down required increases non-linearly.

In the case of ice roads, the wheels of the vehicle generate spin at a smaller torque level, and a greater amount of torque down is required to secure the vehicle's traction. Less torque down is required compared to the case. However, this amount increases nonlinearly. This is illustrated in FIG. 3.

In FIG. 3, compensation is performed using information on a current torque control amount and wheel behavior of a vehicle in a target torque value. If the wheel behavior of the vehicle is stable, the target torque maintains the previous engine control, and if the vehicle is turning, the target torque is lowered even lower.

Next, in calculating the target torque of the TCS engine control in the ESP system, when the target torque is calculated through the compensation as described above, the yaw behavior of the vehicle is used for the control using the sensor information mounted on the vehicle.

To this end, the yaw rate estimator 61 of the ESP controller 60 reads the vehicle speed Vx and the steering angle from the steering angle sensor 10 and each wheel speed sensor 20 (S120), and reads the vehicle speed ( Vx) and steering angle data are used to estimate a yaw rate (CY) desired by the driver from the vehicle model (S130). The method of estimating the yaw rate CY using the vehicle speed Vx and the steering angle data in the yaw rate estimating unit 61 will be omitted.

Then, the yaw rate error calculation unit 62 of the ESP controller 60 reads the yaw rate MY from the yaw rate sensor 30 when the vehicle actually travels (S140) and is measured from the yaw rate sensor 30. The yaw rate DY is compared with the yaw rate CY estimated by the yaw rate estimating unit 61 to calculate a difference value between the two yaw rates, that is, a yaw rate error (DY = MY-CY) (S150).

In this case, the yaw rate error DY calculated by the yaw rate error calculating unit 62 has a positive value in an oversteer situation and a negative value in an understeer situation.

Accordingly, the ESP controller 60 determines whether the vehicle is in an oversteer situation (S160), and compares an absolute value of the yaw rate error DY with a predetermined reference value DY2 (Threshold) in an oversteer situation (S170). If the absolute value of the rate error DY is larger than the reference value DY2, the target torque of the TCS engine control is set low to control to stabilize the yaw behavior of the vehicle (S180).

On the other hand, the ESP controller 60 compares the absolute value of the yaw rate error DY with a predetermined reference value DY1 (Threshold) when the vehicle is understeer in S160 (S190), and the absolute value of the yaw rate error DY. If the reference value DY1 is larger than the reference value DY1, the target torque of the TCS engine control is set lower than that of the oversteer situation to control the stabilization of the yaw behavior of the vehicle (S200).

When the absolute value of the yaw rate error DY is smaller than the reference value DY2 or DY1 in the oversteer or understeer situation, the ESP controller 60 maintains the target torque of the TCS engine control without compensation (S210).

However, when the absolute value of the yaw rate error DY is larger than the reference value DY2 or DY1, the target torque is set low to focus on stabilizing the yaw behavior of the vehicle.

As described above, in the case of the oversteer situation, the time for compensating the target torque is slower than the understeer situation, and the amount for compensating the target torque is less than that for the understeer situation. This is illustrated in FIG. 4.

When the yaw behavior of the vehicle is in an unstable area or is rapidly progressing to the unstable area, the ESP controller 60 suppresses the spin between the road surface and the wheel through traction control and needs to perform a torque up. Torque down is performed to stabilize the yaw behavior.

In addition, when the yaw behavior of the vehicle lies in the stable area or is rapidly progressing to the stable area, the ESP controller 60 lacks a traction control amount to spin between the road surface and the wheel even when torque rise is required. If this is increased, torque down is performed to stabilize the RPM behavior.

This can be summarized as follows.

Torque Compensation = PGY * DY + DGY * DDY + PGS * DV + DGS * DDV

Here, PGY is a gain value used when torque compensation is performed according to the difference in yaw rate error, DY is a yaw rate error magnitude, and DGY is used when torque compensation is performed according to the magnitude of yaw rate error. The gain value, DDY is the variation in yaw rate error, PGS is the gain value used when torque compensation is performed according to the size of the wheel spin, DV is the variable value representing the wheel spin behavior, and DGS is the magnitude of the wheel spin increase amount. Therefore, the gain value used when the torque compensation is performed, DDV is the wheel spin increase amount.

As such, by controlling the pressure of each wheel and engine torque at the same time by using the driving information of the vehicle in the ESP system, the stability of the vehicle can be maximized even in a dangerous situation such as the control of the ESP.

As described above, according to the engine control method of the vehicle stability control system according to the present invention, in calculating the target torque for the TCS engine control in the ESP system according to the gear ratio and acceleration of the vehicle, the yaw behavior information of the vehicle Engine torque can be compensated for to stabilize the yaw motion of the vehicle.

What has been described above is only one embodiment for implementing the engine control method of the vehicle stability control system according to the present invention, the present invention is not limited to the above-described embodiment, it is within the technical spirit of the present invention Various modifications are possible by those skilled in the art.

Claims (4)

In the method of controlling the target torque of the TCS engine control in the vehicle stability control system, Setting a target torque of the TCS engine control by detecting the vehicle acceleration and the gear stage; Estimating a yaw rate desired by the driver by detecting the vehicle speed and the steering angle; Detecting the yaw rate and measuring the yaw rate of the vehicle; Calculating a yaw rate error according to the difference between the measured yaw rate and the estimated yaw rate; And Correcting the set target torque of the TCS engine control based on the calculated yaw rate error. Engine control method of a vehicle stability control system comprising a. The method of claim 1, Correcting the target torque of the TCS engine control, It is determined whether the situation of the vehicle is oversteer or understeer according to the calculated value of the yaw rate error. And a target torque of the TCS engine control according to the calculated variation in the yaw rate error. The method of claim 2, Correcting the target torque of the TCS engine control, And setting the target torque of the TCS engine control to be lower than the oversteer if the vehicle situation is understeer. The method of claim 2, Correcting the target torque of the TCS engine control, And comparing the calculated absolute value of the yaw rate error with a predetermined reference value and lowering the target torque of the TCS engine control if the absolute value of the yaw rate error is larger than the reference value.

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