KR101315780B1 - Apparatus and method for electronic stability program in a vehicle - Google Patents

Abstract

The present invention relates to a vehicle attitude control apparatus and a control method thereof. In particular, when the tire pressure of a corresponding wheel is not an appropriate pressure using each tire air pressure information during vehicle attitude control, a braking force due to a tire pressure difference is applied to the same wheel. By increasing the braking force as compensable, the stability of the vehicle can be improved.

Description

Vehicle attitude control device and its control method {APPARATUS AND METHOD FOR ELECTRONIC STABILITY PROGRAM IN A VEHICLE}

The present invention relates to a vehicle attitude control device and a control method thereof, and more particularly, to a vehicle attitude control device and a control method for controlling the vehicle attitude in consideration of the air pressure information of each tire.

In general, an electronic stability control (ESC) device is an apparatus for optimally controlling a vehicle's driving position, and is an anti-lock brake system (ABS) that prevents the wheel from being locked during braking. Next generation device. The ESC system instantly controls each of the four wheels independently in order to maintain stability when the vehicle is about to slide, enhancing driving stability on dry roads, rain, gravel roads and snow roads.

Such an ESC device has a driver's desired turning speed value (yaw rate value) estimated from a sensor of a vehicle such as a wheel speed sensor, a pressure sensor, a steering angle sensor, a lateral acceleration sensor, and an actual turning speed detected by the turning speed sensor. By comparing the values, it is determined whether the state of the vehicle is the oversteer that is inward in the direction of the vehicle's turning or the understeer which is out of the direction of the vehicle's turning. Applying a braking force to the understeer, while applying a braking force to the turning inner wheel to pressurize the brake hydraulic pressure to secure the stability of the vehicle by performing the attitude control of the vehicle. That is, during oversteering, the braking force is applied to the outer wheel turning outer wheel to generate a compensating moment acting outward of the vehicle, and in case of understeering, the steering wheel is prevented from being lost. By creating an acting compensation moment, the vehicle is prevented from being pushed outwards on the desired trajectory.

In addition, the vehicle is equipped with a tire pressure monitoring system (hereinafter referred to as a TPMS device). This TPMS system monitors the tire pressure and warns the driver when it falls below the specified pressure because the tire pressure is too high or too low, which can cause the tire to burst or the vehicle can slip easily and lead to an accident. Prevent it.

In the related art, since the ESC device does not receive tire air pressure information from the TPMS device, there is a problem that vehicle stability control cannot be performed in consideration of tire air pressure information.

One aspect of the present invention provides a vehicle attitude control apparatus and a method of controlling the vehicle's stability by controlling the braking force of the vehicle using tire pressure information during vehicle attitude control.

The vehicle attitude control apparatus of the present invention for achieving the above object uses a tire pressure sensing system for detecting tire pressure of each wheel, and the tire pressure detected for each wheel and the side sliding angle of each tire estimated from the vehicle model. Estimating the lateral force acting on each wheel, respectively, estimating the first braking force corresponding to each lateral force, and comparing the first braking force with the second braking force corresponding to the appropriate tire pressure of the corresponding wheel. When higher or lower than the second braking force, ESC controller for increasing the braking force of the wheel on the same side as the wheel when the vehicle attitude control.

In addition, the control method of the vehicle attitude control apparatus according to an embodiment of the present invention detects the tire pressure of each wheel, estimates the side slip angle of each wheel from the vehicle model, the detected tire pressure and the estimated side Estimating the lateral force acting on the wheel using the slip angle, comparing the first braking force corresponding to the estimated lateral force of the wheel with the second braking force required at the appropriate tire pressure of the wheel, and comparing the first When the braking force is higher or lower than the second braking force, it may include braking the wheel on the same side as the corresponding wheel during vehicle attitude control.

According to an embodiment of the present invention, when the tire pressure of the corresponding wheel is not appropriate pressure by using each tire air pressure information when controlling the vehicle attitude, the braking force as much as the braking force due to the tire pressure difference on the same wheel can be compensated. By increasing the stability of the vehicle can be improved.

In addition, according to an embodiment of the present invention, when the tire pressure of the outer wheel turning outer wheel during oversteering is not an appropriate pressure, the braking force due to the tire pressure difference may be compensated to the rear wheel turning outer wheel which is the same wheel. Oversteer by increasing the braking force and increasing the braking force to compensate for the braking force caused by the tire pressure difference on the front wheel turning inner wheel, which is the same wheel, if the tire pressure of the rear wheel turning inner wheel is not the proper pressure during understeering. It is possible to prevent loss of coordination of the vehicle at the time of, and to prevent the vehicle from being pushed outward from the desired trajectory at the time of understeer.

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

1 shows a schematic configuration of a vehicle attitude control apparatus according to an embodiment of the present invention.

As shown in FIG. 1, the vehicle attitude control apparatus according to an exemplary embodiment of the present invention includes a steering angle sensor 10, a vehicle speed sensor (orbital speed sensor 30), an orbital speed sensor 30, and an lateral acceleration sensor 40. ), The brake pressure sensor 50, the ESC controller 60, the brake control unit 70 and the engine control unit 80 is configured.

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

The revolution speed sensor 30 detects the yaw rate of the vehicle, the lateral acceleration sensor 40 detects the lateral acceleration Ax of the vehicle, and the brake pressure sensor 50 detects the master pressure. .

The ESC controller 60 receives signals detected from the steering angle sensor 10, the vehicle speed sensor 20, the turning speed sensor 30, the lateral acceleration sensor 40, and the brake pressure sensor 50 to determine the situation of the vehicle. The reference momentum setting unit 61 and the vehicle momentum measuring unit determine whether the oversteer or the understeer, and control the brake control unit 70 and the engine control unit 80 for controlling the braking pressure and engine torque of each wheel. (62), an exercise amount error calculation unit 63, a road surface determination unit 64, an understeer / oversteer determination unit 65, and an understeer / oversteer control unit 66.

The reference momentum setting unit 61 sets a stable reference value representing the trajectory of the vehicle 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 vehicle speed sensor 20. The stability reference, which indicates the trajectory of the desired vehicle, can be represented by the turning speed, which is determined from the steering angle and the vehicle speed based on the basic vehicle dynamics.

The vehicle momentum measuring unit 62 measures the actual vehicle momentum through values detected from the steering angle sensor 10, the vehicle speed sensor 20, the turning speed sensor 30, the lateral acceleration sensor 40, and the brake pressure sensor 50. And the momentum error calculation unit 63 compares the actual reference value measured by the vehicle momentum measurement unit 62 with the stable reference value set by the reference momentum setting unit 61, that is, the difference between the vehicle momentum and the stability reference value, that is, the amount of momentum. Calculate the error.

The road surface determination unit 64 uses the magnitude of the lateral acceleration detected by the lateral acceleration sensor 40 to determine the state of the road surface on which the vehicle travels, that is, the coefficient of friction between the tire and the road surface and the side slip angle. To judge.

The understeer / oversteer determination unit 65 determines whether the state of the vehicle is understeer using the difference in the amount of exercise calculated by the momentum error calculation unit 63 and the road friction coefficient determined by the road surface determination unit 64. Or oversteer.

The understeer / oversteer control unit 66 controls cooperative control with the brake control unit 70, the engine torque control unit 80 alone or the ABS control block 71 and the TCS control block 81 according to the determined understeer or oversteer. By controlling the braking force or the engine driving force to secure the stability of the vehicle, and the rotational speed and the lateral acceleration estimated from the sensors 10 and 20 of the vehicle to limit the turning speed, which is the criteria for determining vehicle stability in the vehicle stability control system. Determine the turning speed limit time and limit size by judging the road surface according to the size of.

In addition, the understeer / oversteer control unit 66 may apply the braking device of the front wheel when an oversteer phenomenon occurs because the rear wheel first reaches the adhesion limit between the tire and the road surface according to the determination of the understeer / oversteer determining unit 65. Control to reduce the turning moment generated by the front wheels. On the contrary, when the front wheel first reaches the adhesion limit between the tire and the road surface and the understeer phenomenon occurs, the rear wheel is controlled to move the vehicle in the desired trajectory. When the road friction coefficient is changed, more severe oversteering phenomenon may occur.In this case, when the difference between the vehicle movement amount and the stabilization reference value increases by more than the prescribed value, the vehicle's stability is secured by controlling the outer wheel outside the front wheel as well. .

In addition, the understeer / oversteer control unit 66 minimizes rocking of the vehicle due to excessive braking force by reducing the driving force caused by the engine when the braking force is insufficient for optimum stability and riding comfort. The required driving force reduction is achieved through controller area network (CAN) communication with the engine ECU.

The brake control unit 70 controls the brake hydraulic pressure supplied to the wheel cylinder according to the braking signal output from the ESC controller 60 to cooperatively control the ABS control block 71 to generate a braking pressure to ensure the stability of the vehicle. In addition, the engine controller 80 controls engine driving according to the engine control signal output from the ESC 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.

Figure 2 shows the configuration of the TPMS device connected to the vehicle attitude control apparatus according to an embodiment of the present invention.

As shown in FIG. 2, the TPMS device 90 includes four TPMS sensor modules 92a, 92b, 92c, and 92d for detecting and wirelessly transmitting tire pressure, and the TPMS sensor modules 92a, 92b, 92c, 92d) is provided with the TPMS control module 91 for wirelessly receiving the tire pressure information from the tire pressure change.

The TPMS sensor modules 92a, 92b, 92c, and 92d include a pressure sensor for detecting tire pressure and a microcomputer for performing overall control.

The TPMS control module 91 is can-communicated with the ESC controller 60. Sends a control command to the TPMS sensor module 92a, 92b, 92c, 92d, receives and recognizes tire pressure information from the TPMS sensor module 92a, 92b, 92c, 92d, and alerts the user if there is an error. do. In addition, the TPMS control module 91 provides the received pressure information of each tire to the ESC controller 60 so that the vehicle attitude control can be performed in consideration of the pressure of each tire during the ESC control (vehicle attitude control).

3 is for explaining the lateral sliding angle of the tire caused by the lateral force in the vehicle attitude control apparatus according to an embodiment of the present invention, Figure 4 is for explaining the relationship between the lateral force, tire pressure, side sliding angle .

As shown in FIG. 3, the lateral force is applied when the vehicle is turned to generate deformation at a portion where the tire contacts the road surface. This deformation causes the angle between the direction of the center plane of the wheel and the direction of travel of the wheel to be distorted. This twisted angle is the side slip angle of the wheel. If one tire pressure is low, this deformation is even worse, resulting in increased weight transfer to the tire and increased lateral slip angle.

As shown in FIG. 4, the lateral force applied to the tire is the maximum at an appropriate tire pressure, and can be seen to decrease when less than or greater than this value. And the larger the side sliding angle, the greater the lateral force.

Lateral force has a great influence on the stability of the vehicle attitude. The maximum lateral force generated between the tire and the road surface is determined according to various road surfaces. In the ESC system, the lateral force required to control the vehicle's unstable posture is obtained by using the braking force of each wheel. If the tire air pressure is lower or higher than the proper pressure, the lateral force greater than the normal control is required.

When the tire inflation pressure information is reflected in the control amount in the ESC device, it is possible to improve the stability control of the vehicle in an emergency situation. As mentioned above, the lateral force acting on the tire is affected by the tire air pressure. The ESC controller 60 calculates the lateral force necessary for the stability of the vehicle using information received from various sensors and converts it into a braking force to control the stability of the vehicle. At this time, the braking force is converted using the friction between the road surface and the tire. The lower the tire pressure, the greater the lateral sliding angle of the wheels with the same lateral force, and the smaller the lateral force of the tire. The corresponding lateral force is obtained using the measured tire pressure and the estimated lateral slip angle, and the braking force converted from the lateral force is compared with the braking force required at the proper tire pressure, and the difference is controlled using the wheel on the same side.

For example, as illustrated in FIG. 5, when oversteer control is required when the tire pressure of the front wheel turning outer wheel is less than or equal to the proper pressure, the braking force difference described above is applied to the wheel on the same side, that is, the rear wheel turning outer wheel. Increases the braking power of the vehicle to perform ��� amount attitude control.

In addition, as shown in FIG. 6, when understeer control is required when the tire pressure of the rear wheel inner wheel is less than or equal to the proper pressure, the braking force equal to the braking force difference described above on the wheel on the same side, that is, the front wheel inner wheel. To increase vehicle posture control.

Referring to FIG. 7, the ESC controller 60 determines whether the turning braking is in operation 100, and detects the actual yaw rate, which is the turning speed value, in the turning braking speed sensor 30 when turning the braking. After detecting the actual yaw rate, the ESC controller 60 estimates the yaw rate desired by the driver from the vehicle model (102), and the actual yaw rate estimated by the driver's desired yaw rate and the turning speed sensor 30 estimated from the vehicle model. The difference between the rates is calculated (103).

Then, the ESC controller 60 determines whether the vehicle behavior is oversteer or understeer from the yaw rate error (104). If the vehicle behavior is oversteer (104), in general, the braking force of the front wheel turning outer wheel (FR) is increased, but if the tire pressure of the front wheel turning outer wheel is lower or higher than the normal pressure, the above-described problem may occur. If the vehicle behavior is oversteer, the ESC controller 60 first. The tire pressure of the front wheel turning outer wheel is sensed (105), and the side slip angle of the front wheel turning outer wheel is estimated from the vehicle model (106). Then, the lateral force of the front wheel turning outer wheel is estimated from the tire pressure and the side sliding angle of the front wheel turning outer wheel (107). This lateral force is then converted into braking force (108), and the difference between the normal braking force of the front wheel turning outer wheel and this converted braking force when the front wheel turning outer wheel is the normal tire pressure is calculated (109), and the braking force by this difference Is applied to the rear wheel turning outer wheel which is the same side wheel as the front wheel turning outer wheel to increase the braking force of the rear wheel turning outer wheel (110).

On the other hand, if the vehicle behavior is understeer (111), in general, the braking force of the rear wheel turning inner wheels (RL) increases but the tire pressure of the rear wheel turning inner wheels is lower or higher than the normal pressure described above problems If the vehicle behavior is understeer, ESC controller 60 first. The tire pressure of the rear wheel turning inner wheel is sensed (112), and the side slip angle of the rear wheel turning inner wheel is estimated from the vehicle model (113). Then, the lateral force of the front wheel turning outer wheel is estimated (114) from the tire pressure? Side sliding angle of the rear wheel turning inner wheel. Then, the lateral force is converted into braking force (115), and the difference between the normal braking force of the rear wheel turning inner wheel and this converted braking force when the rear wheel turning inner wheel is normal tire pressure is calculated (116), and the braking force by this difference is calculated. Is applied to the front wheel turning inner wheel FL, which is the same wheel as the rear wheel turning inner wheel, to increase the braking force of the front wheel turning inner wheel (117).

1 is a control block diagram of a vehicle attitude control apparatus according to an embodiment of the present invention.

2 is a view showing the configuration of a TPMS device connected to the vehicle attitude control apparatus according to an embodiment of the present invention.

3 is a view for explaining the side sliding angle of the tire caused by the lateral force in the vehicle attitude control apparatus according to an embodiment of the present invention.

Figure 4 is a graph for explaining the relationship between the lateral force, tire pressure, side sliding angle in the vehicle attitude control apparatus according to an embodiment of the present invention.

5 is a view for explaining the increase in braking force to the rear wheel turning outer wheel (RR) when the tire pressure of the front wheel turning outer wheel (FF) is low during oversteering in the vehicle attitude control apparatus according to an embodiment of the present invention. .

FIG. 6 is a view for explaining the increase in braking force to the front wheel turning outer wheel FL when the tire pressure of the rear wheel turning inner wheel RL is low during the understeering in the vehicle attitude control apparatus according to the embodiment of the present invention. .

7 is a control flowchart illustrating a control method of the vehicle attitude control apparatus according to an embodiment of the present invention.

[Description of the Reference Numerals]

10: steering angle sensor 20: vehicle speed sensor

30: revolution speed sensor 40: lateral acceleration sensor

60: ESC controller 61: reference momentum setting unit

62: vehicle momentum measurement unit 63: momentum error calculation unit

64: road decision unit 65: understeer / oversteer determination unit

66: understeer / oversteer control unit 70: brake control unit

80: engine control unit 90: TPMS device

Claims (7)

Tire pressure detection system that detects the tire pressure of each wheel, Using the tire pressure sensed by each wheel and the side sliding angle of each tire estimated from the vehicle model, the lateral force applied to each wheel is estimated, the first braking force corresponding to each lateral force is estimated, and each first braking force is estimated. ESC controller for increasing the braking force of the wheel on the same side when the vehicle attitude control when the first braking force is higher or lower than the second braking force by comparing the second braking force corresponding to the proper tire pressure of the wheel. Vehicle attitude control device comprising. The method of claim 1, The ESC controller is a vehicle attitude control device for applying a braking force to the rear wheel turning outer wheel as the difference between the first braking force and the second braking force for the front wheel turning outer wheel when the vehicle oversteer. The method according to claim 1 or 2, The ESC controller is a vehicle attitude control device for applying the braking force to the front wheel turning outer wheels by the difference between the first braking force and the second braking force for the rear wheel turning inner wheels when the vehicle understeer. Detect the tire pressure on each wheel, Estimate the lateral slip angle of each wheel from the vehicle model, Using the detected tire pressure and the estimated lateral slip angle to estimate a lateral force acting on the wheel, Comparing the first braking force corresponding to the estimated lateral force of the wheel with the second braking force required at the appropriate tire pressure of the wheel, And comparing the first braking force with the first braking force higher or lower than the second braking force, by braking the wheel on the same side as the corresponding wheel during vehicle attitude control. 5. The method of claim 4, Calculating a difference value between the first braking force and the second braking force and braking the wheel on the same side as the corresponding wheel by the braking force equal to the calculated difference. The method of claim 5, When the first braking force is higher or lower than the second braking force, it is determined whether the corresponding wheel is the front wheel and the oversteer control of the vehicle is required, and if the wheel is the front wheel and the oversteer control of the vehicle is necessary, the same rear wheel is braked. Control method of the vehicle attitude control device. The method according to claim 5 or 6, When the first braking force is higher or lower than the second braking force, it is determined whether the corresponding wheel is the rear wheel and the understeer control of the vehicle is required, and if the wheel is the rear wheel and the understeer control of the vehicle is required, the same front wheel is braked. Control method of the vehicle attitude control device.

Images