(a) Field of the Invention
The present invention relates to a system for preventing lane deviation of a vehicle and a control method thereof, and more particularly to a system for preventing deviation from a lane by a vehicle and a control method thereof, in which the driver is alerted when the vehicle inadvertently deviates from a lane.
(b) Description of the Related Art
Various technologies are continuously being developed for vehicles to improve safety and driving convenience. One such technology is a system for preventing deviation from a lane. That is, if the vehicle undergoes inadvertent deviation from a lane as a result of driver carelessness, drowsiness, etc., the system either warns the driver or performs control to correct the positioning of the vehicle. In more detail, the lane deviation prevention system determines the location of the lane markers defining the lane the vehicle is traveling in, then determines the location of the vehicle relative to the lane markers. If the vehicle is deviating from the lane, either the driver is warned or a steering actuator is operated to make corrections in the position of the vehicle.
The main elements of a vehicle lane deviation system (in the case where steering control is provided) are a photographing unit for obtaining photographs of the road on which a vehicle is traveling, an image processor for extracting positions of the lane markers and of the vehicle relative to the lane markers from the photographs, a steering controller for generating instructions as needed to make corrections in the position of the vehicle, and a steering actuator that is driven to adjust the steering of the vehicle according to the steering instructions generated by the steering controller. A CCD (charge coupled device) camera is generally used in the conventional lane deviation prevention system, and the actuator is typically a motor mounted in the steering column. The conventional lane deviation prevention system, therefore, is designed with the concept of assisting the driver, that is, of providing a degree of correctional control.
However, since in an image processing procedure of the conventional system algorithms are derived based on edges in the images to extract the lane markers, it is difficult to overcome the problem of noise in the image data. Also, a substantial amount of time is used in such an image processing procedure.
In addition to the image processing methods in which edges of the images are used, there is disclosed a method in which brightness levels in the images are used to extract lane markers. However, this method is error prone and performance easily varies with changes in the brightness of the images. That is, objects in the road may be mistaken for lane markers, and vehicle lane extraction proves difficult at night, on cloudy days, or other instances in which a peripheral brightness is low.
Also, since conventional systems are designed with the concept of providing a degree of correctional control as described above, the bulk of the re-positioning of the vehicle back between the lane markers during deviation must be performed manually by the driver. Therefore, there are not provided any countermeasures for the degree of control needed during more urgent situations.
The present invention has been made in an effort to solve the above problems.
It is an object of the present invention to provide a system for preventing lane deviation of a vehicle and a control method thereof, in which control is performed to prevent the vehicle from inadvertently deviating from a lane.
To achieve the above object, the present invention provides a system for preventing lane deviation of a vehicle and a control method thereof. The system comprises a detector including a lane marker detector for detecting lane markers that define a lane in a road, and a lane marker ECU for determining a transverse position of the vehicle using signals of the lane marker detector; a controller for determining if the vehicle is deviating from the lane by receiving information transmitted by the detector, determining steering control angle and steering control time according to a vehicle speed and a heading angle at the instant the vehicle is deviating from the lane, and outputting control signals following lane deviation prevention such that an automatic drive mode is realized until the vehicle reaches a center of the lane; and a steering driver controlled by the control signals output from the controller.
The lane marker detector is a magnetic sensor that detects magnetic nails installed in lane markers of the road.
Preferably, the controller comprises a communications unit for receiving information from the detector; an input data processor for processing information of various sensors and a steering torque sensor, and the transverse position received from the lane marker detector; a lane deviation determining unit for determining whether the vehicle is deviating from the lane using information transmitted from the input data processor; a fuzzy logic controller for calculating an amount of steering control according to information transmitted from the lane deviation determining unit; a steering angle instruction generator for generating a steering angle profile for controlling steering after the amount of steering control is determined by the fuzzy logic controller; a feedback control unit for generating a path for automatic driving following prevention of lane deviation; and an output data processor for outputting information received from the steering angle instruction generator and the feedback control unit.
The controller further comprises an initializing unit and a fail-safe unit.
In the method for preventing lane deviation of a vehicle, if it is determined that the vehicle is deviating from a lane using information of a transverse position of the vehicle, a steering control angle and a steering control time are determined using fuzzy logic according to a vehicle speed and a heading angle at an instant the vehicle deviates from the lane, thereby preventing lane deviation, after which feedback control of the transverse position of the vehicle is performed through a control variable and output as a steering angle such that the vehicle is positioned at a center of the lane in an automatic drive mode according to a given path, and controlling an actuator of an EPS system using the output.
The method comprises initializing variables and functions of a main ECU; checking information of a lane marker ECU and transmitting the information to an input data processor for processing of the information; determining driver intent to discontinue lane deviation prevention and determining whether lane deviation control is able to be performed; performing fail-safe control to determine whether a system for preventing lane deviation is malfunctioning in the case where there is no driver intent to discontinue lane deviation control and the vehicle is traveling in an area such that lane deviation control is able to be performed; determining if the vehicle is deviating from the lane based on information converted in an input data processor to suit an algorithm, in the case where it is determined that the system is operating normally; calculating an amount of steering control suitable to lane deviation conditions to generate a steering angle profile, in the case where it is determined that the vehicle is undergoing lane deviation; calculating a steering angle to return the vehicle to a center of the lane; and transmitting steering control data and steering angle data to an EPS system to realize steering control.
Here, processing of information by the input data processor includes conversion of input values of various sensors, a steering torque sensor, and of a transverse position of the vehicle.
The driver intent is preferably determined according to whether control switches have been operated, a brake pedal has been depressed, a steering wheel operated, and whether the vehicle is traveling in a no-service zone.
The fail-safe control is performed by determining if a control steering angle is normal and determining if a present vehicle speed is less than or equal to a predetermined vehicle speed.
The determination of whether the vehicle is deviating from the lane is performed by calculating a deviation prediction value according to vehicle speed using a transverse position of the vehicle and a heading angle value, which is the derivative of the transverse position.
The prediction value (p_offset) is obtained by offset_f+Kw*slope_f, where offset_f is the transverse position of the vehicle, slope_f is the derivative of offset_f, and Kw is a gain, which varies according to vehicle speed, and if the p_offset value is greater than one of a predetermined deviation position value OFF_L(left) and a predetermined position value OFF_R(right), it is determined that the vehicle is deviating from the lane.
The amount of steering control suitable to lane deviation conditions is calculated from inputs of vehicle speed and heading angle (slope_f) at the instant the deviation prediction value (p_offset) exceeds the predetermined deviation position value (OFF_L).
The steering angle profile is realized through a triangular waveform.
The steering angle is obtained from Kp * (offset_fxe2x88x92path)+Kd*slope_f, where Kp is P gain, Kd is D gain, offset_f is a transverse position of the vehicle, slope_f is a heading angle, and path is a desired path.