Adaptive Cruise Control System With Traffic Jam Tracking Function

The traditional adaptive cruise control(ACC)system generally requires the speed over 25-40 km/h or higher speed to be activated.It can neither decelerate the host vehicle to a stop state nor adjust it when facing stationary objects.It also has a shortcoming that the system always lead to a large safety distance,which does not meet divers’ driving habits.All these defects limit the application of ACC system.In this paper,the combination of millimeter-wave radar and laser ranging sensor is adopted to achieve the recognition of low speed or stationary target.The paper also adds low-speed tracking function and traffic jam follow-up function to the traditional ACC system.It can achieve a deceleration to stop state and be able to adjust for stationary objects.This all functions expand the range of applications for ACC systems.The main research content of this paper are as follows:1.Designed the ACC system’s control logic,real-time debugging and user interface design.Obtained the free acceleration of the vehicle and removed the component of the gravity acceleration in the carrier coordinate system,thereby eliminated the influence of the gradient of the road surface on the acceleration data measured by the sensor.To reduce the influence of the road surface undulation,body vibration and obtain accurate data of distance,the speed of host car and acceleration,this paper used Kalman filtering algorithm.Designed a target tracking algorithm by using the threshold method and Kalman filtering algorithm.By using this algorithm,realized the sensor fusion of millimeter-wave radar and laser ranging sensor,which can correct the relative velocity to the true value and is beneficial to the final smooth control.2,Collected and analyzed the skilled driver’s driving data.Then three control modes of smooth,safe,and aggressive are divided based on the driver’s acceleration data distribution,this three control modes correspond respectively to the cruise control,low-speed tracking,and traffic jam follow-up condition.It can make the ACC system more in line with the realistic driver’s behavior.The safe vehicle distance function under the cruise control of the vehicle is based on the constant time-gap,the safe vehicle distance function under the low speed following condition is fitted by the segmented quadratic fitting algorithm,and the safe vehicle distance function when approaching the front stationary target is fitted by the BP fitting method.3.According to the current spacing,the host vehicle speed,the velocity of the front vehicle and the current control mode,calculated the real-time expected speed and expected acceleration.The expected driving force and expected braking force can be calculated based on the expected acceleration.By collecting accelerations corresponding to different throttles in different gears,the function curves of throttle and driving force under different gears are established;the brake pedal stroke and braking force function curves are established by collecting the accelerations corresponding to different brake pedal strokes.Thus,the ideal opening degree of the current electronic throttle or the ideal stroke of the brake pedal can be calculated according to the desired driving force or the desired braking force.Considering that the calculated opening degree of the throttle or brake pedal stroke may have error,fuzzy-control is added at the actuator to form a closed-loop control of the throttle and the brake,which achieve longitudinal acceleration and deceleration control of the ACC vehicle.4.The signal processing comparison experiments and the ACC vehicle experiments are performed in this paper.Signal processing comparison experiments include the comparison of original signals and the signals after Kalman filtering.This paper compares the signal processed by the target tracking algorithm designed by the threshold method and Kalman filtering method with the original signal and Kalman filtering signal,and verifies the superiority of the target tracking algorithm.The vehicle experiments include cruise control,low-speed tracking,and traffic jam follow-up experiments.The experimental results show that the distance and acceleration errors are within the driver’s expected error range,especially in the case of low-speed tracking and the distance keep within 13 meters,and the distance is basically controlled at about 3.5 meters when front vehicle is stopped,all this data meets the driving habits of the driver under the premise of ensuring safety.