1 Construction of the co-simulation platform
Use veDYNA vehicle dynamics software to build the target vehicle model, use PreScan scene software to build a parallel parking scene model, combine path planning and path tracking control, build a co-simulation platform of veDYNA, PreScan and Simulink to perform the functions of the parallel parking control system verify.
Since both veDYNA software and PreScan software can call and simulate each other with Simulink, the state parameters of the vehicle dynamics model of veDYNA and the ultrasonic radar signal of PreScan can be transferred to the motion control model in Simulink, and the motion control model can also be controlled by Simulink. The output control quantity of the model is transferred to the veDYNA vehicle dynamics model. In addition, the state parameters of the veDYNA vehicle dynamics model need to be transferred to PreScan through Simulink, and the pose information of the vehicle in the parking scene is updated in real time.
The co-simulation platform needs to use the same reference coordinate system, and it is necessary to ensure the consistency of the horizontal and vertical coordinates of the vehicle. Since the vehicle coordinates of the veDYNA dynamic model are based on the center of the front axis, the vehicle coordinates of the PreScan scene model are based on the center of mass. In the path tracking control model The vehicle coordinates of , refer to the center of the rear axis, so it is necessary to convert the vehicle coordinates of the three models, which need to be represented by the same reference coordinate system, as shown in Figure 4.10. For the vehicle coordinates of the veDYNA dynamic model, in order to maintain the coordinate consistency with the motion control model, it needs to be converted into the vehicle coordinates with the rear axis center as the reference; in order to maintain the coordinate consistency with the PreScan scene model, it needs to be converted into the center of mass. vehicle coordinates for reference.
2 Simulation results and analysis
(1) Condition 1: The size of the parking space is normal, the vehicle is located in area 1 and there are no obstacles.
The simulation process is shown in the figure. It can be seen from the figure that when the starting position of the vehicle is in area 1, when the controller controls the vehicle to perform the parking operation, the vehicle does not collide with the parking space line and the road boundary line, which can control the safety of the vehicle. Drive into the parking space.
The simulation results are shown in the figure below. It can be seen from figures (a) and (b) that the path tracking control model can well control the vehicle to drive along the desired path, and the direction error is within the range, and the error can be well controlled . It can be seen from Figure © that the yaw angle of the vehicle changes continuously with time, and the error range between the actual yaw angle of the vehicle and the yaw angle of the desired path remains within the range of the yaw angle. When the vehicle travels along the desired path to the end point of the path, the yaw angle remains near zero. , the body is parallel to the parking space. It can be seen from Figure (d) that the vehicle speed controller can well control the speed of the vehicle to keep nearby, so that the vehicle can keep running smoothly during the parking process, and the influence of the change of the vehicle speed in the longitudinal direction on the path tracking effect is reduced. It can be seen from Figure (e) that the steering wheel angle of the vehicle changes continuously with time, and there is no sudden change, and the variation range of the steering wheel angle meets the requirements of the vehicle steering mechanism. turning situation. It can be seen from Figure (f) that the change of the steering wheel rotation speed of the vehicle with time is continuous, and there is no sudden change, and the variation range of the steering wheel rotation speed meets the requirements of the vehicle steering mechanism.
(2) Working condition 2: The size of the parking space is normal, the vehicle is located in area 2 and there are no obstacles.
(3) Working condition 3: The size of the parking space is normal, the vehicle is located in area 3 and there are no obstacles.
(4) Working condition 4: The size of the parking space is too small, and the vehicle is located in area 1 without obstacles.
When the size of the parking space is too small, the controller first controls the vehicle to drive along the desired parking path. When the system detects that the vehicle is driving to the rear boundary of the parking space, the controller controls the gear to switch from reverse to first gear, and controls the vehicle to drive forward. After the vehicle completely enters the parking space, the parking is completed. During the parking process, the vehicle does not collide with the parking space line and the road boundary line, which ensures the safety of the parking process.
(5) Condition 5: The size of the parking space is normal, the vehicle is located in area 1 and there are obstacles.
When the vehicle does not detect a pedestrian, the controller controls the vehicle to drive along the desired path; when the ultrasonic radar detects that the distance between the vehicle and the pedestrian is less than the set safe distance, the obstacle avoidance controller intervenes to control the vehicle to stop and avoid; When the distance meets the safety condition, the controller continues to control the vehicle to track the desired path until the parking is completed.
3 Description of the simulink model in this section
simulink model link
Since the simulink model in this section includes the vehicle kinematics veDYNA software and the simulation scene PreScan software, the simulink model in this section cannot be run. It is only for everyone to participate in the idea. You can replace the software with your own software. Such as Carsim, VTD, SCANeR, etc.
I can't find the model of working condition 4 now. Working condition 4 is similar to working condition 3, both of which need to switch gears to change the vehicle speed. There is not much difference between the two models. You can refer to the model of working condition 3.