A Path Follower That Adjusts Its Command to Meet the Limit of Acceleration Margin

The intelligent and safe transportation is pursued in the vehicular industry. The higher level of Automated Driving Assistance System (ADAS) and Autonomous Driving System (ADS) are considered the promising solutions. However, subsystems inside are developed individually without considering the interaction among the intelligent functionalities and motions. It may cause issues on system integration. For example, Decision Subsystem in ADS normally defines the reference trajectory and the speed profile without considering the vehicle dynamics and its operating limit. The vehicle might not be able to achieve the requirement. The risks of the vehicle leaving the defined track or doing unexpected behaviors may occur. The Control Subsystem thus needs to acquire the operating limit information of vehicular motion to ensure vehicle safety.To deal with the aforementioned issue, a path follower which obtains the functionality of self-diagnosis and vehicle speed adjustment is designed as an approach in this paper. With the acquired road adhesion(μ), both the longitudinal and lateral acceleration margin, which is regarded as the acceleration limit of a vehicle, can be calculated as the boundary of vehicle dynamic operation. The margin is thus crucial for the Control Subsystem to determine the proper speed for path following.In this paper, the Control subsystem with the proposed function is examined through a Model-in-the-Loop (MiL) test with Carsim-PreScan co-simulation. According to the results, the system is verified to be able to control the vehicle on track by adjusting its target speed. The issue on the system coupling among upper-lower level subsystems can thus be resolved.