| Popis: |
This paper presents drift control for path tracking without prior knowledge of drift equilibria. Keeping the vehicle on the desired path while maintaining high side slip angle is a challenging task for not only professional drivers but also control systems. There are two issues which make path tracking with high side slip angle difficult. First, the driver or control system must maintain the vehicle states on the drift equilibrium. Second, the control inputs to maintain drifting must also stabilize the path tracking error dynamics. In the previous researches, pre-calculated drift equilibrium was utilized to design the path and maintain the drifting. However, an accurate tire model is needed to calculate drift equilibrium. The novelty of this work lies in the path tracking algorithm without knowledge of drift equilibria. The proposed algorithm consists of three consecutive parts. First, the supervisor determines desired yaw rate to stabilize the path tracking error dynamics considering path tracking error state constraints. Second, the upper level controller determines desired lateral force to track desired yaw rate and desired longitudinal force to keep rear wheels spinning. Third, lower level controller converts desired forces to actuator inputs, steering wheel angle and accelerator pedal input. The performance overall control algorithm has been investigated via simulations while the performance of upper and lower level controller has been investigated via vehicle tests. It can be shown that the proposed algorithm is capable of tracking basic desired path without any prior knowledge of drift equilibrium. Furthermore, the vehicle test results for upper and lower level controller show that the part of algorithm is capable of tracking yaw rate while maintaining high side slip angle. |
