Emergency Escape Manoeuvre of a Faulty Truck in a Platoon Formation Moving in Highway

Abstract

The platooning of trucks provides significant benefits in the existing transportation systems regarding social, economic and environmental aspects. Due to the platoon's high dependence on sensors, it is critically important to have fault-tolerant countermeasures that deal efficiently with failures by achieving minimal risk condition. This thesis tackles designing an emergency escape manoeuvre for a faulty truck that has lost its ability to monitor the driving environment while moving in a platoon formation on a highway. A fallback strategy is proposed that leads the faulty truck to park on the shoulder of the road and allows the rest of the platoon participants to continue their journey. To solve this problem, first, a functional platooning system should be designed. Therefore, a nonlinear bicycle dynamic model is employed, while a new Bidirectional (BD) Cooperative Adaptive Cruise Control (CACC) system is utilized for control purposes. The emergency escape manoeuvre has to be pre-computed and ready to be triggered when the failure occurs, as concerning defined specifications, limitations and constraints. It is generated using a quintic splines methodology, while a new optimization approach regarding the minimization of jerk peaks is adopted, enhancing the efficiency of the design procedure. Furthermore, a gap-closing controller is employed and tuned accordingly to reform the platoon after the faulty truck abandons the formation. Moreover, a suitable decision logic is defined to achieve smooth transition among regular performance and fallback state at both platoon and inter-vehicle level. The functionality of each component is firstly evaluated individually, based on specific performance metrics. Finally, all the mentioned components are put together and the fallback strategy that executes emergency escape manoeuvre in platoon context is derived. Several simulation tests illustrate proof of principle for the proposed framework. It is shown that the proposed strategy indeed achieves minimal risk condition for the faulty truck achieving minimal tracking errors. A global applied strategy is adopted for the gap-closing controller by making healthy follower(s) travel with the maximum possible acceleration. At the same time, the leading truck of the formation maintains a constant speed until the time gap between them becomes $0.8s$, before the switch back to the CACC, to complete this action as fast as possible and safety issues in the driving performance. Additionally, the CACC system is evaluated to ensure that the string stability criterion is satisfied in the mode of operation. Moreover, a virtual leader mechanism is introduced to fill in faulty truck's blind spot in the road that arise from the sensor failure. It is shown that it can provide a sufficient window of movement for the platoon before switching to the fallback strategy.