Development of a Model Reference Adaptive Controller for String Stability in Truck Platooning

Abstract

This research developed a model reference adaptive controller for string stability in truck platooning. String stability is the ability of a platoon to maintain a stable formation as disturbances propagate through the string of vehicles resulting in oscillations or collisions. These disturbances include vehicle breakdown, intruding vehicles, change in speed or position. Designing an adaptive platoon controller that adapt to the disturbances and varying working conditions (such as road conditions and driving behaviours) while ensuring safety, stability, and efficiency has been explored in literature. This leads to the development of adaptive Proportional Integral Derivative (PID) Controller, Model Predictive Controller (MPC), sliding mode controller (SMC), and H-infinity (Hꝏ) controller for string stability of a platoon. However, the performance of these control schemes is affected by the model complexity and parameter uncertainty of the system resulting to an unstable system. In order to address these problems, a reference model of the trucks and adaptive mechanism is designed for error estimation and controller parameter adjustments respectively. A stabilizing controller was designed based on the concept of Lyapunov energy function. The performance of the controller is evaluated by comparing with that of MPC incorporated with PID controller using vehicle distance, vehicle velocity, inter vehicle gap error and velocity error as performance metrics. The simulation results obtained shows that MRAC has a better tracking performance and updates the controller in real-time there by attenuates disturbance when compared to DMPC- PID with an improvement in achieving a constant intervehicle gap of 20 ?, a desired speed of 20 ?/? at a settling time of 20 ???????. The simulation result shows a reduction in average intervehicle gap error of 0.15 ? from the leader vehicle to the follower vehicles. An average velocity error of 0.13 ?/? between the leader vehicle and followers. It also recorded an average acceleration of 0.73 ?/?2 and deceleration of 0.27 ?/?2 to achieve the desired steady state speed. The designed controller shows improvements over the existing control technique in terms of the intervehicle gap and system stability in the platoon.