Switched Dynamic Event-Triggered Control for String Stability of Nonhomogeneous Vehicle Platoons With Uncertainty Compensation

This paper investigates the cooperative adaptive cruise control (CACC) of intelligent and connected vehicles under event-triggered communication and modeling uncertainties. These uncertainties in the vehicular platoon can challenge the well-known homogeneity and linearity assumptions of the CACC. To address this issue, we propose a disturbance observer (DOB) to estimate both the parametric uncertainty and the unmeasured external signals. The DOB-based disturbance estimate is directly incorporated into the feedback linearization control law for uncertainty compensation. To assess the individual stability of each vehicle and the string stability of the nonhomogeneous platoon, we formulate overlapping dynamics that model the interconnection of only those vehicles directly exchanging information. This formulation of overlapping dynamics also facilitates the scalability of the platoon, i.e., we can conveniently increase the number of vehicles in the platoon without compromising the complexity of the stability analysis. Using a suitable Lyapunov-Krasovskii functional and the null-term relaxation technique, we derive sufficient conditions to design a switched dynamic event-triggered controller (ETC) that ensures both individual stability and string stability. With the proposed switching ETC approach, the event-triggering condition is only evaluated after a predefined constant period, ensuring a lower bound between events to avoid Zeno behavior. Extended from the $\mathcal {L}_{2}$-stability concept to explicitly account for the uncertainty effects of the nonhomogeneous platoon, the ETC design conditions are formulated as a convex optimization problem under linear matrix inequalities to maximize the inter-event time. The effectiveness of the proposed ETC approach is validated through extensive simulations and comparisons using an uncertain CACC setup.