Showing 3 results for String Stability
H. Chehardoli, M.r. Homainezhad,
Volume 7, Issue 3 (9-2017)
Abstract
This paper studies the longitudinal control of a group of vehicles following a lead vehicle. A
neighbor based upper level controller is proposed by considering communication delay and
actuator lag. Constant spacing policy is used between successive vehicles. Two different
approaches based on Lyapunov-Razumikhin and Lyapuniv-Krassovski theorems are presented to
stability analysis of closed loop dynamic. By simulation studies, it will be shown that the second
approach is less conservatism than the first one. We consider the bidirectional leader following
(BDLF) topology for inter-vehicle communication. Based on this structure, some sufficient
conditions assuring string stability of platoon is derived. At the end of paper, four different
scenarios are presented to study the robustness of algorithm against communication delay,
actuator lag, disturbance, heterogeny and communication losses.
Dr Hossein Chehardoli, Dr Ali Ghasemi, Mr Mohammad Daneshyian,
Volume 10, Issue 4 (12-2020)
Abstract
A new safe optimal consensus procedure is presented to guarantee the asymptotic and string stability as well as crash avoidance of large-scale non-identical traffic flow. Since time delay is an inherent characteristic of physical actuators and sensors, measurement delay and lags are involved in the upper level control structure. A third-order linear model is employed to define the 1-D motion of each automated vehicle (AV) and the constant time headway plan is employed to regulate the inter-AV distance. It is assumed that the network structure is decentralized look ahead (DLA) and each AV has access to relative position and velocity regarding with the front AV. A linear control law is introduced for each AV and by performing the stability analysis in frequency domain, the necessary conditions guaranteeing string stability and crash avoidance for large-scale traffic flow are derived. Afterwards, to calculate the optimal control parameters guaranteeing the best performance, an objective function combining all mentioned conditions as well as maximum overshoot, settling time and stability margin is introduced. The genetic algorithm (GA) technique is employed to optimize the presented objective function and obtain the optimal control parameters. Various numerical results are proposed to demonstrate the efficiency of this method.
Dr Hossein Chehardoli,
Volume 11, Issue 3 (9-2021)
Abstract
This paper considers the asymptotic zero tracking error as well as string stability of large-scale automated vehicle convoys (LAVC). Both centralized and decentralized bi-directional network topologies are investigated. A double integrator dynamical equation is defined to describe the 1-D dynamics of automated vehicles (AV). A centralized / decentralized controller which employs the relative displacement and velocity compared with the backward and forward AVs is defined for all following AVs. Since the dynamical equation of LAVC is hard to be analyzed for internal stability, a PDE-based approach is introduced to decouple and reduce the closed-loop dynamical equation. According to this approach, we will be able to decouple the dynamical equation of all AVs individually based on the error dynamics. After simplifying the dynamical equation of LAVC, the conditions satisfying the internal stability of centralized and decentralized networks are obtained. After that, algebraic analyses in frequency domain will able us to find the constraints on control gains guaranteeing the string stability. Simulation and experimental results are available to describe the merits of this algorithm.
