Robust static output feedback synthesis for platoons under leader and predecessor feedback

Abstract

A multi-objective static output feedback synthesis problem is considered for the control of vehicle platoons under leader and predecessor feedback. Sufficient linear matrix inequality conditions are derived for the solvability of the problem in a way to facilitate static feed-forward as well. A novel velocity-dependent spacing policy is integrated into the control scheme together with a platoon model in which the emphasis on the predecessor information can be adjusted by a normalized scalar weight. It is shown that the string stability of the spacing errors and the acceleration signals can always be guaranteed by choosing this weight sufficiently small. Moreover, provided that the time headway is chosen sufficiently large, the synthesis can be performed in a way to avoid the amplification of acceleration energies if compared with the leader. As a particularly convenient feature, the target spacing between the vehicles becomes smaller when moving backward along the platoon. The total increase in the platoon length caused by the introduction of the velocity-dependent scheme is shown to be bounded and decreasing with decreasing predecessor weight. It is also established that the predecessor weight can be adjusted smoothly over time without endangering the formation stability. In addition to the optimization of the parameters of common fixed-structure controllers for general vehicle models, the proposed synthesis procedure provides various tools for improving robustness against measurement noise, communication delay, and model uncertainty.It is quite common to consider the platoon control problem based on linear vehicle models obtained by favor of exact feedback linearization [19][20][21][22]. The simplest one is a kinematic model referred to as the double integrator: acceleration (as the control input) to velocity, velocity to position. Because of the (typically uncertain) dynamics of the engine, it is necessary to consider slightly more advanced models in practical designs. The vehicle as a whole is hence usually viewed as a first-order system identified by a (possibly velocity-dependent) time constant referred to as the 'time lag ' [19, 23, 24]. This model is used to represent the transfer function from the given acceleration command to the actual acceleration of the vehicle. In more advanced models, a control input (i.e., actuator) delay is also assumed [5][6][7][25][26][27][28]. It is common to consider identical vehicle models with which the corresponding platoons are referred to as 'homogenous'. The analysis and synthesis problems get much more complicated for 'heterogenous' platoons in which the vehicles have different models [5,29]. For successful practical designs, one needs to take into account the uncertainty in the time lag and/or the actuator delay (as might be encountered in trucks due to switching dynamics with gear changes) in addition to heterogeneity [26].The main goal in a platoon formation is to maintain desirably small spacings between the vehicles by realizable acceleration/deceleration comman...

Heterogeneous string stability of unidirectionally interconnected MIMO LTI systems

“…Fig. 1 illustrates the model structure for the case of a leader and predecessor following (LPF) interconnection topology (Seiler et al, 2004;Köroglu and Falcone, 2017), where the maximum range of communication with direct predecessors is r = 1.…”

“…Typical LPF control structures in vehicle platooning (Seiler et al, 2004;Köroglu and Falcone, 2017) satisfy the conditions of the next theorem which provides sufficient conditions for HSS based on the following fact.…”

Platoon Control based on Predecessor and Delayed Leader Information via Minimized Headway Times

“…Although such a scheme has been proposed in [34], the headway policy suggested therein leads to a similar increase in the platoon length as in the case of predecessor following. On the other hand, the spacing policy proposed in [11] reduces inter-vehicle spacings backwards along the platoon.…”

“…In this paper, we consider the scheme of [11] in the face of delayed leader communication. The goal is to investigate the conditions for the formation and string stability of the platoon for a simple PD-type controller and thereby develop design guidelines.…”

An Adaptive Spacing Policy Guaranteeing String Stability in Multi-Brand <italic>Ad Hoc</italic> Platoons

“…When applying the LPF strategy in well organized, synchronized platoons it is presumed that p (t) are close to each other, and cannot be arbitrary functions [3], [22]. In ad hoc heterogeneous platoons we cannot build upon this assumption.…”