I. Introduction
The platooning of autonomous vehicles has considerable potential for benefiting road traffic, including increased highway capacity, less fuel/energy consumption, and, hopefully, fewer accidents [1]. The process of platooning has been accelerated with increasing usage of wireless communication in road transportation [2]. Pioneering studies on platoon control can date back to 1990s [3], [4]. As pointed out by Hedrick and Tomizuka et al., the control topics of a platoon can be divided into two tasks: 1) to implement control of platoon formation, stabilization, and dissolution and 2) to carry out controls for throttle/brake actuators of each vehicle [5]. These naturally lead to a hierarchical control structure, including upper level control and lower level control [6]– [8], in which the upper level control retains safe and string stable operation, whereas lower level control tracks the desired acceleration by determining throttle/brake commands.