I. Introduction

Cooperative behaviors have become an increasing active area of the research on multi-agent systems (MASs) [1]–[3]. However, formation control, where the agents converge to a desired geometric formation, is one of the most potential fields as its widespread applications in practice, such as mobile robot formation, autonomous satellites adjustment and unmanned aerial vehicles formation. Inspired by the theory and application of time-varying formation control mentioned in [3], a wide variety of researches on formation control can be found in [4]–[6]. Moreover, external disturbances exist in many practical scenarios. Therefore, designing an disturbance observer [7] is an effective method to reject external disturbances. Then, an observer-based formation control protocol was proposed in [8] to deal with unknown disturbances for Lipschitz nonlinear systems and the application of formation control with external disturbances was investigated in [9].