## 1 Introduction  
Multi-agent robot research has been expanding due to the effectiveness, robustness, flexibility and operational efficiency involved in accomplishing tasks with many agents, compared to the use of a single agent [1]. The advantages of load-sharing, enable complex tasks to be simplified for agents, which has allowed cooperative multi-agent robot research to be more actively explored [2, 3, 4]. The multi-agent system is specifically designed to work in hazardous environments and in very limited spaces, which are impossible for humans to reach. Multi-agent systems have applications in medicine and nanotechnology [5]--magnetic [6] robots have been used to send medicine directly to human organs, planetary rovers have been used to accomplish missions on other planets [7, 8], inspection robots have been used to inspect and clean the pipelines in oil and gas industries [9, 10] and researchers have explored the use of unmanned aerial vehicles and swarm robot applications [11, 12, 13]. Due to the importance of these multi-agent systems in aiding human activities, various issues related to the cooperation and coordination of multi-agent systems have been researched and discussed up to the present day. The analysis and direction of cooperative multi-agent systems have been reviewed and discussed by several researchers [2; 14] to demonstrate the significance and impact of multi-agent coordination research. Several issues of multi-agent coordination and control, such as formation [15], consensus [16], containment [17], task allocation [18], path planning [19] and rendezvous [20], have been highlighted by previous researchers. Among them, consensus, which consists of an agreement between agents to reach a certain quality of interest, has attracted a large amount of research. Most of this consensus research has focused on positional consensus or velocity, applied either to homogeneous or heterogeneous agents. Consensus issues can also be categorized into leaderless consensus [16], leader-follower consensus [21], output consensus problems [22] or positional consensus [23]. In parallel with recent wireless network technologies, consensus research is in demand when there are various topology networks [1] that exist to present the connection between the agent and neighbors. The flow of information, which can either be directed or undirected, one-way or two-way, and distributed/one-to-one or centralized/broadcast, that represents the communication between multi-agent makes the consensus issue more challenging. Control and communication issues involved in obtaining an effective consensus system have also attracted the attention of many researchers. Finding a consensus for formation, tracking and rendezvous control applications is challenging for multi-agent systems. For formation, model predictive control has been proposed for a unmanned aerial vehicles (UAV), leader-following system [13] and vector field path planning has been designed for multiple decentralized UAVs without a leader [11]. In addition, the use of a novel state observer and sliding mode control for heterogeneous systems [24] and adaptive control laws for tracking between leader-follower systems [25] are examples of consensus controllers for tracking applications. Meanwhile, for consensus to a rendezvous point, which also known as positional consensus, the focus has been on the design of an effective consensus controller, which can be used in various applications. Models using linear programming with random perturbation [16], a constructed intermediate attitude system for unicycle-type vehicles [26] and distributed static and dynamic control [27], discrete-time double integrator control [28] and broadcast controllers [17] are among the proposed controllers. Additionally, some other researchers focus on the communication issue problem in relation to consensus and rendezvous. For instance, [PERSON] [29] developed a leader-follower robot by proposing an observer that was used to check the independent triggering of event-triggered (ET), whereas [PERSON] et al.