  This paper investigates the flocking control of a swarm with a malicious
agent that falsifies its controller parameters to cause collision, division,
and escape of agents in the swarm. A novel geometric flocking condition is
established by designing the configuration of the malicious agent and its
neighbors, under which we propose a hierarchal geometric configuration-based
flocking control method. To help detect the malicious agent, a parameter
estimate mechanism is also provided. The proposed method can achieve the
flocking control goal and meanwhile contain the malicious agent in the swarm
without removing it. Experimental result shows the effectiveness of the
theoretical result.
