Robotic systems have been extensively used, since the middle of the 20th century, in industrial environments for automated production lines. The idea of implementing complex cooperative behaviors has been recently gaining attention in the research community interested in multi-robot systems. This chapter defines an exosystem, whose state is exploited to generate a desired periodic setpoint for the multi-robot system. It introduces a methodology to define a control law that makes the dependent robots track a periodic setpoint. The chapter shows how to implement the control strategy in a decentralized manner. It also introduces a decentralized estimation methodology, which are exploited by each independent robot to compute an estimate of the complete output vector, and of the independent robot state. The chapter describes how to exploit the output estimation strategy introduced so far for the decentralized implementation of the Luenberger state observer.