On trajectory tracking of control-affine nonlinear systems with unreliable communication

We consider the problem of trajectory tracking for a control-affine nonlinear system, where the reference trajectory is given by a nonlinear dynamical system that accepts a time-varying exogenous input from an external agent through a communication channel. Owing to communication distortions, real-time information of the input signal is seldom available at the controller end. This necessitates appropriate design of the sending interval (the difference between time instants at which data packets are sent) for the external agent, and suitable update laws for the controller. We assume the availability of a control law, that achieves the desired trajectory tracking when the input signal is available in real-time, and outline some design guidelines such that the same control law can ensure boundedness of the tracking error even when the input signal is subjected to packet drops. In particular, we consider an appropriate model for the packet-drop probability of the channel and derive an upper bound on the sending interval. We also highlight the required conditions for update of the control signal. The idea is illustrated through numerical simulations conducted on a nonlinear model for cruise control with vehicle-to-vehicle communication.