Mode Switching Synthesis for Reachability Specifications

In many control applications, a specific set of output tracking controllers of satisfactory performance have already been designed and must be used. When such a collection of control modes is available, an important problem is to be able to accomplish a variety of high level tasks by appropriately switching between the low-level control modes. In this paper, we define a concept of control modes, and propose a framework for determining the sequence of control modes that will satisfy reachability tasks. Our framework exploits the structure of output tracking controllers in order to extract a finite graph where the mode switching problem can be efficiently solved, and then implement it using the continuous controllers. Our approach is illustrated on a helicopter example, where we determine the mode switching logic that achieves the high-altitude takeoff task from a hover mode.