Hybrid control systems using timed Petri nets: supervisory control design based on invariant properties

In this paper, a class of timed Petri nets named programmable timed Petri nets is used for supervisory control of hybrid systems. In particular, the transfer of the continuous state to a region of the state space under safety specifications on the discrete and continuous dynamics is addressed. The switching policy is embedded in the dynamics of the underlying Petri net structure and the supervisors are described by Petri nets. The discrete specifications are expressed in terms of linear constraints on the marking vector and are satisfied by applying supervisory control of Petri nets based on place invariants. The hybrid system switches from a subsystem to another, in a way that the state gradually progresses from one equilibrium to another towards the desired target equilibrium. The supervisory control algorithm is designed to allow switchings to occur only on the intersection of the invariant manifolds. Finally, in the case when the continuous dynamics are described by first order integrators, the design algorithm is formulated as a linear programming problem.