Automatic verification of wireless control in a mining ventilation system

We address a wireless networked control problem for a mine ventilation system. Ventilation control is essential for the control of the operation of a mine for safety and energy optimization. The main control objective is to guarantee safety of the closed loop system. This test-case is simple enough to be computationally tractable, and yet it exposes the main difficulties encountered when using wireless networked systems for safety-critical applications. The focus of this paper is the formal verification of the operation of a closed loop control system for the so called secondary ventilation system that ensures air flow in the chambers of the mine where extraction takes place. The secondary ventilation system is modeled conservatively in the sense that if the formal verification process provides a positive answer then the system is guaranteed to work correctly while the converse is not necessarily true. For control, we use a simple threshold scheme. The overall closed-loop system is described by a hybrid model that takes into account the effects of time-delay, transmission errors and allows the precise formulation of the safety constraints. To ensure that the formal verification process is computationally tractable, we reason in the framework of temporal logics, and apply abstraction techniques and model checking tools that we developed previously.