Statechart Based Elevator Controller and Its Verification

For designing modern automation systems (event-driven complex reactive systems which continuously react to external stimuli) it is necessary to define guidelines, methods and tools that allow to carry out the designs within an overall development methodology that permits to specify these systems in an easy and safe way, to maintain traceability along the different phases of the design, and to have the needed knowledge about the behaviors of the defined system. Basic issues related to current specification technology have been discussed in the companion paper. The current paper describes the present status of our work in validating this methodology on the control of an elevator system. An elevator system is usually equipped with a fairly large number of sensors, making it a real-scale application, but simple enough to serve in demonstrating the basic principles involved with clarity. Entire system is designed using state charts and implemented in a programmable logic device. To demonstrate the feasibility a prototype system is simulated using micro controllers and the results are presented in the paper. However, in this implementation, statecharts are only used as formal specification of control which provides the basis for functional decomposition of the program into communicating finite state machines (FSM): port structures proposed in (S. Devapriya Dewasurendra, 2006) for reconfigurable implementation are not yet incorporated. Hence, the current paper discusses primary issues of modular controller implementation using statechart specifications. Verification has been done by simulating the controller on PIC 16F877 MC in Proteous 6 for selected operations. Formal verification methodology of the previous work will be validated in the next stage of this research