Engineering aspects of real-time systems and an experiment in hybrid control

An important application area for real-time computing is embedded systems where the computing system controls a mechanical, chemical etc. plant or device. The software requirements for such applications are derived from and depends on assumptions about the associated plant. A successful design for an overall system will therefore require close collaboration between control and software engineers. A prerequisite for such interaction is that the involved parties understand each others descriptions of the total system, and the theory of hybrid systems is an attempt to provide such a common language. To gain some insight we have developed a hybrid system, essentially a modular, mode switched control system for an experimental hydraulic manipulator platform. The requirements are specified in duration calculus, a real-time interval logic, and a design is developed and verified by calculations. The design uses a layered program architecture with communicating state machines. The design is implemented in occam on a transputer platform. A few experiments to validate the performance of the system have been conducted