In this chapter, we develop the controller of another complete example: a mechanical press. The intention is to show how this can be done in a systematic fashion in order to obtain the correct final code. In Section 1, we present an informal description of this system. In Section 2, we develop two general patterns that we shall subsequently use. The development of these patterns will be made by using the proofs as a mean of discovering the invariants and the guards of the events. In Section 3, we define the requirement document in a more precise fashion by using the terminology developed in the definition of the patterns. The main development of the mechanical press will take place in further sections where more design patterns will be presented.

Informal description

Basic equipment

A mechanical press is essentially made of the following pieces of equipment:

• a vertical slide, which is either stopped or moving up and down very rapidly;

• an electrical rotating motor, which can be stopped or working;

• a connecting rod, which transmits the movement of the electrical motor to that of the slide;

• a clutch, which allows to engage or disengage the motor on the connecting rod.

This is illustrated in Fig. 3.1.

Basic commands and buttons

The following commands can be performed by means of buttons named respectively B1, B2, B3, and B4.