Documents to download :

• ASC: Control of an automatic parking gate (240 kB)

This simple example is used to present our approach. It concerns the control of an automatic gate for a car park. It is composed of:

• one gate with 2 off-on switches,
• one motor with 2 contactors,
• one receiver for the remote control,one sensor to detect cars.
  
  

The 4 inputs of the controller are:

• GC: Limit switch: Gate fully Closed,
• GO: Limit switch: Gate fully Open,
• Car: Sensor: Car detected,
• RG: Sensor: Remote Control actived.

The 2 Outputs of the controller are:

• Open: Control of the contactor used to open the gate,
• Close: Control of the contactor used to close the gate.
  
  

The expected behaviour of the control system with regard to the application requirements can be expressed by the set of assertions given hereafter. Among the 8 assertions, the first four ones (F1 to F4) are related to vivacity requirements (what must be done to perform the expected task), assertion S1 expresses a safety requirement. Assertions T1 to T3 express constraints coming from actuators features.

• F1: When the remote control is activated, the gate opens.
• F2: If the gate is not fully closed, the detection of a car brings about the opening of the gate.
• F3: The opening of the gate must be full: to stop the opening of the gate, it is necessary that the gate is fully open.
• F4: When the remote control is activated, the gate can not be control to close
• S1: To close the gate, it is necessary that no car is detected.
• T1: The gate must never be simultaneously controlled to open and to close.
• T2: When the gate is fully open, the gate must never be controlled to open.
• T3: When the gate is fully closed, the gate must never be controlled to close.
  
  

To avoid tedious symbolic calculus and to help the designer during the different steps of this synthesis method, a prototype software tool has been developed in Python. This tool performs all the computations required for inconsistencies detection and control laws generation, that enables the designer to focus only on application-related issues.

• The proposed document presents the case study: from requirements to Ladder Diagram