Documents to download :

• ASC: Control of a pumping system (239 kB)

Process to control
This simple example is used to present our approach. The studied system is the controller of a water distribution system composed of two pumps which are working in redundancy. The water distribution is made when it is necessary according to the possible failures of elements (the pumps and the distributing system).

Inputs and Ouputs of the controller

The 5 inputs of the controller are:

• Rq: Request of water,
• F1: Failure of Pump 1,
• F2: Failure of Pump 2,
• Gf: Global failure of the distribution system,
• Pr: Pump 1 has priority.

The 2 Outputs of the controller are:

• P1: Command of Pump 1,
• P2: Command of Pump 2.
  
  

Control system specifications

The expected behaviour of the control system with regard to the application requirements can be expressed by the set of assertions given hereafter

• The two pumps never operate simultaneously.
• A pump cannot operate if it is out of order.
• When a global failure is detected, no pump can operate.
• Pumps can operate only if a water distribution request is present.
• Pumps operate when it is possible.
  
• Priority is given according to `pr' (Pump1 has priority when `pr'is true).
• In order to reduce the wear of the pump, it is necessary to restrict the number of starting of the pumps.
  
  

Obtained results

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