Acronym of Programmable Logic Controller. It is precisely in the programmable adjective that the luck of the PLC resides, its evolution, its enormous diffusion. Before the advent of the PLC, the design, construction, commissioning and maintenance of automation systems required more and more time, resources, space, depending on the increased needs of processes and applications.
It all starts in 1968 (but we are not talking about the student revolution). At the Westinghouse Conference, a General Motors Corporation engineer, Bill Stone, presents a document listing his company’s problems with the reliability and documentation of the factory’s machines. These specifications are delivered by General Motors, along with a request for quotation for the construction of a prototype, to four control system suppliers: Allen Bradley, Digital Equipment Corporation (DEC), Century Detroit, Bedford Associates. At the time of GM’s request, Bedford Associates engineers Richard (Dick) Morley, Mike Greenberg, Jonas Landau, George Schwenk and Tom Boissevain, were already working on the design of a machine, the features of which responded in part to GM’s requests. The Bedford team called this machine “084” (it was Bedford’s 84th design).
After finding the appropriate funding, the team forms a new company: Modicon (MOdular DIgital CONtroller ) which will work closely with Bedford to implement what GM requests. In 1969 Bedford Associates and Modicon presented their 084 system (also called PC, Programmable Controller) to GM and won the contract: the first PLC was born.
Control and supervision of process/automation with PLC and SCADA
The development of these software applications is performed with a rigorous and “object oriented” approach to obtain a modularity of functions , greater clarity in the interpretation of the code and its reusability.
The design consists of a sequence of well defined and precisely specified steps. At each step, specific met hods and techniques are applied, which can be based on a combination of theoretical aspects that derive from models of reality, empirical adaptations that take into account phenomena that have not been drawn from the model and practical rules that incorporate the results of past experiences.
The “mix” of these factors gives rise to a rigorous and systematic approach, the methodology, which can be applied continuously and consistently.To support the technician, « ASDG Automation Software Development Guide » by Teamgiga S.r.l . guides the technician himself in the process of creating the application and makes sure that everything is done in the expe cte d ways.