Graphical programming of control applications - General concepts and G language

A control application can be defined as a computer system that acquires data from sensors and issues commands to the physical process via actuators. Present in all industrial sectors, these applications require rapid, high-quality and reliable development. Usually based on low-level languages (assemblers) or classic languages (C, etc.), the programming of computer systems designed to control physical processes has been revolutionized by the arrival of simpler, more intuitive graphic languages, with more powerful libraries.

The engineers or technicians responsible for creating these applications generally have training or experience based more on the fields of automation or industrial computing than on programming. What's more, they frequently use graphical design methods based on block diagrams or the association of functional blocks, such as GRAFCET or the SA-RT analysis method. So a graphical programming language, based on data transfer between functional nodes, is perfectly suited to the working context of users in this area of control engineering. The G graphical programming language, used in the LabVIEW™ environment, has all these features: intuitive expression, graphical editing, data flow diagrams, high-quality development from a software engineering point of view... What's more, this language enables us to respond to increasingly wide-ranging applications using a large number of specific libraries: signal processing, automatic control, statistical processing, I/O board management software, local or industrial network management software, etc.

In this first dossier [S 8 205v2] , we focus on the various programming modes, and in particular on the G language introduced with LabVIEW software, and its interest in the development of control-command devices.

In the following dossier [S 8 206] , we focus on the use of LabVIEW software to manage data acquired or supplied in relation to physical processes.