Ergonomics Human-machine systems

The man-machine system is the basic concept of ergonomic theory (figure 1 ), and defines the object of ergonomic analysis. Defining the characteristics of the man-machine system is essential to work analysis:

• people and their physical, psychological, cognitive, socio-professional (level of qualification) and other characteristics;

• the machine (material or immaterial) and its characteristics in terms of interface, operating modes, level of automation, reliability, etc.

Other essential and/or contextual elements are also taken into account: work organization, various man-machine interaction media (procedures, interfaces, etc.), means of communication, etc.

Ergonomics, and more specifically work analysis, is concerned with the interrelationships and contextual interactions between the two components of the man-machine system. Operational documentation and procedures define the rules and modalities of interaction, and thus the framework for these interactions, and delimit their scope. For the ergonomist, these are prescriptions often drawn up by the methods department on the basis of the manufacturer's technical documentation. His aim is therefore to identify the results of applying these prescriptions in a fluctuating operational context (hazards, incidents, breakdowns, etc.), and to identify the operator's tactics and strategies for achieving production while managing all the hazards. The aim of the analysis is therefore to highlight this "real" work, which the ergonomist compares with the prescriptions: this is known as measuring the gap.