Thèse de doctorat en Ergonomie
Sous la direction de Yvon Quéinnec.
Soutenue en 1997
à Toulouse 2 .
Cette these repose sur l'analyse ergonomique du controle d'un processus chimique continu, en situation nominale. Elle repond a une demande sociale relevant, d'une part, de l'impact des technologies de traitement de l'information pour la conduite de process et d'autre part, des interrogations en matiere d'organisation du temps de travail. Dans ce contexte, la supervision peut donc etre caracterisee par la predominance des activites mentales et le recours au travail en equipes (travail poste). Du point de vue cognitif, elle consiste a anticiper l'evolution du systeme et a se tenir pret a agir a tout moment, en se referant a la representation de l'etat du systeme construite en debut de poste. Du point de vue chronopsychologique, certaines composantes de ces activites varient en fonction des horaires de travail. Notre but est de montrer que la supervision resulte de l'interaction entre les contraintes chronobiologiques et les exigences cognitives differentes lors de la prise de poste et de la surveillance. Les prises d'information, support de l'activite des controleurs en salle de controle, ont ete relevees en continu pendant 18 factions de 8 heures, de jour comme de nuit. L'analyse revele la specificite de la prise de poste au niveau quantitatif (pic prononce de consultations se prolongeant pendant au moins 90 mn) et qualitatif (recours privilegie a certains formats de page-ecran). Quant a la surveillance, variable en fonction du niveau de vigilance, elle repose sur une forte selection de l'information privilegiant les etapes critiques de la fabrication. Elle se partage aussi entre une anlayse globale et/ou detaillee de la situation. En bref, la supervision en situation nominale temoigne de l'interaction entre les contraintes cognitives de l'activite, les rythmes circadiens et la fatigue liee a la duree du poste. Nous en proposons un modele depassant la sinusoide classique des chronobiologistes trop restrictive pour rendre compte de toutes les variations observees.
Chronopsychological approach of shift takeover and supervisory activity in a dynamic continuous process
This thesis focused on the ergonomic analysis of supervisory activity in a continuous chemical process, on normal operation. It is based on a social request including the impact of new technologies in dynamic process control and assesments of working time. In such a context, the process supervision implies mental activities and shiftwork. From a cognitive viewpoint, it requires the anticipation of the system evolution and to be prepared to act constantly. This supposes to refer to a mental representation of the process, elaborated at the beginning of the shift. From a chronopsychological viewpoint, some components of these mental activities vary according to working hours. Our purpose is to understand the supervision organisation, and to show the interaction between chronobiological constraints and the different cognitive demands of shift takeover or supervisory activity. As essential supports of activity, controllers information gatherings were recorded on line, in the control room, over 18 night and day shifts. The results revealed the shift takeover specificity from quantitative (high rate of consultations carried on over the first 90 minutes) and qualitative viewpoints (variations in the proportions of the different screen pages format according to the shifts). During the supervisory activity (last five hours of work), the rate of information consulted varied according to the level of vigilance. They implied an important selection of information based on critical manufacture stages. They could also correspond to a global or/and a detailed analysis of the situation. To sum up, on normal operation, the supervision attested to the interaction between activity cognitive constraints, circadian rhythms and strain due to the shift duration. We then proposed a model exceeding the classical sinusoid of chronobiologists, too restricted to account for all the variations observed.