Modeling and analysis of human task-performing process in manufacturing systems with human task and error classifications

Development of a formal model for control and analysis of manufacturing systems in which a human operator is incorporated is difficult, nevertheless the human is a key component. It requires building a model of human functional specifications for executing various tasks. In this paper, a human parts handler is considered and the human task-performing process is described in terms of human tasks and errors. For this purpose, human tasks and errors are classified into two sets, respectively. Based on the number of locations where an operator is required to move to complete a task, tasks are divided into an on-the-spot task set and an around-the-system task set. For human errors associated with each of task set, a location error set and an orientation error set are defined, respectively. As the initial step toward building a controller for Human-involved Computer Integrated Manufacturing Systems (HiCIM), assessment of the impact of human involvement on the control of a system, much of which is controlled by a computerized execution system, is presented. The complexity of systems from the control perspective is modeled and analyzed with human tasks and errors. The human task-performing process is described using a flow chart format and a colored Petri net model is presented, and the complexity of process is analyzed in terms of human errors. A shop floor control example where the human operator performs material handling tasks is provided to illustrate the proposed methodology.