Routing and scheduling field service operation by P-graph

Field service operation is a theoretically complex problem. Numerous tasks at various locations need to be assigned to service staff. Skills, capabilities, and the level of local knowledge have to be considered to estimate the time required to complete a task by a group of selected technicians. Multiple objectives involve cost, task priorities, and consumer satisfaction. The cost includes the salary of service staff for a whole route from departing to returning to the base location. The travel cost depends on the proper routing of the service staff and the effective collection of closely located tasks into a single route. Priorities of tasks are defined by a function of their deadlines. Consumer satisfaction is a function of the number of missed appointments. A two-level optimization model is introduced to solve large-scale field service operation problems. At the higher level, tasks are assigned to time intervals based on the capacity and availability of the service groups. Then at the lower level, assigned tasks are exactly scheduled and service routes planned by time-constrained process network synthesis (TCPNS). The execution of the different levels is performed iteratively until the overall work plan cannot be further improved.