# Simulation on Cooperative Changeover of Production Team Using Hybrid Modeling Method
## 4 Changeover Behavior of Operator Agents
### State Chart of Operator Agents  
The state chart is used to describe the autonomous and collaborative behavior of operator agents during the changeover process. The state chart of operator agents' changeover behavior according to the process of the changeover operation is shown in Figure 3. The figure shows that a changeover task can be divided into a parallel production phase and an interactive production phase. In the parallel production phase, \(s^{11}\) includes importing new programs or calling original programs, checking programs and checking the locating datum; \(s^{12}\) includes disassembling and cleaning the current fixtures, cleaning the installation deck and assembling new fixtures. In the interactive production phase, \(c^{1}\) includes debugging, inspecting and recording the results. It is assumed that the information transfer between agents is instantaneous in this model. The entry point of state chart is the \"waiting for tasks\" state. After receiving information of the issued tasks from publishers, the operator is transited to the \"response to the task\" state. The publishers of changeover tasks are managers, while the assisted changeover tasks are published by operators. If the operator master the skills required for the task, the \"Agree\" message will be fed back to the publisher from the operator, otherwise the feedback message is \"Reject\". Then the operator is transited to the \"waiting for tasks\" state. The publisher should make a judgment after all the feedback messages are collected. If there is more than one \"Agree\" feedback message, the task assignment will be completed according to the conflict coordination mechanism, and the \"task confirmation\" message will be sent to the selected operator; if all the feedback messages are \"Reject\", the type of the task will be judged next. If the task is a changeover task, it will be added to the task list by the manager; if the task is an assisted changeover task, the operator as the publisher will conduct the changeover operation directly and independently. The selected operator will get the task and move to a new state according to the task's type once the \"task confirmation\" message is received from the publisher. Taking the changeover task as an example, the operator will decide whether to launch cooperation with the operators in the \"waiting for tasks\" state according to the cooperative changeover strategy and production status information. (1) If the operator who has launched cooperation gets an assistant, then the operator as the initiator will begin to perform the subtask \(s^{11}\) and the operator as the assistant will get an assisted changeover task and begin to perform the subtask \(s^{12}\). Once both the subtasks have been completed, the two operators start to perform the subtask \(c^{1}\) together. As the whole task is completed, both the operators enter the \"complete the task\" state. (2) If the operator cannot get any assistant or there is no need to launch cooperation at all, the operator will begin to perform all the subtasks independently. As the task is completed, the operator enters the \"complete the task\" state. If there are any tasks in the task list that the operator masters the required skills, the operator will select a task according his or her preference. The operator in the \"complete the task\" state needs to check whether the current moment is in the off-work hours. (1) If \"No\", the operator will select a task from the task list according to his or  
Figure 3: State chart of operator agents’ changeover behavior. her skills and selection preference, and then submit the task application to the manager. (2) If \"Yes\", the operator will be transited to the \"being off duty\" state at first, and not to the \"select a task from the task list\" state until the simulation clock runs to work time. Whether the operator can get the task depends on the manager's feedback. (1) If \"Yes\", the operator is transited to a new state according to the task type.