The planning method adopted in the visual programming system for sequence-control program specification design (VIPS/S-SFCD) is described. VIPS/S-SFCD is based on two unique features: (1) an example-based programming technique in which designers specify the initial states and goal conditions of equipment blocks using visual representations; and (2) a planning method that infers machine actions and generates control program specifications. The planning method is based on a state-space model and uses scope to make the searches more efficient. To investigate the effectiveness of the method, VIPS/S-SFCD was used to experimentally generate control program specifications for an existing steel plant. The results showed that the quality of the control program specifications generated by the planner was equal to that achieved by a design specialist, and the time required for designing control programs was much shorter. Using VIPS/S-SFCD, errors in writing specifications are reduced because designers can easily understand the initial and goal state of an equipment block and the sequence of state transitions. The reliability of the specifications is improved because VIPS/S-SFCD generates valid segments of the specifications. The design time is also reduced because designers can use high-level instructions that closely reflect their thought processes.
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