Abstract
Effective decision support system (DSS) design for the supervisory controller of a flexible manufacturing system (FMS) requires that functions be allocated between the human and computer subsystems in order to establish an effective human-computer cooperative arrangement. To better understand the nature of this arrangement for the tool-replacement decision function, a study was performed that investigated four different levels of decision-making responsibility between human and computer with respect to making tool-replacement decisions. The human interacted with a simulated FMS through an interface consisting of two screens. One screen provided menu information and the interactive dialogue and information support characteristics to the particular cooperative arrangement while the other screen displayed an ongoing graphical representation of the FMS. Twelve subjects performed the task under three computer-interactive conditions: manual decision making, manual decision making with decision support, and computer control with human override. Six of these subjects performed the task under conditions where the priorities of workparts changed at some point during the task. A computer control condition that was governed by a Bayesian decision policy served as the control condition. Subjects were required to minimize economic losses as specified by a loss function while maximizing part throughput.
The overall results indicated that, as compared to the other conditions, the manual decision making allocation policy was significantly more effective on both performance objectives under no priority change conditions and on the loss function measure when priority changes occurred. Based on various analyses, it was hypothesized that the more effective performance demonstrated under manual decision making conditions was due to the potential for this arrangement to promote better consideration of global as opposed to local information when making decisions.