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Cycle to Cycle Manufacturing Process Control

Research and Teaching Output of the MIT Community

Show simple item record Hardt, David E. Siu, Tsz-Sin 2003-12-23T15:05:53Z 2003-12-23T15:05:53Z 2002-01
dc.description.abstract Most manufacturing processes produce parts that can only be correctly measured after the process cycle has been completed. Even if in-process measurement and control is possible, it is often too expensive or complex to practically implement. In this paper, a simple control scheme based on output measurement and input change after each processing cycle is proposed. It is shown to reduce the process dynamics to a simple gain with a delay, and reduce the control problem to a SISO discrete time problem. The goal of the controller is to both reduce mean output errors and reduce their variance. In so doing the process capability (e.g. Cpk) can be increased without additional investment in control hardware or in-process sensors. This control system is analyzed for two types of disturbance processes: independent (uncorrelated) and dependent (correlated). For the former the closed-loop control increased the output variance, whereas for the latter it can decrease it significantly. In both cases, proper controller design can reduce the mean error to zero without introducing poor transient performance. These finding were demonstrated by implementing Cycle to Cycle (CtC) control on a simple bending process (uncorrelated disturbance) and on an injection molding process (correlated disturbance). The results followed closely those predicted by the analysis. en
dc.description.sponsorship Singapore-MIT Alliance (SMA) en
dc.format.extent 1111042 bytes
dc.format.mimetype application/pdf
dc.language.iso en_US
dc.relation.ispartofseries Innovation in Manufacturing Systems and Technology (IMST);
dc.subject manufacturing process control en
dc.subject SPC en
dc.subject discrete system control en
dc.subject variance reduction en
dc.title Cycle to Cycle Manufacturing Process Control en
dc.type Article en

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