*Correspondence E_mail: alalinezhad@gmail.com Control Chart Recognition Patterns Using Fuzzy Rule-Based System 1 Associate Professor, Department of Industrial Engineering, Faculty of Industrial and Mechanical Engineering, Qazvin Branch, Islamic Azad University, Qazvin, Iran 2 Department of Industrial Engineering, Faculty of Industrial and Mechanical Engineering, Qazvin Branch, Islamic Azad University, Qazvin, Iran Alireza Alinezhad 1* and Ali Taherinezhad 2 Abstract Control Chart Patterns (CCPs) recognition is one the most important concepts in control chart application. Relating the patterns exhibited on the control chart to assignable causes is an ambiguous and vague task especially when multiple patterns co-exist. In this study, a fuzzy rule-based system is developed for X ̅ control charts to prioritize the control chart causes based on the accumulated evidence. To demon- strate the reasonable performance of the proposed fuzzy rule-based system, the case studies are performed and the results are analyzed. Received: 21 October 2020 Accepted: 18 December 2020 Keywords: Statistical Process Control (SPC), Control Chart Patterns (CCPs) recognition, Fuzzy system, Assignable cause variation Iranian Journal of Optimization Volume 12, Issue 2, 2020, 149-160 Research Paper Islamic Azad University Rasht Branch ISSN: 2588-5723 E-ISSN:2008-5427 Online version is available on: www.ijo.iaurasht.ac.ir Iranian Journal of Optimization, 12(2), 149-160, December 2020 149