Abstract: Aiming at the problems of the controller performance degradation and the lack of accurate and efficient maintenance due to long-term and efficient operation for process industrial control systems with numerous loops, a controller performance assessment method of complex ratio control system is proposed for the benzene-ethylene ratio control system of the hydrocarbonization unit in a styrene plant. Firstly, a control structure of the benzene-ethylene ratio system with 1 main-4 pairs is constructed by analyzing the process mechanism. Secondly, the dynamic performance assessment for controllers of five single-loop systems is implemented based on the improved generalized minimum entropy benchmark using the sliding data window method. Then the following performance index is designed to assess the cooperative control performance between each loop of the system. After that, the combined performance index of the system is formulated. The weights of the combined performance index are determined by the Spearman correlation coefficient method, and the overall assessment of the controller performance for the benzene-ethylene ratio control system is realized. Finally, experimental studies demonstrate the effectiveness and feasibility of the proposed controller performance evaluation method, which can promptly detect suboptimal system states.

Key words: controller, performance assessment, benzene and ethylene ratio control, generalized minimum entropy