A method for setpoint alarming using a normalized index. (March 2017)

• Record Type: Journal Article
• Authors: Salsbury, Timothy I.; Alcala, Carlos F.
• Is Part Of: Control engineering practice. Volume 60(2017)
• Page Start: 1
• Page End: 6
• Publication Date: 2017-03
• Subjects: Control performance -- PID control -- Statistical process control -- Normalized index -- Big data sets; Automatic control -- Periodicals; 629.89
• DOI: 10.1016/j.conengprac.2016.12.002
• Languages: English
• ISSNs: 0967-0661

Abstract

Abstract: This paper describes a normalized index for assessing the performance of PID control loops. The index was developed with a focus on ease of implementation by making use of features that are commonly found in modern control systems. Exponentially-weighted moving averages (EWMAs) or equivalent first-order infinite-impulse response (IIR) filters are found in many control system algorithm libraries and the index is developed using two EWMAs. Because the index is normalized, this paper shows how a single threshold can be derived from generic performance metrics thereby providing a solution to replace traditional setpoint alarming. Results are presented from evaluating the index using data gathered from several different loop types in a building heating, ventilating, and air-conditioning (HVAC) system.