Measurement optimization in optimal process control

Abstract

In connection with the direct digital control of industrial processes, the optimum timing of measurements has been studied in an effort to reduce the required number and the precision of the measurements. This paper gives the optimum timing for stable and unstable processes and discusses the influence of the cost function, measurement noises, and process disturbances on the measurement timing. The cost functions which are quadratic in the control and the terminal error, or steady state error, are evaluated by the use of the linear estimation theory and the stochastic optimization technique. The optimum timing of measurements for process control systems subject to external disturbances has almost uniform intervals when the optimization in the relatively long control interval are considered. This paper presents a compromise between the number and the precision of measurements for some specified control performance to minimize the total required information quantity.