Implementation of Virtual Feedback Control of Industrial Processes via Soft Sensing Technique
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Hardware sensor devices are used for state measurements in many process industries but due to various disturbances and aging effect it causes inaccuracies in measurement. Hence, soft sensing technique is employed. Soft sensing is the method of determining constants and variables of any system according to the performance level based on the measurement from a process. In real-time all process variables cannot be tapped directly. Controlling of those variables are also tedious in nature. Further, by using simple feedback mechanism it cannot be controlled. Hence, there arises need for estimating the unmeasured state using suitable soft sensing techniques. The estimated values can be used as a feedback signal to the external PID controller. This leads to the design of virtual feedback control. In the feedback path, a hardware sensor is replaced with soft sensing technique namely an extended Kalman filter (EKF). But the main drawback of using conventional PID controllers in industries are both servo tracking and disturbance rejection cannot be achieved at the same time. Thus, enhanced PID (EPID) controllers are used to overcome the above demerit. The EPID controller has the capability to instantaneously track the set point variations and reject the disturbances simultaneously. The comparative performance analysis of both conventional PID and EPID integrated with EKF has done in simulated continuous stirred tank reactor non-linear process. The effectiveness of virtual feedback control using EPID has been demonstrated in the real-time level process.
KeywordsCSTR EKF EPID PID Soft sensing Virtual feedback control
This Research work was financially supported by the UGC Major Research Project scheme under the title Investigations on the application of state estimation in CSTR control and Grant order no. F. 39-874/2010(SR) dated 12.01.2011.
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