Abstract: While it is widely recognized that total quality is a cost problem for production systems, it is less well recognized that alarm system efficiency is also an important cost problem. Practically, a well-designed alarm system is an essential tool in to maintain effective plant operations. Poorly designed alarm systems cause unnecessary disturbances, a waste [...]
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Design PID controllers for desired time-domain or frequency-domain response
Abstract: Practical requirements on the design of control systems, especially process control systems, are usually specified in terms of time-domain response, such as overshoot and rise time, or frequency-domain response, such as resonance peak and stability margin. Although numerous methods have been developed for the design of the proportional-integral-derivative (PID) controller, little work has been [...]
Robust PID controller design for non-minimum phase time delay systems
Abstract: A robust PID controller for a non-minimum phase system subject to uncertain delay time is presented in this paper. Utilizing the gain-phase margin tester method, a specification-oriented parameter region in the parameter plane that characterizes all admissible controller coefficient sets can be obtained. The PID controller gains are then directly selected from the parameter [...]
Analytical design and analysis of mismatched Smith predictor
Abstract: In this paper, an analytical design method is developed for the mismatched Smith predictor on the basis of the internal model control (IMC) method. Design formulas are given and design procedure is significantly simplified. One important merit of the proposed method is that the response of the closed loop system can be easily adjusted. [...]
Improving performance using cascade control and a Smith predictor
Abstract: Many investigations have been done on tuning proportional-integral-derivative (PID) controllers in single-input single-output (SISO) systems. However, only a few investigations have been carried out on tuning PID controllers in cascade control systems. In this paper, a new approach, namely the use of a Smith predictor in the outer loop of a cascade control system, [...]
Guide lines for the tuning and the evaluation of decentralized and decoupling controllers for processes with recirculation
Abstract: This paper gives guidelines for the pairing, the time response specification, and the tuning for processes with recirculation when decentralized controllers are used. This selection is based on the condition number, which is an indicator of the process directionality, and on the generalized dynamic relative gain (GDRG), which is a measure of the interaction. [...]
Robust PID Tuning Strategy for Uncertain Plants Based on the Kharitonov Theorem
Abstract: In this paper, the Kharitonov theorem for interval plants is exploited for the purpose of synthesizing a stabilizing controller. The aim here is to develop a controller to simultaneously stabilize the four Kharitonov-defined vortex polynomials. Different from the prevailing works, the controller is designed systematically and graphically through the search of a non-conservative Kharitonov region [...]
PID gain scheduling using fuzzy logic
Abstract: A simple, yet robust and stable alternative to proportional, integral, derivative (PID) gain scheduling is developed using fuzzy logic. This fuzzy gain scheduling allows simple online duplication of PID control and the online improvement of PID control performance. The method is demonstrated with a physical model where PID control performance is improved to levels [...]
A Little about Valves
What is Cv ? If you are a mechanic, you would probably say that it is the joints that are on a front wheel drive vehicle, however if you work in the field of process automation you might know that it pertains to control valves. Cv is the capacity of a control valve, or the [...]
Instrumentation and Control Systems Documentation: Two generations of knowledge
When you read a book, do you ever consider the years of knowledge that lie behind the words? Collectively, the co-authors of Instrumentation and Control Systems Documentation, Second Edition bring 80-plus years’ worth of experience to each page. What’s even more unique is they are father and son. A dedicated ISA member for more than [...]