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Autotuning of a new PI-PD Smith predictor based on time domain specifications
(Elsevier Science Inc, 2003) Kaya, I
The paper extends a recent work on a modified PI-PD Smith predictor, which leads to significant improvements in the control of processes with large time constants or an integrator or unstable plant transfer functions plus long dead time for reference inputs and disturbance rejections. Processes with high orders or long time delays are modeled with low er order plant transfer functions with longer time delays. The PI-PD controller is designed so that the delay-free part of the system output will follow the response of a first-order plant or second-order plant, where it is appropriate, assuming a perfect matching between, the actual plant and model in both the dynamics and time delay. The provided simple tuning formulas have, physically meaningful parameters. Plant model transfer functions and controller settings are identified based on exact analysis from a single relay feedback test using the peak amplitude and frequency of the process output. Examples are given to illustrate the simplicity and superiority of the proposed method compared with some existing ones. (C) 2003 ISA-The Instrumentation, Systems, and Automation Society.
Computation of stabilizing PI and PID controllers
(Ieee, 2003) Tan, N; Kaya, I; Atherton, DP
In this paper, a simple method for the calculation of stabilizing PI controllers is given. The proposed method is based on plotting the stability boundary locus in the (k(p),k(i))-plane and then computing stabilizing values of the parameters of a PI controller. The technique presented does not require sweeping over the parameters and also does not need linear programming to solve a set of inequalities. Thus it offers several important advantages over existing results obtained in this direction. Beyond stabilization, the method is used to shift all poles to a shifted half plane that guarantees a specified settling time of response. Furthermore, computation of stabilizing PI controllers which achieve user specified gain and phase margins is studied. It is also shown via an example that the stabilizing region in the (k(p), k(i)) -plane is not always a convex set. The proposed method is also used to design PID controllers. The limiting values of a PID controller which stabilize a given system are obtained in the (k(p), k(i)) -plane, (k(p), k(d)) -plane and (k(i), k(d))-plane. Examples are given to show the benefit of the method presented.
Controller design for integrating processes using user-specified gain and phase margin specifications and two degree-of-freedom IMC structure
(Ieee, 2003) Kaya, I
In real industrial practice, controller designs are usually performed based on an approximate model. Furthermore, the parameters of the physical systems can vary with operating conditions and time. Therefore, it is essential to design a control system which will show a robust performance in the case of aforementioned situations. Gain and phase margins are well known measures for maintaining the robustness of a control system. In the literature, there are many publications considering controller designs for stable processes based on gain and phase margins specifications. However, for integrating processes, controller designs with user-specified gain and phase margins are very rare. This paper presents a new two degree-of-freedom Internal Model Control (IMC) structure and simple tuning rules to tune/design PD controllers for integrating processes with a small dead time to meet specified gain and phase margins. Simulation examples are given to illustrate that the proposed design method can give better closed loop system performances than existing design methods which is also designed based on user-specified gain and phase margins.
Exact parameter estimation from relay autotuning under static load disturbances
(Ieee, 2001) Kaya, I; Atherton, DP
Obtaining the parameters for PID controllers based on limit cycle information from the process in a relay controlled feedback loop has become an accepted practical procedure. If the form of the plant transfer function is known, exact expressions for the limit cycle frequency and amplitude can be derived in terms of the plant parameters, so that their measurements, assumed error free, can be used to calculate the parameter values. In the literature to date the solutions have only been considered for odd symmetrical limit cycles which will not be the situation when constant disturbances exist. Use of these expressions will lead to errors when the limit cycle is not odd symmetrical. This paper reports on exact parameter estimation for stable and unstable FOPDT or SOPDT plant transfer functions from relay autotuning under static load disturbances where the limit cycles are asymmetrical.
IMC based automatic tuning method for PID controllers in a Smith predictor configuration
(Pergamon-Elsevier Science Ltd, 2004) Kaya, I
In this paper, a new approach is presented based on relay autotuning of a plant to find parameters for its control using a Smith predictor. A Smith predictor configuration is represented as its equivalent internal model controller (IMC) which provides the parameters of the proportional-integral (PI) or proportional-integral-derivative (PID) controller to be defined in terms of the desired closed-loop time constant, which can be adjusted by the operator, and the parameters of the process model. This means that only one parameter, namely the desired closed-loop time constant, is left for tuning, assuming that the model parameters have been obtained from a relay autotuning. The ISE criterion was used to find the filter parameter, and simple equations were obtained to tune the Smith predictor. The method is very simple and has given improved results when compared with some previous approaches. (C) 2003 Elsevier Ltd. All rights reserved.
Improving performance using cascade control and a Smith predictor
(Elsevier Science Inc, 2001) Kaya, I
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, is investigated. The method can be used in temperature control problems where the secondary part of the process (the inner loop) may have a negligible delay while the primary loop (the outer loop) has a time-delay. Two different approaches, including an autotuning method, to find the controller parameters are proposed. It is shown by some examples that the proposed structure as expected can provide better performance than conventional cascade control, a Smith predictor scheme or single feedback control system. (C) 2001 Elsevier Science Ltd. All rights reserved.
A new Smith predictor and controller for control of processes with long dead time
(Elsevier Science Inc, 2003) Kaya, I
Good control of processes. With long dead time is often achieved using a Smith predictor configuration. Typically a PI or PID controller is used; however, it is shown in this paper that for some situations improved set point and disturbance responses can be obtained if a PI-PD controller is Used. Several methods are possible for selecting the parameters of the PI-PD controller but when the plant transfer function has no zeros, the use of the standard forms provides a simple algebraic approach, and also reveals why difficulties may be encountered if a PID controller is used. Some examples are given to show the value of the approach presented. (C) 2003 ISA-The Instrumentation, Systems, and Automation. Society.
Obtaining controller parameters for a new PI-PD Smith predictor using autotuning
(Elsevier Sci Ltd, 2003) Kaya, I
The paper extends a recent work on a modified PI-PD Smith predictor, which leads to significant improvements in the control of processes with large time constants or an integrator or unstable plant transfer functions plus long dead-time for reference inputs and disturbance rejections. Processes with high orders or long time delays are modelled with lower order plant transfer functions with longer time delays. The PI-PD controller is designed so that the delay free part of the system output will follow the response of a first order plant or second order plant, where it is appropriate, assuming a perfect matching between the actual plant and model in both the dynamics and time delay. The provided simple tuning formulae have physically meaningful parameters. Plant model transfer functions and controller settings are identified based on exact analysis from a single relay feedback test using the peak amplitude and frequency of the process output. Examples are given to illustrate the simplicity and superiority of the proposed method compared with some existing ones. (C) 2003 Elsevier Science Ltd. All rights reserved.
A PI-PD controller design for control of unstable and integrating processes
(Elsevier Science Inc, 2003) Kaya, I
A model-based PI-PD controller, design, where the PD feedback is used to change the poles of the plant transfer function to more desirable locations for control by a PI controller, is proposed. Several procedures for obtaining the parameters of the PI-PD controller are possible but one of the simplest approaches, which is used in this paper, is to employ integral squared time error standard forms as this enables the design to be completed using simple algebra. Also, an exact method for model extraction of some integrating processes which may or may not. have a time delay,is presented. The method is compared with several existing methods to control integrating processes and it is shown that the proposed method is superior to existing ones. (C) 2003 ISA-The Instrumentation, Systems, and Automation Society.
A refinement procedure for PID controllers
(Springer, 2006) Kaya, I; Tan, N; Atherton, DP
Proportional-Integral-Derivative (PID) controllers are still extensively used in industrial systems. In the literature, many publications can be found considering PID controller design for processes with resonances, integrators and unstable transfer functions. However, due to structural limitations of PID controllers, generally, a good closed-loop performance cannot be achieved with a PID, for controlling the aforementioned processes, and usually a step response with a high overshoot and oscillation is obtained. PI-PD controllers provide very satisfactory closed-loop performances in the case of controlling processes with resonances, integrators and unstable transfer functions. This paper introduces a simple approach to get parameters of a PI-PD controller from parameters of a PID controller so that a good closed-loop system performance can be realized. Extensive simulation examples are given to illustrate the value of the approach proposed.
A simple procedure for improving performance of PID controllers
(Ieee, 2003) Kaya, I; Tan, N; Atherton, DP
Proportional-Integral-Derivative (PID) controllers are still extensively used in industrial systems. In the literature, many publications can be found considering PID controller design for processes with resonances, integrators and unstable transfer functions However, due to structural limitations of PID controllers, good closed loop performance cannot be achieved with a PID controller for the aforementioned processes and usually a step response with a high overshoot and oscillation is obtained. The PI-PD controller has been shown to provide very satisfactory closed loop performance for controlling processes with resonances, integrators and unstable transfer functions. This paper introduces a simple approach to get parameters of a PI-PD controller from parameters of a PID controller so that a good closed loop system performance is obtained. Extensive simulation examples are given to illustrate the value of the approach proposed.
Tuning PI controllers for stable processes with specifications on gain and phase margins
(I S A-The Instrumentation Systems Automation Soc, 2004) Kaya, I
In industrial practice, controller designs are performed based on an approximate model of the actual process. It is essential to design a control system which will exhibit a robust performance because the physical systems can vary with operating conditions and time. Gain and phase margins are well known parameters for evaluating the robustness of a control system. This,paper presents a tuning algorithm to design and tune PI controllers for stable processes with a small dead time while meeting specified gain and phase margins. Simulation examples are given to demonstrate that the proposed design method can result, in a closed-loop system, in better performances than existing design methods which are also based on user-specified gain and phase margins. (C) 2004 ISA-The Instrumentation, Systems, and Automation Society.
Tuning smith predictors using simple formulas derived from optimal responses
(Amer Chemical Soc, 2001) Kaya, I
Good control of processes with long dead time is often achieved using a Smith predictor configuration. However, not much work has been carried out on obtaining simple tuning rules for a Smith predictor scheme. This paper develops optimal analytical tuning formulas for proportional-integral-derivative (PID) controllers in a Smith predictor configuration assuming perfect matching. Exact limit cycle analysis has been used to estimate the unknown parameters of a first-order plus dead time (FOPDT) or second-order plus dead time (SOPDT) plant transfer function. Simple analytical tuning rules based on these FOPDT and SOPDT are then derived which can be used to tune a PID controller in a Smith predictor scheme. Some examples are given to show the value of the approach presented.
Two-degree-of-freedom IMC structure and controller design for integrating processes based on gain and phase-margin specifications
(Inst Engineering Technology-Iet, 2004) Kaya, I
In industrial practice, controller designs are usually performed based on an approximate model. The parameters of the physical systems can vary with operating conditions and time. Therefore it is essential to design a control system that shows a robust performance in the case of the aforementioned situations. Gain and phase margins are well-known measures for maintaining the robustness of a control system. There are many publications considering controller designs for stable processes based on gain and phase-margin specifications. However, for integrating processes, controller designs with user-specified gain and phase margins are very rare. A new two-degree-of-freedom internal model control structure is presented with simple tuning rules to design and tune PD controllers for integrating processes with a dead time to meet specified gain and phase margins. Simulation examples illustrate that the proposed design method can give better closed-loop system performance than existing design methods based on user-specified gain and phase margins. Simulation results for an assumed perturbation in the process parameters are also given to illustrate the robustness of the proposed controller structure and design method.

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