Setpoint Filter Research Articles

Control System Design for 3x3 Processes Based on Effective Transfer Function and Fractional Order Filter

Designing of PI/PID controller with fractional order set point filter is proposed to achieve the improved performance of 3x3 processes. But the design of controller for such higher dimensional multivariable processes is too difficult task because of interaction involved between the process variables. So interaction must be taken into design consideration. In this method of design determines the interaction between the variables using RGA and RNGA methods and uses it in converting the multivariable processes into multiple single loops. The interaction problems between the loops are overcome by incorporating the decouplers in the control loops. Then, the Effective Transfer Function (ETF) has obtained to design PI/PID controller for each individual element as in single input processes. The fractional order filter is also added to improve the servo response of the processes. Hence, the proposed system improves the overall performance by minimizing the interaction effects due to set point variations. This method is also validate by using a case study.

Control System Design for 3x3 Processes Based on Effective Transfer Function and Fractional Order Filter

Designing of PI/PID controller with fractional order set point filter is proposed to achieve the improved performance of 3x3 processes. But the design of controller for such higher dimensional multivariable processes is too difficult task because of interaction involved between the process variables. So interaction must be taken into design consideration. In this method of design determines the interaction between the variables using RGA and RNGA methods and uses it in converting the multivariable processes into multiple single loops. The interaction problems between the loops are overcome by incorporating the decouplers in the control loops. Then, the Effective Transfer Function (ETF) has obtained to design PI/PID controller for each individual element as in single input processes. The fractional order filter is also added to improve the servo response of the processes. Hence, the proposed system improves the overall performance by minimizing the interaction effects due to set point variations. This method is also validate by using a case study.

Practical disturbance rejection control for boiler-turbine unit with input constraints

With the increase of renewable sources participating into the power grid, the traditional thermal power generation is responsible for the frequent power regulation where the disturbance rejection ability should be enhanced during the operation. The boiler-turbine unit is a non-strictly proper multivariable plant with uncertainties, external disturbances and hard constraints, which make the conventional control strategy hard to meet the operating requirement. To this end, an advanced control strategy of generalized active disturbance rejection control (GADRC) is proposed in this paper, consisting of multivariable extended state observer (MESO) and anti-windup compensator. A simple transformation approach is proposed, which can convert the output disturbances involving the feedthrough item into the input lumped disturbances, so that their impact can be estimated by the MESO and compensated by the proposed GADRC. In addition to this, a setpoint filter is developed in the control structure to remove the tracking offset caused by the unknown disturbances and a novel anti-windup strategy is presented to handle the input saturation problem and alleviate the resulting fuel waste issue. The robust stabilities of the proposed GADRC including feedback control and anti-windup control are guaranteed using frequency domain method and Circle criterion, respectively. Simulation studies compared with other methods demonstrate the effectiveness of the proposed control strategy on the boiler-turbine unit, especially in complex cases of external disturbance and model-plant mismatches.

Design and Simulation of PI Controller with Two Degrees of Freedom

Aiming at the fully coupled problem of steady state and dynamic performance of a PI controller with one degree of freedom, two kinds of two DOF PI controllers were designed based on the setpoint filter structure and the setpoint feed-forward structure, and the design method of compensation link was introduced.On this basis, a variable structure two-degree-of-freedom PI controller was designed with reference to the idea of variable gain PI controller.Finally, the simulation results show that the controller can not only simplify the process of setting control parameters, but also take into account the steady-state performance, dynamic performance and anti-jamming performance of the system, and realize the function of output fast, no overshoot, no error tracking input signal changes.

A New Control Scheme for Integrating Processes with Inverse Response and Time Delay

Abstract This paper presents a novel technique in designing controller for integrating process with inverse response and time delay. Using Pade’s approximation, the positive zero is approximated to a negative zero by modifying the time delay of process. The polynomial approach is employed for the rearranged process to derive the controller parameters. The tuning parameter is selected based on the value of maximum sensitivity. Set point filtering is employed to reduce the overshoot in servo response. Various bench marking examples are considered to evaluate the proposed method. The evaluation is carried out in terms of various performances.

A Set-point Filter Type 2DOF Fractional Order PID Control System Design Scheme for Improved Disturbance Rejection Control

Many works have revealed that non-integer order dynamics is a better representation of real-world systems compared to integer order dynamics. Then, fractional-order modeling and control has become a major topic of control system researches during last two decades. To benefit contributions of fractional-order dynamics in controller response, fractional-order PID (FOPID) controllers have been considered as a substitute of conventional PID controllers and many study reported the control performance improvements provided by FOPIDs. Later, performance of closed loop FOPID control systems can be further improved by additional blocks. This study presents a 2DOF FOPID control system design scheme involving a set-point filter for improved disturbance rejection and set-point control performance. This design scheme performs tuning of a FOPID controller and a first order pre-filter function as a set-point filter. Here, the pre-filter function is employed to deal with a design tradeoff appearing between disturbance rejection performance and step control performance. Coefficients of FOPID controller and the pre-filter are concurrently adjusted by a modified random search algorithm to find out an optimal set-point filter type 2DOF FOPID design that can provide an improved step performance with a higher disturbance rejection. Illustrative examples are presented to demonstrate results of the proposed metaheuristic design schema.

Novel proportional–integral–derivative controller with second order filter for integrating processes

AbstractMany chemical and nonchemical processes exhibit integrating behavior. This paper presents new approach for deriving parameters of proportional–integral–derivative controller for various types of integrating processes. In order to obtain enhanced performance, the controller is augmented by a second order filter. In the process of deriving controller and filter parameters, time delay is approximated by second order Laguerre shift. Analytical tuning rules are derived on the basis of the sensitivity of loop transfer function. With the help of polynomial method, the poles are placed so as to minimize the overshoot in the servo response. A set point filter is also employed to mitigate the overshoot and settling time in servo response. Besides, the set point filter is able to decouple servo and regulatory responses. The proposed method is compared with recently proposed methods. The evaluation is carried out in terms of various performance indices. Investigation of evaluation results reveals that the proposed method offers considerable improvement over the existing methods.

Synthesis of PI Controller with a Simple Set-Point Filter for Unstable First-Order Time Delay Processes and Integral plus Time Delay Plant

The paper describes PI controllers tuning for unstable first order time delay processes and integral plus time delay plant. The suggested method for designing a PI controller is based on the pole assignment method. Conditions for selecting the PI controller parameters in the function of the desired poles and parameters of the plant are met by using the features of the Lambert W function. The system stability in feedback is guaranteed by selecting the desired poles of the pre-defined range. The determined scope for pole selection includes the condition that this controller operates without integral gain, merely as proportional. The overshoot is reduced by using the simple first-order set-point filter. The manner of selecting the initial matrix which is used in a LambertW_DDE toolbox has been proposed. The illustrations of the simulation have been provided. Performances of the system regulated with a suggested PI controller are compared with the results received from other methods wherefrom it may be seen that this method yields better results in terms of the system settling time, rise time and IAE, ISE for set-point and good results in term of IAE, ISE for load disturbance and for the robustness on the uncertain changes expressed by the process parameter change of 10 %.DOI: http://dx.doi.org/10.5755/j01.eie.24.2.20629

Optimal tuning rules for PI/PID controllers for inverse response processes

In this work, optimal tuning rules for PI/PID controllers for stable and integrating first-order inverse response processes are reported. Integral performance criteria (ISTE, IST 2E and IST 3E) have been minimized using Particle Swarm Optimization (PSO), an evolutionary optimization technique, to get optimal controller parameters. For integrating process model, set-point filter is used for reducing large overshoot. For nominal conditions, simulation results show significant improvement in both servo and regulatory performances. The optimal controllers also give good robust control performances during model-mismatch conditions.

Identification and PID tuning techniques for stable and unstable SOPDT processes

In this paper, identification and control of a process whose dynamics can be described by a second-order-plus-dead-time (SOPDT) stable/unstable model is presented. Using the state-space approach and limit cycle information, analytical expressions are derived to identify the process dynamics. The wavelet decomposition is performed to recover a noise-free limit cycle output which is generally contaminated by measurement noise. The proportional–integral–derivative controller connected in the feedback loop is designed primarily to get good load disturbance rejection for the identified process. Reference tracking is achieved with the help of a set-point filter. The direct synthesis method with single tuning parameter is used to tune the controller parameters. The best value of the tuning parameter is selected using the particle swarm optimization algorithm in such a way that a good performance measure of the closed-loop system is achieved.

A 2-Dof LQR based PID controller for integrating processes considering robustness/performance tradeoff

This paper focuses on the analytical design of a Proportional Integral and Derivative (PID) controller together with a unique set point filter that makes the overall Two-Degree of-Freedom (2-Dof) control system for integrating processes with time delay. The PID controller tuning is based on the Linear Quadratic Regulator (LQR) using dominant pole placement approach to obtain good regulatory response. The set point filter is designed with the calculated PID parameters and using a single filter time constant (λ) to precisely control the servo response. The effectiveness of the proposed methodology is demonstrated through a series of illustrative examples using real industrial integrated process models. The whole range of PID parameters is obtained for each case in a tradeoff between the robustness of the closed loop system measured in terms of Maximum Sensitivity (Ms) and the load disturbance measured in terms of Integral of Absolute Errors (IAE). Results show improved closed loop response in terms of regulatory and servo responses with less control efforts when compared with the latest PID tuning methods of integrating systems.

Set-point filter design for a two-degree-of-freedom fractional control system

This paper focuses on a new approach to design U+0028 possibly fractional U+0029 set-point filters for fractional control systems. After designing a smooth and monotonic desired output signal, the necessary command signal is obtained via fractional input-output inversion. Then, a set-point filter is determined based on the synthesized command signal. The filter is computed by minimizing the 2-norm of the difference between the command signal and the filter step response. The proposed methodology allows the designer to synthesize both integer and fractional set-point filters. The pros and cons of both solutions are discussed in details. This approach is suitable for the design of two degree-of-freedom controllers capable to make the set-point tracking performance almost independent from the feedback part of the controller. Simulation results show the effectiveness of the proposed methodology.

Design Of Pid Controller With Compensator Using Direct Synthesis Method For Unstable System

In industrial processes, unstable system produces undesirable peak overshoot. So, PID controller with compensator and set point filter is designed using direct synthesis method. The set point filter reduces the peak overshoot. PID controller with compensator improves the overall response of the system. In this method, the characteristics equation of the system with PID controller and a compensator is compared with a desired characteristics equation. A single tuning parameter is used to find controller parameters, compensator and set point filter.

Tuning of IMC based PID controllers for integrating systems with time delay

Design of Proportional Integral and Derivative (PID) controllers based on IMC principles for various types of integrating systems with time delay is proposed. PID parameters are given in terms of process model parameters and a tuning parameter. The tuning parameter is IMC filter time constant. In the present work, the IMC filter (Q) is chosen in such a manner that the order of the denominator of IMC controller is one less than the order of the numerator. The IMC filter time constant (λ) is tuned in such a way that a good compromise is made between performance and robustness for both servo and regulatory problems. To improve servo response of the controller a set point filter is designed such that the closed loop response is similar to that of first order plus time delay system. The proposed controller design method is applied to various transfer function models and to the non-linear model equations of jacketed CSTR to demonstrate its applicability and effectiveness. The performance of the proposed controller is compared with the recently reported methods in terms of IAE and ITAE. The smooth functioning of the controller is determined in terms of total variation and compared with recently reported methods. Simulation studies are carried out on various integrating systems with time delay to show the effectiveness and superiority of the proposed controllers.

Robust Design of PID Controller Using IMC Technique for Integrating Process Based on Maximum Sensitivity

The aim of this work was to obtain a design for the proportional integral derivative controller in series with a second-order lead/lag filter for pure integrating process with time delay based on internal model control principle to achieve efficient disturbance rejection and robustness. A setpoint filter is introduced to reduce the overshoot in the setpoint response. Further, the robustness of the controller is examined by incorporating perturbations in the time delay parameter for model mismatch. The proposed method demonstrated good disturbance rejection and robustness in comparison with recently developed methods with the controller tuned to have same robustness rank with the calculation of the peak of maximum sensitivity $$(M_S )$$ .

Linear Active Disturbance Rejection Control: Analysis and Tuning via IMC

Linear active disturbance-rejection control (LADRC) is investigated in this paper. First, it is shown that LADRC structure can be changed to a two-degree-of-freedom (TDF) internal model control (IMC) structure, where the nominal model for the IMC design is simply a multiple integral plant, so analysis of LADRC can be done via the IMC framework. Then it is shown that the widely adopted bandwidth-tuning method for LADRC is equivalent to tuning the two time constants of the setpoint filter and the disturbance-rejection filter in IMC. Finally, to improve the control performance of an LADRC, a general method is proposed to incorporate extra dynamics of the controlled plant in LADRC.

Simple Analytic Proportional-Integral-Derivative (PID) Controller Tuning Rules for Unstable Processes

Very simple proportional-integral-derivative (PID) controller tuning rules for a wide range of stable processes are available. However, for unstable processes, the design trend is for controllers to be more complex for better performances. Here, the design concept of “simplicity” is extended to unstable processes. Simple desired closed-loop transfer functions for the direct synthesis method and simple approximations of the process time delay are utilized for unstable processes. Very simple tuning rules for PID controllers and set-point filters are obtained, yielding similar or even improved performances over previous more complicated PID controller tuning methods.

Simple Analytic PID Controller Tuning Rules Revisited

The SIMC method by Skogestad (J. Process Control 2003, 13, 291–309) to tune the PID controller is revisited, and a new method (K-SIMC) is proposed. The proposed K-SIMC method includes modifications of model reduction techniques and suggestions of new tuning rules and set point filters. Effects of such modifications are illustrated through simulations for a wide variety of process models. The proposed modifications permit the SIMC method to be applied with more confidence.

Enhanced cascade control for a class of integrating processes with time delay

Unlike self-regulating processes, cascade control strategies for control of integrating processes with time delay are limited. A novel series cascade control structure to enhance the closed loop performance is proposed for integrating and time delay processes. The proposed controller structure has only two controllers and a setpoint filter. The inner loop controller is designed based on IMC approach and the primary setpoint filter is based on optimal performance index. The primary load disturbance rejection controller, a PID controller in series with a lead/lag compensator, is designed on the basis of the desired closed-loop complementary sensitivity function. The robustness analysis is carried out using Kharitonov's theorem. Simulation results demonstrate the efficacy of the proposed method by showing satisfactory nominal and robust performances.

Cascade control based on minimum sensitivity in outer loop for processes with time delay

A new cascade control program was proposed based on modified internal model control to handle stable, unstable and integrating processes with time delay. The program had totally four controllers of which the secondary loop had two controllers and the primary loop had two controllers. The two secondary loop controllers were designed using IMC technique. They were decoupled completely and could be adjusted independently, which avoided the undesirable influence on performance of the primary controllers. The main controller in the primary loop was devised as a PID using the method of minimum sensitivity, which could guarantee not only the nominal performance but also the robust stability of the system. A setpoint filter was added in the primary loop to improve the tracking performance. All the controllers of the two closed-loops were designed analytically, and could be adjusted and optimized by single parameter respectively. Simulations were carried out on three various processes with time delay, and the results show that the proposed method can provide a better performance of both set-point tracking and disturbance rejection and robustness against parameters perturbation.