Memory-based on-line tuning of PID controllers for nonlinear systems

DESIGN AND EXPERIMENTAL EVALUATION OF A DATA-DRIVEN PID CONTROLLER

In this paper, a new design scheme of performance-driven PID controllers whose PID parameters are adjusted based on a control performance criterion. Although a majority of studies have been focused on the derivation of the CPM index, the control parameter tuning method based on the CPM has been hardly studied. Conventional self-tuning controllers are tuned based on the variance of control errors and/or modeling errors. Few adaptive schemes use performance indice as tuning signals, which should be the main driving force in maintaining optimal operation, This paper develops a strategy for the tuning of an adaptive PID controller that is an approximation of a generalized minimum variance controller. The main driving signal for adaptive tuning is the degradation of the controller performance criterion. The effectiveness of the proposed method is numerically evaluated on two simulation examples.

Main aim of this research is to develop a robust controller for an inverted pendulum system. Performance of classical PID controller is found to be effective in this regard. However, effectiveness of PID controller depends on its three gain values that require proper tuning. Two different tuning methods have been adopted in this study. In the first approach, frequency response-based Zeigler Nichols PID tuning has been considered. In the second approach, a Fuzzy Logic (FL)-based tuning of PID controller gains has been implemented. Moreover, performance of FL-based tuner has been optimized using a binary coded genetic algorithm. It is observed that control performance of FL-based method is substantially better compared to the other method. It may be due to the fact that FL-based method is not taking into account the nonlinearities and plant uncertainties present in the model explicitly. Both the simulation and experimental analysis have been carried out in MatLab Simulink environment.

Design of a Data-Driven PID Controller using Operating Data

We propose a robust self-tuning PID controller suitable for nonlinear systems. The control system employs a preload relay (P_Relay) in series with a PID controller. The P_Relay ensures a high gain to yield a robust performance. However, it also incurs a chattering phenomenon. In this paper, instead of viewing the chattering as an undesirable yet inevitable feature, we use it as a naturally occurring signal for tuning and re-tuning the PID controller as the operating regime digresses. No other explicit input signal is required. Once the PID controller is tuned for a particular operating point, the relay may be disabled and chattering ceases correspondingly. However, it is invoked when there is a change in set-point to another operating regime. In this way, the approach is also applicable to time-varying systems as the PID tuning can be continuous, based on the latest set of chattering characteristics. Simulation results for the level control of fluid in a spherical tank using the scheme are also presented.

In this paper, we are interested in adaptive neural PID control with a reference model for nonlinear systems. A recurrent neural network architecture is studied, and its parameters are computed to mimic a conventional PID controller. Two neural networks architectures, Feed Forward Neural Network (FFNN) and Recurrent Neural Network (RNN) are used for modeling nonlinear systems. To avoid the errors of the Jacobian system approximation, it is best to model the system with a neural network called an emulator. By adding an emulator in parallel with the dynamic system model, the emulator will be trained to learn the dynamics of the system.The back-propagation method is used as the basis for developing algorithms capable of modeling and controlling our nonlinear systems.

PID control schemes have been widely employed for most process systems represented by chemical processes. However, it is a very important problem how to tune PID parameters, because these parameters have a great influence on the stability and the performance of the control system. On the other hand, lots of works for the robust control have been carried out to cope with system uncertainties. Then, some PID parameter tuning methods have been proposed based on the robust stability. However, if the range of uncertainties is very large, the control performance becomes quite conservative. By the way, the support vector machine (SVM) has been proposed as one of the pattern recognition methods and gets lots of attention in last decades. The main motivation in this paper is to present a design scheme of controllers with the switching structure, in which some robust PID controllers are suitably switched using the SVM. Finally, the proposed control scheme is numerically evaluated on a simulation example.

This thesis focuses on the development and analysis of general methods for the design of optimal discrete PID control strategies for multivariable glass furnace processes, where standard genetic algorithms (SGAs) are applied to optimise specially formulated objective functions. Furthermore, a strong emphasis is given on the realistic model parameters identi cation method, which is illustrated to be applicable to a wide range of higher order model parameters identi cation problems. A complete, realistic and continuous excess oxygen model with nonlinearity effect was developed and the model parameters were identified. The developed excess oxygen model consisted of three sub-models to characterise the real plant response. The developed excess oxygen model was evaluated and compared with real plant dynamic response data, which illustrated the high degree of accuracy of the developed model. A new technique named predetermined time constant approximation was proposed to make an assumption on the initial value of a predetermined time constant, whose motive is to facilitate the SGAs to explore and exploit an optimal value for higher order of continuous model's parameters identi cation. Also, the proposed predetermined time constant approximation technique demonstrated that the population diversity is well sustained while exploring the feasible search region and exploiting to an optimal value. In general, the proposed method improves the SGAs convergence rate towards the global optimum and illustrated the effectiveness. An automatic tuning of decentralised discrete PID controllers for multivariable processes, based on SGAs, was proposed. The main improvement of the proposed technique is the ability to enhance the control robustness and to optimise discrete PID parameters by compensating the loop interaction of a multivariable process. This is attained by adding the individually optimised objective function of glass temperature and excess oxygen processes as one objective function, to include the total effect of the loop interaction by applying step inputs on both set points, temperature and excess oxygen, at two different time periods in one simulation. The effectiveness of the proposed tuning technique was supported by a number of simulation results using two other SGAs conventional tuning techniques with 1st and 2nd order control oriented models. It was illustrated that, in all cases, the resulting discrete PID control parameters completely satisfied all performance specifications. A new technique to minimise the fuel consumption for glass furnace processes while sustaining the glass temperature is proposed. This proposed technique is achieved by reducing the excess oxygen within the optimum thermal efficiency region within 1.7% to 3.2%, which is approximately equal to about 10% to 20% of excess air. Therefore, by reducing the excess oxygen set point within the optimum region, 2.45% to 2%, the fuel consumption is minimised from 0:002942kg/sec to 0:002868kg/sec while the thermal efficiency of the glass temperature is sustained at the desired set point (1550K). In addition, a reduction in excess oxygen within methane combustion guidelines will assure that undesirable emissions are in control throughout the combustion process. The efficiencies of the proposed technique were supported by a number of simulation results applying the three SGAs controller tuning techniques. It was illustrated that, in all cases, the fraction of excess oxygen reduction results in a great minimisation of fuel consumption over long plant operating periods.

Pneumatic Muscle Actuator (PMA) has a broad application prospect in soft robotics. However, PMA has highly nonlinear and hysteretic properties among force, displacement, and pressure, which lead to difficulty in accurate position control. A phenomenological model is developed to portray the hysteretic behavior of PMA. This phenomenological model consists of linear component and hysteretic component force. The latter component is described by Duhem model. An experimental apparatus is built up and sets of experimental data are acquired. Based on the experimental data, parameters of the model are identified. Validation of the model is performed. Then a novel cascade position PID controller is devised for a 1-DOF manipulator actuated by PMA. The outer loop of the controller is to cope with position control whilst the inner loop deals with pressure dynamics within PMA. To enhance the adaptability of the PID algorithm to the high nonlinearities of the manipulator, PID parameters are tuned online using RBF Neural Network. Experiments are performed and comparison between position response of RBF Neural Network based PID controller and that of classic PID controller demonstrates the effectiveness of the novel adaptive controller on the manipulator.

Design of RTDA controller for industrial process using SOPDT model with minimum or non-minimum zero

PID control has been applied in many real systems. The control performance strongly depends on PID parameters. Although, some schemes for tuning PID parameters have been proposed, these schemes require system parameters which are estimated by system identification in order to calculate PID parameters. Moreover, most process systems are multivaliable systems which have interference of each respective inputs. On the other hand, data-oriented controller design schemes represented by VRFT or FRIT have received much attention in the last few years. These methods can calculate control parameters using closed loop data, and are expected to reduce computational costs. However, these methods have not been extended for MIMO systems. In this paper, a type of data-oriented multivariable PID controller using closed loop data is proposed. According to the proposed method, full matrices PID parameters which suppress mutual interference are calculated based on the implicit GMVC. Moreover, the control performance can be suitably adjusted by user-specified parameters. The effectiveness of the proposed method is numerically and experimentally evaluated.

Robust tuning of PI controllers based on taguchi method

This paper represents using Case-Based Reasoning (CBR) in order to support undergraduate control engineering students for learning nonlinear systems and control applications. CBR is an experience-based problem solving methodology; thus, it is used for helping control engineering students to design conventional PID controllers for nonlinear systems. For this purpose, GUNT pH neutralization process is used as the experimental setup and a GUI is designed for cased-based reasoning in MATLAB. It is observed that undergraduate students can learn and increase their experience on nonlinear systems using the proposed new CBR-GUI.

This paper presents the comparative study of Model Predictive Controller (MPC) with PID Controller implemented for flow control loop in LABVIEW. Classical PID controller is mostly used in process instrumentation yet tuning of PID controller is the crucial part to be dealt with. Moreover, changes in the parameters of the loop components affects the tuning of the controller, hence over a period of time retuning of PID controller is required. On the other hand MPC controller works on the process model which predicts and optimizes the process performance. Here, Flow control loop performance was studied for MPC and PID controller. MPC worked on 1st order state space system model and PID was tuned using Internal Model Control (IMC) method. The result of implementation shows that, MPC controller performs much better than PID controller. Set point of with less settling time and zero peak overshoot was observed in MPC whereas PID has comparatively more settling time and peak overshoot.

This paper proposes a new offline learning algorithm for a data-driven proportional-integral-derivative (DD-PID) controller based on an extended fictitious reference iterative tuning (E-FRIT). PID controllers have been used in many process systems. However, it is difficult to maintain a good control performance using PID controllers with fixed control parameters because of the nonlinearity of the systems. The DD-PID controller has been proposed as an effective control system for nonlinear systems. This controller can tune its PID parameters adaptively at each equilibrium point of the system output. In the conventional DD-PID controller, the PID parameters are learned so as to minimize a criterion of the FRIT method. However, the FRIT method is based on minimization of the error in system output, and therefore, the criterion is insufficient for systems, such as chemical process systems, for which the stability of a closed loop system is essential. In order to solve this problem, the E-FRIT method has been proposed; a penalty for input variation is incorporated in the criterion for this method. In the present study, an offline learning rule of PID parameters was derived based on the E-FRIT criterion. According to the rule, the PID parameters that are taken into stability can be calculated. The effectiveness of the proposed method was evaluated by simulations of a polystyrene reactor system. The simulation confirmed that the proposed DD-PID controller yields better control result than the conventional learning method.