Efficient Disturbance Rejection Research Articles

Optimization of RST Controller for Speed Control of Linear Induction Motor Using Genetic Algorithm

Background: In this study, a new model of linear induction motor, along with the impact of end-effect on motor performance, is proposed. Moreover, a new strategy of control approach based on the polynomial RST controller is suggested and investigated. Objective: The proposed approach can provide a robust control strategy and overcome the limitations imposed by the proportional-integral (PI) regulator in the FOC technique. RST controller has a two-degree of freedom structure and consists of three polynomials, namely R, S and T, which are determined by the pole placement method and resolving of a Diophantine equation. Despite this, the implementation of this method is usually difficult and becomes more complicated with the complexity of the controlled plants. Methods: This study proposes the genetic algorithm (GA) optimization strategy for tuning RST controller parameters (adjust the controller coefficients) in order to achieve an adequate response time by minimizing the different objective functions, such as steady-state error, settling time, and rise time. Results: The accuracy and control performance of the proposed technique are checked and validated using Matlab /Simulink environment software tool. Simulation results reported that the proposed method (RST-GA) could provide robust solutions with perfect reference tracking and efficient disturbance rejection. Conclusion: These significant results make the proposed approach a promising technique for the design of a high-performance controller, which is highly suitable for industrial and electrical applications.

Efficient disturbance rejection of gimbaled inertial stabilization platform via relay controller

In this article a relay controller is introduced in the simple motor driven gimbaled inertial stabilization platform (ISP) to improve disturbance rejection capacity. This improvement is possible through the manipulation of the adaptive feature of a limit cycle inherent in relay control systems. We present the sufficient condition for the existence of a limit cycle and its stability analysis in the relay control system, along with how this limit cycle can suppress the exogenous torque disturbance efficiently even in the presence of randomly distributed exogenous inputs. As a disturbance rejection measure, line-of-sight stabilization accuracy was obtained with an ISP driven by a typical linear controller and one by a relay controller, respectively. The results of numerical examples show the effectiveness and efficiency of the relay controller over a typical linear controller.

Self-tuning strategy for a minimum variance control system of a highly disturbed process

The paper presents an original self-tuning strategy for a minimum variance controller used to control highly disturbed processes. The role of the proposed algorithm is to implement a self-protection mechanism against major disturbances produced by measurable perturbations acting on a controlled plant. By a variable setting of the control penalty factor (ρ), which weights the influence of the control variance in a cost criterion function, the main objective is to maintain the stability of the control system, even under action of high perturbations. This new self-tuning strategy is based on the assumption that the disturbances acting on the controlled plant are measurable, being implemented and tested for the case of an induction generator integrated into a wind energy conversion system. The power control system's main goal is to reject the disturbance generated by a mechanical torque variation, due to variable wind speed, acting as an external measurable perturbation. Depending on the variation range of this mechanical torque (small variations corresponding to a relatively stationary regime or high variations due to wind gusts), the proposed algorithm sets the control penalty factor to different values. As a result, the overall effect of the self-tuning strategy will be to extend the operating range of the wind aggregate, by maintaining the stability of the control system (strongly disturbed by high wind gusts) and also by an efficient disturbance rejection. As a novelty, the base rule of the self-tuning strategy proposes a rectangular pulse variation of the control penalty factor when a high disturbance occurs. By setting a high amplitude for this pulse variation of ρ, the control is strongly limited, thus ensuring the system stability. At the end of this pulse with a suitable width, the effect of disturbance is fast rejected by returning to a small stationary value of ρ, which allows high enough control. Although designed and validated for a particular case, this self-tuning strategy is generally valid for the minimum variance control of any other process disturbed by measurable perturbations.

Robust tracking system design for a synchronous reluctance motor – SynRM based on a new modified bat optimization algorithm

This paper discusses optimal controller structure design for a Synchronous Reluctance Motor (SynRM). Optimization of controller parameters is based on a new modified BAT optimization algorithm (mBAT). SynRM is represented with a nonlinear dynamic model of a synchronous machine. All gathered nonlinearities of SynRM are taken into account in the controller’s design and optimization procedure with mBAT. A novel SynRM controller structure with a modified robust disturbance observer (mRDO) is presented. The modified mRDO ensures a higher level of stability margin, efficient disturbance rejection, and enables transparent controller parametrization and optimization. Controller synthesis is based on robust ℋ∞ pole-placement technique. The ℋ∞ robust criteria are presented in the form of spectral polynomials and their strong positivity conditions. Spectral polynomials (SP) can be directly used as objective functions in the mBAT optimization procedure. The mBAT algorithm, in terms of the derived SP introduces a novel approach to adaptive weighting function selection and modification of BAT velocity in the position formula. The new modification of the BAT algorithm is inspired by feedback control theory and Lyapunov exponential stability property. The proposed modification of the mBAT significantly increases the efficiency of the given optimization problem.

Two Degree of Freedom PID Controller in Time Delay System using Hybrid Controller Model

In the paper, a hybrid method based two-degree of freedom (2-DOF) PID controller is proposed for tuning the time delay system. The hybrid technique is the combination of fuzzy logic controller (FLC) and gravitational search algorithm (GSA). Here, the GSA is utilised for generating the logic rules of FLC. The 2-DOF proportional integral and derivative (PID) controller ensures highly efficient disturbance rejection and reliable performance. Here, tuning of a 2-DOF PID controller with a time delay system design achieves a high performance for a wide range. For the automatic tuning process, the parameters of time delays system is predicted and tuned optimally in the short period of time. The first order time delay system is tuned and the stability parameters such as small overshoot, settling time and rising time has been achieved. From the results, it is noted that, proposed controller provides enhanced results for the reference tracking and disturbance rejection operations. The effectiveness and feasibility of the proposed technique is demonstrated through the MATLAB/Simulink platform and the performance is tested and compared with the existing controller tuning methods such as FLC technique with genetic algorithm (GA) and artificial neural network (ANN) techniques.

Advanced Modeling and Control of a Solid Sorbent-Based CO2 Capture Process

Solid sorbent-based CO2 capture from flue gas provides a novel alternative to traditional solvent-based processes due to potentially lower energy consumption for regeneration. Optimal operation of such a gas-solid flow process requires an advanced control framework for efficient disturbance rejection and setpoint tracking. This work focuses on the development of computationally fast and accurate dynamic reduced models (D-RMs) and the application of these models to nonlinear model predictive control (NMPC) algorithms. Two different types of D-RMs are developed: the first type is a data-driven model where step-test data are utilized to generate the D-RM through the Decoupled A-B Net (DABNet) model, and the second type of D-RM is a temporal and spatial reduction of the original process model to improve its computational efficiency while still retaining its physics. Disturbance rejection and setpoint tracking characteristics of the NMPC and its computational performance are studied for both types of D-RMs. In addition, performance of both NMPC formulations are compared with linear model predictive control (LMPC) formulations.

A Self-Tuning zSlices-Based General Type-2 Fuzzy PI Controller

The interval type-2 fuzzy Proportional-Integral (PI) controller (IT2-FPI) might be able to handle high levels of uncertainties to produce a satisfactory control performance, which could be potentially due to the robust performance as a result of the smoother control surface around the steady state. However, the transient state and disturbance rejection performance of the IT2-FPI may degrade in comparison with the type-1 fuzzy PI (T1-FPI) counterpart. This drawback can be resolved via general type-2 fuzzy PI controllers which can provide a tradeoff between the robust control performance of the IT2-FPI and the acceptable transient and disturbance rejection performance of the type-1 PI controllers. In this paper, we will present a zSlices-based general type-2 fuzzy PI controller (zT2-FPI), where the secondary membership functions (SMFs) of the antecedent general type-2 fuzzy sets are adjusted in an online manner. We will examine the effect of the SMF on the closed-system control performance to investigate their induced performance improvements. This paper will focus on the case followed in conventional or self-tuning fuzzy controller design strategies, where the aim is to decrease the integral action sufficiently around the steady state to have robust system performance against noises and parameter variations. The zSlices approach will give the opportunity to construct the zT2-FPI controller as a collection of IT2-FPI and T1-FPI controllers. We will present a new way to design a zT2-FPI controller based on a single tuning parameter where the features of T1-FPI (speed) and IT2-FPI (robustness) are combined without increasing the computational complexity much when compared with the IT2-FPI structure. This will allow the proposed zT2-FPI controller to achieve the desired transient state response and provide an efficient disturbance rejection and robust control performance. We will present several simulation studies on benchmark systems, in addition to real-world experiments that were performed using the PIONEER 3-DX mobile robot that will act as a platform to evaluate the proposed systems. The results will show that the control performance of the self-tuning zT2-FPI control structure enhances both the transient state and disturbance rejection performances when compared with the type-1 and IT2-FPI counterparts. In addition, the self-tuning zT2-FPI is more robust to disturbances, noise, and uncertainties when compared with the type-1 and interval type-2 fuzzy counterparts.

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 $$(M_S )$$ .

A robust LMI-based pitch controller for large wind turbines

Abstract This paper utilizes the linear matrix inequalities’ techniques (LMI) for designing a robust collective pitch controller (CPC) for large wind turbines. CPC operates during up rated wind speeds to regulate the generator speed in order to harvest the rated electrical power. The proposed design takes into account model uncertainties by designing a controller based on a polytopic model. The LMI-based approach allows additional constraints to be included in the design (e.g. H∞ problem, H2 problem, H∞/H2 trade-off criteria, and pole clustering). These constraints are exploited to include requirements for perfect regulation, efficient disturbance rejection, and permissible actuator usage. The proposed controller is combined with individual pitch controller (IPC) that reduces the periodic blade’s load by alleviating once per revolution (1P) frequency fatigue loads. FAST (Fatigue, Aero-dynamics, Structures, and Turbulence) software code developed at the US National Renewable Energy Laboratory (NREL) is used to verify the results.

Designing Pitch Controller for Large Wind Turbines via LMI Techniques

This paper proposes a design of robust LMI-based collective pitch controllers (CPC) for large wind turbines operating above their rated wind speeds. The proposed controller design takes into account model uncertainties by designing a controller based on a polytopic model. The LMI-based approach allows additional constraints to be included in the design (e.g. H∞ problem, H2 problem, H2/H∞ trade-off criteria, and pole clustering).These constrains are exploited to include requirements for perfect regulation, efficient disturbance rejection, and permissible actuator usage. The proposed controller is combined with individual pitch controller (IPC) that reduces the periodic blade's load by alleviating once per revolution (1P) frequency fatigue loads.