High performance disturbance observer based control system design for permanent magnet synchronous AC machine applications

This thesis was submitted for the award of Doctor of Philosophy and was awarded by Brunel University LondonAn electrical machine is one of the main workforces in different industries and serves them in various applications. Machine drive control design involves many technical issues for efficient and robust exploitation. Over several decades, Permanent Magnet Synchronous Motor (PMSM) is getting preferred for industrial applications over its counterpart Squirrel Cage Induction Motor (SCIM) drive, because of their higher efficiency, power density, and higher torque to inertia ratio. In the prospective that PMSM drives are considered the drives of the future, there are still technical challenges and issues related to PMSM control. Many studies have been devoted to PMSM control in the past, but there are still some open research areas that bring worldwide researchers’ interests back to PMSM drive control. One of the approaches that may facilitate better performance, higher efficiency, and robust and reliable work of the control system is the disturbance observer-based control (DOBC) with linear and nonlinear output feedback control for PM synchronous machine applications. DOBC is adopted due to its ability to reject external and internal disturbances with improving tracking performance in the variable speed wind energy conversion system (WECS) to maximize power extraction. The high order disturbance observer (HODO) is utilized to estimate the aerodynamic torque-based wind speed without the use of a traditional anemometer, which reduces the overall cost and improves the reliability of the whole system. Also, this method has been designed to improve the angular shaft speed tracking of the PMSM system under load torque disturbance and speed variations. The model-based linear and nonlinear feedback control are used in the proposed control systems. The sliding mode control (SMC) with switching output feedback control law and integral SMC with linear feedback and state-dependent Riccati equation (SDRE) based approaches have been designed for the systems. The SDRE control accounts for the nonlinear multivariable structure of the WECS and is approximated with Taylor series expansion terms. The chattering inherited from SMC is eliminated by the continuous approximation technique. The sliding mode is guaranteed by eliminating the reaching mode in the proposed integral SMC. The model-free cascaded linear feedback control system based on the proportional-integral (PI) controllers use a back-calculation algorithm anti-windup scheme. The proposed speed controllers are synthesized with HODO to compensate for the external disturbance, model uncertainty, noise, and modelling errors. Moreover, servomechanism-based SDRE control, a near-optimal control system is designed to suppress the model uncertainty and noise without the use of disturbance observers. The proposed control systems for PMSM speed regulation have demonstrated a significant improvement in the angular shaft speed-tracking performance at the transients. Their performances have been tested under speed, load torque variations, and model uncertainty. For example, HODO-based SMC with switching output feedback control law (SOFCL) has demonstrated improvement by more than 78% than the PI-PI control system of the PMSM. The performance of the HODOs-based Integral SMC with SDRE nonlinear feedback is improved by 80.5% under external disturbance, model uncertainty, and noise than Integral SMC with linear feedback in the WECS. The HODO-based SDRE control with servomechanism has shown an 80.2% improvement of mean absolute percentage error under disturbances than Integral SMC with linear feedback in the WECS. The PMSM speed tracking performance of the proposed HODO-based discrete-time PI-PI control system with back-calculation algorithm anti-windup scheme is improved by 87.29% and 90.2% in the speed commands and load torque disturbance variations scenarios respectively. The simulations for testing the proposed control system of the PMSM system and WECS have been implemented in Matlab/Simulink environment. The PMSM speed control experimental results have been obtained with Lucas-Nuelle DSP-based rapid control prototyping kit.Center for International Program “Bolashak” of the Ministry of Education and Science Republic of Kazakhsta

θ-D Approximation Technique for Nonlinear Optimal Speed Control Design of Surface-Mounted PMSM Drives

This paper proposes nonlinear optimal controller and observer schemes based on a θ-D approximation approach for surface-mounted permanent magnet synchronous motors (PMSMs). By applying the θ-D method in both the controller and observer designs, the unsolvable Hamilton–Jacobi–Bellman equations are switched to an algebraic Riccati equation and statedependent Lyapunov equations (SDLEs). Then, through selecting the suitable coefficient matrices, the SDLEs become algebraic, so the complex matrix operation technique, i.e., the Kronecker product applied in the previous papers to solve the SDLEs is eliminated. Moreover, the proposed technique not only solves the problem of controlling the large initial states, but also avoids the excessive online computations. By utilizing a more accurate approximation method, the proposed control system achieves superior control performance (e.g., faster transient response, more robustness under the parameter uncertainties and load torque variations) compared to the state-dependent Riccati equation-based control method and conventional PI controlmethod. The proposed observer-based control methodology is tested with an experimental setup of a PMSM servo drive using a Texas Instruments TMS320F28335 DSP. Finally, the experimental results are shown for proving the effectiveness of the proposed control approac

θ-D Approximation Technique for Nonlinear Optimal Speed Control Design of Surface-Mounted PMSM Drives

This paper proposes nonlinear optimal controller and observer schemes based on a θ-D approximation approach for surface-mounted permanent magnet synchronous motors (PMSMs). By applying the θ-D method in both the controller and observer designs, the unsolvable Hamilton–Jacobi–Bellman equations are switched to an algebraic Riccati equation and statedependent Lyapunov equations (SDLEs). Then, through selecting the suitable coefficient matrices, the SDLEs become algebraic, so the complex matrix operation technique, i.e., the Kronecker product applied in the previous papers to solve the SDLEs is eliminated. Moreover, the proposed technique not only solves the problem of controlling the large initial states, but also avoids the excessive online computations. By utilizing a more accurate approximation method, the proposed control system achieves superior control performance (e.g., faster transient response, more robustness under the parameter uncertainties and load torque variations) compared to the state-dependent Riccati equation-based control method and conventional PI controlmethod. The proposed observer-based control methodology is tested with an experimental setup of a PMSM servo drive using a Texas Instruments TMS320F28335 DSP. Finally, the experimental results are shown for proving the effectiveness of the proposed control approac

Suboptimal Stabilization of Unknown Nonlinear Systems via Extended State Observers

This paper introduces a locally optimal stabilizer for multi-input muti-output autonomous nonlinear systems of any order with totally unknown dynamics. The control scheme proposed in this paper lies at the intersection of the active disturbance rejection control (ADRC) and the state-dependent Riccati equation (SDRE) technique. It is shown that using an extended state observer (ESO), a state-dependent coefficient matrix for the nonlinear system is obtainable which is used by the SDRE technique to construct a SDRE+ESO controller. As the SDRE technique is not guaranteed to be globally asymptotically stable, for systems with known linearization at the equilibrium, an algorithmic method is proposed for an approximated estimation of its region of attraction (ROA). Then, it is shown that the global asymptotic stability is achievable using a switching controller constructed by the SDRE+ESO method and ADRC for inside and outside the estimated ROA, respectively.Comment: 6 pages, 1 figur

Design and Analysis of a Generalized High-Order Disturbance Observer for PMSMs with a Fuzy-PI Speed Controller

This paper proposes a generalized high-order observer for estimating total disturbance of permanent magnet synchronous motors (PMSMs). This total disturbance is dominated by load torque but also includes many other terms such as frictions, viscous force, Eddy and flux pulling forces, and noises. Comprehensive experimental results and analyses under various scenarios will be presented to find the appropriate order of the observer. We will compare the performance of zero-order observer (ZDO), first-order observer (FDO), and second-order observer (SDO) under three different scenarios of load torque..

Управління маніпулятором методом SDRE

В даній роботі описується сфера оптимального та субоптимального керування нелінійними об’єктами за допомогою методу Ріккаті, а також розглянуто математичну модель управління маніпулятора та запропоновано практичне застосування описаного математичного апарату в системах управління роботизованою технікою

Nonlinear Systems

Open Mathematics is a challenging notion for theoretical modeling, technical analysis, and numerical simulation in physics and mathematics, as well as in many other fields, as highly correlated nonlinear phenomena, evolving over a large range of time scales and length scales, control the underlying systems and processes in their spatiotemporal evolution. Indeed, available data, be they physical, biological, or financial, and technologically complex systems and stochastic systems, such as mechanical or electronic devices, can be managed from the same conceptual approach, both analytically and through computer simulation, using effective nonlinear dynamics methods. The aim of this Special Issue is to highlight papers that show the dynamics, control, optimization and applications of nonlinear systems. This has recently become an increasingly popular subject, with impressive growth concerning applications in engineering, economics, biology, and medicine, and can be considered a veritable contribution to the literature. Original papers relating to the objective presented above are especially welcome subjects. Potential topics include, but are not limited to: Stability analysis of discrete and continuous dynamical systems; Nonlinear dynamics in biological complex systems; Stability and stabilization of stochastic systems; Mathematical models in statistics and probability; Synchronization of oscillators and chaotic systems; Optimization methods of complex systems; Reliability modeling and system optimization; Computation and control over networked systems

Performance enhancement of multivariable model reference optimal adaptive motor speed controller using error-dependent hyperbolic gain functions

The main contribution of this paper is to formulate a robust-adaptive and stable state-space speed control strategy for DC motors. The linear-quadratic-integral (LQI) controller is utilized as the baseline controller for optimal speed-regulation, accurate reference-tracking and elimination of steady-state fluctuations in the motor’s response. To reject the influence of modelling errors, the LQI controller is augmented with a Lyapunov-based model reference adaptation system (MRAS) that adaptively modulates the controller gains while maintaining the asymptotic stability of the controller. To further enhance the system’s robustness against parametric uncertainties, the adaptation gains of MRAS online gain-adjustment law are dynamically adjusted, after every sampling interval, using smooth hyperbolic functions of motor’s speed-error. This modification significantly improves the system’s response-speed and damping against oscillations, while ensuring its stability under all operating conditions. It dynamically re-configures the control-input trajectory to enhance the system’s immunity against the detrimental effects of random faults occurring in practical motorized systems such as bounded impulsive-disturbances, modelling errors, and abrupt load–torque variations. The efficacy of the proposed control strategy is validated by conducting credible hardware-in-the-loop experiments on QNET 2.0 DC Motor Board. The experimental results successfully validate the superior tracking accuracy and disturbance-rejection capability of the proposed control strategy as compared to other controller variants benchmarked in this article

RECENT TECHNIQUES ON OBSERVER DESIGN FOR DISTURBANCE ESTIMATION AND REJECTION IN PERMANENT MAGNET SYNCHRONOUS MOTORS

Permanent magnet synchronous machines (PMSMs) (either motor or generator) have attracted attention of research community comparing to other types of AC machines in the recent two decades. PMSMs are preferable than other AC machines in terms of large power-factor, broad speed of operation, compact proportions, and effective operation. Unfortunately, different sources of nonlinearities, model uncertainties, and external perturbations determine severity in a design of accurate speed control scheme for PMSMs. In the era of developing science and technologies, many advanced control solutions are proposed to control PMSMs. Although new solutions show their advantages comparing to traditional methods in terms of performance evaluation, practical realization of those algorithms could require expensive hardware with high computational capabilities. Furthermore, people in industry with less knowledge about the motor control may experience difficulties in using such advanced controllers on their own. Traditional PI/PID control schemes still work as a major control technique in modern industry, and in motor control as well. Numerous positive facts about the PI/PID schemes make such superiority of these control schemes. Firstly, the PI/PID can be implemented easily on most industrial software and hardware components. Secondly, while its scheme has clear mechanism of operation, most industrial processes could be controlled via the PI/PID scheme. These schemes are good in terms of small number of parameters to tune and tuning process itself could be very straightforward. Finally, implementation of the PI/PID controllers would require smaller time comparing to most proposed complex control solutions. It is studied that the traditional PI/PID controllers usually cannot deal with unpredictable disturbances, which in turn leads to degraded performance of an overall control system. Inspired by the advantages and widespread application of PI/PID control structure in industry, we propose a disturbance observer based composite control scheme which uses the PI-like controller for the feedback regulation and disturbance observer for estimation of lumped disturbances presented in a PMSM control system. Under this circumstance, this thesis work proposes three different control solutions for PMSM such as High-order disturbance observer-based composite control (HDOBCC), Disturbance rejection PI (DR-PI) control, and Hierarchical optimal disturbance observer-based control (HODOBC). Furthermore, to deeply understand the similarity and difference between the traditional disturbance observer-based control (DOBC) and active-disturbance rejection control (ADRC) schemes, this thesis also presents results of unification of these two control approaches in the speed control of a PMSM. The HDOBCC as the first method proposed in this thesis is designed to improve reference speed tracking performance of a PMSM under various operational conditions. A structure of the HDOBCC comprises a fuzzy-PI controller in a feedback stabilization part and novel high-order disturbance observer in a feedforward compensation part of the speed control system. The proposed controller is designed based on the research questions such as: firstly, although a fixed gain traditional PI controller is able to present satisfactory performance at some extent, still it does not guarantee such performance when sudden disturbances occur in a system; secondly, many disturbance observers designed for a PMSM in literature consider only a load torque as a disturbance, neglecting model uncertainties and parameter variations in design stage. Therefore, the HDOBCC is proposed such that it utilizes a fuzzy approach to determine parameters of the PI controller to overcome limitations of the fixed gain PI controller. Furthermore, the proposed scheme includes a high-order disturbance observer, which estimates not only the load torque, but also disturbances due to model uncertainties and parameter variations. Moreover, extended simulation and experimental studies are conducted to affirm performance of the HDOBCC under various form of the load torque. In addition to commonly tested step form of a load torque, severe forms of the load torque such as triangular form and sinusoidal form are tested with the proposed controller. Stability analysis of the closed-loop HDOBCC system is further provided. The next proposed method, DR-PI control, is designed by seeking answer for questions such as: firstly, although the traditional DOBC scheme applied for PMSM shows reasonable results in a PMSM control, its design can be limited to known actual parameters of the PMSM. In practice, actual parameters are usually not available, hence it could be hard to design the traditional DOBC in the absence of a plant information; secondly, for tuning a PI controller the traditional Ziegler-Nichols tuning approach still remains as one of the popular tuning approaches, however it does not give a rigorous explanation on selection of parameters during its design. Consequently, to answer these questions, the DR-PI control is designed for the PMSM speed control. The DR-PI control is designed such that it has a simple PI-like structure with intrinsic disturbance rejection mechanism determined by the parameters of a filtering element, desired plant model, and desired closed-loop system. Simulation and experimental validations are provided to validate the performance of the DR-PI. Furthermore, gain tuning mechanism and stability analysis of the closed-loop DR-PI-based speed control are also presented. The HODOBC scheme as a third proposed control scheme targets on the next research questions as: first, parameters of the traditional PI controller are mostly obtained by trial-and-error approach, which in turn may not guarantee satisfactory results; in a cascaded PMSM control, the outer speed loop performance highly depends on the performance of the inner current loop. The well-tuned speed control loop may degrade in performance, if the inner current loop is not tuned properly. To address these questions, we propose the HODOBC scheme, which consists of optimal PIlike controller in the feedback stabilization part and optimal extended-state observer (ESO) in the disturbance compensation part. The proposed HODOBC showed better performance when it is compared with other traditional controllers via experiments. Stability analysis is provided via the root locus approach. The study on unification of the DOBC and ADRC schemes has the following research question: the DOBC and ADRC are both used in estimation of total disturbance, but these two schemes are considered differently in literature. Hence, the study of both scheme is conducted to show the condition at which these two schemes show identical performance. The analysis of the traditional DOBC and ADRC schemes concludes that both scheme are equivalent in terms of performance characteristics if the dynamical delays of disturbance observers in each scheme are same. The results of analysis reveal that both scheme can be utilized to design a robust control system for PMSM, i.e. once the gains of disturbance observers can be calculated under the DOBC framework, further the disturbance rejection mechanism can be achieved via the ADRC framework. The results of PMSM control with the proposed control schemes have been tested on the Lucas-Nuelle DSP-based experimental setup

Mathematical and Numerical Aspects of Dynamical System Analysis

From Preface: This is the fourteenth time when the conference “Dynamical Systems: Theory and Applications” gathers a numerous group of outstanding scientists and engineers, who deal with widely understood problems of theoretical and applied dynamics. Organization of the conference would not have been possible without a great effort of the staff of the Department of Automation, Biomechanics and Mechatronics. The patronage over the conference has been taken by the Committee of Mechanics of the Polish Academy of Sciences and Ministry of Science and Higher Education of Poland. It is a great pleasure that our invitation has been accepted by recording in the history of our conference number of people, including good colleagues and friends as well as a large group of researchers and scientists, who decided to participate in the conference for the first time. With proud and satisfaction we welcomed over 180 persons from 31 countries all over the world. They decided to share the results of their research and many years experiences in a discipline of dynamical systems by submitting many very interesting papers. This year, the DSTA Conference Proceedings were split into three volumes entitled “Dynamical Systems” with respective subtitles: Vibration, Control and Stability of Dynamical Systems; Mathematical and Numerical Aspects of Dynamical System Analysis and Engineering Dynamics and Life Sciences. Additionally, there will be also published two volumes of Springer Proceedings in Mathematics and Statistics entitled “Dynamical Systems in Theoretical Perspective” and “Dynamical Systems in Applications”