Adaptive Pole Placement Control Research Articles

A Robust Adaptive Control Strategy of Active Power Filters for Power-Factor Correction, Harmonic Compensation, and Balancing of Nonlinear Loads

This paper introduces a robust adaptive control strategy of shunt active power filters (SAPF) for power-factor correction, harmonic compensation, and balancing of nonlinear loads. The proposed control scheme is implemented without load harmonic detection. The compensation constraints are obtained by regulating indirectly the currents of the power mains. The reference currents of are generated by the dc-link voltage controller based on the active power balance of system. They are aligned to the phase angle of the power mains voltage vector, by using a phase-locked loop system. The current control strategy is implemented by an adaptive pole-placement control strategy integrated to a variable structure control scheme. This control scheme uses the internal model principle of reference currents for achieving the zero steady-state tracking error. Experimental results are shown for determining the effectiveness of an -proposed control system.

Vibration Control and Dynamical Model of a Thermal-Electrical-Mechanical Coupled Smart Cantilevered Beam

Piezoelectric actuators used in vibration control and high precision control have been known widely in recent years. Especially in aeronautics and MEMS systems, their use is spread from vibration suppression to position control. In this paper, a finite element model (FEM) of a piezoelectric actuator and cantilever in thermal environment is presented to suppress vibration effectively. In other words, the finite element model is namely thermal-electrical-mechanical coupled FEM. Based on a 8-node plane finite element, the modal analysis, the harmonic analysis and the transient analysis have been obtained in the current work. Therefore a transfer function model will be attained through the harmonic analysis by identification method in order to control vibration by control law. In addition, the controller will be designed with the adaptive pole placement control (APPC). Finally, through simulation, the thermal influence is considerable for natural frequencies, harmonic response and free vibration. Moreover, the APPC is a significant plan to vibration control in the paper.

Adaptive pole-placement control of 4-leg voltage-source inverters for standalone photovoltaic systems

Three-leg inverters for photovoltaic systems have many disadvantages, especially when the load is unbalanced. These disadvantages are, for example, small utilization of the DC link voltage, the dependency of the modulation factor of the load current and the superposition of a DC component with the output AC voltage. A solution for these problems is the 4-leg inverter. Most papers dealing with 4-leg inverters suggest classic controllers, such as PI controller, for the system. However, the transient performance of the closed-loop system does not become acceptable. On the other hand, adaptive control of 4-leg inverters has not yet been discussed in the literature. This paper proposes pole-placement control strategy, via state feedback, for 4-leg voltage-source inverters to adjust the transient performance of the closed-loop system. In addition, a STR (self-tuner regulator) is introduced to guarantee the adaptive performance of the controller in the presence of time-variant RL loads. Simulation results validate the theoretical results and proposed control strategy.

Adaptive Control Tutorial (P. Ioannou et al.; 2006) [Bookshelf

The purpose of this book is to present the fundamental techniques and algorithms of adaptive control in a tutorial manner to a wide audience, including engineers, students, and researchers. Some of the topics covered include: basic design methods, technical issues and history; two common parametric models of dynamic systems; the adaptive parameter identification (estimation) problem for continuous-time systems and for discrete-time systems; model reference adaptive control (MRAC) for continuous-time systems; designing indirect adaptive pole placement control (APPC); discrete-time versions of MRAC and APPC schemes; and adaptive control of nonlinear dynamic systems. The book includes a well-prepared appendix that covers a broad list of topics and results on systems theory, especially stability theory, in both continuous time and discrete time. The book is comprehensive, rigorous, well written and easy to read. It can be used as an introductory textbook or a technical reference.

Pole Placement Techniques for Active Vibration Control of Smart Structures: A Feasibility Study

It is well known that there is degradation in the performance of a fixed parameter controller when the system parameters are subjected to a change. Conventional controllers can become even unstable, with these parametric uncertainties. This problem can be avoided by using robust and adaptive control design techniques. However, to obtain robust performance, it is desirable that the closed-loop poles of the perturbed structural system remain at prespecified locations for a range of system parameters. With the aim to obtain robust performance by manipulating the closed loop poles of the perturbed system, feasibility of the pole placement based controller design techniques is checked for active vibration control applications. The controllers based on the adaptive and robust pole placement method are implemented on smart structures. It was observed that the adaptive pole placement controllers are noise tolerant, but require high actuator voltages to maintain stability. However, robust pole placement controllers require comparatively small amplitude of control voltage to maintain stability, but are noise sensitive. It was realized that by using these techniques, robust stability and performance can be obtained for a moderate range of parametric uncertainties. However, the position of closed-loop poles should be judiciously chosen for both the control design strategies to maintain stability.

Design of discrete-time adaptive repetitive controllers and application to feed drive systems

Although repetitive control is well known to be useful for controlling systems required to perform periodic motions with high accuracy, the repetitive control system is generally a high-order system and has undesirable high-frequency characteristics. Hence, there has been much research on the robustness improvement of repetitive controllers. Although adaptive control is useful when the plant dynamics is unknown, little effort has been made to apply adaptive control to the repetitive control system. Since the repetitive control system is generally a high-order system, many controller parameters need to be estimated online, especially if adaptive pole-placement control, which enables arbitrary pole placement of the control system, is applied. This paper presents a discrete-time design of adaptive poleplacement repetitive controllers for plants with unknown transfer function coefficients (orders of the plants are assumed to be known) and disturbances by assuming that a non-minimum phase continuous-time plant is controlled with a small sampling period. From this assumption, plant unstable zeros appearing by discretization can be approximated by known ones (limiting zeros). By employing the idea of limiting zeros, the repetitive controller can be realized as a feedforward controller without knowing the plant transfer function coefficients. Since the repetitive controller is placed out of the feedback loop by this design, the adaptive pollplacement controller can be realized without updating a large number of controller parameters. Experimental results with the application of a feed drive system, which is often used in computer numerical control (CNC) machine tool systems with repetitive motion, demonstrate the effectiveness of the proposed method. Design methods with and without the limiting zeros are compared in the experiment. It is then shown that using the limiting zeros reduces the control input variance and improves the control performance.

A VARIABLE STRUCTURE ADAPTIVE POLE PLACEMENT CONTROL APPLIED TO THE SPEED CONTROL OF A THREE-PHASE INDUCTION MOTOR

Due to its flexibility in choosing the controller design methodology and the adaptive law (least squares, gradient, etc.), the Adaptive Pole Placement Control (APPC) is the most general type of adaptive control. It has been developed in an indirect approach and, as an advantage, it may be applied to non-minimum phase plants, because do not involve cancellation of plant zeros. The use of the variable structure systems theory has allowed to aggregate fast transient and robustness to parametric uncertainties and disturbances. In this paper, a Variable Structure Adaptive Pole Placement Control (VS-APPC) is applied to the speed control of an induction motor. Simulations and experimental results are shown.

Controle Adaptativo Por Posicionamento De Pólos E Estrutura Variável Aplicado Ao Controle De Velocidade De Um Motor De Indução Trifásico

Existem dois métodos principais para a construção de controladores adaptativos. Um deles é o Controle Adaptativo por Modelo de Referência (MRAC) e o outro é o Controle Adaptativo por Posicionamento de Pólos (APPC). No MRAC, um modelo de referência é escolhido para gerar a trajetória desejada que o sinal de saída da planta deve seguir, e este modelo pode requerer o cancelamento de zeros da planta. Devido a sua flexibilidade em escolher a metodologia de projeto do controlador (realimentação de estado, projeto de compensador, linear quadrático, etc.) e a lei adaptativa (mínimos quadrados, método do gradiente, etc.), o APPC é o tipo mais geral de controle adaptativo. Tradicionalmente, vem sendo desenvolvido em uma abordagem indireta e, como uma vantagem, pode ser aplicado a plantas de fase não-mínima, já que não envolve cancelamentos de zeros e pólos. A integração aos sistemas com estrutura variável permite agregar rapidez no transitório e robustez às variações paramétricas e perturbações. Neste artigo, um Controlador Adaptativo por Posicionamento de Pólos e Estrutura Variável (VSAPPC) é aplicado ao controle de velocidade de um motor de indução trifásico. São mostrados resultados de simulação e experimentais.

Time-Varying Controller for Temperature-Dependent Viscoelasticity

There are internal-variable techniques that account for the frequency-dependent behavior of viscoelastic materials, but the temperature dependence of these materials has received much less attention. Two methods for designing controllers robust to temperature disturbances are given: (1) Modal reference adaptive control and (2) time-varying pole placement control. Examples that demonstrate the strengths and weaknesses of each are given. The results show that it is possible to achieve vibration reduction while simultaneously rejecting the effects of a temperature disturbance. This work shows that both the frequency and temperature dependence of viscoelastic materials can be modeled with internal variables.

Robust stable pole-placement adaptive control of linear systems with multiestimation

This paper is concerned with a robust pole placement-based adaptive control of continuous linear systems in the presence of bounded noise and a common class of unmodeled dynamics with the use of multiple estimation schemes working in parallel. The multiestimation scheme consists of the above set of various single estimation schemes while being a tool used to minimize the plant identification error by building an estimate which is a convex combination of the estimates at all time. The weighting functions of the individual estimates are provided at each time by a suboptimization scheme for a quadratic loss function The robust stability of the overall adaptive scheme is ensured by an adaptation relative dead zone which takes into account the contribution of the unmodeled dynamics and bounded noise.

An indirect adaptive pole‐placement control for MIMO discrete‐time stochastic systems

AbstractIn this paper, an indirect adaptive pole‐placement control scheme for multi‐input multi‐output (MIMO) discrete‐time stochastic systems is developed. This control scheme combines a recursive least squares (RLS) estimation algorithm with pole‐placement control design to produce a control law with self‐tuning capability. A parametric model with a priori prediction outputs is adopted for modelling the controlled system. Then, a RLS estimation algorithm which applies the a posteriori prediction errors is employed to identify the parameters of the model. It is shown that the implementation of the estimation algorithm including a time‐varying inverse logarithm step size mechanism has an almost sure convergence. Further, an equivalent stochastic closed‐loop system is used here for constructing near supermartingales, allowing that the proposed control scheme facilitates the establishment of the adaptive pole‐placement control and prevents the closed‐loop control system from occurring unstable pole‐zero cancellation. An analysis is provided that this control scheme guarantees parameter estimation convergence and system stability in the mean squares sense almost surely. Simulation studies are also presented to validate the theoretical findings. Copyright © 2005 John Wiley & Sons, Ltd.

Design of Discrete-Time Multivariable Adaptive Repetitive Control Systems

There exist many applications of repetitive control on the factory floor, such as industrial robots and machine tool systems. Since most of the existing repetitive control systems are based on the so-called internal model principle, the system needs to include the internal model of the repetitive reference signals, which is usually higher order model. So it is difficult to apply the adaptive pole placement control because the controller needs to be higher order and a large number of controller parameters need to be estimated online. In this paper we propose a design of adaptive repetitive control systems that are capable of arbitrary pole placement. The proposed controller is based on the two degrees of freedom controller with repetitive feed-forward and adaptive feedback controllers. The adaptive feedback controller is also able to reject unknown disturbances by estimating the internal model of the disturbances. The method is applied to a SCARA-type robot and its effectiveness is experimentally examined.

Direct Adaptive Pole-Placement Control for Pneumatic Servo System.

In pneumatic servo systems, the adaptive pole-placement control system is applied to improve the control performance. In many works, the controller structure of adaptive pole-placement control systems is adopted indirect methods. However, the structure becomes complex in this design scheme, i.e., calculating an inverse matrix. So, we note a direct adaptive pole-placement control system. This paper presents a design scheme of a direct adaptive pole-placement control for pneumatic servo systems. In this design scheme, the control input is sympathized without identification of the plant and calculating an inverse matrix. The effectiveness of the proposed design scheme in confirmed by experiments using the existent pneumatic servo system.

A robust adaptive pole‐placement controller without strictly positive real condition

AbstractThis paper considers the adaptive pole‐placement control problem for system (1) with unmodelled dynamics ηn dominated by a small constant ε multiplied by a quantity independent of ε but tending to infinity as the past input, output, and noise grow. Using bounded external excitation and randomly varying truncation techniques, we give a design method of adaptive pole‐placement controller. It is shown that the closed‐loop system is globally stable, the estimation error for the parameter contained in the modelled part is of order ε, and the closed‐loop system under the adaptive pole‐placement control law is suboptimal in the sense of $$\mathop{\lim\sup}\limits_{{n\to\infty }}{1\over n}\mathop{\sum}\limits_{i=0}^n{\left({A^{*}(z)y_{n}‐L(z)C(z)w_{n}‐B(z)R(z)y_{n}^{*}}\right)^{2}{\leq}O({\varepsilon}^{2})+\gamma^{2}\mathop{\sum}\limits_{j=1}^q{b_{j}^{2}}}$$\nopagenumbers\end while the SPR condition used usually in other papers is replaced by a stability condition. Copyright © 2001 John Wiley & Sons, Ltd.

A Novel Control Scheme for Precise Positioning of Mechanical Positioning Systems

Utilizing the energy-dissipated characteristic of friction, this paper presents a pulse positioning energy model, which extends the application of pulse positioning to disturbance-unmatched systems. The corresponding pole-placement adaptive control algorithm is also given. Based on the energy model and a switch rule, the adaptive control and conventional proportion control are integrated to realize the whole stroke precise positioning of mechanical-positioning systems. Simulations based on the hydraulic-stopper positioning system in mold level control show that the energy model presented in this paper captures the mechanism of pulse positioning and that the control law presented in this paper is simple and effective.

An input‐output approach to achieve adaptive tracking for saturating stable systems

The problem of controlling time-invariant linear systems subject to parametric uncertainty and input saturation constraint, is dealt with using a pole placement adaptive controller. It is shown that the resulting adaptive control system can be described by a non-linear feedback scheme. Then, the l 2 -stability condition for the control system turns out to be the positive-realness of a transfer function involving the plant (estimated) model and the specified closed-loop poles. This makes it necessary to adapt on-line the desired closed-loop poles to the time-varying (estimated) model. The proposed adaptive controller keeps bounded all the closed loop sequences, whatever the initial conditions. Furthermore, it ensures a quite interesting output-reference tracking behaviour. More precisely, the quality of the tracking depends on the reference sequence rate: the slower the reference the better the tracking.

Adaptive Pole-Placement Control Incorporating Neural Network for Pneumatic Servo System.

In pneumatic servo system, an adaptive control method is useful since change in load mass and air compressibility cause parameter variation of the plant. When the discrete time model of the plant becomes non-minimum phase, the adaptive pole-placement control should be applied. However, it is difficult to obtain satisfactory control performances by only using the adaptive pole-placement control when the non-linearity of the plant is not negligible. On the other hand, it is well-known that neural network is effective for such nonlinear plant. This paper presents a design scheme of the discrete-time adaptive pole-placement control incorporating neural network for a pneumatic servo system. In this experiment, we compare the proposed design scheme with a design scheme only using adaptive pole-placement control. As the results, proposed design scheme shows superior control performance in both the transient and steady-state response suppressing the effect of the non-linearity.

The Tracking Control of Mechanical Systems by an Adaptive Pole Placement Controller Combining with a Neural Network

In this paper, an adaptive controller of a plant with unknown parameters and unknown nonlinear frictional force is proposed and applied to the control of a single link robot. The measurement for control is only the motor angle. The proposed adaptive controller is composed of an adaptive pole placement controller and a neural network. The neural network is designed to compensate the nonlinear frictional force and linearize the robot plant. To improve the efficiency of learning of the neural network, an inverse model is introduced. Several considerations are made to improve the robustness of the controller. Many experiments are carried out. The experimental results show the effectiveness of developed control system.

Adaptive dual controller for systems with unmodelled effects

An adaptive pole placement controller with dual modification is applied to a dynamic plant, which is described by an unknown nonlinear model. Stability of the suggested dual contorller, applied together with a robust adaptation scheme, is proved for this system. It is demonstrated that after the insertion of the dual controller, the robust adaptive system remains stable. However, some known assumptions about the unmodelled residuals of the nonlinear plant model should be modified. It is also demonstrated that in the case of no residuals in the plant model, the closed-loop system converges to the model defined by the desired pole positioning. The derived controller is applied to real-time control of hydraulic drive.

An algorithm for adaptive pole placement control of linear systems based on generalized sampled-data hold functions

The use of generalized sampled-data hold functions for adaptive pole placement control of linear systems with unknown parameters, is investigated. The particular control structure used relies on a periodic controller, which suitably modulates the sampled plant output by a multirate periodically time-varying function. Such a control strategy, allows us to assign the eigenvalues of the closed-loop monodromy matrix to the desired prespecified values and does not make assumptions on the plant other than controllability, observability and known order. The proposed indirect adaptive scheme estimates the unknown plant parameters on-line, from sequential data of the inputs and the outputs of the plant, which are recursively updated within the time limit imposed by a fundamental sampling period. On the basis of the proposed algorithm, the adaptive pole placement problem is reduced to a controller determination based on the well-known Ackermanns’ formula. Known adaptive control schemes usually resort to the computation of dynamic controllers through the solution of polynomial Diophantine equations, thus introducing high-order exogenous dynamics in the control loop. Moreover, in many cases, this solution might yield an unstable controller, and the overall adaptive scheme is then unstable with unstable compensators because their outputs are unbounded. The proposed control strategy avoids these problems, since here gain controllers essentially need to be designed. Moreover, persistency of excitation and, therefore, parameter convergence, of the continuous-time plant is provided without making any assumption either on the existence of specific convex sets in which the estimated parameters belong or on the coprimeness of the polynomials describing the ARMA model, or finally on the richness of the reference signals, as compared to known adaptive pole placement schemes.