Boban Veselic

High-Performance Position Control of Induction Motor Using Discrete-Time Sliding-Mode Control

A new way of induction-motor position control for high-performance applications is developed in this paper using discrete-time sliding-mode (DSM) control. In addition to the main DSM position controller, the proposed control structure includes an active disturbance estimator (ADE), in which a passive filter is replaced by another DSM-controlled subsystem, in order to improve system robustness and accuracy. Furthermore, the application of an ADE makes possible the design of both controllers using the knowledge of the nominal system only. Experiments have verified high efficiency of the proposed servo system under the influence of large parameter perturbations and external disturbances in the presence of unmodeled dynamics.

Improved Discrete-Time Sliding-Mode Position Control Using Euler Velocity Estimation

This paper presents a design of digitally controlled positional systems with Euler velocity estimation within the framework of the discrete-time sliding mode (DSM). The effects of quantization and simple velocity estimation on DSM quality are analyzed. It is shown that the introduced and amplified quantization noise degrades sliding motion into the quasi-sliding mode and threatens to provoke chattering. Furthermore, a new DSM control algorithm is proposed, featuring a two-scale reaching law and a supplemental integral action. This algorithm avoids chattering and provides excellent performance. The developed DSM controller has been experimentally tested in an induction motor position control.

Sampled Data Quasi-Sliding Mode Control Strategies

Sampled-data (SD) variable structure control systems (VSCS) with quasi-sliding mode (QSM) are treated in this paper as a logical extension of VSCS with ideal sliding mode (SM). The most of well-known SD QSM control algorithms are derived by starting from reaching law approach. The problems of robustness to uncertainties, loads and unmodeled inertial dynamics are considered and some methods to solve these problems are presented. An example that illustrates SD QSM VSCS properties is given.

Discrete-Time Velocity Servo System Design Using Sliding Mode Control Approach With Disturbance Compensation

This work presents a new approach to high performance velocity servo system design. The approach is based on a discrete-time sliding mode (DSM) control with disturbance compensation. For the purpose of design, the controlled plant is approximated by first-order model. The traditional, as well as the integral type of DSM control is considered. The disturbance compensator is based on the fact that the matched disturbances are directly reflected in the previous value of the switching function. In this paper, slow varying disturbances are estimated by a parallel connection of first- and second-order estimators. The integral type of DSM velocity servo system with such combined compensator can track references and significantly reject bounded disturbances, both up to cubic parabola type. The proposed control system is chattering-free. Theoretically obtained results are verified by simulations and experiments.

Disturbance compensation in digital sliding mode

This paper proposes a new approach for slow and matched disturbance suppression in digital sliding mode. The previous value of disturbance is extracted from switching function and used to make disturbance estimation, and later used in control to cancel disturbance effects. The control function is linear in state and in disturbance estimate. It may be considered chattering free since its value is zero in equilibrium if there are no disturbances.

Comprehensive Approach to Sliding Mode Design and Analysis in Linear Systems

This chapter considers the design of reduced and integral sliding mode (SM) dynamics for state space systems. The prescribed sliding mode dynamics are selected to have either a desired spectrum or optimal behavior in the linear quadratic regulator (LQR) sense. Due to the operator representation of the system equations, separate treatment of the discrete time (DT) and the continuous time (CT) cases is not needed. Fully decentralized design of the control used to satisfy the reachability problem is possible using the obtained sliding subspaces. For the sake of straightforward analysis of the SM dynamics, a new way to obtain the SM equation, based on singular value decomposition (SVD), is also provided. Algorithms are implemented in MATLAB. Simulations illustrating the usefulness of the developed design method conclude the chapter.

Digitally controlled sliding mode based servo-system with active disturbance estimator

This paper considers the design of robust servo system for accurate tracking of complex referent signals in the presence of internal and external disturbances. Discrete-time sliding mode tracking controller is employed in servo-system design. In order to improve tracking accuracy, application of active disturbance estimator is suggested. The same sliding mode controller, designed for reference tracking of nominal system, is identically implemented in the control subsystem within the estimator. The overall servo-system exhibits high tracking accuracy under action of parameter uncertainties and external disturbances. Experimental results confirm the effectiveness of the proposed servo-system structure

Direct Power Control for various topologies of three phase grid-connected Voltage Sources Converters using Sliding Mode Control

This paper presents a new approach to Direct Power Control (DPC) strategy using Space Vector Modulation (SVM) for the three-phase grid connected Voltage Source Converter (VSC) in the Renewable Energy Sources (RESs). The proposed DPC strategy is based on the Sliding Mode Control (SMC) and it is implemented in the dq reference frame. The active and reactive powers are directly controlled by VSC switching states selection based on the instantaneous value of the delivered power error. This strategy may be implemented to various VSC topologies. Moreover, linear controllers and modulators are not necessary. The aim of the control strategy is to inject maximal available active power and a controlled amount of reactive power into grid. The strategy is tested on a simulation model of a multilevel VSC (ML-VSC). Simulation results of the tested VSC topology and harmonic analysis of the output signals are presented at the end.

Digital sliding mode control design based on I/O models of nonlinear plants

The paper deals with the design of digital sliding mode controllers using only input and output sequences of plant. Two approaches are considered. The first one is based on the sliding mode based generalized minimum variance control implemented on the linearized plant model, whereas the second one utilizes the similar idea from the previous method modified for and applied on the discrete-time nonlinear model of the plant. The proposed algorithms are presented and tested by digital simulation on an example of inverted pendulum control

Sliding mode based harmonic oscillator synchronization

This paper deals with the synchronization problem of harmonic oscillatory systems, such as two- and three-phase harmonic oscillators. Synchronization between referent and controlled harmonic oscillators, based on amplitude and phase control, is pursued by employing a variable structure control system. Synchronization is achieved by organizing sliding mode along the intersection of two appropriate nonlinear sliding surfaces, individually providing amplitude and phase identity. In case of three-phase harmonic oscillator synchronization an additional symmetry condition arises, which is handled by introduction of another sliding surface. Parameter perturbations and external disturbances are taken into consideration in control system design. Variable structure controllers for two- and three-phase synchronization are designed, which provide sliding mode along the intersection of sliding surfaces in finite time in spite of present disturbances. Ideal sliding dynamics is proved to be insensitive to internal and external disturbances resulting in an ideal harmonic response. Mathematical analysis as well as experimental and simulation results are presented.