Branislava Perunicic-Drazenovic

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.

A sliding mode based direct power control of three-phase grid-connected multilevel inverter

This paper presents an approach to Direct Power Control (DPC) of a three-phase grid connected three level neutral-point clamped inverter. The presented approach can be extended to other topologies of multilevel inverters. The proposed DPC strategy is based on the Sliding Mode Control (SMC). The active and reactive power are directly controlled by three-level inverter switching states using the value of the delivered power error calculated from previous samples of three phase voltages and currents. An optimal control vector defined in dq reference frame minimizing the ripple is obtained using predicted values of three phase currents. An appropriate switching sequence is generated for each optimal vector using direct and indirect way. In the direct way the switching vector the nearest to the optimal control vector, and the direct way uses space vector modulation. The proposed strategy is robust to system parameters variations. The major advantage of proposed approach is its simple analog/digital control implementation. Moreover, PID controllers, look-up tables, and pulse-width modulators are not necessary. The designed control system is tested on a simulation model of a three-level neutral-point clamped multilevel inverter. Simulation results of a three-level neutral-point clamped multilevel inverter topology confirm the design aims.

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

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

Discrete-time sliding mode controlled positional system with two-scale reaching law and integral action

This paper investigates the effects of signal quantization and velocity estimation on the quality of the discrete-time sliding mode (DSM) in a positional servo-system. Velocity estimation is based on a simple backward finite difference method using the measured quantizied discrete-time position samples. It is shown that such introduced and amplified measurement noise degrades sliding motion into the quasi-sliding mode and threatens to provoke chattering. Furthermore, a DSM control algorithm is proposed, which provides satisfactory performance under these conditions. To avoid chattering, system trajectories are slowed down near the sliding surface by dividing the state space into the fast and slow convergence zones. In the slow zone an additional integral action is employed to secure convergence under action of disturbances. The proposed DSM controller has been experimentally tested in an induction motor position control.

New VSC based finite time control of LTI systems

This paper proposes a finite time control for a class of linear time invariant multi-input continuous-time (CT) and discrete-time (DT) controllable systems. The main idea is to reduce the system order to zero, by using higher sliding control which drives states to origin in finite time. The control scheme is fully decentralized and differentiators are not needed for control realization. The CT reaching control uses the quasi-continuous control. For DT systems a new type of order reducing control named multi-step equivalent control is proposed. This control annihilates both the switching functions and states in a finite number of discrete time units, resulting in a dead-beat control.

Integral Sliding Manifold Design for Linear Systems With Additive Unmatched Disturbances

This note offers an integral sliding manifold design method for linear systems that minimizes the impact of unmatched constant external disturbances. System sensitivity upon an unmatched disturbance vector is assessed by the steady-state dependent criterion function. The derived procedure easily finds a unique integral sliding manifold that minimizes a quadratic optimization criterion. Applicability of this method in case of slowly-varying disturbances is supported by determining disturbance frequency limit that guarantees satisfactory performance. The proposed approach has been demonstrated on a numerical example and verified by simulations.