HIGHER-ORDER SLIDING MODE DYNAMICS DESIGN FOR A CLASS OF SINGLE-INPUT LINEAR SYSTEMS

The paper considers a higher-order sliding mode dynamics design in a class of single-input linear systems having the invertible system matrix. The proposed sliding manifold selection method simultaneously provides a necessary relative degree of the sliding variable for a specific sliding mode order and the desired system dynamics after establishing that sliding mode. It is shown that the found unique solution satisfies these requirements. The theoretically obtained result is validated through a numerical example and illustrated by digital simulations

OPTIMAL SLIDING MANIFOLD DESIGN FOR LINEAR SYSTEMS SUBJECTED TO A CLASS OF UNMATCHED DISTURBANCES

This paper offers the optimal sliding manifold design for the traditional sliding mode and integral sliding mode control of linear systems that minimizes the impact of unmatched constant or slowly-varying external disturbance vector. System sensitivity upon the unmatched disturbances is assessed by the steady-state dependent criterion function. The ability and efficiency of the adopted control strategies in solving the given optimization problem are analyzed. The proposed approach has been demonstrated and verified on numerical examples by computer simulations

DISCRETE TIME QUASI-SLIDING MODE-BASED CONTROL OF LCL GRID INVERTERS

Application of a discrete time (DT) sliding mode controller (SMC) in the control structure of the primary controller of a three-phase LCL grid inverter is presented. The design of the inverter side current control loop is performed using a DT linear model of the grid inverter with LCL filter at output terminals. The DT quasi-sliding mode control was used due to its robustness to external and parametric disturbances. Additionally, in order to improve disturbance compensation, a disturbance compensator is also implemented. Also, a specific anti-windup mechanism has been implemented in the structure of the controller to prevent large overshoots in the inverter response in case of random disturbances of grid voltages, or sudden changes in the commanded power. The control of the grid inverter is realized in the reference system synchronized with the voltage of the power grid. The development of the digitally realized control subsystem is presented in detail, starting from theoretical considerations, through computer simulations to experimental tests. The experimental results confirm good static and dynamic performance

VOLTAGE SAG SENSITIVITY OF INDUSTRIAL VECTOR CONTROLLED INDUCTION MOTOR DRIVES – A COMPARATIVE STUDY

Sensitivity of adjustable speed drives (ASDs) on voltage sag events represents one of the most challenging problems in modern industrial facilities. In this paper, a comprehensive experimental verification of vector-controlled ASDs is conducted under the most-frequent sag types. The obtained results are faced with static and dynamic requirements in speed and torque controlled applications. Besides influence of DC-link parameters, selection of the applied control method and the controller settings can have crucial impact on performance deterioration. Examined industrial ASDs exhibited voltage sag susceptibility with fault error codes under the deeper voltage sags, while under the voltage sags with residual voltage above under-voltage limit they showed speed degradation

Discrete–Time Sliding Mode Control of Linear Systems with Input Saturation

The paper proposes a discrete-time sliding mode controller for single input linear dynamical systems, under requirements of the fast response without overshoot and strong robustness to matched disturbances. The system input saturation is imposed during the design due to inevitable limitations of most actuators. The system disturbances are compensated by employing nonlinear estimation by integrating the signum of the sliding variable. Hence, the proposed control structure may be regarded as a super-twisting-like algorithm. The designed system stability is analyzed as well as the sliding manifold convergence conditions are derived using a discrete-time model of the system in the δ-domain. The results obtained theoretically have been verified by computer simulations

Discrete-time sliding mode control of linear systems with input saturation

The paper proposes a discrete-time sliding mode controller for single input linear dynamical systems, under requirements of the fast response without overshoot and strong robustness to matched disturbances. The system input saturation is imposed during the design due to inevitable limitations of most actuators. The system disturbances are compensated by employing nonlinear estimation by integrating the signum of the sliding variable. Hence, the proposed control structure may be regarded as a super-twisting-like algorithm. The designed system stability is analyzed as well as the sliding manifold convergence conditions are derived using a discrete-time model of the system in the δ-domain. The results obtained theoretically have been verified by computer simulations