Van Van Huynh

A multitask sliding mode control for mismatched uncertain large-scale systems

A new sliding mode control (SMC) approach, output variables only, single phase only and chattering phenomenon free, is presented for a class of mismatched uncertain large-scale systems. For a new multitask SMC, it is not required that the system states are available. Moreover, the sliding function in this study just depends on output variables. Using an exponential type sliding surface, the system states are always in the sliding mode at the beginning time t = 0. Using a newly appropriate linear matrix inequality stability conditions by the Lyapunov method are derived such that each subsystem in the new sliding mode is completely invariant to matched uncertainties. As a result, robustness of the mismatched uncertain large-scale systems can be assured throughout an entire response of the system starting from the initial time t = 0. In every subsystem, a scheme of decentralised control using only output states is proposed. In addition, a continuous controller is finally designed for chattering removal. Finally, a numerical example is used to demonstrate the efficacy of the proposed method.

Second Order Sliding Mode Control Design for Active Magnetic Bearing System

This paper presents a new second order sliding mode control to stabilze a five-degree-of-freedom (DOF) active magnetic bearing (AMB) system. The new single phase sliding surface is introduced first. Then, the continous sliding mode controller is designed to relax the chattering problems in the control input. Furthermore, since the control characteristics of the five-DOF AMB are highly non-linear and time varying, the continous sliding mode controller is proposed to further improve the control performance and increase the robustness of the five-DOF AMB system. Finally, the performance of the controller applied to the five-DOF AMB model is demonstrated through simulation works under various rotational speeds and system conditions.

Adaptive output feedback sliding mode control for time-delay systems with extended disturbance

Abstract This study proposes a new adaptive output feedback sliding mode control (SMC) for mismatched uncertain time-delay systems. First, sufficient conditions in terms of linear matrix inequalities are derived such that the equivalent reduced-order system in the sliding mode is asymptotically stable. Second, based on a new lemma and a novel adaptive law, an adaptive sliding mode controller is designed to guarantee the finite-time reachability of the system states using output feedback only. The proposed method is not limited by the following conditions: (1) the exogenous disturbances must be bounded by a known function of the outputs or by a known function of the state and delayed state variables, and (2) the norm of unmeasured states must be bounded by a constant value. As these conditions are required for the application of most existing SMC approaches for time-delay systems, the proposed approach can be applied to a more generalized system, making it a valuable contribution to the field.

Integral Sliding Mode Control Approach for 3-Pole Active Magnetic Bearing System

In this paper, a new integral sliding mode control scheme is designed for the 3-pole active magnetic bearing system. First, a new integral sliding surface is designed such that the 3-pole active magnetic bearing system in the sliding mode is asymptotically stable under certain conditions. Then, an adaptive controller is designed to solve the unknown upper bound of matched uncertainty and guarantee the reachability of the integral sliding surface. Finally, the performance of the proposed integral sliding mode controller is applied to 3-pole active magnetic bearing system to demonstrate the efficacy of the proposed method.

Adaptive Output Feedback Sliding Mode Control for Complex Interconnected Time-Delay Systems

We extend the decentralized output feedback sliding mode control (SMC) scheme to stabilize a class of complex interconnected time-delay systems. First, sufficient conditions in terms of linear matrix inequalities are derived such that the equivalent reduced-order system in the sliding mode is asymptotically stable. Second, based on a new lemma, a decentralized adaptive sliding mode controller is designed to guarantee the finite time reachability of the system states by using output feedback only. The advantage of the proposed method is that two major assumptions, which are required in most existing SMC approaches, are both released. These assumptions are (1) disturbances are bounded by a known function of outputs and (2) the sliding matrix satisfies a matrix equation that guarantees the sliding mode. Finally, a numerical example is used to demonstrate the efficacy of the method.

Output Feedback and Single-Phase Sliding Mode Control for Complex Interconnected Systems

This paper generalized a new sliding mode control (SMC) without reaching phase to solve two important problems in the stability of complex interconnected systems: (1) a decentralized controller that uses only output variables directly and (2) the stability of complex interconnected systems ensured for all time. A new sliding surface is firstly designed to construct a single-phase SMC in which the desired motion is determined from the initial time instant. A new lemma is secondly established for the controller design using only output variables. The proposed single-phase SMC and the decentralized output feedback controller ensure the robust stability of complex interconnected systems from the beginning to the end. One of the key features of the single phase SMC scheme is that reaching time, which is required in most of the existing two phases of SMC approaches to stabilize the interconnected systems, is removed. Finally, a numerical example is used to demonstrate the efficacy of the method.

Decentralized Adaptive Double Integral Sliding Mode Controller for Multi-Area Power Systems

Most of the existing results for load frequency control of multi-area interconnected power systems can only be obtained when the norm of the aggregated uncertainties is bounded by a positive constant. This condition is difficult to achieve in real multi-area interconnected power systems. In this paper, a new load frequency control (LFC) for multi-area interconnected power systems is developed based on a decentralised adaptive double integral sliding mode control technique where the above limitation is eliminated. First, an adaptive gain tuning law is adopted to estimate the unknown upper bound of the aggregated uncertainties. Second, a double integral sliding surface based adaptive sliding mode controller is proposed to improve the transient performance of the closed loop system. Simulation results show that the proposed control law results in shortening the frequency’s transient response, avoiding the overshoot, rejecting disturbance better, maintaining required control quality in the wider operating range, and being more robust to uncertainties as compared to some existing control methods.

PI Sliding Mode Control for Active Magnetic Bearings in Flywheel

This paper proposes the PI sliding mode control approach in order to control the nonlinear multiple-input-multiple-output active magnetic bearing system in flywheel. A nonlinear model of a one degree of freedom (DOF) active magnetic bearing system in flywheel obtained using Lagrange’s equation is proposed. In this model, the current in each coil is treated as a state variable and the control input is the voltage applied to each coil, this approach offers more advantages than current control input approach. The proportional and integral switching surface is constructed for active magnetic bearing system to improve system dynamic performance in reaching intervals. The robust controller is proposed by the reaching law method to assure that the rotor stays close at the desired displacement even when disturbance and dynamic effect of rotating are taken into considering.

Optimal Load Frequency Control in an Isolated Power System

The load frequency control (LFC) problem for Isolated Power System is considered from the viewpoint of optimal control theory. However, the practical implementation of the optimal controller requires the measurement of all the state variables. This is a serious limitation because of the difficulties involved in their measurement. Output feedback will allow us to design plant controllers of any desired structure. This is another reason for preferring it over full-state feedback. In the regulator problem, we are interested in obtaining good time responses as well as in the stability of the closed-loop system. Therefore, we shall select a performance criterion in the time domain. The simulation results indicate that the proposed control scheme works well. In addition, they show that the controlled system is robust to bounded input disturbances acting on the system.

Variable Structure Load Frequency Control of Power System

Power-system load-frequency control by variable structure controller is proposed. To ease the design effort and improve the performance of the controller, second order variable structure control combine with integral sliding is developed. Overall system is asymptotically stable, for all admissible system parametric uncertainties, when all the local load frequency controllers are working together. Simulations confirm that the proposed second order variable structure control can rebalance power and resynchronize bus frequencies after a disturbance with significantly improved transient performance.