Alireza Nasiri

Adaptive sliding mode control for a class of MIMO nonlinear systems with uncertainties

Abstract This paper proposes an adaptive scheme of designing sliding mode control (SMC) for affine class of multi-input multi-output (MIMO) nonlinear systems with uncertainty in the systems dynamics and control distribution gain. The proposed adaptive SMC does not require any a priori knowledge of the uncertainty bounds and therefore offers significant advantages over the non-adaptive schemes of SMC design. The closed loop stability conditions are derived based on Lyapunov theory. The effectiveness of the proposed approach is demonstrated via simulations considering an example of a two-link robot manipulator and has been found to be satisfactory.

An Adaptive Two-Level Quantizer for Networked Control Systems

This brief proposes a novel adaptive two-level quantizer, which generates 1-b per sample and can be used for a class of industrial networked control systems (NCSs). The adaptive quantizer is introduced to automatically estimate the input of the quantizer using equivalent control-based sliding mode control. The stability condition of the proposed quantizer is derived analytically with the help of a sliding-mode analysis. The effectiveness of the proposed quantized NCS is illustrated experimentally by designing a quantized feedback controller to control the position of a dc motor, where signals with 1-b per sample are utilized to interconnect the controller with the plant. Simulation results from a laboratory prototype illustrate that the proposed quantizer with the feedback controller controls the system effectively, introduces less quantization noise, and minimizes the data rate.

Estimation of actuator and sensor faults for nonlinear systems using a descriptor system approach

This paper addresses the problem of simultaneously estimating actuator and sensor faults of Lipschitz nonlinear systems with non-parametric uncertainties. The proposed fault estimation scheme initially takes sensor faults as auxiliary states and an augmented descriptor system is constructed. By designing a modified proportional and derivative (PD) observer with an adaptive law for this system, the estimation of the original system states, sensor faults and actuator faults can be obtained simultaneously. The sufficient condition for stability of the proposed observer with ℋ∞ performance has been derived based on Lyapunov theory. The stability condition is expressed as Linear Matrix Inequality (LMI) optimization problem for minimizing the ℋ∞ norm of transfer matrix between the estimation error and uncertainties, which outlines a constructive design procedure for observer parameters. It is shown from the simulation that the proposed approach is capable of successfully estimating states and faults not only for nonlinear state-space systems, but also for nonlinear descriptor systems.

The dynamic behaviour of data-driven Δ-M and ΔΣ-M in sliding mode control

ABSTRACT In recent years, delta (Δ-M) and delta-sigma modulators (ΔΣ-M) are increasingly being used as efficient data converters due to numerous advantages they offer. This paper investigates various dynamical features of these modulators/systems (both in continuous and discrete time domain) and derives their stability conditions using the theory of sliding mode. The upper bound of the hitting time (step) has been estimated. The equivalent mode conditions, i.e. where the outputs of the modulators are equivalent to the inputs, are established. The results of the analysis are validated through simulations considering a numerical example.

Passive actuator fault tolerant control for a class of MIMO nonlinear systems with uncertainties

ABSTRACT Fault tolerant control of affine class of multi-input multi-output (MIMO) nonlinear systems has not received considerable attention of researchers compared to other class of nonlinear systems. Therefore, this paper proposes an adaptive passive fault tolerant control method for actuator faults of affine class of MIMO nonlinear systems with uncertainties using sliding mode control . The actuator fault is represented by a multiplicative factor of the control signal which reflects the loss of actuator effectiveness. The design of the controller is based on the assumption that the maximum loss level of the actuator effectiveness is known. Furthermore, since the proposed controller is adaptive, it does not require any a-priori knowledge of the uncertainty bounds. The closed-loop stability conditions of the controller are derived based on Lyapunov theory. The effectiveness of the proposed controller is demonstrated considering two examples: a two degree of freedom helicopter and a two-link robot manipulator and has been found to be satisfactory.

Robust fault estimation of nonlinear systems using SOS approach

This paper proposes a new method of robust fault estimation (FE) for a class of nonlinear systems represented by polynomial fuzzy models. Existing results on these systems essentially focus on fault detection and isolation (FDI) approach. The sufficient conditions for designing gains of the estimator are established via Lyapunov theory, which are formulated in terms of polynomial matrix inequalities (PLMIs). These PLMIs are solved using sum of squares (SOS) approach and estimator gains are calculated using SOSTOOLS toolbox in Matlab. The effectiveness of the proposed approach has been illustrated considering a numerical example and has been found to be satisfactory.

Passive actuator fault tolerant control for a class of MIMO non-linear systems with uncertainties

Fault Tolerant Control of affine class of MIMO non-linear systems have not received considerable attention of researchers compared to other class of non-linear systems. Therefore, this paper proposes an adaptive passive fault tolerant control method for actuator faults of affine class of MIMO nonlinear systems with uncertainties using sliding mode control. The actuator fault is represented by a multiplicative factor of the control signal which reflects the loss of actuator effectiveness. The design of the controller is based on the assumption that the maximum loss level of the actuator effectiveness is known. Further, since the proposed controller is adaptive, it does not require any a priori knowledge of the uncertainty bounds. The closed loop stability conditions of the controller are derived based on Lyapunov theory. The effectiveness of the proposed controller is demonstrated considering an example of a two degree of freedom helicopter and has been found to be satisfactory.

Stabilisation of discrete-time polynomial fuzzy systems via a polynomial lyapunov approach

ABSTRACT This paper deals with the problem of designing a controller for a class of discrete-time nonlinear systems which is represented by discrete-time polynomial fuzzy model. Most of the existing control design methods for discrete-time fuzzy polynomial systems cannot guarantee their Lyapunov function to be a radially unbounded polynomial function, hence the global stability cannot be assured. The proposed control design in this paper guarantees a radially unbounded polynomial Lyapunov functions which ensures global stability. In the proposed design, state feedback structure is considered and non-convexity problem is solved by incorporating an integrator into the controller. Sufficient conditions of stability are derived in terms of polynomial matrix inequalities which are solved via SOSTOOLS in MATLAB. A numerical example is presented to illustrate the effectiveness of the proposed controller.

Robust control of wireless power transfer system

In recent years, wireless power transfer systems have successfully been used in various industrial applications due to their contactless power transfer feature. However, these systems behave as higher order resonant networks and hence are highly sensitive to changes in system parameters. Traditional PID controllers often fail to maintain satisfactory power regulation in the presence of parametric uncertainties which include load and circuit parameter variations, variations in magnetic coupling between the primary and secondary coils. To overcome these problems, this paper designs a robust H∞ output feedback controller for a bi-directional inductive power transfer system. The control design is carried out following Ricatti approach. Simulations are conducted to verify the power regulation performance of the proposed controller and it is compared with a classical PID controller. The results show that the H∞ output feedback controller could successfully regulate the power in both directions in the presence of large uncertainties in various circuit parameters.

Fault tolerant H™ fuzzy-dynamic output feedback control of nonlinear systems with actuator faults: An LMI approach

This paper addresses the problem of robust fuzzy dynamic output feedback control of a nonlinear discrete time system described by a Takagi -Sugeno fuzzy model. It is assumed that the system is subjected to actuator fault. First, the closed-loop faulty dynamic model of the system and the fuzzy dynamic output feedback controller are introduced. Then, the stability conditions are established via Lyapunov theory, which are formulated in terms of linear matrix inequalities to solve the problem. Finally, a numerical example is presented to illustrate the effectiveness of the proposed controllers.