Discrete-time Adaptive Sliding Mode Control Research Articles

Guided Rocket Control System Design Based on Discrete-Time Adaptive Sliding Mode

The discrete-time adaptive sliding mode controller for spinning rockets in presence of parameter error is proposed. Considering the nonlinear characteristics for the system, input-output feedback linearization is utilized to transform the system model into two standard form subsystems. Then a discrete-time controller for guided rockets is designed based on discrete-time sliding mode control principle. In order to diminish the switch width of the discrete-time sliding mode system corresponding to parameter error, a dead-zone parameter adaptive law is designed. The stability of the uncertain closed-loop system is proved by Lyapunov theory, which make the controller have high robustness. Simulation result indicates that the proposed controller is robust with respect to large aerodynamic parametric uncertainty, and has excellent dynamic tracking performance.

Discrete-time adaptive sliding mode control for uncertain systems based on multi-rate output measurement

This article presents the design of a discrete-time adaptive sliding mode control (SMC) for uncertain systems using the noisy multi-rate output measurement. It is assumed that the dynamic systems are described by a discrete-time state equation with mismatched uncertainties. The proposed discrete-time adaptive SMC is composed of the equivalent and the nonlinear switching controls, and it is derived based on a new sliding surface. A new least squares estimator (LSE) to take the estimates for the un-measurable states and the uncertainties is designed without the information of the statistics for the measurement noises and the initial state. In the design of the proposed discrete-time adaptive SMC, the un-measurable states and the uncertainties are, respectively, replaced as their estimates obtained from the proposed LSE, and the sliding coefficient matrices are selected such that the states for the systems are ultimately bounded, and the effect of the external disturbances to give the states is reduced as small as possible. The effectiveness of the proposed method is indicated through the simulation experiment in a simple system.

Discrete-time adaptive sliding mode controller for vehicle steering systems with preview

This paper presents the design of a vehicle steering system with preview for a vehicle model subject to an uncertain side aerodynamic force by the crosswind disturbance. The steering control with preview is automatically implemented by steering the angles of the front/rear wheels based on the discrete-time adaptive sliding mode controller (SMC). It is assumed that the measurement of the states is taken by the measurement constraint and the contamination with independent random noises. The estimates for the unmeasurable states and the uncertainty characterizing the side aerodynamic force are respectively obtained by the weighted least squares estimator using a set of noisy measurements, and the proposed discrete-time adaptive SMC is designed on the basis of the information of the estimates. The simulation result indicates that the proposed vehicle steering system with preview is very effective in the system performance and the practical implementation.

DISCRETE-TIME SLIDING-MODE WMR CONTROL BASED ON PARAMETER IDENTIFICATION

In this paper a discrete-time adaptive sliding mode controller for wheeled mobile robots (WMR) is presented. The dynamical model with time-varying mass has been taken into account. The sliding-mode controller has designed on two components, corresponding to angular and position motion, respectively. In order to accomplish the robustness against parameter uncertainties (robot mass and moment of inertia), an on-line closed loop identification scheme is proposed. In both, angular and position motion controllers, on-line estimation of parameters, which depend on robot mass, is used.

Discrete-time adaptive sliding mode control of a linear system in statespace form

A discrete-time adaptive sliding mode controller for linear systems represented by the state space is presented. The controller is developed using the delta operator, which is better for approximating continuous-time systems than the shift operator. The use of the delta model allows the selection of the sliding surface to be similar to that for the continuous-time case. It is shown that the adaptive control algorithm leads to a stable closed-loop system. Simulation results are presented to illustrate the features of the proposed control scheme.

Discrete-time adaptive sliding mode power system stabilizer with only input/output measurements

In this paper a discrete-time adaptive sliding mode control method is newly developed and applied to the power system stabilization problem. A controllable canonical form of state space realization is constructed using the parameters identified by the on-line recursive least squares method and the system state is estimated from the input/output measurements and the simple state transformations. The identified parameters and the estimated state are then used by the discrete-time sliding mode control, which is suitable for the digital equipment. The most important advantage of the proposed power system stabilizer (PSS) is that it is able to maintain its regulating performance with a slower sampling period than that of the conventional sliding mode PSS because it is developed in a pure discrete-time domain. Another advantage of the proposed PSS is that it needs neither a mathematical model of the power system nor the full-state measurements because they are identified through on-line identifications. Several computer simulations for the linear power system are performed to verify the performance of the proposed PSS. In the computer simulations for various circumstances which are probable in a power system are considered, such as transitions of the active and reactive powers, change of parameters of the synchronous machine, line-to-ground faults and measurement noise. As a result, a new power system stabilizer which can operate in a wide range of operating conditions and can overcome various disturbances and measurement noises is proposed.