Showing papers on "Sliding mode control published in 2007"

Analysis of Chattering in Systems With Second-Order Sliding Modes

Abstract: A systematic approach to the chattering analysis in systems with second-order sliding modes is developed. The neglected actuator dynamics is considered to be the main cause of chattering in real systems. The magnitude of oscillations in nonlinear systems with unmodeled fast nonlinear actuators driven by second-order sliding-mode control generalized suboptimal (2-SMC G-SO) algorithms is evaluated. Sufficient conditions for the existence of orbitally stable periodic motions are found in terms of the properties of corresponding Poincare maps. For linear systems driven by 2-SMC G-SO algorithms, analysis tools based on the frequency-domain methods are developed. The first of these techniques is based on the describing function method and provides for a simple approximate approach to evaluate the frequency and the amplitude of possible periodic motions. The second technique represents a modified Tsypkin's method and provides for a relatively simple, theoretically exact, approach to evaluate the periodic motion parameters. Examples of analysis and simulation results are given throughout this paper.

System and method for driving LED

Abstract: A system drives one or plurality of LEDs regulating their brightness by controlling LEDs average current or voltage. The system includes a switching power converter and an integrated digital regulator with at least one of electrical, thermal and optical feedbacks. The regulator is constructed as a hysteretic peak current mode controller for continuous mode of operation of the power converter. For discontinuous mode of operation of the power converter a pulse averaging sliding mode control is being used. Average LED current is measured by integrating LED pulse current at off time and hysteretically adjusting on time of the power switch. Input battery is protected from discharging at abnormally low impedance of the output.

Modeling and PD Control of a Quadrotor VTOL Vehicle

Abstract: In this paper, we present a model of a four rotor vertical take-off and landing (VTOL) unmanned air vehicle known as quadrotor aircraft. And we explained its control architecture including vision based control. Quadrotors have generated considerable interest in both the control community due to their complex dynamics and military because of their advantages over regular air vehicles. The proposed dynamical model which comprises gyroscopic effects and its control strategies can be source for future works.

LMI-Based Sliding Surface Design for Integral Sliding Mode Control of Mismatched Uncertain Systems

Abstract: We propose a linear matrix inequality (LMI)-based sliding surface design method for integral sliding-mode control of mismatched uncertain systems. The uncertain system under consideration may have mismatched norm bounded uncertainties in the state matrix as well as the input matrix. We give a sufficient condition for the existence of a sliding surface guaranteeing asymptotic stability of the full order sliding mode dynamics. We also give an LMI characterization of the sliding surface, together with an integral sliding mode control law guaranteeing the existence of a sliding mode from the initial time. Additionally, we give an LMI condition of sliding surfaces guaranteeing the alpha-stability constraint. Finally, we give a simulation result to show the effectiveness of our method

On sliding mode observers for systems with unknown inputs

Abstract: This paper considers the problem of designing an observer for a linear system subject to unknown inputs. This problem has been extensively studied in the literature with respect to both linear and nonlinear (sliding mode) observers. Necessary and sufficient conditions to enable a linear unknown input observer to be designed have been established for many years. One way to express these conditions is that the transfer function matrix between the unknown input and the measured output must be minimum phase and relative degree one. Identical conditions must be met in order to design a ‘classical’ sliding mode observer for the same problem. This paper shows how the relative degree condition can be weakened if a classical sliding mode observer is combined with sliding mode exact differentiators to essentially generate additional independent output signals from the available measurements. A practical example dedicated to actuator fault detection and identification of a winding machine demonstrates the efficacy of the approach. Copyright © 2007 John Wiley & Sons, Ltd.

Sliding Mode Control Based on Backstepping Approach for an UAV Type-Quadrotor

Abstract: In this paper; we are interested principally in dynamic modelling of quadrotor while taking into account the high-order nonholonomic constraints in order to develop a new control scheme as well as the various physical phenomena, which can influence the dynamics of a flying structure. These permit us to introduce a new state-space representation. After, the use of Backstepping approach for the synthesis of tracking errors and Lyapunov functions, a sliding mode controller is developed in order to ensure Lyapunov stability, the handling of all system nonlinearities and desired tracking trajectories. Finally simulation results are also provided in order to illustrate the performances of the proposed controller. Keywords—Dynamic modelling, nonholonomic constraints, Backstepping, Sliding mode.

Robust Fuzzy Design for Nonlinear Uncertain Stochastic Systems via Sliding-Mode Control

Abstract: This paper deals with the sliding-mode control (SMC) problem for nonlinear stochastic time-delay systems by means of fuzzy approach. The Takagi-Sugeno (T-S) fuzzy stochastic time-delay model with parametric uncertainties and unknown nonlinearities is presented. A sufficient condition for the exponential stability in mean square of the sliding motion is also derived. Moreover, it is shown that when the linear matrix inequalities (LMIs) with equality constraint are feasible, the designs of both sliding surface and sliding-mode controller can be easily obtained via convex optimization. A simulation example illustrating the proposed method is given.

Accurate Sliding-Mode Control of Pneumatic Systems Using Low-Cost Solenoid Valves

Abstract: A control law is developed for an inexpensive pneumatic motion control system using four solenoid on/off valves and a position feedback sensor. A sliding-mode approach is used, which is well known for its tolerance for system uncertainties. In contrast to previous control laws, our approach does not use pulsewidth modulation. The control law has an energy-saving mode that saves electrical power, reduces chattering, and prolongs the valve's life. Our simulation and experimental results show that the proposed tracking control law performs very well with good tracking and relatively low steady-state position errors

Sliding Mode Observer and Backstepping Control for a Quadrotor Unmanned Aerial Vehicles

Abstract: In this paper, we propose a new approach of the backstepping control running parallel with a sliding mode observer for a quadrotor unmanned aerial vehicle. The sliding mode observer works as an observer of the quadrotor velocities and estimator of the external disturbances such as wind and parameter uncertainties. The controller objective is to achieve good tracking of desired (x,y,z) absolute positions and yaw angle while keeping the stability of the pitch and roll angles, in spite of the presence of bounded external disturbances. For this reason, the observer-controller is proposed to estimate the effect of external perturbations in order to compensate them. The design methodology is based on Lyapunov stability. Simulation results show the good performances and the robustness of the proposed observer-controller.

Sliding-Mode Formation Control for Underactuated Surface Vessels

Abstract: Sliding-mode control laws for controlling multiple unmanned surface vessels in arbitrary formations are proposed. The presented formation control method uses local information as well as the planned gross motion of the formation to achieve mesh stability. A three-degree-of-freedom dynamic model has been used for the surface vessels. It is assumed that each vessel only has two actuators and the vessels are underactuated. Mesh stability and parameter uncertainty in the dynamic model and wave disturbance are considered in designing the controllers. It is shown that the internal dynamics of the underactuated system is also stable. The effectiveness and robustness of these control laws in the presence of parameter uncertainty in the dynamic model and wave disturbances and the mesh stability of the formation are demonstrated by computer simulation.

Integrated sliding mode autopilot-guidance for dual-control missiles

Abstract: An integrated autopilot and guidance algorithm is developed, using the sliding mode control approach, for a missile with forward and aft control surfaces. Based on guidance considerations, the zero efiort miss (ZEM), encountered in difierential games guidance solutions, is used as one of the sliding variables in the proposed control scheme. The dual control conflguration provides an additional degree of freedom in the integrated design. This degree of freedom is exploited by introducing a second sliding surface, selected based on autopilot design considerations. Restraining the system to the ZEM surface guarantees zero miss distance, while remaining on the second surface provides a damped response. The performance of the integrated dual controller is evaluated using a two-dimensional nonlinear simulation of the missile lateral dynamics and relative kinematics, assuming flrst order dynamics for the target evasive maneuvers. The simulation results validate the design approach of using ZEM and the ∞ight-control based sliding surfaces to attain high accuracy interceptions.

Robust Multiple Frequency Trajectory Tracking Control of Piezoelectrically Driven Micro/Nanopositioning Systems

Abstract: A novel modeling and control methodology is proposed in this paper for real-time compensation of nonlinearities along with precision trajectory control of piezoelectric actuators in various range of frequency operation. By integrating a modified Prandtl-Ishlinskii hysteresis operator with a second-order linear dynamics, a nonlinear dynamic model and an inverse feedforward controller are developed and experimentally validated for a piezoelectrically driven nanopositioning stage. This modeling and control framework, however, lacks the accuracy due to the hysteresis model limitation, parametric uncertainties, and ever present unmodeled dynamics. Utilizing the sliding mode control strategy coupled with a perturbation estimation technique, a robust controller is then proposed for trajectory tracking of the actuator displacement. The controller gains are adjusted based on an intelligent comparison of the dynamic model and the control law. Eventually, the performance of the proposed controller is verified for the nanopositioning stage which is equipped with a high resolution capacitive position sensor. Experimental results demonstrate that the controller is capable of precisely tracking triangular and multiple frequency sinusoidal trajectories, which are common practices in many scanning probe microscopy systems.

Self-Organizing Adaptive Fuzzy Neural Control for a Class of Nonlinear Systems

Abstract: This paper proposes a self-organizing adaptive fuzzy neural control (SAFNC) via sliding-mode approach for a class of nonlinear systems. The proposed SAFNC system is comprised of a computation controller and a supervisory controller. The computation controller including a self-organizing fuzzy neural network (SOFNN) identifier is the principal controller. The SOFNN identifier is used to online estimate the controlled system dynamics with the structure and parameter learning phases of fuzzy neural network (FNN), simultaneously. The structure learning phase possesses the ability of online generation and elimination of fuzzy rules to achieve optimal neural structure, and the parameter learning phase adjusts the interconnection weights of neural network to achieve favorable approximation performance. The supervisory controller is used to achieve the L2-norm bound tracking performance with a desired attenuation level. Moreover, all the parameter learning algorithms are derived based on Lyapunov function candidate, thus the system stability can be guaranteed. Finally, simulation results show that the SAFNC can achieve favorable tracking performances.

Numerical Optimization-Based Extremum Seeking Control With Application to ABS Design

Abstract: Extremum seeking control (ESC) schemes based on numerical optimization are proposed in this paper. The extremum seeking problem is treated as an optimization with dynamic system constraints. The numerical optimization-based extremum seeking control scheme is first applied to linear time-invariant (LTI) systems, then it is extended to a class of feedback linearizable systems. The convergence of the ESC scheme is guaranteed by the numerical optimization algorithm and state regulation. The robustness of line search methods and trust region methods is studied, which provides further flexibility for the design of robust extremum seeking controller. Simulation study of antilock braking systems (ABS) design via extremum seeking control is addressed

Enhanced sliding mode motion tracking control of piezoelectric actuators

Abstract: This paper proposes an enhanced sliding mode motion tracking control methodology for piezoelectric actuators to track desired motion trajectories. The proposed control methodology is established to accommodate parametric uncertainties, nonlinearities including the hysteresis effect, and other un-modelled disturbances, without any form of feed-forward compensation. The fundamental concept in this control strategy relies on the specification of a target performance and the formulation of an enhanced sliding mode control law based on the variable structure control approach. The control methodology ensures the convergence of the position tracking error to zero in the presence of the aforementioned conditions. The stability of the control methodology is proven theoretically and a precise tracking ability is demonstrated in the experimental study. One of the most important advantages of this control methodology is that the approach requires only a knowledge of the estimated system parameters together with their corresponding bounds and the bound of the non-linearities and disturbances in the physical realisation. Being capable of motion tracking, the proposed enhanced sliding mode control methodology is very attractive in the field of micro/nano manipulation through which high-precision piezoelectric actuation control applications can be realised.

Research and development on theory and algorithms of sliding mode control

Abstract: According to the development of sliding mode control(SMC)in recent years,the SMC domain is character-ized by eighteen directions.These directions are chattering free of SMC,quasi SMC,trending law SMC,discrete SMC,adaptive SMC,SMC for mismatched uncertain systems,SMC for nonlinear systems,time-delay SMC,terminal SMC,global robust SMC,sliding mode observer,neural SMC,fuzzy SMC,dynamic SMC,integral SMC and SMC for stochastic systems,etc.The evolution of each direction is introduced and analyzed.Finally,further research directions are discussed in detail.

Fuzzy–Neural Sliding-Mode Control for DC–DC Converters Using Asymmetric Gaussian Membership Functions

Abstract: A fuzzy-neural sliding-mode (FNSM) control system is developed to control power electronic converters. The FNSM control system comprises a neural controller and a compensation controller. In the neural controller, an asymmetric fuzzy neural network is utilized to mimic an ideal controller. The compensation controller is designed to compensate for the approximation error between the neural controller and the ideal controller. An online training methodology is developed in the Lyapunov sense; thus, the stability of the control system can be guaranteed. Finally, to investigate the effectiveness of the FNSM control scheme, it is applied to control a pulsewidth-modulation-based forward dc-dc converter. Experimental results show that the proposed FNSM control system is found to achieve favorable regulation performances even under input-voltage and load-resistance variations

Actuator Failure Identification and Compensation Through Sliding Modes

Abstract: The actuator failure compensation problem is addressed in this brief. It is considered an uncertain linear plant, which is supposed to undergo unknown failures causing the plant input components to be stuck at some uncertain but bounded time functions. A sliding-mode-based control policy is presented, guaranteeing the detection of the fault and the identification of the failed component by means of a suitable test input. Once the failed component has been identified, the control law is reconfigured, redistributing the control activity among the controllers still working. The proposed controller has been tested by simulation on a benchmark problem

Experimental Comparison of Position Tracking Control Algorithms for Pneumatic Cylinder Actuators

Abstract: Many researchers have investigated pneumatic servo positioning systems due to their numerous advantages: inexpensive, clean, safe, and high ratio of power to weight. However, the compressibility of the working medium, air, and the inherent nonlinearity of the system continue to make achieving accurate position control a challenging problem. In this paper, two control algorithms are designed for the position tracking problem and their experimental performance is compared for a pneumatic cylinder actuator. The first algorithm is sliding-mode control based on a linearized plant model (SMCL) and the second is sliding-mode control based on a nonlinear plant model (SMCN). Extensive experiments using different payloads (1.9, 5.8, and 10.8 kg), vertical and horizontal movements, and move sizes from 3 to 250 mm were conducted. Averaged over 70 experiments with various operating conditions, the tracking error for SMCN was 18% less than with SMCL. For a 5.8-kg payload and a 0.5-Hz 70-mm amplitude, sine wave reference trajectory, the root-mean-square error with SMCN was less than 0.4 mm for both vertical and horizontal motions. This tracking control performance is better than those previously reported for similar systems.

Sliding Mode Power Control of Variable Speed Wind Energy Conversion Systems

Abstract: This paper addresses the problem of controlling power generation in variable speed wind energy conversion systems (VS-WECS). These systems have two operation regions depending on wind turbines tip speed ratio. They are distinguished by a minimum phase behavior in one of these regions and a nonminimum phase in the other one. A sliding mode control strategy is then proposed to ensure stability in both operation regions and to impose the ideal feedback control solution despite of model uncertainties. The proposed sliding mode control strategy presents attractive features such as robustness to parametric uncertainties of the turbine and the generator as well as to electric grid disturbances. The proposed sliding mode control approach has been simulated on a 1.5-MW three-blade wind turbine to evaluate its consistency and performance. The next step was the validation using the NREL (National Renewable Energy Laboratory) wind turbine simulator FAST (Fatigue, Aerodynamics, Structures and Turbulence code). Both simulation and validation results show that the proposed control strategy is effective in terms of power regulation. Moreover, the sliding mode approach is arranged so as to produce no chattering in the generated torque that could lead to increased mechanical stress because of strong torque variations.

Multirate Output Feedback Based Robust Quasi-Sliding Mode Control of Discrete-Time Systems

Abstract: Over the last few years, the research on discrete-time sliding mode control has received a considerable attention. Unlike its continuous-time counterpart, discrete-time sliding mode control is not invariant in general. In this note, an algorithm is presented for robust discrete-time sliding mode control using the concept of multirate output feedback

Network-Based Fuzzy Decentralized Sliding-Mode Control for Car-Like Mobile Robots

Abstract: In this paper, the trajectory tracking of a car-like mobile robot (CLMR) using network-based fuzzy decentralized sliding-mode control (NBFDSMC) is developed. The scaling factors and the coefficients of the sliding surface for the control of the steering angle and forward-backward velocity of a CLMR are adopted by that for the control of two motors. Due to the delay transmission of a signal through an Internet and wireless module, a revision of fuzzy decentralized sliding-mode control (FDSMC) with suitable sampling time (i.e., NBFDSMC) is accomplished by the quality-of-service (QoS). The proposed control can track a reference trajectory without the requirement of a mathematical model. Only the information of the upper bound of system knowledge (including the dynamics of the CLMR, the delay feature of Internet network, and wireless module) is required to select the suitable scaling factors and coefficients of sliding surface such that an excellent performance is obtained. In addition, the stability of the closed-loop system in the presence of time-varying delay is addressed. Finally, a sequence of experiments including the control of unloaded CLMR and the trajectory tracking of CLMR is carried out to consolidate the usefulness of the proposed control system

Exact state estimation for linear systems with unknown inputs based on hierarchical super‐twisting algorithm

Abstract: A robust hierarchical observer is designed for linear time invariant systems with unknown bounded inputs under conditions of strong observability, providing exact state estimation. The main condition for designing the state estimator is the, so-called, strong observability condition. The supertwisting (second-order sliding mode) algorithm is used in each step of the hierarchy; the continuity of the supertwisting output injection allows to reconstruct a vector formed by some full column rank matrix premultiplied by the state vector, and that vector is obtained in a finite time and without any sort of filtration. For the case when the unknown inputs are considered as constant uncertain parameters, the continuous version of the least-square method is developed. Two numerical examples illustrate the efficiency of the suggested technique. Copyright © 2007 John Wiley & Sons, Ltd.

FPGA-Based Adaptive Backstepping Sliding-Mode Control for Linear Induction Motor Drive

Abstract: A field-programmable gate array (FPGA)-based adaptive backstepping sliding-mode controller is proposed to control the mover position of a linear induction motor (LIM) drive to compensate for the uncertainties including the friction force. First, the dynamic model of an indirect field-oriented LIM drive is derived. Next, a backstepping sliding-mode approach is designed to compensate the uncertainties occurring in the motion control system. Moreover, the uncertainties are lumped and the upper bound of the lumped uncertainty is necessary in the design of the backstepping sliding-mode controller. However, the upper bound of the lumped uncertainty is difficult to obtain in advance of practical applications. Therefore, an adaptive law is derived to adapt the value of the lumped uncertainty in real time, and an adaptive backstepping sliding-mode control law is the result. Then, an FPGA chip is adopted to implement the indirect field-oriented mechanism and the developed control algorithms for possible low-cost and high-performance industrial applications. The effectiveness of the proposed control scheme is verified by some experimental results. With the adaptive backstepping sliding-mode controller, the mover position of the FPGA-based LIM drive possesses the advantages of good transient control performance and robustness to uncertainties in the tracking of periodic reference trajectories.