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The method of the synthesis of multi-channel decentralized variable structure system for the control of quadrotor spatial motion is developed in this paper. The control law based on the formation of the sliding mode in the separate subsystems of each coordinates control is formed. Each subsystem includes two loops for Cartesian coordinates and relevant Euler angles control. The conditions of the existence of stable sliding mode are obtained. These conditions take into account essential dynamic reciprocal effect between all control channels. The application of proposed control law provides high control quality and maximal fast-action at any variations of the quadrotor parameters within given ranges. This control law does not require the identification of changing object parameters. Efficiency of synthesized control system is confirmed by numerical simulation results. The control system can be realized in the real time by simple technical means.

Typically, component-oriented acausal hybrid modeling of complex dynamic systems is implemented by specialized modeling languages. A well-known example is the Modelica language. The specialized nature, complexity of implementation and learning of such languages somewhat limits their development and wide use by developers who know only general-purpose languages. The paper suggests the principle of developing simple to understand and modify Modelica-like system based on the general-purpose programming language Python. The principle consists in: (1) Python classes are used to describe components and their systems, (2) declarative symbolic tools SymPy are used to describe components behavior by difference or differential equations, (3) the solution procedure uses a function initially created using the SymPy lambdify function and computes unknown values in the current step using known values from the previous step, (4) Python imperative constructs are used for simple events handling, (5) external solvers of differential-algebraic equations can optionally be applied via the Assimulo interface, (6) SymPy package allows to arbitrarily manipulate model equations, generate code and solve some equations symbolically. The basic set of mechanical components (1D translational “mass”, “spring-damper” and “force”) is developed. The models of a sucker rods string are developed and simulated using these components. The comparison of results of the sucker rod string simulations with practical dynamometer cards and Modelica results verify the adequacy of the models. The proposed approach simplifies the understanding of the system, its modification and improvement, adaptation for other purposes, makes it available to a much larger community, simplifies integration into third-party software.

The paper aims to the problem of an gas-turbine engine's automatic control systems (ACS GTE) reliability improvement by using of sliding modes. For meeting of heightened requirements for ACS GTE speed and control accuracy in the disturbances conditions, the use of binary systems' methodology was proposed. The binary system is a variable structure system, using a coordinate-parametric feedback (CPFB) combined with the classical principle of error-closing control. A feature of the binary system is the presence of a sliding mode. As the control object, the gas-turbine aviation engine's compressor inlet guide vanes (IGV) are considered. The main feature of IGV is the nonlinearity caused by the constructive characteristics and the effect of internal and external disturbances. The quality of the IGV control is critical for compressor operation, in particular for absence of stalling and surging effects. The binary ACS IGV was synthesized. The approbation of the CPFB with calculated parameters showed insufficient system response speed. To achieve the specified quality requirements of ACS, the coefficients of the binary automatic control system were optimized based on the numerical Monte-Carlo method using Sobol sequences. Simulating optimum ACS IGV in accordance with the selected criterion in statics and dynamics under conditions of external internal disturbances has shown that the control quality rises by 2–3 times in comparison with the industrial regulator.

In this paper, a new guidance law based on the variable structure system theory and an associated model-free target acceleration estimator are proposed. The composite guidance-estimation law is designed to intercept constant-velocity and maneuvering targets by missiles at a desired terminal impact angle. Specifically, the scenario of intercepting the targets with speed-disadvantaged missiles, which has not been studied in detail in the literature available, is considered in this paper. A multiple solution problem for the terminal impact angle and a final line-of-sight angle is clarified in this paper. To solve this problem, the generalized variable structure theory is used and an additional sliding mode surface is introduced in the proposed guidance law, by which missiles can reach a wider range of the final impact angle. In addition, the nonsingular terminal sliding mode control method is applied so that the states of the guidance dynamic system are finite time convergent. In order to intercept maneuvering targets, a Kriging-based model-free finite impulse response filter is employed. Based on this filter, this paper puts forward some improvements, including a data preprocessing method and a parameter offline tuning method by the simulated annealing algorithm. In this way, a model-free target acceleration estimator with strong practicality in engineering is proposed. The stability condition of the proposed composite guidance-estimation law is obtained via the Lyapunov theorem. Finally, simulation results in different initial intercepting scenarios are presented to validate the advantage of the proposed guidance law and target acceleration estimator.

An improved tracking technique of the reference current waveform in a shunt type active power filter is proposed in this paper using sliding mode control and feedback linearization. Feedback linearization approach helps to reduce the complexity of the controller. Excellent tracking is achieved in both for steady state and dynamic performance. A three-phase four-wire system is considered. The proposed algorithm is simulated first in MATLAB/SIMULINK. An experimental prototype using a dspace1104 based controller is also produced in the laboratory. Results from simulation match well with the corresponding results from experimental prototype confirming the usefulness of the proposed technique.

Summary The paper is devoted to a new adaptive variable-structure system (VSS) control algorithm and its applications in underwater robotics. The proposed approach is based on the usage of sliding mode parameter (SMP) in order to have adaptation in VSS. It is demonstrated that the extreme values of SMPs are directly associated with high efficiency of transient processes in VSS. The essence of the presented adaptation algorithm consists on the adjustment of switching surface parameters such that the SMPs move from the assigned desirable value to the extreme values, with the overall effect to accelerate transients. The effectiveness of the derived approach is proven by applying it for controlling a real remotely operated vehicle. Copyright © 2015 John Wiley & Sons, Ltd.

Currently, Ethernet is being enhanced to become the unified switch fabric in data centers. With the unified switch fabric, the cost on redundant devices is reduced, while the design and management of data center networks are simplified. Congestion management is one of the indispensable enhancements on Ethernet, and Quantized Congestion Notification (QCN) has just been ratified as the formal standard. Though QCN has been investigated for several years, there exist few in-depth theoretical analyses on QCN. The most possible reason is that QCN is heuristically designed and involves the property of variable structure. The classic linear analysis method is incapable of handling the segmented nonlinearity of the variable structure system. In this paper, we use the phase plane method, which is suitable for systems of segmented nonlinearity, to analyze the QCN system. The overall dynamic behaviors of the QCN system are presented, and the sufficient conditions for the stable QCN system are deduced. These sufficient conditions serve as guidelines toward proper parameters setting. Moreover, we find that the stability of QCN is mainly promised by the sliding mode motion, which is the underlying reason for QCN's stable queue shown in numerous simulations and experiments. Experiments on the NetFPGA platform verify that the analytical results can explain the complex behaviors of QCN.

Design a robust artificial intelligent nonlinear controller for second order nonlinear uncertain dynamical systems is one of the most important challenging works. This paper focuses on the design of a robust chattering free mathematical model-base artificial intelligence (fuzzy inference system) variable structure controller (MFVSC) for highly nonlinear dynamic continuum robot manipulator, in presence of uncertainties. In order to provide high performance nonlinear methodology, variable structure controller is selected. Pure variable structure controller can be used to control of partly known nonlinear dynamic parameters of continuum robot manipulator. In order to reduce/eliminate the chattering, this research is used the artificial intelligence (fuzzy logic) theory. The results demonstrate that the model base fuzzy variable structure controller with switching function is a model-based controllers which works well in certain and partly uncertain system. Lyapunov stability is proved in mathematical modelbased fuzzy variable structure controller with switching (sign) function. This controller has acceptable performance in presence of uncertainty (e.g., overshoot=1%, rise time=0.9 second, steady state error = 1.6e-8 and RMS error=4.8e-8).

In this paper, a novel hybrid Particle Swarm Optimization (PSO) and Pattern Search (PS) optimized fuzzy PI controller is proposed for Automatic Generation Control (AGC) of multi area power systems. Initially a two area non-reheat thermal system is used and the gains of the fuzzy PI controller are optimized employing a hybrid PSO and PS (hPSO-PS) optimization technique. The superiority of the proposed fuzzy PI controller has been shown by comparing the results with Bacteria Foraging Optimization Algorithm (BFOA), Genetic Algorithm (GA), conventional Ziegler Nichols (ZN), Differential Evolution (DE) and hybrid BFOA and PSO based PI controllers for the same interconnected power system. Additionally, the proposed approach is further extended to multi source multi area hydro thermal power system with/without HVDC link. The superiority of the proposed approach is shown by comparing the results with some recently published approaches such as ZN tuned PI, Variable Structure System (VSS) based ZN tuned PI, GA tuned PI, VSS based GA tuned PI, Fuzzy Gain Scheduling (FGS) and VSS based FGS for the identical power systems. Further, sensitivity analysis is carried out which demonstrates the ability of the proposed approach to wide changes in system parameters, size and position of step load perturbation The proposed approach is also extended to a non-linear power system model by considering the effect of governor dead band non-linearity and the superiority of the proposed approach is shown by comparing the results of hybrid BFO-PSO and craziness based PSO approach for the identical interconnected power system. Finally, the study is extended to a three area system considering both thermal and hydro units with different controllers in each area and the results are compared with hybrid BFO-PSO and ANFIS approaches.

The aim of this study is to enhance DFIG based Wind Energy Conversion Systems (WECS) dynamics during grid coupling. In this paper, a system modelling and a starting/coupling procedure for this generator to the grid are proposed. The proposed non-linear system is a variable structure system (VSS) and has two different states, before and after coupling. So, two different state models are given to the system to analyse transient stability during the coupling. The given model represents well the transient state of the machine, through which, a behaviour assessment of the generator before, during and after connection is given based on simulation results. For this, a 300 kW DFIG based wind generation system model was simulated on the Matlab/SIMULINK environment. We judge the proposed procedure to be practical, smooth and stability improved.

Sliding Mode Control is a nonlinear control methodology based on the use of a discontinuous control input which forces the controlled system to switch from one structure to another, evolving as a variable structure system. This structure variation makes the system state reach in a finite time a pre-specified subspace of the system state space where the desired dynamical properties are assigned to the controlled system. In the past years, an extensive literature has been devoted to the developments of Sliding Mode Control theory. This kind of methodology offers a number of benefits, the major of which is its robustness versus a significant class of uncertainties and disturbances during the sliding mode. Yet, it presents a crucial drawback, the so-called chattering, which may disrupt or damage the actuators and induce unacceptable vibrations throughout the controlled system. This limits the practical applicability of the methodology, especially in case of mechanical or electromechanical plants. This drawback has been faced by recent theoretical developments, oriented to increase the order of the sliding mode, thus producing efficient Second Order and Higher Order Sliding Mode Control algorithms. Robustness of the controlled system, in addition, has been extended to hold since the initial time instant of the control horizon, via the so-called Integral Sliding Mode Control approach. These “modern” results can be profitably used to efficiently solve automotive control problems, as testified by several recent publications and research projects. The aim of this lecture is to provide an outline of the mentioned theoretical advancements, and an overview of available examples of application of sliding mode control to the automotive field, focusing on recent activities developed by the research group chaired by Prof. Ferrara at the University of Pavia.

This paper is devoted to investigating the problems of the variable structure control and optimization for a class of time delay systems, which contain matched uncertainty and unmatched uncertainty, time-varying delay in state of system. Firstly, some special transformation is made for the considered system to obtain an equivalent system. A sliding surface is designed to ensure the behavior of system in the sliding mode exhibit desired performance. Secondly, it is concentrated on the optimization problem for the bounds of unmatched nonlinearity and designed gains, which guarantees the quadratic stability of the sliding motion. Flexible inequality amplifying techniques are developed for the good theoretical results. Thirdly, the efficient variable structure control is designed to drive the considered system state to the sliding surface and maintain a sliding motion on it thereafter. Finally, the effectiveness of the proposed variable structure control is illustrated through an numerical example.

The article focuses on the issues of Load Frequency Control (LFC) under non-linear strategies in multi source multi area hydro thermal system. On practical perspective dead band, boiler dynamics, reheat steam turbine along with hydro turbine operating under two different area capacities are considered in the system. When subjected to random load variations in both the areas, the system exhibits higher oscillations. The speed governor matches the generation with the demand. The offset in the area frequencies and tie-line power is removed by using secondary Proportional Integral (PI) controller. The PI controller is tuned using Ziegler Nichols' (ZN) and Fuzzy Gain Scheduling (FGS) method. The influence of high Proportional (P) controller gain during steady state and high Integral (I) controller gain during transient affects the system performance. Variable Structure System (VSS) helps to switch from P to PI controller during transient to steady state based on control error. The concept of VSS is applied to Fuzzy Gain Scheduling (FGS) PI controller. The performance of the optimal Variable Structure Fuzzy Gain Scheduled (VSFGS) controller under non-linear environment is judged and validated using performance indices.

Applications of several nonlinear control laws, including differential geometric approach and the robust variable structure system (VSS) approach, will be investigated for the fault ride-through (FRT) enhancement of the doubly fed induction generator wind power system. In differential geometric approach, both input-output feedback linearization and state feedback linearization will be studied for rotor-side converter and stator- side converter control. In robust VSS approach, supplementary control generated by the complete models is achieved for FRT enhancement. Two objectives, maximizing the active power out- put as well as regulating the terminal voltage, will be utilized for designing the sliding manifold. Since the proposed methods are based on the general nonlinear system theory, the FRT capability can be indeed improved even under severe fault conditions. Simulations on a one-machine infinite bus system and a two- area four-machine system are presented to validate this result. Performance comparisons among several existing FRT enhanced control will also be examined to show the effectiveness of these nonlinear control schemes.

A nonlinear decoupling control method based on back-stepping design and sliding variable structure control theory was proposed in this paper according to the nonlinear and strong coupling characteristics of missile at hingh angle of attack. The affine nonlinear model of missile was firstly established, the exact linearization and input/output decoupling of system were then realized using differential geometry theory. On the basis of this, the robust controller was designed using back-stepping design and variable structure control method. Simulation results indicate that the influences caused by missile parameter uncertainties, unsuited uncertainties with known upper boundaries and stochastic interference can be effectively restrained.

Current source converter is a variable structure system due to its switching nature, so that it can easily cause the output current waveform distortion and can not be accurately track the reference current. To solve the above problems, this paper proposes a new variable structure control strategy with fan-shaped sliding domain in the current source converter control system. In the control strategy, the paper deduces the switching surface and switching control law of SMVSC, and calculates the sliding existence domain based on the mathematical model of current source converter. Finally, the simulation results show that the control scheme can make current source converter have better output current waveform, fast tracking the reference current, and strong anti-interference ability. Therefore, the control scheme is correct, effective and feasible.

This paper explores distributed smart grid attack strategies to destabilize power system components using variable structure system theory. Here, an opponent is able to remotely control multiple circuit breakers within a power system, say through data corruption or communication network attack, to destabilize target synchronous generators through application of state-dependent breaker switching. In contrast to attack via a single breaker, the multi-switch case provides additional degrees of freedom that can lead to stealthier and wide-scale cascading failures. We provide a dynamical systems context for formulating distributed multi-switch strategies and execute such attacks on the New England 10-generator 39-bus test system.

This paper presents a simple and systematic approach to design sliding mode controller for buck converters. DC/DC switching converters have been used in many applications in recent years. The Sliding Mode Control (SMC) based on Variable Structure System (VSS) theory has been examined for buck switch mode converter type. To obtain a sliding regime, the appropriate sliding surface is selected by assigning poles combined with genetic algorithm. The associated practical problems and the proposed solutions are detailed; like fixed frequency by using pulse width modulation (PWM) as solution and overshoot limitation of the inductor current by using current limiter. A simple and easy to follow design procedure is also described. Simulation results are presented to illustrate the design procedure. The simulation results of the proposed SMC strategy are compared with the adaptive terminal sliding mode control (ATSMC) and PID-SMVC strategies. It is shown that the proposed SMC exhibits a considerable improvement in terms of a faster output voltage response during load changes.

In this paper, variable structure fuzzy gain scheduling is proposed for solving the load frequency control problem of multi source multi area hydro thermal power system. The two control areas are connected via tie line. Each area comprises of both hydro and thermal power plant. The area frequency and tie line power oscillates during load variations are controlled by primary governor controller and secondary Proportional Integral (PI) controller. The PI controller gains are tuned using Ziegler Nichols’ (ZN) method and Genetic Algorithm (GA). ZN method is for conventional bench marking and GA is based on search in the space. In both the methods, the gain values of PI controllers are fixed for any system changes and it is not acceptable. This problem is overcome by scheduling the gain based on system changes using Fuzzy Logic. Finally, Variable Structure System of switching P to PI controller during transient to steady state is integrated with fuzzy gain scheduling. On evaluating all the controller performance based on performance indices, variable structure fuzzy gain scheduling provides better response for multi source multi area hydro thermal power system.

Security issues in cyber-physical systems are of paramount importance due to the often safety-critical nature of its associated applications. A first step in understanding how to protect such systems requires an understanding of emergent weaknesses, in part, due to the cyber-physical coupling. In this paper, we present a framework that models a class of cyber-physical switching vulnerabilities in smart grid systems. Variable structure system theory is employed to effectively characterize the cyber-physical interaction of the smart grid and demonstrate how existence of the switching vulnerability is dependent on the local structure of the power grid. We identify and demonstrate how through successful cyber intrusion and local knowledge of the grid an opponent can compute and apply a coordinated switching sequence to a circuit breaker to disrupt operation within a short interval of time. We illustrate the utility of the attack approach empirically on the Western Electricity Coordinating Council three-machine, nine-bus system under both model error and partial state information.

This study presents the design of a current control loop and the selection of switching logic for pulse-width modulation (PWM) of three-phase switching converters. This approach is based on a deliberate introduction of the predictive sliding mode motion within a control system. It shows that the selection of the PWM pattern is a direct result of sliding mode existence within the current control closed-loop system. The design specifications are robustness to load electrical parameters, fast dynamic response, reduced switching frequency and simple hardware implementation. To meet previous specifications, a sliding mode controller has been developed, designed as a finite state machine, and implemented within a field programmable gate array device. The switching strategy implemented within the state transition diagram provides for a minimum number of switch state changes by the three-phase converter that is confirmed through simulation and experimental results.

In this paper, we study the finite-time synchronization problem for linearly coupled complex networks with discontinuous nonidentical nodes. Firstly, new conditions for general discontinuous chaotic systems is proposed, which is easy to be verified. Secondly, a set of new controllers are designed such that the considered model can be finite-timely synchronized onto any target node with discontinuous functions. Based on a finite-time stability theorem for equations with discontinuous right-hand and inequality techniques, several sufficient conditions are obtained to ensure the synchronization goal. Results of this paper are general, and they extend and improve existing results on both continuous and discontinuous complex networks. Finally, numerical example, in which a BA scale-free network with discontinuous Sprott and Chua circuits is finite-timely synchronized onto discontinuous Chen system, is given to show the effectiveness of our new results.

In this paper, based on the nonlinear state feedback decoupling method, the dynamic transfer function of the inductor motor and pump control motor is setup, and the variable frequency hydraulic control system is realized to solve the contradiction between efficiency and dynamic characteristics using traditional control method. The simulation results show that this system has the better dynamic performance than VCS (Vector Control System). Then in order to optimize the system, the dynamic mathematical model including iron losses is built from the aspect of energy transmission. At last the condition of minimum loss of the system is deduced.

An adaptive robust attitude tracking control law based on switched nonlinear systems is presented for a variable structure near space vehicle (VSNSV) in the presence of uncertainties and disturbances. The adaptive fuzzy systems are employed for approximating unknown functions in the flight dynamic model and their parameters are updated online. To improve the flight robust performance, robust controllers with adaptive gains are designed to compensate for the approximation errors and thus they have less design conservation. Moreover, a systematic procedure is developed for the synthesis of adaptive fuzzy dynamic surface control (DSC) approach. According to the common Lyapunov function theory, it is proved that all signals of the closed-loop system are uniformly ultimately bounded by the continuous controller. The simulation results demonstrate the effectiveness and robustness of the proposed control scheme.

New methods of the synthesis of multi-dimensional robust and adaptive control systems for the centralized control of the spatial motion of autonomous underwater vehicles (AUV) is developed in this paper, such as variable structure system (VSS) and self-adjustment system with reference model. The conditions of the sliding mode existence and the self-adjustment process stability with the presence of essential dynamic reciprocal effect between all control channels are obtained and strictly proved. The application of synthesized discontinuous control provides the high control quality at any variations of the object parameters within the given ranges.

We argue for a morphofunctional approach to emotion modeling that can also aid the design of adaptive embodied systems. By morphofunctionality we target the online change in both structure and function of a system, and relate it to the notion of physiology and emotion in animals. Besides the biological intuition that emotions serve the function of preparing the body, we investigate the control requirements that any morphofunctional autonomous system must face. We argue that changes in morphology modify the dynamics of the system, thus forming a variable structure system (VSS). We introduce some of the techniques of control theory to deal with VSSs and derive a twofold hypothesis: first, the loose coupling between two control systems, in charge of action and action readiness, respectively; second, the formation of patterned metacontrol. Emotional phenomena can be seen as emergent from this control setup.

Cricket system is a typical multivariable, uncertainty, strong coupling, nonlinear dynamics of the underactuated system, is two dimensional extension of club system, have been many scholars at home and abroad as the study of nonlinear control system experimental platform. Usually, the fuzzy adaptive control method is applied to uncertain nonlinear systems, for the practical engineering common multivariable and nonlinear system control matrix irreversible lacked certain applicability. In the process of cricket in uncertain nonlinear system, when the control gain matrix determinant equal to zero, namely the control matrix is irreversible, the ball is out of control. Therefore, to design a can supervise system stability and the supervision of the state variable changes hierarchical controller is of great significance. In this paper, the controller is divided into two layers: the upper layer for supervision and optimization, The lower is combined with the adaptive rule and sliding mode theory, the advantages of intelligent algorithm design of the controller.

A novel control for a nonlinear two-dimensional (2-D) overhead crane is proposed. Instead of the complex design procedures used in classic methods, the proposed scheme combines the principles of neural networks (NNs) and variable structure systems (VSS) to derive control signals needed to drive the cart smoothly, rapidly and with limited payload swing. The merits include the robustness and model-free properties of the sliding mode and neural based controllers, respectively. Simulations performed using a scaled 2-D mathematical model of the crane confirm the effectiveness of the proposed method.

Attitude control of satellites using fluid rings is studied in this paper. A complete dynamics model of a rigid satellite containing fluid rings is developed. It is noticed that when the fluid rings are used as passive controllers they can damp out all attitude disturbances if the satellite is in a circular orbit and only roll―yaw disturbances if the satellite is in an elliptic orbit. However, this passive damping effect is fairly slow. Hence, an active controller is developed to reduce the settling time. To add redundancy to the attitude control system (ACS) of the satellite, four fluid rings in a pyramidal configuration are used. Also, the effect of the failure of one fluid ring on the performance of the ACS of the satellite is tested. Finally, a hybrid controller that is composed of a sliding mode controller and a proportional integral derivative is designed in order to cope with the model uncertainties and eliminate chattering in the response of the system.

The control of electric-power-assisted steering (EPAS) systems is a challenging problem due to multiple objectives and the need for several pieces of information to implement the control. The control objectives are to generate assist torque with fast responses to driver's torque commands, ensure system stability, attenuate vibrations, transmit the road information to the driver, and improve the steering wheel returnability and free-control performance. The control must also be robust to modeling errors and parameter uncertainties. To achieve these objectives, a new control strategy is introduced in this paper. A reference model is used to generate an ideal motor angle that can guarantee the desired performance, and then, a sliding-mode control is used to track the desired motor angle. This reference model is built using a dynamic mechanical EPAS model, which is driven by the driver torque, the road reaction torque, and the desired assist torque. To implement the reference model with a minimum of sensors, a sliding-mode observer with unknown inputs and robust differentiators are employed to estimate the driver torque, the road reaction torque, and the system's states. With the proposed control strategy, there is no need for different algorithms, rules for switching between these algorithms, or fine-tuning of several parameters. In addition, our strategy improves system performance and robustness and reduces costs. The simulation results show that the proposed control structure can satisfy the desired performance.

The intrinsic properties of an ultrasonic motor (high torque for low speed, high static torque, compact in size, no electromagnetic interference, etc.) offer great advantages for industrial applications. However, when load torque is applied, a dead-zone occurs in control input. Therefore, a sliding-mode controller, which is a non-linear controller, is adopted for the ultrasonic motor. The state quantities, such as acceleration, speed, and position, are needed to apply the sliding-mode controller for position control. However, a rotary encoder causes quantization errors in the speed information. This article presents a robust position control method for an ultrasonic motor by using a variable structure system observer. The state variables for the sliding-mode controller are estimated by the variable structure system observer. A small, low-cost, and good response sliding-mode controller is designed in this work by using a microcomputer that is essential in an embedded system for the development of ...

Problem statement: A brushless DC servomotor position control system using a fuzzy logic sliding mode model following controller or FLSMFC is presented. Approach: The FLSMFC structure consists of an integrator and variable structure system. Results: The integrator ensures the elimination of steady state error due to step and ramp command inputs, while the fuzzy control would maintain the insensitivity to parameter variation and disturbances. The FLSMFC strategy is implemented and applied to a position control of a brushless DC servomotor. Conclusion/Recommendations: Experimental results indicated that FLSMFC system performance with respect to the sensitivity to parameter variations is greatly reduced. Also, its can achieve a rather accurate servo tracking and avoids the chattering phenomenon.

This article presents a control method for suppressing the swing vibration of a hybrid excavator. For control design, dynamic models of typical swing motions of the hybrid excavator are derived using a system identification technique. Because the system states of theobtained models are not directly measurable, a sliding mode observer is designed to estimate the system states. A sliding mode control is designed to provide robust tracking performance against the parameter variations and uncertain non-linearities caused by changes in the working conditions. A complicated mathematical model of the hybrid excavator which captures detailed mechanical, electrical, and hydraulic characteristics is developed for system analysis and simulation. The feasibility and effectiveness of the proposed control method are verified by simulations and actual tests in comparison with a conventional proportional and integral controller.

Electronically controlled air suspension systems have been used in vehicles to improve ride comfort and handling safety by adjusting vehicle height. This paper proposes a new nonlinear controller to adjust the height of the vehicle sprung mass (height control) and to regulate the roll and pitch angles of the vehicle body (leveling control) by an air suspension system. A sliding mode control algorithm is designed to improve the tracking accuracy of the control and to overcome nonlinearities and uncertainties in the air suspension system. A mathematical model of the air suspension system is formulated in a nonlinear affine form to describe the dynamic behavior of the system and to derive the control algorithm. The sliding mode observer is also designed to estimate the pressures inside four air springs. The effectiveness and performance of the proposed control algorithm are verified by simulations and actual vehicle tests.

There are many publications on the stabilization of an inverted pendulum because it is a typical unstable system and is well used as an example to verify many control theories. However, few approaches consider the inverted pendulum as an unknown parameter system. This paper proposes a new VSS (Variable Structure System) robust adaptive control system including a self-tuning controller for a rotary inverted pendulum all of whose parameters are unknown. The control system provides two kinds of adaptive controllers, and stabilization of the inverted pendulum is achieved by separating the system into two parts, the pendulum and the rotary arm. The rotational angle of the pendulum is stabilized by a tracking-type VSS adaptive control method, and the rotary arm is simultaneously stabilized by an STC (self-tuning control) system that assures the boundary reference angle of the pendulum. It is then not sufficient to construct an STC system using only the adjustable parameters of the VSS adaptive control system. Therefore, all basic parameters are recursively estimated in order to realize the STC system by using the least squares parameter adaptive law, and this is achieved by superimposing the perturbation signal on the stable adaptive control input over a limited short interval. Furthermore, the STC system designs an LQ controller by developing an efficient QR method for real-time operation. Finally, the validity of the proposed system is demonstrated by numerical simulations and practical experimental results. © 2011 Wiley Periodicals, Inc. Electron Comm Jpn, 94(6): 48–58, 2011; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/ecj.10179

An analysis of a sliding mode proximate time-optimal servomechanism (SPTOS) conducted through simulations and experiments is presented. The sliding mode is utilized to deliver proximate time-optimal performance naturally. We also examine why the SPTOS scheme is superior to the proximate time-optimal servomechanism that is widely used in the disk drive industry. The SPTOS is shown to produce bounded motion along the reference profile, which contributes to accurate reference profile tracking even in the presence of plant uncertainties. The application of the SPTOS yielded accurate reference velocity profile tracking as well as uniformly excellent seek performance regardless of the seek length.

An online fault detection scheme for a sample power system is introduced in this paper. The detection approach is based on the use of a variable structure system called “sliding mode observer”, where information contained in the output measurements is utilized to detect the onset of faults in the transmission network of the sample power system in real time and online. The power system comprises a generating unit connected to an infinite bus through double line transmission network. The common case of a fault occurring on a transmission line is illustrated through simulation studies.

Piezoelectric actuators are widely used in micro manipulation applications. However, hysteresis nonlinearity limits the accuracy of these actuators. This paper presents a novel approach for utilizing a piezoelectric nano-stage as the slave manipulator of a teleoperation system based on a sliding mode controller. The Prandtl–Ishlinskii (PI) model is used to model actuator hysteresis in feedforward scheme to cancel out this nonlinearity. The presented approach requires full state and force measurements at both the master and slave sides. Such a system is costly and also difficult to implement. Therefore, sliding mode unknown input observer (UIO) is proposed for full state and force estimations. Furthermore, the effects of uncertainties in the constant parameters on the estimated external forces should be eliminated. So, a robust adaptive controller is proposed and its stability is guaranteed through the Lyapunov criterion. Performance of the proposed control architecture is verified through experiments.

This paper deals with the design and implementation of the nonlinear control algorithm for the attitude tracking of a four-rotor helicopter known as quadrotor. The choice of this algorithm, which is based on the Backstepping sliding mode technique with adaptive gain, was justified by the fact that it ensures robustness with respect to modelling errors and external disturbances while reducing the chattering phenomenon caused by the sign function in the first order sliding mode based controllers with fixed gains. In order to show the effectiveness of the controller, experimental tests were carried out on a quadrotor. The obtained results show good performance of the proposed controller in terms of stabilisation, tracking and robustness.

S PIN is an autorotational state of aircraft at high angles of attack characterized by large rotation rate in yaw when compared with rates in roll and pitch. In a typical spin, an aircraft rotates about its center of gravity and an axis perpendicular to Earth descending vertically at high speed following a downward corkscrew path [1]. It is one of themost dangerous phenomena encountered bymany of the modern fighter aircraft required to fly in high-angle-of-attack flight regimes. Improper functioning of aerodynamic control surfaces during spin makes it difficult for the pilot to control the aircraft, leading to many a problem, such as spatial disorientation and uncontrolled motion, resulting in fatal accidents and subsequent loss of aircraft. Spin states for many high-angle-of-attack aircraft models have been computed by using bifurcation analysis and continuation technique methodology. Bifurcation analysis results provide the onset points of bifurcations or the critical values of control surface deflections that may inadvertently or voluntarily land an aircraft into spin. Standard control inputs using proper deflection of rudder to control yaw rate with simultaneous application of elevator to reduce the angle of attack have been recommended for spin recovery [1]. Design of new-generation fighter aircraft with new configurations, however, cannot rely on standard piloting strategies. Instead, a uniform approach to design aircraft-model-based recovery strategies is called for. An introduction to spin problem and needs to design nonlinear controllers to recover aircraft from spin has been reported recently in [2]. Identifying spin and level-trim states from a bifurcation analysis of a nonlinear aircraft model, Raghavendra et al. [2] developed a nonlinear dynamic inversion (NDI)-techniquebased spin-recovery controller. NDI-technique-based methods have emerged as popular control design techniques in aircraft flight dynamics. Controllers based on the NDI techniques, however, come with certain associated disadvantages, such as separation of dynamics based on timescales, resulting in complicated control architecture, lack of robustness due to external uncertainties and unmodeled plant dynamics, and inability to achieve control saturation limits [3]. In this Note, we present a sliding-mode (SM) controller based on variable-structure control technique for spin recovery of aircraft. Variable-structure-technique-based controllers have been found to be robust in the presence of system uncertainties and external disturbances, and, usually result in simpler control algorithms [4]. Controller presented in this Note uses results from a bifurcation analysis of the high-angle-of-attack research vehicle (HARV) model of F-18 available in literature [2]. This Note is organized as follows. In Sec. II, a brief description of the aircraft model with reference states for SM controller design is presented. In Sec. III, SM control design technique is explained. Results and discussions are presented in Sec. IV and conclusions follow thereafter in Sec. V.

The major task for any monitoring system is to detect upcoming faults as early as possible. Rotor failures are responsible for a large percentage of total induction motor failures. Thus, a new nonintrusive and in-service approach has been proposed in this paper to detect one broken rotor bar in induction motor using only input quantities information. The method is not affected by the type of load and other asymmetries and it is capable of providing reliable fault diagnose without maintenance specialist intervention. The proposed sensorless technique is based on two real time state space discrete models that are used to estimate the flux of both the stator and the rotor and analyzes the differences obtained in torque when the two models are employed. One of the observers was designed for rotor resistance disturbance rejection. Firstly, simulation results have been conducted and sensitivity and robustness also have been checked for the proposed method. Secondly, an experimental setup has been constructed to implement the new technique in on-line model. The results obtained validate the proposed model and show the reliability of the new method.

This paper proposes an actuator fault-tolerant control scheme designed for a class of nonlinear systems, and then applied to an underwater Remotely Operated Vehicle (ROV) used for inspection purposes. Fault detection is achieved using a Variable Structure System (VSS) observer, while a sliding-mode based approach has been used both for fault isolation and ROV control, after the application of an input decoupling nonlinear state transformation to the ROV model. Finally, control reconfiguration is performed exploiting the inherent redundancy of actuators. An extensive simulation study has been also performed, supporting the effectiveness of the proposed approach.

This paper presents a robust output feedback controller based on sliding modes and indirect adaptive control applied to the angular shaft speed control of a three-phase induction motor. This approach has remarkable stability properties and offers a straightforward and intuitive tuning of its parameters. Moreover, a simplified version of the algorithm, named compact indirect variable structure model reference adaptive control (CIVS-MRAC), provides not only an easy design procedure, but also a computational implementation of low complexity, thus motivating its application in industrial environments.

This study presents an adaptive sliding mode controller for a micro-electro-mechanical systems (MEMS) z-axis vibratory gyroscope. The adaptive model reference state tracking control with sliding mode controller is developed to estimate the angular velocity, the damping and stiffness coefficients of MEMS vibratory gyroscope in real time. An adaptive controller that can estimate the unknown upper bound of the parameter uncertainties and external disturbance is derived and the stability of the closed-loop system is established. The adaptive sliding mode controller is designed so that the trajectory of the driving axes can track the state of the reference vibration model. The effectiveness of the proposed scheme is demonstrated through numerical simulations on an MEMS vibratory gyroscope.

A new state-of-health (SOH) estimation method for lithium batteries that uses a dual-sliding-mode observer is presented. The capacity fade and resistance deterioration were estimated by the dual-sliding-mode observer. The dual-sliding-mode observer consists of a fast-paced time-varying observer and a slow-paced time-varying observer. The fast-paced time-varying observer estimates parameters, such as the state of charge and terminal voltage, and polarization effects. The slow-paced time-varying observer estimates the SOH in terms of the capacity fade and resistance deterioration. The convergence of the proposed observer was proved by the Lyapunov equation. The structure of the proposed system is simple and easy to implement and shows robust control properties against modeling errors and temperature variations. The test results show that the proposed observer system has superior tracking performance than previous ampere-counting method.

Actual endoscopes and boroscopes, widely used in industry and in minimal invasive surgery, have considerable limitations, mainly due to their low number of degrees of freedom and their manual operation. Two different solutions for the electrical actuation of articulated endoscopes are presented in this paper. The technical constraints for this kind of application are very limited space for the actuators and high performance in terms of torque and angular reach. The first solution classically consists in a 2 d.o.f. structure steered by two pairs of antagonist shape memory alloy (SMA) wires. The sizing and preload determination for those actuators follow an original analytical approach. The second solution consists in a multi-d.o.f. structure actuated by thin NiTi springs mounted in an antagonist configuration and directly integrated in the structure of the endoscope. The geometry of the springs is obtained by optimization through genetic algorithms and finite elements method. Experiments show good adequacy between real behaviour and numerical model and also validate the approach. This study is also enhanced by a control scheme specifically developed for SMA actuators in an antagonist configuration. It is based on a first order sliding mode scheme, which has the advantage of a great structural simplicity. The experimental results show that this solution can reach a good compromise between the dynamic behaviour of the actuator, its energy consumption and the structural lifetime of the endoscope.

In this paper, we discuss the classical problem of attitude stabilization for a rigid spacecraft with external disturbances. Almost all the control laws for attitude stabilization problem in the literature can only guarantee at best exponential convergence of the attitude with infinite settling time. We employ finite-time control techniques including terminal sliding mode approach and continuous finite-time control approach to develop feedback control laws for stabilizing spacecraft attitude in terms of Rodrigues parameters. The attitude of the rigid spacecraft will be stabilized to the origin in finite time in the absence of disturbances and a small region of the origin in the presence of disturbances. Rigorous proof is given. Numerical simulation results show the effectiveness of the method.

The problem of designing robust tracking controls for a large class of robots actuated by brushed direct current motors is addressed. This class of electrically driven robots can be perturbed by plant uncertainties, unmodelled time-varying perturbations and external disturbances. Adaptive neural network (or fuzzy) systems are employed to approximate the behaviours of uncertain dynamics, and the variable structure system control algorithm is used to efficiently eliminate the effect of both the approximation error and the time-varying perturbation. Consequently, a hybrid robust adaptive dynamic feedback tracking controller is developed such that all the states and signals of the closed-loop system are bounded and the asymptotic bound on the trajectory tracking error can be made arbitrarily small. Finally, simulation examples are presented to demonstrate the effectiveness and the tracking performance of the proposed control algorithm.

In this paper, a novel “composite reaching law” was explained in details: 1) the equation of discrete motion for a control system; 2) the design of discrete-time variable structure control. In addition, the model of a three-storey shear-type building structure was used to verify the effectiveness of the discrete variable structure control method. The results of numerical example analysis of the model show that the control law can effectively reduce the peak value of seismic response of the building structure and the chattering effect of the control system.

This paper presents an NMPC of a supermarket refrigeration system. This is a hybrid process involving switched nonlinear dynamics and discrete events, on/off manipulated variables (valves and compressors), continuous controlled variables (goods temperatures) and, finally, several operation constraints. The hybrid controller is based on a parameterization of the on/off control signals in terms of time of occurrence of events instead of using directly binary values; in this way, the optimization problem can be re-formulated as an NLP problem. A rigorous model of a real supermarket refrigeration system is presented, as well as results of the hybrid controller operating on it.