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Hydro-turbine governing system (HTGS) is a complicated nonlinear system that is directly related to the safety of the hydropower stations. In this paper, a simplified predictive control method is presented for the HTGS. Moreover, the system parameters of the predictive controllers are given. Simulated results are presented to evaluate the control performance of the predictive controller, which is compared with the conventional PID controller. [ABSTRACT FROM AUTHOR]

The article proposes a new flatness-based control method implemented in successive loops which allows for stabilization of the heart's electrical activity. Heart's pacemaking function is modeled as a set of coupled oscillators which potentially can exhibit chaotic behavior. It is shown that this model satisfies differential flatness properties. Next, the control and stabilization of this model is performed with the use of flatness-based control implemented in cascading loops. By applying a per-row decomposition of the state-space model of the coupled oscillators a set of nonlinear differential equations is obtained. Differential flatness properties are shown to hold for the subsystems associated with the each one of the aforementioned differential equations and next a local flatness-based controller is designed for each subsystem. For the i-th subsystem, state variable xi is chosen to be the flat output and state variable xi+1 is taken to be a virtual control input. Then the value of the virtual control input which eliminates the output tracking error for the i-th subsystem becomes reference setpoint for the i+1-th subsystem. In this manner the control of the entire state-space model is performed by successive flatness-based control loops. By arriving at the n-th row of the state-space model one computes the control input that can be actually exerted on the aforementioned biosystem. This real control input of the coupled oscillators' system, contains recursively all virtual control inputs associated with the previous n-1 rows of the state-space model. This control approach achieves asymptotically the elimination of the chaotic oscillation effects and the stabilization of the heart's pulsation rhythm. The stability of the proposed control scheme is proven with the use of Lyapunov analysis. [ABSTRACT FROM AUTHOR]

This paper presents nonlinear backstepping control for Wind Power Generation System (WPGS) based Permanent Magnet Synchronous Generator (PMSG) and connected to utility grid. The block diagram of the WPGS with PMSG and the grid side back-to-back converter is established with the dq frame of axes. This control scheme emphasises the regulation of the dc-link voltage and the control of the power factor at changing wind speed. Besides, in the proposed control strategy of WPGS, Maximum Power Point Tracking (MPPT) technique and pitch control are provided. The stability of the regulators is assured by employing Lyapunov analysis. The proposed control strategy for the system has been validated by MATLAB simulations under varying wind velocity and the grid fault condition. In addition, a comparison of simulation results based on the proposed Backstepping strategy and conventional Vector Control is provided. [ABSTRACT FROM AUTHOR]

The article presents a differential flatness theory-based method for adaptive control of autonomous submarines. A proof is provided about the differential flatness properties of the submarine's model (having as state variables the vessel's depth and its pitch angle). This also means that all its state variables and its control inputs can be written as differential functions of the flat output. Making use of its differential flatness features, the submarine's dynamic model is transformed into the multivariable linear canonical (Brunovsky) form. In the transformed model, the control inputs consist of unknown nonlinear parts, which are identified with the use of neurofuzzy approximators. The learning rate for these estimators is determined by the requirement the first derivative of the closed-loop's Lyapunov function to be a negative one. Furthermore, with the use of Lyapunov stability analysis it is proven that an H-infinity tracking performance is succeeded for the feedback control loop. This implies enhanced robustness to model uncertainty and to external perturbations. Simulation experiments are carried out to further confirm the efficiency of the proposed adaptive fuzzy control scheme. [ABSTRACT FROM AUTHOR]

The paper proposes nonlinear control and filtering for Autonomous Underwater Vessels (AUVs) based on differential flatness theory and on the use of the Derivative-free nonlinear Kalman Filter. First, it is shown that the 6-DOF dynamic model of the AUV is a differentially flat one. This enables its transformation into the linear canonical (Brunovsky) form and facilitates the design of a state feedback controller. A problem that has to be dealt with is the uncertainty about the parameters of the AUV's dynamic model, as well the external perturbations which affect its motion. To cope with this, it is proposed to use a disturbance observer which is based on the Derivative-free nonlinear Kalman Filter. The considered filtering method consists of the standard Kalman Filter recursion applied on the linearized model of the vessel and of an inverse transformation based on differential flatness theory, which enables to obtain estimates of the state variables of the initial nonlinear model of the vessel. The Kalman Filter-based disturbance observer performs simultaneous estimation of the non-measurable state variables of the AUV and of the perturbation terms that affect its dynamics. By estimating such disturbances, their compensation is also succeeded through suitable modification of the feedback control input. The efficiency of the proposed AUV control and estimation scheme is confirmed through simulation experiments. [ABSTRACT FROM AUTHOR]

The article discusses research which examined the task based weathervaning control algorithm for Dynamic Positioning (DP) offshore vessels under consideration of Lyapunov stability theory. Topics discussed include the offshore operations of the DP vessel and change in the vessel's heading without change of controlled position.

This paper presents a motion tracking and control system for automatically landing Unmanned Aerial Vehicles (UAVs) on an oscillating platform using Laser Radar (LADAR) observations. The system itself is assumed to be mounted on a ship deck. A full nonlinear mathematical model is first introduced for the UAV. The ship motion is characterized by a Fourier transform based method which includes a realistic characterization of the sea waves. LADAR observation models are introduced and an algorithm to process those observations for yielding the relative state between the vessel and the UAV is presented, from which the UAV's state relative to an inertial frame can be obtained and used for feedback purposes. A sliding mode control algorithm is derived for tracking a landing trajectory defined by a set of desired waypoints. An extended Kalman filter (EKF) is proposed to account for process and observation noises in the design of a state estimator. The effectiveness of the control algorithm is illustrated through a simulation example. [ABSTRACT FROM AUTHOR]

The paper proposes a differential flatness theory-based adaptive fuzzy controller for spark-ignited (SI) engines. The system's dynamic model is considered to be completely unknown. By applying a change of variables (diffeomorphism) that is based on differential flatness theory the engine's dynamic model is written in the linear canonical (Brunovsky) form. After transforming the SI-engine model into the canonical form, the resulting control inputs are shown to contain nonlinear elements which depend on the system's parameters. These nonlinear terms are approximated with the use of neuro-fuzzy networks while a suitable learning law can be defined for the aforementioned neuro-fuzzy approximators so as to preserve the closed-loop system stability. Moreover, using Lyapunov stability analysis it is shown that the adaptive fuzzy control scheme succeeds H x tracking performance, which means that the influence of the modeling errors and the external disturbances on the tracking error is attenuated to an arbitrary desirable level. The efficiency of the proposed adaptive fuzzy control scheme is checked through simulation experiments. [ABSTRACT FROM AUTHOR]

Highly efficient embedded control units for transportation means make use of advanced nonlinear control and estimation methods. In this research article a new nonlinear filtering and control method is applied to spark ignited (SI) engines. The proposed SI engine's control scheme requires the implementation of differential flatness theory together with a new nonlinear filtering approach (known as Derivative-free nonlinear Kalman Filtering). The considered method succeeds the efficient control of the SI engine parameters such as intake pressure and turn speed. To bring the control loop at a working stage additional problems have to be solved. These are for instance that (i) certain variables of the engine's state vector cannot be measured directly (e.g. the ones associated with input pressure), (ii) there are inaccuracies in the dynamic model of the SI engine while external perturbations and disturbances (such as friction torques) are exerted to the engine. The performance of the proposed control scheme is tested through simulation experiments. [ABSTRACT FROM AUTHOR]

In this paper nonlinear embedded control for turbocharged Diesel engines is developed with the use of Differential flatness theory and adaptive fuzzy control. It is shown that the dynamic model of the turbocharged Diesel engine is differentially flat and admits dynamic feedback linearization. It is also shown that the dynamic model can be written in the linear Brunovsky canonical form for which a state feedback controller can be easily designed. To compensate for modeling errors and external disturbances an adaptive fuzzy control scheme is implemanted making use of the transformed dynamical system of the diesel engine that is obtained through the application of differential flatness theory. Since only the system's output is measurable the complete state vector has to be reconstructed with the use of a state observer. It is shown that a suitable learning law can be defined for neuro-fuzzy approximators, which are part of the controller, so as to preserve the closed-loop system stability. With the use of Lyapunov stability analysis it is proven that the proposed observer-based adaptive fuzzy control scheme results in H∞ tracking performance. [ABSTRACT FROM AUTHOR]

The development of efficient embedded control for turbocharged Diesel engines, requires the programming of elaborated nonlinear control and filtering methods. To this end, in this paper nonlinear control for turbocharged Diesel engines is developed with the use of Differential flatness theory and the Derivative-free nonlinear Kalman Filter. It is shown that the dynamic model of the turbocharged Diesel engine is differentially flat and admits dynamic feedback linearization. It is also shown that the dynamic model can be written in the linear Brunovsky canonical form for which a state feedback controller can be easily designed. To compensate for modeling errors and external disturbances the Derivative-free nonlinear Kalman Filter is used and redesigned as a disturbance observer. The filter consists of the Kalman Filter recursion on the linearized equivalent of the Diesel engine model and of an inverse transformation based on differential flatness theory which enables to obtain estimates for the state variables of the initial nonlinear model. Once the disturbances variables are identified it is possible to compensate them by including an additional control term in the feedback loop. The efficiency of the proposed control method is tested through simulation experiments. [ABSTRACT FROM AUTHOR]

The purpose of this communication is to investigate the effectiveness of a spatial indexed guidance law to perform longitudinal trajectory tracking with overfly time constraints. The aircraft flight dynamics are expressed in a space indexed frame and a nonlinear control structure is adopted. The influence of wind and navigation estimation errors on the 2D+T guidance performance is analyzed while simulation results are displayed. [ABSTRACT FROM AUTHOR]

In this paper a pulsewidth modulation based sliding mode controller (PWM SMC) design for a four switch three level bidirectional converter (3L BDC) is presented. The converter nonlinear control design in this structure is complicated because of the existence of two independent switch sets. To overcome this difficulty, an initiative way in defining the control law which utilizes interleaving control of switch sets is proposed. Using this way, the independent switch sets become somehow dependent. The designed controller is analysed and simulated using Matlab (Simulink Toolbox) software. The simulated results show the effectiveness of the designed controller in steady state and transient state of the converter. [ABSTRACT FROM PUBLISHER]

Conventional sliding mode control (SMC) usually causes chattering problem. Fuzzy sliding mode has been proposed in literature to reduce chattering. Interval type 2 fuzzy logic systems (IT2FLS) enhances fuzzy system performance by incorporating uncertainties in rule base. In this paper, the reaching component of SMC is replaced by an IT2FLS to reduce chattering taking into consideration possible system uncertainties. The inputs of the IT2FLS are the sliding variable and its derivative. To investigate the validity of the proposed controller, it is used to control a simulated model of an under-actuated, unstable inverted pendulum. The Simulation results show that the proposed controller can handle more efficiently parameter uncertainty and disturbance in stabilization of the pendulum and cart position tracking to a reference trajectory. [ABSTRACT FROM PUBLISHER]

This paper presents a new discrete-time sliding mode control (DSMC) scheme dedicated to precision positioning control of a piezoelectric actuation system. Traditionally, hysteresis modeling is required to compensate for the piezoelectric nonlinearity and state observer design is needed to implement the DSMC control, which renders a time-consuming procedure. The proposed DSMC control scheme releases these computational burdens by a new approach. Specifically, the elimination of state observer is realized by developing a discrete-time dynamics model of the whole system. In addition, the piezoelectric nonlinearity is considered as a perturbation term and predicted by perturbation estimation technique. The stability of the control system is proved in theory and demonstrated through experimental studies on a prototype system. Experimental results reveal the efficiency of the presented control scheme for the precision positioning control. [ABSTRACT FROM PUBLISHER]

In this paper a practical control scheme is discussed for the positioning and tracking control of a one mass rotary system. The practical controller designed must have high speed performance, high accuracy, robust to disturbance and parameter variation and have high positioning response which always welcome to industry. Hence, a Nominal Characteristic Trajectory Control (NCTF) controller has been proposed to yield high motion control performance and high robustness. This controller does not require exact model and parameter identification which make it easy to design. Basically, NCTF controller consists of a simple structure comprising Nominal Characteristic Trajectory (NCT) and Proportional Integral (PI) Compensator. Apart from a Conventional NCTF controller, the NCTF controller also improves to Continuous Motion NCTF (CM-NCTF) controller. CM-NCTF controller has same design procedure as Conventional NCTF controller and it is able to produce a slightly better performance than the conventional one by producing slightly faster response and smooth tracking performance. To evaluate the controller performance, the Conventional NCTF controller and CM-NCTF controller, was compared to PID control through experiment. [ABSTRACT FROM PUBLISHER]

The paper presents a Model Reference Adaptive Control algorithm for mobile robots with parameter uncertainties and unstructured dynamics to guarantee that a robot can track to desired trajectory asymptotically and avoid jerky. The controller has been designed in two consecutive parts; one is a nonlinear kinematic controller and the other is the model reference adaptive controller using the feedback signal from the mobile robot's actuator. The simulation results show the efficiency and the application ability of the proposed controller. [ABSTRACT FROM PUBLISHER]

In this paper, we propose an online adaptive neural-algorithm to solve the CT nonlinear optimal control problems. Compared to the existing methods, which adopt the architecture with two neural networks (NNs) for actor-critic implementations, only one NN for critic is used to implement the algorithm, simplifying the structure of the computation model. Moreover, we also provide a generalized learning rule for updating the NN weights, which covers the existing critic update rules as special cases. The theoretical and numerical results are given under the required persistent excitation condition to verify and analyze stability and performance of the proposed method. [ABSTRACT FROM PUBLISHER]

This paper proposes a nonlinear control strategy for a hybrid PV-battery system insuring frequency and voltage support of the power system. The hybrid system includes a PV panel and battery connected to three-phase DC-AC inverter via DC-DC boost converter and bidirectional DC-DC boost converter. A synchronous generator represents the power grid. The voltage regulators control DC-DC boost converter and DC-AC inverter while the frequency regulator controls the bidirectional DC-DC boost converter. A conventional MPPT is used to adjust the reference for nonlinear PV voltage regulator. The voltage regulator is designed based on multi-input multi-output exact feedback linearization technique. It consists of a module that uses the terminal voltage deviation to generate q-axis voltage component. A module that maintains the DC-link voltage is also added to generate d-axis voltage component as well. The proposed frequency regulator includes a module that changes the reference signal of a battery current control module when the frequency deviation is significant. The battery current regulator is designed based on partial input-output feedback linearization strategy. The proposed control system is evaluated in simulation. The results reveal that with the proposed control scheme, the PV-battery generator reacts like a conventional synchronous generator when the grid frequency changes considerably. [ABSTRACT FROM PUBLISHER]

Modern day innovations for applications in Life Sciences and Health Care are revolutionizing the public healthcare sector. Long gone are the days when advanced diagnostics were available only for the elite. Bringing these advancements in diagnostics and medical analysis has become the prime focus of governments in developing and under developed countries where the risks of epidemics and poor hygiene are prevalent due to their supernumerary population. The PCR (Polymerase Chain Reaction) machine is one such invaluable tool in diagnostics that can be used to detect a variety of diseases and abnormal medical conditions. This paper presents a simple algorithm for nonlinear PID (Proportional Integral Derivative) temperature control of a Peltier based TEC (Thermo Electric Cooler) that incorporates an additional ambient temperature feedback for optimum operation in a variety of environments with different temperatures. The algorithm uses PID constants that are characterized using polynomial regression from a discrete database of measurements to choose the right value for the right target temperature. The ambient feedback has two roles. Firstly, it is used to divide the control region into two zones for optimum control. Secondly, it is used to slide the entire characteristic appropriately to provide seamless operation in a variety of thermal environments. The proposed algorithm can be used for easy temperature control with an overshoot of less than 0.1° C and an accuracy of +/− 0.1°C for any such similar system, without the mathematical rigor for modelling the entire system. [ABSTRACT FROM PUBLISHER]

In this paper, chaos synchronization problem of the fractional order Coullet system in a master-slave pattern is investigated by using the nonlinear feedback control method. Suitable synchronization conditions are analyzed based on the Lyapunov stability theory. And the synchronization of commensurate order Coullet chaotic system of the base order 0.98 is implemented by virtue of the method. Numerical simulations are provided to verify the performance of the proposed controller. [ABSTRACT FROM PUBLISHER]

This paper presents a control experiment of a vertical jumping motion with 4links Robot. A target system consists of four links and three actuators placed on each joint between the links. This system is fullactuated at the initial step, but as the physical constraint varies in a process of a jumping motion, the system comes to be underactuated. With the control strategy overcoming these difficulties, we conduct experiments with 4links Robot and show the experimental results. [ABSTRACT FROM PUBLISHER]

This paper describes the rising up motion and stabilizing control for Denguribot. Denguribot is the Acrobot composed of two rounded links. The purpose of this paper is to stabilize Denguribot in a standing position from lying down. In order to achieve this purpose, we propose rising up control law using PI controller. Our method is to make an angle of Denguribot track its reference function by partial linearization method to pump up its energy and to update the reference on a Poincare´ section. As a stabilization control law, we approximate Denguribot as the Acrobot and design a stabilization control law for the Acrobot, using exact linearization method. Numerical simulation shows the effectiveness of the suggested method. [ABSTRACT FROM PUBLISHER]

This paper shows the usefulness of the nonlinear controller realizing periodic motion of monorotor UAV by experiments. Monorotor UAV has no equilibrium point. So, the control target is semi-hovering; a motion that passes desired non-equilibrium point at which height and attitude stop periodically. In order to achieve this control objective, we propose discontinuous and time-varying output zeroing controller which allows zero dynamics to be controlled. The numerical simulation and experiments show the validity of suggesting controller design method. [ABSTRACT FROM PUBLISHER]

In this paper revised model of the IEEE working group recommended is used for simulation of transient response of hydro turbine converted to state space model and verification was made using measurements of transients from real Hydro Power Plant (HPP). Nonlinear mixed model controller was designed and implemented into complete HPP simulation model and compared with PID with real parameters used in HPP, and with adjusted PID parameters with consideration of smallest frequency error. Verification of performance of the model was made comparing model response with measured load rejection, which is worst case of HPP operation. [ABSTRACT FROM PUBLISHER]

Development of a mathematical model of air to fuel ratio and control for SI engines has been proposed in various themes to satisfy technical specification. This paper reveals a simple yet effective nonlinear control to enhance the regulator. The mean value engine model (MVEM) is employed and enhanced to validate the effectiveness of the proposed scheme. The regulator is designed using a discrete fuzzy PI algorithm, provided easy tuning, robustness, and rapid development with simple architecture. Effects on dead time, exhausted delay, and chaotic disturbance are also included. The simulation results show satisfactory performance using standard criteria such as an integral of absolute error (ITAE), an integral of square error (ISE) and an integral of absolute control output (IACO) and a mean absolute error (MAE). [ABSTRACT FROM PUBLISHER]

This paper presents a nonlinear control of 900-kW wind power, to track the maximum power point (MPPT,) and control Power Factor Correction (PFC) of wind farm using three Squirrel Cage Induction Generator (SCIG) driven by 300-kW wind turbines. The wind turbine delivers an active and reactive power to grid via common DC-bus and Voltage Source Converter (VSC), the proposed control strategy provides perfect tracking performances of the DC-bus voltage and the active and reactive powers to their references trajectories. The proposed control laws are derived from the Lyapunov approach using backstepping controllers. Finally, the simulation results verify the stability and effectiveness of the control strategy [ABSTRACT FROM PUBLISHER]

In this paper, we will study the output-error-constrained tracking control problem of an electrostatic torsional micromirror beyond the pull-in limit. We will first show that this problem can be formulated as a robust output regulation problem and it further boils down to a robust regulation problem with output-constrained by adaptive internal model design, the solution of which would in turn lead to the solution of the original problem. Then we design a regulation controller for such a regulation problem by using the barrier Lyapunov function technique. Our adaptive control law ensures the electrostatic torsional micromirror with a enhanced tracking performance in the sense that the moveable micromirror can achieve the sinusoidal wave scanning of any frequency up to a full gap operation without contacts of the fixed bottom electrode, and furthermore, the estimated sinusoidal wave frequency converges to its real value. [ABSTRACT FROM PUBLISHER]

According to the characteristics of Reusable Boost Vehicle (RBV) during the large attitude adjusting phase, like strong nonlinearity, strong coupled and multi input-output, the nonlinear modeling is established (with the nonlinearity of aerodynamic coefficients varies with factors fully considered, such as Mach number, attack angle, sideslip angle and so on). A RBV flying control strategy based on neural network robust adaptive inverse is proposed. First, RBV system is completely decoupled using nonlinear dynamic inverse; secondly, the effect of model uncertainty is eliminated using robust adaptive method; finally, the feasibility and validity of the control strategy during the large attitude adjusting phase are verified with nonlinear simulation. [ABSTRACT FROM PUBLISHER]

In this paper, we investigate active, nonlinear and linear matrix inequality(LMI) synchronization methods between two novel unified hyper chaotic systems. Synchronization between the two hyper chaotic systems is achieved based on the corresponding stability theorem. The main contribution of this paper is introducing LMI method to the synchronization of the hyper chaotic systems. Numerical simulations are presented to demonstrate the effectiveness of these methods. [ABSTRACT FROM PUBLISHER]

This paper first emphasizes how the well-known backstepping procedure for constructive nonlinear control design can be adapted to further guarantee some constraints on the output evolution. This approach is then illustrated with the problem of angle or voltage control in a simple Single-Machine-Infinite-Bus model of an electrical network. Various simulations are finally provided accordingly. [ABSTRACT FROM PUBLISHER]

The mechanism of entrainment to natural oscillations in a class of (bio)mechanical systems described by linear models is investigated. A nonlinear control strategy (based on the speed gradient control algorithm) is analyzed providing the system oscillation in resonance mode with a natural frequency. It ensures an energy-optimal entrainment performance robustly against perturbations in system parameters in a finite time. The obtained controller equations can be interpreted as equations of a dynamical neural network. Assuming that the resetting mechanism in animals is selected to ensure a suboptimal entrainment performance, the neural network interpretation may be helpful for understanding the entrainment phenomenon in nature. Efficiency of the proposed entrainment solutions is demonstrated by examples of computer simulation. [ABSTRACT FROM PUBLISHER]

This paper studies the point-to-point liquid container transfer control problem for a PPR robot. A multi-mass-spring model is considered for the characterization of the most prominent liquid sloshing modes. The control inputs are two forces and a torque applied to the prismatic joints and the revolute joint, respectively. The control objective is to control the robot end-effector movement while suppressing the sloshing modes. A nonlinear mathematical model that reflects all of these assumptions is first derived. Then, a Lyapunov-based nonlinear feedback controller is designed to achieve the control objective. Finally, a simulation example is included to demonstrate the effectiveness of the controller. [ABSTRACT FROM PUBLISHER]

In this paper, a quasi-continuous sliding-mode strategy is done which solves the problem of power generation for variable speed wind turbine systems. The control objective is to maximize the extracted energy from the wind while mechanical loads are reduced. The properties of the proposed controller are robustness to parametric uncertainties of the turbine, robustness with respect to external disturbances, robustness to unmodeled dynamics and accuracy, with an accuracy of higher order and finite reaching time. The high-order sliding-mode controller is applied to reduce the effects of chattering in the generated torque that could lead to increased mechanical stress because of strong torque variations. We use a realistic model which takes into account the nonlinear dynamic aspect of the wind turbine and the turbulent nature of the wind. We assume that only the rotor speed and electric power are available from measurements on the wind turbine. In order to validate the mathematical model and evaluate the performance of proposed controller, we used the National Renewable Energy Laboratory aeroelastic wind turbine simulator FAST. Simulation and validation results show that the proposed control strategy has improvements in comparison with the existing controllers. [ABSTRACT FROM PUBLISHER]

In this paper, for a three dimensions autonomous continuous nonlinear dynamical system, the chaotic characteristic and control of chaotic synchronization of model of fractional-order are researched by the theory of fractional-order calculus. The results show that the lowest order of which chaos can occur is 0.855 in this nonlinear dynamic model of fractional-order. Based on the theory of stability of the fractional-order dynamical system, the controller is designed, the control of chaotic synchronization of nonlinear dynamic model of fractional-order is implement and the chaotic synchronization is proved analytically. Finally, the validity of nonlinear controller designed in this paper is verified by numerical simulation using Adams-Bashforth-Moulton arithmetic. [ABSTRACT FROM PUBLISHER]

Mobile two wheeled inverted pendulum (TWIP) robot is one type of mobile robot that have a number of advantages. Because dynamics of a TWIP is a complex nonlinear form, several studies have linearized the dynamic equation at the equilibrium point and designed a controller with linear dynamic equation. The limitation of the approach is, because of ignoring a high order term, the performance of that controller cannot be guaranteed at a point far from equilibrium. This paper discusses the modeling of TWIP systems and shows a new control method with nonlinear dynamics. [ABSTRACT FROM PUBLISHER]

The objective of this paper is to design an effective control scheme for an asteroid orbiting satellite. The paper first introduces the dynamics formulation of such satellites and then provides a framework for the control system design. The control objective is to achieve a nadir pointing attitude on a circular equatorial orbit. Lyapunov-based nonlinear feedback laws are constructed to control the rotational and translational motion of the satellite so that the control objective is achieved. Computer simulations are carried out to illustrate the effectiveness of the control laws. [ABSTRACT FROM PUBLISHER]

This paper studies the thrust vector control problem for an upper-stage rocket with fuel slosh dynamics. The control inputs are the gimbal deflection angle of a main engine and a pitching moment about the center of mass of the spacecraft. It is assumed that the rocket acceleration due to the main engine thrust is large enough so that surface tension forces do not significantly affect the propellant motion during main engine burns. The prominent sloshing modes are represented by a multi-mass-spring model with time-varying parameters. A time-varying nonlinear feedback controller is designed to control the translational velocity vector and the attitude of the spacecraft, while suppressing the sloshing modes. A simulation example is included to illustrate the effectiveness of the controller. [ABSTRACT FROM PUBLISHER]

Input-output linearization and Sliding Mode Control (SMC) theory are applied to the formulation and control of a wind energy generation system with uncertainties which is described in the state space. The equivalent control based SMC and the second-order SMC algorithm are employed to stabilize the system. Conditions are derived to guarantee the stability for the system under the uncertainties. Simulation results verify the strategy proposed. [ABSTRACT FROM PUBLISHER]

In this paper, we consider the environmental boundary tracking problem where the objective is to steering a nonholo-nomic mobile robot to track the desired environmental boundary. Based on kinematic model of the mobile robot, we design a kinematic control law for the robot to track the desired boundary. Kinematic control law needs perfect velocity tracking, which doesn't always hold for mobile robot. So, dynamic control law is designed for the nonholonomic mobile robot to track a designated reference velocity, so as to track the desired environmental boundary. The stability of the designed control laws is verified by Lyapunov theory and Barbalat's Lemma and illustrated by simulation results. [ABSTRACT FROM PUBLISHER]

For those complex nonlinear systems with non-analytical subsystems, gain scheduling control and linear parametric varying control can be utilized for performance improvement over the whole operating envelope. Different from the above two control design methods, this paper proposes an operator-based, generalized minimum variance type of control strategy. The advantage of the proposed method is its ease of design and tuning; more importantly it allows the existence of non-analytical modules in the nonlinear system. Such systems are wide-spread in astronautic, aeronautic and industrial systems, illustrating the potentiality of the proposed design methodology. Finally, a simulation study is provided to validate the effectiveness of the proposed design approach. [ABSTRACT FROM PUBLISHER]

An adaptive approach based on Trajectory Linearization Control (TLC) is introduced to achieve the trajectory tracking of model-scaled helicopter with constant or slow time-varying model uncertainties. In the procedure of the controller designing, estimated parameters are applied to compensate for the uncertain inertial parameters (such as the mass and the inertial matrix) of the helicopter. Stability of the adaptive control system is proved in both constant and time-varying cases. Performances of the closed-loop system are verified by simulation results. [ABSTRACT FROM PUBLISHER]

A new nonlinear tracking controller is presented for an underactuated quadrotor unmanned aerial vehicle (UAV) in this paper. The vehicle is subject to parametric uncertainties. A continuous nonlinear robust control design is combined with an on-line parameter estimation scheme to develop the control law. A Lyapunov based stability analysis is utilized to prove that asymptotic tracking of the quadrotor UAV's position and regulation of yaw orientation are achieved under parametric uncertainties. Compared with sliding mode based control approaches, the proposed control design in this paper is free of chattering. Numerical simulation results of a 6 DOF quadrotor UAV model are included to demonstrate the good tracking performance of the proposed control strategy. [ABSTRACT FROM PUBLISHER]

This paper presents a new continuous nonlinear robust controller for the tracking problem of a class of air-breathing hypersonic vehicles. The vehicle's longitudinal dynamic model contains unstable zero-dynamics, which brings great challenges for the control development. A nonlinear robust design approach is combined with dynamic parameter estimation to improve control performance under model uncertainties. The flight controller requires very limited knowledge of the system dynamic model, and is free of chattering issue. Lyapunov based analysis are utilized to prove that the proposed control laws achieve asymptotic tracking of the vehicle's longitudinal velocity and flight path angle (FPA) under system parametric uncertainties, while keeping all the other signals bounded. Numerical simulation results are provided to validate the performance of the proposed algorithms. [ABSTRACT FROM PUBLISHER]

Quad rotor UAV is a classical multi-input and multi-output system, which is nonlinear, complicated and dynamically unstable. In this paper, quad rotor dynamics is considered to consist of translation and rotation subsystem. Nonlinear control strategy that includes Backstepping method and Slide mode technique for both translational and rotational dynamics are implemented for the quad rotor. The stability of the control design is ensured by Lyapunov global stability theorem. Additionally, in order to improve the dynamic response and avoid the violation of the control input constraints, the piecewise differentiable input is applied instead of the step input for the control of rotational subsystem. The performance of the nonlinear control algorithm is evaluated by simulation. Results from simulation validate effectiveness of the designed control strategy for quad rotor near quasi stationary (hover or near hover) flight. Finally, comparison between Backstepping and Slide mode is carried out briefly to highlight respective characteristics. In addition to that, conclusion is derived for this study and future work is proposed. [ABSTRACT FROM PUBLISHER]

This paper deals with the problem of fuzzy tracking control for a class of nonlinear time-delay systems subject to actuator saturation. The nonlinear systems under consideration are described by T-S fuzzy model, and the time delays are assumed to be constant. The purpose is to design state-feedback fuzzy controllers such that the resulting closed-loop system is locally bounded and its state follows a reference signal. Delay-dependent conditions for the existence of desired controllers are obtained by using the H∞ control method together with a simplified LMI approach. A numerical example is provided to demonstrate the effectiveness of the proposed design method. [ABSTRACT FROM PUBLISHER]

This paper is focused on developing a new approach to nonlinear control synthesis using tangent linearization control and state-dependent Riccati differential equations. Motivated by recent results on tangent linearization control, the nonlinear feedback stabilization problem for nonlinear systems is firstly reduced to that of a feedback stabilizing controller design for linear time-varying systems. And then, a state-dependent Riccati differential equation based approach is presented to design of state-feedback controller of the deduced linear time-varying system. To implement such a controller, only a state-dependent Riccati differential equation with given positive definite initial condition needs to be solved online. Moreover, it is shown analytically that the closed-loop system under the proposed nonlinear feedback is exponentially asymptotically stable. Finally, a numerical example shows the effectiveness of the proposed approach. [ABSTRACT FROM PUBLISHER]

In this paper, we consider the robust output regulation problem with nonlinear exosystems without the assumption that the solution of the regulator equations along the trajectory of the exosystems should be polynomial. Based on the extended concepts of steady-state generator and internal model, a set of sufficient conditions for the solvability of the problem are given. Thus, the result developed in this paper can allow the robust output regulation problem with nonlinear exosystems to accommodate much more general nonlinear given plants including those which contain nonpolynomial nonlinearity. [ABSTRACT FROM PUBLISHER]

Based on sum of squares theory, this paper is concerned with the nonlinear control for a special class of nonlinear systems. The nonlinear state feedback controller with a reduced-order observer is designed via the polynomial-type Lyapunov function and sum of squares optimization toolbox, so that the controlled system has good stability and dynamic characteristics, meanwhile it can suppress various types of external disturbances well. The simulation results verify the effectiveness and feasibility of the design method. [ABSTRACT FROM PUBLISHER]