Feedback Linearization Approach Research Articles

Robust Nonlinear Controller Design for Three-Phase Grid-Connected Photovoltaic Systems Under Structured Uncertainties

This paper presents a robust nonlinear controller design for a three-phase grid-connected photovoltaic (PV) system to control the current injected into the grid and the dc-link voltage for extracting maximum power from PV units. The controller is designed based on the partial feedback linearization approach, and the robustness of the proposed control scheme is ensured by considering structured uncertainties within the PV system model. An approach for modeling the uncertainties through the satisfaction of matching conditions is provided. The superiority of the proposed robust controller is demonstrated on a test system through simulation results under different system contingencies along with changes in atmospheric conditions. From the simulation results, it is evident that the robust controller provides excellent performance under various operating conditions.

An optimal and intelligent control strategy for a class of nonlinear systems: adaptive fuzzy sliding mode

In this paper, an optimal adaptive fuzzy sliding mode controller is presented for a class of nonlinear systems. In the proposed control, in the beginning, the boundaries of parametric uncertainties, disturbances and un-modeled dynamics are reduced using a feedback linearization approach. Next, in order to overcome the remaining uncertainties, a sliding mode controller is designed. Mathematical proof shows that the closed-loop system with the proposed control is globally asymptotically stable. Using sliding mode control causes the undesirable chattering phenomenon to occur in the control input. Next, in order to remove the undesirable chattering phenomenon, an adaptive fuzzy approximator is designed to approximate the maximum boundary of the remaining uncertainties. Another mathematical proof shows that the closed-loop system with the proposed control is globally asymptotically stable in the presence of structured and unstructured uncertainties, and external disturbances. Finally, the self-adaptive modified bat algorithm is used to determine the coefficients of the adaptive fuzzy sliding mode control and the coefficients of the membership functions of the adaptive fuzzy approximator. To investigate the performance of the proposed controller, an inverted pendulum system is used as a case study. Simulation results verify the desirable performance of the optimal adaptive fuzzy sliding mode control.

Optimal regulation of a cable robot in presence of obstacle using optimal adaptive feedback linearization approach

SUMMARYOptimal path planning of a closed loop cable robot, between two predefined points in presence of obstacles is the goal of this paper. This target is met by proposing a new method of optimal regulation for non linear systems while Dynamic Load Carrying Capacity (DLCC) of the robot is supposed as the related cost function. Feedback linearization is used to linearize the system while Linear Quadratic Regulator (LQR) is employed to optimize the DLCC of the system based on torque and error constraints. Obstacle avoidance for both the end-effector and cables is also considered by the aid of designing an adaptive local obstacle avoidance controller. As a result of linearized nature of the proposed optimal regulation and obstacle avoidance, fast calculation for real time applications is possible. Therefore, formulation of the optimal feedback linearization, together with calculating the DLCC of the robot based on the presented constraints is derived. Finally, a simulation study is performed to study the optimal dynamics and also the maximum DLCC of the cable robot in presence of obstacles. Simulation results are eventually compared with experimental tests conducted on IUST Cable Suspended Robot (ICaSbot) to verify the validity and efficiency of the proposed optimal controllers.

A novel method for recording the position and orientation of the end effector of a spatial cable-suspended robot and using for closed-loop control

In this paper, a new method of recording the position and orientation of the end effector as a feedback of a spatial cable-suspended robot is presented based on coupling the data of image processing and laser sensors. All of the degrees of freedoms (DOFs) of the end effector can be easily fed back through the proposed protocol in an online way and with the highest accuracy. This method has advantages over encoder feedback method since encoder feedback method does not consider the effect of structural uncertainties like vibrations of the cables. Also, the proposed method is preferable to ultrasonic sensor feedback method or accelerometers, because it does not suffer from the effect of reflecting the sound from obstacles and indoor small room syndrome or the accelerometer noise problems. It is possible to use this setup in almost every environmental situation and for any configuration of the end effector. The position and orientation of the end effector recorded in an online way are used to prepare a feedback signal and control the robot in a closed-loop way using feedback linearization approach. A simulation study is carried out on the ICaSbot which is a spatial cable-suspended robot. Finally, experimental tests are conducted on the ICaSbot to validate the proposed algorithm and simulation results performed in the MATLAB environment.

Hybrid Control of Liquid-Filled Spacecraft Maneuvers by Dynamic Inversion and Input Shaping

In this paper, a hybrid control method for partially liquid-filled spacecraft maneuvers is proposed. This control scheme integrates the command input shaping technique and the feedback linearization method to guarantee the implementation of the maneuver task for spacecraft to yield the desirable suppression of liquid fuel slosh. The coupled slosh spacecraft in attitude maneuver carrying a sloshing liquid is considered as a multibody system with the sloshing motion modeled as a spherical pendulum. Nonlinearly coupled equations of attitude and orbital motion are presented for the partially liquid-filled spacecraft undergoing fuel slosh. A feedback linearization approach is applied to transform the nonlinear system dynamics into a linear system (inverse dynamics of the original system or so-called dynamics inversion) to compute the input corresponding to the reference output. Dynamic inversion and input shaping techniques are used to design a controller for the reference tacking maneuver of spacecraft with fuel sloshing. Numerical simulation results are presented to confirm the effectiveness of the proposed hybrid control method.

Adaptive PID controller design guidelines for a class of non-linear systems

In this paper, the systematic model reference adaptive PID (APID) controller design for a class of uncertain non-linear systems is discussed. The exact linear system based upon feedback linearisation approach is employed to establish the equivalent linear model of the process, which is then employed to develop the controller. In order to demonstrate the performance of the proposed technique, the trajectory tracking of the single arm robot manipulator subjected to process uncertainties and input disturbance is conducted. Simulation results illustrate the superior performance of the APID algorithm achieving the targets by fully eliminating the severe load disturbance exerted to the robot consuming feasible amount of control energy. This remarkable performance proposes it as an effective robust control strategy in online and/or offline precise servo control applications.

Output-feedback control of arc length for manual gas metal arc welding with higher order sliding modes

This paper explores the design of a non-linear output-feedback control technique based on the higher order sliding mode approach for an uncertain manual gas metal arc welding (GMAW) system. To cope with the large uncertainties affecting the dynamics of the system and the rapid changes in contact tip to workpiece distance (CT) caused by the uneven movement of the welding gun by the operator, an output-feedback control system has been developed with an observer-controller that combines the second order sliding mode (SOSM) controllers and an SOSM differentiator. A non-linear single input single output (SISO) system model has been considered here for the design. Thus, the robust output feedback controller with observer is proposed here, which has been compared with an earlier proposed classical feedback linearisation approach. Simulation results are presented and discussed in order to establish a framework for comparison.

Decentralized Robust Feedback Linearization Control Based on Integrity

Decentralized Robust Feedback Linearization (DRFL) approach based on integrity for multivariable systems is presented. It uses a model observer to compensate the non-modeled dynamics, system uncertainties, and external disturbances of a system. Firstly, the existence of DRFL controllers with integrity is examined. Then, stable regions of each DRFL controller parameters are calculated, and some parameters are obtained by placing suitable closed-loop poles, for meeting the design specifications for the whole control system. The proposed method is applied to an illustrative example. Results demonstrate that DRFL control is feasible and robust for complicated multivariable systems.

Quasi-Sliding Mode Control of a High-Precision Hybrid Magnetic Suspension Actuator

A novel 1-DOF hybrid magnetic suspension actuator for precise motion control is presented. The actuator is designed to achieve sub-micron positioning accuracy over a range of motion in excess of 1000 µm while avoiding large nominal levitation currents and iron core saturation. The proposed passive push-active pull configuration offers precise motion control with moderate actuator effort when a payload is to be accurately suspended over a large range of travel. The proposed actuator can be used modularly to control multiple axes of motion in a multi-DOF positioning application that requires millimeter-range travel with submicron accuracy. A Quasi-Sliding Mode controller (QSM) is presented in which the sliding mode dynamics are directly designed, as opposed to the typical Lyapunov function approach that is solely based on stability. Since full knowledge of the state vector is required, a nonlinear high-gain observer was also designed and implemented. Performance of the QSM algorithm in controlling the proposed actuator is compared to that of a PID controller with standard feedback linearization. Several experiments are conducted to demonstrate both the positioning and tracking capabilities of the proposed actuator. The proposed QSM method shows better transient performance than the standard PID feedback linearization approach. QSM also shows better tracking performance, which is highly desirable in systems in which fast and accurate motion control along a desired path is critical.

Nonlinear dynamics and control of bifurcation to regulate the performance of a boiler–turbine unit

The economical operations of power plants and environmental awareness are the major factors affecting the importance of control in boiler–turbine units. In this paper, a multivariable nonlinear model of boiler–turbine unit is considered. Drum pressure, electric output and water level of drum (as output variables) are adjusted at desired values by manipulation of valve positions for fuel, steam and feed-water flow rates (as input variables). Nonlinear dynamics of the unit is investigated through the concepts of bifurcation and limit cycles behaviour. In the presence of harmonic disturbances, some coefficients of the dynamic model, fuel and steam flow rates play as the bifurcation parameters. It is shown that variation of bifurcation parameters leads to the occurrence of secondary Hopf (Neimark) and symmetry-breaking bifurcations (in drum pressure or electric output). To improve the aperiodic and quasi-periodic behaviour of the system to the stable periodic one, a control regulator is designed based on feedback linearization approach. It is shown that the controller acts efficiently in disturbance rejection and guarantees the stable periodic solutions with low oscillatory behaviour (which is essentially demanded by the power grid).

Adaptive trajectory tracking control of wheeled mobile robots with disturbance observer

SUMMARYIn this paper, the trajectory tracking problem for a wheeled mobile robot in the presence of kinematic and dynamic uncertainties has been addressed. Uncertainties are modeled as lumped disturbances. A kinematic controller based on feedback linearization approach and a dynamic controller based on model reference adaptive control are designed in the presence of disturbances. In order to ensure both robustness and implementability of the controllers, the disturbances are estimated by a generalized linear matrix inequality‐based disturbance observer. Simulation results show the effectiveness of the proposed method. Copyright © 2013 John Wiley & Sons, Ltd.

Workspace trajectory tracking control for two-flexible-link manipulator through output redefinition

In this paper, a control strategy and stability analysis for two-flexible-link manipulator are presented to track a desired trajectory in the workspace. The inverse dynamics problem is solved using virtual space and the quasi-static approach. Flexible manipulators are non-minimum phase systems when the controlled output is the tip position. To overcome this problem, an output redefinition technique is used. Two steps are presented to control the manipulator’s tip position. First, assuming that the first link is stable, we develop the control law for the last link to stabilise the error dynamics using the feedback linearisation approach. The weighted parameter defining the non-collocated output is selected to guarantee bounded internal dynamics such that the output is as close as possible to the tip. Second, the same strategy is followed for the first link. Simulation results are presented to show good tracking of desired trajectory in the workspace.

FEEDBACK LINEARIZATION-BASED ADAPTIVE FUZZY SLIDING MODE CONTROL OF MEMS TRIAXIAL GYROSCOPE

In this paper, a fuzzy logic adaptive sliding mode control using feedback linearization approach is proposed for the micro-electro mechanical systems triaxial gyroscope with unknown system non-linearities.

Tracking Controller Design for Diving Behavior of an Unmanned Underwater Vehicle

The study has investigated the almost disturbance decoupling problem of nonlinear uncertain control systems via the fuzzy feedback linearization approach. The significant dedication of this paper is to organize a control algorithm such that the closed-loop system is active for given initial condition and bounded tracking trajectory with the input-to-state stability and almost disturbance decoupling performance. This study presents a feedback linearization controller for diving control of an unmanned underwater vehicle. Unmanned underwater vehicle proposes difficult control subject due to its nonlinear dynamics, uncertain models, and the existence of disturbances that are difficult to measure. In general, while investigating the diving dynamics of an unmanned underwater vehicle, the pitch angle is always assumed to be small. This assumption is a strong restricting constraint in many interesting practical applications and will be relaxed in this study.

Electronic Throttle Control System: Modeling, Identification and Model-Based Control Designs

Electronic throttle control (ETC) system has worked its way to becoming a standard subsystem in most of the current automobiles as it has contributed much to the improvement of fuel economy, emissions, drivability and safety. Precision control of the subsystem, which consists of a dc motor driving a throttle plate, a pre-loaded return spring and a set of gear train to regulate airflow into the engine, seems rather straightforward and yet complex. The difficulties lie in the unknown system parameters, hard nonlinearity of the pre-loaded spring that pulls the throttle plate to its default position, and friction, among others. In this paper, we extend our previous results obtained for the modeling, unknown system parameters identification and control of a commercially available Bosch’s DV-E5 ETC system. Details of modeling and parameters identification based on laboratory experiments, data analysis, and knowledge of the system are provided. The parameters identification results were verified and validated by a real-time PID control implemented with an xPC Target. A nonlinear control design was then proposed utilizing the input-output feedback linearization approach and technique. In view of a recent massive auto recalls due to the controversial uncontrollable engine accelerations, the results of this paper may inspire further research interest on the drive-by-wire technology.

Visual Servoing Tracking Control of a Ball and Plate System: Design, Implementation and Experimental Validation

This paper presents the design, implementation and validation of real-time visual servoing tracking control for a ball and plate system. The position of the ball is measured with a machine vision system. The image processing algorithms of the machine vision system are pipelined and implemented on a field programmable gate array (FPGA) device to meet real-time constraints. A detailed dynamic model of the system is derived for the simulation study. By neglecting the high-order coupling terms, the ball and plate system model is simplified into two decoupled ball and beam systems, and an approximate input-output feedback linearization approach is then used to design the controller for trajectory tracking. The designed control law is implemented on a digital signal processor (DSP). The validity of the performance of the developed control system is investigated through simulation and experimental studies. Experimental results show that the designed system functions well with reasonable agreement with simulations.

Nonlinear dynamics, bifurcation and performance analysis of an air-handling unit: Disturbance rejection via feedback linearization

Nowadays, dynamic analysis of air-conditioner units is essential to achieve satisfactory comfort conditions in buildings with low energy consumption and operation cost. In this paper, a nonlinear multi input–multi output model (MIMO) of an air-handling unit (AHU) is considered. In the presence of realistic harmonic disturbances, nonlinear dynamics of AHU is investigated. The effect of various thermodynamics and geometrical parameters on limit cycles behaviour of the indoor temperature is investigated. It is observed that the indoor space volume plays as the bifurcation parameter of the system. Decreasing the indoor space volume leads to the occurrence of secondary Hopf (Neimark) bifurcation and consequently the unstable quasi-periodic solution of the indoor temperature. To overcome this problem, a multivariable control strategy based on feedback linearization approach is implemented, in which the air and cold water flow rates are the control inputs while the indoor temperature and relative humidity are the control outputs. It is shown that the designed controller guarantees the comfort indoor conditions by preventing the unstable quasi-periodic responses and improving the limit cycles behaviour.

Fault Ride-Through Enhancement of DFIG-Based Wind Generation Considering Unbalanced and Distorted Conditions

A control strategy is proposed to enhance the operation, under network disturbances, of a wind turbine driven doubly fed induction generator (DFIG). The scheme allows us to overcome low voltages, imbalances, and harmonic distortions at the point of common coupling. The control law is designed using a feedback linearization approach plus resonant filters; this law directly controls the DFIG stator powers from the rotor voltages, unlike the most used nested two-loop approaches. An accurate control of the active and reactive powers delivered to the grid permits us to fulfill severe grid code requirements and to improve the fault ride-through capability. Under unbalanced conditions, the reference currents of both grid- and rotor-side converters are coordinately chosen to simultaneously eliminate the double-frequency pulsations in the total active power and electromagnetic torque. Several tests and disturbances to provide a realistic assessment and validation have been performed, showing the adequacy of the proposed controller. Comparisons with other control approaches with different objectives are also presented to illustrate the advantages regarding elimination of the double-frequency ripples and harmonic rejection capability.

Decentralized high order sliding mode control of multimachine power systems

In this paper, feedback linearization approach and high order sliding mode control are combined to stabilize and decentralize nonlinear multimachine power systems. The design control permits to decentralize and handle the nonlinearities of power systems model by using the feedback linearization approach and HOSM control to each generating unit in the global system for stabilizing the system. Each machine is modeled as an independent uncertain dynamic subsystem where the uncertainty is a disturbance that represents the effects of the rest of the system on that particular machine. This disturbance is estimated by numerical method. A local high order sliding mode stabilizer is designed to regulate the machine angle of each generating unit under high level external disturbances. This method is illustrated with a three-machines infinite bus power system. Simulations show that the proposed (DHOSMC) provides high-performance in dynamic characteristics and its robustness with regard to external disturbance.

Modeling and multi-loop feedback control design of a SEPIC power factor corrector in single-phase rectifiers

In this paper, a comparative analysis of three multi-loops control schemes dedicated to the single ended primary inductance converter (SEPIC) power factor corrector (PFC) is presented. The first control technique uses a robust hysteresis current controller; the second control strategy consists of a frequency–domain linear design of regulators on the basis of a small-signal averaged model of the converter, whereas the third control design method uses the input/output feedback linearization approach applied on the large-signal state-space averaged model of the converter. In order to verify and compare the performance of all control schemes, numerical simulations are carried out on a switching-functions-based model of the converter, which is implemented using Matlab/Simulink. The control systems are tested under both rated and disturbed operating conditions. The systems performance is evaluated in terms of source current total harmonic distortion (THD), input power factor, and DC voltage regulation toward load disturbances.