Disturbance Rejection Ability Research Articles

Universal finite-time observer based second-order sliding mode control for DC-DC buck converters with only output voltage measurement

DC-DC buck converters are widely used in industrial applications. Practically, there are parametric uncertainties, external disturbances and nonlinear unmodeled dynamics affecting the control performance of the DC-DC buck converters. Worse still, the current sensor may fail to work normally in practice. Taking the factors aforementioned into account, this paper proposes a universal finite-time observer (UFTO) based second-order sliding mode controller with only output voltage measurement in a simple structure for buck converters subject to mismatched disturbances. Firstly, a universal finite-time observer is designed to give the estimations of unmeasurable states including the current inductor and lumped disturbances. Secondly, introducing the estimations, a second-order sliding mode controller is proposed and a rigorous stability of the whole system is presented. Under the proposed finite-time controller, the system obtains a better convergence property and a better disturbance rejection ability comparing with the asymptotic control method. Moreover, the controller has a simple structure, providing convenience for engineers. As a by-product, only voltage sensor is needed, which reduces the cost and improves the fault tolerant ability for the system. Simulation and experimental results are investigated to validate the effectiveness of the proposed control approach.

Analiza niezawodności strategii sterowania w oparciu o kilka obserwatorów stanu rozszerzonego ESO i jej zastosowanie w systemie kontroli regulacji poziomu czworonożnego robota w warunkach zakłóceń i uszkodzeń

The complexity of control algorithms and their vulnerability to disturbances and failures are the main problems that restrict the operations of multi-legged mobile robots in more complex environments. In this paper, a multiple extended state observer (ESO) based control strategy is proposed to achieve stable tilt angle control for quadruped robots under the influence of disturbances and actuator failures. By treating the multiple legs as parallel control objects, more ESOs were added to improve the disturbance rejection ability of the linear active disturbance rejection control (LADRC). Correlation of interactive information about the legs is realized by the synthesis of multiple ESO information. Based on LADRC, this method has the advantages of easy parameter tuning, good robustness, and strong ability to cope with interference and fault conditions. A control system reliability evaluation method was proposed. The reliability and control performance of the multi-ESO based control system under leg stuck failure conditions were systematically analyzed. Simulation and experimental results for the level adjustment control system of a quadruped robot are provided to verify the disturbance rejection ability, feasibility and practicability of the proposed multi-ESO based control method

Adaptive LADRC-Based Disturbance Rejection Method for Electromechanical Servo System

Electromechanical actuator (EMA) exhibits advanced performance in industry, but its dynamic servo responses are constrained by parametric perturbations, load torque variations, and measurement noise. A strong disturbance rejection ability is necessary for EMAs. However, this usually makes them more sensitive to the measurement noise, reducing the steady-state precision. In this article, an adaptive linear active disturbance rejection control (LADRC) controller is proposed to achieve strong antidisturbance performance and reduce noise sensitivity for EMAs. A novel parallel structure is proposed to improve dynamic responses, which replaces the traditional cascade structure of position and speed loops. Aiming to improve the antidisturbance performance, a linear full-order-extended state observer is integrated with the parallel controller, called the LADRC controller. To reduce the difficulty of parameter tuning, the number of tuning parameters of LADRC is reduced to two by a pole placement design. And these two parameters of LADRC can be adjusted adaptively by the hyperbolic tangent function. Finally, the simulation and experimental results are provided to verify the effectiveness of the proposed strategy for EMAs.

Adaptive optimal target controlled infusion algorithm to prevent hypotension associated with labor epidural: An adaptive dynamic programming approach

Patients receiving labor epidurals commonly experience arterial hypotension as a complication of neuraxial block. The purpose of this study was to design an adaptive optimal controller for an infusion system to regulate mean arterial pressure. A state–space model relating mean arterial pressure to Norepinephrine (NE) infusion rate was derived for controller design. A data-driven adaptive optimal control algorithm was developed based on adaptive dynamic programming (ADP). The stability and disturbance rejection ability of the closed-loop system were tested via a simulation model calibrated using available clinical data. Simulation results indicated that the settling time was six minutes and the system showed effective disturbance rejection. The results also demonstrate that the adaptive optimal control algorithm would achieve individualized control of mean arterial pressure in pregnant patients with no prior knowledge of patient parameters.

Radial position control for magnetically suspended high‐speed flywheel energy storage system with inverse system method and extended 2‐DOF PID controller

To achieve high-precision position control for the active magnetic bearing high-speed flywheel rotor system (AMB-HFRS), a novel control strategy based on inverse system method and extended two-degree-of-freedom (2-DOF) proportional–integral–derivative (PID) controller is proposed in this study. First, the inverse system method is employed to decouple the AMB flywheel rotor system with strong non-linear and coupling, into four independent subsystems. Subsequently, extended 2-DOF PID controllers are used to regulate the decoupled subsystems, to obtain good performances of disturbance rejection and tracking simultaneously. In the extended 2-DOF PID controller, a differential signal is produced by a velocity observer to improve the ability of against noise. Finally, the characteristics of stability, tracking, disturbance rejection and robustness of the control strategy proposed are analysed in theory, and its ability and effectiveness to control the radial position of the AMB-HFRS are further studied by simulations and experiments. It is shown that the control strategy proposed can keep the AMB-HFRS suspending stably from static state to the speed of 24,000 rpm, has the advantages of good tracking, high disturbance rejection, strong robustness and good ability of against noise.

Reinforcement learning and non-zero-sum game output regulation for multi-player linear uncertain systems

This paper studies the non-zero-sum game output regulation problem (GORP) for a class of continuous-time multi-player linear systems. Without the knowledge of state and input matrices, the Nash equilibrium solution, N-tuple of feedback control policy, is learned through online data collected along the system trajectories. A key strategy is, for the first time, to combine techniques from reinforcement learning (RL), differential game theory, and output regulation for data-driven control design. Different from the existing literature of adaptive optimal output regulation, the feedforward matrices are considered nontrivial. Theoretical analysis shows the disturbance rejection and tracking ability of the closed-loop system. Simulation results demonstrate the efficacy of the developed data-driven control approach.

Linear active disturbance rejection control for pressurized water reactor power based on partial feedback linearization

Due to nonlinearity and complexity of pressurized water reactor (PWR), the simple and practical controller for PWR is relatively difficult to design. This study discusses a novel compound control scheme that combines the advantages of partial feedback linearization (PFL) and linear active disturbance rejection control (LADRC). First, a second-order linearization model is derived via PFL. Then, LADRC is designed on the basis of the linearization model. Linear extended state observer is developed to estimate ‘generalized disturbance’, which includes model uncertainty and external disturbance. Finally, the controller parameters are optimized by tuning bandwidth. Simulation results show that the combined controller has faster response, fewer overshoots, and better disturbance rejection ability than PID, whereas it guarantees robustness under various reactor operating conditions.

A Lateral-Directional Control Method for High Aspect Ratio Full-Wing UAV and Flight Tests

To solve the lateral-directional control problem of the high aspect ratio full-wing unmanned aerial vehicle (UAV) without an aileron and rudder, a control method is proposed that uses the differential thrust of propellers as the control output and the yaw angle as the controlled attitude angle. Meanwhile, simulation analysis and experimental verification are carried out. First, a lateral-direction mathematical model and a differential thrust of propeller model of the full-wing drone are established. The influence of the aerodynamic derivative C Y β on the lateral-direction mode is analyzed. Second, based on nonlinear dynamic inversion (NDI) and active disturbance rejection control (ADRC) theories, a yaw angle controller that uses the differential thrust of propellers as the control output is designed. Finally, the vector field (VF) method is improved to obtain the straight-line trajectory tracking method satisfying different speeds, and the logic of waypoint switching is given. The research shows that C Y β has a great influence on the dutch roll damping of the drone. For the full-wing configuration, it is feasible to use the yaw angle as the controlled attitude angle without considering the roll angle. The simulation and experimental results show that the designed lateral-directional control method for the high aspect ratio full-wing UAV has a good control effect and disturbance rejection ability. Meanwhile, the control method has less parameters to adjust and less calculation, which is very suitable for engineering applications.

Active Disturbance Rejection Control of a Five-Phase PMSM with Parameters Variation

This paper deals with the Active Disturbance Rejection Control (ADRC) of a five-phase Permanent Magnet Synchronous Motors (PMSMs) to overcome both of sensibility and limited performances of traditional control strategies against parameters variation and environmental disturbances. The proposed control strategy is based on the Extended State Observer (ESO) which is used mainly for estimation and compensation of internal and external perturbations caused by load torque, parameters variation and uncertainties. Then, the estimated total disturbance are compensated in a feed-forward way. According to this information, the ADRC guarantees steady performances, perfects dynamic of the PMSM and improves the disturbance rejection ability. Simulation results highlight the robustness of the suggested control technique and its ability to achieve a good performance under unfavourable conditions.

Design of PI controller for Liquid Level System using Siemens Distributed Control System

The PI controller design for a liquid level system using the weighted geometric center method is discussed. Every real-time process have dead time. This dead time leads to the generation of oscillation in the system response. The oscillation generated due to dead time introduces instability in system performance. This paper presents a tuning method based on calculating a geometric center in the stability region for a higher order system. In this, the stability region calculated by plotting (Kp, Ki)-plane based on boundary locus stability technique. Further centre point computed in the stability locus by a geometric center method. This center point will provide Kp, Ki value for tuning the PI controller. The First Order Plus Dead Time (FOPDT) process considered to elaborate the method for computing the tuning parameters. A nonlinear time-delay system and a plant having time-delay response are controlled in simulation. The performance of the newly obtained PI controller based on weighted geometric center method is compared with the existing results to show the usefulness of the control scheme. Moreover, disturbance rejection ability of the newly obtained PI controller based on weighted geometric center method is demonstrated by applying disturbances. In addition, the designed controller implemented using Siemens DCS PCS7 V8.1 platform.

Adaptive neural tracking control for automotive engine idle speed regulation using extreme learning machine

The automotive engine idle speed control problem is a compromise among low engine speed for fuel saving, minimum emissions and disturbance rejection ability to prevent engine stall. However, idle speed regulation is very challenging due to the presence of high nonlinearity and aging-caused uncertainties in the engine dynamics. Therefore, the engine idle speed system is a typical uncertain nonlinear system. To address the problems of inherent nonlinearity and uncertainties in idle speed regulation, an extreme learning machine (ELM)-based adaptive neural control algorithm is proposed for tracking the target idle speed adaptively. The purpose of ELM is to rapidly deal with the uncertain nonlinear engine system. Since the original ELM is not designed for adaptive control, a new adaptation law is designed to update the weights of ELM in the sense of Lyapunov stability. Experiment is conducted to validate the performance of the proposed control method. Experimental result indicates that the ELM-based adaptive neural control outperforms the classical proportional–integral–derivative (PID), fuzzy-PID and back-propagation-neural-network-based controllers in terms of tracking performance under the variation of engine load.

Research into the Automatic Berthing of Underactuated Unmanned Ships under Wind Loads Based on Experiment and Numerical Analysis

With the continuous improvement of unmanned ship automation requirements, research into the automatic berthing of underactuated unmanned ships has important theoretical significance and practical value. In order to determine the trajectory of unmanned ships, the line of sight (LOS) algorithm was applied due to the characteristics of underactuated unmanned ships without side thrusters. In order to resist wind disturbance, the active disturbance rejection control (ADRC) method was applied to keep the ship moving on its intended trajectory. Then, to carry out the simulation analysis before the tank experiment, a remote-control simulation system based on a user datagram protocol (UDP) communication was built, and the ability of the ADRC controller to make the ship perform completely automatic berthing in both wind and no wind conditions was verified in simulations. Combined with the simulation results, a tank experiment was accomplished at the Japanese National Research Institute of Fishery Engineering. The experimental results also showed that the ADRC controller has good robustness, that the problems of insufficient autonomous route determination and the disturbance rejection ability in the process of the automatic berthing of underactuated unmanned ships are solved, and the safety of ship navigation is improved, which lays a theoretical and experimental foundation for the further development of unmanned ship control.

Control of Supercritical Organic Rankine Cycle based Waste Heat Recovery System Using Conventional and Fuzzy Self-tuned PID Controllers

This research develops a supercritical organic Rankine cycle (ORC) based waste heat recovery (WHR) system for control system simulation. In supercritical ORC-WHR systems, the evaporator is a main contributor to the thermal inertia of the system, which is greatly affected by transient heat sources during operation. In order to capture the thermal inertia of the system and reduce the computation time in the simulation process, a fuzzy-based dynamic evaporator model was developed and integrated with other component models to provide a complete dynamic ORC-WHR model. This paper presents two control strategies for the ORC-WHR system: evaporator temperature control and expander output control, and two control algorithms: a conventional PID controller and a fuzzy-based self-tuning PID controller. The performances of the proposed controllers are tested for set point tracking and disturbance rejection ability in the presence of steady and transient thermal input conditions. The robustness of the proposed controllers is investigated with respect to various operating conditions. The results show that the fuzzy self-tuning PID controller outperformed the conventional PID controller in terms of set point tracking and disturbance rejection ability at all conditions encountered in the paper.

Practical disturbance rejection control for boiler-turbine unit with input constraints

With the increase of renewable sources participating into the power grid, the traditional thermal power generation is responsible for the frequent power regulation where the disturbance rejection ability should be enhanced during the operation. The boiler-turbine unit is a non-strictly proper multivariable plant with uncertainties, external disturbances and hard constraints, which make the conventional control strategy hard to meet the operating requirement. To this end, an advanced control strategy of generalized active disturbance rejection control (GADRC) is proposed in this paper, consisting of multivariable extended state observer (MESO) and anti-windup compensator. A simple transformation approach is proposed, which can convert the output disturbances involving the feedthrough item into the input lumped disturbances, so that their impact can be estimated by the MESO and compensated by the proposed GADRC. In addition to this, a setpoint filter is developed in the control structure to remove the tracking offset caused by the unknown disturbances and a novel anti-windup strategy is presented to handle the input saturation problem and alleviate the resulting fuel waste issue. The robust stabilities of the proposed GADRC including feedback control and anti-windup control are guaranteed using frequency domain method and Circle criterion, respectively. Simulation studies compared with other methods demonstrate the effectiveness of the proposed control strategy on the boiler-turbine unit, especially in complex cases of external disturbance and model-plant mismatches.

A Composite Sliding Mode Controller for Wind Power Extraction in Remotely Located Solar PV–Wind Hybrid System

Ensuring electrification of remote locations continues to be a major challenge for power engineers. To deal with the effect of intermittent nature of wind, this paper presents the design and implementation of a composite sliding mode controller (CSMC) for a battery energy storage (BES) supported solar photovoltaic (PV)–wind hybrid system in a remote location. This control technique comprises of a soft-switching sliding-mode observer (SS-SMO) and a nonsingular terminal sliding mode controller (NTSMC). The SS-SMO is used to observe the disturbances, whereas the NTSMC is used as a speed controller. The chattering problem caused by the conventional sliding mode controller is alleviated by replacing the conventional signum switching function with the smooth hyperbolic tangent function in disturbance observer loop. The fast and finite time convergence NTSMC based speed controller along with the SS-SMO based disturbance rejection unit, serves the benefits of CSMC. This technique exhibits robustness against model uncertainties and external disturbances. Moreover, the complexity of the system is reduced by replacing the mechanical speed and position sensors with parameter estimation. A double-stage configuration using a dc/dc boost converter is adopted for a PV system. A comparative analysis is presented between the proposed and conventional techniques. A prototype of the hybrid system is developed in the laboratory with permanent magnet synchronous generator. The CSMC-based controller with disturbance rejection ability is implemented to harvest peak wind power. A perturb and observe maximum power point tracking technique is adopted to harvest peak solar power. A voltage control technique is adopted to maintain the voltage at the point of common coupling.

Performance Enhancement of RCS and Application to Tracking Control of Chuck-Workpiece Systems

This paper presents a linear-extended-state-observer-based repetitive control (RC) method to enhance the disturbance rejection performance and tracking performance for a nonlinear system with aperiodic uncertainties and disturbances. Both design scenarios, i.e., with and without a detailed mathematical model of the plant, are considered, respectively. The proposed method exhibits the following three attractive features. First, instead of tuning the observer gain via the bandwidth idea by trial and error, available information on the plant model is used to design the observer gain and the state-feedback RC gains. As a result, the disturbance rejection ability is elevated. Second, robust stability and learning efficiency are adjusted preferentially through two tuning parameters, which effectively improve both the transient and steady-state performance. Third, the observer gain and state-feedback RC gains are simultaneously optimized through an optimization algorithm, in which an index is introduced to evaluate the overall system performance. The design procedure of the system is presented in detail. Finally, an application to tracking control of a chuck-workpiece system demonstrates the validity of the proposed method. Comparisons with the conventional RC method, the standard extended-state-observer-based RC method, and a linear active-disturbance-rejection-control-based RC method show that the proposed method can achieve the best disturbance rejection performance.

Active Disturbance Rejection Control for Bearingless Induction Motor Based on Hyperbolic Tangent Tracking Differentiator

To meet the operation requirements of a bearingless induction motor (BIM) control system, such as fast speed response, stable suspension, and high disturbance rejection ability, an active disturbance rejection control (ADRC) strategy based on hyperbolic tangent tracking differentiator (HTTD) is proposed. First, based on the air-gap magnetic field decoupling control of the BIM, the uncertainties of the system itself and the load disturbance are regarded as a total disturbance. The extended state observer (ESO) is used to observe the total disturbance in real time. The speed ADRC and suspension ADRC are designed for the torque winding and suspension winding, respectively. Second, the hyperbolic tangent function is applied to the tracking differentiator (TD) of ADRC to simplify its structure. The frequency characteristic curves are analyzed through the sweep-frequency test, and the design parameters are further determined. Finally, this strategy is analyzed with simulation in MATLAB/Simulink and verified on an experimental prototype. Both simulation and experimental results show that the strategy not only has good speed and current characteristics but also reduces the effect of load disturbance on the system and improves the suspension characteristics of the BIM.

Fuzzy logic approach for smooth transition between grid-connected and stand-alone modes of three-phase DG-inverter

In distributed generation systems, the worst case of operation is a sudden transition between Grid-Connected mode (GC) and Stand-Alone mode (SA). In this situation, system state variables, such as abrupt changes in currents, risk to contribute to the destruction of the whole power system. In this work, the use of the Fuzzy Logic (FL)-based approach for smooth transition between GC and SA is investigated. In contrast with the classical approach where the transition is a direct and abrupt change from the GC control mode to the SA mode, the Fuzzy Logic Algorithm (FLA) allows generating a feasible reference trajectory that ensures smooth transition between GC and SA modes through a unified control. Furthermore, the FL is employed to tune the voltage loop control in order to increase the disturbance rejection ability of the voltage loop. Also, the control design and the trajectory planning principle are detailed. The effectiveness of the proposed control is validated by simulation tests and its performance is compared to a conventional control scheme.

LabVIEW Based Level Control of Coupled Tank System

This paper utilizes Variable Structure Control (VSC) to control the level of a two tank system. By using Sliding Mode Technique in VSC, the levels of the tanks are maintained at a desired setpoint. The system is subjected to the conventional PID controller and the results are brought out. To track the robustness of the system, an external disturbance is intentionally introduced. The ability of disturbance rejection is checked in both VSC and PID controllers. It is found that VSC offers quick settling time, low peak overshoot and low rise time, and as compared to PID control. LabVIEW(Laboratory Virtual Instrument Workbench) is the software used for the control of the whole process. This is very user friendly software. It uses Graphical programming technique. As an extension the control can be implemented by hardware using DAQ cards.

Active Disturbance Rejection Control Applied to High-order Systems with Parametric Uncertainties

Active disturbance rejection control (ADRC) is an emerging control technique known for its simplicity and good disturbance rejection ability. It has been applied to first- and second-order systems in many areas. However, the application of the ADRC to high-order systems is few and also challenging because the existing bandwidth tuning method is unable to determine proper controller parameters to achieve desired system performance. To address this problem, a new method is proposed to tune the ADRC for controlling high-order systems. First, the ADRC is decomposed into a controller and a prefilter in the frequency domain. Second, they are tuned to satisfy prescribed performance specifications. Two applications of the ADRC to high-order hydraulic systems are presented. It is shown that the proposed method greatly improves the performance of the ADRC compared to the bandwidth tuning method.