Control Loop Design Research Articles

Compensator design for corrector magnet power supply of TPS facility

From 2012 to 2015, Taiwan government has a most important technology project is Taiwan Photon Source (TPS), the total budget of TPS fund to over US300 million. It set up a synchrotron storage ring (electron energy of 3.3 GeV, circumference of 518 m, and low emittance) that provides one of the world's brightest synchrotron sources of x-rays. This study presents a compensator design for corrector magnet power supply to avoid limitations in stabilizing the frequency when the machine output current load is valid. A lead-lag compensator had been built in a full-bridge converter to improve the system bandwidth. Lead-lag compensators influence various disciplines, such as robotics, satellite control, automobile diagnostics, and laser frequency stabilization. These components are important building blocks in analog control systems and can also be used in digital control. A 50V output voltage and 10A output current prototype converter is fabricated in the laboratory. From the experimental results, the effectiveness of the control loop design can be verified from the gain margin and phase margin.

Power Stage and Feedback Loop Design for LLC Resonant Converter in High-Switching-Frequency Operation

As converter switching frequencies are moving toward megahertz frequencies for high power density, secondary leakage parasitics that were previously negligible have to be considered in mathematical modeling for LLC resonant converters. At high-switching-frequency operation, the power stage design must take secondary leakage inductance into account because it can affect the input–output voltage gain. In addition, the feedback loop design should consider the effect of the time delay caused by the performance limitation of a digital controller to improve the small-signal model accuracy of the converter. Using the proposed power stage and feedback control loop design considerations, the LLC resonant converter can achieve high power conversion efficiency and stability enhancement at high switching frequencies. All the proposed methods are experimentally verified using a 240-W prototype LLC resonant converter operating at 1-MHz switching frequency.

Sensor faults tolerance control for a novel multi-rotor aircraft based on sliding mode control

This paper deals with the controllers design using a novel siding mode control and proportional–derivative control for the trajectory tracking problem of a new multi-rotor aircraft, which experiences angular velocity sensor faults and external disturbances. The control system is divided into two parts: the inner loop for attitude subsystem and outer loop for position subsystem. For the inner loop, the angular velocity sensor faults, including bias, drift, loss of accuracy, and loss of effectiveness are considered as equivalent mismatched disturbances, while the system internal coupling, nonlinearity, and external disturbances are considered as equivalent matched disturbances. A novel sliding mode control approach is proposed for inner loop controller design, which includes a nonlinear disturbance observer to estimate both mismatched and matched disturbances, a novel switching surface based on the estimation of the mismatched disturbance to counteract its impact, a double power reaching law to attenuate the chattering problem, and a compensation for the matched disturbance to reduce the controller gains. The sensor faults are handled without fault detection and controller reconfiguration, making the method require less computation and easy implementation. The proposed method enhances the robustness without sacrificing the nominal properties. For outer loop, the proportional–derivative approach is used to design the virtual controller. The closed-loop system stability is proved by the Lyapunov theory. Finally, various simulation experiments are shown to validate the effectiveness, robustness, and the superiority of the proposed flight control scheme.

Double Loop Control Design for Boost Converters Based on Frequency Response Data

This paper presents a data driven approach for PI control design based on frequency response data and calculations of stabilizing sets. The geometrical interpretation of the loci of stability margins allows to determine the parameters of a PI controller from a space of achievable specifications, constructed from frequency response data. As illustration for the use of the proposed approach in engineering applications, regulation of the output voltage of a boost power converter circuit under a double loop control strategy is presented. Numerically, it was possible to generate enough amount of data to perform accurate predictions. The key to apply the proposed approach with success was the generation of a Bode diagram for the system with fine resolution, avoiding the explicit necessity for mathematical models.

Control system design of flying-wing UAV based on nonlinear methodology

Abstract In this paper, A fluid vector rudder flying-wing UAV is employed as the design object, so as to study the nonlinear design method and flight validation. For the maneuvering flight control, this paper presents a control structure. This control structure included the inner loop linearization decoupling methods to eliminate the known negative coupling and the outer loop backstepping methods for trajectory tracking control. The stability of the control structure has been proved in this paper. Compared with the traditional backstepping control method, this controller increases the inner loop decoupling structure and retains the aerodynamic damping term which makes the linearized system a weak nonlinear system. This structure can not only reduce the conservatism of the outer loop controller design, but also is convenient for engineering implementation. Simulation and flight validation results show that the proposed control scheme is effective.

Fundamental Analysis of the Perturbation Rejection Characteristics of Single-Input-Multiple-Output Systems Subject to Multiple Perturbations

Single-Input-Multiple-Output (SIMO) systems are found in several applications. Some of the main concerns are (1) the possibility of stabilizing all the outputs and (2) the possibility of attaining independent tracking control of all the outputs. Whereas the first issue can be easily be elucidated, the second has proven to be impossible in all but a few systems. In many cases one practical option is to use the input to drive a main output, taking care that the behavior of the remaining secondary outputs is acceptable. In this configuration, in addition to the features of the main control loop, the perturbation rejection properties of the secondary outputs become important. This article analyzes the structural properties, stability, and perturbation rejection characteristics of SIMO systems. The article presents fundamental conclusions regarding the relationship of the main control loop and the perturbation rejection characteristics of the secondary outputs. A simple and intuitive example is used to show how the theoretical findings can be used to improve the design of the main control loop through its frequency domain characteristics. The results are developed using simple frequency domain theoretical elements, making the findings relevant for both engineering applications and deriving further theoretical developments.

Nonlinear hierarchical control for quad-rotors with rotation matrix

ABSTRACTThis paper develops a nonlinear hierarchical control for quad-rotors to accomplish trajectory tracking manoeuvres. The rotation matrix is applied to represent the attitude of the quad-rotor. The position and attitude loop controls are designed separately. During the position loop control design, an auxiliary system with saturation control project is developed, which can not only ensure a bounded applied thrust, but also preserve the constrained requirement in the command rotation extraction. As an intermediate step, the minimum rotation principle is employed to extract the command rotation matrix. Then, using the property of the rotation matrix, an applied torque with the corresponding initial condition constraint is designed to complete the attitude tracking. Based on the analysis theory of the hierarchical system, it’s proven that, with the developed applied thrust and torque, the tracking errors of the quad-rotor system are asymptotically stable. Finally, simulations illustrate the theoretical results.

Flexible Voltage Support Control with Imbalance Mitigation Capability for Inverter-Based Distributed Generation Power Plants under Grid Faults

The high penetration level of inverter-based distributed generation (DG) power plants is challenging the low-voltage ride-through requirements, especially under unbalanced voltage sags. Recently, a flexible injection of both positive- (PS) and negative-sequence (NS) reactive currents has been suggested for the next generation of grid codes. This can enhance the ancillary services for voltage support at the point of common coupling (PCC). In light of this, considering distant grid faults that occur in a mainly inductive grid, this paper proposes a complete voltage support control scheme for the interface inverters of medium or high-rated DG power plants. The first contribution is the development of a reactive current reference generator combining PS and NS, with a feature to increase the PS voltage and simultaneously decrease the NS voltage, to mitigate voltage imbalance. The second contribution is the design of a voltage support control loop with two flexible PCC voltage set points, which can ensure continuous operation within the limits required in grid codes. In addition, a current saturation strategy is also considered for deep voltage sags to avoid overcurrent protection. Finally, simulation and experimental results are presented to validate the effectiveness of the proposed control scheme.

Modeling and Control of a Low-Speed Flywheel Driving System for Pulsed-Load Mitigation in DC Distribution Networks

This paper details the modeling and development of an improved controller design for a dc flywheel energy storage system (FESS) driving circuit. The driving system is based on a bidirectional buck–boost converter. The modeling of this converter including the parasitic resistances for all the components was carried out. In this model, the equivalent circuit of the machine was integrated in the converter state-space model for improved accuracy and controllability. The system has two operating modes; when the FESS is charging, the converter operates in the buck mode. A controller was designed to regulate the charging rate through controlling the machine’s terminal voltage. In the discharging mode, the converter operates in the boost mode. A current controller takes over to control the injected current from the machine to the dc bus. The detailed design of both control loops was identified. Simulation results show the accuracy of the derived model and the enhanced performance of the FESS. Further, it is shown that the reversal of power-flow direction was performed seamlessly. A hardware prototype of the converter was implemented and the effectiveness of the developed system was experimentally verified. The experimental results are in excellent agreement with the simulation.

A Mathematical Model for Total Power Control Loop of Large PHWRs

A simple low dimensional nonlinear dynamic model for total power control loop of a large Pressurized Heavy Water Reactor (PHWR) is presented in the paper. The model is derived from first principles and it can be utilized for control system studies. The dynamics of reactor and various components and subsystems of the total power control loop are described by ordinary differential equations and difference equations. The developed model is validated using transient datasets obtained from operational $540~MWe$ Indian PHWR, Unit 4 of Tarapur Atomic Power Station, India. The work reported in this paper will be very useful to control system engineers in the controller design and simulation of total power control loop of PHWRs.

Robust gain-scheduled control for unmanned aerial vehicles

The flight dynamics of a modern aircraft are highly nonlinear and vary over the wide flightenvelope of the aircraft. This fact makes it difficult for a single controller to achieve the desired closedloopspecifications. This paper considers gain-scheduling successive loop control design for linear parameter-varying system in terms of linear matrix inequalities. The obtained controller guarantees an efficientunmanned aerial vehicle’s control under external disturbances within the flight envelope. The designprocedure is illustrated by a case study of unmanned aerial vehicle lateral channel control

Design of Oscillation Control Loop With Coarse-Precision Mode Transition for Solid-State Resonant Gyroscope

This paper presents a dual mode oscillation control loop design for a solid-state hemispherical resonator gyroscope (HRG) which uses the hemispherical vibrating shell for detecting the Coriolis force. A desirable control loop needs to be robust, fast, and also to have small driving and frequency noises which may cause significant errors, such as angular random walk. To design a fast and robust oscillation loop for precision gyroscope, a novel approach using a sequential resonance control mode transition is proposed in this paper. The coarse resonance control mode principally consists of phase shifter and limiter, which provides fast startup and tolerant tracking performances. The precision mode uses phase-locked loop for the sake of precision tracking performance. In addition, a theoretical analysis on the designed control loop considering mode transition is presented. In this paper, the tracking performances of the proposed loop are demonstrated via both simulation and experiments. The experimental results using a fabricated HRG verified the effectiveness of the proposed method.

Design of AC–DC PFC High-Order Converters With Regulated Output Current for Low-Power Applications

AC-DC power factor corrector circuits used in low-power applications have to overcome important power quality problems related to crest and power factors as well as total harmonic distortion (THD), and in many cases, they have to exhibit a high degree of output regulation. The design of efficient drivers for low-power applications using high-order converters is considered in this paper. Power factor correction is achieved by imposing a loss-free resistor behavior to SEPIC and Ćuk converters by means of an internal loop based on sliding-mode control, which requires a hysteretic comparator for its implementation. However, with a constant hysteresis width, the system exhibits harmful harmonic distortion in the input line current waveform so that a variable hysteresis window is used instead to avoid this distortion near the zero crossings of the input current. The subsequent analysis of the ideal sliding dynamics around the equilibrium point allows the design of an outer control loop to regulate the output current. Mathematical analysis, numerical simulations, and experimental results are presented to demonstrate the functionality of the proposed technique obtaining a significant improvement in terms of decreasing the THD. A dimmable LEDs driver supplying an HBLEDs string with a wide range of output current regulation illustrates the design.

Position tracking control of switched reluctance motor with adaptive linear element based on current-sharing method

A novel position tracking control strategy is proposed for switched reluctance motor (SRM) in this paper. The control strategy design can be divided into two steps. The first step is the position control loop design for the SRM, which is composed of proportional plus derivative (PD) controller and adaptive linear element (Adaline). The weights of the Adaline are trained with sliding-mode-learning algorithm (SMLA). The position controller has the united merits of the Adaline and sliding mode control (SMC). The second step is the inner current control loop design. The output of the position control loop is considered as the virtual reference current. The virtual reference current is divided into referenced phase current of the SRM with the proposed current-sharing method (CSM). The proposed position tracking control strategy need any model information on the SRM besides the phase number of the SRM. Simulation results certify that the proposed method not only can realize the position tracking of the SRM, but also has high control performance.

High performance AC–DC control power supply for low voltage ride through inverters

This paper presents a control power supply (CPS) design which is used to feed power to the subsystems of a power converter. The CPS design presented here maintains a constant 24V dc output even over a wide (90V rms to 270V rms ) ac voltage variation at its input for a High Power Converter (HPC). The circuit design and closed loop control design of such a CPS are presented. During starting, the power supply to the control circuitry of the CPS in turn is obtained using a separate start-up power supply. The various design issues and details of the on-board power supply and start-up power circuit to ensure the reliable start-up and shut down of the CPS are analyzed. The CPS was tested for wide input voltage range (v in ) and the performance validates the design. The CPS has also been tested for an input side voltage sag and its performance allows the HPC to meet the low voltage ride-through requirements.

Simulation and Analysis of Integral LQR Controller for Inner Control Loop Design of a Fixed Wing Micro Aerial Vehicle (MAV)

The focus of this paper is on the autopilot control loop design of fixed wing Micro Aerial Vehicles (MAVs).The control methodologies used to design the lateral and longitudinal control are based on Proportional Integral Derivative (PID) and Linear Quadratic Regulator (LQR) with integral action control techniques. The design of these controllers is based on the assumption that the system dynamics can be decoupled to longitudinal and lateral dynamics. A nominal model is chosen among many linear models linearized under various operating conditions. The resulting controllers are simulated in MATLAB® SIMULINK® workspace and results are studied. The simulation results show that both the controllers gives satisfactory performances with or without disturbances, but the LQR controller provides better disturbance rejection and exhibits better overall performance.

Two degrees of freedom FOPID control loop design via SMDO algorithm

Two degrees of freedom FOPID control loop design via SMDO algorithm

A Method for Identification of the Equivalent Inductance and Resistance in the Plant Model of Current-Controlled Grid-Tied Converters

Precise knowledge of the plant time constant $L/R$ is essential to perform a thorough analysis and design of the current control loop in voltage source converters (VSCs). From the perspective of the current controller dynamics in the low-frequency range, such plant time constant is also suitable for most cases in which an LCL filter is used. As the loop behavior can be significantly influenced by the VSC working conditions, the effects associated to converter losses should be included in the model, through an equivalent series resistance. In addition, the plant inductance may also present important uncertainties with respect to the value of the VSC L/LCL interface filter measured at rated conditions. Thus, in this paper, a method is presented to estimate both parameters of the plant time constant, i.e., the equivalent inductance and resistance in the plant model of current-controlled VSCs. The proposed technique is based on the evaluation of the closed-loop transient responses of both axes of the synchronous reference frame when a proportional-integral current controller is implemented. The method gives a set of resistance and inductance values that should be employed for a rigorous design of the current controllers. Experimental results validate the approach.

A Temperature-Stable Piezoelectric MEMS Oscillator Using a CMOS PLL Circuit for Temperature Sensing and Oven Control

In this paper, design, analysis, and implementation of a piezoelectric microelectromechanical systems (MEMS) oscillator on an ovenized microplatform is presented. An oxide-refill process is used to compensate the first-order temperature coefficient of frequency of MEMS resonators, as well as to realize thermal isolation structures. The technology enables fabrication of low-power ovenized device fusion platforms using standard silicon on insulator wafers. Utilizing the intrinsic frequency-temperature characteristic of two MEMS resonators, temperature sensing and closed-loop oven-control is realized by phase-locking two MEMS oscillators at an oven-set temperature. The design of the phase-lock control loop is studied using multidomain linear models. Control loop dynamics, noise properties, and nonideal effects are analyzed. Low-power and low-noise phase-locked loop-based control circuitry is designed in 0.18- $\mu \text{m}$ CMOS to interface with the MEMS resonators. Using the developed technology, an oven controlled MEMS oscillator exhibits an overall frequency drift of <8 ppm over −40 °C to 70 °C without the need for system calibration. In addition, the MEMS oscillators exhibit near zero phase noise degradation in closed-loop operation. [2015-0023]

Design of Multiple Feedback Control Loops for a Single-phase Full-bridge Inverter Based on Stability Considerations

Single-phase inverters employ LC filters for the purpose of reducing pulse-width modulation harmonics. The drawback of LC filter is its stability problem at resonance frequency. Passive damping offers simple and reliable solution, but it decreases the overall system efficiency. Active damping is lossless and provides flexibility of controlling the damping performance; however, it is sensitive to parameters variation. This article presents stability analysis of a single-phase full-bridge inverter to improve dynamic performance and stability. Design of LC filter is carried out considering both undamped and damped structures. The effect of filter parameters on pole-zero locations of the inverter is presented, and variation of the phase margin over a wide range of parameters variation is examined. Active damping using closed-loop current control of the full-bridge inverter to mitigate the resonance oscillation is designed and compared with passive damping. The disturbance rejection via dynamic stiffness with and without active damping is examined to justify the proposed current controller. Simulation and experimental results are presented to validate the effectiveness of the proposed design. It is found that the proposed control of the inverter provides excellent voltage regulation with low total harmonic distortion and ensures good performance and robust stability under parameters variation.