Adaptive Loop Research Articles

A sliding mode speed and position observer for a surface-mounted PMSM

To improve the speed and position observation performance of a Surface-Mounted Permanent Magnet Synchronous Motor (SM-PMSM), an improved sliding mode observer (SMO) based on the adaptive synchronization filter (ASF) and quadrature phase-lock loop (QPLL) is proposed. An adaptive synchronous filter based on feedback rotor position estimation from a QPLL is proposed to extract the fundamental signal of the back electromotive force (back-EMF). Then, a QPLL is linked to calculate the rotor position and speed according to the fundamental signal of the back-EMF, in order to effectively suppress the estimated harmonics and chattering and improve the observation accuracy of speed and position. Finally, the effectiveness and feasibility of the proposed observer approach are verified by simulation and dSPACE.

A 1.25–12.5 Gbps Adaptive CTLE with Asynchronous Statistic Eye-Opening Monitor

The equalization of a large attenuation signal and multirate communication in high-speed serial interface is hard to balance. To overcome this difficulty, an adaptive equalization system with optimized eye-opening monitor is proposed. The designed eye-opening monitor is based on the asynchronous statistic eye diagram tracking algorithm, and the eye diagram is obtained by undersampling with the low-speed asynchronous clock. With the eye-opening monitor into the adaptive loop, an adaptive equalization system combined with continuous-time linear equalization (CTLE) is completed. And the inductor peaking technology is used to improve the capacity of compensation. With SMIC 28 nm CMOS process to achieve the overall design, the power consumption and core chip area are 12 mW @ 12.5 Gbps and 0.12 mm2, respectively. And postsimulation results show that it can offer compensation from 6 to 21 dB for 1.25–12.5 Gbps range of receiving data, which achieves a large range of data rate and channel loss, and its power efficiency is 0.046 pJ/bit/dB for the worst case, which is better than most previous works.

Frequency tracking loop with wide pull‐in range for weak DSSS signal

A frequency tracking loop based on triangle function frequency discriminator and adaptive loop bandwidth adjustment is proposed to track the Doppler frequency of weak direct-sequence spread spectrum (DSSS) signal. The proposed structure first provides a frequency discrimination with wide pull-in range to lock the large residual frequency offset after acquisition. Then, the adaptive loop bandwidth adjustment is employed to improve the accuracy of frequency estimation. Compared with the conventional tracking loop, the proposed structure has wider pull-in range and higher sensitivity. Simulation results verify the validity of the proposed method.

FUZZY SUPERVISOR FOR PID CONTROLLER

Introduction: PID regulators are an important industrial automation tool. However, the traditional ways of their customization involve experiments with the plant, reducing the control system efficiency when the operating conditions change. To solve this problem, you have to use an adaptation loop which automatically changes the regulator parameters when the quality indicators deteriorate. Purpose: Developing a structure and an algorithm for a fuzzy supervisor of a PID controller in order to improve the operation quality in the context of uncontrolled changes in the plant parameters. Results: We propose two options for organizing a fuzzy supervisor. The first option involves continuous changing of the controller parameters based on the information about the current control error. The supervisor is trained offline with the help of a genetic algorithm. This approach makes the application universal, but the resulting structure is a black box. The second option is using transient process quality estimates; it can be used when the input signal periodically changes. The controller parameters are changed using fuzzy rules with clear semantics. It is shown that systems with a fuzzy supervisor can reduce the overshoot or static error which both can occur when the control object parameters change. The system operation was simulated using MatLab Simulink. Practical relevance: The use of PID controllers with fuzzy supervisors can be useful in the design of control systems for a wide range of dynamic plants.

A grid-tie PV inverter with the ability to improve power quality under unbalanced and distorted source voltage conditions

ABSTRACTThis paper proposes a grid-tie PV inverter that is able to improve power quality under conditions of both distorted and unbalanced source voltage. The presented strategy is based on the instantaneous power theory and uses a second-order generalized integrator-quadrature signal generator (SOGI-QSG). The presented control strategy is aimed at compensating reactive power, eliminating current harmonics, load balancing, and enabling the PV to inject maximum power to the grid. The advantages of the control system are the use of SOGI-QSG adaptive filter and frequency-locked loop (FLL), and removing the low-pass filter and phase-locked loop (PLL). DC–DC and DC–AC converters are utilized for connecting the PV to the grid. The DC–DC and DC–AC converters are responsible for maximum PV power tracking and achieving the control aims, respectively. Using 4-leg converter structure for grid-tie inverter enables achieving the control objectives in 3-phase 4-wire distribution network without any transformer. The presented control strategy is applied to a 3-phase 4-wire distribution network and is simulated in MATLAB/SIMULINK environment. The results of this simulation are then compared with the conventional instantaneous power method in areas including load balancing, reactive power compensation and the elimination of current harmonics, under unbalanced and distorted source voltage conditions.

A Generalized Design Framework of Notch Filter Based Frequency-Locked Loop for Three-Phase Grid Voltage

Despite many intensive researches regarding frequency-locked loops (FLLs) in recent years, the basic problems of principles, models, and structures of FLL algorithms remained open. Conventional FLL comprises a notch filter and a frequency adaptive loop. The notch filter can be categorized into two types: real coefficient filter (RCF) and complex coefficient filter (CCF). However, the principles, models, and structures of RCF and CCF are generally explained by various theories, and thus, a unified understanding and further developments of FLLs are restricted. This paper proposes a generalized design framework of FLLs based on the Popov adaptive theory. Grounded on the proposed framework, three main contributions can be achieved: 1) the mathematical equivalence of RCF-based FLLs and CCF-based FLLs are revealed; 2) not only the wellknown FLLs (e.g., the DSOGI-FLL and the AVF-FLL) can be derived, but also the other FLLs with novel features can be generated, and thus, the existing case designs of FLLs are developed into a family of designs; 3) the performance differences in terms of stability and convergence speed of the FLLs are quantitatively analyzed, and thereby an enhanced FLL (referred to as EFLL) is recommended. The designs and analyzes have been verified by both simulations and experiments.

A Frequency Demodulator Based on Adaptive Sampling Frequency Phase-Locking Scheme for Large Deviation FM Signals

A frequency demodulation scheme based on adaptive sampling frequency phase-locking loop (PLL) is proposed for extracting large deviation message signal from sinusoidal frequency-modulated signals. The proposed scheme has been designed to track the frequency-modulated input signal using a look-up-table and adaptively changing the sampling period. While tracking the carrier signal, the numerically controlled oscillator involved in the PLL structure produces the sampling frequency according to the variation of input frequency. In the PLL, the message signal has been extracted at the output of proportional integral controller. Simulation results prove that the PLL exhibits quick acquisition behavior, wide operating range, negligible steady-state error. Experimental investigation validates the efficacy of the proposed PLL performance in message signal extraction.

A fully-integrated 16-channel EEG readout front-end for neural recording applications

In this paper, a power-efficient, low noise analog front-end (AFE) is presented which employs the chopper-stabilized technique. A new instrumentation amplifier structure leads to a high input impedance beyond 10 GΩ at the frequency of 10 Hz. Furthermore, an adaptive DC servo loop (DSL) is proposed which is conditionally activated to minimize the negative impact of this block on the noise performance of the AFE. The integrated input-referred noise of the amplifier is 1.33 µVrms and 1.19 µVrms over the 0.5 Hz–100 Hz frequency range when the DSL is enabled or disabled, respectively. Also, considering different aspects of the AFE, a new comprehensive figure of merit (FOM) is introduced to compare different state-of-the-art biopotential amplifiers. The power consumption and bandwidth of the designed 16-channel AFE are 15.81 µW and 235 Hz, respectively. The circuit is realized in the 180 nm standard complementary metal–oxide–semiconductor technology using a 1 V power supply.

Trajectory tracking of quadrotor flying manipulators using [formula omitted] adaptive control

This paper concerns with tracking control of an unmanned quadrotor vehicle equipped with a multi-link robotic manipulator. We present an analytic model of the system that formulates unknown interactions between the aerial platform and the manipulator in the form of nonlinear time-varying uncertainties. Based on the proposed model, a novel trajectory tracking scheme is synthesized by combining two inner feedback linearization loops to stabilize the nominal quadrotor and manipulator dynamics and a master L1 adaptive loop to systematically compensate for uncertainties and realize the desired closed-loop behavior. We show that this scheme leverages predictable transient and steady state performance in the presence of coupling effects and given a specified reference trajectory. Simulation studies have shown the effectiveness of the proposed aerial manipulator control method.

Analysis of Tan-Sun Coordinate Transformation System for Three-Phase Unbalanced Power System

This paper mainly analyzes the characteristics of Tan-Sun coordinate transformation system, which is an extended version of Clarke coordinate transformation system suitable to be applied in three-phase unbalanced power system. The main purpose of Tan-Sun coordinate transformation system is to convert three-phase unbalanced alternating-current quantities into two orthogonal alternating-current quantities with the same amplitude, and these two quantities can be further converted into two direct-current quantities without second harmonic components through Park transformation. Tan-Sun coordinate transformation system can realize the direct-current decoupling of three-phase unbalanced currents, and the strict decoupling of the model of three-phase unbalanced power system, so the control methods developed for three-phase balanced power system can be migrated into three-phase unbalanced power system perfectly. In this paper, Tan-Sun and inverse Tan-Sun coordinate transformation matrices are illustrated at first. The essence of Tan-Sun coordinate transformation system is then presented, which can be divided into two coordinate transformation processes, and the corresponding coordinate transformation matrices are provided by detailed analysis. The relationship between Tan-Sun and Clarke coordinate transformation systems is also discussed. Finally, the simulation and experimental results are provided to validate the effectiveness of the adaptive Tan-Sun phase-locked loop method and the superiority of Tan-Sun coordinate transformation system.

High average power coherent femtosecond pulse combining system based on an all fiber active control method

We experimentally demonstrate a high average power coherent polarization beam combining system of two-channel femtosecond fiber chirped-pulse amplifiers based on our all fiber active control method comprising an active phase locking loop and adaptive control loop of optical path drift for the first time. A coherent combining efficiency of 87% is achieved at the combined power of 4.3 W, which drops with the average power scaling. The combined average power finally reaches 313 W with a coherent combining efficiency of 79% and the corresponding compressed pulse duration is 827 fs. The reasons for the loss in combining efficiency are experimentally investigated. Further power scaling is restricted by the deterioration of the laser mode, but it is still possible if the performance of the single femtosecond fiber chirped-pulse amplifier is improved.

Enhanced proportional power sharing strategy based on adaptive virtual impedance in low‐voltage networked microgrid

The variation of the electrical distance and the complexity of the electric network lead to the variations of feeder impedances between distributed generation units and load points. It is determined that conventional droop control has drawbacks in achieving accurate power sharing due to the effects of mismatched impedance. Therefore, this study proposes an enhanced proportional power sharing strategy based on adaptive virtual impedance in a low-voltage networked microgrid. The improved R-L type droop control can effectively prevent the coupling between real and reactive powers. Furthermore, an adaptive virtual impedance loop is introduced to counteract the feeder voltage drop. The method utilises real and reactive power mismatching which were fed into integral controllers, and then generates the virtual inductive and resistive components, respectively. This proposed strategy is able to enhance power sharing accuracy without requiring the knowledge of feeder impedance, and it is more adaptive to the complex impedance. The simulation experiments carried out under the environment of MATLAB/Simulink, and results verify the effectiveness of the proposed strategy.

A 5 Gb/s CMOS adaptive equalizer for serial link * * Project supported by the National Natural Science Foundation of China (No. 61376099), the Foundation for Fundamental Research of China (No. JSZL2016110B003), and the Major Fundamental Research Program of Shaanxi (No. 2017ZDJC-26).

A 5 Gb/s adaptive equalizer with a new adaptation scheme is presented here by using 0.13 μm CMOS process. The circuit consists of the combination of equalizer amplifier, limiter amplifier and adaptation loop. The adaptive algorithm exploits both the low frequency gain loop and the equalizer loop to minimize the inter-symbol interference (ISI) for a variety of cable characteristics. In addition, an offset cancellation loop is used to alleviate the offset influence of the signal path. The adaptive equalizer core occupies an area of 0.3567 mm2 and consumes a power consumption of 81.7 mW with 1.8 V power supply. Experiment results demonstrate that the equalizer could compensate for a designed cable loss with 0.23 UI peak-to-peak jitter.

Adaptive Gain Control Method of a Phase-Locked Loop for GNSS Carrier Signal Tracking

The global navigation satellite system (GNSS) has been widely used in both military and civil fields. This study focuses on enhancing the carrier tracking ability of the phase-locked loop (PLL) in GNSS receivers for high-dynamic application. The PLL is a very popular and practical approach for tracking the GNSS carrier signal which propagates in the form of electromagnetic wave. However, a PLL with constant coefficient would be suboptimal. Adaptive loop noise bandwidth techniques proposed by previous researches can improve PLL tracking behavior to some extent. This paper presents a novel PLL with an adaptive loop gain control filter (AGCF-PLL) that can provide an alternative. The mathematical model based on second- and third-order PLL was derived. The error characteristics of the AGCF-PLL were also derived and analyzed under different signal conditions, which mainly refers to the different combinations of carrier phase dynamic and signal strength. Based on error characteristic curves, the optimal loop gain control method has been achieved to minimize tracking error. Finally, the completely adaptive loop gain control algorithm was designed. Comparable test results and analysis using the new method, conventional PLL, FLL-assisted PLL, and FAB-LL demonstrate that the AGCF-PLL has stronger adaptability to high target movement dynamic.

Vibratory drilling with digital adaptive control

High standards and efficiency of deep hole drilling used for hard-to-machine metals and alloys could not be achieved if chips are not segmented in the cutting zone. Chip control could be achieved through transmission of harmonic vibrations to the drill in direction of its rotating axis. One way to maintain these vibrations is to replace a drill chuck with a special self-vibratory drilling head, which includes an elastic element that allows axial movement of the tool. The right stiffness value of an elastic element and appropriate machining conditions could lead to oscillation self-excitation of a drill due to the regenerative mechanism. It is advisable to support this mechanism with a control action defined within the feedback loop, which provides process quality necessary for chip control in the broad range of process parameters. This work analyzes adaptive control algorithm for vibratory drilling process dynamics where control action over an oscillating system is proportional to drill axial vibrational velocity, and a feedback gain is determined in the adaptation loop. Dynamics modeling of a closed-loop nonlinear system “elastic system-machining process-control system” is carried out for cases with or without control proving effectiveness of control algorithm. The model was used to analyze how control system analog-to-digital conversion parameters influence vibratory process quality. Requirements, which ensure control system achieves a control aim, were approximately stated for capacity and response limit for analog-to-digital conversion.

Adaptive Control of Thermal Processes: Laser Welding and Additive Manufacturing Paradigms

In Laser-based Manufacturing, the configuration of process parameters aims to maintain quality measures within specific boundaries and it is obtained through experimentation. The idea developed and presented in this paper concerns the prediction of the performance of adaptive control policies, based on process modeling. Two examples of Laser-based Manufacturing are deployed in order to verify the response of adaptive control algorithms through empirical design, Laser welding and Laser-based Additive Manufacturing processes. The penetration depth has been utilized as the quality criterion of the adaptive control loop for both processes. The solidification phase has also been examined.

Adaptive Multi loop IMC Based PID controller tuning using Bat Optimization algorithm for Two Interacting Conical Tank Process

In this paper, multi-loop adaptive internal model controller (IMC)-based PID is designed for the two interacting conical tank level process (TICTLP). The nonlinear TICTLP is decomposed into linear transfer function matrix around the operating points and the effective open loop transfer function (EOTF) is developed using simplified decoupler. The IMC-based PID controller parameters are obtained for EOTF model using bat optimisation algorithm (BOA). A weighted sum of integral time absolute error is used as control design objective function for multi-loop IMC-PID design which yields faster settling time with minimum over shoot. The fuzzy-based adaptive gain scheduling is used to provide complete control to TICTLP and fuzzy-based adaptive decoupler is implemented to eliminate the dynamic interaction between control loops. The simulation results of proposed controller are compared with conventional ZN-PID, IMC controllers to show the superiority of proposed controller. The simulation response of proposed controller indicates the performance improvement control schemes interns of time domain performance indices, servo tracking, regulatory response and faster settling time.

Demonstration of a vectorial optical field generator with adaptive close loop control.

We experimentally demonstrate a vectorial optical field generator (VOF-Gen) with an adaptive close loop control. The close loop control capability is illustrated with the calibration of polarization modulation of the system. To calibrate the polarization ratio modulation, we generate 45° linearly polarized beam and make it propagate through a linear analyzer whose transmission axis is orthogonal to the incident beam. For the retardation calibration, circularly polarized beam is employed and a circular polarization analyzer with the opposite chirality is placed in front of the CCD as the detector. In both cases, the close loop control automatically changes the value of the corresponding calibration parameters in the pre-set ranges to generate the phase patterns applied to the spatial light modulators and records the intensity distribution of the output beam by the CCD camera. The optimized calibration parameters are determined corresponding to the minimum total intensity in each case. Several typical kinds of vectorial optical beams are created with and without the obtained calibration parameters, and the full Stokes parameter measurements are carried out to quantitatively analyze the polarization distribution of the generated beams. The comparisons among these results clearly show that the obtained calibration parameters could remarkably improve the accuracy of the polarization modulation of the VOF-Gen, especially for generating elliptically polarized beam with large ellipticity, indicating the significance of the presented close loop in enhancing the performance of the VOF-Gen.

A +25-dBm IIP3 1.7–2.1-GHz FDD Receiver Front End With Integrated Hybrid Transformer in 28-nm CMOS

A highly linear receiver (RX) front end with integrated hybrid transformer (HT) for frequency-division duplexing mobile communications is reported. The HT, implemented with a three-winding coplanar transformer, is used to interface the RX front end with the antenna and the power amplifier. The primary is driven at its center tap with the transmitted signal and at one input with the antenna signal, while the other input is connected to an on-chip programmable balancing impedance. The two secondary drives a differential push–pull common-gate low-noise amplifier (LNA). Assuming a perfectly linear hybrid only 45 dB of transmitter (TX)–RX isolation and 35 dB of common-mode rejection are required to meet the intermodulation specs thanks to the +25-dBm receiver IIP3. This would drastically simplify hybrid balancing and adaptation loop. Cascaded noise figure of duplexer, LNA, and baseband is below 6.7 dB and TX insertion loss below 4.3 dB from 1.7 to 2.1 GHz. The implemented prototype in 28-nm CMOS has an active area of 0.7 mm2 and requires only 26 mW.

An Adaptive PAM-4 Analog Equalizer With Boosting-State Detection in the Time Domain

This paper introduces an improved adaptive analog equalizer that is required in high speed serial receivers using four-level pulse amplitude modulation signaling. By performing boosting-state detection in the time domain, the proposed adaptive analog equalizer can effectively overcome a serious problem that the received signal’s eye-opening tends to be compromised by the convergence accuracy of the adaptive control loop. To suppress the pattern-dependent jitters (PDJs), an inductor-less, cross-stage feedback structure is employed in the proposed analog equalizer to help broaden its effective tuning bandwidth. Multichannel simulations have confirmed that the proposed equalizer is able to achieve a 42% improvement in eye-height opening when compared with the equalizers employing popular spectrum-comparing schemes. Trellis diagram analyses under different date rates have revealed that the bandwidth of the proposed equalizer can be extended by as much as 60%, thus effectively bringing the PDJs from 44% down to 27.5%.