Closed-loop Gain Research Articles

A Wideband Oscillator Exploiting Multiple Resonances in Lithium Niobate MEMS Resonator.

This article presents a comprehensive guide to codesign lithium niobate (LiNbO3) lateral overtone bulk acoustic resonators (LOBARs) and voltage-controlled oscillators (VCOs) using discrete components on a printed circuit board (PCB). The analysis focuses on understanding the oscillator-level tradeoffs between the number of locked tones, frequency stability, tuning range, power consumption, and phase noise. Moreover, this article focuses on understanding the relationship between the abovementioned specifications and the different LOBAR parameters, such as electromechanical coupling ( kt2 ), quality factor ( Q ), transducer design, and the resonator size. As a result of this study, the first voltage-controlled MEMS oscillator (VCMO) based on LiNbO3 LOBAR is demonstrated. Our LOBAR excites over 30 resonant modes in the range of 100-800 MHz with a frequency spacing of 20 MHz. The VCMO consists of an LOBAR in a closed loop with two amplification stages and a varactor-embedded tunable LC tank. By adjusting the bias voltage applied to the varactor, the tank can be tuned to change the closed-loop gain and phase responses of the oscillator so that the Barkhausen conditions are satisfied for a particular resonant mode. The tank is designed to allow the proposed VCMO to lock to any of the ten overtones ranging from 300 to 500 MHz. These ten tones are characterized by average [Formula: see text] of 2100, kt2 of 1.5%, figure of merit ( [Formula: see text]) of 31.5 enabling low phase noise, and low-power oscillators crucial for Internet of Things (IoT). Due to the high [Formula: see text] of the LiNbO3 LOBAR, the measured VCMO shows a close-in phase noise of -100 dBc/Hz at 1-kHz offset from a 300-MHz carrier and a noise floor of -153 dBc/Hz while consuming 9 mW. With further optimization, this VCMO can lead to direct radio frequency (RF) synthesis for ultralow-power transceivers in multimode IoT nodes.

Concise and economical control implemented on ship fin stabilizer system based on nonlinear feedback algorithm

For damping the rolling motion of ship effectively and economically in rough sea, nonlinear feedback algorithm is implemented to control the fin stabilizer. Most of the researches paid attention to improve the performance of controller, while this paper turns attention to control the feedback error by a nonlinear function to reduce energy consumption. The controller and feedback error decorating constitutes to a kind of nonlinear feedback control. In rough sea, the controller which is designed by close-loop gain shaping algorithm can reduce the rolling angle by 51.67%. After decorating feedback error by a sine nonlinear function, the performance of controller is not affected, while the output of fin servo system is decreased by 13.6%. Obviously, the energy is saved.

A Phase Noise Reduction Technique in LC Cross-coupled Oscillators with Adjusting Transistors Operating Regions

In this paper, an intuitive analysis of a phase noise reduction technique is done, and then a modified structure is proposed to achieve higher phase noise reduction than the original one. This method reduces the impact of noise sources on the phase noise by decreasing closed-loop gain in zero-crossings points and moving this high closed-loop gain to the non-zero-crossings points. This reduction tested on different scales and all of them showed improvement in the phase noise performance. In other words, this method reduces the phase noise by manipulating the operation region. Impulse sensitivity function (ISF) for the proposed structure shows degradation in comparison to the original structure. We have designed the proposed oscillator in 0.18 μm using CMOS TSMC standard technology. The proposed oscillator operates on 900 MHz, moreover, phase noise is -138.4 dBc/Hz at 1 MHz offset frequency while it consumes 3.11 mA from 1.8 V supply voltage. Keywords. LC cross-coupled oscillator. Phase noise reduction. ISF reduction.

Multitechnique Concise Robust Control for the Insulation Containment Space Pressure Control of LNG Carrier

In this note, a novel multitechnique concise robust control scheme, based on the mirror mapping technique (MMT), closed-loop gain shaping algorithm (CGSA), Smith predictor (SP), and nonlinear feedback technique (NFT), is proposed for the pressure control of the liquefied natural gas (LNG) carrier insulation containment space. Firstly, a kind of integral unstable time-delay model is obtained by linearizing the nonlinear model of the pressure maintenance system around its equilibrium. By using the MMT and CGSA, one acquires the corresponding stable mirror mapping model of the unstable linear model and the designed controller. And the SP is introduced to tackle the time-delay problem. In addition, for the purpose of energy saving, the NFT is added into the control scheme. Finally, a set of experiments has been employed to illustrate the control effects, and the results show that it can achieve satisfying performance in aspects of disturbance rejection and energy saving.

Measurement delay compensated LADRC based current controller design for PMSM drives with a simple parameter tuning method

For permanent magnet synchronous motor drives, the difficulty of parameter tuning of nonlinear active disturbance rejection control (ADRC) current controller is the bottleneck for its application. This paper proposes a measurement delay compensated linear ADRC (LADRC), and a simple tuning method for LADRC’s parameters is presented. Firstly, an ideal model without resistance is acquired, because the current coupling terms, dead-time effects, and motor parameter variations are estimated and canceled out by an linear extended state observer. Secondly, an improved LADRC considering time delay of current measurement is developed. It eliminates unmatched disturbance compensation caused by measurement delay. And frequency responses of current closed-loop gain and disturbance suppression are evaluated. Then, based upon the frequency characteristics of the LADRC controller, a simple tuning method founded on desired frequency bandwidth is presented. It is convenient to be implemented. Finally, experimental results demonstrate that the proposed method is effective.

Two-Stage BJT Amplifier with Negative Voltage Series Feedback Analysis Program Proteus 8

In this paper, the common two-stage amplifier voltage series negative feedback amplifier circuit is analyzed theoretically. With negative feedback, the closed-loop voltage gain can be reduced and controlled so that the op-amp can function as a linear amplifier. Negative feedback is the basic method and essential means of improving amplifying circuit efficiency. Then using Proteus 8 professional as simulation software, the relationship between the gain obtained by open-loop and the simulation of the closed-loop and the pass-band is shown by comparing the real experimental data with the result of the circuit’s simulation and the waveform. Negative feedback opposes or subtracts from the input signals giving it many advantages in the design and stabilization of control systems. Basically the relationship consistent with the calculated results, that is in good agreement with the theoretical analysis.

Improving Rate of Convergence via Gain Adaptation in Multi-Agent Distributed ADMM Framework

In this paper, the Alternating Direction Method of Multipliers (ADMM) is investigated for distributed optimization problems in a networked multi-agent system. In particular, a new adaptive-gain ADMM algorithm is derived in a closed form and under the standard convex property in order to greatly speed up convergence of ADMM-based distributed optimization. Using Lyapunov direct approach, the proposed solution embeds control gains into weighted network matrix among the agents and uses those weights as adaptive penalty gains in the augmented Lagrangian. It is shown that the proposed closed loop gain adaptation scheme significantly improves the convergence time of underlying ADMM optimization. Convergence analysis is provided and simulation results are included to demonstrate the effectiveness of the proposed scheme.

Energy Saving of Course Keeping for Ships Using CGSA and Nonlinear Decoration

In order to further reduce the rudder angle and the steering frequency on the premise of achieving good course-keeping control effect for ships, a concise robust control algorithm is proposed in this paper. The second order closed-loop gain shaping algorithm is employed to design the linear controller first. Then the final control law is achieved by using the nonlinear decoration technique. The stability of the closed-loop system is proved by the Nyquist criterion. Taking training vessel Yukun as a test plant, the simulation experiments under normal sea state and heavy sea state are carried out respectively to verify the effectiveness of the proposed scheme. The results indicate that compared with the existing methods, the proposed control algorithm not only has obvious advantages in energy-saving effect and smoothness, but also has stronger anti-interference ability under heavy sea state. The second-order closed-loop gain shaping controller decorated by bipolar sigmoid function has better robustness and a concise form. Meanwhile its remarkable energy-saving effect and smoothness make steering condition meet the requirements of navigation practice, which is of great significance for ships to realize safe and efficient navigation.

A kind of multimode nonlinear algorithm for efficiency-improved course keeping of large tankers

In order to achieve efficient control of ship course keeping with low energy consumption, this paper introduces nonlinear feedback into fuzzy control and closed-loop gain shaping algorithm (CGSA). Taking the ship “New Triumph” as an example, the simulation results show that the multimode controller with non-linear feedback can not only respond to the steering instructions quickly, but also reduce the energy consumption by 32% to realize the course keeping efficiently and smoothly under the wind-wave model. Research shows that the introduction of nonlinear feedback term can optimize the control system, and its advantages of saving energy consumption are of great significance in practical engineering applications.

Enhanced Gradient Tracking Algorithms for Distributed Quadratic Optimization via Sparse Gain Design

In this paper we propose a new control-oriented design technique to enhance the algorithmic performance of the distributed gradient tracking algorithm. We focus on a scenario in which agents in a network aim to cooperatively minimize the sum of convex, quadratic cost functions depending on a common decision variable. By leveraging a recent system-theoretical reinterpretation of the considered algorithmic framework as a closed-loop linear dynamical system, the proposed approach generalizes the diagonal gain structure associated to the existing gradient tracking algorithms. Specifically, we look for closed-loop gain matrices that satisfy the sparsity constraints imposed by the network topology, without however being necessarily diagonal, as in existing gradient tracking schemes. We propose a novel procedure to compute stabilizing sparse gain matrices by solving a set of nonlinear matrix inequalities, based on the solution of a sequence of approximate linear versions of such inequalities. Numerical simulations are presented showing the enhanced performance of the proposed design compared to existing gradient tracking algorithms.

An ultra-low power amplifier for wearable and implantable electronic devices

This paper presents an ultra-low-power CMOS amplifier for Low-frequency biosignal recording applications, especially for implantable biosensors and wearable or portable devices such as wearable electrocardiogram (ECG) recording microsystems that power consumption and on-chip area are the critical constraints. The proposed amplifier consists of two stages. In the first stage, a current reuse topology is used to achieve a lower input-referred voltage noise power density compared to a normal single-ended common source amplifier. In order to reduce the on-chip area, an inverter based amplifier with high output impedance is used at the output stage of the circuit to reduce the area occupied by the large load capacitance, which is required for having low cut off frequency of 200 Hz. Using this technique, the required load capacitance is decreased to about 2.1 pF. To reduce the power consumption, a ± 0.6 V supply voltage is used, and the transistors are pushed toward sub-threshold region to reduce the bias currents to about 260 nA in the first and the second stages. To validate the design, the proposed amplifier is simulated using 0.18 μm TSMC CMOS technology with Cadence in post-layout level. It is shown that the total power consumption of the proposed amplifier is as low as 640 nW. The proposed amplifier benefits from a CMRR >125 dB, total input-referred noise of 6.1 μVrms in 200 Hz bandwidth for ECG signal recording, and a closed-loop gain of about 35.1 dB. The layout of the circuit occupies a total area of 0.034 mm2.

A Low Noise Amplifier Suitable for Biomedical Recording Analog Front-End in 65nm CMOS Technology

This paper presents a fully integrated front-end, low noise amplifier (LNA), dedicated to the processing of various types of bio-medical signals, such as Electrocardiogram (ECG), Electroencephalography (EEG), Axon Action Potential (AAP). A novel noise reduction technique, for an operational transconductance amplifier (OTA), has been proposed. This adds a current steering branch parallel to the differential pair, with a view to reducing the noise contribution by the cascode current sources. Hence, this reduces the overall input-referred noise of the LNA, without adding any additional power. The proposed technique implemented in 65[Formula: see text]nm CMOS technology achieves 30 dB closed-loop voltage gain, 0.05[Formula: see text]Hz lower cut-off frequency and 100 MHz 3-dB bandwidth. It operates at 1.2[Formula: see text]V power supply and draws 1[Formula: see text][Formula: see text]A static current. The prototype described in this paper occupies 3300[Formula: see text][Formula: see text]m2 silicon area.

Power applications for fuel-cell using switching regulators

<p><strong> </strong></p>Generally the switch mode power supply input voltage source is constant or shows insignificant little varieties.in any case, when fuel call used input source the last assumption is not valid. A fuel cell stack is give a details of low and not controlled DC output voltage, moreover, when the demanded current increases the output voltage becomes low in a nonlinear form; from now on, suitable controller is required to taken the previously mentioned issues. In this article, a normal current-mode controller is planned to using a joined model for an energy unit stack and a boost converter; besides, the resolving control method increasing the system stability and output voltage regulation.. The proposed energy system utilizes an energy component power (polymer electrolyte film fuel cell) and a boost converter passing on power of 900 W. the proposed controller execution for output voltage regulation by means of closed loop gain estimations and step load changes. What's more, a correlation amongst open-and closed- loop estimations is made, where the controller robustness is tried for vast load varieties and fuel cell stack output voltage changes are shows on simulation results.

A Battery-Less Portable ECG Monitoring System With Wired Audio Transmission.

This paper proposes a batteryless electrocardiogram (ECG) monitoring chip and intelligent system with wired audio transmission, which can be applied to long-term and real-time ECG monitoring. The ECG signal is modulated and amplified in the front-end chip and then is transmitted through the microphone channel of the 3.5-mm headphone cable. The sinusoidal signals from the left and right channels are converted into a dc supply and a precise local oscillator signal in the front-end chip, respectively. The proposed system samples the signal through the high-precision audio analog-to-digital converter in smart devices and processes it through the internal software. Therefore, no external battery, local oscillator, and complicate modules are required in this system. A chopper/amplitude modulation (AM) reused mixer amplifier is proposed, which combines chopping with AM and reuses the local oscillator signal. The closed-loop gain of the proposed amplifier varies between 20 and 47 dB and can be automatically adjusted according to the amplitude of the output signal. The proposed chip was implemented in a standard 0.18-μm CMOS process and occupies 1.07 × 0.95 mm2 of core area. The power management module outputs a 1.5-V dc voltage to power the system. When connected with the headphone cable load, the chip consumes a total power of 156 μW. The proposed monitoring system has been verified by the audio device and MATLAB in the PC. The test results show that the input reference noise of the demodulated signal is 2.12 μVrms (0.1-200Hz) and the total harmonic distortion is 0.56%@3 mV input.

Controller Design for MIMO System with Time Delay Using Closed-loop Gain Shaping Algorithm

In this paper, a general scheme is proposed for Multi Input Multi Output (MIMO) systems with time delays by using closed-loop gain shaping algorithm (CGSA). The controller is designed based on the minimum phase(MP) part of these processes. For every closed loop, there is the unique variable parameter, the performance and robustness can be tuned quantitatively to satisfy the practical requirements of project. Finally, three examples in published literatures are performed to illustrate the effectiveness of proposed method. Compared with the relative references, the control performances of proposed method are superior to those of existed research, and the control scheme is with advantages of concision and efficiency.

Closed-Loop Cardiovascular Interactions and the Baroreflex Cardiac Arm: Modulations Over the 24 h and the Effect of Hypertension

Closed-loop models of the interactions between blood pressure (BP) and heart rate variations allow for estimation of baroreflex sensitivity (feedback effects of BP changes on heart rate) while also considering the feedforward effects of heart rate on BP. Our study is aimed at comparing modulations of feedback and feedforward couplings over 24 h in normotensive and hypertensive subjects, by assessing closed-loop baroreflex models in ambulatory conditions. Continuous intra-arterial BP recordings were performed for 24 h in eight normotensive and eight hypertensive subjects. Systolic BP (SBP) and pulse interval (PI) beat-by-beat series were analyzed by an autoregressive moving average model over consecutive 6-min running windows, estimating closed-loop feedback and feedforward gains in each window. The open-loop feedback gain was estimated for comparison. Normotensive and hypertensive patients were compared during wake (18:00–22:00) and sleep (23:00–5:00) periods by a mixed-effect linear model at p < 0.05. In both groups feedback (feedforward) gain averaged values were higher (lower) in sleep than in wake. Moreover, the closed-loop feedback gain was higher in normotensive subjects both in wake and sleep, whereas the closed-loop feedforward gain was higher in hypertensive subjects during sleep. By contrast, no significant differences were found between the normotensive and hypertensive groups for the open-loop feedback gain. Therefore, the closed-loop SBP-PI model can detect circadian alterations in the feedforward gain of PI on SBP and derangements of spontaneous baroreflex sensitivity in hypertension not detectable with the open-loop approach. These findings may help to obtain a more comprehensive assessment of the autonomic dysfunction underlying hypertension and for the in-depth evaluation of the benefits of rehabilitation procedures on autonomic cardiovascular modulation.

Robust MPC with recursive model update

Robust constrained control of linear systems with parametric uncertainty and additive disturbance is addressed. The main contribution is the introduction of a mathematically rigorous and computationally tractable framework for stabilizing model predictive control with online parameter estimation to improve performance and reduce conservatism. Requirements for closed-loop stability and provable constraint satisfaction are considered separately, resulting in the use of online set-membership system identification combined with homothetic prediction tubes for robust constraint satisfaction, and an H∞ optimal point estimate of the unknown parameters to achieve a finite closed-loop gain from the disturbance to the state. Extensions to time-varying parameters and persistently exciting inputs to guarantee parameter convergence are presented. A numerical example illustrates the proven properties and efficacy of the approach.

Design of Two-Stage Fully-Differential Operational Transconductance Amplifier Using a Standard 0.35µm CMOS Process

The paper presents a design of a two-stage fully-differential operational transconductance amplifier (OTA) for a 10-bit 40-Msamples/s Nyquist rate analog-to-digital converter (ADC) using  a standard 0.35µm complementary metal-oxide semiconductor (CMOS) process. A telescopic cascode topology is implemented as main stage, with common source amplifiers as output stage for the differential outputs. The open loop amplifier achieved a gain of 108dB, while the closed loop gain is at 12dB with settling time of less than 11ns for an accuracy of 0.5%. Total output noise achieved is 63.4uVrms. Loop unity gain bandwidth is 205MHz with phase margin of 77.6°. The design has a dynamic range of 88.3dB, and power consumption of 26.6mW from a 3V supply.

Integrated control and process design for improved load changes in fluidized bed boiler steam path

Integrated control and process design is considered for a power plant to obtain improved load changes in output electrical power (MWe). Fast load transitions are increasingly needed in conventional power plants, which calls for a deeper integration between the boiler and its control system. An integrated design methodology is applied to an industrial boiler steam path in this paper; no past reports of such an application exist in the literature. The methodology utilizes dynamic optimization together with performance relative gain array and closed-loop disturbance gain controllability analysis. The aim is to optimize the boiler steam storage distribution, the turbine valve operation, and the electrical power and main steam pressure controllers during different MWe ramp reference trajectories. The methodology was successful in defining closed-loop designs with excellent MWe setpoint tracking, small steam pressure disturbances and minimal steam throttling. The results also highlighted the challenges related to integrated design in power plants.

The Performance of Operational Amplifiers Consisting of 4H-SiC CMOS After Gamma Irradiation

The operational amplifier was fabricated by 4H-SiC complementary MOS on the same die for sensors installed in nuclear power plants, and it showed over $100\times $ the radiation resistance compared with Si bipolar junction transistors. The closed-loop gain at 50 kGy was 11% lower than it of preirradiation because the allowable output voltage range became small by the threshold voltage degradation of p-channel metal–oxide–semiconductor field-effect transistors (MOSFETs), and the offset voltage became unstable when the gamma integral dose was beyond 30 kGy. To reduce the influence of gamma irradiation, we propose a MOSFETs structure which features both thin gate oxide and field plate electrodes connected to an isolation layer. We evaluated the proposed isolation structure using the single device, and our experiments confirmed that the proposed isolation structure has potential of gamma irradiation resistance of 100 kGy.