Simple Compensation Research Articles

A temperature-dependent gain compensation technique for positron emission tomography detectors based on a silicon photomultiplier

In this study, we propose a simple gain compensation technique for silicon photomultiplier (SiPM)-based positron emission tomography detectors, using a temperature sensor that automatically controls the bias voltage of the SiPM depending upon the ambient temperature. The temperature sensor output, for which the temperature coefficient can be controlled by the input voltage, is used as one end of the bias voltage. By adjusting the temperature coefficient, the proposed gain compensation method can be applied to various SiPMs with different breakdown voltages. As a proof of concept, the proposed method was evaluated for two scintillation detector setups. Applying the proposed method to a single-channel SiPM (ASD-NUV3S-P; AdvanSiD, Italy) coupled with a 3 mm × 3 mm × 20 mm LGSO crystal, the 511 keV photopeak position in the energy histogram changed by only 1.52% per 10 °C while, without gain compensation, it changed by 13.27% per 10 °C between 10 °C and 30 °C. On a 4 × 4 array MPPC (S14161-3050HS-04; Hamamatsu, Japan), coupled with a 3.12 mm × 3.12 mm × 15 mm 4 × 4 LSO array, the photopeak changes with and without gain compensation were 2.34% and 20.53% per 10 °C between 10 °C and 30 °C, respectively. On the wider range of temperature, between 0 °C and 40 °C, the photopeak changes with and without gain compensation were 3.09% and 20.89%, respectively. The energy resolution degradation of SiPM-based scintillation detectors operating at temperatures was negligible when the proposed gain compensation method was applied.

100 Gbps/λ C-Band CD Digital Pre-Compensated and Direct-Detection Links With Simple Non-Linear Compensation

In the scenario of downstream Passive Optical Networks (PON), we analyze through simulations and experiments a 100 Gbps/λ link using digital signal processing (DSP) over up to 50 km single mode fiber (SMF) in C-band. In particular, we propose chromatic dispersion digital pre-compensation (CD-DPC) and quaternary pulse amplitude modulation (PAM-4) levels optimization at the transmitter side (TX), and simple non-linear compensation (NLC) in combination with adaptive equalization (AEQ) at the receiver side (RX). Regarding NLC, we compare two approaches: a quadratic polynomial function and a square-root-like function respectively. In this paper, we analyze in detail the performances of four proposed options, namely equispaced PAM-4 levels without NLC (baseline case), equispaced PAM-4 levels in combination with NLC, optimized PAM-4 levels without NLC, and optimized PAM-4 levels in combination with NLC. We demonstrate through simulations and experiments that optimized PAM-4 levels can only offer limited enhancement when NLC is applied, and up to 3.3 dB sensitivity gain can be obtained thanks to NLC at RX when setting the optimum parameters, with respect to the baseline case.

Motion control of the rail traction system by dual brushless AC motors using a disturbance observer

This study presents an accurate motion control scheme using a modified non-linear disturbance torque observer for a rail traction system driven by a dual brushless AC (BLAC) motor. The target application has two BLAC motors mounted on the top surface of the rail. The mover translation along the rail is handled solely by the traction motors without any external sensor. In the low-speed range, however, the conventional disturbance torque observer is unstable due to the resolution of the Hall sensor and speed detection delay. To solve this instability problem, a simple weight function with the synchronisation of torque current and the delayed speed feedback is added to the proposed torque observer. This way, zero output can be created in the selected speed region for stabilisation and torque current can be compensated. Furthermore, simple balance error compensation to synchronise both motors is added to the proposed speed and position model reference adaptive control scheme. The experiments were performed to verify the proposed control method. The results show advanced performance with reduced position and balance errors between the two BLAC motors and an improved overall control performance of the rail mover.

Wideband Generalized Beamspace Modulation (wGBM) for mmWave Massive MIMO Over Doubly-Selective Channels

Generalized beam modulation (GBM) is a recently proposed spectrum efficiency (SE)-enhanced index modulation (IM) scheme for narrowband millimeter wave (mmWave) massive multiple-input multiple-output (mMIMO) systems with hybrid transceivers. Unlike most existing fully-digital IM techniques whose application to wideband channels is straightforward after adopting the orthogonal frequency division multiplexing (OFDM) technique, extending GBM from the narrowband to wideband channels is quite challenging. The reason is that the per-subcarrier process in hybrid OFDM systems is no longer independent across individuals as all subcarriers share a common analog beamformer. Hence, the designed wideband GBM (wGBM) has to be compatible with hybrid OFDM systems while maintaining the SE-enhanced merit of GBM. Towards this objective, a symbol-based instead of the prevalent subcarrier-based paradigm is applied to guide wGBM design. To avoid the high detection complexity in large-scale OFDM systems, we devise a low-complexity detector by transforming the complicated symbol (block) detection into the manageable subcarrier (sub-block) detection. Finally, a simple first-order Doppler compensator is carefully designed to enhance the robustness of wGBM against Doppler. Both theoretical analyses and numerical simulations have been carried out to demonstrate the superiority of wGBM over existing alternatives in terms of error performance and energy efficiency.

High-Speed CMOS Three-Stage Amplifier Based on Feedback Attenuation

This paper presents a new and simple frequency compensation scheme for multistage CMOS operational transconductance amplifiers (OTAs). In this work, by applying a differential block frequency compensation (DBFC) technique to a compensation network of three-stage OTA, the dominant pole is drastically improved independent from the DC gain path. The DBFC introduces amplified signal directly to the second-stage output through the compensation capacitor. The signal injection increases operational frequency range while just a single and small value capacitor is used as the Miller capacitor, which leads to considering the proposed configuration as a low die area occupation and high-speed amplifier. The simulation results show with the same capacitive load and power dissipation the gain bandwidth (GBW) frequency can be improved considerably compared to conventional nested Miller compensation. The presented circuit is simulated in a 0.18[Formula: see text][Formula: see text]m CMOS technology with a 1.8[Formula: see text]V supply voltage. According to the results, the proposed circuit shows 102[Formula: see text]dB, 105[Formula: see text]MHz, and 343[Formula: see text][Formula: see text]W as the DC gain, GBW, and power consumption, respectively.

Facile and Low Cost Temperature Compensated Humidity Sensor and Signal Conditioning System

Most relative humidity sensors are resistive or capacitive sensors. It’s a fact that the resistance and capacitance of a vast majority of such sensors also depend on the surrounding temperature and a change of temperature can cause significant errors in the final reading of relative humidity. This fact of temperature dependence is scarcely investigated in development of humidity sensors. In this work, a very simple temperature compensation method has been developed that automatically eliminates the effect of change in temperature from the final output without requiring separate measurement of temperature or any data processing. Amorphous polyethylene oxide (PEO) was used as the active material for humidity sensor owing to its high sensitivity and almost linear response. Interdigitated type sensor electrodes (IDE) were fabricated using reverse offset printing on glass substrate and the active layer was deposited through spin coating. An identical twin sensor was fabricated with the same parameters and was additionally encapsulated form the open environment. The dummy sensor was used as opposing pair with the active sensor in a bridge configuration to achieve temperature compensation. The bridge sensitivity was recorded to be ~2.9 mV/%RH that was further improved to 100 mV/%RH using a differential instrumentation amplifier based signal conditioning circuit. The sensor system was deployed in a real-life relative humidity measurement with changing temperature that returned a remarkable accuracy of 98.76%. The error due to temperature dependence reduced from 22.4% to just 1.24%. The transient response time of the sensor was found to be ~2.4 s.

Nonlinear signal errors in homodyne laser Doppler vibrometry induced by strong second-order ghost reflections and their mitigation.

A variety of mechanisms can induce distortions in the output signals of a homodyne laser Doppler vibrometer (LDV). In this paper, the nonlinear LDV distortions caused by a strong second-order ghost reflection originating from lens flares are theoretically explained and analyzed. We propose a simple compensation method to mitigate this distortion. The performance and limitations of this method are also explained both in simulation and in experiment.

A Novel NLOS Error Compensation Method Based IMU for UWB Indoor Positioning System

Electromagnetic wave is susceptible to the multipath effect, especially in complex indoor environment. As transmission of non-line of sight (NLOS), it leads to bigger measurement error, which makes positioning accuracy decline. In the paper, we aim to compensate the measurement error mainly affected by the NLOS to enhance the positioning accuracy. Conceptions of “virtual inertial point” and “environmental factor” are introduced, and moreover acceleration data of inertial measurement unit (IMU) are adopted. A novel and simple NLOS error compensation method for high accuracy indoor positioning system based UWB is proposed. Based on the principle of inertia, IMU can be used to fix motion trend of tag and to get coordinate of virtual inertial point. The measurement coordinate can be acquired by UWB system. We can calculate the distances between virtual inertial point and real measurement in same area, respectively under line of sight (LOS) and NLOS in advance. The ratio of two different distances can be defined as environmental factor, which is mainly used to reflect the influence of NLOS on positioning accuracy quantitatively relative to LOS in the paper. Environmental factor, as the weighted coefficient, is adopted to merge coordinates of the virtual inertial point and measurement to obtain the coordinate compensated under NLOS. It is a process of scaling measurement down to user-defined area for positioning accuracy requirement to reduce the impact of NLOS. At last, Kalman Filter is used to smooth the set of coordinate compensated under NLOS to further improve positioning accuracy. Experimental results show that our method can effectively compensate the NLOS error in the indoor positioning system based ultra-wide band (UWB) technology. The positioning accuracy is improved nearby 80% in NLOS area.

Dynamic Compensation of Ultra-Low-Range Pressure Sensors

A technique has been developed to compensate pressure readings from arrays of highly sensitive membrane-type pressure sensors for deflections caused by acceleration normal to the plane of the membrane using a single inertial measurement unit. By normalizing the fourth-order unsteady Kirchoff-Love equation, it can be shown that inertial body pseudoforces and applied surface pressure elicit a similar and additive response from the sensors. Inertial effects arising from linear and angular acceleration as well as angular velocity may therefore be converted to ‘pseudopressures’ and eliminated by means of a simple linear compensation process which can be calibrated using only gravity. To demonstrate, signals from a conventional six-axis inertial measurement unit (including three orthogonal components each of angular velocity and linear acceleration) are used to provide an approximation of the acceleration of the sensing dies within a seven-channel distributed array of ultra-low pressure sensors. Applying the proposed correction reduces the maximum full-scale uncertainty of the measurements by as much as 50%.

Capacitor Current Feedback With Phase-Lead Compensator to Eliminate Resonant Frequency Forbidden Region for LCL-Type Grid-Connected Inverter in Weak Grid

Digital-controlled <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LCL</i> -type grid-connected inverter, with capacitor-current-feedback active damping, is widely adopted in the mediate-to-high power application because of low output harmonics and high power quality. Owing to the digital control delay, however, the inverter robustness might be weakened against the grid-impedance variation. In this article, a simple phase-lead compensator is proposed to insert into the capacitor-current feedback-path for compensating the digital control delay. In doing so, the boundary frequency of the virtual-positive-resistance-region (VPRR) can be increased from one-sixth to almost one-fourth of the sampling frequency. In addition, the resonant frequency forbidden region for the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LCL</i> filter can be eliminated, such that the inverter robustness can be significantly improved against the grid-impedance variation. To ensure the system stability and attain a good control performance, a design procedure is further presented for the phase-lead compensator as well as the closed-loop parameters. Finally, an <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LCL</i> -type grid-connected inverter is built and tested in the lab, and experimental results are presented to verify the effectiveness of the proposed control scheme and parameter design procedure.

Sparse and Decoupling Control Strategies Based on Takagi-Sugeno Fuzzy Models.

In order to better handle the coupling effects when controlling multiple-input multiple-output (MIMO) systems, taking the decentralized control structure as the basis, this paper proposes a sparse control strategy and a decoupling control strategy. Type-1 and type-2 Takagi-Sugeno (T-S) fuzzy models are used to describe the MIMO system, and the relative normalized gain array-based criterion is employed to measure the coupling effects. The main contributions include: 1) compared to the previous studies, a manner with less computational cost to build fuzzy models for the MIMO systems is provided, and a more accurate method to construct the so-called effective T-S fuzzy model (ETSM) to express the coupling effects is developed; 2) for the sparse control strategy, four indexes are defined in order to extend a decentralized control structure to a sparse one. Afterward, an ETSM-based method is presented that a sparse control system can be realized by designing multiple independent single-input single-output (SISO) control loops; and 3) for the decoupling control strategy, a novel and simple ETSM-based decoupling compensator is developed that can effectively compensate for both steady and dynamic coupling effects. As a result, the MIMO controller design can be transformed to multiple noninteracting SISO controller designs. Both of the sparse and decoupling strategies allow to use linear SISO control algorithms to regulate a closely coupled nonlinear MIMO system without knowing its exact mathematical functions. Two examples are used to show the effectiveness of the proposed strategies.

Temperature Hysteresis Mechanism and Compensation of Quartz Flexible Accelerometer in Aerial Inertial Navigation System.

Strap-down inertial navigation systems (INSs) with quartz flexible accelerometers (QFAs) are widely used in many conditions, particularly in aerial vehicles. Temperature is one of the significant issues impacting the performance of INS. The variation and the gradient of temperature are complex under aerial conditions, which severely degrades the navigation performance of INS. Previous work has indicated that parts of navigation errors could be restrained by simple temperature compensation of QFA. However, the temperature hysteresis of the accelerometer is seldom considered in INS. In this paper, the temperature hysteresis mechanism of QFA and the compensation method would be analyzed. Based on the fundamental model, a comprehensive temperature hysteresis model is proposed and the parameters in this model were derived through a temperature cycling test. Furthermore, the comparative experiments in the laboratory were executed to refine the temperature hysteresis model and to verify the effectiveness of the new compensation method. Applying the temperature hysteresis compensation in flight condition, the result shows that the position error (CEP) is restrained from 1.54 nmile/h to 1.29 nmile/h. The proposed temperature hysteresis compensation method improves the performance of INS effectively and feasibly, which could be promoted to other applications of INS in similar temperature changing environment correspondingly.

Design of Two-Stage Comb-Based Decimation Filter with High Aliasing Rejection and Low Passband Droop

This paper presents a simple method for the design of comb-based decimation filter with a high aliasing rejection and low passband droop. The method is based on the application of the mathematical result on zeros of symmetric polynomials on the unit circle. The application of this result leads to the introduction of the four additional single zeros into comb folding bands, where aliasing occur. As a result, the folding bands become wider and the aliasing rejection is increased. The passband droop is compensated by a simple compensator who works at low rate. The comparisons with the most recent methods from literature confirmed the advantages of this proposal regarding magnitude responses and the required complexity.

How COVID-19 reshapes businesses and executive pay for sustainability

The purpose of this paper is to answer the research question of how to design a fair and resilient compensation scheme according to stakeholder theory and the sustainability concept. The first finding of this paper is the framework for the sustainable, fair, resilient, scientific, simple, and practical compensation schemes — pay for sustainability (P4S). P4S has been developed after reviewing the literature and obtaining insights from the compensation consultants in Switzerland. It is also a useful tool in COVID-19 and will be for future crises. As a second finding, this theory-adaptation-based conceptual and commentary paper criticizes the conventional executive compensation structure and introduces the business lessons learned from the COVID-19 crisis. As a contribution to both the literature and practice, this research advances the novel knowledge in the field by conceptualizing a reliable and scientific framework and explaining the advantages and disadvantages of the four methods of the P4S framework. During COVID-19, environmental, social, and governance (ESG) based performances and compensation schemes have gained more importance. Finally, these proposed methods contribute to the adaptation of ESG-based compensation schemes while considering the local and individual differences of organizations

A Novel Robust Sensorless Technique for Field-Oriented Control Drive of Permanent Magnet Synchronous Motor

This paper proposes a novel rotor position estimation technique based on stator flux linkage to implement robust sensorless field-oriented control for permanent magnet synchronous motor drives. The proposed method can accurately estimate rotor position by mitigating the dependence on quality of the magnitude and phase angle of the estimated stator flux linkage. A high-accuracy load angle calculation based on <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$d$ </tex-math></inline-formula> - <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$q$ </tex-math></inline-formula> -axis current estimation method is first developed for further rotor position determination. In the rotor position calculation, the reference flux linkage magnitude is used instead of the estimated one to avoid the influence of potential high noise levels during low speed operation. As a result, the rotor angle estimation depends only on the phase angle of stator flux linkage, without the effect of its magnitude. The estimation accuracy can thus be improved. Also, by employing a simple stator flux linkage phase lag compensator, the performance of the proposed sensorless method can be dramatically improved at low speed. Moreover, the problem of motor parameter variation (e.g., changes in winding resistance, stator inductances, and permanent magnetic flux linkage) has been analyzed and overcome. Finally, comparisons between conventional and proposed methods are presented with simulations and experiments to demonstrate the effectiveness and reliability of the proposed method.

Assessment and Mitigation of Dynamic Instabilities in Single-Stage Grid-Connected Photovoltaic Systems With Reduced DC-Link Capacitance

Single-stage utility-scale photovoltaic (PV) systems are usually interfaced with the host grid via a centralized voltage-source converter (VSC). Recently, and due to their reliability, the dc-link film capacitors are favored over electrolytic types in grid-connected applications. However, the capacitance per unit volume of film capacitors is significantly smaller than electrolytic capacitors. The overall system stability might be compromised by the reduction of the dc-link capacitance, particularly in PV systems that have a dynamic resistance that varies with operating conditions. Using a detailed small-signal model of the grid-connected PV system, it is shown in this paper that the reduction of the dc-link capacitance interferes with the dynamic resistance of the PV array, which eventually leads to instabilities. The minimum dc-link capacitance that preserves the overall system stability is determined. A simple and effective active compensator is developed to mitigate the instabilities with the reduced dc-link capacitance. Detailed time-domain simulations are presented to validate the analytical results and show the proposed compensator’s effectiveness in preserving the system stability.

Efficient generation of third harmonics in Yb-doped femtosecond fiber laser via spatial and temporal walk-off compensation

On the basis of a home-made femtosecond Yb-doped fiber laser, we designed a compact and efficient third harmonic generation scheme by a simple compensation plate of β-BaB2O4 crystal. The compensation plate is optimized through its thickness and cutting angle to reverse both spatial and temporal walk-off. By optimizing the parameters of the compensation plate and incident light intensity, a maximum output of 2.23 W with a repetition rate of 1 MHz at 345 nm is obtained, which implies a conversion efficiency of 23% from the infrared to ultraviolet.

Compensation and Staffing to Trade Off Speed and Quality in Large Service Systems

Most common queueing models used for service system design assume the servers work at fixed (possibly heterogeneous) rates. However, real-life service systems are staffed by people, and people may change their service speed in response to their compensation incentives. The delicacy is that the resulting employee service rate affects the staffing, but also the staffing affects the resulting employee service rate. Our objective in this paper is to find a joint staffing and compensation policy that induces optimal service system performance.We do this under the assumption that there is a trade-off between service speed and quality, and employees are paid based on both. The employees each selfishly choose their own service speed in order to maximize their own expected utility, which can have both a monetary and a non-monetary component. We characterize the symmetric equilibrium service speed in large systems under a simple linear staffing and compensation policy. We show that there is a limiting first best policy within that class. The important insight is that in the large system limit the problem decouples into one where the system manager first jointly determines the staffing and service speed, and second uses the compensation to achieve that desired service speed. We further show the conditions under which a critically loaded, efficiency-driven, quality-driven, or mixed regime — in which there is simultaneous customer abandonment and server idling — emerges under a first-best policy.

Compensation of Magnetic Force of an Electromagnet for Compression Mode Characterization of Magnetorheological Elastomers

Compression mode characterizations of magnetorheological elastomers (MREs) involve challenges associated with compensating for the magnetic force generated by electromagnets. Different series of magnetic force and flux measurements were performed in order to establish a general systematic methodology for compensating for the magnetic force. In this regard, an optimal design of a UI-shaped electromagnet was realized to facilitate measurements of the force under controlled magnetic flux density up to 1 T. Results revealed notable phase and magnitude differences between the measured static and dynamic magnetic forces, which are found to be mainly dependent on magnetic flux density and frequency. A simple and powerful compensation model was proposed to accurately predict the magnetic force for the entire range of flux density and excitation conditions considered. The proposed model is experimentally validated, and then employed to identify viscoelastic force of an isotropic MRE. Results revealed maximum errors in equivalent stiffness and damping constants of the MRE in the orders of 90% and 163%, respectively, without compensation. The proposed methodology provides a framework for accurate characterization of MREs in the compression mode.

A Simple Blind Sampling Frequency Offset Estimation Scheme for Short-Reach DD-OFDM Systems

In this paper, a simple and overhead-free sampling frequency offset (SFO) blind estimation and compensation scheme is proposed and experimentally demonstrated in a short-reach direct detection orthogonal frequency division multiplexing (DD-OFDM) transmission system. After extracting subcarriers of OFDM symbols from multiple OFDM frames, the phase shift is obtained by the fourth-power algorithm, and the obtained results are averaged to perform phase estimation. It can achieve high-precision SFO estimation while ensuring low computational complexity as well as high spectral efficiency. The experimental results show that the SFO estimation accuracy using the proposed scheme can be significantly reduced to as low as ±3 ppm when SFO ranges from -1000 ppm to +1000 ppm after 20-km standard single-mode fiber (SSMF) transmission. Moreover, for the QPSK/16QAM encoded DD-OFDM systems aided by the proposed scheme, up to ±200 ppm SFO can be compensated with slight error vector magnitude (EVM) penalties after 20-km SSMF transmission. Furthermore, the results demonstrate that despite the existence of severe SFO, our proposed SFO compensation scheme can offer nearly negligible power penalties in the DD-OFDM system with optical back-to-back (OBTB) and 20-km SSMF transmission as compared to the ideal case without SFO.