Temperature Compensation Strategy Research Articles

Investigation of an indirect measurement method of ultrasonic bone cutting forces based on strain sensors

The measurement model of ultrasonic bone cutting force is an urgent problem to be solved in the application of ultrasonic osteotomy in robot assisted orthopedic surgery, which is of great significance for achieving bone layer perception and cutting force control during the surgical process. This article proposes an indirect measurement method of ultrasonic bone cutting force based on strain. Firstly, according to the axial vibration strain distribution curve of the ultrasonic osteotomy, the optimal measurement position for the strain gauge is selected as the high strain position (with a high signal-to-noise ratio), and the temperature compensation strategy of the dual strain gauge method is used to reduce or eliminate the thermal effects during the strain measurement. Then, the Pearson correlation coefficient between strain and cutting force in different cutting directions is calculated, and there is a strong positive correlation between strain and cutting force. Finally, the least squares method was used to obtain indirect measurement models of ultrasonic bone cutting force based on strain in different cutting directions. The experimental results showed that the waveform of cutting force measured indirectly based on strain was in good agreement with the waveform of cutting force measured directly by the force sensor. The error between the effective value of indirect measurement of cutting force and the effective value of direct measurement of cutting force did not exceed 13%, which verified the feasibility and effectiveness of this method. The indirect measurement models of ultrasonic bone cutting force based on strain will become a cost-effective choice with good accuracy and high sensitivity, providing a theoretical basis for orthopedic robots to perceive and control cutting force, and promoting the clinical application of ultrasonic osteotomy in orthopedic robots.

A novel RBFNN-UKF-based SOC estimator for automatic underwater vehicles considering a temperature compensation strategy

Accurate state of charge (SOC) estimation of batteries is a prerequisite for the reliable operation of automatic underwater vehicles. Currently, the accuracy of traditional SOC evaluation algorithms deteriorates significantly at low temperatures and low SOCs. Hence, a novel SOC estimator is proposed in this study, consisting of three efforts. Firstly, a new radial basis function neural network (RBFNN) battery model is built to replace the equivalent circuit model (ECM) for SOC estimation. Then, based on the relation between SOC and terminal voltage at a different temperature, a temperature compensation strategy is developed, which is an effortless operation and does not increase the computational burden. Finally, incorporating the new battery model, the temperature compensation strategy, and the unscented Kalman filter (UKF), a novel SOC estimation frame expressed as RBFNN-UKF is designed.The performance of the proposed method, including accuracy, generalization ability, and low-temperature adaptation, is evaluated systematically based on a publicly available dataset, where the inaccurate initial value and the current errors are added in each case. The results show that: (1) The SOC estimation curve of RBFNN-UKF can converge quickly to the reference curve and maintain good consistency even at low SOCs; (2) The proposed method exhibits excellent generalization capability for different dynamic cycles; (3) At low temperatures, the SOC estimation error of the RBFNN-UKF is reduced to 17 % of traditional ECM-UKF algorithm with the recursive least squares parameter identification method. The above results indicate that the proposed RBFNN-UKF-based SOC estimator has a high application value for AUVs and other vehicles working in complex environments.

A novel data-based approach for monitoring fatigue crack propagation in welded joints under varying ambient temperature using the electromechanical admittance

Fatigue crack growth is one of the most common damage mechanisms of structural components and can result in a sudden and unexpected abrupt fracture which can cause catastrophic failure. Thus, monitoring of crack propagation is an important topic of structural health monitoring. For that reason, this work aims at the detection of crack propagation by the application of a high-frequency vibration-based method, using the electromechanical admittance (EMA). It enables the local monitoring of the coupled dynamic behavior of the structure and the piezoelectric transducer which changes, for example, due to damage. It is the purpose of this study to develop a method from the recorded data reflecting fatigue crack growth in weld zones. As it is known that the data are affected by temperature, a temperature compensation strategy is considered. In this study, a presentation of the coupled EMA data has been found, which allows the isolation of the crack propagation effects. Within the scope of fatigue experiments, fatigue cracks were introduced into threaded bolts of rail support points, welded onto base plates. In practice, they are embedded in a layer of mortar and, therefore, have poor accessibility. Electromechanical impedance measurements were carried out at different states of fatigue crack growth. The fatigue crack growth was validated by strain gauge measurements executed during the fatigue experiment. The proposed feature was calculated from the recorded EMA data. The technique produces promising results detecting fatigue cracks and can also be transferred to similar types of welded joints or rods where fatigue crack growth occurs.

High-accuracy ultrasonic method for in-situ monitoring of oil film thickness in a thrust bearing

The ultrasonic method has been widely applied to measure the oil film thickness – a critical variable that reflects lubrication conditions. However, due to the thermal dependence of ultrasonic signals, significant deviations in film thickness measurements are introduced, hindering the in-situ application of the ultrasonic technique. To address this issue, a real-time temperature compensation method that can accurately obtain the frequency domain information of the reference signal is proposed. Specifically, the reflection from the substrate-coating interface compensates for the thermal effect on the phase increment and amplitude attenuation – this is noted as “self-calibration”. An extra experimental test with a substrate-coating-air structure is performed to calibrate the thermal effect on the coating-induced phase shift – this part is denoted as “pre-calibration”. The combination of “self-calibration” and “pre-calibration” enables the overall temperature compensation strategy. After the effectiveness validation with a temperature-controlled experiment, the proposed method is implemented in a thrust bearing in a heavy-duty hydropower generator with full running conditions, including loading and unloading, normal speed and shut-down. The largely ranged oil film thickness (3–330 μm) is ultrasonically measured and compared with the theoretical value, showing a higher measurement accuracy than the eddy current method.

Stress Testing for Performance Analysis of Orientation Estimation Algorithms

Technological advancements have seen the spread of MEMS (Micro-electromechanical Systems) based sensors such as IMU (Inertial Measurement Unit) systems. The latter provide object orientation information in numerous applications such as smartphones, robotics, automotive, drones, and many others. In more detail, IMUs based on MEMS technology are characterized by small size, low power, and low cost. Technically, orientation information is provided by appropriate orientation estimation algorithms fed with quantities measured by MEMS sensors, such as acceleration, angular velocity, and magnetic field. A preliminary work pointed out that such MEMS sensors suffer significant drifts when they have to endure non-standard operating profiles in terms of thermal conditions. However, when considering very low-cost devices, the influence of temperature on the operation of orientation estimation algorithms still remains an important research gap in the literature. To deal with this important aspect, the paper proposes a specific test plan to analyze the performances of MEMS-based IMUs by considering a temperature stress test. Therefore, the effect of temperature was first analyzed on the individual sensors of the IMU (accelerometer, gyroscope, and magnetometer), then the effects of a very simple temperature compensation strategy were analyzed to highlight the importance of such step. Specifically, the effects of not compensating for temperature were studied considering a low-cost commercial IMU typically used in various fields of application. To better quantify such effects in practical applications, two well-known orientation estimation algorithms (i.e., Complementary Filter and AHRS) typically fed by IMUs output have been considered. The experimental results obtained using the custom devices under test show that temperature compensation is necessary for the best performance of the analyzed orientation estimation algorithms.

Temperature compensation strategy for ultrasonic-based measurement of oil film thickness

Due to non-destructive testing characteristics, ultrasonic-based measurements are regarded as potential strategies in real-time monitoring of varied lubricant film thickness for tribological systems. Different theoretical models have been recently developed to calculate the film thickness from ultrasonic echo waves. However, the temperature influence on ultrasonic systems (for example, the acoustic parameters of materials and piezoelectric elements), which is non-negligible in the continuously running equipment, especially for heavy-loaded lubricated systems, has scarcely been considered. In this paper, the sensitivity of different parameters to the temperature variation is investigated in classical ultrasonic models. With the theoretical error analysis, a comprehensive temperature compensation strategy that considering the acoustic speed, material density, and reference signal, is proposed and integrated into the ultrasonic measurement algorithms. It is worth noting that the amplitude attenuation, waveform expansion, and signal time shift are considered in the compensation of the reference signal. Experimental verification is finally carried out in a calibrated rig with swept lubricant film thickness and different ambient temperatures. Test results suggest that the ultrasonic measurements with the proposed strategy effectively compensates the temperature influence and enables accurate calculations of lubricant film thickness under varying temperatures.

Study on the FPGA-based Temperature Compensation for the SiPM of CEPC ECAL Prototype

Silicon photomultiplier (SiPM), with the advantages of high gain, low noise, small volumn, is used as the photoelectric converter in the detection unit of the electromagnetic calorimeter (ECAL) prototype of the Circular Electron Positron Collider (CEPC). However, the ambient temperature has influences on the SiPM gain, which will therefore affect the energy resolution of the calorimeter. To solve this problem, a temperature compensation strategy including the temperature field reconstruction and the high voltage control is proposed in this article. The compensation strategy is implemented in the Field Programmable Gate Array (FPGA) of ECAL prototype which can work real-timely and the LED test and the radiation source test both show good results. When using the temperature compensation, the variation of the system gain is less than 10% when temperature changes from 20̂C to 40̂C, compared with that of 35% without the compensation.

Co-composting of sewage sludge and Phragmites australis using different insulating strategies

Insulating strategies are indispensable for laboratory-scale composting reactors, however, current insulation methods interfere with the aerobic fermentation behaviors related to composting. To address this issue, a centre-oriented real-time temperature compensation strategy was designed in this study. Five 9 L reactors (R1–R5) with different insulation strategies were used for the co-composting of dewatered sludge and Phragmites australis and compared. The process performance was assessed by monitoring the temperature, O2 and CO2 emissions, the physical–chemical properties of the composting materials were evaluated by measuring the organic matter (OM), carbon nitrogen ratio (C/N), pH, electrical conductivity (EC), and fluorescence excitation-emission matrix (EEM) spectra. And a 16S rDNA analysis was used to quantify the evolution of bacterial community. The main findings are as follows. Compared with R1 as a control, the insulating strategies can increase the maximum temperature and prolong the thermophilic phase of composting. Comparing R1 and R3 showed that real-time temperature compensation can better restore the real fermentation of the compost. The results showed that R5 had the best composting effect, reaching 69.8 °C, which was 25.1%, 29.7%, 19.3%, and 17.3% higher than R1, R2, R3, and R4, respectively, and remaining in the thermophilic phase for 4.24 d, which is 1.4, 1.5, 1.3, and 0.2 times longer than R1, R2, R3, and R4, respectively. Furthermore, it can significantly reduce the temperature difference between the centre and edge of the reactor, which improved the composting material allocation efficiency and composting process control accuracy, further providing a basis for the actual full-scale composting operation.

Development of temperature-insensitive fibre bragg grating pressure transducer

In this work, the development of an aluminium diaphragm fibre Bragg grating (FBG) pressure transducer with temperature compensation strategy is presented. One of the big challenges for the applications of an FBG pressure transducer is the inconsistency in output wavelength due to temperature variations. This situation leads to huge uncertainties in pressure readings. The aim of this article is to present how to eliminate the effects of temperature variations to the pressure measurements. Two FBG sensors were used; namely as FBG 1 and FBG 2. These FBGs were bonded each one on the diaphragm and base surface of the pressure transducer. The strain readings by the FBG on the diaphragm was normalized by the FBG reference which was pasted on the transducer’s base. This temperature compensation strategy was successful and the FBG pressure transducer was proven to be suitable for pressure measurement of gas with an average error of 2.32%. Besides, the result also shows that, for pressure ranging from 0 to 0.5 MPa, the FBG pressure transduced has sensitivity of 2.8485 nm/MPa with linear fitting coefficient of 99.97%.

Model-based statistical guided wave damage detection for an aluminum plate

Accurate decision-making requires understanding the factors that influence those decisions. In guided wave structural health monitoring, the first aim is to detect the presence of damage. This decision is based on the assumption that it is possible to discriminate between undamaged and damaged states. Sensing systems collect data to construct damage statistics, that is, numerical representations of how the state of the structure has changed over time. These damage statistics are designed to be sensitive to damage signatures in the data. However, environmental and operating conditions, such as the presence of temperature variations, perturb damage statistics and weaken decision-making. Temperature compensation strategies applied to reduce these perturbations are imperfect. Qualifying the performance of a temperature compensation strategy to reduce or eliminate the effects of temperature is dependent on the resulting damage statistics. Quality temperature compensation strategies must be able to recover damage statistics and increase damage detection accuracy. This article establishes a framework for evaluating the performance of damage detection methods that use temperature compensation to reduce the effects of environmental and operating conditions. Here, the scale transform and the dynamic time warping method are examined for data with varying temperature and signal-to-noise ratios. Monte Carlo simulations are used to construct probability densities and perform statistical analysis on the resulting damage statistics.

Differential Phononic Crystal Sensor: Towards a Temperature Compensation Mechanism for Field Applications Development.

Phononic crystals are resonant structures with great potential to be implemented in applications as liquid sensors. The use of the symmetry reduction technique allows introducing relevant transmission features inside bandgaps by creating defect modes in a periodic regular structure. These features can be used as measures to quantify changes in the speed of sound of liquid samples that could be related to the concentration of analytes or the presence of pathogens among other interesting applications. In order to be able to implement this new technology in more challenging applications, such as biomedical applications, it is necessary to have a very precise and accurate measurement. Changes in temperature greatly affect the speed of sound of the liquid samples, causing errors in the measurements. This article presents a phononic crystal sensor that, by introducing additional defect modes, can carry out differential measurements as a temperature compensation mechanism. Theoretical studies using the transmission line model and analytes at various temperatures show that the proposed temperature compensation mechanism enhances the performance of the sensor in a significant way. This temperature compensation strategy could also be implemented in crystals with different topologies.

Xenobiotic metabolism modulation after long-term temperature acclimation in juveniles of Solea senegalensis

The Senegalese sole, Solea senegalensis, originates from subtropical waters and displays great adaptability to environmental factors such as temperature. A comprehensive study on the effect of long-term temperature acclimation on xenobiotic metabolism, along with the assessment of other parameters related to physiological status, was designed to characterize the response of this species to temperature fluctuations within a realistic range. S. senegalensis juveniles were acclimated for a period of 60 days to two different ambient temperatures, 15 and 20 °C. Several hepatic, gill, muscular and plasmatic parameters were measured over time at the two temperatures. The lower temperature triggered, over time, the synthesis of hepatic microsomal cytochrome P450-related enzymes (e.g. 7-ethoxyresorufin O-deethylase (EROD), carboxylesterases, and the conjugating enzyme uridine diphosphate glucuronosyltransferase and, more significantly, EROD activity in gills. The antioxidant enzyme activities: catalase and glutathione reductase in liver were positively correlated to temperature. Plasmatic parameters (glucose, lactate, triglycerides and osmolality) were consistent with a good physiological status of the experimental fish. The expression of heat shock proteins in muscle did not significantly change in the two temperature groups. The results evidenced that the subtropical species S. senegalensis also uses the temperature compensation strategy to different degrees for most biotransformation enzymes; this response was more intense and faster in gills than in liver. This compensatory strategy did not apply to antioxidant enzymes and GST. The present findings highlight the need to consider the thermal history of the fish when using S. senegalensis as a sentinel in a biomarker-based pollution monitoring study. The fish plasticity on its strategy of physiological adaptation to temperature changes could contribute to explain the success in the geographical expansion of this species.

Acclimation of Solea senegalensis to different ambient temperatures: implications for thyroidal status and osmoregulation

We have investigated the regulation of thyroidal status and osmoregulatory capacities in juveniles from the teleost Solea senegalensis acclimated to different ambient temperatures. Juveniles, raised in seawater at 19°C, were acclimated for 3 weeks to temperatures of 12, 19 and 26°C. Since our preliminary observations showed that at 12°C feed intake was suppressed, our experimental design controlled for this factor. The concentration of branchial Na+,K+-ATPase, estimated by measurements of enzyme activity at the optimum temperature of this enzyme (37°C), did not change. In contrast, an increase in Na+,K+-ATPase activity (measured at 37°C), was observed in the kidney of 12°C-acclimated fish. In fish acclimated to 12°C, the hepatosomatic index had increased, which correlated with increased plasma levels of triglycerides and non-esterified fatty acids. Plasma cortisol levels did not differ significantly between the experimental groups. In liver and gills, the amount of iodothyronine deiodinases that exhibit thyroid hormone outer ring deiodination was up-regulated only when fish did not feed. When assayed at the acclimation temperature, kidney deiodinase activities were similar, indicating a temperature-compensation strategy. 3,5,3′-triiodothyronine (T3) tissue concentrations in gills and kidney did not differ significantly between experimental groups. However, at 12°C, lower T3 tissue levels were measured in plasma and liver. We conclude that S. senegalensis adjusts its osmoregulatory system to compensate for the effects of temperature on electrolyte transport capacity. The organ-specific changes in thyroid hormone metabolism at different temperatures indicate the involvement of thyroid hormones in temperature acclimation.

Guided wave health monitoring of complex structures by sparse array systems: Influence of temperature changes on performance

Structural health monitoring of complex structures with guided waves is complicated because of the large number of overlapping reflections obtained in time-traces. One of the strategies to avoid having to interpret raw time signals is to use baseline subtraction techniques. However, environmental effects modify the signals, causing large amplitude levels in the subtracted signal which can mask information received from weak reflectors such as defects. A large database of baselines covering environmental effects commonly faced by the structure becomes necessary, and the simple gathering of these baselines becomes a difficult task. This paper investigates how a temperature compensation method can be used to reduce the number of signals required in the database. The strong influence of signal complexity and mode purity on the effectiveness of this method is shown experimentally. Finally, an airframe panel is tested using a temperature compensation strategy developed.