Development and evaluation of a two-axial shearing force sensor consisting of an optical sensor chip and elastic gum frame

We developed a promising shearing force sensor that is small in size and can measure shearing force along two axes independently. This sensor consists of an elastic gum frame and an optical sensor chip (6 mm × 6 mm × 8 mm). From the experimental results, the resolutions of the sensor along the x- and y-axes are found to be 0.070 N and 0.063 N. We also experimentally demonstrated that the sensor can separately measure shearing force along two axes. Finally, we demonstrated that the scale factor which correspond to resolution and linear portion which correspond to measuring range of the signals can be changed easily by using three types of elastic gum frame. This sensor can be embedded in the finger of a robot hand and use it to not only measure shearing force but also detect the slip phenomenon.     

Study on the evaluation of cylinder’s global sizes

In ISO 14405-1, the global sizes, such as least-squares diameter, minimum circumscribed diameter and maximum inscribed diameter are defined. The diameters above can be measured by using cylindrical coordinate measuring method like the circular section measuring method of cylindricity error. The determination method of the least-squares diameter was firstly given based on the cylindrical measuring system, and the optimization models of the minimum circumscribed diameter and the maximum inscribed diameter were built, respectively. The corresponding objective functions were unified as “minimax” expressions. For the four axis parameters of the cylinder with the minimum circumscribed diameter or the maximum inscribed diameter, the searching ranges of cylinder’s axis parameters for their optimal solutions were defined numerically. Thereafter, the genetic, steepest decent and BFGS-0.618 algorithms were introduced, and the optimization evaluation algorithms of two kinds of diameters mentioned above were given. Based on many cylinders’ profiles obtained by the circular section measuring method on a measuring instrument of cylinder’s global sizes which was developed by Zhongyuan University of Technology, Zhengzhou, China. The accuracy, efficiency and suitability of three optimization algorithms were investigated through the evaluation of a lot of the minimum circumscribed diameters and the maximum inscribed diameters. The measurement uncertainty of the global sizes for the cylindrical specimen was analyzed, and the measurement uncertainties of the sizes in the radial and z directions are ±0.95 μm and ±0.5 μm, respectively. The total measurement uncertainties of the global sizes of the cylindrical specimens with the specifications of ϕ10 × 120 mm and ϕ100 × 300 mm are ±3.8 μm and ±5.7 μm, respectively. The investigation results showed that for the evaluation of the globe sizes, any one of three algorithms above is not absolutely prior to the other two algorithms while considering both evaluation accuracy and efficiency, and the difference of their evaluation results do not exceed 0.5 μm. On the other hand, many points between the maximum value and the least value do not affect the evaluation results in optimization process. For improving the evaluation efficiency, by de-selecting those points while considering the characteristic parameter was also studied based on the statistic method and experiment. Coefficient t should be less than 0.3 to ensure the evaluation accuracy. This research may be useful for developing the next generation measurement instrument for the global sizes and the way forward for the digital manufacturing.     

Precision design and control of a flexure-based roll-to-roll printing system

This paper presents the design, characterization, and control of a flexure-based roll-to-roll (R2R) printing system that achieves nanometer level precision and repeatability. The R2R system includes an unwinding/rewinding module, a web guide mechanism, and a core positioning stage consisting of two monolithic compliant X–Y stages that control the position/force of the print roller. During the printing process, capacitance probes, eddy current sensors and load cells are used to monitor the displacements of the flexure stage and contact force in real time. Control strategies, including decoupling, PID, and cascade control, have been implemented to decouple the cross-axis and cross-stage motion coupling effect and improve the overall precision and dynamic performance. In actual printing processes, the contact force and roller position can be uniformly controlled within ±0.05 N and ±200 nm respectively across a 4 in. wide PET web. To demonstrate the performance, a positive microcontact printing (MCP) process is adapted to the R2R system, printing various fine metal patterns, e.g., optical gratings and electrodes, in a continuous fashion.     

Multi-range sensors for the measurement of liquid film thickness distributions based on electrical conductance

The paper presents an approach toward an enhancement of the measuring range of high-speed sensors for the measurement of liquid film thickness distributions based on electrical conductance. This type of sensors consists of electrodes mounted flush to the wall. The sampling of the current generated between a pair of neighboring electrode is used as a measure of the film thickness. Such sensors have a limited measuring range, which is proportional to the lateral distance between the electrodes. The range is therefore coupled to the spatial resolution. The proposed new design allows an extension of the film thickness range by combining electrode matrices of different resolution in one and the same sensor. In this way, a high spatial resolution is reached with a small thickness range, whereas a film thickness that exceeds the range of the high resolution measurement can still be acquired even though on the costs of a lower spatial resolution. A simultaneous signal acquisition with a sampling frequency of 3.2 kHz combines three measuring ranges for the characterization of a two-dimensional film thickness distribution: (1) thickness range 0–600 µm, lateral resolution 2×2 mm², (2) thickness range 400–1300 µm, lateral resolution 4×4 mm², and (3) thickness range 1000–3500 µm, lateral resolution 12×12 mm². The functionality of this concept sensor is demonstrated by tests in a horizontal wavy stratified air–water flow at ambient conditions. Using flexible printed circuit board technology to manufacture the sensor makes it possible to place the sensor at the inner surface of a circular pipe.     

Classification of vertebral column disorders and lumbar discs disease using attribute weighting algorithm with mean shift clustering

In this article, a new data pre-processing method has been suggested to detect and classify vertebral column disorders and lumbar disc diseases with a high accuracy level. The suggested pre-processing method is called the Mean Shift Clustering-Based Attribute Weighting (MSCBAW) and is based primarily on mean shift clustering algorithm finding the number of the sets automatically. In this study, we have used two different datasets including lumbar disc diseases (with two classes-our database) and vertebral column disorders datasets (with two or three classes) taken from UCI (University of California at Irvine) machine learning database to test the proposed approach. The MSCBAW method is working as follows: first of all, the centres of the sets automatically for each characteristics in dataset by using the mean shift clustering algorithm are computed. And then, the mean values of each property in dataset are calculated. The weighted datasets by multiplying these mean values by each property value in the dataset that have been obtained by dividing the above mentioned mean values by the centres of the sets belonging to the relevant property are achieved. After the data weighting stage, three different classification algorithms that included the k-NN (k-Nearest Neighbour), RBF–NN (Radial Basis Function–Neural Network) and SVM (Support Vector Machine) classifying algorithms have been used to classify the datasets. In the classification of vertebral column disorders dataset with two classes (normal or abnormal), while the obtained classification accuracies and kappa values were 78.70% ± 0.455 (the classification accuracy ± standard deviation), 81.93% ± 0.899, and 80.32% ± 0.56 using SVM, k-NN (for k = 1), and RBF–NN classifiers, respectively, the combinations of MSCBAW and SVM, k-NN (for k = 1), and RBF–NN classifiers were obtained 99.03% ± 0.977, 99.67% ± 0.992, and 99.35% ± 0.9852, respectively. In the classification of second dataset named vertebral column disorders dataset with three classes (Normal, Disk Hernia, and Spondylolisthesis), while the obtained classification accuracies and kappa values were 74.51% ± 0.581, 78.70% ± 0.659, and 83.22% ± 0.728 using SVM, k-NN (for k = 1), and RBF–NN classifiers, respectively, the combinations of MSCBAW and SVM, k-NN (for k = 1), and RBF–NN classifiers were obtained 99.35% ± 0.989, 96.77% ± 0.948, and 99.67% ± 0.994, respectively. As for the lumbar disc dataset, while the obtained classification accuracies and kappa values were 94.54% ± 0.974, 94.54% ± 0.877, and 93.45% ± 0.856 using SVM, k-NN (for k = 1), and RBF–NN classifiers, respectively, the combinations of MSCBAW and SVM, k-NN (for k = 1), and RBF–NN classifiers were obtained 100% ± 1.00, 99.63% ± 0.991, and 99.63% ± 0.991, respectively. The best hybrid models in the classification of vertebral column disorders dataset with two classes, vertebral column disorders dataset with three classes, and lumbar disc dataset were the combination of MSCBAW and k-NN classifier, the combination of MSCBAW and RBF–NN classifier, and the combination of MSCBAW and SVM classifier, respectively.     

A long-stroke 3D contact scanning probe for micro/nano coordinate measuring machine

This paper presents a long-stroke contact scanning probe with high precision and low stiffness for micro/nano coordinate measuring machines (micro/nano CMMs). The displacements of the probe tip in 3D are detected by two plane mirrors supported by an elastic mechanism, which is comprised of a tungsten stylus, a floating plate and two orthogonal Z-shaped leaf springs fixed to the outer case. A Michelson interferometer is used to detect the vertical displacement of the mirror mounted on the center of the floating plate. An autocollimator based two dimensional angle sensor is used to detect the tilt of the other plane mirror located at the end of the arm of the floating plate. The stiffness and the dynamic properties are investigated by simulation. The optimal structural parameters of the probe are obtained based on the force-motion model and the constrained conditions of stiffness, measurement range and horizontal size. The results of the performance tests show that the probe has a contact force gradient within 0.5 mN/μm, a measuring range of (±20 μm), (±20 μm), and 20 μm, respectively, in X, Y and Z directions, and a measurement standard deviation of 30 nm. The feasibility of the probe has preliminarily been verified by testing the curved surface of a convex lens.     

Measurement and statistical analysis toward reproducibility validation of AZ4562 cylindrical microlenses obtained by reflow

This paper presents the statistical analysis applied into the shape of microlenses (MLs) for validating the high-reproducibility feature of their fabrication process. The MLs were fabricated with the AZ4562 photoresist, using photolithography and thermal reflow processes. Two types of MLs arrays were produced for statistical analysis purposes: the first with a cross-sectional diameter of 24 μm and the second with a cross-sectional diameter of 30 μm, and both with 5 μm spacing between MLs. In the case of 24 μm diameter arrays, the measurements showed a mean difference in diameter of 2.78 μm with a standard deviation (SD) of 0.22 μm (e.g., 2.78 ± 0.22 μm of SD) before the reflow, and 2.34 ± 0.35 μm of SD after the reflow. For the same arrays, the mean difference in height obtained was, comparatively to the 5.06 μm expected, 0.76 ± 0.10 μm of SD before the reflow and 1.91 ± 0.15 μm of SD after the reflow, respectively. A mean difference in diameter of 2.64 ± 0.41 μm of SD before the reflow, and 1.87 ± 0.34 μm of SD after the reflow was obtained for 30 μm diameter MLs arrays. For these MLs, a mean difference in height of 0.71 ± 0.12 μm of SD before the reflow and 2.24 ± 0.24 μm of SD after the thermal reflow was obtained, in comparison to the 5.06 μm of height expected to obtain. These results validate the requirement for reproducibility and opens good perspectives for applying this fabrication process on high-volume production of MLs arrays.     

Feasibility assessment of magnetic resonance-thermometry on pancreas undergoing laser ablation: Sensitivity analysis of three sequences

Laser ablation (LA) is a minimally invasive technique for the treatment of tumors as an alternative to surgical resection. The light absorbed by tissue is converted into heat, and causes irreversible cell damage when temperatures higher than 60 °C are reached. The knowledge in real time of temperature may be particularly beneficial for adjusting laser settings applied during treatment and to be notified in real time about its end-point. As a consequence, several techniques for temperature monitoring within the tissue have been investigated along the last decades. In the field of LA, particularly attractive are non-invasive methods. Among these techniques, thermometry based on the analysis of Magnetic Resonance Imaging (MR-thermometry) has gaining large acceptance in this field. MR-thermometry allows estimating the temperature variation thanks to the thermal dependence of several MRI parameters, among others the most promising are T₁ relaxation time, and proton resonance frequency shift.The aim of this study is to assess the sensitivity of MRI thermometry using three T₁-weighted sequences (i.e., Inversion Recovery Turbo-FLASH, IRTF, Saturation Recovery Turbo-FLASH, SRTF, and FLASH) using an 1.5-T MR scanner on healthy swine pancreases undergoing LA. The reference temperature was measured by MRI-compatible fiber optic sensors (fiber Bragg grating sensors). The sensitivity of the proposed techniques was estimated and compared. The thermal sensitivity of the three sequences was −1.47 ± 0.08 °C⁻¹, −0.95 ± 0.05 °C⁻¹, and −0.56 ± 0.04 °C⁻¹ for IRTF, SRTF and FLASH, respectively. Results show that the proposed technique may be adequate for temperature monitoring during LA.     

Determination of the thermal conductivity of composted material

The objective of this study was to develop a reliable method for the determination of the thermal conductivity of composted material using the TP08 probe. Study was set out to determine whether the selection of a signal fragment used to establish thermal conductivity (λ), has a significant influence on the results. Also minimum number of measurements was determined for every phase of the composting process. No significant differences were reported between results, but certain changes in the value of λ were noted. In successive stages of the process, thermal conductivity of composted material were: 0.31 ± 0.09, 0.45 ± 0.14, 0.27 ± 0.03 and 0.37 ± 0.17 W m⁻¹ K⁻¹.     

Performance evaluation of a cheap,open source,digital environmental monitor based on the Raspberry Pi

We report on the design, construction and evaluation of a low-cost digital environmental monitoring system based on a popular micro-computer board and mass market digital sensors. The system is based around the use of open source software and readily available digital sensors, providing key parameters required for environmentally-controlled calibration laboratories: air temperature, pressure and humidity. Each system logs data at set intervals with front-panel display, web page graphical display and email alerting when exceeding set tolerances. The sensors have been calibrated at the National Physical Laboratory using standards traceable to the SI. Long term stability of the system is estimated and in addition to monitoring of laboratory environments for regulatory purposes, the systems can also be used to provide on-demand values for local refractive index with an expanded (k = 2) uncertainty of 1.1 × 10⁻⁷ as required for many optical-based measuring systems.     

Ability of different balance tests to discriminate between young and elderly subjects

Different balance tests are used to assess age-related decline of movement function. Good basic metric characteristics are in order for a balance test to become a useful assessment tool for clinical and research practice. By measuring balance of 27 young (22.3 ± 3.6 years) and 23 elderly (82.3 ± 9.6 years) adults discrimination power (ROC curve) of five common and one novel balance test was assessed (maximal lunge, quick step, leaning forwards and backwards, star excursion balance test, forward reach and centre-of-pressure (CoP) tracking, respectively). In all of the tests at least one parameter had high discriminating power (ROC area > 0.8, p < 0.05; d > 0.8). CoP displacement derived parameters in the star excursion balance test had high discrimination power and had the potential to give additional information on balance, besides the outreach distance. The interaction effect between age and direction of reach or lean proved to be insignificant, with the frequency of CoP direction changes in anterior–posterior direction during star excursion balance test being the only exception. The results of this study add to the methodological ground base in clinical balance assessment protocols by identifying parameters with the highest discriminating power of the most commonly applied balance assessment tests.     

Intra-session reliability of traditional and nonlinear time-series posturographic measures in a semi-tandem stance: A reference to age

The purpose of this study was to evaluate the intra-session reliability of traditional and nonlinear time-series center of pressure (CoP) based measures of postural sway during upright semi-tandem quiet stance in young vs. older subjects. Seventy-four healthy volunteers (40 young individuals, mean age: 27 ± 6 yrs; 34 older individuals, mean age: 79 ± 8 yrs) performed three 30-s trials of semi-tandem quiet stance on a force plate with their eyes open. Traditional posturography analysis and 4 nonlinear time-series analyses (sway density plots, diffusion plots, recurrence quantification, sample entropy analyses) were applied to the recorded CoP time series, based on which 13 traditional and 32 nonlinear time-series CoP-based measures were calculated. Significant trial-to-trial improvements (particularly between the first and second trial) were observed in the calculated CoP measures in only 2 and 4 cases in the young and older individuals respectively. Regarding the traditional CoP measures, the highest intraclass correlation coefficients (ICC_average, i.e. ICC_2,k) (0.75–0.96) and the lowest coefficients of variation (CV) (8.2–27.3%) in both age groups were observed in the mean frequency of CoP local extrema, the mean amplitude of CoP excursion, and the time-normalized CoP area, although for some of the measures we recommend an additional familiarization trial due to systematic bias. Regarding the structural mechanics CoP measures, the highest ICCa (0.70–0.94) and the lowest CVs (1.2–8.4%) in both age groups were observed in those derived from recurrence quantification and sample entropy analyses, respectively. These CoP measures could be recommended for further use in basic and clinical studies, particularly those on age-related changes in postural control during the semi-tandem quiet stance.     

On the film thickness dependence of shear strengths in sliding,boundary-layer friction

The density functional theory calculated pressure-dependent shear strength S of a four-layer slab of KCl on a Fe(1 0 0) substrate is compared to previous calculations for a bilayer slab to gauge the effect of film thickness on the shear properties of the film. It is found that the shear strength varies with pressure as S = S₀ + αP, where P is the contact pressure. The resulting calculated values for the four-layer slab are S₀〈1 0〉 = 62 ± 15 and S₀〈1 1〉 = 65 ± 11 MPa while α〈1 0〉 and α〈1 1〉 are 0.06 ± 0.01. The values are very close to those calculated for the bilayer slab of S₀〈1 0〉 = 64 ± 9 and S₀〈1 1〉 =69 ± 8 MPa and α〈1 0〉 and α〈1 1〉 of 0.05 ± 0.01, and in reasonable agreement with the experiment values. These results suggest that the thickness of the film does not have a profound effect on the shear properties.     

Development of high-precision micro-roundness measuring machine using a high-sensitivity and compact multi-beam angle sensor

With recent development in advanced manufacturing, demand for nanometric accuracy in dimensional metrology has increased dramatically. To satisfy these requirements, we propose a high-accuracy micro-roundness measuring machine (micro-RMM) using a multi-beam angle sensor (MBAS). The micro-RMM includes three main parts: the MBAS, a rotary unit, and a bearing system. The MBAS has been designed and established in order to improve motion accuracy of the micro-RMM. The dimensions of the MBAS are 125(L) mm × 130(W) mm × 90(H) mm. Compared with other methods, an MBAS is less susceptible to spindle error (stage-independence) when detecting angles, can maintain high sensitivity with miniaturized size, and can be used conveniently at the factory level. The optical probe, reported in this paper, is based on the principle of an autocollimator, and the stability is improved when using the MBAS. Unlike multi-probe methods, the micro-RMM is constructed to realize roundness measurement by using only one probe, which is less susceptible to instrumental errors. Experimental results confirming the feasibility of the multi-beam angle sensor for roundness measurement are also presented.     

Solid particle erosion studies on polyphenylene sulfide composites and prediction on erosion data using artificial neural networks

Solid particle erosion behavior of polyphenylene sulfide, reinforced by short glass fibers with varying fiber content (0–40 wt%) has been studied. Steady-state erosion rates have been evaluated at different impact angles (15–90°) and impact velocities (25–66 m/s) using silica sand particles (200 ± 50 μm) as an erodent. PPS and its composites exhibited maximum erosion rate at 30° impact angle indicating ductile erosion behavior. Though PPS is a brittle thermoplastic, incubation period was found for neat resin and its composites at normal impact (α = 90°). The erosion rates of PPS composites increased with increasing amount of glass fiber. Morphology of eroded surfaces was examined using scanning electron microscopy (SEM) and possible wear mechanisms were discussed. Also, artificial neural networks (ANNs) technique has been used to predict the erosion rate based on the experimentally measured database of PPS composites. The results show that the predicted data are well acceptable when comparing them to measured values. A well-trained ANN is expected to be very helpful for prediction of wear data for systematic parameter studies.     

Small-capacity deadweight force standard machine compensating loading frame

The Korea Research Institute of Standards and Science (KRISS) has developed a 20 N deadweight force standard machine. The machine consists of a weight stack, a loading frame, a taring system, a main body and a control system. The taring system has the role of compensating the initial force generated by the loading frame. With two motors, a displacement sensor, several limit switches, and a synthetic control system consisting of a programmable logic controller and an operating PC, the machine can be operated almost fully automatically. The machine can generate a compressive force in the range of 0.5–22 N with a relative expanded uncertainty of 1.0 × 10^–4. The machine was compared with a 200 N deadweight force standard machine. In the comparison, the relative deviation was 5.8 × 10^–5, less than the declared expanded uncertainty of the force standard machines, therefore confirming the machine’s accuracy.     

Towards the standardization of ballistocardiography systems for J-peak timing measurement

There is a growing interest in accurately measuring the timing of the J peak of the ballistocardiogram (BCG) in order to obtain cardiovascular function markers non-invasively, especially in modern home healthcare applications. In this paper we have studied the effect that some common uncertainty sources have in the time measurement of the J peak. This is a necessary step towards the standardization of modern ballistocardiography systems equivalent to that available for ECG systems. We conclude that, to reduce J peak time uncertainty below the measured intrinsic uncertainty of about ±2 ms, the minimal bandwidth should be from 1.5 Hz to 22.5 Hz; the sampling frequency can be decreased up to 50 Hz when using cubic spline interpolation; 5 bits are required to quantify the signal, and signal-to-noise ratio (SNR) and signal-to-interference ratio (SIR) should be over 40 dB and 3 dB respectively.     

Optimization of medicinal plant extraction methods and their encapsulation through extrusion technology

In this study, aqueous extracts of Plectranthus ecklonii, Plectranthus grandidentatus, Plectranthus ornatus, Plectranthus porcatus, and Plectranthus saccatus were prepared using infusion, decoction, microwave and ultrasonic methods. Rosmarinic and caffeic acids were their major components while chlorogenic acid was for the first time found in a Lamiaceae extract (P. saccatus), being the acetylcholinesterase (AChE) inhibition and the antioxidant activities furthermore evaluated. P. ecklonii microwave extract with a high yield (22.9 ± 0.3 mg of dry plant extract/mL), the best AChE inhibition activity (59.14 ± 4.97%) and a strong antioxidant activity (25.47 ± 1.1%) at 1 mg/mL, was then successfully encapsulated into alginate beads (98.64–100.0%). The high rosmarinic and caffeic acids content as well the high AChE inhibition and antioxidant properties after the encapsulation strongly indicate that this strategy could potentiate the action of the plant extract by promoting a protective effect and a sustained release of active constituents and, ultimately, improve their pharmacological effects.     

Monitoring of strain induced by heat of hydration,cyclic and dynamic loads in concrete structures using fiber-optics sensors

Advances in sensors technology provided an opportunity to monitor structures during different construction stages, as well as the behavior of concrete elements during hydration and strength gain. In this paper, embedded Fabry–Pérot fiber-optic sensors were utilized in an experimental investigation to study the hydration process in two different concrete volumes. In addition, the sensors performance under cyclic and torsional loading was investigated. The results showed that up to +300 μstrains could be developed until the final setting is reached. The increase in strain was accompanied by a 55 °C (130 °F) increase in temperature during the first 24 h. These values vary based on the nature of the mix and the concrete volume. In the cyclic and torsion tests, the fiber-optic sensors responded to load variations and were capable of recording samples responses as small as 1 μstrain.     

Development and evaluation of a compact 6-axis force/moment sensor with a serial structure for the humanoid robot foot

In order to walk safely, forces and moments exerted on humanoid robot foot should be measured and used for controlling the robot. This paper describes the development and evaluation of a six-axis force/moment sensor used under humanoid robot foot. The developed sensor is capable of measuring 400 N horizontal force, 1000 N vertical force, 20 N·m moment about the horizontal axis and 10 N·m moment about the vertical axis using rectangular cross-sectional beams. The structure of the sensor is newly modeled, and the sensing elements are simulated by using finite element method (FEM). Then the sensor is fabricated by attaching strain gages onto the beams. Finally, a characteristic test of the developed sensor is carried out, and the output from FEM analysis agrees with those from the characteristic test.