Tactile Probe Research Articles

Development of a Six-Degree-of-Freedom Analog 3D Tactile Probe Based on Non-Contact 2D Sensors.

In this paper, a six-degree-of-freedom analog tactile probe with a new, simple, and robust mechanical design is presented. Its design is based on the use of one elastomeric ring that supports the stylus carrier and allows its movement inside a cubic measuring range of ±3 mm. The position of the probe tip is determined by three low-cost, noncontact, 2D PSD (position-sensitive detector) sensors, facilitating a wider application of this probe to different measuring systems compared to commercial ones. However, several software corrections, regarding the size and orientation of the three LED light beams, must be carried out when using these 2D sensors for this application due to the lack of additional focusing or collimating lenses and the very wide measuring range. The development process, simulation results, correction models, experimental tests, and calibration of this probe are presented. The results demonstrate high repeatability along the X-, Y-, and Z-axes (2.0 µm, 2.0 µm, and 2.1 µm, respectively) and overall accuracies of 6.7 µm, 7.0 µm, and 8.0 µm, respectively, which could be minimized by more complex correction models.

Using micro spheres as reference artifacts for the in-situ characterization of tactile 3D micro probes along the probing sphere’s equator

Abstract Nano and micro coordinate measuring machines (CMMs) have been developed for the characterization of small dimensional features. They require a procedure which enables a traceable and precise characterization of probing spheres. In this contribution we explore the use of well characterized micro spheres as reference artifacts for the in-situ characterization of probing spheres along the probing sphere’s equator. The spheres are characterized using a strategy which is based on a set of tactile surface scans in conjunction with a stitching-algorithm. These micro spheres serve as a reference for the in-situ characterization of a tactile 3D micro probe on a nano measuring machine (NMM-1). Our investigations are based on a sample of eight spheres sourced from two different suppliers. Although the sample is small, we could already observe characteristics which seem to be typical for spheres of a certain type (i.e. nominal radius and material). The experiments indicate that micro spheres are a suitable reference artifact for tactile 3D micro probes. We were able to reproduce the measured mean radius of the probing sphere with a standard deviation of 31 nm using reference spheres whose nominal radius covers a range of 89 µm (61 µm up to 150 µm).

Multisensory peripersonal space: Visual looming stimuli induce stronger response facilitation to tactile than auditory and visual stimulations

Anticipating physical contact with objects in the environment is a key component of efficient motor performance. Peripersonal neurons are thought to play a determinant role in these predictions by enhancing responses to touch when combined with visual stimuli in peripersonal space (PPS). However, recent research challenges the idea that this visuo-tactile integration contributing to the prediction of tactile events occurs strictly in PPS. We hypothesised that enhanced sensory sensitivity in a multisensory context involves not only contact anticipation but also heightened attention towards near-body visual stimuli. To test this hypothesis, Experiment 1 required participants to respond promptly to tactile (probing contact anticipation) and auditory (probing enhanced attention) stimulations presented at different moments of the trajectory of a (social and non-social) looming visual stimulus. Reduction in reaction time as compared to a unisensory baseline was observed from an egocentric distance of around 2 m (inside and outside PPS) for all multisensory conditions and types of visual stimuli. Experiment 2 tested whether these facilitation effects still occur in the absence of a multisensory context, i.e., in a visuo-visual condition. Overall, facilitation effects induced by the looming visual stimulus were comparable in the three sensory modalities outside PPS but were more pronounced for the tactile modality inside PPS (84 cm from the body as estimated by a reachability judgement task). Considered together, the results suggest that facilitation effects induced by visual looming stimuli in multimodal sensory processing rely on the combination of attentional factors and contact anticipation depending on their distance from the body.

Three Sliding Probes Placed on Forelimb Skin for Proprioceptive Feedback Differentially yet Complementarily Contribute to Hand Gesture Detection and Object-Size Discrimination

The purpose was to assess the effectiveness of three sliding tactile probes placed on the forelimb skin to provide proprioceptive feedback for the detection of hand gestures and discrimination of object size. Tactile contactors representing the first three fingers were driven along the proximodistal axis by linear servo motors. Twenty healthy subjects were involved in the gesture detection test, with 10 of them also participating in the object-size discrimination task. Motors were controlled by computer in the first four sessions of the gesture detection experiment, while the fifth session utilized a sensorized glove. Both the volar and dorsal sides of the forearm were examined. In the object-size discrimination experiment, the method was exclusively assessed on the volar surface under four distinct feedback conditions, including all fingers and each finger separately. The psychophysical data were further analyzed using a structural equation model (SEM) to evaluate the specific contributions of each individual contactor. Subjects consistently outperformed the chance level in detecting gestures. Performance improved up to the third session, with better results obtained on the volar side. The performances were similar in the fourth and fifth sessions. The just noticeable difference for achieving a 75% discrimination accuracy was found to be 2.90 mm of movement on the skin. SEM analysis indicated that the contactor for the index finger had the lowest importance in gesture detection, while it played a more significant role in object-size discrimination. However, all fingers were found to be significant predictors of subjects' responses in both experiments, except for the thumb, which was deemed insignificant in object-size discrimination. The study highlights the importance of considering the partial contribution of each degree of freedom in a sensory feedback system, especially concerning the task, when designing such systems.

Active learning for the prediction of shape errors in milling

In machining processes, various influences, such as workpiece and tool geometry, process parameters or tool wear, can lead to decreasing part quality. Thus, predicting these influences to enable better process planning is essential. However, no general, analytical model is available to facilitate this. Data-driven approaches, on the other hand, are costly due to the required data labeling efforts. To address this, the authors present a data-driven active machine learning approach to predict shape errors based on process data enhanced by a material removal simulation. Using two representative pocket milling datasets, it is shown that this approach can yield better (up to 5 % decrease of RMSE) and more consistent (up to 85 % decrease in standard deviation of RMSE) model accuracy for a given budget of tactile probing points compared to a passive learning strategy.

A 3-D-Printed Tactile Probe Based on Fiber Bragg Grating Sensors for Noninvasive Breast Cancer Identification

A 3-D-Printed Tactile Probe Based on Fiber Bragg Grating Sensors for Noninvasive Breast Cancer Identification

Perception of facial expressions involves emotion specific somatosensory cortex activations which are shaped by alexithymia

Somatosensory cortex (SCx) has been shown to crucially contribute to early perceptual processes when judging other's emotional facial expressions. Here, we investigated the specificity of SCx activity to angry, happy, sad and neutral emotions and the role of personality factors. We assessed participants' alexithymia (TAS-20) and depression (BDI) levels, their cardioceptive abilities and recorded changes in neural activity in a facial emotion judgment task. During the task, we presented tactile probes to reveal neural activity in SCx which was then isolated from visual carry-over responses. We further obtain SCx emotion effects by subtracting SCx activity elicited by neutral emotion expressions from angry, happy, and sad expressions. We find preliminary evidence for distinct modulations of SCx activity to angry and happy expressions. Moreover, the SCx anger response was predicted by individual differences in trait alexithymia. Thus, emotion expressions of others may be distinctly presented in the observer's neural body representation and may be shaped by their personality trait.

Freeform digital twin approach to develop the HP 300 freeform verification standard

Inspired by previous experience in freeform metrology practice and industrial needs, the Czech Metrology Institute developed the freeform standard Hyperbolic paraboloid 300 of dimensions 300mm×300mm×160mm with a freeform functional area of approximately 64000mm2. The paper presents a mathematical–metrological approach to finding a suitable strategy for calibrating the freeform standard on a coordinate measuring machine with a tactile probing system. The calibration strategy consists in the development of a freeform digital twin of the standard, i.e. a continuous digital representation of a freeform measured value with associated uncertainty. A procedure to estimate the uncertainty of the coordinate freeform measurement is described, too. After calibration, the Hyperbolic paraboloid 300 standard will become a verification gauge suitable for use as a precision reference in advanced freeform metrology similar to common verification gauges widely used in length metrology.

Intrathecal non-viral interleukin-10 gene therapy ameliorates neuropathic pain as measured by both classical static allodynia and a novel supra-spinally mediated pain assay, the Two-Arm Rodent Somatosensory (TARS) task

Intrathecal delivery of interleukin-10 (IL-10) gene therapy has been reported to be effective in suppressing pain enhancement in a variety of rodent models. However, all publications that have tested this treatment have relied upon measures of static allodynia (von Frey test) and thermal hyperalgesia (Hargreaves test). As this plasmid DNA IL-10 (pDNA-IL10) therapeutic approach is now in human clinical trials for multiple pain indications, including intrathecal delivery for human neuropathic pain, it is important to consider the recent concerns raised in the pain field that such tests reflect spinal rather than supraspinal processing of, and responsivity to, noxious stimuli. Consequently, this raises the question of whether intrathecal pDNA-IL10 can reverse established neuropathic pain when assessed by a test requiring supraspinal, rather than solely spinal, mediation of the behavioral response. The present study utilizes the rat sciatic chronic constriction injury (CCI) model of neuropathic pain to compare the expression of static allodynia with that of cognitively controlled choice behavior in a two-arm maze, adapted from Hayashida et al. (2019). This modification, termed the Two-Arm Rodent Somatosensory (TARS) task, provides rats free choice to reach a desired goal box via a short “arm” of the maze with tactile probes as flooring versus a longer “arm” of the maze with a smooth surface. Here we demonstrate that static allodynia and avoidance of the nociceptive flooring in TARS develop in parallel over time, and that both behaviors also resolve in parallel following intrathecal pDNA-IL10 gene therapy. Details for the construction and use of this new maze design are also provided. Together, this study documents both: (a) the important finding that intrathecal IL-10 gene therapy does indeed resolve neuropathic pain as measured by a supraspinally-mediated behavioral task, and (b) a new, supraspinally-mediated task that allows behavioral assessments across weeks and allows the analysis of both development and resolution of neuropathic pain by therapeutic interventions. As such, the TARS operant behavior task is an improvement over other approaches such as the mechanical conflict-avoidance system which have difficulties demonstrating development and reversal of pain behavior in a within-subject design.

Nanometer precision height gauge for small holes with high aspect ratio

The demand for measuring the feature size of small holes is increasing. In this study, a nanometer precision height gauge for small holes with a high aspect ratio was developed. The height gauge comprises a Michelson interferometer, a moving and weight balance system, a tactile probing system, and a positioning control system. The errors due to the angular deflection of the moving stage were analyzed, and a corner-cube-based interferometer was designed. The structural design of the moving and weight balance systems was explored. A tactile micro/nano-probing system was developed and used. The signal processing, positioning control and measurement strategy, and software were developed. The system was calibrated and verified by testing the reference ring gauge. The experimental results show that the height gauge can achieve a resolution of 5 nm, a measurement uncertainty of 90 nm (k = 2), and a measuring range of 30 mm. The prototype can be used to measure the depth of small holes with a high aspect ratio.

Tissue Viscoelasticity Quantification Using Smartphone Tactile Imaging Probe With an Indenter and Viscoelastic Pitting Recovery Model

Viscoelasticity of human tissue often carries important physiological information linking to many fatal diseases, such as heart failure, renal impairment, and liver failure. Fluid retention due to these diseases cause swelling of body parts (edema) and changes the viscoelastic characteristic of the tissue. We hypothesize that the viscoelastic behavior change of the tissue can be estimated by creating and quantifying the pit on the swelled body parts. Here, we present a smartphone tactile imaging probe with an indenter (STIP-I) system that measures the pitting parameters and characterizes the viscoelastic behavior. This system consists of tactile imaging sensing that utilizes a light diffusion in a polydimethylsiloxane (PDMS)-based optical waveguide and a Viscoelastic Pitting Recovery (VPR) computation model. The prototype STIP-I system is tested using edematous tissue phantoms, which show a moderate measurement error of 29.5% for the pitting parameters and excellent performance of 7.60% error in elastic modulus estimation. The STIP-I system is expected to bring a new approach to understanding viscoelasticity changes due to various diseases.

Sensor for Meso-Scale Tissue Stiffness Characterization

Force sensing is fundamental for developing smart surgical devices capable of in-vivo tissue stiffness measurement. The sensing technique necessitates integration of micromachined force sensors at the end-effectors of tactile probes. We discuss fabrication and characterization of a small footprint silicon diaphragm-based force sensor with boron-doped piezoresistors connected in Wheatstone bridge configuration. The sensor performance characteristics for axial indentation experiments yield sensitivity 0.34 mV/mN, linearity > 0.99, and hysteresis 1.18% for force range 0–250 mN. To validate the utility of the force sensor for mechanical characterization of soft tissues, we perform indentation experiments on sheep tracheal tissues. The study involved two important mechanical characterization techniques: compression and stress relaxation. Tissue samples comprised of cartilage tissue from the cranial, middle, and caudal portions of the trachea and smooth muscle tissue. We record the hysteresis patterns of the tissue samples at <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$10 ~\mu \text{m}$ </tex-math></inline-formula> /s strain rate. The stiffness of cranial, middle, and caudal cartilage at 20% strain are 23±1.39 N/m,22.36±2.05 N/m, and 22.41±2.04 N/m. The cranial cartilage is innately stiffer than other tracheal segments; however, the results show no statistical variation (p ≥ 0.1488) in cartilage stiffness based on anatomical region. The stiffness of smooth muscle at 30% strain measures to be 14.02±0.76 N/m. The stress relaxation experiments reveal cartilage samples have faster relaxation time, and the smooth muscle tissues respond less rapidly to compression loads and have slower relaxation time. The feasibility of characterizing soft tissues at low contact force and small sensing area extends the utility of the sensor in airway diagnostic tools for localized stiffness measurement.

Improving template-based CT data evaluation by integrating CMM reference data into a CAD model-based high fidelity triangle mesh

One of the key characteristics of dimensional X-ray computed tomography (CT) is the possibility of complete capturing of all interfaces of the measurement object with its environment (atmosphere and clamping contact points) and itself (in case of certain multi-material conditions and pores). This property distinguishes CT from optical measurement systems (e.g. structured-light scanning), which in general lack the capability to capture the clamping surfaces without additional expenses into additional positioning and referencing measures. Therefore, CT data is in general well suited for data template-based1 measurement data evaluation (in this context also known as nominal-actual comparison) because the whole surface of the measurement object is captured it is straightforeward to identify critical surface regions. In practice (e.g. as described in [2]), a nominal-actual comparison is usually conducted by aligning the measured geometry with the nominal geometry (CAD model) of the measurement object, followed by the calculation of the local distance field. Following this approach, it is not possible to separate measurement errors introduced by the measuring system and production deviations introduced by the workpiece. Therefore, the approach is less suited for a thorough measurment system analysis. Tactile probing is well established in dimensional metrology [3] and tactile coordinate measuring systems (CMS) perform highly accurate measurements on various workpieces [4, 5]. Furthermore, the simulation of the measurement evaluates the task specific measurment uncertainty [6]. Nevertheless, only a limited number of measurment points is captured by a tactile CMS and some features might not be accessible. This contribution demonstrates a method to integrate point cloud CMM (reference measurement) data into the CAD model of a workpiece in order to create a hybrid CAD/CMM model represented by a high fidelity triangle mesh, which can be used for further evaluation [7– 9] of the local measurement uncertainty characteristics of the measurement task as well as for standard nominal-actual comparisons. Additionally, as a necessary pre-processing step, a method to transform a CAD model into a triangle mesh with user-defined sampling point density is presented, such that each triangle edge point lies exactly on the CAD model surface. This represents the prerequisite for correct nominal-actual comparisons with triangle meshes used as nominal geometry.

Prevalence of White Spot Caries Lesions in Primary Teeth in Preschool Children: Systematic Review and Meta-analysis.

The first clinically detectable stage of caries lesion is a non-cavitated white spot lesion (WSL). The detection of early stages of caries lesions allows non-invasive management by fluoride usage, oral hygiene and diet control. There is a lack of information in the literature regarding the prevalence of these caries lesions in preschool children, which is important especially for public health strategies. The aim of this study was to conduct a systematic review with meta-analysis to verify the WSLs prevalence in primary teeth of preschool children. A literature search with MEDLINE/PubMed, Scopus, Web of Science, and Open Gray databases was conducted. Included studies fulfilled the eligibility criteria. Meta-analyses were performed using random effects model, for prevalence of pooled WSLs and subgroups analyses. The search strategy identified 4922 potentially relevant articles, with final inclusion of 16 studies. The pooled prevalence of WSLs in primary teeth was 14.0% (95% CI: 8.0-24.0), without publication bias (p=0.2668). For subgroup analyses, an increase in WSLs prevalence for children of low-income economy (24.0%; 95% CI: 20.0-28.0), for age >31 months (22.0%; 95% CI: 12.0-37.0), for validated visual criteria assessment (20.0%; 95% CI: 11.0-33.0), and for tactile assessment with ball-ended probe (26.0%; 95% CI: 11-50.0) were detected. It is suggested that the prevalence of WSLs in primary teeth of preschool children increases in countries with low income economy, with age greater than 31 months or texture assessment with visual validated criteria or ball-ended probe. PROSPERO Registration: Protocol number #CDR42017078434.

Tactile needle probe for minimally invasive tissue identification during epidural space insertion

This paper presents a novel optical fiber-based needle probe designed to measure the tactile force at needle tip during needle insertions. By fusing the measurements along inserting paths, the probe can provide visualized tissue layer breaking information such as cutting force and layer thickness within the internal organ structure. The sensing system then can confirm types of tissue and localize needle tip by analyzing force feedback signal. The performance of the developed probe was validated via insertions on various bio tissues. Experimental results show that the sensing needle can provide reliable force information and estimation of the tissue types.

Analysis of total rotor runout components with multi-probe roundness measurement method

Several standards for vibration testing of rotating machinery define limits for relative shaft displacement during rotation. With requirements for relative shaft displacement, limits are given for combined electrical and mechanical runout, which is the eddy probe reading error and the error caused by geometry of the measured shaft. Some standards allow for compensation of the mechanical and electrical runout by vectorially subtracting them from the eddy current probe values.This paper presents a measurement procedure applying multi-probe error separation to accurately determine the roundness profile and center point motion of electric motor shafts. The roundness error and center point movement obtained from multi-probe measurement with tactile displacement probes are compared with eddy current sensor displacement measurements to separate the total displacement measured with an eddy current probe into three components: center point motion, roundness error and electrical runout. Additionally, a transform for the measured eccentric component is presented to obtain an estimate for permanent rotor bow regardless of the rotor support arrangement during measurement.The relevant industrial vibration testing standards were reviewed. Several issues were found in the measurement methods required by the standards. The requirements of the standards and the used terminology are assessed critically and improvement proposals are presented.

Dimensional metrology of additively manufactured lattice structures by combined tactile probe and X‐ray tomography

Dimensional metrology of additively manufactured lattice structures by combined tactile probe and X‐ray tomography

COMPLEX-SHAPED PARTS GRINDING TECHNOLOGY INFORMATION ENSURING

A method of computer-aided design and manufacture of complex-shaped parts of machines and implants from difficult-to-machine materials (titanium, cobalt-chromium alloys, zirconium dioxide, etc.) has been developed, based on the principles of building an integrated CAD/CAM/CAE system of computer-aided designing and a hierarchical intelligent numerical control system. It is shown that kinematical mechanisms created over the past several centuries do not allow reproducing with the required accuracy the joints movement of living organisms for their use in biomedical implantation technologies. Therefore, the worn out joints of living organisms are reconstructed by adding complex-shaped parts from these difficult-to-machine materials. Information about the geometric shape of these parts (3D model) at the pre-production stage is obtained using modern methods of computed tomography and magnetic resonance imaging, and at the production stage the actual location of the stock grinding allowance is measured by laser (or tactile) scanning. To reduce the unevenness of the position of the grinding stock allowance, the workpiece of a complex-shaped part before grinding is oriented in the coordinate system of a CNC machine based on the established criterion for minimizing the allowance. An example of such orientation of the gear workpiece is given. This workpiece is measured with a Renishaw tactile probe on the left and right sides of the gear valleys before gear grinding. Both the minimum allowance on the left and right sides of the valleys and the difference between them are determined, and then additionally the gear wheel blank is rotated in the appropriate direction to align these minimum values detected. In turn, the aligned minimum allowances, should be sufficient to compensate for the influence of technological factors from the previous operation and the error in setting the workpiece for this operation. For complex-shaped implants, such an additional orientation is performed, for example, according to algorithms for ensuring the minimax value of the allowance.

Letter: The Risk of COVID-19 Infection During Neurosurgical Procedures: A Review of Severe Acute Respiratory Distress Syndrome Coronavirus 2 (SARS-CoV-2) Modes of Transmission and Proposed Neurosurgery-Specific Measures for Mitigation.

Letter: The Risk of COVID-19 Infection During Neurosurgical Procedures: A Review of Severe Acute Respiratory Distress Syndrome Coronavirus 2 (SARS-CoV-2) Modes of Transmission and Proposed Neurosurgery-Specific Measures for Mitigation.

Multi-sensor registration method based on a composite standard artefact

Registration is a critical and essential procedure in any multi-sensor dimensional measuring systems. Most of the traditional registration methods are achieved by measuring a common standard by multiple sensors; however, it is difficult to ensure that heterogeneous sensors measure the same feature points. In this study, a new multi-sensor registration method based on a composite standard artefact is proposed. The base of the standard artefact is equipped with a standard sphere and a standard chrome-circle for registering the visual sensor (VS) and the tactile probe sensor (TPS) on a multi-sensor dimensional measuring machine. The VS and TPS measure the standard chrome-circle and the standard sphere, respectively. The coordinate system conversion parameters between the two sensors were solved based on the constant distance between the standard chrome-circle centre and the standard sphere centre. Both the simulations and experiments demonstrate higher precision and stability of the proposed method for the registration of multiple heterogeneous sensors in high-precision dimensional measurement systems. The root mean square errors of the registration experiments in X and Y -directions are 6μm and 4μm, respectively. The combined standard uncertainties are uc(tx)=1.6μm and uc(ty)=1.2μm.