Estimation Of Contact Pressure Research Articles

Pressure eye: In-bed contact pressure estimation via contact-less imaging.

Computer vision has achieved great success in interpreting semantic meanings from images, yet estimating underlying (non-visual) physical properties of an object is often limited to their bulk values rather than reconstructing a dense map. In this work, we present our pressure eye (PEye) approach to estimate contact pressure between a human body and the surface she is lying on with high resolution from vision signals directly. PEye approach could ultimately enable the prediction and early detection of pressure ulcers in bed-bound patients, that currently depends on the use of expensive pressure mats. Our PEye network is configured in a dual encoding shared decoding form to fuse visual cues and some relevant physical parameters in order to reconstruct high resolution pressure maps (PMs). We also present a pixel-wise resampling approach based on Naive Bayes assumption to further enhance the PM regression performance. A percentage of correct sensing (PCS) tailored for sensing estimation accuracy evaluation is also proposed which provides another perspective for performance evaluation under varying error tolerances. We tested our approach via a series of extensive experiments using multimodal sensing technologies to collect data from 102 subjects while lying on a bed. The individual's high resolution contact pressure data could be estimated from their RGB or long wavelength infrared (LWIR) images with 91.8% and 91.2% estimation accuracies in PCSefs0.1 criteria, superior to state-of-the-art methods in the related image regression/translation tasks.

Estimation of contact pressure in machine focusing on instantaneous frequency and phase of ultrasonic pulse.

Estimation of contact pressure in machine focusing on instantaneous frequency and phase of ultrasonic pulse.

An extended discrete element method for the estimation of contact pressure at the ankle joint during stance phase.

Abnormalities in the ankle contact pressure are related to the onset of osteoarthritis. In vivo measurements are not possible with currently available techniques, so computational methods such as the finite element analysis (FEA) are often used instead. The discrete element method (DEM), a computationally efficient alternative to time-consuming FEA, has also been used to predict the joint contact pressure. It describes the articular cartilage as a bed of independent springs, assuming a linearly elastic behaviour and absence of relative motion between the bones. In this study, we present the extended DEM (EDEM) which is able to track the motion of talus over time. The method was used, with input data from a subject-specific musculoskeletal model, to predict the contact pressure in the ankle joint during gait. Results from EDEM were also compared with outputs from conventional DEM. Predicted values of contact area were larger in EDEM than they were in DEM (4.67 and 4.18 cm2, respectively). Peak values of contact pressure, attained at the toe-off, were 7.3 MPa for EDEM and 6.92 MPa for DEM. Values predicted from EDEM fell well within the ranges reported in the literature. Overall, the motion of the talus had more effect on the extension and shape of the pressure distribution than it had on the magnitude of the pressure. The results indicated that EDEM is a valid methodology for the prediction of ankle contact pressure during daily activities.

Intraoperative computer-assisted prediction of intraarticular contact pressures in the knee during high tibial osteotomy.

To develop an accurate intraoperative method to estimate changes in intraarticular contact pressures during high tibial osteotomy (HTO). Changes in knee alignment and pressure were monitored in real time in seven cadaver specimens that received HTO. Intraarticular contact pressure (N/mm2 ) in each knee compartment was estimated based on extraarticularly acquired data (leg alignment, correction, and ankle tilt) and based on the application of an axial force of half bodyweight (400-450N). Contact pressure estimation was more accurate in the lateral compartment (R2 =0.940) than in the medial compartment of the knee (R2 =0.835). The optimism-corrected R2 was 0.936 for the lateral compartment and 0.821 for the medial compartment. We have established a framework for estimating the change in intraarticular contact pressures based on extraarticular data. This research could be helpful in generating appropriate algorithms to estimate joint alignment changes based on applied loads.

Estimation of contact pressure between mechanical parts focusing on instantaneous frequency of ultrasonic pulse

Estimation of contact pressure between mechanical parts focusing on instantaneous frequency of ultrasonic pulse

ガーリン理論に基づく接触モデルによる人工関節用材料間の接触面圧推定

ガーリン理論に基づく接触モデルによる人工関節用材料間の接触面圧推定

A real-time topography of maximum contact pressure distribution at medial tibiofemoral knee implant during gait: Application to knee rehabilitation

Knee contact pressure is a crucial factor in the knee rehabilitation programs. Although contact pressure can be estimated using finite element analysis, this approach is generally time-consuming and does not satisfy the real-time requirements of a clinical set-up. Therefore, a real-time surrogate method to estimate the contact pressure would be advantageous.This study implemented a novel computational framework using wavelet time delay neural network (WTDNN) to provide a real-time estimation of contact pressure at the medial tibiofemoral interface of a knee implant. For a number of experimental gait trials, joint kinematics/kinetics and the resultant contact pressure were computed through multi-body dynamic and explicit finite element analyses to establish a training database for the proposed WTDNN. The trained network was then tested by predicting the maximum contact pressure at the medial tibiofemoral knee implant for two different knee rehabilitation patterns; “medial thrust” and “trunk sway”. WTDNN predictions were compared against the calculations from an explicit finite element analysis (gold standard).Results showed that the proposed WTDNN could accurately calculate the maximum contact pressure at the medial tibiofemoral knee implant for medial thrust (RMSE¯=1.7MPa, NRMSE¯=6.2% and ρ¯=0.98) and trunk sway (RMSE¯=2.6MPa, NRMSE¯=9.3%, ρ¯=0.96) much faster than the finite element method. The proposed methodology could therefore serve as a cost-effective surrogate model to provide real-time evaluation of the gait retraining programs in terms of the resultant maximum contact pressures.

Evaluation of contact pressure in human vocal folds during phonation using high-speed videoendoscopy, electroglottography, and magnetic resonance imaging

Mechanical stresses on the vocal folds surface during high pitch or amplitude phonation have been postulated to cause vocal fold damage. Models for the quantitative estimate of the contact pressure may be valuable for prevention and treatment. The objective of this study was to non-invasively estimate the contact pressure for different phonation types, amplitudes, and pitch in human subjects using concurrent high-speed videoendoscopy and eletroglottography. The edge velocities before and after contact were estimated from the analysis of consecutive digital images. Instantaneous contact areas were determined from electroglottography along with magnetic resonance image (MRI). The contact pressure was assessed using the impulse momentum form of Newton’s second law. Quantitative verifications using silicone models were made. Investigations were then carried out in quantitative human subjects to compare contact pressures for three different voice types, pitches, and loudnesses. Contact pressures for breathy, normal, and pressed voice were obtained for fifteen female subjects. The results were verified through comparisons with values measured directly using a probe microphone. The proposed methods appear to be robust and accurate for contact pressure estimation.

Optical measurement for the estimation of contact pressure and stress

This paper presents experiments based on optical measurements which allowed characterising the elastic strains and stresses induced by a real contact between two parts. For that purpose, a disc of polymethyl methacrylate (PMMA) was indented by a rigid steel punch. Using the transparency of the material, the displacement field of the contact surface was measured, across the thickness of the sample, using a chromatic confocal sensor. Boussinesq's potential theory was then applied to this data in order to evaluate the true pressure of the contact. It allowed also estimating the strains and stresses at any point of the indented sample.

106 コンプレッションスポーツウェアの圧力予測に関する実験的研究(運動計測(2))

106 コンプレッションスポーツウェアの圧力予測に関する実験的研究(運動計測(2))

Estimation of the contact pressure on the medial surface of the vocal folds during phonation.

Voice production involves flow‐induced self‐oscillations of the vocal folds. Collision between the vocal folds is commonly observed during normal phonation. The contact pressure experienced by human vocal folds during collision is usually considered as the most likely source of phonotrauma. The goal of the present study was to quantify contact pressures in human subjects during phonation. A pressure sensor was developed for direct measurements. Verification data and preliminary data on human subjects were obtained. Subject response and other clinical challenges lead to the development of a less intrusive approach for the contact pressure estimation from high speed images based on a Hertzian impact model. A verification of the accuracy of this approach was made. Results from the nonintrusive approach were compared with results from direct measurements using a hemilaryngeal physical model of the human vocal folds. The experimental setup was designed to reduce sensor’s interference with the vocal fold oscillations. The accuracy of the estimated contact pressure from the nonintrusive method was found to be within around 10%. Advantages and possible sources of error are discussed. [Work supported by NIH.]

535 PS型人工膝関節における回旋時のポスト/カム間の接触圧力評価(S09-1 関節のバイオメカニズム(1),S09 関節のバイオメカニズム)

535 PS型人工膝関節における回旋時のポスト/カム間の接触圧力評価(S09-1 関節のバイオメカニズム(1),S09 関節のバイオメカニズム)

Normal hip joint contact pressure distribution in single-leg standing—effect of gender and anatomic parameters

A practical and easy-to-use analysis technique that can study the patient's hip joint contact force/pressure distribution would be useful to assess the effect of abnormal biomechanical conditions and anatomical deformities on joint contact stress for treatment planning purpose. This technique can also help to establish the normative database on hip joint contact pressure distribution in men and women in different age groups. Twelve anatomic parameters and seven biomechanical parameters of the hip joint in a normal population (41 females, 15 males) were calculated. The inter-parameter correlations were investigated. The pressure distribution in the hip joint was calculated using a three-dimensional discrete element analysis (DEA) technique. The 3D contact geometry of the hip joint was estimated from a 2D radiograph by assuming that the femoral head and the acetabular surface were spherical in shape. The head–trochanter ratio (HT), femoral head radius, pelvic height, the joint contact area, the normalized peak contact pressure, abductor force, and the joint contact force were significantly different between men and women. The normalized peak contact pressure was correlated both with acetabular coverage and head–trochanter ratio. Change of abductor force direction within normal variation did not affect the joint peak contact pressure. However, in simulated dysplastic conditions when the CE angle is small or negative, abductor muscle direction becomes very sensitive in joint contact pressure estimation. The models and the results presented can be used as the reference base in computer simulation for preoperative planning in pelvic or femoral osteotomy.

Estimation of Contact Pressure between Bearing and Bearing Housing by Means of Ultrasonic Waves.

When measuring the contact pressure of the joint, it is suggested that a method using ultrasonic waves has a marked feature, i.e., continuous applicability to the sliding or rotating joint without changing the state of contact. This paper reports a newly proposed parameter for the evaluation of contact pressure of cylindrical joint for spindle system of machine tools. Wavelet transform shows a noteworthy effect to extract the characteristics of joint. From the experimental results, the relationship between the radial run-off of spindle and the contact pressure of the joint in working condition has been discussed.