8,948 research outputs found
Walker-Assisted Gait in Rehabilitation: A Study of Biomechanics and Instrumentation
While walkers are commonly prescribed to improve patient stability and ambulatory ability, quantitative study of the biomechanical and functional requirements for effective walker use is limited. To date no one has addressed the changes in upper extremity kinetics that occur with the use of a standard walker, which was the objective of this study. A strain gauge-based walker instrumentation system was developed for the six degree-of-freedom measurement of resultant subject hand loads. The walker dynamometer was integrated with an upper extremity biomechanical model. Preliminary system data were collected for seven healthy, right-handed young adults following informed consent. Bilateral upper extremity kinematic data were acquired with a six camera Vicon motion analysis system using a Micro-VAX workstation. Internal joint moments at the wrist, elbow, and shoulder were determined in the three clinical planes using the inverse dynamics method. The walker dynamometer system allowed characterization of upper extremity loading demands. Significantly differing upper extremity loading patterns were Identified for three walker usage methods. Complete description of upper extremity kinetics and kinematics during walker-assisted gait may provide insight into walker design parameters and rehabilitative strategies
Application of a portable FTIR for measuring on-road emissions
The objective of this work was the development of an onroad
in-vehicle emissions measurement technique
utilizing a relatively new, commercial, portable Fourier
Transform Infra-Red (FTIR) Spectrometer capable of
identifying and measuring (at approximately 3 second
intervals) up to 51 different compounds. The FTIR was
installed in a medium class EURO1 spark ignition
passenger vehicle in order to measure on-road
emissions. The vehicle was also instrumented to allow
the logging of engine speed, road speed, global position,
throttle position, air-fuel ratio, air flow and fuel flow in
addition to engine, exhaust and catalyst temperatures.
This instrumentation allowed the calculation of massbased
emissions from the volume-based concentrations
measured by the FTIR. To validate the FTIR data, the
instrument was used to measure emissions from an
engine subjected to a real-world drive cycle using an AC
dynamometer. Standard analyzers were operated
simultaneously for comparison with the FTIR and the
standard analyzer results showed that most pollutants
(NOx, CO2, CO) were within ~10% of a standard analyzer
during steady state conditions and within 20% during
transients. The exception to this was total HC which was
generally 50% or less than actual total HC, but this was
due to the limited number of hydrocarbons measured by
the FTIR. In addition to the regulated emissions, five
toxic hydrocarbon species were analyzed and found to
be sensitive to cold starts in varying proportions. Finally,
FTIR data was compared to results from a commercially
available on-road measurement system (Horiba OBS-
1000), and there was good agreement
Analysis of knee strength measurements performed by a hand-held multicomponent dynamometer and optoelectronic system
The quantification of muscle weakness is useful to evaluate the health status and performance of patients and athletes. In this paper, we proposed a novel methodology to investigate and to quantify the effects induced by inaccuracy sources occurring when using a hand-held dynamometer (HHD) for knee strength measurements. The validation methodology is based on the comparison between the output of a one-component commercial HHD and the outputs of a six-component load cell, comparable in dimension and mass. An optoelectronic system was used to measure HHD positioning angles and displacements. The setup allowed to investigate the effects induced by: 1) the operator's ability to place and to hold still the HHD and 2) ignoring the transversal components of the force exchanged. The main finding was that the use of a single component HHD induced an overall inaccuracy of 5% in the strength measurements if the angular misplacements are kept within the values found in this paper (≤15°) and with a knee range of motion ≤22°. Extension trials were the most critical due to the higher force exerted, i.e., 249.4 ± 27.3 versus 146.4 ± 23.9 N of knee flexion. The most relevant source of inaccuracy was identified in the angular displacement on the horizontal plane
Axial force and efficiency tests of fixed center variable speed belt drive
An investigation of how the axial force varies with the centerline force at different speed ratios, speeds, and loads, and how the drive's transmission efficiency is affected by these related forces is described. The tests, intended to provide a preliminary performance and controls characterization for a variable speed belt drive continuously variable transmission (CVT), consisted of the design and construction of an experimental test rig geometrically similar to the CVT, and operation of that rig at selected speed ratios and power levels. Data are presented which show: how axial forces exerted on the driver and driven sheaves vary with the centerline force at constant values of speed ratio, speed, and output power; how the transmission efficiency varies with centerline force and how it is also a function of the V belt coefficient; and the axial forces on both sheaves as normalized functions of the traction coefficient
Calculating the interior permanent-magnet motor
This paper describes the calculation of torque in a brushless permanent-magnet line-start AC motor by means of the flux-MMF diagram in combination with the finite-element method. Results are compared with measured flux-MMF diagrams, with shaft torque measurements, and with torque calculated using the classical phasor diagram
The detection of gear noise computed by integrating the Fourier and Wavelet methods
This paper presents a new gearbox noise detection algorithm based on analyzing specific points
of vibration signals using the Wavelet Transform. The proposed algorithm is compared with a previouslydeveloped
algorithm associated with the Fourier decomposition using Hanning windowing. Simulation
carried on real data demonstrate that the WT algorithm achieves a comparable accuracy while having a lower
computational cost. This makes the WT algorithm an appropriate candidate for fast processing of noise gear box
Kinesimetric method and apparatus
Apparatus and method for the determination of functional capability of bodies are disclosed. Reach as well as velocity, acceleration and force generation at various positions may be determined for a body by a three dimensional kinesimeter equipped with an ergometer. A general data package indicative of performance potential of a subject body or collection of bodies is provided for interfacing with data characteristics of various environments
Forces on Centrifugal Pump Impellers
Forces are exerted on a centrifugal pump impeller, due to the asymmetry of the flow caused by the volute of diffuser, and to the motion of the center of the impeller whenever the shaft whirls. Recent work in the measurement of these forces as a function of the whirl speed to shaft speed ratio, and the influence of the volute, is reviewed. These forces may be decomposed into a steady force, a static stiffness matrix, a damping matrix and an inertia matrix. It is shown that for centrifugal pumps of the moderate specific speed typical of boiler feed stages, there is a region of potential shaft vibration excitation from the hydrodynamic forces if the operating speed is well above the first flexural critical speed
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