scholarly journals The testing of plane surfaces

1912 ◽  
Vol 86 (586) ◽  
pp. 227-234
Keyword(s):  
Degree Of Freedom ◽  
Small Areas ◽  
Know How ◽  
Standard Measuring ◽  
Contact Points ◽  
Trade Practice ◽  
Standard Plate ◽  
Accuracy Of Measurement ◽  
Measuring Machine

There is only one way of originating a true plane, viz., to make it in triplicate and to work all three surfaces so as to obtain a "fit" between them. In engineering trade practice this is done when a standard plate is required, and any one of the three plates thus obtained can be used as being truly plane (within the limits of the "raddle" process) for the making of further surface-plates. In many modern exact apparatus, e. g. , a standard measuring machine or a Michelson's interferometer, accuracy of measurement directly depends on the truth of the plane "ways" of the bed along which the various parts of the apparatus slide. These ways are made either by scraping or lapping, and it is of importance to know what errors occur from place to place along the bed due to defective workmanship. The bed generally has three worked planes all inclined to one another, and the movable parts rest on these by, five contact points, thus allowing only one degree of freedom. These five feet bear on the surfaces below by small areas, and amongst other considerations it is important to know how far these feet rise and fall in and out of the scraping marks if the surfaces have been made by scraping.

scholarly journals A standard measuring machine

1912 ◽  
Vol 87 (597) ◽  
pp. 385-390
Keyword(s):  
National Physical Laboratory ◽  
Standard Measuring ◽  
Physical Laboratory ◽  
Accurate Comparison ◽  
Measuring Machine ◽  
Regular Work ◽  
Absolute Measurements ◽  
Line Standard

In some physical researches it is required to measure the dimensions of a regular solid, whether parallel-sided, cylindrical, or spherical-ended, with the greatest possible accuracy. Again, in the regular work of a metrology bureau, accurate comparison of the size of an end-standard of length with reference to a line-standard is required. Until 1906 the only apparatus available for these purposes was the measuring machine made for comparing engineering gauges. In that year the writer described a machine based on the principle of electric touch, which was much more delicate than the older mechanical machines. It also had facilities for exploring the solid under test, to prove its accuracy of figure. This machine has been installed and used in the National Physical Laboratory since 1909. Improvements in it were described later. The present paper gives an outline of an improved machine of the same type embodying the experience gained in using the 1906 machine. The chief novelties are: (1) greater strength in the supporting parts, and consequent rigidity of the whole apparatus; (2) larger and much improved table to carry the solid under test; (3) improved measuring-ends; (4) an innovation for making absolute measurements, whereby the line-standard moves but the reading microscope remains fixed; (5) side girders to relieve the bed of load and so reduce friction, abrasion, and strain.

Accuracy of Orthodontic Force and Tooth Movement Measurements

1996 ◽  
Vol 23 (3) ◽  
pp. 241-248 ◽  
Author(s):  
Dan Lundgren ◽  
Py Owman-Moll ◽  
Jüri Kurol ◽  
Birgit Mårtensson
Keyword(s):  
Tooth Movement ◽  
Mean Value ◽  
Measurement Methods ◽  
Calibration Data ◽  
Force Measurements ◽  
Accuracy Of Measurement ◽  
Measuring Machine ◽  
Initial Force ◽  
Level Of Agreement

This study was designed to test the accuracy of measurement methods for assessment of force and tooth movement in orthodontic procedures. Daily in vivo measurements of the force produced by activated archwires showed that the initial force declined substantially (by 20 per cent of mean value) within 3 days. Both the ‘trueness’ (validity) and precision of the force measurements, obtained with a strain gauge, were found to be high (SD values were 1·0 cN and 0·4 cN, respectively). Horizontal tooth movements were measured with three different instruments: a slide calliper, a co-ordinate measuring machine, and laser measuring equipment based on holograms. There was a good level of agreement between these methods. This was also confirmed by calibration data. The precision of the methods was (SD values) 0·06, 0·07, and 0·13 mm, respectively. The benefits of the use of the co-ordinate measuring machine are obvious, since it can measure tooth movements in relation to reference planes in all directions.

Knee Joint Response to Compressive Loading and Ligament Injury

1999 ◽  
Author(s):  
Jordan Lee ◽  
Frank Fronczak
Keyword(s):  
Knee Joint ◽  
Cruciate Ligament ◽  
Compressive Loading ◽  
Degree Of Freedom ◽  
Ligament Injury ◽  
Ligament Injuries ◽  
Acl Injuries ◽  
Measuring Machine ◽  
Anterior Cruciate ◽  
Six Degree Of Freedom

Abstract The knee joint is a six degree-of-freedom joint which has a complex response to loading. The joint has a characteristic behavior for particular ligament injuries such as anterior cruciate ligament failure. The response of the joint to a combination of compressive loading and secondary loadings was examined in this study. The secondary loadings were: an anterior force, a valgus moment, an internal torque, or an external torque. A goat model was used with 17 specimens testing different ligament injuries in vitro, specifically stretched or severed anterior cruciate ligaments (ACL) and lateral collateral ligaments (LCL). The femur was held fixed and the tibia loaded in a specially designed apparatus, allowing complete six degree-of-freedom joint motion. The motion of the tibia with respect to the femur was recorded using a coordinate measuring machine. The knee joint demonstrated sensitivity to ACL injuries but not to LCL injuries for the loadings examined. The response to ACL injuries was more highly dependant on the compressive load than the secondary loadings for all tests.

Study on the Method of Error Identification and Compensation for Gear Measuring Center

2012 ◽  
Vol 482-484 ◽  
pp. 1821-1828
Author(s):  
Peng Wan ◽  
Jun Jie Guo ◽  
Hai Tao Li
Keyword(s):  
High Precision ◽  
Error Detection ◽  
Geometric Error ◽  
Precision Measurements ◽  
Tooth Surface ◽  
Geometric Errors ◽  
Detection Technology ◽  
Accuracy Of Measurement ◽  
Measuring Machine ◽  
Multi Body

Gear Measuring Center(GMC) is commonly used to test error of the tooth surface of the gear, whose geometric accuracy directly impacts on the accuracy of measurement. How to quickly and accurately detect space geometric error of the measuring machine and compensate becomes the essential means of high-precision measurements. According to the problem above, in the paper, three-beams laser detection technology is proposed. The detection of the geometric errors of the linear axis was achieved. The accurate measurement for the position and attitude of the plane mirror on measurement seat was achieved based on laser telemetry principle. The positioning error, the pitching angle errors, the deflection angle errors and the straightness errors were separated. And then based on multi-body system theory, by using of homogeneous coordinate transformation, the error compensation model of 4-axis measuring machine which includes three shifting pairs and one revolute pair was established, and the algorithm was given in the paper. The theoretical foundation for real-time compensation of 4-axis GMC was established. The geometric errors of GMC can be improved by the method of the error detection and compensation. The method plays a very important role in high-precision measurements.

A 5-5 One-Degree-of-Freedom Fully Parallel Mechanism for the Modeling of Passive Motion at the Human Ankle Joint

2007 ◽  
Author(s):  
R. Franci ◽  
V. Parenti-Castelli
Keyword(s):  
Ankle Joint ◽  
Parallel Mechanism ◽  
Degree Of Freedom ◽  
Anatomical Structures ◽  
Passive Motion ◽  
Three Sphere ◽  
Contact Points ◽  
Human Ankle ◽  
Sphere Contact ◽  
Ankle Complex

This paper presents a new equivalent spatial mechanism for the passive motion simulation at the human ankle complex joint. The mechanism is based on the geometry of the main anatomical structures of the ankle complex, such as the shape of the talus and tibio/fibula bones at their interface, and the TiCal and CaFil ligament lengths. In particular, three sphere-to-sphere contact points at the interface have been identified and isometric fibers of both TiCal and CaFil ligaments have been considered to devise the equivalent mechanism. The proposed mechanism is a fully-parallel mechanism of type 5-5 with one degree of freedom. A procedure for the optimal synthesis of the mechanism is given. Simulation results compared with experimental data show the efficiency of the proposed mechanism to replicate the ankle passive motion, and also to reflect at the same time the main anatomical structures of the ankle joint. The new mechanism is believed to be a useful tool for both pre-operation planning and prosthesis design.

scholarly journals Six-degree-of-freedom pose estimation with µm/µrad accuracy based on laser multilateration

2021 ◽  
Vol 10 (1) ◽  
pp. 19-24
Author(s):  
Jan Nitsche ◽  
Matthias Franke ◽  
Nils Haverkamp ◽  
Daniel Heißelmann
Keyword(s):  
Pose Estimation ◽  
Coordinate Measuring Machine ◽  
Degree Of Freedom ◽  
End Effector ◽  
Data Rates ◽  
Measurement Principle ◽  
Measuring Machine ◽  
Position And Orientation ◽  
Six Degree Of Freedom ◽  
Adequate Measurement

Abstract. The estimation of the six-degree-of-freedom position and orientation of an end effector is of high interest in industrial robotics. High precision and data rates are important requirements when choosing an adequate measurement system. In this work, a six-degree-of-freedom pose estimation setup based on laser multilateration is described together with the measurement principle and self-calibration strategies used in this setup. In an experimental setup, data rates of 200 Hz are achieved. During movement, deviations from a reference coordinate measuring machine of 20 µm are observed. During standstill, the deviations are reduced to 5 µm.

Development of a two-degree-of-freedom piezoelectric motor using single plate vibrator

2011 ◽  
Vol 226 (4) ◽  
pp. 1036-1052 ◽  
Author(s):  
G-M Cheng ◽  
K Guo ◽  
P Zeng ◽  
Y-M Sun
Keyword(s):  
Numerical Models ◽  
Excitation Frequency ◽  
Degree Of Freedom ◽  
Analytical Models ◽  
Experimental Result ◽  
Piezoelectric Motor ◽  
Piezoelectric Vibrator ◽  
Contact Points ◽  
Numerical Result ◽  
Two Degree Of Freedom

A two-degree-of-freedom piezoelectric motor using only one piezoelectric ceramic was proposed based on two vibration modes (B32 and B23) of a rectangular plate piezoelectric vibrator. The working principle was elaborated. Analytical and numerical models were established in order to design the piezoelectric vibrator. Calculations with finite element method were carried out using ANSYS software to validate the analytical models and demonstrate the elliptical trajectory of the four contact points between the stator and the sphere. Experimental result on the prototype shows that the numerical result including resonance frequency and elliptical motion of the motor indicate good agreement with the experimental one. The rotation speed around an axial along the direction of length of the rectangular piezoelectric vibrator of the motor is 37.7 r/min under the drive voltage 90 V and excitation frequency 44 kHz.

Sign in / Sign up

Export Citation Format

Share Document