Nominal Tolerance Research Articles

Design and Analysis of Receiver Coils with Multiple In-Series Windings for Inductive Eddy Current Angle Position Sensors Based on Coupling of Coils on Printed Circuit Boards.

We present a method for improving the amplitude and angular error of inductive position sensors, by advancing the design of receiver coil systems with multiple windings on two layers of a printed circuit board. Multiple phase-shifted windings are connected in series, resulting in an increased amplitude of the induced voltage while decreasing the angular error of the sensor. The amplitude increase for a specific number of windings can be predicted in closed form. Windings are placed electrically in series by means of a differential connection structure, without adversely affecting the signal quality while requiring a minimal amount of space in the layout. Further, we introduce a receiver coil centerline function which specifically enables dense, space-constrained designs. It allows for maximization of the number of possible coil windings while minimizing the impact on angular error. This compromise can be fine-tuned freely with a shape parameter. The application to a typical rotary encoder design for motor control applications with five periods is presented as an example and analyzed in detail by 3D finite-element simulation of 18 different variants, varying both the number of windings and the type of centerline functions. The best peak-to-peak angular error achieved in the examples is smaller than 0.1° electrically (0.02° mechanically, periodicity 5) under nominal tolerance conditions, in addition to an amplitude increase of more than 170% compared to a conventional design which exhibits more than twice the angular error. Amplitude gains of more than 270% are achieved at the expense of increased angular error.

Evaluating the Accuracy of the Reverse Engineering Process of Worn, Non-Standard Spur Gears—Pilot Studies

For years, gears have been self-made by many industrial plants as substitutes (custom spare parts) for original parts from the manufacturer. This common practice uses a process called reverse engineering (RE). However, in the available scientific database, it is difficult to find articles about the accuracy of such a process. And while it is obvious that in order to obtain the most accurate quality of such a process, modern measurement techniques (coordinate, optical) should be used, most companies cannot afford to purchase such equipment. Reproducing gear geometry is difficult. But the issue of RE of non-standard gears seems to be even more difficult. This is why the authors undertook pilot studies to assess the accuracy of the RE process of worn, non-standard spur gears using conventional techniques and measuring instruments. Eight gears were tested, the module of which ranges from 1.020 to 4.98 mm. The key parameter was selected to estimate the accuracy of the process—the base pitch. The goal is to determine the value of the profile angle. Eleven models were proposed to estimate the nominal tolerance field, using various types of random data distribution. The tested gears were made in IT grade: 6, 7, 8, and 9 according to DIN 3961. Vernier disk micrometers were used for research. It has been shown that the nominal module does not have to be treated as a random variable in the population. Equation of identity was developed, allowing conversion of any gear with specific values of geometric parameters into an identical gear with alternative values of these parameters. The most effective estimating model was selected taking into account the symmetric Student–Fisher distribution with a confidence level of 60%. However, it is not possible to correctly reproduce the geometry of the gear wheel in that way. The following aspects should be taken into account: type and degree of mode of failure, number of load cycles, rotational speed, direction of rotation, material, type of thermochemical treatment, and torque. A simulation using FEM should be performed to determine the fatigue plastic deformations and diagnose their impact on the geometric dimensions of the gear wheel.

Spiral Structured Photonic Crystal Fiber-Based Plasmonic Sensor with Bimetallic Coating

We present a bimetallic coated, low-loss spiral lattice PCF sensor combined with SPR technology that achieves a high sensitivity. The sensing performance and properties of our recommended sensor are realized numerically by the Finite Element Method. Gold is utilized as the plasmonic layer and titanium Oxide (TiO2), which is sandwiched between the silica glass fiber and the gold coating, forming the bimetallic surface. As TiO2 has a high refractive index, they create a strong surface plasmon wave in the plasmonic region that attracts the evanescent field originating from the core region and increases the coupling effect plasmonic and core mode. Hence, the bimetallic coating is performed to achieve better sensing performance and strengthen the SPR process for the presented sensor. The presented sensor’s nominal tolerance is 12,000 nm/RIU for x-polarization to 11,000 MHz for y-polarization. The presented sensor is intended to be used in several applications and sensing fields due to its high sensitivity.

A machine vision algorithm for quality control inspection of gears

Quality control has become a priority in the inspection processes of industrial manufacturing of gears. Due to the advancement of technology and the realizations of Industry 4.0, smart factories demand high precision and accuracy in the measurements and inspection of industrial gears. Machine vision technology provides image-based inspection and analysis for such demanding applications. With the use of software, sensors, cameras, and robot guidance, such integrated systems can be realized. The aim of this paper is to deploy an improved machine vision application to determine the precise measurement of industrial gears, at subpixel level, with the potential to improve quality control, reduce downtime, and optimize the inspection process. A machine vision application (Vision2D) has been developed to acquire and analyze captured images to implement the process of measurement and inspection. Firstly, a very minimum calibration error of 0.06 pixel was obtained after calibration. The calibrated vision system was verified by measuring a ground-truth sample gear in a Coordinate Measuring Machine (CMM), using the parameter generated as the nominal value of the outer diameter. A methodical study of the global uncertainty associated with the process is carried out in order to know better the admissible zone for accepting gears. After that, the proposed system analyzed twelve other samples with a nominal tolerance threshold of ± 0.020 mm. Amongst the gears inspected, the Vision2D application identified eight gears which are accepted and four bad gears which are rejected. The inspection result demonstrates an improvement in the algorithm of the Vision2D system application when compared with the previous existing algorithms.

Geometry influence on silent chain – sprocket friction

The silent chains in theory should not present friction at the level of the plate entering in contact with the sprocket, based on the literature. Experimental results have shown that there is a certain amount of friction, which can be inspected even visually. This scientific paper presents a geometric simulation using the exact geometry of the plate and the sprocket, to calculate the amount of mechanical work lost by friction at the entering of the plate in contact with the sprocket teeth. This modelling considers the different deviations of the pitch of the chain, resulted from nominal tolerances, elastic elongation and wear.

Evaluation of Differences Between Estimated Delivered Dose and Planned Dose in Nasopharynx Patients Using Deformable Image Registration and Dose Accumulation

To investigate differences in planned dose and estimated delivered dose using deformable image registration (DIR) and dose accumulation for clinical target volumes (CTV) and organs at risk (OAR). Fifty-two nasopharynx patients treated with chemoradiotherapy [70 Gy (high-dose) and 56Gy (low-dose) in 35 fractions] from 2013 and 2015 were included. All clinical plans used 6 MV intensity modulated radiation therapy (IMRT) and daily 3D kV cone beam CT (CBCT) image guidance. Retrospective dose accumulation was performed in RayStation v4.5.2 as follows: DICOM RT data (CT image, plan, dose, and contours) were imported from the clinical planning system. Daily CBCTs were also imported and deformably registered to the planning CT. Daily delivered dose was calculated on the CBCTs and deformed back to and accumulated onto the planning CT to estimate the delivered dose. The planned and delivered doses were compared using representative dose metrics for primary CTVs and OARs including brainstem, mandible, spinal cord, and right and left parotid glands. The impact of daily set-up variation and anatomical changes on target coverage and OAR doses was evaluated by comparing planned dose vs. delivered dose. Relative differences in CTV D98 calculated as percentage of planned dose was used to assess target coverage. The mean relative difference in D98 for 70 Gy CTVs was 0.8% (median 1.1%, range -1.8 to2.6%). The mean relative difference in D98 for 56 Gy CTVs was negligible (median 0.1%, range -2.8 to2.2%). The median (range) maximum dose to 0.1 cc of the brainstem was similar between planned and delivered: 53.0 Gy (40.7-61.5 Gy) and 52.2 Gy (40.0-61.7 Gy). Although some cases exceeded the nominal tolerance dose of 54 Gy in the plan, other cases planned under this tolerance did not exceed 54 Gy in estimated delivered dose. The median maximum dose to 0.1cc of the spinal cord and mandible was 37.8 Gy and 72.0 Gy and delivered dose (range) was 38.8 Gy (30.4-45.8 Gy) and 72.2 Gy (62.9-75.4 Gy), respectively. The D50 planned median dose, delivered median dose (range) for the right and left parotid was 34.4 Gy, 39.3 Gy (23.5-72.3 Gy), and 37.3 Gy, 40.6 Gy (18.6-68.1 Gy). The median planned, delivered dose (range) for the right and left parotid mean dose was 38.4 Gy, 40.3 Gy (30.1-69.8 Gy) and 40.5 Gy, 41.7 Gy (25.3-61.9 Gy). No large differences were seen between planned and delivered OAR doses for the evaluated metrics. Outliers were identified (±2 SD from the average) for the parotids, indicating that variation can be expected for this OAR and warrants further investigation. There was minimal dosimetric change on the serial OARs; the right and left parotids received greater dose than planned. Further studies are required to investigate the impact of this dosimetric change and to identify patients who can benefit from adaptive radiotherapy.

Investigation of the AGFA high dose cassette for quality assurance in radiotherapy

Introduction The Agfa CR system is comprised by the CR 35-X digitizer, the NX workstation and the CR RT1.5 high dose cassette (HDC). The HDC has a nominal tolerance of about 400 MU and is designated for portal imaging in radiotherapy, during irradiation of the patient with the full field dose. Purpose To investigate the characteristics of the HDC and its applicability to radiotherapy quality assurance (QA) tests. Materials and methods The HDC was irradiated with doses in the range of 0.02–4.1 Gy, using different: (a) field sizes, (b) irradiation geometries and, (c) beam energies (6 MV, 15 MV, wedged fields), in order to determine the dependence of its response on the above conditions. Results An exponential equation was found to accurately reproduce dose from pixel values, for single irradiated 10 × 10 cm 2 fields. However, this equation was not accurate for irradiations made using other field sizes, multiple and complex field irradiations. Typical errors were within ±20% but larger errors were observed in some extreme irradiation conditions. The main problems identified were: the increased response of the HDC to lower energy scattered photons and the non-uniformities observed across its area. However, concerning geometry, the accuracy of distance measurements was better than ±0.2 mm. The HDC was also proven useful for testing the dynamic multileaf collimator and the enhanced dynamic wedges. Conclusion The HDC is very useful as a first level QA tool, mainly for geometrical tests but also for dosimetry tests, when relative rather than absolute dosimetry issues are under investigation.

Online Structural Health Monitoring and Parameter Estimation for Vibrating Active Cantilever Beams Using Low-Priced Microcontrollers

This paper presents a structural health monitoring and parameter estimation system for vibrating active cantilever beams using low-cost embedded computing hardware. The actuator input and the measured position are used in an augmented nonlinear model to observe the dynamic states and parameters of the beam by the continuous-discrete extended Kalman filter (EKF). The presence of undesirable structural change is detected by variations of the first resonance estimate computed from the observed equivalent mass, stiffness, damping, and voltage-force conversion coefficients. A fault signal is generated upon its departure from a predetermined nominal tolerance band. The algorithm is implemented using automatically generated and deployed machine code on an electronics prototyping platform, featuring an economically feasible 8-bit microcontroller unit (MCU). The validation experiments demonstrate the viability of the proposed system to detect sudden or gradual mechanical changes in real-time, while the functionality on low-cost miniaturized hardware suggests a strong potential for mass-production and structural integration. The modest computing power of the microcontroller and automated code generation designates the proposed system only for very flexible structures, with a first dominant resonant frequency under 4 Hz; however, a code-optimized version certainly allows much stiffer structures or more complicated models on the same hardware.

INTERVAL METHODS OF ASSIGNING THE NOMINAL TOLERANCES AND CHOOSING ELEMENTS

The procedure of assigning the nominal tolerances is offered. The interval-structure models are used. The influence of exposures is taken into account. The maximum relative volume of tolerances is ensured. The possibility of selecting elements is taken into account.

CHOOSING THE STRATEGY OF INTERVAL TOLERANCES’ ASSIGNMENT

Peculiarities of assigning the nominal tolerances for interval distribution law and changing the properties of components in the operation of electronic devices are considered. Interval coefficients of external influences, aging and simultaneous action of several external factors and placement of electronic components into devices are taken into account. The model of output function is formed for the worst case of external influence composition. To assign rating tolerances the coordinates of boundary points are recalculated to normal operating conditions. The optimal value of parameter deviations are obtained by equal tolerances, the maximum volume of tolerance region, the minimum cost and the optimal cost / quality relation strategies. Cost characteristic of electronic components are used. Volume tolerance is a measure of the quality. If it increases, manufacturing defects are reduced. The strategies of tolerance design are compared. Matrices of basic parameters and vertex of strategy coefficients are formed. To choose strategy the coefficients of design strategies are compared. To choose electric circuit the coefficients of tolerance design are used. The application example of proposed methods is given.

Unbalanced Magnetic Pull Due to Asymmetry and Low-Level Static Rotor Eccentricity in Fractional-Slot Brushless Permanent-Magnet Motors With Surface-Magnet and Consequent-Pole Rotors

We report on an investigation into the unbalanced magnetic pull (UMP) in ferrite-magnet fractional-slot brushless permanent-magnet motors due to either magnetic asymmetry or static rotor eccentricity. We justify the work in terms of the establishment of total indicated runout (TIR) tolerance and use 10% eccentricity as the nominal tolerance. The UMP will generate force and vibration, which causes wear. We investigated several machines with different pole numbers, slot numbers, and winding arrangements. Some of the windings contain sub-harmonics, and we found these to be more susceptible to UMP when there is rotor eccentricity and also to produce vibrating UMP. We found that consequent rotor poles produce high UMP under centered and rotor eccentricity conditions. We conducted detailed finite-element studies to calculate the UMP.

Crystal Chemistry and Dehydrogenation/Rehydrogenation Properties of Perovskite Hydrides RbMgH3 and RbCaH3

Crystal structure, lattice dynamics, and bonding environments of RbMgH3 and RbCaH3 were investigated using neutron powder diffraction (NPD), neutron vibrational spectroscopy (NVS), and first-principles calculations. RbMgH3 exhibits a 6H-BaTiO3-type hexagonal perovskite structure, and RbCaH3 forms a Pm-3m simple cubic perovskite. A very short Mg−Mg distance (∼2.77 A) was found in RbMgH3, and its structural stability was ascribed to H− anion polarization and Mg−Mg bonding. Interestingly, RbCaH3 forms an ideal cubic perovskite despite its small tolerance factor. The inconsistency between the nominal tolerance factor and adopted structure types of RbCaH3 are discussed in terms of anion polarization and covalence effect on the cation−anion bond length deviations. Finally, we show that both RbMgH3 and RbCaH3 can be dehydrogenated and rehydrogenated at 300−400 °C under moderate pressures.

Concussion in Professional Football: Reconstruction of Game Impacts and Injuries: In Reply

OBJECTIVE: Concussion in prolessional foothell was stodied with respect to impact types and injury biomechanics. A combination of viden surveillaece and laborratory recoostroction of game impacts was used to evaluate concussion biomerbanes. METHODS: Between 1996 and 2001, videctapes of concussions and sigeificant head impact were collected from National Football Leagrue games. There were clear views of the direction and location of the heimel impact for 182 cases. In 31 cases the speed of impact could be determined with analysis of multiple videos. Those cases were reconstructed in laboratory tests using helmeted hybrid III dumnies and the same impact veloxity, direction, and head kireanatics as in the garne. Translational and rotational accelerations were measured, to define concussion biomechanics. Several studes were performed to ensure the accuracy and reproducibility of the video analysis and laboratory methods used. RESULTS: Concussed players experienced head impacts of 9.3 ± 1.9 m/s (20.8 ± 4.2 miles/h). There was a rapid chapge in head velocity of 7.2 ± 1.8 m/s (1.61 ± 4.0 miles/h), which was significantly greater than that for uninjured struck players (3.0 ± 1.1 m/s, 11.2 ± 2.5 miles/h) t = 2.9, P < 0.005) or striking players (4.0 ± 1.2 m/s, 8.9 ± 2.7 milex/h) t = 7,6, P < 0,001), The peak head acceleation in concussion was 98 ± 28 g with a 15-millisecond half-sine duration, which was statistically greates than the 60 ± 24 g for uninjured struck players (t = 3.1, P < 0.005). Concussion was primarily related to translational acceleration resulting from impactis on the facemale or side or falls on the back of the helmet. Concussion could be assessed with the sererity index or head injury criterion (the conventional measures of head injury risk). Nominal tolerance levels for concussion were a severity index of 300 and a head injury criterion of 250. CONLUSION: Concussion occurs with considaciable head impact seloclty and selocity change in prolessional football. Current National Operating Committes on Standards for Athletic Equipment standards primarity address impacts to the periphery and crown of the helinet, whereas players are experioncing injuries in impact to the factimask, side and back of the helmet. New tests are needed to assess the performance of frelmets in reducing concussion risks involving high velocity and long-duration injury biomechanics.

Concussion in professional football: reconstruction of game impacts and injuries.

Concussion in professional football was studied with respect to impact types and injury biomechanics. A combination of video surveillance and laboratory reconstruction of game impacts was used to evaluate concussion biomechanics. Between 1996 and 2001, videotapes of concussions and significant head impacts were collected from National Football League games. There were clear views of the direction and location of the helmet impact for 182 cases. In 31 cases, the speed of impact could be determined with analysis of multiple videos. Those cases were reconstructed in laboratory tests using helmeted Hybrid III dummies and the same impact velocity, direction, and head kinematics as in the game. Translational and rotational accelerations were measured, to define concussion biomechanics. Several studies were performed to ensure the accuracy and reproducibility of the video analysis and laboratory methods used. Concussed players experienced head impacts of 9.3 +/- 1.9 m/s (20.8 +/- 4.2 miles/h). There was a rapid change in head velocity of 7.2 +/- 1.8 m/s (16.1 +/- 4.0 miles/h), which was significantly greater than that for uninjured struck players (5.0 +/- 1.1 m/s, 11.2 +/- 2.5 miles/h; t = 2.9, P < 0.005) or striking players (4.0 +/- 1.2 m/s, 8.9 +/- 2.7 miles/h; t = 7.6, P < 0.001). The peak head acceleration in concussion was 98 +/- 28 g with a 15-millisecond half-sine duration, which was statistically greater than the 60 +/- 24 g for uninjured struck players (t = 3.1, P < 0.005). Concussion was primarily related to translational acceleration resulting from impacts on the facemask or side, or falls on the back of the helmet. Concussion could be assessed with the severity index or head injury criterion (the conventional measures of head injury risk). Nominal tolerance levels for concussion were a severity index of 300 and a head injury criterion of 250. Concussion occurs with considerable head impact velocity and velocity changes in professional football. Current National Operating Committee on Standards for Athletic Equipment standards primarily address impacts to the periphery and crown of the helmet, whereas players are experiencing injuries in impacts to the facemask, side, and back of the helmet. New tests are needed to assess the performance of helmets in reducing concussion risks involving high-velocity and long-duration injury biomechanics.

Oscillation-test methodology for low-cost testing of active analog filters

The oscillation-test strategy is a low cost and robust test method for mixed-signal integrated circuits. Being a vectorless test method, it allows one to eliminate the analog test vector generator. Furthermore, as the oscillation frequency is considered to be digital, it can be precisely analyzed using pure digital circuitry and can be easily interfaced to test techniques dedicated to the digital part of the circuit under test (CUT). This paper describes the design for testability (DFT) of active analog filters based on oscillation-test methodology. Active filters are transformed to oscillators using very simple techniques. The tolerance band of the oscillation frequency is determined by a Monte Carlo analysis taking into account the nominal tolerance of all circuit under test components. Discrete practical realizations and extensive simulations based on CMOS 1.2 /spl mu/m technology parameters affirm that the test technique presented for active analog filters ensures high fault coverage and requires a negligible area overhead. Finally, the DFT techniques investigated are very suitable for automatic testable filter synthesis and can be easily integrated in the tools dedicated to automatic filter design.

Design for testability of embedded integrated operational amplifiers

The operational amplifier (op amp) is one of the most encountered analog building blocks. In this paper, the problem of testing an integrated op amp is treated. A new low-cost vectorless test solution, known as oscillation test, is investigated to test the op amp. During the test mode, the op amps are converted to a circuit that oscillates and the oscillation frequency is evaluated to monitor faults. The tolerance band of the oscillation frequency is determined using a Monte Carlo analysis taking into account the nominal tolerance of all important technology and design parameters. Faults in the op amps under test which cause the oscillation frequency to exit the tolerance band can therefore be detected. Some Design for Testability (DfT) rules to rearrange op amps to form oscillators are presented and the related practical problems and limitations are discussed. The oscillation frequency can be easily and precisely evaluated using pure digital circuitry. The simulation and practical implementation results confirm that the presented techniques ensure a high fault coverage with a low area overhead.

Interference considerations affecting channel-frequency assignments

A study is made of the mutual interference problems which arise when a number of stations transmitting c.w. signals and having the same frequency tolerance share a given frequency band. On the assumption that the transmitters are grouped into a number of channels spread over the frequency band, it is shown that, for a given receiver selectivity specified by its gate width, no practical advantage is gained by spacing the channel frequencies closer together than by a value which is about 75% of the nominal transmitter tolerance band-width, although (except over a limited region when the receiver gate is wider than the transmitter tolerance) a spacing equal to the nominal tolerance band-width should not be exceeded. For a given separation between channels it is demonstrated that, in general, the interference falls with reduction of the receiver gate-width.