scholarly journals Gravito-inertial ambiguity resolved through head stabilization

2019 ◽  
Vol 475 (2223) ◽  
pp. 20180010 ◽  
Author(s):  
Ildar Farkhatdinov ◽  
Hannah Michalska ◽  
Alain Berthoz ◽  
Vincent Hayward
Keyword(s):  
Mechanistic Model ◽  
Angular Position ◽  
Head Acceleration ◽  
Body Movements ◽  
Otolith Organ ◽  
Central Function ◽  
Head Stabilization ◽  
Inertial Measurements ◽  
Gravitational Vertical

It has been frequently observed that humans and animals spontaneously stabilize their heads with respect to the gravitational vertical during body movements even in the absence of vision. The interpretations of this intriguing behaviour have so far not included the need, for survival, to robustly estimate verticality. Here we use a mechanistic model of the head/otolith organ to analyse the possibility for this system to render verticality ‘observable’, a fundamental prerequisite to the determination of the angular position and acceleration of the head from idiothetic, inertial measurements. The intrinsically nonlinear head-vestibular dynamics is shown to generally lack observability unless the head is stabilized in orientation by feedback. Thus, our study supports the hypothesis that a central function of the physiologically costly head stabilization strategy is to enable an organism to estimate the gravitational vertical and head acceleration during locomotion. Moreover, our result exhibits a rare peculiarity of certain nonlinear systems to fortuitously alter their observability properties when feedback is applied.

Optimal Tooth Modifications in Hypoid Gears

2003 ◽  
Author(s):  
Vilmos V. Simon
Keyword(s):  
Angular Position ◽  
Point Contact ◽  
Tooth Surface ◽  
Gear Pair ◽  
Hypoid Gear ◽  
Tooth Contact ◽  
Hypoid Gears ◽  
Transmission Errors ◽  
Tool Profile

A method for the determination of optimal tooth modifications in hypoid gears based on improved load distribution and reduced transmission errors is presented. The modifications are introduced into the pinion tooth surface by using a cutter with bicircular profile and by changing the cutter diameter. In the optimization of tool parameters the influence of shaft misalignments of the mating members is included. As the result of these modifications a point contact of the meshed teeth surfaces appears instead of line contact; the hypoid gear pair becomes mismatched. By using the method presented in [1] the influence of tooth modifications introduced on tooth contact and transmission errors is investigated. Based on the results that was obtained the radii and position of circular tool profile arcs and the cutter diameter for pinion teeth generation were optimized. By applying the optimal tool parameters, the maximum tooth contact pressure is reduced by 16.22% and the angular position error of the driven gear by 178.72%, in regard to the hypoid gear pair with a pinion manufactured by a cutter of straight-sided profile and of diameter determined by the commonly used methods.

Magnetometric determination of the angular position of an object

1996 ◽  
Vol 39 (12) ◽  
pp. 1217-1220
Author(s):  
B. M. Smirnov
Keyword(s):  
Angular Position

Determination of reflector angular position using directional phase-encoded wavefield

1995 ◽  
Vol 33 (1) ◽  
pp. 15-25 ◽  
Author(s):  
S.T.T. Ha ◽  
Hua-Wei Zhou ◽  
J.A. McDonald
Keyword(s):  
Angular Position

scholarly journals Lunar Libration Tables and Determination of Crater Coordinates

1997 ◽  
Vol 165 ◽  
pp. 281-286
Author(s):  
Natasha Petrova
Keyword(s):  
Gravitational Field ◽  
Solar System ◽  
Angular Position ◽  
Theoretical Description ◽  
Laser Ranging ◽  
Radio Sources ◽  
Space Technology ◽  
The Moon ◽  
Lunar Rotation

The study of lunar rotation has attracted considerable interest with the advent of the epoch of exploration of the Solar system by space technology. A series of works on an investigation of the lunar gravitational field carried out with the help of artificial lunar satellites have greatly advanced our possibility for that study. The problem concerning the landing on the lunar surface of spacecraft, and the creation of durable lunar bases, impose heavy demands on the accuracy of theoretical description of orbital and rotational motion of the Moon.The development of the observational technology with the help of radio-and laser ranging (LLR) provides at the present time measurements of the distance to a given point on the Moon with an accuracy of about 2 cm, probably improved in the future to about 5mm (Banerdt, 1995). By using differential VLBI measurement with extragalactic radio sources angularly near the Moon, it should be possible to obtain routine estimates of angular position of the beacon to 0.1 mas from each observation (Baudry, 1995). Therefore, combining VLBI and LLR techniques will provide a means of achieving new objectives, and that calls for the development of the theories adequate to an accuracy for observations.

Methods of Rotor-Unbalance Determination

1939 ◽  
Vol 6 (1) ◽  
pp. A1-A6
Author(s):  
J. G. Baker
Keyword(s):  
Mathematical Method ◽  
Internal Combustion Engine ◽  
Combustion Engine ◽  
Angular Position ◽  
Normal Operation ◽  
Axial Position ◽  
Rigid Rotor ◽  
Engine Crankshaft ◽  
Quick Determination

Abstract Rotor-unbalance determinations both in balancing machines and from vibration readings taken on the rotor during normal operation have in some cases been rather complicated and often subject to considerable error. This paper suggests methods intended to improve balancing methods in these cases. In part I a more or less conventional method of calculating unbalance corrections from vibration readings is reviewed and the limitations and errors pointed out. Next, an extension of the method is developed which is in some cases simpler and inherently more accurate. In part II a mathematical method is developed for determining unbalance corrections in cases where the locations of the corrections are completely prescribed in contradistinction to the ordinary case in which the axial position of the correction is prescribed but the angular position is to be determined. Also, a balancing machine is described which reads directly the unbalance corrections required at four preselected locations in a rigid rotor. This balancing machine is especially suited for the quick determination of unbalance corrections required in an internal-combustion-engine crankshaft. In part III center-of-percussion balancing is described which is a method of taking vibration readings which can be interpreted directly in terms of unbalance. This method is applicable only under certain conditions which are noted.

scholarly journals Reconstruction of the Image Metric of Periodic Structures in an Opto-Digital Angle Measurement System

Sensors ◽  
2021 ◽  
Vol 21 (13) ◽  
pp. 4411
Author(s):  
Alexander N. Korolev ◽  
Alexander Ya. Lukin ◽  
Yurii V. Filatov ◽  
Vladimir Yu. Venediktov
Keyword(s):  
Periodic Structures ◽  
Angular Position ◽  
Digital Camera ◽  
Angle Measurement ◽  
Camera System ◽  
Optical Pattern ◽  
Image Metric ◽  
The Ideal ◽  
Camera Sensor

Measurement of the object angular position and its change is one of the important tasks in measurement technique. Our method is based on determination of the angular position of a 2D periodical optical pattern (2D mark) at the object, captured by the sensor of a digital camera. System performance can be frustrated by errors in determination of the spot coordinates on the camera sensor; by the presence of lens aberrations; by deviations from the parallelism of the pattern planes and the camera sensor; and by differences between the actual spots positions and the ideal grid. In the paper we discuss the effect of these errors and the way to correct or eliminate them. We have developed the mathematical routine and the corresponding numerical codes for correction of the said errors. The code and the routine we checked in a real experiment. It has shown that the correction decreases the standard deviation in 15 times.

scholarly journals Investigations of a D10 laboratory Farymann Diesel engine by means of a Langmuir probe

2013 ◽  
Vol 153 (2) ◽  
pp. 75-82
Author(s):  
Zbigniew Korczewski ◽  
Jacek Rudnicki ◽  
Leszek Piechowski ◽  
Adam Cenian
Keyword(s):  
Comparative Analysis ◽  
Diesel Engine ◽  
Langmuir Probe ◽  
Angular Position ◽  
Precise Determination ◽  
Injection System ◽  
Engine Fuel ◽  
Feed System ◽  
Working Space

A precise determination of the crankshaft angular position, at which the self fuel ignition occurs in a diesel engine, enables a credible diagnosis of the technical condition of the engine working space as well as the fuel feed system. An observation of the Langmuir probe signal provides entirely new possibilities for engine diagnostics. The probe is introduced into the working space of a cylinder through its indicator valve. This paper presents preliminary results of diagnostic tests performed on a D10 type Farymann Diesel engine. The main aim of the investigations was to confirm the diesel engine control susceptibility to the applied, original measuring method that enables a precise determination of the crank-shaft angle, under which the fuel self-ignition occurs. In order to verify the diagnostic results, simultaneous measurements have been conducted of the cylinder pressure as well as vibrations (measured on the cylinder head cover or its mounting bolts) generated by the engine fuel injection system and the valve timing system. A satisfactory qualitative and quantitative agreement of the recorded control parameters has been obtained using a simplified comparative analysis. The results showed that further upgrade of the diagnostic method as well as the computer software is necessary in order to synchronize all the monitored variables and enable a comparative analysis in relation to the angular crankshaft position.

High Precision Contact Model for Ball Bearings With Waviness

2021 ◽  
Author(s):  
Camille Jeannot ◽  
E. Sadoulet-Reboul ◽  
S. Dufrenoy
Keyword(s):  
High Precision ◽  
Predictive Models ◽  
Angular Position ◽  
Contact Model ◽  
Ball Bearings ◽  
Nonlinear Contact ◽  
Tangential Forces ◽  
Bearing Behavior ◽  
Global Parameters

Abstract Studying high precision ball bearings requires the development of predictive models. In presence of waviness on the rings, geometrical and also mechanical parameters will vary according to the angular position. To consider these modifications, a nonlinear contact model is proposed with normal and tangential forces calculation using Hertz and Dahl’s models. To solve the static equilibrium of the bearing, a highly modular energy method is developed. It allows the determination of both local and global parameters using the same equation. The 2D developed approach can be used to study different waviness orders and magnitudes to get a better understanding on how this affects the bearing behavior (contact load, balls gaping, pointing defects...). The presented results show that even small contact direction reorientation can create tangential forces. This modifies the bearing deflections and induces a residual moment. These phenomena can only be observed when the contact is accurately modeled.

SCANNER DESIGN SPECIFICITY FOR HELMET-MOUNTED TARGETING SYSTEM

2021 ◽  
Vol 156 (1) ◽  
pp. 29-37
Author(s):  
Volodymyr SENATOROV ◽  
Svitlana GLAZKOWA
Keyword(s):  
Angular Position ◽  
Design Principles ◽  
Geometric Parameters ◽  
The Other ◽  
Field Of View ◽  
Scanning Process ◽  
Counterclockwise Direction ◽  
Triangulation Method ◽  
Targeting Accuracy

Following design principles are important for helmet-mounted targeting systems. Two scanners on base of the polygonal reflector-type prisms forming the fanned field of view are fastened to head-up display. Three LEDs installed on pilot helmet form a plane, the normal of which is collinear to helmet indi-cator viewing line. Angles of LED bearings are measured with triangulation method and angular position of viewing line is calculat-ed. Two options for organization of scanning process are analyzed in the paper. In the first variant, one prism rotates in clockwise and the other in counterclockwise direction. In the second variant both prisms rotate in the same direction, clockwise for example. It is shown that if the prisms rotate in the same direction the targeting accuracy is greater. The algorithm developed for determination of targeting accuracy may be used to matching the rate of scanning and geometric parameters of helmet-mounted targeting system at prescribed accuracy of targeting.

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