On Developing an Electromechanical Drive Equipped with a Ball Screw Protected from Jamming

2020 ◽  
pp. 66-82
Author(s):  
R.R. Abdulin ◽  
V.V. Bolshakov ◽  
A.S. Zudilin ◽  
A.N. Stitsenko ◽  
N.V. Krylov ◽  
...  
Keyword(s):  
Dynamic Properties ◽  
Import Substitution ◽  
Cylindrical Body ◽  
The Body ◽  
Ball Screw ◽  
Helical Line ◽  
Screw Thread ◽  
Screw Design ◽  
Electromechanical Drive ◽  
Rolling Elements

At present, one of the most pressing issues is the problem of improving electromechanical drive reliability, specifically, eliminating the possibility of jamming in the ball screw. The paper proposes an engineering solution designed to replace expensive imported ball screws. We analysed alternative designs intended to improve electromechanical drive reliability. We proposed and patented a ball screw design featuring a separator, in which the nut acts as a piston. The structure consists of a smooth cylindrical body and a slotted separator, its slots positioned along a helical line with a step equal to the thread lead. The body and the separator are coaxial and rigidly fixed together at the separator end faces so that the rolling elements remain in contact with the screw thread surfaces, the internal smooth cylindrical surface of the nut body and the surfaces of the separator slots. The ball screw design proposed, which features a nut with no internal threading, significantly simplifies the structure and its manufacturing technology. We built a model of an electromechanical drive equipped with a recirculating ball screw in order to determine static and dynamic properties of an electromechanical drive containing a ball screw featuring a separator. We compared the strength of the ball screw designs considered. As the ball screw featuring a separator is simpler and more reliable, the results of our analysis and the properties of an electromechanical drive equipped with the design proposed show that it is a promising solution to the import substitution problem concerning recirculating ball screws

Chaos in body–vortex interactions

2010 ◽  
Vol 466 (2119) ◽  
pp. 1871-1891 ◽  
Author(s):  
Johan Roenby ◽  
Hassan Aref
Keyword(s):  
Body Shape ◽  
Mass Density ◽  
Relative Equilibrium ◽  
Large Body ◽  
Point Vortex ◽  
Cylindrical Body ◽  
The Body ◽  
Body Motion ◽  
Single Vortex ◽  
Vortex Interactions

The model of body–vortex interactions, where the fluid flow is planar, ideal and unbounded, and the vortex is a point vortex, is studied. The body may have a constant circulation around it. The governing equations for the general case of a freely moving body of arbitrary shape and mass density and an arbitrary number of point vortices are presented. The case of a body and a single vortex is then investigated numerically in detail. In this paper, the body is a homogeneous, elliptical cylinder. For large body–vortex separations, the system behaves much like a vortex pair regardless of body shape. The case of a circle is integrable. As the body is made slightly elliptic, a chaotic region grows from an unstable relative equilibrium of the circle-vortex case. The case of a cylindrical body of any shape moving in fluid otherwise at rest is also integrable. A second transition to chaos arises from the limit between rocking and tumbling motion of the body known in this case. In both instances, the chaos may be detected both in the body motion and in the vortex motion. The effect of increasing body mass at a fixed body shape is to damp the chaos.

scholarly journals Identification of Dynamic Parameters of Pedestrian Walking Model Based on a Coupled Pedestrian–Structure System

2021 ◽  
Vol 11 (14) ◽  
pp. 6407
Author(s):  
Huiqi Liang ◽  
Wenbo Xie ◽  
Peizi Wei ◽  
Dehao Ai ◽  
Zhiqiang Zhang
Keyword(s):  
Negative Correlation ◽  
Dynamic Properties ◽  
Damping Ratio ◽  
Field Testing ◽  
The Body ◽  
Structural Vibration ◽  
Pedestrian Dynamics ◽  
Structure Interaction ◽  
Mass Spring ◽  
Stiffness And Damping

As human occupancy has an enormous effect on the dynamics of light, flexible, large-span, low-damping structures, which are sensitive to human-induced vibrations, it is essential to investigate the effects of pedestrian–structure interaction. The single-degree-of-freedom (SDOF) mass–spring–damping (MSD) model, the simplest dynamical model that considers how pedestrian mass, stiffness and damping impact the dynamic properties of structures, is widely used in civil engineering. With field testing methods and the SDOF MSD model, this study obtained pedestrian dynamics parameters from measured data of the properties of both empty structures and structures with pedestrian occupancy. The parameters identification procedure involved individuals at four walking frequencies. Body frequency is positively correlated to the walking frequency, while a negative correlation is observed between the body damping ratio and the walking frequency. The test results further show a negative correlation between the pedestrian’s frequency and his/her weight, but no significant correlation exists between one’s damping ratio and weight. The findings provide a reference for structural vibration serviceability assessments that would consider pedestrian–structure interaction effects.

Seismic cone penetration test and seismic tomography in permafrost

2004 ◽  
Vol 41 (5) ◽  
pp. 796-813 ◽  
Author(s):  
Anne-Marie LeBlanc ◽  
Richard Fortier ◽  
Michel Allard ◽  
Calin Cosma ◽  
Sylvie Buteau
Keyword(s):  
Seismic Tomography ◽  
Dynamic Properties ◽  
Cone Penetration Test ◽  
The Body ◽  
Body Waves ◽  
Reconstruction Technique ◽  
Seismic Velocities ◽  
Penetration Test ◽  
Cone Penetration ◽  
Seismic Cone Penetration Test

Two high-resolution multi-offset vertical seismic profile (VSP) surveys were carried out in a permafrost mound near Umiujaq in northern Quebec, Canada, while performing seismic cone penetration tests (SCPT) to study the cryostratigraphy and assess the body waves velocities and the dynamic properties of warm permafrost. Penetrometer-mounted triaxial accelerometers were used as the VSP receivers, and a swept impact seismic technique (SIST) source generating both compressional and shear waves was moved near the surface following a cross configuration of 40 seismic shot-point locations surrounding each of the two SCPTs. The inversion of travel times based on a simultaneous iterative reconstruction technique (SIRT) provided tomographic images of the distribution of seismic velocities in permafrost. The Young's and shear moduli at low strains were then calculated from the seismic velocities and the permafrost density measured on core samples. The combination of multi-offset VSP survey, SCPT, SIST, and SIRT for tomographic imaging led to new insights in the dynamic properties of permafrost at temperatures close to 0 °C. The P- and S-wave velocities in permafrost vary from 2400 to 3200 m/s and from 900 to 1750 m/s, respectively, for a temperature range between –0.2 and –2.0 °C. The Young's modulus varies from 2.15 to 13.65 GPa, and the shear modulus varies from 1.00 to 4.75 GPa over the same range of temperature.Key words: permafrost, seismic cone penetration test, vertical seismic profiling, seismic tomography, dynamic properties.

Analysis of load distribution and contact stiffness of the single-nut ball screw based on the whole rolling elements model

2019 ◽  
Vol 43 (3) ◽  
pp. 344-365 ◽  
Author(s):  
Ye Chen ◽  
Chun-yu Zhao ◽  
Si-yu Zhang ◽  
Xian-li Meng
Keyword(s):  
Load Distribution ◽  
Contact Stiffness ◽  
Structural Parameters ◽  
Contact Angles ◽  
Ball Screw ◽  
Distribution Model ◽  
Axial Stiffness ◽  
Feed System ◽  
Normal Contact ◽  
Rolling Elements

This paper aims to investigate the load distribution and contact stiffness characteristics of the single-nut ball screw pair (SNBSP). First, the transformed relationship of coordinate systems is established. Then, the whole rolling elements load distribution model of the SNBSP is presented. Based on this, the whole rolling elements contact stiffness model is obtained. Applying the Newton–Raphson iterative method to solve the model, the normal force of rolling elements and the contact angles between balls and raceway surface are determined. The calculation results are reasonably consistent with those of the half pitch model. Then, the local contact stiffness and global contact stiffness are obtained. Furthermore, the effects of axial load and structural parameters of the SNBSP on the normal contact force, contact angle, and local and global contact stiffness are discussed using numeric analysis. Finally, a dynamic model of the z-axis feed system with time-varying axial stiffness is established, and the accuracy of the model is verified by experiments.

scholarly journals Development of precision blank carriage for manufacturing large gratings and echelles

2019 ◽  
Vol 11 (1) ◽  
pp. 168781401881954
Author(s):  
Xinfang Ge ◽  
Biao Chu
Keyword(s):  
High Performance ◽  
Single Neuron ◽  
Dynamic Properties ◽  
Hertzian Contact ◽  
Ball Screw ◽  
Proportional Integral Derivative ◽  
Precision Positioning ◽  
Long Distance ◽  
Proportional Integral Derivative Controller ◽  
Proportional Integral

A long-travel positioning device, which combines a ball-screw-driven coarse stage with a fine one, driven by piezoelectric translator, to achieve the long-distance traveling, up to 500 mm, as well as high-precision positioning, is crucial in the field of diffraction grating fabrication at nanometer scale. In this article, we present the design of the fine-feed drive stage with resolution as high as 20 nm and propose a single neuron-based proportional–integral–derivative controller to realize ultra-precision positioning. A high-performance piezoelectric translator is used to drive the mechanism, and the parallel leaf springs are used to guide the moving platform with preload force. A dynamic model of the precision positioning mechanism has been established by considering the Hertzian contact. In addition, the static and dynamic properties are investigated with the laser interferometry tracking methodology. The experimental results indicate that the positioning accuracy of less than 10 nm is obtained with the single neuron-based proportional–integral–derivative controller and also demonstrate the excellent performance of the proposed mechanism and control strategy.

Theoretical Study on the Influence of Planet Gear Rim Thickness and Bearing Clearance on Calculated Bearing Life

2019 ◽  
Vol 142 (3) ◽  
Author(s):  
Andreas Fingerle ◽  
Jonas Hochrein ◽  
Michael Otto ◽  
Karsten Stahl
Keyword(s):  
High Efficiency ◽  
Roller Bearing ◽  
The Body ◽  
Fem Model ◽  
Bearing Life ◽  
Bearing Load ◽  
Rolling Elements ◽  
Planet Gear ◽  
Cylindrical Roller Bearing ◽  
Cylindrical Roller

Abstract Planetary gearboxes are becoming more popular due to their high-power density and potentially high efficiency. When the planet bearings are internally mounted, the body of the planet gear has to be hollow. The demand for large outer diameters due to high-load requirements might result in a small planet rim thickness. Depending on the rim thickness, its rigidity may become very low. Due to the low stiffness and the special load conditions caused by the double meshing, the deformation of the planet and its bearings are unique. In this paper, the influence of rim thickness on bearing load and lifetime is examined. The analysis is performed with a finite element method (FEM) model of a planet rim with a built-in cylindrical roller bearing. With the resulting planet deformation from the FEM calculation, the load distribution on the rolling elements in the bearing and the bearing lifetime according to ISO/TS 16281:2008 has been evaluated.

Theoretical Study on the Influence of Planet Gear Rim Thickness and Bearing Clearance on Calculated Bearing Life

2019 ◽  
Author(s):  
Andreas Fingerle ◽  
Jonas Hochrein ◽  
Michael Otto ◽  
Karsten Stahl
Keyword(s):  
High Efficiency ◽  
Roller Bearing ◽  
The Body ◽  
Fem Model ◽  
Bearing Life ◽  
Bearing Load ◽  
Rolling Elements ◽  
Planet Gear ◽  
Cylindrical Roller Bearing ◽  
Cylindrical Roller

Abstract Planetary gearboxes are becoming more popular due to their high power density and potentially high efficiency. When the planet bearings are internally mounted, the body of the planet gear has to be hollow. The demand for large outer diameters due to high load requirements might result in a small planet rim thickness. Depending on the rim thickness, its rigidity may become very low. Due to the low stiffness and the special load conditions caused by the double meshing, the deformation of the planet and its bearings are unique. In this paper, the influence of rim thickness on bearing load and lifetime are examined. The analysis is performed with an FEM model of a planet rim with a built-in cylindrical roller bearing. With the resulting planet deformation from the FEM calculation, the load distribution on the rolling elements in the bearing and the bearing lifetime according to ISO/TS 16281:2008 have been evaluated.

Stability of towed, totally submerged flexible cylinders

1968 ◽  
Vol 34 (2) ◽  
pp. 273-297 ◽  
Author(s):  
M. P. Paidoussis
Keyword(s):  
Cylindrical Body ◽  
Quantitative Comparison ◽  
The Body ◽  
Low Flow ◽  
Critical Conditions ◽  
Neutral Buoyancy ◽  
Dimensionless Parameters ◽  
Optimum Stability ◽  
Conditions Of Stability ◽  
Oscillatory Instabilities

A general theory is presented to account for the small, free, lateral motions of a flexible, slender, cylindrical body with tapered ends, totally submerged in liquid and towed at steady speed U. For particular shapes of the ends and length of tow-rope, it is shown that the body may be subject to oscillatory and non-oscillatory instabilities for U > 0; at small U, these instabilities correspond to those of a rigid body. At higher U, the system generally regains stability in the above modes, but may be subject to higher-mode, flexural oscillatory instabilities. The critical conditions of stability are calculated extensively and the effect on stability of a number of dimensionless parameters is discussed. It is shown that optimum stability is achieved with a streamlined nose, a blunt tail and a short tow-rope.Some experiments are described which were designed to test the theory. Rubber cylinders of neutral buoyancy were held in vertical water flow by a nylon ‘tow-rope’. Provided the tail was streamlined and the tow-rope not too short, ‘criss-crossing’, non-flexural oscillations developed at very low flow. Increasing the flow, these oscillations ceased and the cylinder buckled like a column; subsequently higher-mode flexural oscillations developed. However, for a sufficiently blunt tail and short tow-rope, the system was completely stable.The experimental observations are generally in qualitative agreement with theory. Quantitative comparison of the various instability thresholds and stable zones between experiment and theory, based on estimated values of some of the theoretical dimensionless parameters, is also fairly good.

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