scholarly journals Self-Motion and the Shaping of Sensory Signals

2010 ◽  
Vol 103 (4) ◽  
pp. 2195-2207 ◽  
Author(s):  
Robert A. Jenks ◽  
Ashkan Vaziri ◽  
Ali-Reza Boloori ◽  
Garrett B. Stanley
Keyword(s):  
High Frequency ◽  
High Speed ◽  
External Environment ◽  
Low Frequency ◽  
Head Rotation ◽  
Object Localization ◽  
Behavioral Variability ◽  
Sensory Signals ◽  
Behavioral Variables ◽  
Self Motion

Sensory systems must form stable representations of the external environment in the presence of self-induced variations in sensory signals. It is also possible that the variations themselves may provide useful information about self-motion relative to the external environment. Rats have been shown to be capable of fine texture discrimination and object localization based on palpation by facial vibrissae, or whiskers, alone. During behavior, the facial vibrissae brush against objects and undergo deflection patterns that are influenced both by the surface features of the objects and by the animal's own motion. The extent to which behavioral variability shapes the sensory inputs to this pathway is unknown. Using high-resolution, high-speed videography of unconstrained rats running on a linear track, we measured several behavioral variables including running speed, distance to the track wall, and head angle, as well as the proximal vibrissa deflections while the distal portions of the vibrissae were in contact with periodic gratings. The measured deflections, which serve as the sensory input to this pathway, were strongly modulated both by the properties of the gratings and the trial-to-trial variations in head-motion and locomotion. Using presumed internal knowledge of locomotion and head-rotation, gratings were classified using short-duration trials (<150 ms) from high-frequency vibrissa motion, and the continuous trajectory of the animal's own motion through the track was decoded from the low frequency content. Together, these results suggest that rats have simultaneous access to low- and high-frequency information about their environment, which has been shown to be parsed into different processing streams that are likely important for accurate object localization and texture coding.

scholarly journals Small-Scale Drilling Test Rig For Investigation of Axial Excitation On The Drilling Process

2018 ◽  
Vol 148 ◽  
pp. 16001
Author(s):  
A. Austefjord ◽  
S. Blaylock ◽  
I. Forster ◽  
M. Sheehan ◽  
C. Wright
Keyword(s):  
High Frequency ◽  
High Speed ◽  
Low Frequency ◽  
Advanced Technology ◽  
Small Scale ◽  
Drilling Process ◽  
Generation Process ◽  
Rock System ◽  
Drilling Rig ◽  
Axial Excitation

This paper describes the design, construction and operation of a small-scale drilling rig for the purpose of investigation of the effect of axial excitation on the drilling process. The rig is bench top in size and has been designed to drill small rock samples, whilst at the same allowing axial excitation to be induced into the drilling process. The rig has been designed to drill the rock without any drilling fluids – so allowing improved observation of the chip generation process. Additionally, the drilling weight on bit is applied via masses, so allowing greater representation of the dynamic behavior of the drilling process – i.e. capturing more natural frequencies. The results from the rig have been obtained over two frequency ranges – low frequency (0-50 Hz) and high frequency (50-250 Hz). Results show that improved rate of penetration is obtained with axial excitation – with low and high frequency optima occurring. These optima can be related to the behavior of the string in the two frequency ranges – in the low frequency range, the entire string acts in unison; whereas at high frequency, only the bit/rock system is active. As a result, it is concluded that for low frequency operation, only information about the drill string is required to optimize performance; whereas for high frequency operation, information about the bit/rock system is required to optimize performance. Observation of the chip generation process via high speed video has shown that during axial excitation, regular shaped bricks are ejected when compared with the typical wedge- shaped chips that are normally ejected during the drilling process. It is concluded that, during the axial excitation process, the chips are being ejected via a levering action, so allowing a more efficient and quicker process. MIT [1] provided background classes, project guidance and project review as part of an NOV/MIT advanced technology program. Larger scale lab tests and/or field tests are required to verify/validate these conclusions.

Measurement of High Frequency Viscoelastic Properties of Deformed Rubber

2016 ◽  
Vol 715 ◽  
pp. 139-146 ◽  
Author(s):  
Tadayoshi Shoyama ◽  
Koji Fujimoto
Keyword(s):  
Resonance Frequency ◽  
High Frequency ◽  
High Speed ◽  
Dynamic Properties ◽  
Loss Modulus ◽  
Low Frequency ◽  
Soft Materials ◽  
Load Cell ◽  
Universal Prediction ◽  
Response Method

Bearings of small turbo machines support high speed rotors rotating with the frequency over 1 [kHz]. Such bearings are often supported with O-rings made of soft materials like rubber to attenuate high frequency oscillations. Dynamic properties of rubber supporters have been measured experimentally for individual dimensions, but the universal prediction of dynamic properties for various frequencies is difficult not only because rubbers exhibit nonlinearity against its strain, but because O-ring supporters deform heterogeneously. For the precise prediction, it is necessary to investigate the viscoelasticity of rubber under various deformations and frequencies. Such properties can be measured by the standard shear vibration non-response method of ISO 6721-6 (JIS K 7244-6). However this is applicable only to low frequency range under 100 [Hz] because of the limitation of resonance frequency of the load cell. In this research, based on BERM (Base Excitation Resonant Mass) method, a new method was developed to measure the complex shear modulus at high frequencies up to 1 [kHz] of rubber sheets under homogeneous shear deformations. In the presented method, the force is calculated from the acceleration of the mass instead of the direct measurement by a load cell. Hence accurate measurement became possible even in the range beyond the resonance frequency of a load cell. The measured shear storage modulus G’ and shear loss modulus G” of deformed rubber were presented.

scholarly journals Wall pressure beneath a transitional hypersonic boundary layer over an inclined straight circular cone

2020 ◽  
Vol 2 (1) ◽  
Author(s):  
Siwei Dong ◽  
Jianqiang Chen ◽  
Xianxu Yuan ◽  
Xi Chen ◽  
Guoliang Xu
Keyword(s):  
Boundary Layer ◽  
High Frequency ◽  
High Speed ◽  
Low Frequency ◽  
Axial Direction ◽  
Wall Pressure ◽  
Hypersonic Boundary Layer ◽  
High Frequency Signal ◽  
Local Boundary ◽  
Half Angle

AbstractProperties of wall pressure beneath a transitional hypersonic boundary layer over a 7∘ half-angle blunt cone at angle of attack 6∘ are studied by Direct Numerical Simulation. The wall pressure has two distinct frequency peaks. The low-frequency peak with f≈10−50 kHz is very likely the unsteady crossflow mode based on its convection direction, i.e. along the axial direction and towards the windward symmetry ray. High-frequency peaks are roughly proportional to the local boundary layer thickness. Along the trajectories of stationary crossflow vortices, the location of intense high-frequency wall pressure moves from the bottom of trough where the boundary layer is thin to the bottom of shoulder where the boundary layer is thick. By comparing the pressure field with that inside a high-speed transitional swept-wing boundary layer dominated by the z-type secondary crossflow mode, we found that the high-frequency signal originates from the Mack mode and evolves into the secondary crossflow instability.

A comprehensive optimal design method for magnetorheological dampers utilized in DMU power package

2021 ◽  
pp. 146442072110496
Author(s):  
Fanghui Xu ◽  
Dawei Dong ◽  
Yan Huang ◽  
Rui Zhang ◽  
Shizhe Song ◽  
...  
Keyword(s):  
Optimal Design ◽  
High Frequency ◽  
High Speed ◽  
Low Frequency ◽  
Mr Damper ◽  
Magnetic Flux Density ◽  
Objective Functions ◽  
Damping Force ◽  
Optimal Method ◽  
Mr Dampers

The diesel multiple unit (DMU) has been widely used in high-speed railway service due to its flexibility and economy. Considering the broadband and complex vibration generated by DMU power package, the advanced semi-active suspension with magnetorheological (MR) dampers is introduced to promote anti-vibration performance. In this work, a comprehensive optimal design approach for MR damper used in DMU power package is proposed. Quasi-static modeling process is conducted to obtain MR damper's low-frequency outputs, while its high-frequency damping forces are calculated by physical modeling considering the fluid compressibility and piston assembly inertia. Then the objective functions and optimization variables are determined. Based on response surface and linear correlation analysis, the influence of the optimal variables on the objective functions is discussed. Using reference-point based nondominated sorting approach (NSGA-III), the evolutionary many-objective optimization is conducted. In addition, magnetic design is incorporated into the optimal process to ensure the magnetic flux density in the effective working area. Finally, an optimized MR damper prototype is manufactured and tested. By comparing the experimental damping force with calculated results in both low-frequency and high-frequency ranges, the effectiveness of the presented optimal method for MR dampers is validated.

Comparative Feature Analysis of Ground Surface Vibration Induced by High-Speed Train Running on Viaduct and Embankment

2014 ◽  
Vol 638-640 ◽  
pp. 1229-1232
Author(s):  
Kun Ming Mao ◽  
Ting Ting Wang ◽  
Qian Wen Ru ◽  
Yan Li
Keyword(s):  
Frequency Band ◽  
High Frequency ◽  
High Speed ◽  
Fourier Spectrum ◽  
Three Dimensional ◽  
Low Frequency ◽  
Ground Surface ◽  
Vertical Acceleration ◽  
High Frequency Band ◽  
Surface Vibration

Based on the Abaqus parallel computing cluster system platform, the three-dimensional finite element model of train-track-viaduct/embankment-foundation-soil coupling is established. The three-dimensional space-time variation and Fourier spectrums characters of ground surface vibration vertical accelerations by high-speed train running on viaduct and embankment are simulated. The result shows that ground surface vibration is mainly excited by periodic axle force of the train in the site near the viaduct pier. In the site far from the viaduct pier, ground surface vibration is mainly from the transmission of the site near the viaduct pier. With the increased distance between the viaduct pier, the peak value of ground surface vibration vertical acceleration decreases, and decreases significantly when the distance is within 10m. There are two main frequency bands of Fourier spectrum of ground surface vibration vertical acceleration: low-frequency band 0-12Hz and high-frequency band 35-47Hz of viaduct route, and low-frequency band 0-21Hz and high-frequency band 25-45Hz of embankment route. In general, with the increased distance between viaduct/embankment, Fourier spectrum amplitude of every frequency band decrease, and attenuation speed of high-frequency band is much faster than-frequency band’s.

The Design and Control of a Rigid-flexible Coupling Positioning Stage for Enhanced Settling Performance

2021 ◽  
Author(s):  
Hao Peng ◽  
Zhijun Yang ◽  
Wenchao Xue ◽  
Ruirui Huang ◽  
Yi Huang
Keyword(s):  
High Frequency ◽  
High Speed ◽  
Mechanical Design ◽  
Dead Zone ◽  
Low Frequency ◽  
Poor Performance ◽  
Experimental Tests ◽  
Control Performance ◽  
Flexible Coupling ◽  
Positioning Stage

Abstract Traditional high-speed precision motion stage (HSPMS) design pursues high-stiffness structure to achieve fast response. However, such structure leads to high-frequency disturbance near dead zone of friction, which causes poor performance in controlling HSPMS. To this end, this paper proposes the active disturbance rejection control (ADRC) based mechanical design to reduce the bandwidth of friction disturbance and improve the control performance of HSPMS. It is proved that the low-frequency disturbance can be more effectively tackled by the extended state observer (ESO) in the frame of ADRC. In particular, rigid-flexible coupling (RFC) positioning stage is presented for converting the high-frequency friction disturbance into the low-frequency elastic deformation disturbance by flexure hinges. The experimental tests are carried out for both traditional stage and RFC stage. It is clearly shown that compared with traditional design, the control performance of RFC stage is remarkably promoted.

Design of a Retrofittable Spindle Attachment for High Frequency Vibration-Assisted Drilling

2014 ◽  
Author(s):  
J. Panju ◽  
M. Meshreki ◽  
M. H. Attia
Keyword(s):  
High Frequency ◽  
High Speed ◽  
Low Frequency ◽  
Cutting Parameters ◽  
High Amplitude ◽  
Spindle Attachment ◽  
Vibration Assistance ◽  
Low Amplitude ◽  
Thrust Forces ◽  
Conventional Drilling

Conventional drilling of modern super alloys and composite material induces high stresses in the vicinity of drilled holes along with high thrust forces which lead to problems in terms of hole quality and accuracy as well as increased tool wear. A recent and promising technique to overcome these challenges is to introduce vibration assistance in the cutting zone by superimposing oscillating vibration in the feed direction of the tool. Two regimes of vibration excitation could be applied for this purpose: low frequency (<500 Hz) high amplitude (>100 μm) and high frequency (>500 Hz) low amplitude (<20 μm). Motivated by the advantages of the HF-VAD and the limited work available in the literature for this regime, a new system is developed by the authors where the rotating tool is excited to high frequency and low amplitude. The new design is based on the use of piezoelectric actuators to generate the motion and a high speed slip ring to ensure the transfer of sufficient power to the actuator. A novel concept was implemented by de-coupling the rotary motion of the spindle from the vibrational motion of the actuator to ensure a higher efficiency of power transmission without damaging either the actuator or the spindle. With this design, a retrofittable HSK 100A toolholder with high frequency excitation spindle attachment was manufactured to incorporate drill sizes up to 1/4 inches. Commissioning tests were performed under no load and spring loaded conditions and it was found that the system has a capability to excite the tool up to 100 μm at 900 Hz (resonance frequency) and up to 5 μm between 500–800 Hz and 1100–2500 Hz. HF-VAD tests were conducted using this new attachment on Aluminum 6061 and it was found that the system was able to successfully obtain the prescribed frequency and amplitude. Up to 50% reduction in thrust forces was obtained in HF-VAD in comparison to conventional drilling under same cutting parameters; this is associated with finer chips with break off serrations.

Cluster Analysis on Vibration Characteristic in High Speed Ball-End Milling Hardened Steel

2011 ◽  
Vol 188 ◽  
pp. 145-149
Author(s):  
Bin Jiang ◽  
S.C. Yang ◽  
Yin Jin Yang ◽  
Min Li Zheng ◽  
P. Sun
Keyword(s):  
Surface Roughness ◽  
High Frequency ◽  
High Speed ◽  
End Milling ◽  
Low Frequency ◽  
Hardened Steel ◽  
High Speed Milling ◽  
Ball End Milling ◽  
Vibration Behavior ◽  
Low Frequency Vibration

Aim at the uncertainty of vibration behavior in high speed ball-end milling hardened steel, carried out the experiment of high speed milling hardened steel and modal analysis of cutter, studied vibration behavior of cutter and workpiece, and established vibration behavior sequence of high speed milling hardened steel. Using gray system theory, did gray cluster analysis of vibration characteristics, explored the correlation among cutter vibration, workpiece vibration and surface roughness characteristics, put forward the method of characterizing vibration characteristics in high speed ball-end milling hardened steel. The results show that high frequency vibrations of cutter and workpiece are caused by the interaction of centrifugal and dynamic cutting force, the increase of cutter overhang enhances high frequency vibration of cutter, the characteristic of cutter vibration changes from low frequency vibration to interaction of low frequency vibration and high frequency vibration. Using cutters with different overhang, surface roughness of high speed milling hardened steel has similar characteristics, surface roughness in row spacing direction can characterize low frequency vibration of cutter, and surface roughness in feed can characterize resonance characteristic of cutter caused by high frequency vibrations of cutter and workpiece.

Full Band S-Parameter Generation Methodology for High Speed Package Interconnect Modeling

2005 ◽  
Author(s):  
Xiangyin Zeng ◽  
Jiangqi He ◽  
Baoshu Xu
Keyword(s):  
Frequency Band ◽  
Time Domain ◽  
High Frequency ◽  
High Speed ◽  
Signal Integrity ◽  
Low Frequency ◽  
Frequency Range ◽  
Full Wave ◽  
S Parameter ◽  
Full Band

Beyond GHz operation frequency and Gb/s transfer rate bring a big challenge to high speed package interconnect designs. To make sure the product meets the specifications, signal integrity analysis has to be done carefully for critical signals before tape out for manufacturing. In order to obtain an accurate signal integrity modeling, the package interconnect must be accurately modeled. Frequency domain S-parameter has been widely used to replace the traditional package lumped model characterized by the fixed values of R, L, and C, which is no longer accurate. To facilitate the time domain analysis, equivalent circuits or behavioral macro models can be established based on the frequency domain S-parameter. In order to obtain a stable, casual and accurate time domain response, the S-parameter should be accurate in the full frequency band from DC to the interested maximum frequency. Usually full wave electromagnetic simulators are used to obtain the package S-parameter. The obtained S-parameter is very accurate in high frequency band, but unfortunately poor in low frequency band which is usually an extrapolation of the high frequency results. Improper use of such EM tools will result in wrong S-parameter, which may sometimes bring instability to the final results in a time-domain simulator based on direct convolution. The equivalent circuit synthesized from the high frequency S-parameter may also generate poor result due to lack of accurate information in the low frequency band. In this paper, we first address the theoretic al reason for the inaccurate low frequency result from the full wave electromagnetic simulators. Then we introduce a new process to generate accurate S-parameter in the full interested frequency band. In the process, the frequency band is divided into three parts, the low frequency range, middle frequency range, and the high frequency range. Skin effect phenomenon is found to be the physical explanation for the frequency band division. It is found that properly choosing EM tools in the proper frequency band is the key to get accurate full band S-parameters.

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