High Speed Digital Holography for Measuring Time-Dependent Displacement and Vibrations

1995 ◽  
Author(s):  
Y. Y. Hung ◽  
C. T. Griffen
Keyword(s):  
High Speed ◽  
Digital Holography ◽  
Time Dependent ◽  
Vibration Measurement ◽  
Measuring Time ◽  
Novel Technique ◽  
Point Of Interest ◽  
Displacement Sensors ◽  
Image Acquisition System ◽  
Fringe Patterns

Abstract This paper presents a novel technique allowing time-dependent displacement of an object to be studied by continuously digitizing the speckle images using a high speed image acquisition system. Instead of generating fringe patterns, the displacement versus time for any point of interest can be studied. Therefore, the technique is equivalent to “many” massless and noncontact displacement sensors, which is particularly useful for vibration measurement.

scholarly journals Three-Axis Inductive Displacement Sensor Using Phase-Sensitive Digital Signal Processing for Industrial Magnetic Bearing Applications

Actuators ◽  
2021 ◽  
Vol 10 (6) ◽  
pp. 115
Author(s):  
Teemu Sillanpää ◽  
Alexander Smirnov ◽  
Pekko Jaatinen ◽  
Jouni Vuojolainen ◽  
Niko Nevaranta ◽  
...  
Keyword(s):  
Signal Processing ◽  
Digital Signal Processing ◽  
Eddy Current ◽  
High Speed ◽  
Digital Signal ◽  
Magnetic Bearing ◽  
Air Gap ◽  
Sensor Design ◽  
Quadrature Demodulation ◽  
Displacement Sensors

Non-contact rotor position sensors are an essential part of control systems in magnetically suspended high-speed drives. In typical active magnetic bearing (AMB) levitated high-speed machine applications, the displacement of the rotor in the mechanical air gap is measured with commercially available eddy current-based displacement sensors. The aim of this paper is to propose a robust and compact three-dimensional position sensor that can measure the rotor displacement of an AMB system in both the radial and axial directions. The paper presents a sensor design utilizing only a single unified sensor stator and a single shared rotor mounted target piece surface to achieve the measurement of all three measurement axes. The sensor uses an inductive measuring principle to sense the air gap between the sensor stator and rotor piece, which makes it robust to surface variations of the sensing target. Combined with the sensor design, a state of the art fully digital signal processing chain utilizing synchronous in-phase and quadrature demodulation is presented. The feasibility of the proposed sensor design is verified in a closed-loop control application utilizing a 350-kW, 15,000-r/min high-speed industrial induction machine with magnetic bearing suspension. The inductive sensor provides an alternative solution to commercial eddy current displacement sensors. It meets the application requirements and has a robust construction utilizing conventional electrical steel lamination stacks and copper winding.

scholarly journals High-Speed Video Analysis of the Process Stability in Plasma Spraying

2021 ◽  
Author(s):  
K. Bobzin ◽  
M. Öte ◽  
M. A. Knoch ◽  
I. Alkhasli ◽  
H. Heinemann
Keyword(s):  
Plasma Spraying ◽  
High Speed ◽  
Plasma Jet ◽  
Plasma Jets ◽  
Time Dependent ◽  
Acquisition Time ◽  
Fast Fourier Transformation ◽  
Frequency Spectra ◽  
Dependent Signal ◽  
The Stability

AbstractIn plasma spraying, instabilities and fluctuations of the plasma jet have a significant influence on the particle in-flight temperatures and velocities, thus affecting the coating properties. This work introduces a new method to analyze the stability of plasma jets using high-speed videography. An approach is presented, which digitally examines the images to determine the size of the plasma jet core. By correlating this jet size with the acquisition time, a time-dependent signal of the plasma jet size is generated. In order to evaluate the stability of the plasma jet, this signal is analyzed by calculating its coefficient of variation cv. The method is validated by measuring the known difference in stability between a single-cathode and a cascaded multi-cathode plasma generator. For this purpose, a design of experiment, covering a variety of parameters, is conducted. To identify the cause of the plasma jet fluctuations, the frequency spectra are obtained and subsequently interpreted by means of the fast Fourier transformation. To quantify the significance of the fluctuations on the particle in-flight properties, a new single numerical parameter is introduced. This parameter is based on the fraction of the time-dependent signal of the plasma jet in the relevant frequency range.

3D Profile Variety Measurement of Pectoral Fin in Fish Fast Start

2011 ◽  
Vol 83 ◽  
pp. 280-284
Author(s):  
Ming Jiang ◽  
Shu Zhang ◽  
Xiao Yuan He
Keyword(s):  
Fourier Transform ◽  
High Speed ◽  
Kinetic Characteristic ◽  
Three Dimensional ◽  
Pectoral Fin ◽  
Fourier Transform Profilometry ◽  
Fast Start ◽  
Fringe Patterns ◽  
3D Information ◽  
3D Profile

Fast-starts are brief, sudden accelerations used by fish during predator-prey encounters. In this paper, a three-dimensional (3D) test and analysis method is critical to understand the function of the pectoral fin during maneuvers. An experiment method based on Fourier Transform Profilometry for 3D pectoral fin profile variety during fish maneuvers is proposed. This method was used in a carp fast-start during prey. Projecting the moiré fringes onto a carp pectoral fin it will produce the deformed fringe patterns contain 3D information. A high speed camera captures these time-sequence images. By Fourier transform, filter, inverse Fourier transform and unwrap these phase maps in 3D phase space, the complex pectoral fin profile variety were really reconstructed. The present study provides a new method to quantify the analysis of kinetic characteristic of the pectoral fin during maneuvers.

Dynamic characteristics of a drill in the drilling process

2003 ◽  
Vol 217 (2) ◽  
pp. 161-167 ◽  
Author(s):  
B W Huang
Keyword(s):  
Dynamic Characteristics ◽  
High Speed ◽  
Thrust Force ◽  
Time Dependent ◽  
Drilling Process ◽  
Improve Quality ◽  
Vibration Model ◽  
High Speed Drilling ◽  
Spinning Speed ◽  
Twisted Beam

The dynamic characteristics of high-speed drilling were investigated in this study. To improve quality and produce a higher production rate, the dynamic characteristics of the drilling process need to be studied. A pre-twisted beam is used to simulate the drill. The moving Winkler-type elastic foundation is used to approximate the drilling process. A time-dependent vibration model for drilling is presented. The spinning speed, pre-twisted angle and thrust force effects of the drill are considered. The numerical analysis indicates that the natural frequency is suddenly reduced as the drill moves into a workpiece.

An improved model for investigating the vibration characteristics of ball bearing owing to outer race waviness under high speed

2021 ◽  
Vol 69 (2) ◽  
pp. 89-101
Author(s):  
Pingping Hou ◽  
Liqin Wang ◽  
Zhijie Xie ◽  
Qiuyang Peng
Keyword(s):  
High Speed ◽  
Ball Bearing ◽  
Vibration Measurement ◽  
Vibration Frequencies ◽  
Outer Race ◽  
Response Characteristics ◽  
Lagrange’S Equation ◽  
Rolling Elements ◽  
Initial Clearance ◽  
Improved Model

In this study, an improved model for a ball bearing is established to investigate the vibration response characteristics owing to outer race waviness under an axial load and high speed. The mathematical ball bearing model involves the motions of the inner ring, outer ring, and rolling elements in the radial XY plane and axial z direction. The 2Nb + 5 nonlinear differential governing equations of the ball bearing are derived from Lagrange's equation. The influence of rotational speed and outer race waviness is considered. The outer race waviness is modeled as a superposition of sinusoidal function and affects both the contact deformation between the outer raceway and rolling elements and initial clearance. The MATLAB stiff solver ODE is utilized to solve the differential equations. The simulated results show that the axial vibration frequency occurred at l fc and the radial vibration frequencies appeared at l fc fc when the outer race waviness of the order (l) was the multiple of the number of rolling elements (k Nb) and that the principal vibration frequencies were observed at l fc fc in the radial x direction when the outer race waviness of the order (l) was one higher or one lower than the multiple of the number of rolling elements (k Nb 1). At last, the validity of the proposed ball bearing model was verified by the high-speed vibration measurement tests of ball bearings.

Noncontacting Vibration Measurement Using a Massless Interferometric Accelerometer

1995 ◽  
Author(s):  
Keyu Li
Keyword(s):  
Elevated Temperatures ◽  
Laser Light ◽  
Vibration Measurement ◽  
Object Surface ◽  
Out Of Plane ◽  
Plates And Shells ◽  
Fringe Patterns ◽  
Hostile Environments ◽  
Derivatives Of ◽  
Object Behavior

Abstract An interferometric strain measurement technique is extended to vibration measurements. The technique is based on two micro-indentations placed on an object surface using a combination of diffraction and interference of laser light. Relative displacements between the two indentations and derivatives of in-plane and out-of-plane vibrational displacements are measured by analyzing the phase shift of the interference fringe patterns. The technique can be used to study bending stress and deflection problems in vibrational beams, plates and shells. The displacement derivatives are measured in real time, from which time derivatives or the velocity and acceleration of the displacement derivative as well as vibrational frequency can be determined. The technique has advantages over an accelerometer in that it is noncontacting and does not require attachment of the transducer to the object which could alter the object behavior. In addition, it has many desirable features such as being extremely compact, massless, and applicable to hostile environments such as those associated with production and elevated temperatures.

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