11,814 research outputs found
Accurate particle position measurement from images
The moment method is an image analysis technique for sub-pixel estimation of
particle positions. The total error in the calculated particle position
includes effects of pixel locking and random noise in each pixel. Pixel
locking, also known as peak locking, is an artifact where calculated particle
positions are concentrated at certain locations relative to pixel edges. We
report simulations to gain an understanding of the sources of error and their
dependence on parameters the experimenter can control. We suggest an algorithm,
and we find optimal parameters an experimenter can use to minimize total error
and pixel locking. Simulating a dusty plasma experiment, we find that a
sub-pixel accuracy of 0.017 pixel or better can be attained. These results are
also useful for improving particle position measurement and particle tracking
velocimetry (PTV) using video microscopy, in fields including colloids,
biology, and fluid mechanics.Comment: 8 pages, 17 figure
Standard Quantum Limits for broadband position measurement
I utilize the Caves-Milburn model for continuous position measurements to
formulate a broadband version of the Standard Quantum Limit (SQL) for
monitoring the position of a free mass, and illustrate the use of Kalman
filtering to recover the SQL for estimating a weak classical force that acts on
a quantum-mechanical test particle under continuous observation. These
derivations are intended to clarify the interpretation of SQL's in the context
of continuous quantum measurement.Comment: Replaced version: changed title, fixed algebra error at the very end,
conclusions modified accordingly. Four pages, one eps figur
Arm Position Measurement
This capstone project addresses the design and implementation of a device that measures arm position and speed. The device is intended for use in conducting further research on the motion of limbs affected by cerebral palsy, and in the prototypic development of a device that could help control such motion, thereby allowing a user to accomplish daily tasks. This project includes the design of an appropriate experiment and testing apparatus to explore possible solution prototypes, along with suggested methods to perform analysis of the experiment results. This is considered to be the fundamental research necessary to better understand the scope and requirements that a prototype design would need. The results of this experimental research will provide recommendations for moving forward in the development of an Arm Stabilizer device
Linear motor for multi-car elevators, design and position measurement
Multi-car elevator is an emerging technology consisting of two or more elevator cars moving independently in an elevator hoistway, which has become more appealing as building heights increase. In this paper, the design and drive methodologies for a linear motor driven multi-car elevator system with independently moving cars is introduced together with experimental results. Additionally, a safety method developed for the linear motor elevator and the conditions necessary for its proper operation are discussed. The new results introduced in this paper are in the areas of the design method of the linear motor for multi-car elevator system, and the preliminary results for the position measurement system
Position Measurement for a Relativistic Particle: Restricted-Path-Integral Analysis
Measurements of the position of a relativistic particle is considered in the
framework of the Restricted-Path-Integral (RPI) approach. The amplitude
describing such a measurement is shown to be exponentially small outside the
light cone of the space-time point corresponding to the measurement output, in
a qualitative agreement with the Hellwig and Kraus' postulate of relativistic
state reduction. Theory of the measurement including the probability
distribution for different measurement outputs is suggested. It is shown that
correct theory does not exist (for arbitrary initial states) if the error of
the measurement is less than the Compton length. The physical reason is that
the picture of measurement is destroyed in this case by pair creation.Comment: 12 pages, LATE
Improved position measurement of nano electromechanical systems using cross correlations
We consider position measurements using the cross-correlated output of two
tunnel junction position detectors. Using a fully quantum treatment, we
calculate the equation of motion for the density matrix of the coupled
detector-detector-mechanical oscillator system. After discussing the presence
of a bound on the peak-to-background ratio in a position measurement using a
single detector, we show how one can use detector cross correlations to
overcome this bound. We analyze two different possible experimental
realizations of the cross correlation measurement and show that in both cases
the maximum cross-correlated output is obtained when using twin detectors and
applying equal bias to each tunnel junction. Furthermore, we show how the
double-detector setup can be exploited to drastically reduce the added
displacement noise of the oscillator.Comment: 9 pages, 1 figure; v2: new Sec.
How to Measure Magnetic Flux with a Single Position Measurement?
Current methods for measuring magnetic flux are based on performing many
measurements over a large ensemble of electrons. We propose a novel method
based on wavefunction "revival" for measuring the flux modulo hc/2e using only
a single electron. A preliminary analysis of the feasibility of the experiment
is provided.Comment: Improved version. Accepted for publication in EP
3-D Velocity Regulation for Nonholonomic Source Seeking Without Position Measurement
We consider a three-dimensional problem of steering a nonholonomic vehicle to
seek an unknown source of a spatially distributed signal field without any
position measurement. In the literature, there exists an extremum seeking-based
strategy under a constant forward velocity and tunable pitch and yaw
velocities. Obviously, the vehicle with a constant forward velocity may exhibit
certain overshoots in the seeking process and can not slow down even it
approaches the source. To resolve this undesired behavior, this paper proposes
a regulation strategy for the forward velocity along with the pitch and yaw
velocities. Under such a strategy, the vehicle slows down near the source and
stays within a small area as if it comes to a full stop, and controllers for
angular velocities become succinct. We prove the local exponential convergence
via the averaging technique. Finally, the theoretical results are illustrated
with simulations.Comment: submitted to IEEE TCST;12 pages, 10 figure
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