KEYWORDS: Algorithm development, Clouds, Tolerancing, Control systems, Sensors, 3D metrology, Detection and tracking algorithms, 3D modeling, Laser development, Spatial filters
The purpose of this research is to develop a new means of identifying and extracting geometrical feature statistics from a
non-contact precision-measurement 3D profilometer. Autonomous algorithms have been developed to search through
large-scale Cartesian point clouds to identify and extract geometrical features. These algorithms are developed with the
intent of providing real-time production quality control of cold-rolled steel wires. The steel wires in question are prestressing
steel reinforcement wires for concrete members. The geometry of the wire is critical in the performance of the
overall concrete structure.
For this research a custom 3D non-contact profilometry system has been developed that utilizes laser displacement
sensors for submicron resolution surface profiling. Optimizations in the control and sensory system allow for data points
to be collected at up to an approximate 400,000 points per second. In order to achieve geometrical feature extraction and
tolerancing with this large volume of data, the algorithms employed are optimized for parsing large data quantities. The
methods used provide a unique means of maintaining high resolution data of the surface profiles while keeping algorithm
running times within practical bounds for industrial application.
By a combination of regional sampling, iterative search, spatial filtering, frequency filtering, spatial clustering, and
template matching a robust feature identification method has been developed. These algorithms provide an autonomous
means of verifying tolerances in geometrical features. The key method of identifying the features is through a
combination of downhill simplex and geometrical feature templates. By performing downhill simplex through several
procedural programming layers of different search and filtering techniques, very specific geometrical features can be
identified within the point cloud and analyzed for proper tolerancing. Being able to perform this quality control in real
time provides significant opportunities in cost savings in both equipment protection and waste minimization.
This paper presents a portable optical sensor capable of measuring complex multi-axis strain fields without the need for special surface preparation or stringent sensor-to-surface alignment. The sensor consists of three to four electronic
speckle photography (ESP) modules. The design of each modular element is based on a previously developed 5-axis
(five degree of freedom) surface displacement measurement technique, and is able to measure two dimensional in-plane surface movement, unaffected by other degrees of freedom (displacement and rotation) movement. Identical modular strain elements are arranged in a Rosette grid layout so that accurate and robust multi-axis surface strain measurement can be achieved.
Experiments were conducted to demonstrate the multi-axis strain field measurement capability of this optical sensor by
using a test bed that provided a known directional planar strain field, and excellent results were obtained. In particular, experiments have shown that the principle strain can be accurately extracted independent of the orientation of the device. This portable optical sensor will allow precise non-contact measurement of practical complex strain fields such as those encountered in bridge abutments, and portions of beams near critical infrastructure support locations; in other words, wherever plane strains depart from uni-axial behavior. Its unique hand-held portable capability offers distinct advantages over laboratory strain measurement setups, allowing accurate robust non-contact measurements to be achieved even in a harsh field application environment.
This paper describes a novel optical system capable of measuring 5-axis (five degrees of freedom) object surface movement without the need for special surface preparation or stringent alignment. The compact optical system is based on electronic speckle photography (ESP) and is designed to be insensitive to out-of-plane movement. Experiments were conducted to measure the 5-axis motion simulated by a 6-axis motion system. The results show that the optical system accurately resolves the motion on every axis successfully, with the expected insensitivity to out-of-plane displacements. A possible application of the technique in strain measurement is also addressed in the paper.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.