Application of Terrestrial Laser Scanner in Particle Accelerator

and Reverse Engineering Solutions D. Bianculli - D. Humphries

Accelerator Survey & Alignment Group

LBNL – Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA

Terrestrial Laser Scanners can collect a million points per second and it is a technology widely used in fields such as: topography, forensics, building, mining, as-built surveying,

architecture, archaeology, monitoring, civil engineering and urban modeling. Because of beamline operations, access to the storage ring is restricted to approximately two days every two

weeks: so a laser tracker system is too time consuming. A terrestrial laser scanner was used to collect point cloud data and High Dynamic Range images of the inner wall of the Advanced

Light Source particle accelerator main storage ring tunnel. Sub-millimeter accuracy registration of multiple setups was performed using sphere shaped targets in an existing monument

network previously surveyed by laser tracker. Data was exported in a web-based point cloud with HDR images. Direct surface reconstructions in Autodesk Inventor 3D CAD provide a

parametric solid model of all significant features such as wire ways, pipelines, air ducts and electrical boxes. A validation analysis was conducted comparing the constructed model to the

actual tunnel wall by laser tracker.

INSTRUMENT

TARGETS

EXPERIMENTAL METHOD

WEB-BASED DELIVERABLE

3D CAD MODELING

FROM ALS... ...TO ALS-U

LEICA SCANSTATION P20 • Accuracy of single measurement 3D Position Accuracy 3 mm at 50 m; 6 mm at 100 m Linearity error ≤ 1 mm Angular accuracy 8” horizontal; 8” vertical • Target acquisition Algorithmic fit to planar B&W targets 2 mm standard deviation up to 50 m • Dual-axis compensator Selectable on/off, resolution 1”, dynamic range +/– 5’, accuracy 1.5” • Maximum range 120 m

Hemispherical 5 inches diameter white targets are built with the

center of the hemisphere coincident with the center of a steel

1.5” ball so that they can be used in magnetic drift-nests.

Therefore regardless of how the target is mounted on a

kinematic nest, its center does not change position. Targets were

inspected by portable CMMs and the centering accuracy

determined to be below 100µm.

• 41 stations have been setup at strategic locations around the storage ring

• Each station was levelled and hemispherical targets were scanned

• Existing network was used with floor and wall monuments surveyed by laser tracker

• For each of these targets a double face measurement was performed and spheres were best-fitted.

• Point cloud resolution was set at 6.3mm @10m distance with a quality level of 3.

• Full dome point cloud scanning: 360° horizontal and +90°/-55° vertical field of view

• High Dynamic Range (HDR) pictures were taken at the highest available resolution of 1920x1920 pixels.

For each shot, three images were taken with different exposures within a field of view of 17°x17°.

• Targets acquisition, point cloud scanning and imaging took about 40 min for each station

with two operators working in the field.

• Total raw data in the hard drive was 34 GB.

• Data imported into Cyclone and registration of all setups based on targets with RMS error of only 680 µm

• Cyclone-PUBLISHER encodes the original point

clouds data and merge them with HDR pictures

• Data visible in Internet Explorer and TruView plug-in

• Using the free Leica TruView panoramic point cloud

viewer, users can view, zoom in, or pan over point

clouds naturally and intuitively

• Users can measure and mark distances picking pairs

of points as if they were measuring in the real space

by a tape measure

• ETRUVIEW = ESCANNER + EENCODING

• Select a subset of the complete point

clouds

• Index in Autodesk ReCap

• Import into Autodesk Inventor

• Create work planes and editable

sketches of object profiles using point

clouds directly as a reference to

obviate meshing

• Utilize extrusion and revolution from

sketches to create solid objects

• ALS-Upgrade is a major conversion of the existing ALS to a diffraction limited

synchrotron light source

• For cost reduction existing shielding walls of the storage ring and user beamlines are

maintained while most accelerator components inside the existing tunnel will be

replaced

• An accumulator ring will be added and placed on the inner side wall of the storage

ring tunnel

• An as-built 3D-CAD model with details of all infrastructure will be necessary for the

design phase

• Create a database of parametric

objects: switches, wire ways, air

ducts, pipes, struts etc

• Visually position solid objects to

match the correspondent point cloud

representation

• Export in STEP file

• Laser tracker survey of the same features

created in CAD

• Import CAD model into Spatial Analyzer

• Comparison of correspondent objects

positioning and orientation

• Max displacement error = 2.4 mm

• Max orientation angle = 0.25 deg

VALIDATION