This design is under construction. A first trial was performed by Tibi to test the integrity of the mechanical assembly. 6 fibers are used around a center fiber. All fibers have the same diameter, 1mm. The structure is stable and the 6 outer fibers are distributed almost uniformly. Only 3 out of these 6 fibers will be used to carry light to the detectors. The center fiber brings light into the gap.
|Record created date||April 23, 2013|
|Record created by||None|
We don't know.
Before I start working on this project I review and restructure documentation - website and docs
I also communicated to SENSORICA about my work.
Project page link
Main doc link
There are a lot of docs that need to be updated around the Tape Sensor.
Optical Design - Tape sensor one in (glass) 3 out (PMMA)
with the melted glass fiber tip for a smaller exit cone within the gap.
Received the order from Thorlabs and assembled the optical fibers (3 out 1mm PMMA and 1 in, 125/62.5 glass) together.
It is not easy to assemble these fibers. I attached the together using a think metal wire. I also put them on a metal bar, but I am not too satisfied with that. Need another bar, probably with a groove in it. Also, the gap is not straight, the joint tube is a little too flexible.
The joint tube is a 2mm diameter transparent shrinking tube. No need to shring the tube around, it is tight enough.
I also prototypeed 7 fiber 250um diameter PMMA fiber, using a shrinking tube to hold them together. We already tried this structure using the 1mm PMMA fiber, and it is quite stable. I polished these fibers and it looks good.
I worked with Jonathan on the Tape Sensor.
I assembled the rod, from a cylindrical piece of wood, approx 1m long, which I had so buy. I made a groove in it using the Dremel.
I completed the prototype - glued the optical fibers in the groove of the wooden rod, sanded the rod and inserted it into the aluminum tube. Before inserting it into the aluminum tube we tested the prototype, and it seamed to work well. Some optical fiber preparation (cleaning) was required before connecting the fibers to the PDs and the LED. After the wooden rod was inserted into the aluminum tube I tested the device again. The sensor still works. We need now to find its axis. I also thought about the algorithm to extract the spatial information from the 3 intensities measured on the 3 PMMA collector fibers.
Jonathan helped mounting the PD on the circuit.
Microscopes were used for fiber preparation and for gap alignment inside the groove made in the wooden rod.
I continued to work on the demo for Zhu, which was dues on Friday - the day after.
I wrote the equations to extract spatial information from 3 intensities (need to scan the calculations and put them online!)
See document about the mathematical model and simulations
The LabView program (used for acquisition, data processing and display) required some modification, and the equation needed to be implemented - coded in the LabView program.
After these modifications I moved the setup on a different table that we chose for the demo, and wired everything.
I started testing the device and I encountered some problems. No spatial information could be extracted and the data made no sense within the model we were using.
I tried other ways to extract spatial information from the data, but things did not improve.
I discussed with Ivan and Daniel about the problem, and we realized that our model about the prototype was wrong. It turned out that compression and stretch of the joint were dominating the effects. The mirror tilting was was too small to be detected.
The 3 fibers ware applied off center within the aluminum tube. The intensity fluctuations with vending were max if the bending was done on plane containing the fibers. If the device was rotated fibers were 90 degrees no signal was detected.
So it turns out that this prototype doesn't work as expected, but this gave us other ideas about the hockey stick project (see smart sports equipment).