Looking for ideas on how to track movement
Looking for ideas on how to track movement
(OP)
I would like to track the movement of a part over a 1-2' arc as part of a durability test on components that are moved by motors. The motors turn about 90 degrees and the components travel in 1-2' arcs. The motors are actuated in extreme environments (-40C, 60C/80%RH, salt humidity, dust) for several days or weeks at a time.
I would like to produce graphs showing the speed of the moving component as a function of time so that any speed fluctuations that occur while the motor is running can be realized. Tracking the position with a resolution of an inch or better would be ideal.
Would RFID be useful in this application? I am curious what technology is used in the making of computer-animated films, where sensors are mounted to people and the movement is then reproduced on computer screens. I’ve considered machine vision but expect integrating it in extreme environments will be difficult.
Currently I have a system setup that monitors the extreme positions of the moving components using magnetic sensors and magnets mounted on the moving components. I’ve thought about mounting extra magnetic sensors but am hoping to come up with something better.
Any ideas will be appreciated!
Thanks,
Dave
I would like to produce graphs showing the speed of the moving component as a function of time so that any speed fluctuations that occur while the motor is running can be realized. Tracking the position with a resolution of an inch or better would be ideal.
Would RFID be useful in this application? I am curious what technology is used in the making of computer-animated films, where sensors are mounted to people and the movement is then reproduced on computer screens. I’ve considered machine vision but expect integrating it in extreme environments will be difficult.
Currently I have a system setup that monitors the extreme positions of the moving components using magnetic sensors and magnets mounted on the moving components. I’ve thought about mounting extra magnetic sensors but am hoping to come up with something better.
Any ideas will be appreciated!
Thanks,
Dave





RE: Looking for ideas on how to track movement
If not, then you need something else.
The human-to-computer thing is/was(?) often done using IR diodes and a 2D sensor that outputs two voltages proportional to X and Y position. The IR easily penetrates dirt, but the detector needs protective flow of air - and an occasional water spritz now and then.
Gunnar Englund
www.gke.org
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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...
RE: Looking for ideas on how to track movement
If you are measuring an angle, can you just put a rotary encoder on the motor?
RE: Looking for ideas on how to track movement
I can not disassemble the parts to access the motor or shaft unfortunately. Mounting a rotary potentiometer on the outside of the part presents only mounting problems so I'll give that some more thought.
I researched the computer-animation motion tracking that I first asked about, "motion capture" seems to be the correct term for it. A magnetic motion capture system that can be purchased with only 1 sensor (instead of enough for body movement) designed for 2D looks like it might do the job well but I'm not sure where to find such a thing.
RE: Looking for ideas on how to track movement
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Sometimes I only open my mouth to swap feet...
RE: Looking for ideas on how to track movement
Without these answered, you cannot get a relevant solution.
TTFN
RE: Looking for ideas on how to track movement
TTFN
RE: Looking for ideas on how to track movement
htt
The latter is a standalone product, while the former is a plug-in for MAC-based Final Cut Studio:
http://www.apple.com/finalcutstudio/finalcutpro/
Note that unless you want to spend lots of money, you're limited to 30 Hz frame rate for image-based systems, which might be insufficient for your application
TTFN
RE: Looking for ideas on how to track movement
RE: Looking for ideas on how to track movement
http://www.equator.ac.uk/index.php/articles/670
http://www.vrdepot.com/vrteclg.htm
Cameras shouldn't be an issue:
http://www.cohu-cameras.com/pdf/3640.pdf
TTFN
RE: Looking for ideas on how to track movement
If you scale it down, try to measure how much (in lenght) the motor shaft rotates and the time it takes to get to the desired position, knowing that you will be able to know your answer.
RE: Looking for ideas on how to track movement
No.
"I am curious what technology is used in the making of computer-animated films, where sensors are mounted to people and the movement is then reproduced on computer screens."
What are mounted to the actors are reflective balls (not sensors). The balls are tracked in 3D using multiple IR cameras.
RE: Looking for ideas on how to track movement
From what I've read that sounds more like optical motion capture...
http://www
htt
http://www.wave-report.com/tutorials/MoTrak.htm
That last site claims line of sight is not required for magnetic. I found a reference to an article discussing speed and position tracking of a catheter (for autonomous insertion)- perhaps just a few sensors rather than a few dozen. Still looking for a place to start with this technology though.
RE: Looking for ideas on how to track movement
TTFN
RE: Looking for ideas on how to track movement
When you consider the cost and dificulty of measuring speed accurately at very low RMPs, it is worth another try.
The resolution of your speed will be so much greater if you measure the motor speed that there is almost no comparison.
If you cannot find an encoder for the motor shaft, you may use a light and sensor to count fan blades passing.
A high quality encoder may give position indication as well as speed.
If a graph of relative operating speed is all that is required you may use a simple RPM indication. As a result of this, we are faced with several problems. Dirt and humidity, and attemting to accurately measure very low operating speeds.
It has been my experience that when one condition of a problem leads to such a magnification of difficulty, it is time to re-evaluate the original condition.
One of the stated conditions of the problem is the unavailability of the motor shaft.
It may be less difficult to modify the restricting condition than to work around it. In this case, try harder to access the motor shaft for measurement. If you are able, a lot of other difficulties will go away and the problem becomes very simple.
respectfully
RE: Looking for ideas on how to track movement
RE: Looking for ideas on how to track movement
I realize the motor shaft would be best for tracking motor movement but I trully need to track the position of the moving component; there are gears and clutches in between and accessing the motor shaft simply isn't an option.
RE: Looking for ideas on how to track movement
They are really easy to install, compared to a vision system!