Page 4 of 5 FirstFirst ... 2345 LastLast
Results 31 to 40 of 44

Thread: GPS type technology for machine slide position ?

  1. #31
    Join Date
    Jan 2003
    Location
    Deep in the Heart of Texas!
    Posts
    7,633

    Default

    I would think the RF wavelength necessary to provide any accuracy at such small distances would place you seriously close to radiation wavelengths. I sure wouldn't want to wear a lead suit every time I needed to use the lathe or mill.

  2. #32
    Join Date
    Dec 2015
    Location
    Chilliwack, BC, Canada
    Posts
    4,416

    Default

    Quote Originally Posted by CCWKen View Post
    I would think the RF wavelength necessary to provide any accuracy at such small distances would place you seriously close to radiation wavelengths. I sure wouldn't want to wear a lead suit every time I needed to use the lathe or mill.
    The wavelength does not need to be that high if the return pulse signal is examined for phase shift. Otherwise you're right and if it were based on full length of a wave then .0025mm resolution as a full single wavelength is actually in the infrared range at 2,540 nm. So not lead but perhaps a reflective silver suit

  3. #33
    Join Date
    Jun 2004
    Posts
    999

    Default

    Quote Originally Posted by Edwin Dirnbeck View Post
    I obviously made a mistake by mentioning gps in the title of my post.Most of the replies seem to be fixated on a complete 3 axis system controlled by some transponders up in the air somewhere. I am thinking of 1 transponder and 1 receiver per axis all located ON THE MACHINE and sheided from chips. Edwin DIRNBECK
    You still need 3 satellite signals for a position, it doesn't get simpler Just because you decide to measure along a straight line!
    If you benefit from the Dunning-Kruger Effect you may not even know it ;-)

  4. #34
    Join Date
    Nov 2008
    Location
    SF East Bay.
    Posts
    6,070

    Default

    I suppose that if all you want is the distance between point A and B, then one transmitter and one receiver will work... Until something gets in the way. Or if there is electrical noise. But echo reflection should work. It would still require the same technology as the scales to protect the space between the transmitter and receiver. It might even be more complex.

    Dan
    Measure twice. Cut once. Weld. Repeat.
    ( Welding solves many problems.)

  5. #35
    Join Date
    Jan 2004
    Location
    Missouri
    Posts
    29,748

    Default

    Quote Originally Posted by Magicniner View Post
    You still need 3 satellite signals for a position, it doesn't get simpler Just because you decide to measure along a straight line!
    Actual GPS was NOT envisioned as the means of position determination..... The OP said that, and we can presume that he wishes to separate the axes as a DRO does, but NOT have any large housing for a scale etc on each axis.

    It seems that the "need" does not exist for this device in general use, or at least a need sufficient to justify the probable cost has not been clearly stated.

    It is OBVIOUSLY "possible" to do, "you just count wavelengths" of the frequency necessary to get the resolution you need. The very precise calibration folks do that all the time to check precision gage blocks. Note that this "possibility" does not include any of the "practical" considerations needed to make it work reliably on machine. I believe, however, that it IS in fact done with the machines used to cut very precise telescope mirrors, and may be done for other high precision optical purposes.
    1601

    Keep eye on ball.
    Hashim Khan

  6. #36
    Join Date
    Jun 2004
    Posts
    999

    Default

    Quote Originally Posted by J Tiers View Post
    Actual GPS was NOT envisioned as the means of position determination..
    No, he said GPS type, that means a receiver comparing timing of at least 3 signals from known positions and comparing the difference in timing to calculate a position.
    If you benefit from the Dunning-Kruger Effect you may not even know it ;-)

  7. #37
    Join Date
    Jan 2004
    Location
    Missouri
    Posts
    29,748

    Default

    Quote Originally Posted by Magicniner View Post
    No, he said GPS type, that means a receiver comparing timing of at least 3 signals from known positions and comparing the difference in timing to calculate a position.
    To YOU it does.

    It seems pretty obvious he meant a "non-contact" system, of some sort, that has no long scales or readers dragging along with the slides as a standard DRO does. Reading the position by some sort of "beam", not a physical object.

    Strict literal ("legal") interpretation of someone's words is not useful when they are themselves not sure of exactly what they really mean
    Last edited by J Tiers; 10-11-2018 at 10:09 AM.
    1601

    Keep eye on ball.
    Hashim Khan

  8. #38
    Join Date
    Jan 2013
    Location
    Michigan
    Posts
    1,474

    Default

    A camera pointing downward on the lathe bed would provide a 'dro' capability of sorts. It could be built for almost nothing and coded any number of ways. OpenCV is one way. Lasers can be used for a different type of reference.

    https://www.pyimagesearch.com/2016/0...e-with-opencv/

  9. #39
    Join Date
    Feb 2011
    Posts
    755

    Default

    Quote Originally Posted by Magicniner View Post
    No, he said GPS type, that means a receiver comparing timing of at least 3 signals from known positions and comparing the difference in timing to calculate a position.
    Like I said,I should NOT HAVE USED THE TERM ,GPS IN THE TITLE OF MY POST. I am only refering to that part of the technology that enables the receiver to measure the distance between itself and ONE SATELITE (RCIEVER). I understand that the GPS SYSTEM need to calculate the distance to 3 or more satelites in order to get a polar coordinate position.Once again I am talking about one axis and one sending and one recieveing unit.I know this sounds silly because we have cheap scale units.This technology is 40 years old and virtually unchanged. Meanwile the rest of the world marches on . My nephew was at a multi million dollar complex that was built so that people could sit on a couch and drink hiballs and watch each other wack golf balls and you guesed it ,the balls had tiny rfi chips in them for aproxamate location and they have coming gps golf balls to track the tragectery. I personally have zero use for games,but that seems to be where the technology goes. Edwin Dirnbeck
    ,

  10. #40
    Join Date
    Nov 2008
    Location
    SF East Bay.
    Posts
    6,070

    Default

    Radio seems like a good way to do it, but it really does need a clear line of sight to be reliable.

    As an example of what I mean I'll use GPS. When looking for a geocache located next to a sheet metal building I had the strangest problem. The GPS said the location was 10 feet of the building, but as I approached the building the reading changed and said I should be 15-20 feet from the wall. The signal was reflecting from the metal skin of the building.

    That should be easy to fix, right? All you need to do is make sure that nothing gets between the sender and receiver. Some sort of tube maybe? But it would need to be very well sealed. A single chip in the path could cause errors. But doable. Not sure that it would be better or easier than the best glass scales.
    Measure twice. Cut once. Weld. Repeat.
    ( Welding solves many problems.)

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •