A Question about Hydraulics

Discussion in 'Off-Topic' started by jpanhalt, Dec 19, 2014.

  1. jpanhalt

    Thread Starter AAC Fanatic!

    Jan 18, 2008
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    I have a Komatsu PC35MRX with a little over 2000 hours. It looks like this, which just a picture off the web and not my machine.

    upload_2014-12-19_17-52-1.png

    I have gotten pretty comfortable operating it, but pulling the bucket across a surface to level it is somethingI have not mastered. In fact, I am lousy at it.

    So, I am thinking of putting accelerometers on the boom and dipper, which will tell me, for example, how much to raise or lower the boom to accommodate for the arc of the dipper as I pull it across a surface.

    The hydraulic controls are typical manual spool valves. My question is this: What exists in an electrically controlled valve with manual override, and what is it called?

    A simple approach might be to add a servo, but then such servos don't allow easy override, even when not powered. One way around that would be to have an electrically engaged clutch on the servo. But. I am looking for other ideas. I don't want to impede digging and other things, but I need help level scraping. I have seen operators who can do that by sight, but I just don't have that skill. Consider it an ADA type of adaptation.

    John
     
  2. Alec_t

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    Er, isn't this a banned topic here? Nice toy, though, John. I'm envious.
    Try googling "directional control valve solenoid manual".

    I'm thinking knocks and vibration will confuse accelerometers. Would arm angle be a more reliable parameter?
     
    Last edited: Dec 19, 2014
  3. killivolt

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    I think Ian Rodgers can answer that question on ETO.

    kv
     
  4. jpanhalt

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    Probably, but I think Ian deals with MUCH larger equipment.

    As for being a banned topic on AAC, this is not automotive and not inherently dangerous. There are so many safety interconnects on modern construction equipment that you cannot adjust yourself for a good f*** without the whole thing shutting down.

    John
     
  5. jpanhalt

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    It is definitely a nice toy, but you can do a lot of damage in a short time. I helped the local forestry people clear a log jam on the river last Summer. Got some good black walnut logs as a freebie for the effort.

    I have not assessed the vibration aspect yet. The accelerometer I am using is effectively immune to shock and seems to have a reasonably short settling time. Once I test it on my tractor (another thread) I will have a better idea of the effects of short-term vibration.

    John
     
  6. MaxHeadRoom

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    On a robotic machine it would be interpolated motion, which involves servo's and feedback etc.
    Normally the operator is the feedback and control loop. ;)
    Max.
     
  7. #12

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    Do we have a smiley for, "That went completely over my head"? :D
     
  8. MaxHeadRoom

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    Interpolated motion.

    Max.
     
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  9. killivolt

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    This is how the terminator started out. :p

    You think I'm kidding:cool:

    I'll be back lol

    kv

    Edit: Sorry; I couldn't resist. I had a Pumpkin Stout a minute ago while ripping up some 13 year old carpet. Arrrg; but it will look nice for christmas lady's.
     
  10. JoeJester

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    The ping pong match was classic.

    Upon making that billiard shot, the robot was over jubilant.
     
  11. strantor

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    What kind of valves are on your machine? Some brands are highly customizable, with different options for actuation. For example I'm working with danfoss PVG32 valves on a project currently. I can pop out a 20gpm closed center spool and put in a 30 gpm float spool, I can remove 4 bolts and swap a dual-coil bang-bang solenoid coil operator for a 0-10v proportional operator with integrated lvdt closed loop position control and a pressure compensation, or a PWM version with no lvdt, etc on and on, endless possibilities. And no matter what spool I choose, on the other end of the block I can attach a manual handle. If your valves offer the same kind of flexibility, you could potentially just add some form of electrical actuation to your existing manual controls without much fuss. From there, a trifecta of linear position sensors and some flavor of digital brain to do the trig and control the valves, and you should be on your way.

    But this stuff is nowhere near the realm of "affordable" for most people. but most don't people don't own their own backhoe, so maybe I should say "practical." For the price it would cost to do what I've described above, using the danfoss valves that I'm familiar with the pricing on, you could contract a skilled operator for a week to run your backhoe, or a professional instructor to come out to your location and teach you how to do it properly, plus a couple of truckloads of loose dirt to practice with.
     
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  12. Alec_t

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    :confused: I thought the only purpose of an accelerometer was to detect shock? ;)
     
  13. tcmtech

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    The only real solution is to simply put the time in and practice it.

    Technology is not the answer for everything. Sometimes a person actually has to work at something to become good at it. :oops:
     
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  14. jpanhalt

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    The shock specification for the MXD2020EL is >50,000 g. Its detection range is ±1 g.

    John
     
  15. jpanhalt

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    I am not sure of the valve brand used on the excavator. It is definitely in segments like you describe, but I don't think that is unique to Danfoss. Even the bolts on this machine are stamped with the Komatsu logo, so I suspect the hydraulic valves are too. They are relatively had to get access to, but are still accessible for adjustment. BTW, this is a small 3-1/2 ton machine. Parts are expensive, but in a different ballpark than for the bigger machines.

    Right now, I am just wondering what sort of things would be available. Now I know some words to use when looking. I consider it is unlikely I will mess with the spool valves, it is a very tight space -- I had to modify a wrench just to adjust the accessory pressure. But still, that option has not been completely discarded.

    John
     
  16. atferrari

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    IIRC, cranes.
     
  17. Brownout

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    I wouldn't think accelerometers would be helpful at all. I'm with Max, the important measurement would be at each pivot point. By measuring these angles, you should be able to come up with a algorithm to keep the bucket at a predetermined height. As for valves, I'll just read what more informed members have to say about it. I've actually entertained the idea of automating my own backhoe.
     
  18. BR-549

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    When I was a young man, I operated an old Link Belt Speeder 45' cable drag line. Both feet and hands are busy all the time.

    I don't think you'll ever learn to grade with that outlook.

    The only way to grade is by the feel of the machine(inertia), the feedback on the controls, and the sound of the machine.

    It takes practice. It's like driving. Once you get it down, you can grade all day while daydreaming to keep from getting bored.

    Once you learn how to get the feel for one machine, you can acquire the feel of another quickly.
     
  19. tcmtech

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    Yep. What he said.

    Sometimes you just have to put the time and effort in to get good at something.;)
     
  20. jpanhalt

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    @BR-549
    @tcmtech

    To Both:

    I find your comments to be completely off topic and insulting. Did you understand my post? Did you put any effort into actually trying to answer my question or contribute positively?

    My question was not about something I plan to do tomorrow or even in the future. I made that clear. With over 4000 posts and many hours of effort put into AAC, I think I have at least earned the right to "think out loud" very occasionally and get serious responses by those who have knowledge in the field of my question. At a minimum, you should realize that I am not a slackard, nor do I expect to be adept at something without practice.

    Most of all, I object to being lectured on how to be successful by a couple of anonymous hecklers. What have either of you done to qualify for that position?

    Regards, John
     
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