Long Range UGV

124

Comments

  • Erco, I saw those and wondered how white would look. There were 3 in stock across 2 local stores so I figured I'd pass.

    Mike, I'm hoping the 14" bike tires are hard to get onto the 14" rover tire. I'm hoping some soapy water will get it over the wheel. Then when that water dries up the tire will be so tight on the wheel that a couple of screws, or rivets, will be all we need.

    If there's some slack, thanks for the glue suggestions, we're going to need something to fill the gaps.

  • xanadu wrote: »

    Mike, I'm hoping the 14" bike tires are hard to get onto the 14" rover tire. I'm hoping some soapy water will get it over the wheel. Then when that water dries up the tire will be so tight on the wheel that a couple of screws, or rivets, will be all we need.

    Them are some big wheels.

    A warm tire is easier to work with, than a cold one. Leave them in the sun awhile if they are too tight. Hope they fit without a lot of extra hardware.
  • We have tires! After removing the bead, the tire fits very snug. All you need is a long screwdriver to pop it on.

    At the speeds we're traveling, I think a few rivets will do the job. If they don't, we'll find out and do something else.

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  • so, are we nearing a beach test?
    Jim
  • I think so, the batteries arrived today.

    35 Ah, 20 lbs each. 70 Ah total. On a 30 W panel, on a perfect day that's 2.5 A charge rate, let's call it 2 A. Probably closer to 1.5 A with other stuff running. Split that 1.5 amp between 2 batteries and we're all the way down to 750mA per battery charge rate, on a perfect day.

    Maybe I should call it the Turtle UGV.
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  • Or you can give it an ocasional day off just to sit and sun itself!
    Jim
  • ercoerco Posts: 17,693
    Batteries are for suckers. Eliminating them saves time, money, & weight...

    Just make the world's biggest BEAM solar engine photopopper, where the solar cells charge a cap up to a fixed trigger voltage, then fire through the motors to nudge the rover a bit. Mark Tilden got it right many years ago.

    http://www.beam-online.com/Robots/Circuits/circuits.html
    "When you make a thing, a thing that is new, it is so complicated making it that it is bound to be ugly. But those that make it after you, they don’t have to worry about making it. And they can make it pretty, and so everybody can like it when others make it after you."

    - Pablo Picasso
  • xanaduxanadu Posts: 2,858
    edited April 15 Vote Up0Vote Down
    That's really cool, way too elegant for me lol.

    I put the tires together and fixed the steering. There is still more to do with the steering, it's not quite turning all the way right, and then too far left. I will have to make the bracket adjustable.

    4 rivets per tire. The plastic tire was much thicker than I imagined.

    The traction is great. Here's a video of the turn radius on the good side.



    Pics:

    1. Steering aftermath of last field test
    2. The part of the rover that popped apart when I tried to bend the actuator mount back
    3. Same as #1 but removed (bracket flipped)
    4. The temporary new setup
    5. Batteries strapped it, plan to use only once for beach test
    6. Shot of the tire tires

    Ready for the beach! If anyone has a giant Easter Bunny costume I'll go Sunday.
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  • xanadu wrote: »
    Maybe I should call it the Turtle UGV.



    Turtle in the desert? You have to more amphibian than that. There is a lot of speed in those motors, and if your going to wear a costume, you better be able to run fast too.
    What is the plan in the desert? Store power by day and travel by night? IR headlights don't cost to much to run.
  • Mike, google desert tortoise!
    Jim
  • RS_Jim wrote: »
    Mike, google desert tortoise!
    Jim


    Yah! They even have their own organization.

    http://www.deserttortoise.org

    still say it's quicker than a turtle.
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  • MikeDYur wrote: »
    xanadu wrote: »
    Maybe I should call it the Turtle UGV.

    Turtle in the desert? You have to more amphibian than that. There is a lot of speed in those motors, and if your going to wear a costume, you better be able to run fast too.
    What is the plan in the desert? Store power by day and travel by night? IR headlights don't cost to much to run.

    The plan is to only use motors when the battery is above 12.5 V. That leaves a giant buffer. Otherwise it will have to sit still. The 3G modem and camera will be off most of the time. Everything will rely on 1 master Prop to maintain power.

    There will be some night ops. I have a sweet CCTV camera, it's analog but has 12x optical zoom, can pan 360 and tilt 90. It's heavy and probably sucks a lot of juice. It was free. The issue there is the analog video encoder costs as much as an IP camera. Also I would need to add RS485 for the PTZ controls, and figure out how to control it in SPIN or Prop C.

    If today's test works out;

    1. Finish steering and add feedback pot
    2. Mount Solar Panels
    3. Install Modem and Pi
    4. Install camera mast (PVC tube)
    5. Get camera working
    6. Simulated field test using 3G
    7. Install sensors
    8. Desert
  • A holiday weekend beach mission may not have been the best idea. The beaches are packed. I will test the rover Monday. I'm taking the day off.

    Happy Easter!
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  • Oops!
  • @xanadu, I think it had something to do with the bunny suit.
  • xanaduxanadu Posts: 2,858
    edited April 16 Vote Up0Vote Down
    Those bunny suit pics were supposed to be deleted!

    Change of plans, we're going out to dinner, so I picked a restaurant on the beach. That means setting up the dual batteries and adjusting the steering. A great way to spend a day off, IMO. I did a quick drive around my yard and everything looks good. The interesting part is that the motors don't seem to draw more current with the added traction on the tires. I can't wait to see how it handles sand.

    Pic 1 is the battery arrangement. Topped off the charge on each battery, and connected them. I put another 30 A thermal breaker between the two batteries. It feels weird paralleling big batteries. I haven't done that before. I keep looking at them, waiting for something to explode.

    Pic 2 is the solution to working on the steering. I suspended the front end with a ratchet strap and it made things really easy to work on. So, the steering is done, again. If nothing bends at the beach, it will stay like this.

    T minus 6 hours.
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  • That was fun. Things are better, but nowhere near desert ready. The rover had a lot more traction, and steers nicely. The place we're going in the desert has a harder surface than the beach sand. It was very demanding, and I didn't get stuck. I didn't really go anywhere either. The rubber started working its way off the tires. I will have to use more rivets. The batteries are too far forward. I hope that by moving the batteries back it will be better.

    Here's some sand action -

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  • ercoerco Posts: 17,693
    Fun Easter! 4WD skid steering might work better. Got two more Power Wheels motors?
    "When you make a thing, a thing that is new, it is so complicated making it that it is bound to be ugly. But those that make it after you, they don’t have to worry about making it. And they can make it pretty, and so everybody can like it when others make it after you."

    - Pablo Picasso
  • The technique I used to use when I went fourweeling in the sand was to reduce the tire air pressure to around 10 psi. Oh, I guess that won't work with hard plastic tires! If you are going to run all of the time in sand, I think Erco's suggestion of 4WD is probably necessary. Has anyone evertried 4WD with 4 motors and conventionl stearing?
    Jim
  • PublisonPublison Posts: 9,358
    edited April 17 Vote Up0Vote Down
    RS_Jim wrote: »
    Has anyone ever tried 4WD with 4 motors and conventional steering?
    Jim

    Do it with my Suburban all the time in snow. :) Steering is a little different in 4WD.


    Infernal Machine
  • MikeDYur wrote: »

    BTW: you may have to look into four wheel drive if that sand is too loose.

    Wonder where he got that idea?
  • I would like to try this again with the batteries further aft, and the rubber strapped down better. We have driven 2WD sedans around endlessly, so long as you stay on flat ground. If I run into soft sand I can back out of it. I'm going to move the batteries (which needs to be done either way) and give it another shot, I should have done that before this test.

    If that doesn't work well, in the absence of proper tires, 4WD will be the only option left. I can't find 14" paddle tires, and even if I could I'm sure they would cost too much. The question I have is would skid steering work? I feel like it would just dig holes. Keeping the current steering config and adding power to the front wheels seems harder to do, do you think it would work any better?

    I have weeks of waiting for misc eBay electronics before it's going anywhere so the pressure is off. At least I have a picture of the rover valet parked at my favorite restaurant :)
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  • xanaduxanadu Posts: 2,858
    edited April 17 Vote Up0Vote Down
    I found a set of wheel drive hubs, and an axle for $20. I have the original set of motors. I may as well go 4WD now. There would be less chance of steering mechanism breaking. I would also get out of adding feedback on the actuator. I guess I'll just move the batteries and wait for the parts.

    https://tigerimports.net/sunshop/index.php?l=product_detail&p=14979
    https://tigerimports.net/sunshop/index.php?l=product_detail&p=10494

    My motor controller is 9 A continuous, and 30 A max per channel. That may not work well for AWD. The motors stall around 3 A, yet 2 of them will trip a 20 A breaker. It's hard to tell what is really needed without some kind of data logging, so I guess now would be a good time to get that going.

    Edit; according to the diagram, the outer rims for front and rear are different. It's obvious from the axle size, but I didn't see them on the same site so I had to order them elsewhere.

    http://www.ereplacementparts.com/rim-rear-outer-p-627664.html?
  • Do it with my Suburban all the time in snow. Steering is a little different in 4WD.
    really, your Suburban has 4 independent motors!
  • The AWD parts will be here middle of next week. Lame.

    In the meantime what obstacle avoidance sensors should I use?

    I'm thinking Sharp IR all around, they're small and waterproof. I played around with the eBay China ultrasonic parking sensors and decided I'd much rather poll an ADC, considering 8 channels use 4 pins. All of this is in addition to GPS and IMU, and environmental sensors.

    6 Total?

    2x front forward
    2x front downward
    2x rearward

    The pic shows one side, the sensors would be mirrored on the opposite side. Pardon the crude drawing.

    Also, someone had an illustration of the beam of the Sharp sensors. I remember it not being symmetrical. Looking through the datasheet I can't find that. Google isn't turning up much, am I imagining things? I thought it was a thread here... I'll keep looking.
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  • ercoerco Posts: 17,693
    Really? IR out in the blinding sun? Have you tested that? I haven't, but always assumed presumed it would be problematic.

    BTW, thanks for your leads on PowerWheels motors, got mine already and they are sweet!
    "When you make a thing, a thing that is new, it is so complicated making it that it is bound to be ugly. But those that make it after you, they don’t have to worry about making it. And they can make it pretty, and so everybody can like it when others make it after you."

    - Pablo Picasso
  • Uh... I have the magical IR sensors. They don't pick up IR light from the sun, ever.

    Dangit...
  • ercoerco Posts: 17,693
    Maybe adding even more powered wheels is even gooder-er. The Banana Splits would never "skid steer" you wrong.

    https://en.wikipedia.org/wiki/Amphicat



    "When you make a thing, a thing that is new, it is so complicated making it that it is bound to be ugly. But those that make it after you, they don’t have to worry about making it. And they can make it pretty, and so everybody can like it when others make it after you."

    - Pablo Picasso
  • Here's a shot of the new parts, the motor is removed from gearbox. I'm going to try skid steering first. I have no idea how to connect everything. I'm not really happy about motors being exposed.

    The mini F-150's steering mechanism has been falling apart since day one. The 4WD issue is forcing me into doing something about it, which is a good thing.

    So, how to attach this axle to frame?
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  • parts of a Lazy Susan? (Fleemarket/Garage Sale)

    Enjoy!

    Mike
    I am just another Code Monkey.

    A determined coder can write COBOL programs in any language. -- Author unknown.

    The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this post are to be interpreted as described in RFC 2119.
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