One-Servo Robot Challenge

ercoerco Posts: 18,191
edited June 2015 in Robotics Vote Up0Vote Down
How about a one servo (or one motor) only mobile robot? I have a concept I'll be trying soon. Inviting others to start thinking and building.

It's a no-brainer to do a wheeled robot doing J-turns: a continuous rotation servo or motor drives robot forward in one direction, and spins robot in the other direction. So the bot either goes straight or turns in one direction. But I'm thinking of a bipedal weight shifting walker. Maybe limper. Will see.

If I add a requirement that it's gotta do a figure 8, then the J-turn bot is mostly out, unless the mechanism only selects curve left and curve right. That's cheating.in my book. So it has to be able to drive straight too.

Anyone else game? Start thinking, Duane, Martin_H, Amanda, Gareth, Whit, Rick, Rich, Matt_G, Nikos and everyone else! ( I know I forgot some people...)

Let this 3-servo bot inspire you: https://www.youtube.com/watch?v=ej1_BWnmpgg

That music is second only to Cliff Richard's "Congratulations"!
"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
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Comments

  • 122 Comments sorted by Date Added Votes
  • Martin_HMartin_H Posts: 3,984
    edited January 2015 Vote Up0Vote Down
    I'm interested, but completely befuddled how to do a figure eight with only one servo.
  • ercoerco Posts: 18,191
    edited January 2015 Vote Up0Vote Down
    Genius starts with befuddlement, Mister First Responder!

    Please promise me that this challenge will not in any way become the object of your fixation. I expressly forbid it!
    "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
  • WBA ConsultingWBA Consulting Posts: 2,631
    edited January 2015 Vote Up0Vote Down
    I may not have the adequate "walking mechanism" knowledge to explain this right, but a single servo robot that can do a figure 8 should be this easy:

    The servo needs to drive two actions for each side of the "walking mechanism". At dead center, 90 degrees, the servo is in "neutral". When the servo is driven to the "left" or 0 degrees, two actions need to occur. One is the action of shifting the center of gravity to the right foot and the second is to pull the left foot forward. Same goes for driving the servo to "right" or 180 degrees, but shifts weight to the left and pulls the right foot forward. My knowledge of these mechanical actions is limited to what I have seen on Youtube or project sites, so I can't explain it more nor draw it properly to show the lever and cam actions that would need to occur, but I can visualize it mostly in my head.
    The action of driving the servo from neutral to either side and back to neutral needs to engage the movement mechanisms through a complete cycle. In other words, going from 90 to 0 and back to 90 should mean the robot goes from a balanced stance, leans to the right, moves the left foot forward, and then balances again.

    attachment.php?attachmentid=112779&d=1421104327

    Once the mechanics of that nature are in place, the robot's movements are pretty simple to make up:

    Servo positioning for actions:
    Walk forward: 0, 180, 0, 180, etc (left, right, repeat)
    Walk slight left: 0, 90, 0, 180, 0, 90, 0, 180 (left, left, right, repeat)
    Spin left: 0, 90, 0, 90, 0, 90, etc (left, left, etc)
    847 x 768 - 102K
    Andrew Williams
    WBA Consulting
  • W9GFOW9GFO Posts: 3,715
    edited January 2015 Vote Up0Vote Down
    Think how a canoe is driven (paddled). Only one side at a time, for various stroke lengths/directions. One servo could do that pretty easily I think.
  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 21,046
    edited January 2015 Vote Up0Vote Down
    W9GFO wrote:
    Think how a canoe is driven (paddled). Only one side at a time, for various stroke lengths/directions. One servo could do that pretty easily I think.
    I agree. Lever-actuated ratcheted wheels would be one way to do it. The really tricky part would be how to make the bot go in reverse.

    -Phil
    “Perfection is achieved not when there is nothing more to add, but when there is nothing left to take away. -Antoine de Saint-Exupery
  • ercoerco Posts: 18,191
    edited January 2015 Vote Up0Vote Down
    The really tricky part would be how to make the bot go in reverse.

    Reverse isn't a requirement. Straight, left and right turns are. Could be curving arcs or turning in place to the figure 8.
    "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: 3,059
    edited January 2015 Vote Up0Vote Down
    Tri-copter with tail servo.

    What do I win?

    Edit: Oh dang it says one motor. I get it now...
  • ercoerco Posts: 18,191
    edited January 2015 Vote Up0Vote Down
    Ah xanadu, I'm sorry I left you off of my rushed call out list, but you're certainly a capable builder too.

    Also Tommy Tailspin, Chris L8, zappman, Paul K, vanmunch. And so many others!

    @Tommy: One servo is JUST a rudder. What can you do?

    Who knows, this might lead to another viable robot for Parallax to sell. Start writing your "Robot of the Year" acceptance speech now.
    "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: 3,059
    edited January 2015 Vote Up0Vote Down
    Thanks for the mention! There was a small robot made a few months ago that used the acceleration of the motor timed with flexible legs and rigid legs to create something like what you're talking about. Memorable article. http://spectrum.ieee.org/automaton/robotics/robotics-hardware/how-to-make-a-steerable-robot-with-just-one-single-motor

    I guess timing and acceleration are one very good approach. For me it would be easier to develop some kind of clutch between the wheels and motor. I have some ideas, but would the clutch be considered extra motors?

    There's a magnet in development where an electrical pulse can change its poles. It will be neat to see if that is used as a clutch. You could have one motor, and pulse the magnetic clutches to control their friction. Sounds almost as complicated as encoders and timing though.

    hmmm...
  • ercoerco Posts: 18,191
    edited January 2015 Vote Up0Vote Down
    Clutches, gears, mechanism, all doable but overkill IMO and certainly no fun to prototype. I'm thinking simple, all momentum and weight shift. Tilted axis servo shifts battery weight L/R, CW/CCW. Feet might be Hexbug or bristlebot-style "clutches" that grip better one way. Control is by how far and how fast the servo moves & shifts the CG.

    IIRC, didn't PhiPi have something like this with a tilted axis servo a while back?
    "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
  • Tim-MTim-M Posts: 520
    edited January 2015 Vote Up0Vote Down
    Brings back lots of memories Beau...

    I used to repair consumer electronics for a living and saw hundreds and hundreds of VCR's come across my bench, mostly needing rubber parts like the idler wheels and belts central in your photo. That is a clever mechanism providing a lot of function from a simple single motor.

    Now back to your original thread programming and topic...
  • W9GFOW9GFO Posts: 3,715
    edited January 2015 Vote Up0Vote Down
    Have you seen those walker toys that will walk down a slightly inclined ramp? You could use one servo for one of those to gently sway a weight side to side. Then to turn you would quickly accelerate the weight in a particular direction.
  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 21,046
    edited January 2015 Vote Up0Vote Down
    erco wrote:
    IIRC, didn't PhiPi have something like this with a tilted axis servo a while back?
    Two servos, Mark Tilden-style:

    [video=vimeo;71207671]


    -Phil
    “Perfection is achieved not when there is nothing more to add, but when there is nothing left to take away. -Antoine de Saint-Exupery
  • ercoerco Posts: 18,191
    edited January 2015 Vote Up0Vote Down
    Now we're getting somewhere, fellas. Keep those cards & letters & ideas coming.
    "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
  • TtailspinTtailspin Posts: 1,321
    edited January 2015 Vote Up0Vote Down
    Thanks erco, that means alot, Just wish I was in the same league as yourself, xanadu, vanmunch, Et al...(forget naming them all, You're all my hero's...)
    The only thing I've got that is even a little close to what you are describing, is this thing I built for a "white Elephant" gift exchange for Xmas this year...
    This Unfinished Prototype is for a "State of the Art, Table Top Flight Simulator." is just screaming for some Electronics to be installed. Just waiting for some free time to get back into the fun...
    I have been swamped with "Dream Jobs"(one offs I can't believe I have been commissioned to complete.) Some of my best work too..

    Sorry, gonna have to sit this one out for a few more weeks. :(

    Thanks again erco. You Da Man!.



    -Tommy (Casters are for Suckers) Tailspin.
    1024 x 1365 - 191K
  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 21,046
    edited January 2015 Vote Up0Vote Down
    Tommy,

    Wait a minute! You're not You weren't this guy are were you?


    whose Cessna 152 Aerobat I once had the "pleasure" of almost throwing up in? (You kept ashes in the ashtray so you could tell when the rental pilot pulled negative G's!)

    -Phil
    “Perfection is achieved not when there is nothing more to add, but when there is nothing left to take away. -Antoine de Saint-Exupery
  • NikosGNikosG Posts: 604
    edited January 2015 Vote Up0Vote Down
    I would say a robot similar to the "Penguin Robot ". But looking at Penguin Features: I realized that penguin has two servos and not one!
  • TtailspinTtailspin Posts: 1,321
    edited January 2015 Vote Up0Vote Down
    No sir, that is not my Airplane.

    But, Uhm, errr... So you got into an Airplane with someone that uses the name Tailspin in the company name?
    That's kinda like playing cards with a guy named "Doc" isn't it? :)



    -Tommy
  • LoopyBytelooseLoopyByteloose Posts: 12,537
    edited January 2015 Vote Up0Vote Down
    Martin_H wrote: »
    I'm interested, but completely befuddled how to do a figure eight with only one servo.

    HINT -- I suspect the car you drive everyday is the equivalent to a one-servo robot. After all, it has merely one engine.

    Of course, a clever fellow might come up with several other solutions. I think that something similar to rowing a boat might work out. To turn, you just do more strokes on one side.

    On the other hand, there is a simple one-servo robot that I built years ago... almost forgot. It requires for wire legs. It was a BEAM project.

    http://www.instructables.com/id/How-to-build-the-one-motor-walker/

    http://www.solarbotics.net/library/circuits/bot_walker_uCrawler.html

    Sorry if I spoiled someone's fun.
    Hwang Xian Shen, Puddleby-on-the-Marsh.
    All things considered, I can live and thrive without Microsoft products. LINUX is just fine.
  • Duane DegnDuane Degn Posts: 10,000
    edited January 2015 Vote Up0Vote Down
    Sorry but I'm sitting this one out. IMO, a robot really needs to have at least six servos to deserve the name "robot". (I am joking (mostly).)

    Let's Make Robots recently had a single motor robot challenge. This was the winning entry.
  • W9GFOW9GFO Posts: 3,715
    edited January 2015 Vote Up0Vote Down
    HINT -- I suspect the car you drive everyday is the equivalent to a one-servo robot. After all, it has merely one engine.
    One motor AND one servo (the driver which turns the steering wheel).
  • kwinnkwinn Posts: 7,512
    edited January 2015 Vote Up0Vote Down
    Duane Degn wrote: »
    Sorry but I'm sitting this one out. IMO, a robot really needs to have at least six servos to deserve the name "robot". (I am joking (mostly).)

    Let's Make Robots recently had a single motor robot challenge. This was the winning entry.

    Clever, but could be done better and with smoother motion using a hexapod.
    In science there is no authority. There is only experiment.
    Life is unpredictable. Eat dessert first.
  • Martin_HMartin_H Posts: 3,984
    edited January 2015 Vote Up0Vote Down
    W9GFO wrote: »
    One motor AND one servo (the driver which turns the steering wheel).

    Bingo, that's why I find this so hard. Each degree of freedom usually requires a motor or servo.

    I can imagine a geartrain which turns the drive wheel side to side, as well as providing forward power. With proper tuning such a mechanism could probably do a figure eight. However actually building such a machine is not something I'm good at.
  • ercoerco Posts: 18,191
    edited January 2015 Vote Up0Vote Down
    Heck, if it was easy, anybody could do it. Which is why I've recruited you cats, the best & brightest. Duane, I'm not letting you sit this one out. Nice try though.

    You CHICKEN, McFly?

    I hope to see some entries in a week or so, or I'll have to add a "solar powered" requirement too!
    "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
  • W9GFOW9GFO Posts: 3,715
    edited January 2015 Vote Up0Vote Down
    You could also drive a robot like a fish. Have a bristlebot type thing mounted on the end of an arm attached to the servo. The servo would vibrate back and forth a couple of degrees to provide the propulsion. To steer move the servo to one side while still vibrating.

    With the right type of attachment you might even be able to go in reverse by varying the frequency of the vibration.
  • ercoerco Posts: 18,191
    edited January 2015 Vote Up0Vote Down
    Great call, Rich. I was thinking along those lines with a skateboarder metaphor. Cycling through the servo's middle range provides straight ahead propulsion (perhaps like a railroad handcar, you might also get fwd/reverse with phasing), and to turn, you coast for a bit while the servo goes to either extreme, which tweaks the steering linkage L/R.
    "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
  • kwinnkwinn Posts: 7,512
    edited January 2015 Vote Up0Vote Down
    Pretty hard to beat two wheels with sawtooth gears and a servo for simplicity. Rotate left to turn left wheel, right to turn right wheel. Alternate left and right to go forward, do more left than right to turn right, more right than left to turn left.
    In science there is no authority. There is only experiment.
    Life is unpredictable. Eat dessert first.
  • ercoerco Posts: 18,191
    edited January 2015 Vote Up0Vote Down
    Love it, kwinn!

    Video below is for popsicle stick loving-Duane and Hexapod fans. No turning or control, but it's inspiring since it has such nice articulation and only uses one motor. Paper clip legs and linkages. Shorter video at https://www.youtube.com/watch?v=hO9pCjlSmso

    Those purple batteries look like the cheap Ebay NiMH cells I posted about long ago. :)
    "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
  • WBA ConsultingWBA Consulting Posts: 2,631
    edited January 2015 Vote Up0Vote Down
    erco wrote: »
    Love it, kwinn!

    Where's my love Erco?? I posted the exact same idea 2 days ago in post #4.. now, where's that crying emoticon.............
    Andrew Williams
    WBA Consulting
  • ercoerco Posts: 18,191
    edited January 2015 Vote Up0Vote Down
    Where's my love Erco?? I posted the exact same idea 2 days ago in post #4.. now, where's that crying emoticon.............

    OMG Andrew I did completely miss your post. Spot on, my bad, you nailed the left/right wiggle walk early on in great detail. Apologies, I defer to your venerable expertise and considerable body of work.

    So it should be a simple matter for you to build your creation and post the first video...? :)
    "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
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