One-Servo Robot Challenge
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"!
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"!
Comments
Please promise me that this challenge will not in any way become the object of your fixation. I expressly forbid it!
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.
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)
-Phil
Reverse isn't a requirement. Straight, left and right turns are. Could be curving arcs or turning in place to the figure 8.
What do I win?
Edit: Oh dang it says one motor. I get it now...
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.
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...
IIRC, didn't PhiPi have something like this with a tilted axis servo a while back?
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...
[video=vimeo;71207671]
-Phil
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.
Wait a minute! You're not You weren't [I see the business has been purchased] 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
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
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.
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.
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.
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!
With the right type of attachment you might even be able to go in reverse by varying the frequency of the vibration.
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.
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...?