But those servos (they look similar to the Dynamixel type used on the Bioloid) draw so much current the robot cannot support the weight of batteries to provide the juice -- hence the wires. Something has to be done about that, though for some robotic tasks, a tether is not a problem.
Given standard (though still powerful) servos and a box full of Lynxmotion Servo Erector Set parts, one could build something like this for around $1,500 or so. The Dynamixel servos are about $45 each, which is what I'd probably use (if I had the money!). A hexapod with 4 DOF is 24 servos, times $45, or $1,080. Metal brackets would make the robot smaller than if using the plastic stuff used on the Bioloid, but I'm not sure the Lynxmotion stuff firs the Dynamixels.
I didn't see any clips of it in action, but one nice aspect of the Dynamixel servos is that they're electrically switchable between 300 degree arc and continuous rotation, the latter allowing them to be used as whegs.
For much of what they show in the video, they should have been able to carry batteries without much of a problem. I don't know what the run time would be like, but they could do it. There are enough similar robots being built with Lynxmotion and other parts that carry their own power source.
Some of the things like walking under the mesh or doing cartwheels might present some issues with managing the CG of the robot with the extra mass from the batteries. But maybe putting batteries on top and bottom of the body would help that.
But, it's a cool video.
Possible if you use standard servos and only 18 of them. Like I said, if the servos are Dynamixel or similar (which they appear to be -- they aren't standard R/C servos), and they use a minimum of 24, you're looking at up to 1 amp per servo, though holding current might be half or third that. The robot in the still-frame of the video has 30 servos, 5 DOF per leg. No way an on-board battery will support the current for that many servos, and that's using the cheaper AX-12 (the AX-18s draw up to 2.2 amps each).
I agree. I meant the basic functionality and not the specific robots in the video.
Also, if you can limit the number of servos moving at one time you should be able to reduce the current draw - although the motion will not be as fluid.
Yes, that's true. And many of the 24-servo Lynxmotion-based quads and hexapods have to do that.
That said, with li-poly we're getting there. Maybe not with long play times, but perhaps enough to take a few snapshots of the bomb some cretin put in the heating ducts.
I did a 10 servo snake that operates on regular AAAs, and there's no leg lifting involved. Play time is about 10 minutes, then the snake has to rest.
Those digital servo's are from Robotis(Dynamixels) but I can't quite read the model #. It is possible all of those servo's are being controlled from one serial pin interfaced from the microcontroller.
In order to do a smooth slither the servos need to be slowed down. When moving mass the sudden motion of the servos destroys the slithering action and the snake just thrashes about. It's a 2-axis snake, so it's okay for segments to replicate earlier ones, which simplifies the programming. My brother, who has the math brain in the family, is helping me write the algorithm. Right now the snake just wants to jump off to the floor and bite my ankles.
Had I been smart I would have used a Pololu servo controller, which has speed and ramping features built in. But NOOOO! I had to write all that Smile myself. And on a single thread Arduino no less. At least a Prop would have provided some multi-tasking, helpful because during all this the snake needs to sense objects in front *and* listen for commands from a TV remote control.
To do it "right" the sine wave has to dampen -- the tail end of the reptile doesn't have the same amplitude as the front. There are only a few videos of other robotic snakes in action, and real snakes are no help, as their motions are so complex it's fairly hopeless to attempt to replicate them, at least with typical homebrew construction. I have to do this so that other people can build it, too.
Will your snake have tiny wheels on the bottom? I had to do that on mine. (Most robotic snakes do the same.) I ended up using little wheels off of some skateboard thumb toys I got at the dollar store. Same color as the snake so they blend in.
After this is the talking parrot that slings insults at you when you enter the room.
After this is the talking parrot that slings insults at you when you enter the room.
-- Gordon
Isn't that what wives are for? DOH !!!!!!!!!!!!!!!
I'll be using rubber HOT WHEELS trucks on mine, thank you very much! This guy's S5 robot doesn't look like it's damping: http://www.snakerobots.com/S5.html
Ron Czapala
Posts: 2,418
Comments
But those servos (they look similar to the Dynamixel type used on the Bioloid) draw so much current the robot cannot support the weight of batteries to provide the juice -- hence the wires. Something has to be done about that, though for some robotic tasks, a tether is not a problem.
Given standard (though still powerful) servos and a box full of Lynxmotion Servo Erector Set parts, one could build something like this for around $1,500 or so. The Dynamixel servos are about $45 each, which is what I'd probably use (if I had the money!). A hexapod with 4 DOF is 24 servos, times $45, or $1,080. Metal brackets would make the robot smaller than if using the plastic stuff used on the Bioloid, but I'm not sure the Lynxmotion stuff firs the Dynamixels.
I didn't see any clips of it in action, but one nice aspect of the Dynamixel servos is that they're electrically switchable between 300 degree arc and continuous rotation, the latter allowing them to be used as whegs.
-- Gordon
Some of the things like walking under the mesh or doing cartwheels might present some issues with managing the CG of the robot with the extra mass from the batteries. But maybe putting batteries on top and bottom of the body would help that.
But, it's a cool video.
-- Gordon
I agree. I meant the basic functionality and not the specific robots in the video.
Also, if you can limit the number of servos moving at one time you should be able to reduce the current draw - although the motion will not be as fluid.
That said, with li-poly we're getting there. Maybe not with long play times, but perhaps enough to take a few snapshots of the bomb some cretin put in the heating ducts.
I did a 10 servo snake that operates on regular AAAs, and there's no leg lifting involved. Play time is about 10 minutes, then the snake has to rest.
-- Gordon
Still, graceful walkers amazing to watch. That cartwheel at 1:40 is a cool new move AFAIK.
No, whegs good. Whegs is magick.
-- Gordon
Me wanna hear more about your 10-servo snake, Gordon. That's where I'm headed with these 8 servos: http://www.youtube.com/watch?v=HSLktpOkrGs
Had I been smart I would have used a Pololu servo controller, which has speed and ramping features built in. But NOOOO! I had to write all that Smile myself. And on a single thread Arduino no less. At least a Prop would have provided some multi-tasking, helpful because during all this the snake needs to sense objects in front *and* listen for commands from a TV remote control.
-- Gordon
Will your snake have tiny wheels on the bottom? I had to do that on mine. (Most robotic snakes do the same.) I ended up using little wheels off of some skateboard thumb toys I got at the dollar store. Same color as the snake so they blend in.
After this is the talking parrot that slings insults at you when you enter the room.
-- Gordon
Isn't that what wives are for? DOH !!!!!!!!!!!!!!!
I'll be using rubber HOT WHEELS trucks on mine, thank you very much! This guy's S5 robot doesn't look like it's damping: http://www.snakerobots.com/S5.html