1 day sale:$60 Hexapod incl 18 Servos

erco

http://www.icstation.com/a1506-legs-robot-black-spider-robot-18pcs-sg90-servo-motor-p-5378.html

If you feel so compelled. Not the sexiest hexapod, but maybe the cheapest. No controller, just servos, plastic parts & hardware. Someday I might. But for my tastes right now, it seems like this bot has 17 too many servos.

GordonMcComb

Interesting minimalistic 3DOF hexapod design. World's worst YouTube video.

Publison

I duno. The audio was OK.

Always tethered. Too light to support a LiPO?

Duane Degn

Publison wrote: »

I duno. The audio was OK.

Always tethered. Too light to support a LiPO?

I hate that video. (of course the song is fine). I really don't like seeing a robot dance by editing it's movements/timing with video.

I think it can support a LiPo. I have on of these. The kit cost $4 more than purchasing the servos alone. I think now it's only $2 more than the servos.

I figure I'll try the base kit and then make my own version.

ICStation claims the servos can run off a 2S LiPo but I think the servo jitter when running on 8V. They behave much better at 5V.

The kit does not include all the required hardware (they're not cheating anyone, it says additional hardware is needed on the webpage).

I haven't finished building the kit but I really don't like the design so far. They provide two bolts where four are needed. With only two bolts the servo easily moves out of position. I think four bolts may add too much weight since the bolts are pretty big.

The kit has some of the worst laser cutting I've seen. Lots of ghosting around the cuts. I'm guessing from reflections. Not all the holes are aligned correctly.

Publison

Good to know Duane. Last thing I need is another distraction that prevents me from checking out my new ebay S2.

erco

Aren't those tiny servos constantly on the edge of stripping/breaking? Surely one good drop on the floor and it's all over. Even when in normal use, it seems like cheap servos will wear out their feedback pot, constantly sweeping over the same tiny section of their travel. I'm guessing that's why so many builders have variable height built in, to change the range of motion and spread the love/wear around.

I love hexapods, and I'll get to building one someday, but it seems like a huge investment of time for something with a very limited life. I'm a minimalist.

Oh how I'd love to see a hexapod do Nikos' Fibonacci spiral. Duane?

GordonMcComb

I think as an inexpensive design to study legged locomotion it's fine. But it's underpowered by cheaply-made servos, and is unlikely to last long in real usage. Tethered is ok for this type of hands-on educational project, so I have no problem with that.

The video makes it IMPOSSIBLE to see how, and even if, the robot is moving with all its leg thrashing. The "dancing" is cute, but tiresome after the first 30 seconds. We want to see how well it walks and turns, and with no frame of ground reference in the video, that's not possible. As far as I can tell, it's not actually moving except for random skittering.

Martin_H

The annoying part of the video is that they're mostly using two degrees of freedom in the legs. Here's a quadruped using all three like a boss:

xanadu

That's a lot of servos! Doesn't look like payload is an option if you want it to last long.

erco

In that first (ICstation) video, it looks like there are LEDs inside the servos. Am I seeing things? Might just be a reflection, the light looks green & red to me.

Light-up servos would be cool.

Duane Degn

I think the lights are reflections from the LEDs on the servo control board.

ICStation's Hackaday.io project about this hexapod lists this servo controller as the one to use.

http://www.icstation.com/channels-servo-motor-controller-robot-contorller-servo-driver-p-3509.html

(IMO a $25 Propeller Project Board with some headers would be a much better option for controlling a hexapod than the $55 board linked above.)

I'm pretty sure ICStation did not program IK algorithms. I think they used a servo sequencer.

The quadruped Martin found certainly uses IK.

I'm pretty sure a quadruped is in my future. There's something extra organic looking about a four legged robot when it's done right (as demonstrated in the video).

The last time I tried improving my hexapod program I tried to add the ability for the robot to tilt its body and still be able to walk nice and level. It turns out this extra complication really adds a lot of computations required to figure out which angle each servo should be positioned. I haven't yet been able to tilt my hexapod consistently.

I think it's pretty clear Paul K. figured out how to tilt the body on his hexapod.

Very nicely done. (I think Paul does a great job on anything he takes on.)

I think my "Halloween Hex" has character but you'll notice the body stays level to the ground.

I think my hex may move smoother than Paul's but I'm not sure if Paul was trying for smooth motion.

My algorithm supposedly keeps the body level (not that I knew how to do it different) and the body should move at a constant speed (as long as the input speed isn't changed).

I should really try combining Paul's code with mine (or visa versa). A hexapod that could move like Pauls and also move nice and smooth should really look cool. Of course I'd also keep the eyes. People generally really like the eyes on my hexapod. They were a relatively easy addition for the impact they seem to make.

Whit

Interesting stuff here and good find erco - I too will wait - if I do this - I want higher quality!

@Duane - great observation about he four legged bot - I had never really noticed that before - it is a bit more creepy!

NWCCTV

I am not a fan of the cheap Chinese plastic. I bought one of the supposedly awesome grippers and spent more time super gluing pieces back together as the slightest thing seems to make them snap. I gave up and ordered an aluminum one!!!!