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View Full Version : Custom Aluminium 4DOF Hexapod For Sale



mdenton
06-09-2012, 11:23 AM
Hi, I'm thinking of selling one of my custom built hexapods, however, if it doesn't sell I will strip it down and sell off the servos :(.. read on for more details.


Picture of the Hexapod Next to a 300mm Ruler.
http://hexapodrobot.com/images/4DOF/P1060237.jpg


This is the largest RC servo hexapod I have built so far, and had a 4 DOF leg design, with all the leg and body parts designed by myself using T6 grade aluminium and cut on my CNC router. The upper and lower body plates are 4mm thick, the leg plates are 2mm thick. The hexapod uses 24 dynamixel servos arranged in the following manner:


Coxa: RX-10
Femur: RX-28
Tibia: RX-10
Metatarsus: RX-10


http://hexapodrobot.com/images/4DOF/P1060238.jpg


http://hexapodrobot.com/images/4DOF/P1060241.jpg


http://hexapodrobot.com/images/4DOF/P1060242.jpg


Each of the legs is cabled back to a central power and signal distribution PCB. The hexapod was built towards the end of 2009, and was used as a test platform for my 4-DOF algorithms and to test some foot sensors I was working on. All electronics for the hexapod have been removed. The hexapod worked fairly well, however, although the dynamixel servos have plenty of torque, I found their resolution of 1024 steps to be somewhat limiting for my tests, and after about 5 to 8 hours of use over several months the hexapod has been collecting dust. All servos are in good working order.


http://hexapodrobot.com/images/4DOF/P1060245.jpg


The Foot design consists of a 8mm ball and custom machined delrin socket foot attached to a dynamixel bracket. The foot has an adhesive foam pad on the bottom.


http://hexapodrobot.com/images/4DOF/P1060247.jpg


I thought I would see if anyone is interested in the platform before I break it down and sell the servos individually, as it seems a shame to waste all this engineering! Maybe you know a university or research institute that might be interested :confused: Feel free to pass on these details.


http://hexapodrobot.com/images/4DOF/P1060251.jpg


If your interested in purchasing the hex, PM me with a sensible offer, bare in mind that the servos alone would cost in excess of £2500 GBP :eek:

jwatte
06-09-2012, 02:28 PM
I can't afford to buy your pod, even though it looks nice :-)

A question, though: Do the springs really help? It seems like the load on the hip joints would be going the same way as the springs, so when "resting" with the body off the ground, wouldn't the springs actually work in the same direction as gravity?

Gertlex
06-09-2012, 02:47 PM
Just wanted to say... nice job on the construction and pretty pictures :) Thanks for sharing.

mdenton
06-10-2012, 05:31 AM
I can't afford to buy your pod, even though it looks nice :-)

A question, though: Do the springs really help? It seems like the load on the hip joints would be going the same way as the springs, so when "resting" with the body off the ground, wouldn't the springs actually work in the same direction as gravity?

The springs do nothing while the hexapod is powered up, they were added just to stop the legs from collapsing as fast when picking the hexapod up when the servos are powered off. Although to be honest they didn't help that much.

DresnerRobotics
06-11-2012, 10:49 AM
Curious- do you have any video of this guy walking? Love the design!

Zenta
06-11-2012, 03:14 PM
Hi Matt,

Its been awhile since I saw a render of your hex in 2009. Great to see some real pics of it! Looks great, very interesting foot design. You've not considered just selling the servos and replace them with the MX series?

mdenton
06-12-2012, 03:44 AM
Curious- do you have any video of this guy walking? Love the design!

Unfortunately not! I spent a substantial amount of time tweaking the code for this guy, but never bothered filming it! I'm now using a simulator instead which is easier to deal with, but not as nice to look at ;)


Its been awhile since I saw a render of your hex in 2009. Great to see some real pics of it! Looks great, very interesting foot design. You've not considered just selling the servos and replace them with the MX series?


I could, but as mentioned above I now use a simulator. The MX series do look very good, although I'm not entirely convinced 12bit resolution is enough for good PID control. Have you tried them?

The servos I have built myself for various animatronics jobs have at least 15bit feedback, as you tend to loose a bit or two with noise, and to get a decent velocity signal from them you need higher resolutions, unless you have a velocity encoder on the back of the motor :)