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Dec 07, 2019, 05:14 AM
My name is Naga
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Hexapod Walker


Anyone have any experience making a Hexapod Walker?

I recently bought the parts for two of these robots; a nice alloy frame with 18 Tower Pro MG996R servos and a smaller and much acrylic cheaper acrylic frame with 18 SG90 servos.

I am going to control them with an SAMD21 micro controller running Arduino code with a couple of 16 Channel PWM servo controllers.

There are a few examples of Arduino code out there to set these up myself but not much.

Any comments or suggestions would be appreciated!
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Dec 11, 2019, 09:09 PM
Out of the way, Peck!
Have you seen the SSC32 servo controller from Lynxmotion?
https://www.robotshop.com/en/lynxmot...ontroller.html

It allows you to control up to 32 servo channels with 1uS resolution as well as access to 8 analog I/O. The SSC-32U includes bidirectional communication with query commands, synchronized, or "group" moves, plus a built-in 12 Servo Hexapod Gait Sequencer.

It's what i used in my underwater ROV build, to control all my lights, servos, and (2) 9-dof manipulator arms.

I have 'plans', you know, the crazy ideas we have that we'll probably never do...To build a hexapod, but i prefer building things Bigger, and so my design calls for a 4m-tall 'spider', built from aluminum tubing, XPS foam, fiber-reinforced packing tape, with (18) cheap cordless drills turning Acme leadscrews, driven by h-bridges, for the leg servos (homemade linear actuators). Maybe with some Coolneon electroluminecent wire running along the purple/yellow/green-painted body and legs. This should give me a huge fast-walking spider to scare people with...lol.
Last edited by Oddmar; Dec 11, 2019 at 09:17 PM.
Dec 11, 2019, 09:49 PM
My name is Naga
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Thanks for your reply Oddmar.

There are a few solutions to a Hexapod, especially from Lynxmotion. They even do special boards for Hexapods with the code already written, just download and go.

Although not really expensive, the board you linked to cost way more than the boards I will use (not really an issue in its self) and doesn't really give much advantage that I can see.

Take the built in 12 Servo Hexapod Gait Sequencer for example. That is two not three servos for each leg so only back/forward and up & out or down & in. All movements must cause the foot to move in arcs.

Three servos per leg (18 total) gives horizontal back/forward, vertically up/down and horizontal in/out so much better as it means the foot can be moved in straight lines. Just a bit of trigonometry required to coordinate all three servos to place the foot exactly where wanted in 3D space.

Also the inbuilt Hexapod Gait is two tripods, one on each side. So one tripod lifts and swings forward while the other thrusts back. That is a very simple and clumsy gait that is easy to program from basic code.

The synchronised or group moves may be useful.

I guess I am making it harder for myself, but much of the challenge with this project is developing the code in Arduino myself.

Getting a double Tripod Gait going with two servos per leg easy, I already have code for that and with three servos a little more complex but just trig using inverse kinematics.

What will be much more challenging will be graded movements so the servos don't just snap into the new position but move smoothly in increments from one position to the other perhaps even with acceleration and deceleration at the start and end of each movement.

Then apart from the basic double Tripod gait, there are lots of others like ripple gaits and so on. It is also possible to program in a dance sequence!

So the fun is going to be in the coding. Maybe I am being too ambitious but I want to develop as much of this as I can myself.

Thanks for your reply, you have encouraged me to push on with the project!

Capers II hexapod gait demonstration (3 min 4 sec)



Hexapod: Best of Dance 2010 (3 min 25 sec)
Last edited by nagas; Dec 11, 2019 at 10:02 PM.
Jan 02, 2020, 07:34 AM
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Hi!

Hexapods are really cool and great fun projects to build, I have tried to build one too but I ran into a problem I could not solve and thus lost interest to it.

I used Arduino nano and USC-32 servo controller but it didn't work properly.

You can read my blog post about the build and leg twitching problem if you are interested.
Also if you know or figure out what causes the problem in the video at the bottom of this post, please do tell me.

http://andershomm.com/hexapod-pt-0/


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