UA RNSL Intel Hexapod: 3D Balance Gestures

Hexapod robot designed at the Robotics and Neural Systems Laboratory (RNSL) at the University of Arizona.

The hexapod is using Robotis AX-12, RX-10, and RX-28 servo motors. The controller is a Fit-PC2 with Intel Atom Z530 Processor computer running Ubuntu 9.04, with a custom PIC18F4550 based USB board to pipe motor control protocol.

This is a demonstration of the new leg design which is much more solid than the previous design. Also, new 3D balance gestures have been included based on a spring model. Balance gestures are shown both turned on and off for comparison.

The gray plastic was designed in Solidworks, and was created using a Dimension BST 1200es 3D printer.

Inverse kinematics is used with a dynamic walking gait. The dynamics still need work to be smoother and faster. The legs are not calibrated perfectly either, which can be seen when a foot occasionally lifts up.

Currently the robot has foot contact sensors which will be used in the future for terrain adaptation. Three AX-12 motors will be used to control a camera with 3DOF.

Category:

Science & Technology

Tags:

• hexapod
• robot
• dimension
• inverse
• kinematics
• 3d
• printer
• fit-pc2
• pic18f4550
• rx-28
• rx-10
• ax-12
• dynamixel
• robotis
• robotics
• Ps

[mark11original]

Thats excellent. I want to build a Hexapod, just wondering why do you need three different types of servos? (AX-12, RX-10, and RX-28 servos) I am a beginner at robots and I have only used servos with 3 wires (Hi Tech 645 servo), would these be good enough or should I get better ones?

[blegas78]

@mark11original You don't need three types of servos for any reason. I just like the Dynamixel motors because it is possible to read their state through the serial protocol.

The 645 servos are great for hexapods

[aguirrea]

Great Job, Congratulations!

I'm trying to control an AX12 motor with a pic18f4550 and I have troubles to initialize the serial port at the baud rate the AX12 need, I will be pleased if you could post or send me a snippet of code with the serial initializing of the pic18f4550 to properly work with the ax12

best regards

Andrés

[blegas78]

@aguirrea Configuring the USART largely depends on the oscillator frequency. I have a 48MHz oscillator (FOSC), so to communicate at 1Mbps I set the baud rate register (spbrg to 2 ( solve this: FOSC / (16 * (spbrg + 1)) = baud rate). Other than this, make sure you have one stop bit, are sending only 8 bits, and are in high speed mode. Google MCC18 library and use those functions if you can. Good luck!

[lordK2323]

Hi, if you change the 48MHZ for a 20HMZ, can you still reach 1mbps?, becuase the SPBRG = 0.25 => [SPBRG] = 0

Im trying to control ax12 with 18f4550 usart as aguerrea

Regads.

Seba

[blegas78]

@lordK2323 Not all clock frequencies will work, but some may be close enough. I think +/- 5% error is considered ok. You can check this by plugging in the rounded number used for SPBRG back into to the formula to calculate the actual baud rate. You can then calculate the error by (actual - desired)/desired*100% = %error. I think that you might have too large of an error. I think that a 32MHz oscillator will match the dynamixel bus perfectly though, for all baudrates.

[S7ranger168]

OH MY GOD!!! It's a freaking Replicator!! :P

[tyrokiller]

Now make it run. ;)

[Tannerthomas]

ROBOTSSSS RULLLEEE!!!

[tdurk93v2]

@threepackbigmack How old are you? I am only in high school but I am on a robotics team (search YouTube and google for Walton Robotics) and might be able to at least point in the right direction.

[threepackbigmack]

i have 0% of knowledge about building robots but this is my goal, my dream, and my future to build robots and major in robotics and become a robotic engineer. Where should I start?

[Nomoreidsleft]

Wow, that's probably a very expensive piece of equipment. Check out what Odbot has achieve with some chopsticks and plastic:

watch?v=7hG6Amnb9Mo

No, expensive 3D printer, no expensive 3D modeling software, no expensive servos, and he managed an extra 2 more limbs for eye stalks. So, his is actually a Dexapod.

[bogdanbosss]

Great, now make it the size of a tank , put some armor and a cannon on it and you my friend are rich.

[Krikafan]

All it needs now is a torso-mounted turret ;)

[THEIRONMAN9]

ARGHHHH KILL THE DANCING SPIDER !!

[rtprohn]

lol its getting horny :P

[lilicrashes]

@redtwiggy

I am new too! which books and where do I find parts to try to make something like this?