STALKER quadruped robot

[innerbreed]

*PROJECT STILL IN DEVELOPMENT*
MORE IMAGES AND VIDS WILL FOLLOW!!!



S . T . A . L . K . E . R
Surveillant Tactical Articulated Locomotory Kinematical Enhanced Robot
"This fast and agile walking machine ‘with light and tactical movement, uses advanced and calculated kinematics with dexterous precision to achieve a high standard in robotic articulated motion. With ‘state of the art’ walking technology, this omnidirectional robot is unique in quadrupedal locomotion and design."
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Description: Quadruped robot with symmetrical Design
Developer: Jonny Poole (aka Innerbreed)
Software version: *stalk1.0.bas* *SSC32-V2.01XE* *Atom Pro28* *IDE v8.0.1.7*
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Intro…
I had wanted to build a quadruped for a while ‘having built a Biped, and Hexapods’ but I also wanted to create something new ‘and not just a robot with 4 legs.

Software:
The robot walks with variable speeds, in any direction (translation), or turn in place (rotation), or any combination of the two. The leg lift and ride height is adjustable and also the gait walking speed, also the body rotates in every axis using an Inverse kinematics table written by Zenta.

Hardware:
I am running BotBoardII, BASIC Atom Pro, SSC-32, Atmega168, 2.4ghz wireless Ps2 style controller, HS-645MG's.

The Mechanics:
The robot is made from structural aluminium components from the Servo Erector Set.
Although a few "unplanned" changes have been made to the design of this robot, i am still happy with what has been acheived.
The robot's body symmetry makes this a very ambitious quadruped walker. The three DOF (degree of freedom) leg design provides the flexibility required to walk with an Omni-directional gait!

1st Gen:


2nd Gen:

Powering:
Servos - 1x 6v (5 cell) 1600mah 2/3A NiMH
Electrics - 2x Alkaline PP3 9v

All 12x HS-645MG servos for the legs use Unbreakable MP Gear
The heart of the unbreakable geartrain is the MP Gear. The MP Gear is made utilizing a revolutionary production technique that injects a high impact plastic around a metal pinion gear to form an unbreakable first gear. By utilizing this gear Hitec has successfully reduced the amount of drive train noise that is common in metal gear servos and at the same time added considerable strength to the geartrain.

A Problem Shared Is a Problem Solved:
Main problems i have faced with this project is the inabillity to stop thinking of new ideas.
What you see now, is possibly the 15th overall design idea for this project.
Ideas ranging from legs, chassis, body structure, have all taken an upgrade.

The first gen quad used HS-475's on a basic structure:
everything from spring systems, taking out parts to lower the weight, and even taking the project away from the original idea all together!


For the future:
6x HS-475HB servos will be added, 1 for the “body rotate” (pan), 4 for the two “side cannons” (pan & tilt) and 1 for the “top turret” (pan)
*not added at this point due to the need of a torque upgrade*
Complete Vacuum formed shells & other cosmetics to finalise the design.


Innovations:
The Coxa joint (Hip) is at a -50º tilt to the body as apposed to the conventional +90º.
The reason for this is primarily for cosmetic design structure, but also it has given the robot more function and flexibility. Having said this, there is more strain on the servo's but this doesn't effect the performance too much, thanks to Zenta!

*Only for the 1st gen design.
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Improved gait engine/speed/body rotations X-Z-Y/SSC communication/SSC V2 registers.
A universal gait engine which makes it possible to simply add new gait types by setting properties.
The analog sticks not only controls the step length but also the speed of the gait.
ByteTable Added for additional group-move commands.
The Leg calculations that Zenta developed and posted to me regarding the tilted coxa config.
A internal timer measures the calculation time of each step. This makes it possible to get a perfect timing between the BB2 and the SSC.
The offsets of the servos are moved to the SSC V2 register.
Added Directional heading servo to point towards travel direction.
Added more DualShock inputs to code for extra functions to be added.
Manual body move X/Z (while walking) for better gait control on uneven ground using D-Pad.

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Stalker Specs

Servo motion control = local closed loop
Steering = omnidirectional
Number of legs = 4
Degrees of freedom (DOF) per leg = 3
Total (DOF) = 18
Motion speed (inch per sec)= ?
Body Height = 152mm
Overall Height = up to 410mm
Body Width = 100mm
Body Length = 100mm
Coxa Length = 55mm
Femur Length = 96mm
Tibia Length = 140mm
Weight (w/out batteries) = 3lb 8oz
Ground clearance = up to 254mm
Range of motion per axis = 180º (max)
Accuracy of motion per axis = .09º
Servo voltage = 6 vdc

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Links to project discussion:

http://www.lynxmotion.net/viewtopic.php?t=3601

VIDS SO FAR:
1st Gen:
http://www.youtube.com/watch?v=uQ5W9ULn ... re=channel
http://www.youtube.com/watch?v=yDqQO8zK ... re=channel
http://www.youtube.com/watch?v=k2SdzSOU ... re=channel
http://www.youtube.com/watch?v=1Um7Uw27 ... re=channel

2nd Gen:
Still to come.

THANK YOU FOR LOOKING.

[Matt Denton]

Hi Jonny!

This is looking great!, I had come accross your quad desing some time ago, but haven't been keeping up with progress, nice job!

Would like to see your IK solution for the angled coxa.. looks like its working well

Look forward to seeing it on the move.

[BillB]

HI Jonny,

Looks very impressive.

I like the angled positioning of the coxa alot. The frustration I have with most my Hexapod (where the coxa servos axes are perpendicular to the grouind) is that the IK singularity is vertically below the Coxa.

Your angled coxa configuration gorups the IK singularities together under the centre of the robot. Which is much, much better for IK and will afford you a much broader range of walking gaits. Great stuff.

Keep up the fabulous work.

BillB

[innerbreed]

hi.

thanks for your comments.

unfortunatly i had to change the coxa configuration as trying to program the two rotations needed (ZX) is becomming a pain.
we tried to convert the globle rotations to local for this.

here is the current set up now.
not as eye catching but its easier to program.
iv been having a signal (or im lead to believe) so once this is sorted ill post a vid of the new body ik and gaits!

[wuselfuzz]

Very nice project!

Main problems i have faced with this project is the inabillity to stop thinking of new ideas.
What you see now, is possibly the 15th overall design idea for this project.
Ideas ranging from legs, chassis, body structure, have all taken an upgrade.

Haha, I can understand that, but for me, it's on the electronics/software side.

Or just incredibly random stuff like using a roomba for fast walker deployment.

Hm. Is there any kind of convention for hobby robotics in europe?

Would be nice to see all the stuff others have created in real life.

[innerbreed]

Touching old ground here. by just over two years....
Presently im discussing the Stalker chassis with Eric (DialFonZo). he has come up with a very cool, and interesting design for the project.

After 23hours he supplied me with a concept:


After a little discussion, this then evolved a little further:



4 days later (today) Eric posted me an image of the parts:


Anyway, The stalker project is returning as you may have guessed.

Iv been looking back over the complex tilted coxa, and since all axis are affected when doing coxa rotations 'and to solve the kinematics we would need to convert all (X,Y,Z) feet coordinates from the original Phoenix code, using a simplified rotation matrix for IKFeetPosX, IKFeetPosY and IKFeetPosZ.
im still working this out on a practical basis and then hopefully develop a snippet to add to the code.

but for now im working on fabricating the external look of the stalker etc.

Hope you enjoy it.
Ps: Thanks Eric.