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Advice for Quadruped (QSR-X1)

PostPosted: Fri Oct 31, 2008 1:28 pm
by clh6685

Picture above is my quadruped which i just done assembly the mechanism hardware. The structure i used is double sided PCB cut by cnc. It is 12DOF actuated by 12 mini servo. The control circuit i was planning to use PIC16F84A. The walking gate will then program directly into the PIC. The question is I have no experience in the inverse kinematic calculation and translate the formula into the assembly code to program it.

My 1st goal is to let my quad walking forward only.
Welcome for any of yours advice.

Re: Advice for Quadruped (QSR-X1)

PostPosted: Fri Oct 31, 2008 2:24 pm
by Matt Denton
Hi Chok, welcome to the forum!

Nice looking quad, and great idea using PCB for the structure, I bet its really light!

If you looking to do IK within the pic, I would say you will need at least a PIC18F series pic. IK uses alot of floating point maths and intrinsic functions such as sin cos etc. My first HexEngine ran on a PIC18F2520 device running at 40Mhz, 10mips. I was able to calculate IK and foot motion at around 30 fps, so for a quad you would probably get up to 40fps. I think you will struggle with the 16F84 device running at a maximum of 5Mips. Also I think writing IK in assembler is going to be a mind bend, I would try and get hold of a C compiler.

Re: Advice for Quadruped (QSR-X1)

PostPosted: Fri Oct 31, 2008 5:21 pm
by No1_sonuk
Also, the 16F84 only has 13 I/O, so if you're driving 12 servos direct, you'll only have 1 I/O left for comms or sensors.
If you want to go with simple PICs, I'd recommend the 16F690. It has more I/O, and has some other functions that'll help.

Re: Advice for Quadruped (QSR-X1)

PostPosted: Sat Nov 01, 2008 12:40 am
by clh6685
Yup,the structure itself is very light in weight.

Matt,Sonut. Thanks for your's recommentation.I'll take into consideration on that.


Re: Advice for Quadruped (QSR-X1)

PostPosted: Mon Nov 03, 2008 8:57 am
by Demmo
your quad looks good to me and what I appreciate the most - your design is original - i haven't seen any design similiar to yours, so i assume it is your invention 8-)

there may be some problems during walking because of spiky (? - not sure if this is a good term) floor contacts, uhmm... fingers? ;) it probably will lose grip and legs will slide during fast moves - this is why most crawlers use rubber caps

what torque do your servos have? your quad legs looks to be quite long when erected, so if servos are weak you would have to keep them close to the body to minimize force lever... maybe the quad will be light enough and mentioned problem will not appear - i have no idea how much does it weigh

keep working,
budding project


Re: Advice for Quadruped (QSR-X1)

PostPosted: Mon Nov 03, 2008 11:34 am
by clh6685
Hi Demmo,

Your are right, this quad is my own design. I use Solidwork to simulate the structure as in my mind thats looks cool for me before I fabricate it.
I'm agree with your about my quad leg tip design. I'll further add-on a rubber on the leg tip.

The servos I use are:COXA,1kg/cm--FEMUR,1.6kg/cm--TIBIA,1.6kg/cm--
The leg when fully extend is quite long,but I design in that way just wana match the leg and body ratio for good looking only.
When in actual walking gate it wont fully extend.
The weight as the assembly in photo, is about 500gram only. Of course not included batt.

Currently I'm testing PIC16F84A firmware for one of the leg sequence.


First walking gate testing on my Quad

PostPosted: Sun Nov 09, 2008 8:20 am
by clh6685
QSR-X1 first walking testing

Hello world,

Some new update on my quad. Finally my quad out of walking simulation on computer.
Check out it's first walking clip on Youtube above.


Re: Advice for Quadruped (QSR-X1)

PostPosted: Sun Nov 09, 2008 11:03 am
by Matt Denton
Looks great Chok!

Nice fluid movement! those servos move really fast too.. definitely aided by your super light weight leg design.

Re: Advice for Quadruped (QSR-X1)

PostPosted: Sun Nov 09, 2008 2:31 pm
by jaspinall
Wow! Can't believe those legs move that fast! But, they do! Good work :)

Re: Advice for Quadruped (QSR-X1)

PostPosted: Sun Nov 09, 2008 6:54 pm
by Matt Denton
What are the make and model of the servos? Have you shredded any gears yet?