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Mechanics and Construction => Mechanics and Construction => Topic started by: saba_rish91 on January 21, 2013, 10:08:51 AM

Title: Mathematical Model
Post by: saba_rish91 on January 21, 2013, 10:08:51 AM

Hey,

I'm building a quadruped robot. I need to find its mathematical model. How do I start?
I did try to find few papers on that. But, it didn't help me.
Please help.


Thanks in advance.

Title: Re: Mathematical Model
Post by: Gertlex on January 21, 2013, 11:56:38 AM

There's various aspects... You weren't clear on what you need.

Here's a forum thread where forces on the servos are discussed.
http://forums.trossenrobotics.com/showthread.php?5349-4-DOF-leg-mechanics-and-torque-requirements (http://forums.trossenrobotics.com/showthread.php?5349-4-DOF-leg-mechanics-and-torque-requirements)

As for the actual walking gaits, there are a few different ones.  The NUKE code implements and documents them.
http://code.google.com/p/arbotix/wiki/NukeTuning#Gaits_Included (http://code.google.com/p/arbotix/wiki/NukeTuning#Gaits_Included)

Finally, there are a couple of .gif animations in this thread's first post, which demonstrate the movement being done.  On a single leg, it's purely a geometry problem.  Then with four legs, you just have to figure out how to offset the four legs' movements to get actual walking.
http://forums.trossenrobotics.com/showthread.php?4929-My-4DoF-Quad-Mech-Numa (http://forums.trossenrobotics.com/showthread.php?4929-My-4DoF-Quad-Mech-Numa)

Title: Re: Mathematical Model
Post by: saba_rish91 on January 22, 2013, 11:10:23 AM

In the thesis (link below)

http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.12.2818&rep=rep1&type=pdf (http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.12.2818&rep=rep1&type=pdf)

Page 41, in equation 3.6, the vector rBH is constant and hence the derivative must be zero. But, in the next equation (3.7), he has multiplied it with the rotation matrix. I don't understand how he arrived at this.

Please help.