Tuesday, April 14, 2020

Mojo3 - A Robotic Dog (#7) - OK, One More Test!

Mojo3 is a Compliant Quadruped Robot Dog

Ok, maybe I should read my own blog posts. I believe I was supposed to do a new design. Instead I started the Milli - th WildWorm, but that is a different post.  Before I jump off to a new design, maybe just ONE MORE TEST?  I build the hip servo mechanism so that now we can see the actual distance traveled by the robot's leg.

Mojo3 - Leg Design with Gear Driven Hip and Bearing
The new hip design will be just a gear driven leg unit, and a gear on the servo - as the CAD picture suggests. This design should work, as the weight of the servo is now directly transferred to the Chassis through the bearing. This should remove the considerable load from the small 9g servos.

Mojo3 - Kinematic Motion Test

Here the test is set up, the leg is moving repeated through a single step. There is a 60 degree sweep of the hip section, and a 40 degree pull on the leg segment.  The results are (blurry) below.  In this configuration, the leg is only able to lift about 4mm on the return swing. (I will include the video in the future on my YouTube channel)

Mojo3 - Step Kinematic Motion Trace - Just Not Enough!

Only a 4mm lift on the return of the leg to the forward position.  I do not believe this is going to be enough to overcome the dynamic (tilting) nature of the gate.  Time to consider another design!

on the up side.  A shout out to Oracid1 on YouTube and his nice Inverse Kinematics Arduino code. It is a bit cleaner solution than the one I wrote for Mojo2. I have adopted some of the 'clean code' concepts for Mojo3.

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