#13 Many CAD hours later
Compact 2DOF leg, The Tree
Biweekly Pinto update!
Compact leg
This is a more compact version of the 2DOF leg developed previously, which hopefully makes the robot lighter and more squirrel-shaped. Almost every part is moving, and giving enough clearance while making sure the links have the right geometry to handle the large spring forces was a huge challenge that lasted two weeks.
The motors on the right use a twisted string to rotate the two pulleys (dark green and light red). The pulleys are connected to the light green and light red through series torsion springs in the form of carbon fiber springs. The light green and light red links are a part of a 5-bar linkage in blue, which propels the foot. There aren’t that many rigid links, but packing them all into a small space around a central shaft makes the geometries uncomfortably complicated and interdependent.
It mostly works though!
There are still some issues with the latch to quickly release spring energy, but once that’s fixed in a few days we’ll be ready to test using the motors and perform real jumps.
Scale
This time, the back leg was designed to interface easily with the front leg. However, it still looks a bit silly. The front legs are much longer than the back, and the “belly” is too low compared to the back leg. We’ll likely increase the size of the back leg links (in blue) and bring the front legs closer to the body.
Electronics
The squirrel brain works! It’s a tiny board consisting of a ESP32-S3 that handles the RS485 and Dynamixel TTL buses to control all the motors, some power switches, and Wifi communication.
We also soldered the Ø12encoder, a tiny magnetic encoder that is going to measure the position of the series-elastic link. This lets us know how compressed the spring is and also calculate the position of the foot.
Engineering Open House is coming up in less than 2 months! We’ve been assigned a spot, and here is the tree we have to conquer:
Pinto lookin THICC