Balancing Leg

It balances!

The inertia changes significantly as the "body" moves up and down the leg - for the controller, I got feedback gains with LQR for the maximum and minimum extension cases, and linearly interpolate between those gains as the leg extends.

More Screw Mechanism Testing

 Now controlled over CAN and USB, using a gui based on the espresso machine software

The the USB communication plus Python GUI gives me nice live-plots and logs.  Here's a plot of the fast position steps:

Pressure control, 1 kHz USB data logging

PI+Lead pressure control with ~30 hz bandwidth (probably will get it's own thorough post soon), native USB data transfer either way (logging at a little over 1 kHz, sending commands at ~15 hz from the GUI), python/QT gui running the show.  Orange = pressure command, blue = measured pressure:

Frequency response measurement

It's been a while since I did any system id for fun:

Pretty darn 2nd order (as expected from motor inertia and magnetic coupling stiffness).  Handy way to get generate a bode plot from timeseries data is  \(\frac{FFT(output)}{FFT(input)}\)

 

Gear Pump Closed Loop Pressure Control

 

Using a leftover pendulum motor controller, Moog brushless motor scavenged from the Media Lab years ago, and gear pump from ebay to play with closed-loop pressure control.  Pressure plotted on the computer screen (and shown on the gauge), pressure setpoint stepped up and down, and a needle valve used as a variable load.

Internals of the gear pump:  Food-grade, stainless body with PEEK/CF gears and bushings: