Showing posts with label initial conditions. Show all posts
Showing posts with label initial conditions. Show all posts

Sunday, September 5, 2010

Building a PID controller for the Quadcopter

My students have finally taken some inspiration from the mechanical engineering folks and started on building a PID controller for the quadcopter using simulink blocks and various experiments to measure the angular acceleration produced by the motors. They are still far from having a rigid-body simulation of the system but apparently the PID controller in simulink can be stabilized. Another challenge will be to port the PID controller to Python, building a rigid-body simulation can be attempted with PyODE.

Quadcopter System DiagramThey had also been asking for a block diagram and/or circuit diagram. So I obliged with an Inkscape block diagram, circuit digrams are best left to the manufacturing professionals of Arduino and Gumstix.

Quadcopter test rig ended up being not so fancy and brick based at least it worksThe measurement of angle with time shows non-constant angular acceleration, but the curves can still be fitted with a second order polynomial. The angular rate curves look even more quadriatic, indicating increasing acceleration with time.

Quadcopter Magnetometer YExtracting the acceleration from this should be pretty straight forward as long as we fit a polynomial to a relatively safe part of the dataset. I think a fair number of reptitions and logs of the same experiment will be needed to smooth out the wiggles.

Monday, January 25, 2010

Australia Day - We are Here Day

A lot of my friends are calling Australia Day "Invasion Day" - the historical connotation of landing in Sydney cove are unavoidable. In the larger context a few hundred years makes no difference, lifeforms come and go. We are here only temporarily, no use getting caught up in messes from the past - time is much better used focusing on the future. Let's call it "We are here Day".

Australia Day can become the focus of patriotic (read bogonism) can have at times violent outcomes. I have been at the receiving end of it way too often for my comfort and have been caught by the safety net of private health insurance. At least it promotes some kind of Australian industry - which the Australian flag bag (made in China) I just got from the supermarket does little to. As an engineer it is sometimes frustrating to see the lack of technical production capacity in Australia, well we have a few defence contractors perennially running over budget and some car industry but no advanced electronics. Labour is just way inflated in value - good for affordability of iPhones I guess.

Wealth is usually on a logarithmic distribution and highly influenced by the initial conditions i.e. luck of birth. Our lives are too short for the chaotic butterfly effect on which the universe rests to sufficiently evolve from our initial condition. What we observe is a finite almost linear element of the unfolding system, yet it is sufficiently unpredictable and fractal to be interesting.

Being Australian can simply be the luck of being born in this country or "earning" the right through education, preserverance and holding up signs to do the Citizenship test since the National computerized testing system failed and we don't have the technology to make it more robust. Yet I am willing to hang around and make the system better.