Auric: Learning from testing

It's amazing what you learn when testing in the real world...

Auric went out for a long drive last weekend, while things went pretty well, there are always things to learn:

1.  Solving a performance problem

Halfway through the long test I noticed that Auric was pulling to the left, and I suspected a motor drive problem.  After putting the machine up on a bench for a closer look I noticed something, well, "green"

Upon closer inspection, Auric had decided to become an autonomous lawn mower and managed to wrap a 60cm grass runner around the front left drive.  Side effect was that the motor was loaded down and that caused thermal protection in the driver board to kick in.

The final insult was when the imaging detected off-course behaviour and resulted in the motion controller trying to drive the jammed motor even harder, resulting in a vicious cycle.

The end result of all of this is twofold.  Firstly, removing said grass solved the problem, and I wish to add "WEEDING" as a term in the robotics lexicon for the process of solving environmentally caused mechanical issues.

2.  When the board is not what it seems

Dear SparkFun, I owe you an apology.

In my last article, I wrote I was using your "Monster Moto Shield" as part of the motion controller.  Those with keen eyes will spot something completely different at the back of Auric at present.  So what happened?

I purchased two boards from an online reseller because my usual suppliers had no stock, and it would take too long to get them from the US.  Both boards failed in exactly the same way.  The driver for motor 2 would only drive the motor in reverse.  In forward, the potential across the motor was about 0.8 volt, regardless of the motor being used. supply voltage, etc.

I thought this was highly unlikely, so I looked closely at the boards.  While the say SparkFun on them, have the right logo and all, they don't appear exactly like the board on SparkFun's website.  The two driver chips have wildly different manufacturing ID numbers as well.

So what did I get then?  A pair of pretty good looking knock-offs.  Oddly enough, the seller has gone to ground so I have done my money on these ones, and will stick to my preferred resellers in future.

To meet the deadline, I switched to a Deek Robot motor driver which has got me past the deadline, but I am looking forward to getting my real Monster Shields soon!

3.  If it sticks out, it will get broken
In the interest of getting some more interesting video, I attached a Moovie Action camera from Jaycar electronics just above the front track.  This short clip clearly shows what happens when the front camera extends beyond the line of the front tracks:


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