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Old Dec 20, 2011, 03:10 PM
tridge is offline
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Originally Posted by davidbuzz View Post
Team TGIF, from Hackerspace Brisbane, are using APM+ArduPlane for a significant part of our flight platform. In case you are interested.... We currently have three experimental plane/s flying using this electronics, and one quadcopter. The quad copter is for fun., not for the OBC. :-)
The quads are certainly fun :-)

I assume you'll be connecting your geofence implementation to a commercial "termination unit" ( which then interrupts the RC signals appropriately on command ) .. and this commection will be by signaling it with an I/O pin from the primary flight APM?
yes, except we are building our own termination unit, not using a commercial one.

The way I read the OBC rules, the "termination system" must be completely independent from the on-board flight systems, which means that having a signal from the primary flight APM that controls when to terminate ( like you've implemented, if I understand it ), is no longer completely independant, is it?
Section 5.5.5 says "The autopilot is allowed to detect the mission boundary crossing and activate the flight termination device". We have interpreted the "completely independent" requirement as meaning that the termination device won't fail due to failure of other components (so separate power and CPU, as listed in the requirements).

eg: the commercial termination unit will not be triggered if the primary APM fails for some reason ( eg battery goes flat, system reboots, locks up, or even just a software bug, whatever)
In our design the termination device also monitors a heartbeat from the autopilots, so it knows if the autopilot has locked up. The rules cover what to do when that happens.

I'm also looking at the rule which basically says "must be able to terminate the plane on-demand, from the ground" , and wondering if this means we must have an entirely separate out-of-band long-range radio link of some sort, just for the termination system? (Eg, would it be acceptable to use the existing telemetry link to send termination instructions, because it's already a "must have" with regard to 1hz the heart-beat signal and what-not guarantees that have been specified around it? ) .
Our interpretation is that using the existing telemetry link is OK for sending a termination command. In our design we have 2 radio links (one high speed, one low speed), and we can terminate via either link.

Cheers, Tridge
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