Now that we’ve returned to Canberra and taken a well-earned break, we have spent some time reviewing our performance at the OBC. The following article is a review of what we did and didn’t do well as a group at the OBC.
Winning the OBC, whilst an awesome achievement, has also provided us the chance to act out a search and rescue scenario as a team. Thus a review of our performance at the OBC provides some valuable information on how we can improve ourselves in future “real life” S&R scenarios, in addition to providing hints and tips for other likeminded UAV organisations.
Things we did well:
The two radio systems (5.8 GHz Ubiquiti Rockets and 928MHz RFD900’s) used for telemetry and imagery worked quite well. The automatic failover between the two links worked flawlessly and enabled us to easily work outside of the range of the 5.8GHz datalinks for parts of the mission.
The Pixhawk/APM:Plane flight controller tracked the waypoints during the mission extremely well during periods of strong gusting winds.
Our image recognition hardware/software found the missing bushwalker easily and quickly displayed it on our screens. Repeated passes over Joe allowed us to get a high accuracy on our estimated position of him.
The wind correction algorithm for our bottle drop, whilst simple, worked extremely well. During testing, we’d used our data to develop an empirical formula for predicting the bottle drop location based on the aircraft’s position and speed and the direction/velocity of the wind.
Things we didn’t do so well:
Labelling of power ports – during setup, we accidentally killed the ethernet switch used in the Ground Control Station (GCS) network (as we had multiple GCS operators/laptops) by plugging the switch into a 12V plug instead of the 7.5V plug. Fortunately, we’d bought a spare switch with us!
Checklists and communications were definitely an item we’d not tested and developed enough. There was confusion about who was doing which check and when on the checklists. Some critical items were left out of the checklists.
Our takeoff and landing (done automatically by the APM) were marginal, far below our usual quality. The takeoff in particular raised some concerns from the OBC Judges, as the UAV was blown off course towards the GCS and Judge’s tents during takeoff. From an organisational perspective, several things did NOT happen:
- We did not take the wind into account during our takeoff preparations
- Lack of practice in taking off in windy conditions
- Lack of communication between the GCS and Pilot as to the wind conditions
- Lack of practice in aborting automated takeoffs
At the end of the day, we were very focussed on gaining the extra points in the OBC (for an automated takeoff and landing) and we never stopped to properly consider the circumstances under which the automated takeoff would not be appropriate.
During the mission itself, our antenna tracker required slight offsets to track the UAV properly. Part of this was due to a different magnetic environment at Kingaroy (compared to our home base in Canberra) degrading the compass accuracy. In addition, we’d never considered having to set up the antenna on non-flat ground!
As mentioned previously, the landing to Kingaroy airport also presented some issues. One again, the wind had its own ideas and carried the aircraft past our nominal landing point and it did not land until much further down the runway, finishing up very close to the geofence. As with the takeoff, we did not consider the effect of strong winds on our aircraft during this phase, nor did we have experience in landing in strong winds.
So, for other UAV operators out there, we offer the following advice:
- Don’t just have checklists – use them regularly and continuously improve them
- Practice flights in a variety of wind conditions. Know the limits of the airframe and of the automatic flight modes in these wind conditions
- Ensure that safety is always put first - have a safety management system. UAV’s do have the potential to hurt or severely injure people!
- If operating in a team, make sure that everyone clearly knows what their responsibilities are. Checklists and operations manuals work well for this. Following this, regular practice with a full UAV/GCS setup with the entire team is a must
A full review list is available at https://canberrauav.readthedocs.org/en/latest/lessons/OBC2014/review.html
We'd like to thank 3DRobotics for their very generous support of CanberraUAV for the 2014 UAV Outback Challenge. Thanks also go to all the individuals we've collaborated with, to further the field of S&R UAV platforms.