When we perform the MWA tile beam measurement, I will not be manually controlling the 'copter; instead it will execute a series of pre-planned waypoints. Therefore we need to begin testing the waypointing mechanism. Another trip to Edinburgh Oval is a good start, since we've already surveyed the area and I know that it is large and clear of other people, so if the automated control systems misbehave in any way, I can take immediate steps to regain control with no danger to others.
I started by looking at the Google Maps image of the site, and picked a simple square pattern for the 'copter to execute. I attempted to set a point-of-interest just 10m north of the starting point, so that the 'copter would always be facing us. I borrowed a video camera from Curtin IT services to mount on the 'copter, so that we would be able to see what it saw after the flight. We brought a large bright orange cordon of flags which we could leave in a heap at the POI, so that we could see how much its position varied during the video. We also brought a car GPS which could give us the latitude and longitude of a position, so that we could mark it and see whether it and the 'copter agreed. I was assisted by Brian Crosse and several summer school students: Teresa, Zeus, Kimberley and Luke.
Weather was mostly sunny, 32 C with a very light NE breeze.
First we surveyed all of the waypoints, to make sure that I had selected them correctly from Google Maps, and the 'copter wasn't going to disappear over the horizon or into the trees! Brian and the four students went around each waypoint in turn, and a student stayed at each surveyed position. I put the 'copter in the take-off position, 10m north of my own position.
Flight start 16.04
I switched on the transmitter power, then the 'copter, and then connected it to MK Tool and uploaded the waypoints. I then calibrated the 'copter, then brought it up to about 10m altitude, put it in PH/AH for a few seconds to check everything was working, and then put it into 'come home' mode, which causes it to execute its programmed waypoints.
It moved off smoothly along each waypoint, but I could see that it was not yawing to point the camera mount at the POI, instead continuing to point North throughout. As it went to each waypoint, the relevant student left a shoe in the surveyed position, and moved to stand directly underneath the 'copter as it hovered at the waypoint.
Once it reached WP4, it simply stayed in position - I wasn't sure whether it would come 'home' to its take-off position. I also realised that I did not know its orientation exactly, because it wasn't clear whether it had yawed at all during the way point execution. So I put it in PH/AH, and carefully tilted it side-to-side until I worked out its orientation. The gentle NE wind was pushing the 'copter away from me and toward the trees, so I decided not to attempt to bring it all the way back to its take off point, and instead reduce throttle and land it where it was.
Flight end 16.07
We picked up the 'copter and moved it back to its take-off point. I added a fifth waypoint, the original take-off position, so that it would move back. I checked the video and saw that indeed it was not pointing at the POI, but in the field I didn't know what could be wrong, and decided not to change any of the settings in case that created more problems than it solved!
Flight start 16.22
I uploaded all of the waypoints again, throttled up and took it to 10m, put it in PH/AH and then told it to execute the waypoints. Again it flew very smoothly through the waypoints. Each time it arrived at a student, they left a shoe where they were, and moved underneath the new position. After WP4, it came back to the take-off position, and I landed it carefully.
Flight end 16.26
When we looked at the distribution of positions, it was clear that the initial surveying was off by about 10m to the east - so each waypoint executed by the 'copter was 10m to the west of the original marked position. This implies that a car GPS it is only accurate to ~10m and we should keep that in mind for future surveying of waypoints.
On the plus side, the difference between the first pass of waypoints and the second was only about 1m, so the 'copter GPS seems to be much more reliable than the car GPS.
Lessons
I started by looking at the Google Maps image of the site, and picked a simple square pattern for the 'copter to execute. I attempted to set a point-of-interest just 10m north of the starting point, so that the 'copter would always be facing us. I borrowed a video camera from Curtin IT services to mount on the 'copter, so that we would be able to see what it saw after the flight. We brought a large bright orange cordon of flags which we could leave in a heap at the POI, so that we could see how much its position varied during the video. We also brought a car GPS which could give us the latitude and longitude of a position, so that we could mark it and see whether it and the 'copter agreed. I was assisted by Brian Crosse and several summer school students: Teresa, Zeus, Kimberley and Luke.
Weather was mostly sunny, 32 C with a very light NE breeze.
First we surveyed all of the waypoints, to make sure that I had selected them correctly from Google Maps, and the 'copter wasn't going to disappear over the horizon or into the trees! Brian and the four students went around each waypoint in turn, and a student stayed at each surveyed position. I put the 'copter in the take-off position, 10m north of my own position.
Flight start 16.04
I switched on the transmitter power, then the 'copter, and then connected it to MK Tool and uploaded the waypoints. I then calibrated the 'copter, then brought it up to about 10m altitude, put it in PH/AH for a few seconds to check everything was working, and then put it into 'come home' mode, which causes it to execute its programmed waypoints.
It moved off smoothly along each waypoint, but I could see that it was not yawing to point the camera mount at the POI, instead continuing to point North throughout. As it went to each waypoint, the relevant student left a shoe in the surveyed position, and moved to stand directly underneath the 'copter as it hovered at the waypoint.
Once it reached WP4, it simply stayed in position - I wasn't sure whether it would come 'home' to its take-off position. I also realised that I did not know its orientation exactly, because it wasn't clear whether it had yawed at all during the way point execution. So I put it in PH/AH, and carefully tilted it side-to-side until I worked out its orientation. The gentle NE wind was pushing the 'copter away from me and toward the trees, so I decided not to attempt to bring it all the way back to its take off point, and instead reduce throttle and land it where it was.
Flight end 16.07
We picked up the 'copter and moved it back to its take-off point. I added a fifth waypoint, the original take-off position, so that it would move back. I checked the video and saw that indeed it was not pointing at the POI, but in the field I didn't know what could be wrong, and decided not to change any of the settings in case that created more problems than it solved!
 |
| Flying past Curtin Stadium. |
I uploaded all of the waypoints again, throttled up and took it to 10m, put it in PH/AH and then told it to execute the waypoints. Again it flew very smoothly through the waypoints. Each time it arrived at a student, they left a shoe where they were, and moved underneath the new position. After WP4, it came back to the take-off position, and I landed it carefully.
Flight end 16.26
When we looked at the distribution of positions, it was clear that the initial surveying was off by about 10m to the east - so each waypoint executed by the 'copter was 10m to the west of the original marked position. This implies that a car GPS it is only accurate to ~10m and we should keep that in mind for future surveying of waypoints.
On the plus side, the difference between the first pass of waypoints and the second was only about 1m, so the 'copter GPS seems to be much more reliable than the car GPS.
Lessons
- Car GPS is only accurate to ~10m, may not be adequate for waypoint-surveying
- 'Copter GPS is accurate to ~1m and it can reach this in low-wind conditions
- The 'copter does not come 'home' after executing its waypoints - you must also program in a final 'home' position
- Something is not working with the POI functionality, despite apparently enabling the correct options in MK Tool - needs investigation.
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