As a follow-up to the rover drops #1 and #2 I spent a day with Assistant Professor Nagatani-san of Tohoku university in Japan (and his students) and Izu-san of EnRoute (a company that specialises in Industrial use multicopters and hobby use RC vehicles here in Japan and China) at Karuizawa's Mt Asama attempting to autonomously drop a 2.5kg rover from a large (4kg+) EnRoute "ZionPro" hexacopter.
The flight was completely autonomous including activating the servo release which held the rover to the hexacopter (we used the camera shutter release). After being released the rover was "lowered" on a 30m wire wound around a brushless motor which was meant to slow it's descent (with mixed results). If you've never heard of this mechanism before, it seems if you connect the bullet connectors of a brushless motor together it resists being turned. If you attach a resistor between the bullet connectors it will resist less strongly. In this way we could somewhat adjust the speed at which the rover descended at.
A couple of things that we learned from this test in case you try something similar:
- the altitude reported by a Ublox GPS (i.e. APM/PX4) vs a hand held GPS can vary by 10m.
- the altitude reported in google maps (and thus the mission planner) can vary by 20m from reality because they only provide the average altitude for the area. I'm not sure how big that area is but we found that google maps altitudes could be high or low from reality depending upon where you were on the slope.
- trying to drop from a wire is tough! we need a more reliable system for the next test. Maybe use a range finder to get the copter closer to the surface without hitting it or perhaps measure the motor output to determine when the dangling rover has reached the ground.
- the hexacopter and battery were more than sufficient to carry the rover the 600m covered in this test. At least twice that distance would have been possible.
- AC3.0.1 is very capable of the accuracy required for this mission. It was a thing of beauty.
There will be one more attempt within the next 2 months which should be pretty much the same except the distance will be further and the dropping mechanism will be improved!
Thanks and all comments, input welcome!
Comments
@Federico re what happens when the copter loses a lot of weight...in this case from looking at the CTUN logs, the moment that the rover was dropped the throttle output dropped from 80% to about 60%. Because of the fast reaction of the altitude hold though the copter moved less than a meter.
One correction, I was going through MP code again and you guys where right at the first time.
M.P. uses G.E. data when plotting the elevation graph, I wonder way it has a SRTM class?
Very cool. I loved the machine vanishing into the mist (onward, brave little traveler!) and the reappearing at the target.
Why wire? Why not some strong synthetic?
How do you program a landing with a first descend speed until altx and then another descend speed until toich down ?
Randy, here's another suggestion: Maybe the rover-release function could be allocated to the rover, which would release itself from the line when an on-board sonar sensor determines it is close enough to ground surface. The quad/hexacopter could have an attached spool of a known length of fishing line (with the copter end securely fastened), and a loop of line at the other end that slips over the shaft of a small solenoid on the rover. When the copter is in the desired location, it slowly descends until the rover's sonar triggers the solenoid, releasing the line and allowing the rover to drop to a surface. This approach could minimize the risk of damage to the rover, and maybe less risk of it tumbling down a slope.
It uses it because there is a simple way to acess it, and a single acess for the hole world. Here is the database: http://dds.cr.usgs.gov/srtm/version2_1/SRTM3/
I'm sure that if someone codes a new dataset MO would mind to integrate it.
Why does Mission Planner use SRTM data? The USGS elevation set with global coverage was GTOPO30 until it was superseded a few years ago by GMTED2010. GMTED2010 has 7.5 arc-second resolution everywhere except the poles, and for the south pole is has 30 arc-second resolution. For US coverage, the NED has 1/3 arc-second resolution. USGS also announced this month that they were making Canadian and Mexican data available (at 1 arc-second if I remember correctly). A few blogs ago someone mentioned using ArcGIS WMS to make SDE layers viewable in MissionPlanner. Maybe we could get higher-resolution elevation products.
several blogs ago there was a airplane that looks allot like a military drone, cannot recall the name, the four motors can rotate for forward flight or vertical flight.
@Jared
What "copter that transitions into an airplane"?
hey Arthur, the copter that transitions into an airplane, is that custom code?
-
1
-
2
-
3
-
4
of 4 Next