Over the past week I’ve been spending some time building and setting up our new ArduCopter Quad. Although our ultimate goal is to develop a fully autonomous hexacopter we decided to use the quadcopter frame to familiarize ourselves with the ArduCopter code and hardware. To simplify the building process a mikrokopter hexakopter frame was used and assembled in a quad formation. Plates were custom made from HDPE sheets to mount the electronics on. The power system consists of 4 880 kV motors, 30 Amp jDrones ESCs and 12 x 4.5 props. XBees are being used to provide wireless telemetry.
After building the copter and setting up/loading the code I was able to start adjusting the PID gain values. To help with this process, which often involves a good amount of crashing I had decided to build a testing rig out of two eye hooks, 20lb test fishing line, a lead fishing sinker and a metal coat hanger. The hanger was mounted to the quad’s frame so that the fishing line could be tied to it and support the quad near its CG. The fishing line was threaded through the two eye hooks which were mounted to the ceiling. The sinker was tied to the end of the string after the second eye hook such that at its lowest point it was 2 feet off the ground. As the quad took off the sinker pulled the line taught to get rid of any extra slack in the line. If anything were to happen to the quad in flight I could simply cut the power and let the line catch it. This setup allowed the quad to fly freely without running the risk of hitting the ground or getting the fishing line caught in a prop.
Once the copter had begun to stabilize itself I decided to cut the support line and do some test flights, all of which went without any problems. Because it was dark outside and the grass was wet I had decided to just fly in stabilization mode under my carport. I was able to get the quad to the point where all you had to do was throttle up and it would fly itself (picture of it flying on the left, no strings attached I swear : ). I was so confident in the quads performance that I let my dad try it out and he was able to fly it (he had never flown an airplane or helicopter on his own before). Tomorrow I’ll take it out back to start playing with the loiter and altitude lock modes. I was able to get GPS lock tonight but haven’t started up the XBees. As we’ve found in the past XBees know no limits when it comes to being stubborn.
I’ve also been looking into waypoint navigation with the ArduCopter system and it seems that ArduPirates has successfully developed a roundabout way for flying waypoints. This involves editing the ArduCopter’s GPS lock code with predefined waypoints and inserting loop counters for each waypoint to indicate the amount of time spent at a given location. So essentially your still in GPS lock but switching up the home location throughout the flight.
I have a video as well but I can’t seem to get it to copy to my computer. Once I figure it out I’ll upload that was well. I’ll update the blog as I continue to make progress.