Setting up "Throttle Mid Position" for Good Altitude Hold and Loiter Performance - Arducopter

Based on my experience of nearly one year involving in the development of hexacopter platform powered by Arducopter firmware, I have discovered that if the hexacopter is able to perform well in altitude hold mode followed by a good loiter performance, it wouldn't have much problems to be flown autonomously. If you have problem on that, probably one of the tricks to solve it would be try setting up the "Throttle Mid Position".

Initially, I was using six 2212-13 1000kV brushless motors with 10x4.5 props which gave me a decent thrust of 0.6kg each. During its first flight itself, the platform was able to hover nicely at 50% throttle. I only had to tune the altitude hold P value for better performance. After several crashes during following flight tests, eventually the motor shafts were severely bent. 

Then, I switched to Tiger Motor MT 2216-11 900kv brushless motors. That time, my air frame weight was a bit higher (nearly 2.6kg) with additional payload attachments to the air frame such as video transmitter, payload drop mechanism, landing gear, camera and some optional components. During its first flight it hovered at 70% throttle. When I switched to altitude hold mode instantly, it would just shoot up and when I position throttle at middle, it descends.

UAV Siswa Challenge 2013/2014

It has been nearly one year since the UAV Siswa Challenge started. I represented Universiti Putra Malaysia under team Icarus along with three other friends of mine from Deparment of Aerospace Engineering. There were two teams (Icarus and Langit Biru UPM) selected from Universiti Putra Malaysia to be among the 10 finalists for the competition. Initially, we had to submit a proposal, followed by a closed presentation and interview session by juries from Dassault Aviation France, CTRM and MIGHT before teams of 10 finalists were chosen and awarded with complete multi-rotor development kit.

We were given nearly 8 months for building, testing and preparing hexacopter platform to conduct required missions during two rounds of final competition which was held in Universiti Putra Malaysia on 22nd and 23rd March 2014. We had learnt a lot of things throughout our journey of 8 months preparing our hexacopter platform. Beyond the technical knowledge we gained to upload the firmware, configurations to be made, performance tuning, we did also acquired a better ability of working as a team, project management, problem solving and decision making skills. Personally, myself as a person who was more comfortable working alone, came to understand the advantages of being as a team and distributing the task among the team members. Things just get easier, better and simpler solutions can be generated from a brainstorming session and collaboration between team members.

Earlier stages of the progress after receiving the kit was really slow because we had to test and understand the individual components and systems that we were provided with. Technical problems would just pop-up at anytime, where we had to crack our head thinking and searching for solutions on web. And if we don't find any solutions, our best friend, "Trial and Error" method was always there for us.

Once everything was set up, it was time to start flying. We had only one airframe with costly electronic components on-board with some spare propellers.  We had zero experience in flying remote control aircrafts/ multirotors. A lift-off from the ground at that time was a great challenge for us. Afraid of losing airframe, we waited for guidance from professional flyers. Luckily there was someone who helped us with that. A local RC hobbyist who had nearly 8 years experience of flying multi-rotors lend his hand to us. After listening to some encouraging words from him, we gained confidence to take-off the hexacopter and had a decent hover flight. Well, that ended up with some bumpy landing. But, HAHA! I did land it without breaking the propellers or damaging the airframe! Continuous support from the local RC hobbyist really kept us moving when we faced big problems. Thanks to him.

Continuous flight practice built more confidence inside us. We started moving on testing different flight modes and started tuning hexacopter for good performance. Few days before technical presentation,  the luck was not on our side. We had a disastrous crash. We were testing an auto mode flight. Very low experimental P value for stabilizing parameter was the reason for that. Yet, we managed to buy a new body kit and prepared the hexacopter overnight and resumed the flight test next morning. We also managed to do well during the technical presentation which was held in MIGHT office in Cyberjaya.

Our working hour shot up as the competition day was nearing. We were testing and debugging our custom made image processing algorithm and additional software functionalities to be used during the competition rounds. More and more flight test was carried out in the outdoor area. Flight performance was tuned. We tested our payload drop mechanisms. 

Finally, the competition day, 22nd March 2014, arrived. We were performing well on the first day of competition. During the training session late evening on that day preparing for our challenge on the next day, we had to face another disastrous crash of our hexacopter platform when we tested our custom code to send automated commands from Ground Station via telemetry. The propellers stopped spinning on-air and platform fell like a rock from a height of 7 meters damaging our payload drop mechanism, our only landing gear and hexacopter arm. At that time, we had three problems to solve. First, we had to repair our hexacopter platform. Second, we had to recreate our payload drop mechanism. Third, we had to debug the code for sending command from Ground Stations. Fourth, we needed to test the code and make it really work or we would be disqualified from second round. Everything had to be done within an overnight.

Nearing a situation of losing hope for the second round, we tried to calm ourselves for some hours. With some moral support from our team supervisors and the local RC hobbyist, we managed to motivate ourselves. Clock started ticking. 8 more hours left. An intensive teamwork aided by quick and critical thinking of team members, we managed to revive our airframe, re-built the payload drop mechanism and debugged the code. The final flight test to verify the performance of code was done just one hour before the real competition begun. Thanking the god. It worked like charm. We managed to complete the mission for that day. Though, we had to fly a bit slower due to uncertainty in the cause of the great crash we had. Our second trial during second round was a bit shocking though, after we tuned the parameters for a faster performance, once again, the hexacopter fell from a height of 5 meters. Luckily, there was no any severe damages to the airframe.

The final results of the competition will be announced in mid-April. The entire journey and experiences gained during the commencement of UAV Siswa Challenge 2013/2014 will remain as an unforgettable moments of my undergraduate life. Here I would like to thank Dassault Aviation, Malaysian Ministry of Higher Education, CTRM, MIGHT, for coming up with an event of first of its kind in Malaysia for university students.

I would like to also thank Universiti Putra Malaysia, our team supervisor Assoc. Prof. Lt. Col. (R) Mohamed Tarmizi Ahmad, Dr. Omar Kassim Ariff, RC hobbyist Mr.Arif and my team members for their unlimited support throughout the competition.

Now, anxiously waiting for the results to be announced....

Note: More pictures are on the way!