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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! 

Modified the Yak-54 Foam Model RC Plane

After the bad crash which has caused nose to break apart from the fuselage, I get to know about a few mistakes/disadvantages in the current design that I did as a beginner. Those are:- less distance between propeller tip to ground and weak motor mount to foam. As I'm still lacking of good landing technique, whenever it lands, the prop would hit the ground and results the second problem where motor mount comes out of foam.

Decreasing the prop size might not be a good solution. So, I decided to shift entire nose part up making the model to become a low wing plane and to make stronger motor mount. It's just a 'trial and error' experiment. So, I started doing a motor mount made of wood with 4 short CF tubes (which I had saved some extra pieces when I was making gliders previously).     

Yak-54 35" Depron Foam Model Build Log- Part 4



Continuing the build log of Yak-54 model. As per said in the post before, after a hard landing which has caused the motor mount and landing gear mount to break, I've further modified the model to have less frontal area, strengthened the landing gear attachment with foam, redid the motor mount.

Yak-54 35" Depron Foam Model Build Log- Part 3

Two days ago, I started creating a mount for motor. Glued 2 wooden sticks to wooden motor mount as shown in the next image. These sticks will be glued to the foam which is cut at half-depth. This will make motor mount structure much strong. 



Yak-54 35" Depron Foam Model Build Log- Part 2

Today, I've started working on the airframe where it is mainly built out of compressed white foam and foam with black colouring at one of its sides. We're building it in our hostel (residential college), College 10, UPM.  As per stated in the first part of this build log, I've downloaded the plan/template for this model, printed it out, cut the templates(wings, stabilizers, fuselage) and pasted onto the foam. Since, I've planned to make a different fuselage structure, I did some extra work beyond those plans over that template.

Fuselage has internal width of 2 inches and gets smaller in size as it approaches the stabilizers. Thickness of the foam used is 6mm. So, here is the picture of the non-assembled electronic items, transmitter unit, and Phoenix RC Simulator which I bought from RCSmart. Captured with 2MP Nokia classic phone.


Yak-54 35" Depron Foam Model Build Log- Part 1

The depron foam model of Yak-54 has a wingspan of 35". It is a aerobatic 3D plane and able to hover, hang vertically in flight (due to thrust produced by electric motor mounted on nose), do torque rolls and tail touches. 


You can download pdf plans of this plane from link 1 or link 2. I'm going with the 35" plan in first link. We should use lighter electronic components for this kind of model which you can buy from the nearest RC hobby shops. For us in Malaysia, there are various RC hobby shops in Klang Valley but, I prefer RCSmart which is located in Amcorp Mall, Petaling Jaya because it's the nearest to my university and easiest to reach (Taman Jaya LRT station in front Amcorp Mall). We are using the following electronic components bought from RCSmart.

1) Brushless motorTower Pro 2408-21 black
2) Electronic Speed Control - Emax 20A ESC for brushless motors
3) 9 gram servos (x4)
4) 11.1V 3S 1300mah 25C Li-Po battery
5) Fly Sky 8-channel Receiver unit
6) FlySky TH9X Transmitter unit

The following image shows basic electronic circuit for remote controlled aircraft.

However, we're going to modify the flat single-foam fuselage shown in the plan into thicker fuselage with compartment inside it for the ease of electronic parts placement. Hoping to build something like shown in the image below. 




 

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