Its been a pretty slow week in terms of meaningful progress on the project. A few tough assignments during the week and a couple of tests meant I was pretty distracted by my studies and my Arduinos still haven’t arrived which is depressing. I contacted the seller and he’s resending them, chalking it down to the previous shipment being lost. But my first toy quad copter did arrive. However, the end result was kinda disappointing and I will discuss why exactly this week. I will also do a bit deeper analysis on the on-board hardware required for the quad-copter.
First look at a quad-copter
I have to be honest, before this project, I knew very little about quad-copters. In fact, this week was the first time I ever flew one. So I had no idea what to expect. When I opened the package, I immediately realized that the size I had gotten is probably too small for the application of the project. I tested it out as well and my suspicions were confirmed. Although it looks a decent enough design, this particular brand uses smaller propellers, weaker motors and a less sophisticated motor control system. The big advantage of learning from this toy was the fact that it uses a 6-axis gyroscope to orientate itself when flying. So although it feels hard to control, the copter is capable of performing some complex manoeuvres. However, its not all bad, the communication channels are still the same as most other RC UAV’s so I can still make use of it to reverse-engineer the RC communication protocol to work with my system. That will be my next step as I concurrently attempt to procure a more suitable toy quad-copter to use for my first prototype before expanding to the multiple system implementation.
The experience of flying the quad-copter was interesting. On one hand, I had to be pretty brave and full throttle it at first to get it off the ground, but there was massive drifts which meant that the copter kept smashing into walls. But the dynamics discussed last week were successfully verified in practice. In fact, it was also clearly perceivable that the in-flight drift was caused by the rotors spinning at different speeds. It is quite conceivable that if better speed control of the rotors can be achieved, the overall stability of the quad copter can be greatly improved. The size of this particular design meant that much emphasis was given to aerial agility and manoeuvrability, but for the purposes of this project, a normal 6 degree of freedom implementation should be appropriate. Indeed, the quad copter might not be needed to rotate if it can be programmed to execute turns in tight angles.
A look inside the copter casing revealed how simple the design for this particular copter is. The absence of ESC (Electronic Speed Controller) means that the speed control for each motor is most likely PWM. Considering also that this copter is a low power application, this leads to inaccuracies in motor speed control. Thus it explains why it is so hard to control and use for beginners. It took me a couple of days to truly get the hang of it, and yet I still have trouble sometimes. But, by far the most disappointing problem was that this copter is very light weight and low powered, so it can’t really carry any sort of payload. Add to that the small dimensions of the quad copter also means that it will be hard to modify and improve. The thrust of the copter could possible be improved by using a higher powered motors and possibly with wider propellers with a larger tilt angle, but in reality this changes are hard to implement and will most likely be cancelled out by the extra weight of the components added.
The following is a brief breakdown of the components of the copter and their specifications:
– Battery: – 3.7V; 300mAh Li-Ion rechargeable battery [45bmins charging time; approximately 8~12 mins flight time]
– MCU :- Nuvoton MINI54ZAN
– Propellers: 6cm diameter with 30 degree tilt; 2 x counter-clockwise propellers (negative tilt) and 2 x clockwise propellers (positive tilt)
– DC motor: Unsure of manufacturer; 5VDC low power motor [roughly about 3W calculated from battery usage]
– 6-axis Gyroscope
– Radio Transceiver :- NRF24L01 2.4GHz Antenna wireless transceiver
– LED Indicators
– Plastic Frame
I’ve already been scouting for a more powerful quad copter and it seems that the prices literally double. I will purchase one soon and will most like be assembling the rest of the quad-copters in the team from separate parts. But until I get the new copter, I will proceed to learning about the communication channels that are used for RC control for the quad-copter and try to emulate them on the Arduino. My radio transceivers will arrive soon and I can work on the hardware aspect with this quad copter first (i.e. use my arduino to replace the function of the remote control). While I wait for the materials to arrive, I will commence with basic structure of the programming for the RC communicaiton. More updates to come next week. Till then have a great week and enjoy the Fifa World Cup!