Apr 24, 2011

Quadrocopter - Part 4 - Spinning out of Control

In the previous post i mentioned that i needed gyroscopic sensors and accelerometers to stabilize the quadrocopter.For more detail on these sensors visit Gyroscope and Accelerometer. Basically what i'll be doing is using these sensors find out the orientation of the quadrocopter relative to the ground. With this data i can adjust the speed of the various motors (using something called as PID Controller) to stabilize the quadrocopter in a particular orientation. Now to move the quadrocopter in any direction you adjust the speed of any one (or all) the motors so as to get the proper direction of motion. For more info on how a quadrocopter actually flys go here.

There are two ways (that i have thought of) to obtain these sensors:
               1) Buy it off the self
               2) Salvage it from any commercially available product that already has these sensors (such as the PS3 Move, Nintendo Wii, iPod Touch, your new touchscreen phone,etc.

Both ways have their advantages and disadvantages.

Buying off the self makes it very easy to interface the sensors with any micro-controller but it is expensive when compared to the alternative.Salvaging it from a consumer device is tricky and requires a bit of hacking but is less expensive depending on what device you use.I decided to go for the second option.

Now i had four choices of devices:

  • My iPod Touch 1st Gen
  • My Phone (Samsung Wave S8500)
  • PS3 Move 
  • Nintendo Wii
I gave up on the iPod and the phone because they did not have a gyroscope sensor (kind of important) plus i did not want to seem them destroyed if CPUV crashes. So i decided to go with the PS3 Move or the Wii. I was leaning towards the Move as it also had a 3-Axis magnetometer but after some help form Kenn Sebesta (http://www.eissq.com/ps3_move/) i found out that i would need a programmer for the onboard STM32 chip to get it to work for the quadrocopter. I would have to write a custom firmware into the chip as the current firmware switches off the entire controller as soon as it goes out of Bluetooth range ( going to happen in my case). The programmer costs about $20 in the use but shipping it to India the price including shipping goes up over $60 which is a problem. For $60 (about Rs.3000) i could get myself a decent 6-Ch RF controller which is also necessary. 

So i decided to go with the Wii. I will use the gyros in the Wii Motion Plus and the accelerometers in the Wii Nunchuck for the project as of now. Working on the Move would have been awesome but sadly the cost involved is too high for something that i can do without. I will try to upgrade the quadrocopter later but as of now in sticking with the Wii.

Wii Motion Plus

Wii Controller + Nunchuck 


PS3 Move


Links to part 1 ,part 2 & part 3