I found an additional port on Pixhawk board scheme and came up with idea to connect a higher performance IMU (mostly accel and gyro) to autopilot in terms of my master thesis. My budget allows me to buy the system below 200$.
After making an overview on other (more expensive) autopilot's sensors like Micropilot or Mikrokopter, I decided to settle on Analog Device's (AD) inertial sensors. Going forward, I compared AD (30-50$) gyros with Pixhawk's MPU6000, and I was a bit surprised. The performances and measurements range of MPU was if not the same, but a bit higher. Maybe I am not that good in gyro's theory, but as I know the main characteristics are - Sensitivity, Sensitivity Tolerance, Scale range, Nonlinearity, Rate Noise Density and of course others, but these are basis. So check out the results:
Sensitivity 6mv/°/sec 80 LSB/°/s 131 LSB/º/s
Sensitivity Tolerance ±2% ±3% ±3%
Scale range ±300°/sec ±300°/sec ±250 °/sec
Nonlinearity 0.1% 0.05% 0.2%
Rate Noise Density(°/sec/√Hz) 0.05 0.015 0.005
And comparing for instance ADXL203 accelerometer to MPU's one doesn't bring the issue to the light.
So it looks like MPU not even cheaper, more adjustable and has the same or better performances, but also has an accelerometer inside. Of course I understand that AD sensors are suppose to be more reliable etc., but why is the price that different? There should be some other reasons that I have missed...
And eventually it leads me to the conclusion: are these expensive autopilots worth its money?
I think this issue will be interesting for a lot of users so I really hope on your replies!