I have been testing the new sensor shield board for ArduPilot Mega. This new version (codename : Foxtrap2) comes with the IDG500 gyros from Invensense. Old board (and also ArduIMU) uses ST gyros. Well I had heard that Invensense gyros are more vibration resistance than ST´s (because the internal resonant frequency is much higher) so I decided to do a "real world" test.
As you can see the Invensense gyros are MUCH cleaner than ST´s. This is a nice performance for a vibration enviroment (real quad flight).
This is how I did the test:
- I mounted the two boards at the same time in a quadcopter (60cm size, 10x4.5 props)
- Register the raw sensor data in the DataFlash EEPROM at main loop rate (70Hz in this test) on each board
- In order to syncronize the two data sets I tap (with my finger) at the beggining and end of flight (this tap is clearly visible on data)
- I started increasing the throttle slowly and then made a 25 seconds hovering
I calculated the standard deviation of the gyros on the three steps (at rest, ground with motors on and hovering)
The results are VERY clear, the Invensense gyros are MUCH better in vibration resistance than ST´s. This are fantastic news!! and really worth the delay on the sensor shield!!
With this performance, in the case of a quad (and planes also), we can increase the gain of the gyro rate to increase the stability. (Usually the limit of the gain is the noise on the gyros).
Here is the full set of data with graphics (Excel file): Gyro_Test.zip
I have made several flights with this new shield and I´m very happy with the results, the quad shows a fantastic stability :-)
We have tested also the other components of this shield like the Dataflash EEPROM, the new barometer, the rele (for payloads), switches... We needed to make some minor changes (pin assignements) to some libraries (APM_ADC and DataFlash) and we are now developing the Arduino libraries for the barometer and the optional magnetometer.
Also in the final production of the board, Jordi will do some improvements in the ADC part adding a dedicated voltage regulator for gyros and accels because we discovered in this version that the I2C translator (for the barometer) add some noise to the system.
When I talked to Jordi he says that this IMU board should be available starting late next week.