FreeIMU

heading calculation with gyro

Asked by okan uyar

Hi,
I'm an phd student in TURKEY.
Firstly, I like much your free IMU project.
I want to measure Pitch,Roll and Heading with PIC(microchip) via your freeimu board( Is marketing of this board continue and can you ship it to TURKEY).
After measurement, I will convert the values to analog data for using it with PLC.
Can you give me some advice for this usage( reading with PIC and converting it to analog value).
I have also LPR530AL,LISY300AL,ADXL335 and work on this purpose.These
sensors give analog info so I don't need D/A conversion.
But I couldn't measure the heading without using magnetometer. I try to avoid usage of magnetometer because of hard-soft iron effects. (I will use this sensors in industrial area. So there is a lot of disturbance.)
My Gyro sensor(LISY300) produce analog signal according to the angular-rate for instance. How can I use this information to calculate the heading.
Because gyro produce the signal for instance and then return to reference value.
Thanks in advance

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Fabio Varesano (fabio-varesano) said : 		#1

Hi,

Yes, FreeIMU is going to be commercialized again. You can get it from the shops listed at http://www.varesano.net/projects/hardware/FreeIMU#get .. currently they are out of stock but they be back soon.

Without a magnetometer, your heading informations will be affected by drifting of the gyro. With time, your calculation of the heading will be incorrect. If this is not a problem, you can use this code: http://www.x-io.co.uk/res/sw/madgwick_algorithm_c.zip See MahonyAHRS.c function MahonyAHRSupdateIMU.

That function will expect a gyro x, y, z readings expressed in rad/s and accelerometer x,y,z readings. So, you have to sample your analog sensors using your ADC, if you are using Arduino that's the analogRead() function. Read this guide http://www.starlino.com/imu_guide.html to understand how to convert an analog reading into a meaningful value for your sensor.

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