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2020-03-13 12:33 pm
Hi,
I am trying to get my rover bot to wander around the living room. But I need to keep track of where it is and its heading. (SLAM ?) So I need more info on using the various imu/pmu/compass breakout boards and chips. In particular, I do not understand how to convert output from a imu magnetometer into a compass heading that ranges from 0-360 degrees.
My R&D rover system is 3.3 volts. ESP32 and RPI-zero-ws.
So, more content with IMU in the context would be great !
Best regards,
Phil
2020-03-19 5:59 pm
Phil,
I have only used the Honeywell HMC5883L stand-alone compass rather than an IMU but the basic principals should be the same. I found a few good Honeywell technical documents that explain the equations in getting angles 0-360 or North,NE,East, etc.
Search for these pdf's
Caruso, Michael "Applications of Magnetoresistive Sensors in Navigation Systems"
Caruso, Michael "Applications of Magnetic Sensors for Low Cost Compass Systems"
AN-203 "Compass Heading Using Magnetometers."
It looks like you want to do Dead Reckoning. You use wheel encoders to track your speed and tire revolutions. The compass can give you a heading with respect to North. With my robot if I want it to turn right say 35 degrees I speed up left motor, slow right motor, and start integrating (summing) the signal from the gyroscope until it reaches the 35 target. Then the motors adjusted to go straight (zer0 output from gyro). So with the compass, gyro (or IMU) , and encoders you got a basic start. Keep in mind the errors in both the heading and location will build-up the farther it goes to the point it is way off. I think that is where the "L" in SLAM comes in.