![]() Moving a vector around in three-dimensional space can be a complicated affair. Sometimes that calibration requires an external EEPROM. Whichever sensor you use, you must calibrate the device according to the manufacturer's datasheet prior to every use. The focus of the article is on the mathematics, not the sensor. However, the mathematics presented here should work with any sensor system. ![]() Interested readers might like to know that Bosch replaced this IMU with the BMX055. I am using this IMU because I have one on hand from a previous article on how to capture data with the BNO055. In this article, I will describe a rotation matrix and present some of the mathematics required to configure the Bosch BNO055 IMU for the purposes of dead-reckoning. Quaternions are preferred because they require less computation by an MCU. The way to do this is with rotation matrices whose individual elements are populated with trigonometric functions or quaternions. Once your sensor is aligned in the inertial frame, you can align your data. You usually have to align your sensor with your inertial reference frame to be able to interpret the data. If you are not careful, you will end up making calculations with data that is mixed among multiple axes of movement.Ī calibrated sensor still needs to be aligned with an inertial reference to make the data truly useful. All of that data is completely useless unless you can find a way to relate the IMU’s frame of reference to a fixed, external reference frame.ĭata from uncalibrated sensors are useless.Īnd once you figure out how to stabilize the data in an inertial reference frame, misaligned axes can still wreak havoc on all of your hard work. IMU data is useless unless you know how to interpret it.įor example, the BNO055 is a 9DOF sensor that can provide acceleration, gyroscopic, and magnetometer data, as well as fused quaternion data that indicates absolute orientation from an initial position. Working with IMUs can maddening for a variety of reasons, but what scares people the most is usually the math. ![]()
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