Audio & signal processing

9 axis MotionTracking® combines gyroscope, accelerometer, and TMR magnetometer sensor data. The resulting angular frame is relative to both gravity (down) and north.

The advantages of 9 axis MotionTracking® over 6 axis MotionTracking® are that 9 axis MotionTracking® results are usable for navigation and other applications which require information about the angle relative to north. It also eliminates any heading drift which may be present in a 6 axis MotionTracking® solution so that users are pointed in the correct direction without delay due to recalibration. 

Because 6 axis MotionFusion has no way to directly sense the earth’s magnetic field, it estimates heading by integrating the gyroscope sensor outputs. The gyroscope sensor will have some small amount of noise and may have small biases. Since the technique of gyroscope integration keeps a running sum of gyroscope sensor outputs and those sensor outputs include small errors, the sum will slowly accumulate an error over time. 6-axis MotionFusion can only correct part of this error using information from the accelerometer.

Both accelerometers and magnetometers are noisy sensors, which means they exhibit a slow response rate (due to noisy filtering) in fast moving systems. Accelerometer measurements are also affected by motion. By using a gyroscope and MotionFusion, the MotionFusion solution will have a faster response rate and track small, quick movements much more quickly. Gyroscope MotionFusion also makes it possible to sense linear acceleration separately from gravity.

The Embedded MotionApps Platform provides MotionFusion of three axis gyroscope and three axis accelerometer data. The result is an angular frame which is relative to gravity (down). On its own, a three axis accelerometer can be used to find an angular frame relative to gravity. However, because accelerometers detect the sum of linear acceleration and gravity, an accelerometer cannot provide an accurate angular frame solution when it is in motion, which makes it unusable in many applications. By fusing the gyroscope with accelerometer, Embedded MotionApps delivers a stable angular frame solution which precisely follows the device motion.

With the Embedded MotionApps Platform, for 6-axis MotionFusion, ‘forward’, is the direction when the device initializes. Subsequent MotionFusion solutions will be described relative to this initial forwards direction.

9 axis MotionFusion combines gyroscope, accelerometer, and magnetometer sensor data. The resulting angular frame is relative to both gravity (down) and north. 9 axis MotionFusion is not available in Embedded MotionApps Platform at this time.

The advantages of 9 axis MotionFusion over 6 axis MotionFusion are that 9 axis MotionFusion results are usable for navigation and other applications which require information about the angle relative to north. It also eliminates any heading drift which may be present in a 6 axis MotionFusion solution.

The Embedded MotionApps Platform software is not intended for use on an operating system, but it is possible. For use on Android or Linux operating systems, the MotionApps Platform Library is recommended.

Our sensors support I²C, SPI, and UART interfaces for easy integration with microcontrollers and embedded systems.

Each sensor has a defined accuracy and resolution specified in the datasheet. For instance, some motion sensors can detect changes as small as 0.001g.