New-Tech Europe Digital Magazine | Feb 2016

30 mg (~2 deg roll/pitch error) are not an exception in low-cost MEMS sensors. Gyroscopes biases of up to 30 deg/s are also possible, although most gyroscopes biases are between -5 and 5 deg/s. A calibration improves the gyroscope bias repeatability up to +/- 0.5 deg/s, whereas accelerometer biases are limited to 2 mg (0.1 deg roll/pitch error). Mounting a module on another board does not influence the calibration parameters. As modules are simultaneously tested during calibration, production yield of the end-user application is significantly improved. The capital investments for a calibration and test setup are significant, especially when the number of sensors per year is limited (under 10,000 units per year). In cases in which fewer than 10,000 units per year are required, the test and calibration costs already justify the higher price of a module. Electronics and Mechanical Design With magnetometers in many IMU designs, and with sensitive MEMS, the electronics design cannot be overlooked. Mechanical stress is

often specified for the relatively large MEMS sensors components, so this should be taken into account. When something changes in the MEMS sensor component itself, the PCB of the end-user application may need to be redesigned. A turnkey module solves all these issues as it comes on a PCB that does not change interface and pinning and relieves the user from mechanical stress calculations. Sensor Fusion Software Sensor fusion software is required to interpret MEMS sensor data as useful orientation data, should the application demand this. Although sensor fusion algorithms are documented in literature, it is not as straightforward as just taking data and applying a filter. The sensor fusion algorithms of Fairchild’s FMT1000 series modules are optimized for several different use case scenarios based on the decades of application experience of Xsens, an industry leader in motion tracking acquired by Fairchild. The sensor fusion algorithm can be processed with different sets of settings, such as dynamic, human

motion or high magnetic dependency. Performance testing on a wide range of test platforms ensures the best performance for many different applications. An added benefit of using Fairchild’s sensor fusion software is that the sensor fusion algorithm outputs different data in selectable output formats. Examples are free acceleration, where gravity is already subtracted; reference coordinate frames, for use in arbitrary alignment; and several fixed point and floating point output formats. Getting all this in a tested package will save you a lot of time and risk in the execution of your project. The motion tracking module was designed keeping in mind user requirements and application needs. The design and development process took into thorough consideration the various aspects of producing and delivering a robust and high performance motion tracker module.

50 l New-Tech Magazine Europe