Does the Android Operating System Provide what the MEMS-IMU Manufacturers Promise?

Beside the camera, MEMS IMUs (Micro Elector-Mechanical Systems) belong today to the standard sensor conglomerate that every smartphone should have. In the future, the importance of MEMS-IMUs will increase more and more, especially if we talk about smart cities or internet of things (IoT). Since the MEMS manufacturer care only about numbers, i.e., low-cost, size and power consumption, some hardware and software integration deficits are highly likely to happen during the assemblage of the cell phone. This paper aims to check the quality of the consumer-grade smartphone IMUs from the user point of view. This includes the communication between the Android OS and the motion sensor. Additionally, a laboratory calibration of a couple of Xiaomi Mi 8 smartphones together with the same IMU-chip provided directly from the manufacturer has been performed. Referring to the spec. sheets, the outcome of the calibration (i.e., bias, scale factor and non-orthogonality errors) reveals, that the quality of both accelerometer and gyroscope parameters outperforms the manufacturer specifications. However, the only parameter that failed during this test is the bias error of the gyroscope. Further analysis of the stochastic processes show an unexpected behavior in the accelerometer z-axis for all employed smartphones, which can be caused by the electromagnetic compatibility or power supply regulation issues.