Multi-axis inertial measurement units measuring human posture and motion

This paper presents the development of systems monitoring human body motions and postures for clinical purposes. The hardware for these applications exploits a newly released commercial Micro-Electro-Mechanical (MEM) 3-axis accelerometer and a MEM 3-axis rate gyroscope being developed by HSG-IMIT. First the paper gives an overview of wearable 3-axis accelerometer systems and the corresponding data storage and transmission developed by ETB. The main part of the paper describes the design of the 3-axis rate gyroscope to be implemented in an Inertial Measurement Unit (IMU) for the body motion monitoring. Such health applications require IMUs of very low size to be able to fix the sensor cluster to the human being. This prevents the use of state-of-the-art IMUs implemented by three perpendicular orientated rate gyroscopes for this purpose. Thus a novel 3-axis rate gyroscope realised in one plane, on a single die, is being developed. With this device a reduction of the package size of multiaxial MEM sensors is achievable at least by a factor of ten. A further advantage of this approach is the reduced cost due to the omission of a spatial configuration and due to the small dimensions. Finally the synthesis of the 3-axis accelerometer and the 3-axis rate gyroscope to an IMU for monitoring 3D body segment orientation is addressed.