Development of a MEMS IMU with optimized SWaP-C

Northrop Grumman LITEF GmbH (NG LITEF) started the development of microelectromechanical systems (MEMS) gyroscope chips with Deep Reactive Ion Etching (DRIE) in 2003. Based on this technology, a six degree of freedom MEMS IMU (LITEF MEMS IMU1) was developed, consisting of three separate gyroscope and accelerometer chips. After successful transfer from early MEMS IMU prototypes to series production, NG LITEFs IMU1 is available since many years with a specified bias error of 4 $^{\circ}/\mathrm{h}$ and an angular random walk (ARW) of 0.15 $^{\circ}/{\mathrm{h}}$ over temperature. The concept of IMU1 is based on three single gyroscope and accelerometer modules. In order to reduce the number of signal lines from the central signal processing board of the IMU1 to the single modules, a MEMS gyroscope chip concept with a minimized set of electrodes was selected. The multiplexing of the electrodes combined with the high requirements on the IMU regarding performance results in a complex operating scheme with several auxiliary control loops. This places high demands on the front-end electronics and digital signal processing, and therefore requires a high level of computing power. In the recent years, NG LITEF has focused on the development of IMU-NG with optimized SWaP-C (Size, Weight, Power, and Cost), while preserving the IMU performance. By optimizing the digital signal processing and by integrating the front-end electronics into an application-specific integrated circuit (ASIC), the power consumption was reduced by a factor of three. Additionally, the volume of the IMU-NG is scaled down from 340 $\mathrm{cm}^{3}$ to 113 $\mathrm{cm}^{3}$ by optimizing the existing assembly & packaging concept and due to the miniaturization of the readout electronics. Based on these activities, ARW, velocity random walk (VRW) and bias error are in a comparable range to the actual NG LITEF MEMS IMU1 without the need of redesigning the MEMS chips. In this work, gyroscope performance below 0.1 $^{\circ}/\mathrm{h}$ bias instability and accelerometer bias instability of 3 $\mu \mathrm{g}$ can be presented. The paper covers the development of the IMU-NG with the improved assembly & packaging concept and the integration of the readout electronics into an ASIC. Furthermore, it provides an outlook to the next MEMS IMU improvements and further MEMS inertial sensor development activities planned at NG LITEF over the next four years.