SBIR-STTR Award

Microelectromechanical systems (MEMS) inertial (motion) sensors are now used for a wide range of consumer and industrial applications, but cant be used for many precision navigation applications because of their inaccuracy. In particular, the measurement (bias) stability of MEMS gyroscopes generally have temperature sensitivities of 10-100 degrees/hour/degree Celsius. This mean that even with small outside temperature chances, these sensors have difficulty achieving the 1 degree/hour instabilities of much larger and more expensive fiber optic gyroscopes. Furthermore, changes in stress (which can also be temperature dependent) also have significant effects on device performance. The proposed environmentally stabilized IMU (eIMU) will address this through improvements in its micromachined thermal/stress isolation package. This package holds the IMU (consisting of 3 gyroscopes and 3 accelerometers) at a constant temperature during operation and isolates them from changing outside stresses. The technical challenges include: (i) further optimizing the package design to eliminate thermal and stress gradients; (ii) eliminating materials and processes which can result in long term sensor drift and; (iii) optimizing the sensor performance and the oven control algorithms.

IMUs consist of 3 accelerometers (which measure motion in a straight line) and 3 gyroscopes (which measure angle changes). Working together with the correct software, they can be used for navigation and orientation measurements in a wide range of applications. Microelectromechanical systems (MEMS) inertial (motion) sensors are now used for a wide range of consumer, industrial and automotive applications, but cant be used for higher performance applications because of their extreme environmental sensitivityespecially to temperature. In particular, the measurement (bias) stability of consumer grade gyroscopes can be up to 80 degrees per hour per degree Celsius. This means that even with small outside temperature changes, these sensors cannot maintain bias repeatability of under 20 degrees per hour required for many tactical navigation applications. The proposed environment resistant inertial measurement unit (eIMU) addresses this by applying a stress isolation and thermal control package around a MEMS IMU in order to: 1) maintain a constant temperature during operation and 2) isolate it from humidity and outside stresses in the environment. The technical challenges include: i) choosing the optimal IMU for packaging in order to address military applications; and ii) improving the package design for better stress/thermal isolation and better stress repeatability.