Todd L. Braman

Honeywell gun-hard inertial measurement unit (IMU) development

Honeywell has designed and manufactured a gun-hard IMU that provides the baseline for meeting the needs of DoD guided tactical munitions, as well as being a platform for commercial usage. The gun-hard IMU is a solid-state inertial sensor package that measures and provides inertial angular rates and linear accelerations in a body-mounted strap-down mechanization. Its compensated outputs include summed and incremental angle and velocity data for inertial guidance, as well as angular rates and linear accelerations for autopilot/control functions. The data are reported in user-defined coordinates at 600 Hz and 100 Hz (typically) through a digital serial interface bus. The unit contains three Honeywell MEMS silicon gyroscopes, three Honeywell MEMS silicon accelerometers, as well as the electronics and software necessary to implement the requirements of the tactical market. The Honeywell gun-hard IMU development team includes multiple Honeywell sites and Draper Laboratories. In 2003, Honeywell demonstrated IMU survival and performance above 10,000 gs. In 2004, Honeywell will produce and deliver an IMU that will survive and perform at 20,000 gs. In addition to providing gun-hard survivability and high performance, Honeywell will capitalize on its extensive production experience to ensure a device that is cost effective for Honeywell customers.

Designing Vibration and Shock Isolation Systems for Micro Electrical Machined Based Inertial Measurement Units

Inertial Measurement Units (IMUs) using MEMS (Micro Electro Mechanical Systems) sensors, to detect rotation and acceleration, are extremely sensitive to vibration and shock. Because these IMUs are used in aircraft, missiles, and even in gun launched projectiles, the vibration and shock levels can be extremely high. We have been successful in designing isolation systems that protect the MEMS sensors from these harsh environments. These isolation systems attenuate the shock and vibration in frequency ranges that would otherwise degrade IMU performance and even damage the sensors. In designing an isolation system, for an IMU with MEMS devices, the designer must first acquire a good definition of the shock and vibration environment to which the IMU will be exposed. Then the designer must determine the frequencies and levels to which the MEMS devices are sensitive. Finally the designer must have knowledge of IMU properties such as resonant frequencies, mass properties, clock frequencies, etc. By knowing all of this information, and how it affects IMU performance, the designer can determine the proper parameters for the isolation system. A well designed isolation system using these parameters will be capable of protecting the MEMS devices while maintaining IMU performance through out all specified environments.