My last two blog entries discussed demonstrations of gyroscopes and angular momentum conservation at our school’s science fair. One of the demonstrations I put together takes a look at how really small gyroscopic sensors, such as those in many smart phones, video game remotes or quad-copters provide information about their changing orientations. This information can be used as feedback for self-balancing (e.g. a two-wheeled scooter), navigation or as input to other applications like video games.
I didn’t want to sacrifice my smart phone for this experiment. Fortunately, chips containing gyroscopic sensors are relatively cheap. In reading up on gyroscopic chips, I found that orientation data from gyroscope sensors is prone to drift significantly over time, so gyroscopic sensors are frequently combined with additional sensors, such as accelerometers or magnetometers to correct for this effect. This combination of sensors is frequently referred to as an IMU, or “Inertial Measurement Unit”, and it is used in airplanes, spacecraft, GPS navigators (for use when GPS signals are unavailable) and other devices. The number of of sensor inputs in an IMU are referred to as “DOF” (Degrees of Freedom), so a chip with a 3-axis gyroscope and a 3-axis accelerometer would be a 6-DOF IMU.