Ring laser gyroscopes typically consist of in-run bias stabilities ranging anywhere from 1 °/hour down to less than 0.001 °/hour, encompassing the tactical and navigation grades. Quartz and MEMS gyroscopes are typically used in the consumer grade, industrial grade, and tactical grade markets, while fiber-optic gyroscopes spanĪll four of the performance categories. Gyroscopes, fiber-optic gyroscopes (FOGs), ring laser gyroscopes (RLGs), and quartz/MEMS gyroscopes. There are many different types of gyroscopes available on the market, which range over various levels of performance and include mechanical To learn more about the operation of a MEMS accelerometer see Section 1.3, or to understand the various specifications associated with selectingĪ suitable accelerometer for your application please refer to Section 3.1 of the VectorNav Inertial Navigation Primer.Ī gyroscope is an inertial sensor that measure an object's angular rate with respect to an inertial reference frame. To a linear acceleration along the sensitivity axis, the acceleration causes the proof mass to shift to one side, with the amount of deflection proportional to the acceleration. The mass is known as the proof mass and the direction that the mass is allowed to move is known as the sensitivity axis. ACCELEROMETERĪn accelerometer is the primary sensor responsible for measuring inertial acceleration, or the change in velocity over time, and can be found in a variety of different types, including mechanical accelerometers, quartz accelerometers, and MEMS accelerometers.Ī MEMS accelerometer is essentially a mass suspended by a spring, as illustrated in Figure 2. Let’s dive into the specific sensors used in an IMU, namely an accelerometer and gyroscope. Below is a table the illustrates the difference between the VN-100 industrial grade device and the VN-110 tactical grade device. VectorNav offers two grades of IMU that are based on MEMS accelerometers and gyroscopes. Table 1 : Performance Grades of Inertial Sensors GRADE The table below summarizes the performance of the These performance categories are typically defined based on the in-run bias stability of the sensor, as the in-run bias stability plays such a large role in determining inertial navigation performance. They are divided into one of the four categories based on the specifications of the accelerometer and gyro: IMUs are available in several performance grades. You can learn more about how an AHRS works in Section 1.6 of the Inertial Navigation Primer.īy ArnoldReinhold - Own work, CC BY-SA 4.0, Figure 1: Apollo Inertial Measurement Unit The addition of a magnetometer and filtering algorithms to determine orientation information results in a device known as an Attitude and Heading Reference Systems (AHRS). Magnetometers (optional): measurement of the magnetic field surrounding the system.Accelerometers: providing a measure specific force/acceleration.Gyroscopes: providing a measure angular rate.An Inertial Measurement Unit (IMU) is a device that can measure and report specific gravity and angular rate of an object to which it is attached.
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