Inertial reference unit

About: Inertial reference unit is a research topic. Over the lifetime, 1306 publications have been published within this topic receiving 22068 citations. The topic is also known as: IRU.

Hemispherical Resonator Gyro: an IRU for Cassini

Abstract: The JPL Inertial Reference Unit (IRU) is the single most sophisticated assembly on the Cassini spacecraft. At the core of the IRU is the state-of-the-art, Litton Hemispherical Resonator Gyro (HRG). Launched in October 1997, Cassini's trajectory utilizes gravity assist maneuvers around Venus (two), Earth, and Jupiter over a seven year period, arriving at Saturn in June 2004. Its tour of the Saturnian system will last an additional four years. Although the Stellar Reference Unit (SRU) provides the ultimate reference for the spacecraft Attitude and Articulation Control System (AACS) and can be used to control the spacecraft under benign conditions, the Cassini IRU is essential during maneuvers and fault recovery operations, and for precision attitude stabilization during science data acquisition. Therefore, IRU reliability over the long Cassini mission is a critical concern. Following an extensive evaluation of possible alternatives, the Hemispherical Resonator Gyro (HRG) based IRU developed by Litton Guidance and Control Systems, was chosen for the Cassini mission. The HRG is an attitude rate sensor that has no physical wear-out mechanisms. Based on a principle first described by G. H. Bryan (1890) in his paper, 'On Beats in the Vibrations of a Revolving Cylinder or Bell', the HRG is created by vibrating a quartz resonator. This paper discusses the theory and modifications required to the design of the standard Space Inertial Reference Unit to adapt it to meet the requirements of the Cassini mission and the AACS interface. The Cassini mission is the first use of an IRU for a deep space planetary mission that does not use a spun-mass sensor.

A method of calibrating inertial sensors

Abstract: A method of calibrating inertial sensors of working equipment, such as a vehicle or survey equipment, includes determining whether the working equipment is in operation or not. Data is captured from inertial sensors and associated temperature sensors while the working equipment is out of operation. The captured data is used to update a thermal bias error model for the inertial sensors.

Development of a MEMs-based IMU Unit

Abstract: In this study, gyroscope-free inertial measurement unit interface is developed to simulate new system configurations called YILDIZ using known calculation methods and implementation of MEMS accelerometers based on cubic arrangement. Additionally significant effect of different sensing directions and sensor allocations are taken into consideration. Throughout the project, simulation studies, realization of sample gyro-free MEMs-based INS systems, and collection of data through data acquisition systems are performed in given order. Using simulation of the system, parameter-dependent errors are aimed to be minimized on the system output. Then, near-ideal geometry and the sensor configurations can be reached and the system can be realized. Prototype outputs are processed and efficient algorithms are developed using Matlab-Simulink environment.

Heading stabilization for aided inertial navigation systems

Abstract: A method of stabilizing heading in an inertial navigation system is provided. The method includes operating an inertial measurement unit comprising horizontal-sensing elements and off-horizontal-sensing elements while the inertial measurement unit is in a first orientation, calibrating the horizontal-sensing elements of the inertial measurement unit based on horizontal aiding measurements, forward-rotating the inertial measurement unit by a selected-rotation angle about a horizontal-rotation axis so that the inertial measurement unit is oriented in a second orientation, operating the forward-rotated inertial measurement unit while the inertial measurement unit is in the second orientation, and calibrating the rotated off-horizontal-sensing elements based on horizontal aiding measurements while the inertial measurement unit is in the second orientation. When the inertial measurement unit is in the first orientation, the horizontal-sensing elements are oriented in a horizontal reference plane. When the inertial measurement unit is in the second orientation, the off-horizontal-sensing elements are oriented in the horizontal reference plane.

Wearable Inertial Sensors and Their Applications

Abstract: Wearable inertial sensors have been developed extensively over the past several years. Inertial sensors, including accelerometers, gyroscopic sensors, and magnetic sensors, can be embedded in the body, such as the trunk, leg, arm, etc., for monitoring the motion associated with human activities. In this chapter, we examine the technological principles of several types of inertial sensors, and provide an assessment and evaluation of these sensors for patient rehabilitation in clinical practice.