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.

Realtime assessment of foot orientation by Accelerometers and Gyroscopes

Abstract: Abstract Foot orientation can be assessed in realtime by means of a foot-mounted inertial sensor. We consider a method that uses only accelerometer and gyroscope readings to calculate the foot pitch and roll angle, i.e. the foot orientation angle in the sagittal and frontal plane, respectively. Since magnetometers are avoided completely, the method can be used indoors as well as in the proximity of ferromagnetic material and magnetic disturbances. Furthermore, we allow for almost arbitrary mounting orientation in the sense that we only assume one of the local IMU coordinate axes to lie in the sagittal plane of the foot. The method is validated with respect to a conventional optical motion capture system in trials with transfemoral amputees walking with shoes and healthy subjects walking barefoot, both at different velocities. Root mean square deviations of less than 4° are found in all scenarios, while values near 2° are found in slow shoe walking. This demonstrates that the proposed method is suitable for realtime application such as the control of FES-based gait neuroprostheses and active orthoses.

Environmentally mitigated navigation system

Abstract: An environmentally mitigated navigation system includes a thermal isolating chamber, an inertial measurement unit that can include individual gyroscopes and accelerometers for making inertial measurements, and a temperature control system; the temperature control system includes a thermoelectric cooling system, which in a powered mode maintains the inertial measurement unit at a substantially predetermined temperature, and a phase change device for maintaining the inertial measurement unit or inertial sensors at substantially a predetermined temperature in an unpowered mode; the phase change device substantially maintains the predetermined temperature by changing phase to define a stable temperature window for the inertial measurement unit or individual sensors to make inertial measurements during the unpowered mode as well as during the powered mode.

Quaternion based attitude estimation algorithm applied to signals from body-mounted gyroscopes

Abstract: An application of inertial sensing to gait analysis is described: the attitude estimation algorithm computes the attitude quaternion associated with a body part, i.e. the foot instep moving in the inertial space, by employing a spherical linear interpolation procedure to compensate for the errors due to the influence of the gyroscope bias. The effectiveness of the approach is demonstrated by simulations.

Development of a Wearable Device for Motion Capturing Based on Magnetic and Inertial Measurement Units

Abstract: This paper presents a novel wearable device for gesture capturing based on inertial and magnetic measurement units that are made up of micromachined gyroscopes, accelerometers, and magnetometers. The low-cost inertial and magnetic measurement unit is compact and small enough to wear and there are altogether thirty-six units integrated in the device. The device is composed of two symmetric parts, and either the right part or the left one contains eighteen units covering all the segments of the arm, palm, and fingers. The offline calibration and online calibration are proposed to improve the accuracy of sensors. Multiple quaternion-based extended Kalman filters are designed to estimate the absolute orientations, and kinematic models of the arm-hand are considered to determine the relative orientations. Furthermore, position algorithm is deduced to compute the positions of corresponding joint. Finally, several experiments are implemented to verify the effectiveness of the proposed wearable device.

Calibration of an internal sensor system

Abstract: A calibration device for establishing a 3-D reference frame for an inertial sensor system. A secondary mounting surface on the calibration device is used to provide a measurement of the reference line required for inertial system installation alignment. This device provides a means for establishing a highly accurate alignment of inertial system sensors relative to the output coordinates, called the "mounting frame", without a requirement for optics or a manual transfer of data. By rotating the inertial sensor system through use of a rate table into planes which are substantially perpendicular to each other, the mounting frame for the sensor system can be established.