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.

Attitude and gyro bias estimation by the rotation of an inertial measurement unit

Abstract: In navigation applications, the presence of an unknown bias in the measurement of rate gyros is a key performance-limiting factor. In order to estimate the gyro bias and improve the accuracy of attitude measurement, we proposed a new method which uses the rotation of an inertial measurement unit, which is independent from rigid body motion. By actively changing the orientation of the inertial measurement unit (IMU), the proposed method generates sufficient relations between the gyro bias and tilt angle (roll and pitch) error via ridge body dynamics, and the gyro bias, including the bias that causes the heading error, can be estimated and compensated. The rotation inertial measurement unit method makes the gravity vector measured from the IMU continuously change in a body-fixed frame. By theoretically analyzing the mathematic model, the convergence of the attitude and gyro bias to the true values is proven. The proposed method provides a good attitude estimation using only measurements from an IMU, when other sensors such as magnetometers and GPS are unreliable. The performance of the proposed method is illustrated under realistic robotic motions and the results demonstrate an improvement in the accuracy of the attitude estimation.

Line transfer system for airplane

Abstract: A method is provided for establishing a physical reference inside an airplane representing the airplane's optimized line of flight based on the as-built orientation of aerodynamically significant features of the airplane. Values generated for aerodynamic pitch, roll and yaw representing the optimized line of flight are used to orient a tool reference surface outside the airplane. The orientation of the tool reference surface is recorded using an inertial reference unit placed on the tool reference surface. The tool reference surface and inertial reference unit are moved into the airplane where they are used to establish the physical reference on the airframe.

Computational Elements for Strapdown Systems

Abstract: This paper provides an overview of the primary strapdown inertial system computational elements and their interrelationship. Using an aircraft type strapdown inertial navigation system as a representative example, the paper provides differential equations for attitude, velocity, position determination, associated integral solution functions, and representative algorithms for system computer implementation. For the inertial sensor errors, angular rate sensor and accelerometer analytical models are presented including associated compensation algorithms for correction in the system computer. Sensor compensation techniques are discussed for coning, sculling, scrolling computation algorithms and for accelerometer output adjustment for physical size effect separation and anisoinertia error. Navigation error parameters are described and related to errors in the system computed attitude, velocity, position solutions. Differential equations for the navigation error parameters are presented showing error parameter propagation in response to residual inertial sensor errors (following sensor compensation) and to errors in the gravity model used in the system computer. COORDINATE FRAMES As used in this paper, a coordinate frame is an analytical abstraction defined by three mutually perpendicular unit vectors. A coordinate frame can be visualized as a set of three perpendicular lines (axes) passing through a common point (origin) with the unit vectors emanating from the origin along the axes. In this paper, the physical position of each coordinate frame’s origin is arbitrary. The principal coordinate frames utilized are the following: B Frame = "Body" coordinate frame parallel to strapdown inertial sensor axes. N Frame = "Navigation" coordinate frame having Z axis parallel to the upward vertical at the local position location. A "wander azimuth" N Frame has the horizontal X, Y axes rotating relative to non-rotating inertial space at the local vertical component of earth's rate about the Z axis. A "free azimuth" N Frame would have zero inertial rotation rate of the X, Y axes around the Z axis. A "geographic" N Frame would have the X, Y axes rotated around Z to maintain the Y axis parallel to local true north. E Frame = "Earth" referenced coordinate frame with fixed angular geometry relative to the rotating earth. I Frame = "Inertial" non-rotating coordinate frame.

Inertial measurement system

Abstract: An apparatus for measuring an inertial property on a set of one or more axes is disclosed. The apparatus includes a first inertial sensor arranged to measure the inertial property, having a first predetermined resolution and a first predetermined measurement range, and a second inertial sensor arranged to measure the inertial property, having a second predetermined resolution and a second predetermined measurement range. The second resolution is coarser than the first and the second measurement range is larger than the first. A processing system is adapted to receive measurement signals from the first and second inertial sensors and, when the output of the first inertial sensor is within the first predetermined measurement range, to update an error estimate for adjusting the output of the second inertial sensor, based on the measurement signals from the first and second inertial sensors.

Inertial sensor unit

Abstract: The unit has a number of miniaturised inertial sensors arranged so that they are subjected to the same inertial measurement parameter. The signals from the inertial sensors are fed to the same signal processor for generating an output measurement signal representing the inertial measurement parameter. Each inertial sensor contains a miniaturised resonator, whose resonance characteristic is influenced by the inertial measurement parameter. A number of measurement sensors with different measurement ranges can be used for measurement over an extended measurement range.