Showing papers on "Inertial measurement unit published in 1979"

Size Effect on Navigation Using a Strapdown IMU

Abstract: : Size effects in a strapdown IMU (Inertial Measurement Unit) are not always ignorable. They should be considered in the error budget for high accuracy inertial navigation. This report presents results of a study on size effects. It is found that while each individual accelerometer has only one type of size effect, an IMU has two in general, the 'mounting offset size effect' and the cluster size effect. General formulas for determining IMU size effect errors are developed in the report. Numerical examples, laboratory test results, and flight simulation results are given to demonstrate the size effects and to reveal their effect on navigation error. It is discussed that an optimum orientation for the accelerometer cluster can be chosen to minimize the navigation errors caused by size effects. It is also shown that, in principle, size effect of an IMU can be compensated using the angular rate information available from gyros. A size effect compensation concept is proposed with the associated computation algorithm given.

Missile-x/third generation inertial instrument characterization test program

Abstract: The Third Generation Inertial Instruments were selected by the Charles Stark Draper Laboratories for the Missile-X Inertial Measurement Unit (IMU) called the Advanced Inertial Reference Sphere (AIRS). These instruments are the Third Generation Gyroscope (TGG) and the Specific Force Integrating Receiver (SFIR). A Characterization Test Program was developed to provide performance measurement of the instruments. A list of characterization tests was formulated and prioritized. Standard test plans and procedures were developed and tests run at multiple test agencies to characterize the instruments and to evaluate test station differences using the concept of a standard test instrument. The characteristics of instruments are being tabulated and stored in an instrument data bank which is a computer system mechanized for storing and retrieving test results. The results are being used to provide error budget/capability estimates to describe MX weapon system performance. This paper describes the mechanization and implementation of this program.

Navigation systems for approach and landing of VTOL aircraft

Abstract: The formulation and implementation of navigation systems used for research investigations in the V/STOLAND avionics system are described. The navigation systems prove position and velocity in a cartestian reference frame aligned with the runway. They use filtering techniques to combine the raw position data from navaids (e.g., TACAN, MLS) with data from onboard inertial sensors. The filtering techniques which use both complementary and Kalman filters, are described. The software for the navigation systems is also described.

Low-cost inertial navigation for moderate-g missions

Abstract: A low cost inertial navigation system (INS) concept is described for flight missions characterized by moderate accelerations and limited attitude variations. These missions involve general aviation aircraft, helicopters, or remotely piloted vehicles. The significance of the moderate acceleration and limited attitude is reviewed with respect to platform mechanization and instrumentation. A hybrid mechanization, partially gimballed and partially strapdown, is presented. The INS is implemented by an unbalanced two axis gimbal system and controlled by a two degree of freedom gyro. The INS provides locally level two axis acceleration information along with pitch and roll measurements. Heading information is provided by a second gyro mounted in the inner gimbal. The system error model is equivalent to that of a conventional platform with a tilt error determined by the integral of the gyro drift rate and an equivalent accelerometer type errors are also cancelled. Rapid gyro-compassing, implemented with opened gimbal control loops, and a strapdown procedure provides calibration of gyro drift rate biases.