SIRU development. Volume 1: System development

A complete description of the development and initial evaluation of the Strapdown Inertial Reference Unit (SIRU) system is reported. System development documents the system mechanization with the analytic formulation for fault detection and isolation processing structure; the hardware redundancy design and the individual modularity features; the computational structure and facilities; and the initial subsystem evaluation results

Solar array flight experiment/dynamic augmentation experiment

This report presents the objectives, design, testing, and data analyses of the Solar Array Flight Experiment/Dynamic Augmentation Experiment (SAFE/DAE) that was tested aboard Shuttle in September 1984. The SAFE was a lightweight, flat-fold array that employed a thin polyimide film (Kapton) as a substrate for the solar cells. Extension/retraction, dynamics, electrical and thermal tests, were performed. Of particular interest is the dynamic behavior of such a large lightweight structure in space. Three techniques for measuring and analyzing this behavior were employed. The methodology for performing these tests, gathering data, and data analyses are presented. The report shows that the SAFE solar array technology is ready for application and that new methods are available to assess the dynamics of large structures in space

Comparative in-flight thrust measurements of the SERT 2 ion thruster

Comparative in-flight thrust measurements of SERT 2 ion thrusto

Software requirements: Guidance and control software development specification

The software requirements for an implementation of Guidance and Control Software (GCS) are specified. The purpose of the GCS is to provide guidance and engine control to a planetary landing vehicle during its terminal descent onto a planetary surface and to communicate sensory information about that vehicle and its descent to some receiving device. The specification was developed using the structured analysis for real time system specification methodology by Hatley and Pirbhai and was based on a simulation program used to study the probability of success of the 1976 Viking Lander missions to Mars. Three versions of GCS are being generated for use in software error studies

SIRU Development. Volume 4: Accelerometer Module

No abstract availabl

The Limits of In-run Calibration of MEMS and the Effect of New Techniques

Inertial sensors can significantly increase the robustness of an integrated navigation system by bridging gaps in the coverage of other positioning technologies, such as GNSS or Wi-Fi positioning [1]. A full set of chip-scale MEMS accelerometers and gyros can now be bought for less than $10, potentially opening up a wide range of new applications. However, these sensors require calibration before they can be used for navigation[2]. Higher quality inertial sensors may be calibrated “in-run” using Kalman filter-based estimation as part of their integration with GNSS or other position-fixing techniques. However, this approach can fail when applied to sensors with larger errors which break the Kalman filter due to the linearity and small-angle approximations within its system model not being valid. Possible solutions include: replacing the Kalman filter with a non-linear estimation algorithm, a pre-calibration procedure and smart array [3]. But these all have costs in terms of user effort, equipment or processing load. This paper makes two key contributions to knowledge. Firstly, it determines the maximum tolerable sensor errors for any in-run calibration technique using a basic Kalman filter by developing clear criteria for filter failure and performing Monte-Carlo simulations for a range of different sensor specifications. Secondly, it assesses the extent to which pre-calibration and smart array techniques enable Kalman filter-based in-run calibration to be applied to lower-quality sensors. Armed with this knowledge of the Kalman filter’s limits, the community can avoid both the unnecessary design complexity and computational power consumption caused by over-engineering the filter and the poor navigation performance that arises from an inadequate filter. By establishing realistic limits, one can determine whether real sensors are suitable for in-run calibration with simple characterization tests, rather than having to perform time-consuming empirical testing

Flight test results of the Strapdown hexad Inertial Reference Unit (SIRU). Volume 1: Flight test summary

Flight test results of the strapdown inertial reference unit (SIRU) navigation system are presented. The fault-tolerant SIRU navigation system features a redundant inertial sensor unit and dual computers. System software provides for detection and isolation of inertial sensor failures and continued operation in the event of failures. Flight test results include assessments of the system's navigational performance and fault tolerance

The Limits of In-Run Calibration of MEMS Inertial Sensors and Sensor Arrays

MEMS accelerometers and gyroscope triads now cost less than $10, potentially opening up many new applications. However, these sensors require calibration prior to navigation use. This paper determines the maximum tolerable sensor errors for in-run calibration techniques using a basic Kalman filter by developing criteria for filter failure and performing Monte Carlo simulations for a range of different sensor specifications, and both car and UAV motion-profiles. Gyroscope bias is found to be the most significant with the maximum tolerable value of its SD varying between 0.75 and 2.6 deg/s depending on the value of the specification of the other sensor sources. The paper shows that pre-calibration and smart array techniques could potentially enable in-run calibration to be applied to lower-quality sensors. However, the estimation of scale-factor cross-coupling and gyroscope g-dependent errors could potentially be critical. Armed with this knowledge, designers can avoid both unnecessary design complexity and computational load of over-engineering and the poor navigation performance of inadequate filters

Application of inertial instruments for DSN antenna pointing and tracking

The feasibility of using inertial instruments to determine the pointing attitude of the NASA Deep Space Network antennas is examined. The objective is to obtain 1 mdeg pointing knowledge in both blind pointing and tracking modes to facilitate operation of the Deep Space Network 70 m antennas at 32 GHz. A measurement system employing accelerometers, an inclinometer, and optical gyroscopes is proposed. The initial pointing attitude is established by determining the direction of the local gravity vector using the accelerometers and the inclinometer, and the Earth's spin axis using the gyroscopes. Pointing during long-term tracking is maintained by integrating the gyroscope rates and augmenting these measurements with knowledge of the local gravity vector. A minimum-variance estimator is used to combine measurements to obtain the antenna pointing attitude. A key feature of the algorithm is its ability to recalibrate accelerometer parameters during operation. A survey of available inertial instrument technologies is also given

Flight test results of the Strapdown hexad Inertial Reference Unit (SIRU). Volume 3: Appendices A-G

Results of flight tests of the Strapdown Inertial Reference Unit (SIRU) navigation system are presented. The fault tolerant SIRU navigation system features a redundant inertial sensor unit and dual computers. System software provides for detection and isolation of inertial sensor failures and continued operation in the event of failures. Flight test results include assessments of the system's navigational performance and fault tolerance. Selected facets of the flight tests are also described in detail and include some of the following: (1) flight test plans and ground track plots; (2) navigation residual plots; (3) effects of approximations in navigation algorithms; (4) vibration spectrum of the CV-340 aircraft; and (5) modification of the statistical FDICR algorithm parameters for the flight environment