Navigation Using Inertial Sensors

This tutorial provides an introduction to navigation using inertial sensors, explaining the underlying principles. Topics covered include accelerometer and gyro technology and their characteristics, strapdown inertial navigation, attitude determination, integration and alignment, zero updates, motion constraints, pedestrian dead reckoning using step detection, and fault detection

Navigation System Design with Application to the Ares I Crew Launch Vehicle and Space Launch Systems

For a launch vehicle, the Navigation System is responsible for determining the vehicle state and providing state and state derived information for Guidance and Controls. The accuracy required of the Navigation System by the vehicle is dependent upon the vehicle, vehicle mission, and other consideration, such as impact foot print. NASAs Ares I launch vehicle and SLS are examples of launch vehicles with are/where to employ inertial navigation systems. For an inertial navigation system, the navigation system accuracy is defined by the inertial instrument errors to a degree determined by the method of estimating the initial navigation state. Utilization of GPS aiding greatly reduces the accuracy required in inertial hardware to meet the same accuracy at orbit insertion. For a launch vehicle with lunar bound payload, the navigation accuracy can have large implications on propellant required to correct for state errors during trans-lunar injection

Passive, free-space heterodyne laser gyroscope

Laser gyroscopes making use of the Sagnac effect have been used as highly accurate rotation sensors for many years. First used in aerospace and defense applications, these devices have more recently been used for precision seismology and in other research settings. In particular, mid-sized (~1 m-scale) laser gyros have been under development as tilt sensors to augment the adaptive active seismic isolation systems in terrestrial interferometric gravitational wave detectors. The most prevalent design is the 'active' gyroscope, in which the optical ring cavity used to measure the Sagnac degeneracy breaking is itself a laser resonator. In this article, we describe another topology: a 'passive' gyroscope, in which the sensing cavity is not itself a laser but is instead tracked using external laser beams. While subject to its own limitations, this design is free from the deleterious lock-in effects observed in active systems, and has the advantage that it can be constructed using commercially available components. We demonstrate that our device achieves comparable sensitivity to those of similarly sized active laser gyroscopes

Vektorisuunnistukseen perustuva sisätilapaikannusjärjestelmä

In this thesis a positioning system, that can provide accurate reference coordinates for indoor usage is described and analysed. Those coordinates are needed in the development of various indoor positioning systems. Satellite navigation systems such as GPS can provide accurate positioning outdoors but their accuracy is poor when used indoors. Inertial navigation can provide accurate positioning indoors using accelerometers and gyroscopes but an accurate system is extremely expensive. Accurate indoor positioning is also achievable using a floor plan, a measuring tape or both but these methods are prone to human errors. The system presented in this thesis is designed to overcome the aforementioned problems using dead reckoning navigation. Dead reckoning is a positioning method, that starts always from a known location and attitude. In dead reckoning, gyroscope and odometer measurements are used to obtain position by updating the previous position. The dead reckoning system uses a micro electro mechanical (MEMS) gyroscope and two odometers to measure attitude and travelled distance, respectively. A data acquisition program was written to save their measurements to log files on a PC and position was computed by post processing those. The system has been mounted on a cart for easy transportation. Before testing accuracy of the system the gyro and odometers were calibrated. The gyro was attached to a turn table to calibrate its scale factor and bias. From the turn table study it became obvious that the gyro needs to be calibrated just before testing accuracy of the system. Odometers were calibrated by driving the cart in a known straight line distance several times. Based on the drives a scale factor was calculated to compensate the difference in odometer readings. The gyro scale factor was calibrated just before accuracy test of the system by turning the cart around several times. The accuracy of the system was tested in a test drive lasting 30 minutes. During the test the gyro bias was calibrated whenever the system was stopped at reference positions for positioning accuracy estimation. Positioning error of less than 30 cm was achieved in the test drive.Tässä työssä kehitettiin ja analysoitiin tarkka sisätilapaikannusjärjestelmä. Sitä voidaan käyttää tarkkojen koordinaattien määrittämiseen, joita tarvitaan kehitettäessä muita sisätilapaikannusjärjestelmiä. Satelliittipaikannusjärjestelmiä, kuten GPS:ää, voidaan käyttää ulkotiloissa tarkkojen koordinaattien määrittämiseksi, mutta sisällä niiden tarkkuus on heikko. Tarkkaan sisätilapaikannukseen soveltuvat esimerkiksi gyroskooppeja ja kiihtyvyysantureita käyttävät inertiapaikannusjärjestelmät, mutta ne ovat erittäin kalliita. Pohjapiirustusta, mittanauhaa tai molempia voidaan käyttää tarkkaan sisätilapaikannukseen, mutta niitä käytettäessä tulee tehtyä helposti virheitä. Työssä esitetty vektorisuunnistusjärjestelmä on suunniteltu ratkaisuksi edellä mainittuihin ongelmiin. Vektorisuunnistus on paikannusmenetelmä, joka alkaa aina tunnetusta sijainnista ja suunnasta. Siinä käytetään gyroskoopin ja matkamittarin mittauksia paikan määrittämiseksi päivittämällä edellinen sijainti. Työssä esitetty järjestelmä käyttää mikromekaanista (MEMS) gyroskooppia suunnan määrittämiseksi ja kahta matkamittaria kuljetun matkan mittaamiseksi. Mittausten lukemiseksi antureilta kirjoitettiin tietokoneohjelma, joka tallensi ne lokitiedostoihin. Järjestelmän sijainti määritettiin jälkikäteen käyttäen lokitiedostoihin tallennettuja mittauksia. Järjestelmä on kiinnitetty kärryyn, jotta sitä on helppo kuljettaa sisätiloissa. Järjestelmän gyroskooppi ja matkamittarit kalibroitiin ennen sen tarkkuuden tutkimista. Skaalauskertoimen ja biaksen määrittämiseksi gyroskooppi kiinnitettiin pyörityspöytään. Kalibrointituloksista kävi ilmi, että gyroskooppi täytyy kalibroida juuri ennen järjestelmän tarkkuuden tutkimista. Matkamittarit kalibroitiin työntämällä kärryä suoraan tunnetun pituinen matka, jonka mittaus toistettiin useampia kertoja. Mittausten perusteella määritettiin skaalauskerroin, jolla kompensoitiin matkamittareiden lukemissa havaittu ero. Gyroskoopin skaalauskerroin kalibroitiin juuri ennen järjestelmän tarkkuuden tutkimista pyörittämällä kärryä useampi kerta ympäri. Järjestelmän tarkkuutta tutkittiin koeajossa, joka kesti 30 minuuttia. Koeajon aikana gyroskoopin bias kalibroitiin aina pysähdyttäessä tunnetuissa sijainneissa paikannustarkkuuden tutkimiseksi. Paikannusvirhe koeajon aikana oli alle 30 cm

CMOS systems and circuits for sub-degree per hour MEMS gyroscopes

The objective of our research is to develop system architectures and CMOS circuits that interface with high-Q silicon microgyroscopes to implement navigation-grade angular rate sensors. The MEMS sensor used in this work is an in-plane bulk-micromachined mode-matched tuning fork gyroscope (M² – TFG ), fabricated on silicon-on-insulator substrate. The use of CMOS transimpedance amplifiers (TIA) as front-ends in high-Q MEMS resonant sensors is explored. A T-network TIA is proposed as the front-end for resonant capacitive detection. The T-TIA provides on-chip transimpedance gains of 25MΩ, has a measured capacitive resolution of 0.02aF /√Hz at 15kHz, a dynamic range of 104dB in a bandwidth of 10Hz and consumes 400μW of power. A second contribution is the development of an automated scheme to adaptively bias the mechanical structure, such that the sensor is operated in the mode-matched condition. Mode-matching leverages the inherently high quality factors of the microgyroscope, resulting in significant improvement in the Brownian noise floor, electronic noise, sensitivity and bias drift of the microsensor. We developed a novel architecture that utilizes the often ignored residual quadrature error in a gyroscope to achieve and maintain perfect mode-matching (i.e.0Hz split between the drive and sense mode frequencies), as well as electronically control the sensor bandwidth. A CMOS implementation is developed that allows mode-matching of the drive and sense frequencies of a gyroscope at a fraction of the time taken by current state of-the-art techniques. Further, this mode-matching technique allows for maintaining a controlled separation between the drive and sense resonant frequencies, providing a means of increasing sensor bandwidth and dynamic range. The mode-matching CMOS IC, implemented in a 0.5μm 2P3M process, and control algorithm have been interfaced with a 60μm thick M2−TFG to implement an angular rate sensor with bias drift as low as 0.1°/hr ℃ the lowest recorded to date for a silicon MEMS gyro.Ph.D.Committee Chair: Farrokh Ayazi; Committee Member: Jennifer Michaels; Committee Member: Levent Degertekin; Committee Member: Paul Hasler; Committee Member: W. Marshall Leac

Scout fourth stage attitude and velocity control (AVC) system feasibility study

The feasibility of incorporating a guidance system in the Scout fourth stage to achieve a significant improvement in expected payload delivery accuracy is studied. The technical investigations included the determination of the AVC equipment performance requirements, establishment of qualification and acceptance test levels, generation of layouts illustrating design approaches for the upper D and payload transition sections to incorporate the hardware, and the preparation of a vendor bid package. Correction concepts, utilizing inertial velocity and attitude, were identified and evaluated. Fourth stage attitude adjustments as determined from inertial velocity variation through the first three stages and a final velocity correction based upon the measured in-plane component errors at injection were employed. Results show radical reductions in apogee-perigee deviations

Performance Analysis Of Strapdown Systems

ABSTRACT This paper provides an overview of assorted analysis techniques associated with strapdown inertial navigation systems. The process of strapdown system algorithm validation is discussed. Closed-form analytical simulator drivers are described that can be used to exercise/validate various strapdown algorithm groups. Analytical methods are presented for analyzing the accuracy of strapdown attitude, velocity and position integration algorithms (including position algorithm folding effects) as a function of algorithm repetition rate and system vibration inputs. Included is a description of a simplified analytical model that can be used to translate system vibrations into inertial sensor inputs as a function of sensor assembly mounting imbalances. Strapdown system static drift and rotation test procedures/equations are described for determining strapdown sensor calibration coefficients. The paper overviews Kalman filter design and covariance analysis techniques and describes a general procedure for validating aided strapdown system Kalman filter configurations. Finally, the paper discusses the general process of system integration testing to verify that system functional operations are performed properly and accurately by all hardware, software and interface elements. 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. 1 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 earth. I Frame = "Inertial" non-rotating coordinate frame. NOTATION V = Vector without specific coordinate frame designation. A vector is a parameter that has length and direction. The vectors used in the paper are classified as "free vectors", hence, have no preferred location in coordinate frames in which they are analytically described

High-accuracy Motion Estimation for MEMS Devices with Capacitive Sensors

With the development of micro-electro-mechanical system (MEMS) technologies, emerging MEMS applications such as in-situ MEMS IMU calibration, medical imaging via endomicroscopy, and feedback control for nano-positioning and laser scanning impose needs for especially accurate measurements of motion using on-chip sensors. Due to their advantages of simple fabrication and integration within system level architectures, capacitive sensors are a primary choice for motion tracking in those applications. However, challenges arise as often the capacitive sensing scheme in those applications is unconventional due to the nature of the application and/or the design and fabrication restrictions imposed, and MEMS sensors are traditionally susceptible to accuracy errors, as from nonlinear sensor behavior, gain and bias drift, feedthrough disturbances, etc. Those challenges prevent traditional sensing and estimation techniques from fulfilling the accuracy requirements of the candidate applications. The goal of this dissertation is to provide a framework for such MEMS devices to achieve high-accuracy motion estimation, and specifically to focus on innovative sensing and estimation techniques that leverage unconventional capacitive sensing schemes to improve estimation accuracy. Several research studies with this specific aim have been conducted, and the methodologies, results and findings are presented in the context of three applications. The general procedure of the study includes proposing and devising the capacitive sensing scheme, deriving a sensor model based on first principles of capacitor configuration and sensing circuit, analyzing the sensor’s characteristics in simulation with tuning of key parameters, conducting experimental investigations by constructing testbeds and identifying actuation and sensing models, formulating estimation schemes is to include identified actuation dynamics and sensor models, and validating the estimation schemes and evaluating their performance against ground truth measurements. The studies show that the proposed techniques are valid and effective, as the estimation schemes adopted either fulfill the requirements imposed or improve the overall estimation performance. Highlighted results presented in this dissertation include a scale factor calibration accuracy of 286 ppm for a MEMS gyroscope (Chapter 3), an improvement of 15.1% of angular displacement estimation accuracy by adopting a threshold sensing technique for a scanning micro-mirror (Chapter 4), and a phase shift prediction error of 0.39 degree for a electrostatic micro-scanner using shared electrodes for actuation and sensing (Chapter 5).PHDMechanical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttps://deepblue.lib.umich.edu/bitstream/2027.42/147568/1/davidsky_1.pd

Strapdown Miniature Electrostatic Gyro /SDMEG/ development and evaluation Final report, 1 Jun. 1965 - 28 Mar. 1969

Feasibility study for strapdown electrically suspended gyroscope in attitude reference system for spacecraf

Attitude Determination Method by Fusing Single Antenna GPS and Low Cost MEMS Sensors Using Intelligent Kalman Filter Algorithm

For meeting the demands of cost and size for micronavigation system, a combined attitude determination approach with sensor fusion algorithm and intelligent Kalman filter (IKF) on low cost Micro-Electro-Mechanical System (MEMS) gyroscope, accelerometer, and magnetometer and single antenna Global Positioning System (GPS) is proposed. The effective calibration method is performed to compensate the effect of errors in low cost MEMS Inertial Measurement Unit (IMU). The different control strategies fusing the MEMS multisensors are designed. The yaw angle fusing gyroscope, accelerometer, and magnetometer algorithm is estimated accurately under GPS failure and unavailable sideslip situations. For resolving robust control and characters of the uncertain noise statistics influence, the high gain scale of IKF is adjusted by fuzzy controller in the transition process and steady state to achieve faster convergence and accurate estimation. The experiments comparing different MEMS sensors and fusion algorithms are implemented to verify the validity of the proposed approach