There exist numerous commercial six-degree-ofreedom inertial measurement units capable of measuring low-range accelerations and rotation rates. A commercially available multi-range IMU capable of measuring low and high-range motions does not exist. An IMU with this capability was developed for measuring trajectory data of projectiles such as high-powered rockets. This data can be used to provide performance feedback to projectile designers and users. A small footprint printed circuit board was designed to minimize the overall size of the unit, compared to “perf-board” prototypes. Several PCB design guidelines were closely followed to reduce electrical interference in digital/analog components and traces. Embedded C code was developed to control the IMU. The unit features a wireless user interface, providing several control options, including an option to download data sampled at 1KHz per sweep of all twelve sensor channels. Preliminary testing reveals good consistency among the high and low-range sensors and acceptably low noise levels.

Accurately determining one’s location has long been a persistent problem in navigation and has reappeared in recent years in the field of mobile computing. The ability to determine a device’s location indoors is needed for both automation and efficient communication in collaborative robotic and sensor networks. Technologies such as indoor GPS transmitters and Cricket have been employed, but have had limited success due to cost, accuracy, and power consumption. The Inertial Solution for Accurately Assessing location Coordinates (ISAAC) was developed as a means of filling this need without requiring infrastructure or expensive components to accurately determine position, inside or outside. ISAAC is based on modified six-degrees-of-freedom (6DOF) dead reckoning algorithms currently being used by Unmanned Aerial Vehicles (UAV). UAVs typically have access to other types of sensors to supplement and/or replace the IMU measurements. ISAAC was implemented using a low-cost MEMS 6DOF IMU in which the onboard firmware was modified to incorporate the dead reckoning calculations and communications necessary to realize ISAAC. ISAAC was implemented as a portable unit which communicated with a host computer through an RS-232 interface. ISAAC did not perform as well as expected; the location coordinates were very inconsistent with device movements and did not produce any useful data. The correct intermediate results of the calculations and subsequent review by a local subject-matter-expert implies that the source of the erroneous results lie with the accuracy and precision of the MEMS IMU. ISAAC presents a foundation for future work where more robust sensors and/or filtering can be used for further examination of inertial-based location systems. / text

Inertial measurement units (IMUs) are used in a wide range of applications to estimate position, velocity, and attitude of vehicles. The high cost of tactical grade IMUs makes the low-cost microelectromechanical systems (MEMS) based IMUs appealing. These types of IMUs are less accurate, so to counteract this effect, multiple and different configurations should be used. The work presented here provides efficient and low cost solutions using different configurations of redundant (multiple) MEMS-IMU swarms, which increase the level of accuracy to potentially the order of that of a tactical IMU. Several configurations are presented and compared through different methods. / text

ITC/USA 2009 Conference Proceedings / The Forty-Fifth Annual International Telemetering Conference and Technical Exhibition / October 26-29, 2009 / Riviera Hotel & Convention Center, Las Vegas, Nevada / The US Army Research Laboratory currently uses a variety of ballistic diagnostic systems for gathering aerodynamic information pertaining to gun launched munitions. Sensors are a vital component of each of these diagnostic systems. Since multiple sensors are commonly used, they are often configured into a sensor suite or inertial measurement unit (IMU). In order to gather information on smaller diameter projectiles, a small diameter IMU was designed using commercial-off-the-shelf (COTS) sensors and components. This IMU was first designed with a 21.6mm diameter and then later reintegrated into a 17.5mm diameter unit. The IMU provides up to ten sensor data channels which can be used to make in-flight projectile motion measurements. These measurements are then used in the determination of the projectile's aerodynamics. It has been successfully flight tested on a variety of projectiles. It has been used in conjunction with an on-board recorder (OBR) to take measurements on 40mm and 25mm projectiles. It has also been used in a telemetry based system on-board a flare stabilized 25mm projectile. This paper covers the design of the IMU and gives examples of various sensor data.

This thesis presents a 6 degree of freedom (DOF) position and orientation tracking solution suitable for pedestrian motion tracking based on 6DOF low cost MEMS inertial measurement units. This thesis was conducted as an extension of the ongoing efforts of the Precision Personnel Location (PPL) project at WPI. Prior to this work most of the PPL research focus has been on Radio Frequency (RF) location estimation. The newly developed inertial based system supports data fusion with the aforementioned RF system in a system currently under development. This work introduces a methodology for the implementation of a position estimation system based upon a Kalman filter structure, constructed from industry standard inertial sensor specifications and analytic noise models. This methodology is important because it allows for both rapid filter construction derived solely from specified values and flexible system definitions. In the course of the project, three different sensors were accommodated using the automatic design tools that were constructed. This thesis will present the mathematical basis of the new inertial tracking system followed by the stages of filter design and implementation, and finally the results of several trials with actual inertial data captures, using both public reference data and inertial captures from a foot mounted sensor that was developed as part of this work.

This paper presents a method for pedestrian activity classification and gait analysis based on the microelectromechanical-systems inertial measurement unit (IMU). The work targets two groups of applications, including the following: 1) human activity classification and 2) joint human activity and gait-phase classification. In the latter case, the gait phase is defined as a substate of a specific gait cycle, i.e., the states of the body between the stance and swing phases. We model the pedestrian motion with a continuous hidden Markov model (HMM) in which the output density functions are assumed to be Gaussian mixture models. For the joint activity and gait-phase classification, motivated by the cyclical nature of the IMU measurements, each individual activity is modeled by a "circular HMM." For both the proposed classification methods, proper feature vectors are extracted from the IMU measurements. In this paper, we report the results of conducted experiments where the IMU was mounted on the humans' chests. This permits the potential application of the current study in camera-aided inertial navigation for positioning and personal assistance for future research works. Five classes of activity, including walking, running, going upstairs, going downstairs, and standing, are considered in the experiments. The performance of the proposed methods is illustrated in various ways, and as an objective measure, the confusion matrix is computed and reported. The achieved relative figure of merits using the collected data validates the reliability of the proposed methods for the desired applications. / <p>QC 20130114</p>

Det finns ett behov av att kunna nyttja ett användarvänligt system för interaktion med kroppsnära sensorer vid undervisning och forskning vid skolan för kemi, bioteknologi och hälsa vid Kungliga Tekniska Högskolan. Ansvariga vid utbildningen har därför gett i uppdrag att utreda om ett specifikt sensorsystem, Movesense, kan utgöra grunden för ett användarvänligt verktyg för att kunna studera biomekaniska rörelser inom utbildning och forskning. En förstudie har genomförts för att undersöka sensorsystemets potential. En systemprototyp har utvecklats för konfiguration av sensorsystemet och hämtning av sensordata. En kvantitativ utvärdering av insamlade data från sensorsystemet och videoanalys har utförts för att fastställa om det är möjligt att utföra rörelseanalyser med hjälp av systemprototypen. Utredningen resulterade i en fungerande systemprototyp, samt slutsatsen att Movesense går att nyttja som verktyg för att studera vissa typer av rörelser. Prototypen har stor utvecklingspotential och sensorsystemet har potentiella möjligheter inom utbildning och forskning. / There is a need to be able to utilize a user-friendly system for interaction with body-worn sensors in teaching and research at the school for chemistry, biotechnology and health at the Royal Institute of Technology. Responsible persons at the program have therefore assigned a Bachelor of Science (BSc) degree project to investigate whether a specific sensor system, Movesense, can serve as a user-friendly tool for studying biomechanical movements within education and research. A preliminary study is carried out to examine the sensor system's potential. A system prototype is developed for configuring the sensor system and retrieving sensor data. A quantitative evaluation of collected data from the sensor system, and video analysis is performed to determine whether it is possible to perform motion analysis using the system prototype. The investigation resulted in a functioning system prototype, and that Movesense can be used as a tool for studying certain types of movements. The prototype has great development potential, and the sensor system has potential opportunities in education and research.

Indoor Positional Navigation (IPN) systems can be used to track the position of tools in factories which is crucial for quality assurance in many manufacturing industries. Inertial navigation is rarely used on its own because of the noisy Inertial Measurement Unit (IMU) sensors which contribute to large drift. Current IPN systems usually involve the installation and calibration of cameras or antennas, so achieving sufficient accuracy with inertial navigation based IPN would be very desirable. This project aims to evaluate an inertial navigation algorithm, based on Zero Velocity Update (ZUPT), for bolt level positioning by repeatability tests using an industrial robot. The ZUPT algorithm, developed at Atlas Copco, manages to effectively reduce drift and achieve moderate accuracy in position for simpler movements. The gravity tracking Kalman filter dictates the systematic errors in position that grow large with increased degree and dimension of rotation. When keeping rotations within 45◦ for a linear movement the absolute error in position is under 10%. Frequent stops are important when moving in a more complex trajectory to be able to negate drift, consequently detecting the start and stop of motion is crucial. The results show that increased frequency will improve accuracy. It is shown that averaging IMU samples before calculations can increase both truthfulness and precision by 10−25%, if sampling the IMU faster than the calculations. The ZUPT approach of inertial navigation will never yield positional results in real time, and the evaluated algorithm only performs well within certain limitations, mainly frequent stops and simple movements. Despite these limitations there is potential in using the algorithm for quality assurance purposes in hand held industrial fasteners. / Kvalitetssäkring är en central fråga för många tillverkningsindustrier, så som flygplans- och bilindustrin, där det är avgörande att varje förband har dragits åt på rätt sätt för att garantera säkerheten i produkten. Moderna fabriker har centrala styrsystem som kommunicerar med maskiner och verktyg, och ifall något blir fel är det vanligt att fabrikslinan stannar vilket blir kostsamt. Inomhuspositionering (IPS) av hög noggrannhet kan spåra vilken åtdragning som blivit fel, vilket dokumenteras och åtgärdas om möjligt senare, utan att stanna fabrikslinan. Dagens noggranna IPS system för kvalitetssäkring kräver installation och kalibrering av kameror och/eller antenner. Tröghetsnavigering kräver i grunden bara billiga sensorer installerade på verktyget men metoden är mycket opålitlig på grund av sensorernas opålitlighet och brus. I detta projekt har en metod för tröghetsnavigering, användandes Zero Velocity Update (ZUPT), evaluerats för kvalitetssäkring av handhållna verktyg genom repetabilitetstester. Tröghetsnavigeringsalgoritmen som tidigare utvecklats på Atlas Copco lyckas på effektivt sätt reducera drift och uppnår rimlig noggranhet för enklare rörelser. För linjära rörelser med rotationer under 45◦ så erhålls ett absolut positionsfel inom 10%. För att fungera väl även för mer komplexa rörelser krävs frekventa stop, och noggrann rörelsedetektion är central. Denna ZUPT-metod kommer aldrig att kunna generera position i realtid och algoritmen presterar väl endast inom vissa begränsningar. Trots detta så finns god potential för metoden inom kvalitetssäkring för handhållna industriverktyg.

International Telemetering Conference Proceedings / October 25-28, 1999 / Riviera Hotel and Convention Center, Las Vegas, Nevada / Obtaining a projectile’s free-flight motion profile and its aerodynamic coefficients is typically accomplished at indoor test ranges using photographic techniques synchronized to timing stations. Since these ranges are relatively short, many discrete tests are necessary to compile a complete understanding of the projectile’s behavior. When Time Space Position Information (TSPI) is requested over long-range flights, it has been gathered with expensive video, laser, and radar trackers. These can be inaccurate at times and are limited to locations where the range equipment is able to track the projectile’s entire flight. With the ever-increasing sophistication of ordnance, such as smart and competent munitions that have multi-stage thrusting and maneuvering capability, it is becoming increasingly difficult to make the necessary measurements using current measurement techniques. Microelectromechanical Systems (MEMS) sensors and other electro-optical and magnetic sensors referenced to the sun and earth allow the projectile’s angular rates (spin, pitch, and yaw) and accelerations (axial and radial) to be measured throughout the flight. These sensors have been packaged into miniaturized telemetry instrumentation systems and placed within empty voids of the munition or in place of the fuze or warhead section. By combining this sensor data with a 6-DOF trajectory code, many of the projectiles aerodynamic coefficients including drag, static moment, and damping moment over a large Mach Number range and over multiple flight paths have been obtained. These techniques decrease the number of test shots required, reduce the complexity of the test setup, and reduce the test costs. Test data from instrumented tank, artillery, and rocket flight tests are presented in this report to show the current capability of making inflight measurements using telemetry-based techniques.

O mecanismo Plataforma de Stewart é um manipulador do tipo paralelo, com seis graus de liberdade, boa relação peso/carga e alta rigidez. Tais características conferem a este tipo de manipulador propriedades superiores de precisão em relação aos manipuladores seriais. Neste trabalho, o controle de um Manipulador Plataforma de Stewart (MPS) acionado por atuadores hidráulicos é estudado com o objetivo de compensação de movimentos para viabilização de transferência de cargas e pessoas em ambiente naval.Visando ao desenvolvimento de um protótipo experimental, o manipulador é estudado considerando a situação em que se encontra sobreposto a um segundo MPS que tem por objetivo simular o movimento da maré, sendo ambos MPS considerados desacoplados dinamicamente. Neste contexto, o estudo envolve a análise cinemática e dinâmica do manipulador incluindo, também, a dinâmica dos cilindros hidráulicos. Além disso, são estudadas unidades de medição inercial (IMU) utilizando-as como instrumento para medição do movimento da base a ser compensado. O projeto do controlador do sistema de atenuação de movimento faz uso da técnica de Torque Computado (TC). A análise de estabilidade, feita separadamente para o sistema mecânico e hidráulico, baseou-se da teoria de Lyapunov. Simulações realizadas considerando trajetórias similares às do movimento de um navio são utilizadas. Para compensação do movimento são utilizados, também, sinais provenientes de uma IMU. Por meio de simulação, comprova-se que o sistema proposto é capaz de compensar adequadamente os movimentos da base estudados. / The Stewart platform mechanism is a parallel manipulator with six degrees of freedom, high load/weight ratio and high stifness. These properties give them a better accuracy when compared to serial manipulators. This work focuses on study of electrohydraucally Stewart Platform Manipulators (MPS) to enable compensation of vessels motions for load and personell transfer in sea. Aimed at developing an experimental prototype, a second MPS is placed underneath the rst MPS to simulate vessels motions and so both manipulators are considered dynamically decoupled. In this sense, the kinematics and dynamics of this manipulator are presented, as well as a mathematical model of the hydraulic actuator. Furthermore, special attention is given to the study of inertial measurement units (IMU) which is used as an instrument for measuring the motion to be compensated. Controller design for the compensation system is developed considering compute torque theory which consider the system separated in two: mechanical and hydraulic. The Lyapunov criteria is used to guarantee closed loop stability for each subsystem. Simulations are performed considering similar vessel motions. Signals provided from a comercial IMU are used for motion compensation. The control compensation performance is veri ed by means of computer simulations.