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

Fall accidents are one of the most serious problems leading to unintentional injuries and fatalities among older adults. However, it is difficult to assess individuals' fall risk and to determine who are at risk of falls and in need of fall interventions. Therefore, this study was motivated by a need to provide a cogent fall risk assessment strategy that may be conducive to various wireless platforms. It aimed at developing a fall risk assessment method for evaluating individuals' fall risk by providing diagnostic modalities associated with gait. In this study, a "determinants of gait" model was adopted to analyze gait characteristics and associate them with fall risk. As a proof of concept, this study concentrated on slip-induced falls and the slip initiation risks. Two important parameters of determinants of gait, i.e. the pelvic rotation and the knee flexion, were found to be associated with slip initiation severity. This relationship appeared to be capable of differentiating fallers and non-fallers within older adults, as well as differentiating normal walking conditions and constrained walking conditions. Furthermore, this study also leveraged portable wireless sensor techniques and investigated if miniature inertial measurement units could effectively measure the important parameters of determinants of gait, and therefore assess slip and fall risk. Results in this study suggested that pelvic rotation and knee flexion measured by the inertial measurement units can be used as a substitution of the traditional motion capture system and can assess slip and fall risk with fairly good accuracy. As a summary, findings of this study filled the knowledge gap about how critical gait characteristics can influence slip and fall risk, and demonstrated a new solution to assess slip and fall risk with low cost and high efficiency. / Ph. D.

Wearable computers and e-textiles are increasingly prevalent in today's society. Motion capture is one of many potential applications for on-body electronic systems. Self-contained motion capture applications require information from sensors distributed throughout the body on a "smart" garment. Therefore, this thesis presents the design of a flexible hardware platform for e-textile motion capture applications. This thesis also presents software for one such application, namely, tracking the pose or relative position of body limbs. The accuracy of this solution is compared to an industrial optical motion capture system. The combined hardware and software design are successful at collecting and processing motion capture data in the context of an e-textile jumpsuit. / Master of Science

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.

La navigation par système inertiel strapdown est aujourd’hui la plus répandue. L’architecture est bien connue et a été très largement améliorée au cours des dernières décennies. Néanmoins, le principe fondamental n’a subi de bouleversement et reste constitué d’une triplette d’accéléromètres et de gyromètres permettant de revenir aux informations d’attitude et de cap.La précision de l’estimation de position repose principalement sur la gamme de performance des capteurs utilisés. En particulier, des applications telles que des lanceurs spatiaux requièrent une très haute précision et des capteurs d’une technologie éprouvée sont utilisés. L’arrivée sur le marché de capteurs inertiels MEMS de haute précision ouvre une alternative à coût réduits couplée à une réduction de masse, volume et de consommation. Les moyens de production des MEMS ainsi qu’une meilleure connaissance des propriétés des matériaux ont permis l’arrivée d’accéléromètres MEMS pouvant rivaliser avec les technologies éprouvées de gamme tactique. Toutefois, les gyromètres de technologie MEMS existantes restent dans une gamme de performance de type industrielle.La présente étude vise à analyser la possibilité d’utiliser des accéléromètres de haute précision pour améliorer les performances gyrométriques, dans l’objectif de réaliser une solution tout MEMS d’unité de mesure inertielle. Une brève introduction sur les techniques de filtrage de Kalman pour la fusion de données est présentée, ainsi que son implémentation pour notre étude. L’analyse théorique se poursuit avec une présentation des résultats expérimentaux.L’étude conclut que l’utilisation d’une paire d’accéléromètres de haute performance et d’un gyroscope de type consommateur permet d’atteindre les performances d’un gyromètre tactique. Les contraintes de définition et de mesure pour l’implémentation du système sont présentées en détail.Cette étude est menée pour la mesure angulaire autour d’un axe unique de rotation, un complément d’étude est nécessaire à l’extrapolation de cette approche pour une mesure générique en 3D. / Strapdown inertial navigation units are the most popular systems used for navigation. The system architecture is well established and has been extensively improved over the past decades. However, the core idea remains same where a triad of accelerometers and gyroscopes provide the attitude and heading information.The accuracy of the position estimate depends on the performance grade of the sensors employed. For applications like space launchers requiring very high accuracy, high-grade devices using traditional technologies are used. The advent of accurate MEMS based sensors offer an exciting low-cost alternative with expected reduction in size and power consumption. MEMS fabrication technology, assisted by improved understanding of material properties have led to accelerometers that can compete with traditional devices for tactical applications. However, the MEMS based solutions currently available for gyroscopes can replace only industrial grade applications.This study attempts to investigate if the currently available high-grade accelerometers can be used to improve the gyroscope performance, towards the final goal of a complete MEMS based solution for inertial navigation units. The study begins with a literature review of current status of technology. A brief explanation of linear Kalman filtering technique for data fusion is presented, along with its implementation concerning this work. The theoretical discussion is then followed by presentation of experimental results.The study found that using a pair of high-grade accelerometers, a consumer grade gyroscope can have its performance upgraded for tactical applications. The design and sensing constraints for realizing this system are discussed in detail.Since this research work primarily concerns with angular rate estimation around a single axis of rotation, further research is recommended for extrapolating this approach for a more general 3-D sensing case.

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>

Thesis(M.S.)--Auburn University, 2006. / Abstract. Vita. Includes bibliographic references (p.115-120).