http://ieeexplore.ieee.org/iel5/5/31047/01444179.pdf

Fundamentals of acoustics

Real-time tracking of human body motion is an important technology in synthetic environments, robotics, and other human-computer interaction applications. This paper presents an extended Kalman filter designed for real-time estimation of the orientation of human limb segments. The filter processes data from small inertial/magnetic sensor modules containing triaxial angular rate sensors, accelerometers, and magnetometers. The filter represents rotation using quaternions rather than Euler angles or axis/angle pairs. Preprocessing of the acceleration and magnetometer measurements using the Quest algorithm produces a computed quaternion input for the filter. This preprocessing reduces the dimension of the state vector and makes the measurement equations linear. Real-time implementation and testing results of the quaternion-based Kalman filter are presented. Experimental results validate the filter design, and show the feasibility of using inertial/magnetic sensor modules for real-time human body motion tracking

/pdf/design-implementation-and-experimental-results-of-a-1rdc3xrkch.pdf

Design, Implementation, and Experimental Results of a Quaternion-Based Kalman Filter for Human Body Motion Tracking

Improving the performance of modular, low-cost autonomous underwater vehicles (AUVs) in such applications as long-range oceanographic survey, autonomous docking, and shallow-water mine countermeasures requires improving the vehicles' maneuvering precision and battery life. These goals can be achieved through the improvement of the vehicle control system. A vehicle dynamics model based on a combination of theory and empirical data would provide an efficient platform for vehicle control system development, and an alternative to the typical trial-and-error method of vehicle control system field tuning. As there exists no standard procedure for vehicle modeling in industry, the simulation of each vehicle system represents a new challenge. Developed by von Alt and associates at the Woods Hole Oceanographic Institute, the REMUS AUV is a small, low-cost platform serving in a range of oceanographic applications. This thesis describes the development and verification of a six degree of freedom, non-linear simulation model for the REMUS vehicle, the first such model for this platform. In this model, the external forces and moments resulting from hydrostatics, hydrodynamic lift and drag, added mass, and the control inputs of the vehicle propeller and fins are all defined in terms of vehicle coefficients. This thesis describes the derivation of these coefficients in detail. The equations determining the coefficients, as well as those describing the vehicle rigid-body dynamics, are left in non-linear form to better simulate the inherently non-linear behavior of the vehicle. Simulation of the vehicle motion is achieved through numeric integration of the equations of motion. The simulator output is then checked against vehicle dynamics data collected in experiments performed at sea. The simulator is shown to accurately model the motion of the vehicle. Thesis Supervisor: Jerome Milgram Title: Professor of Ocean Engineering, MIT Thesis Supervisor: Kamal Youcef-Toumi Title: Professor of Mechanical Engineering, MIT Thesis Supervisor: Christopher von Alt Title: Principal Engineer, WHOI Candide had been wounded by some splinters of stone; he was stretched out in the street and covered with debris. He said to Pangloss: "Alas, get me a little wine and oil, I am dying." "This earthquake is not a new thing," replied Pangloss. "The town of Lima suffered the same shocks in America last year; same causes, same effects; there is certainly a vein of sulfur underground from Lima to Lisbon." "Nothing is more probable," said Candide, "but for the love of God, a little oil and wine." "What do you mean, probable?" replied the philosopher. "I maintain that the matter is proved." Candide lost consciousness.

/pdf/verification-of-a-six-degree-of-freedom-simulation-model-for-4n98272on0.pdf

Verification of a six-degree of freedom simulation model for the REMUS autonomous underwater vehicle

A human body motion tracking system based on use of the MARG (Magnetic, Angular Rate, and Gravity) sensors has been under development at the Naval Postgraduate School and Miami University. The design of a quaternion-based Kalman filter for processing the MARG sensor data was described in [1]. This paper presents the real-time implementation and testing results of the quaternion-based Kalman filter. Experimental results validate the Kalman filter design, and show the feasibility of the MARG sensors for real-time human body motion tracking.

/pdf/implementation-and-experimental-results-of-a-quaternion-20j231gm54.pdf

Implementation and Experimental Results of a Quaternion-Based Kalman Filter for Human Body Motion Tracking

Adaptive tuning of a Kalman filter via fuzzy logic for an intelligent AUV navigation system

This paper presents the design and development of an enhanced inertial navigation system that is to be integrated into the Morpheus autonomous underwater vehicle at Florida Atlantic University. The inertial measurement unit is based on the off-the-shelf Honeywell HG1700-AG25 3-axis ring-laser gyros and three-axis accelerometers and is aided with ground speed measurements obtained using an RDI Doppler-velocity-log sonar. An extended Kalman filter has been developed, which fuses together asynchronously the inertial and Doppler data, as well as the differential Global Positioning System positional fixes whenever they are available. A complementary filter was implemented to provide a much smoother and stable attitude estimate. Thus far, preliminary study has been made on characterizing the inertial navigation system-based navigation system performance, and the corresponding results and analyzes are provided.

Enhancement of the inertial navigation system for the Morpheus autonomous underwater vehicles

Autonomous underwater vehicles (AUVs) are typically used to "actively" probe the ocean, using sensors that are mounted on a vehicle that moves through the water column. A more challenging task is to use an AUV to position a bottom-mounted stationary platform, such as a passive sonar that requires a large aperture. This paper describes the development of a passive sonar, which was mounted as a payload to the Ocean Explorer II, AUV developed at the Florida Atlantic University. The payload was designed so that the AUV could land on the seafloor and deploy the sonar. The passive sonar developed for this system can be used to measure and localize broadband sources that generate ambient noise in the coastal region. The sonar uses a sparse volume array of only six elements and a 2 m maximum dimension. With this array, it is possible to generate three-dimensional images consisting of thousands of independent pixels for any look direction or chosen image plane. This paper describes the ambient noise sonar and the variable buoyancy system used in deploying the array, and then presents some typical results obtained using the sonar.

A passive sonar system based on an autonomous underwater vehicle

This paper describes a controlled self-motion study recently carried out using a small autonomous underwater vehicle (AUV) in a controlled environment in which regular and random waves can be generated accurately for various frequencies and heights. In this study, the AUV was one of the Florida Atlantic University's Ocean Explorer series vehicles, and the controlled environment was chosen to be the Maneuvering And Sea-Keeping (MASK) facilities located at the David Taylor Model Basin. During the entire study, 29 sets of experimental motion and wave data were collected under various wave frequencies and heights, vehicle alignment, and operating depths. Due to the wave tank constraint, the vehicle speed was restricted to be less than 1.5 m/s and the wave frequency higher than 0.3 Hz without significantly affecting the self-motion analysis. Time history and power spectral density results suggest that the roll-induced pitching response was considerably larger for the wave frequencies tested, as compared to the pitch-induced rolling response. Standard deviation results reveal that the existing OEX is capable of producing approximately 3/spl deg/ (peak-to-peak) pitch, 0.7/spl deg/ (peak-to-peak) roll, and 0.6/spl deg/ (peak-to-peak) yaw at 2-m depth in the head-sea condition when the encountering wave frequency is close to 0.4 Hz. However, at 1.5-m vehicle depth, significant surges were observed in pitching and rolling motion, suggesting that the OEX is currently unsuitable to maintain accurate depth-following within this range at sea-state 2 or higher. It is hoped that the results presented can provide better insights into how a small AUV with a nonideal body shape reacts to waves of different sea states, and how vehicle self-motion can be streamlined by choosing proper vehicle speed, heading, and depth, given that the wave characteristics are available.

S.M. Smith

Papers

Enhancement of the inertial navigation system for the Morpheus autonomous underwater vehicles

A passive sonar system based on an autonomous underwater vehicle

An experimental self-motion study of the Ocean Explorer AUV in controlled sea states