Miller P.A.,Mine Safety Appliances |
Farrell J.A.,University of California at Riverside |
Zhao Y.,Digital Forest |
Djapic V.,Undersea Research Center
IEEE Journal of Oceanic Engineering | Year: 2010
This paper considers the vehicle navigation problem for an autonomous underwater vehicle (AUV) with six degrees of freedom. We approach this problem using an error state formulation of the Kalman filter. Integration of the vehicle's high-rate inertial measurement unit's (IMU's) accelerometers and gyros allow time propagation while other sensors provide measurement corrections. The low-rate aiding sensors include a Doppler velocity log (DVL), an acoustic long baseline (LBL) system that provides round-trip travel times from known locations, a pressure sensor for aiding depth, and an attitude sensor. Measurements correct the filter independently as they arrive, and as such, the filter is not dependent on the arrival of any particular measurement. We propose novel tightly coupled techniques for the incorporation of the LBL and DVL measurements. In particular, the LBL correction properly accounts for the error state throughout the measurement cycle via the state transition matrix. Alternate tightly coupled approaches ignore the error state, utilizing only the navigation state to account for the physical latencies in the measurement cycle. These approaches account for neither the uncertainty of vehicle trajectory between interrogation and reply, nor the error state at interrogation. The navigation system also estimates critical sensor calibration parameters to improve performance. The result is a robust navigation system. Simulation and experimental results are provided. © 2005 IEEE.
Dong W.,University of America |
Zhao Y.,Digital Forest |
Chen Y.,University of California at Riverside |
Farrell J.A.,University of California at Riverside
IEEE Transactions on Neural Networks and Learning Systems | Year: 2012
This paper considers tracking control for single-input, single-output nonaffine dynamic systems. A performance-dependent self-organizing approximation-based approach is proposed. The designer specifies a positive tracking error criterion. The self-organizing approximation-based controller then monitors the tracking performance and adds basis elements only as needed to achieve the tracking specification. Even though the system is not affine, the approach is defined such that the approximated function is independent of the control variable u. Stability is proved and the self-organization is derived in a Lyapunov-based methodology. To illustrate certain novel aspects of the proposed controller, a numerical example is included. © 2012 IEEE.
Tan X.,Michigan State University |
Xi W.,Digital Forest |
Baras J.S.,University of Maryland University College
Automatica | Year: 2010
In this paper we present analysis of a discrete-time, decentralized, stochastic coordination algorithm for a group of mobile nodes, called an autonomous swarm, on a finite spatial lattice. All nodes take their moves by sampling in parallel their locally perceived Gibbs distributions corresponding to a pairwise, nearest-neighbor potential. The algorithm has no explicit requirements on the connectedness of the underlying information graph, which varies with the swarm configuration. It is established that, with an appropriate annealing schedule, the algorithm results in swarm configurations converging to the (global) minimizers of a modified potential energy function. The extent of discrepancy between the modified and original potential energy functions is determined by the maximum node travel between time steps, and when such distance is small, the ultimate swarm configurations are close to the global minimizers of the original potential energy. Simulation results are further presented to illustrate the capability of the sampling algorithm in approximate global optimization for swarms. © 2010 Elsevier Ltd. All rights reserved.
Li Y.,University of Minnesota |
Srinivasan B.,University of Minnesota |
Jing Y.,University of Minnesota |
Yao X.,University of Minnesota |
And 4 more authors.
Journal of the American Chemical Society | Year: 2010
A novel giant magnetoresistive sensor and uniform high-magnetic-moment FeCo nanoparticles (12.8 nm)-based detecting platform with minimized detecting distance was developed for rapid biomolecule quantification from body fluids. Such a system demonstrates specific, accurate, and quick detection and quantification of interleukin-6, a low-abundance protein and a potential cancer biomarker, directly in 4 L of unprocessed human sera. This platform is expected to facilitate the identification and validation of disease biomarkers. It may eventually lead to a low-cost personal medical device for chronic disease early detection, diagnosis, and prognosis. © 2010 American Chemical Society.
Dhanda A.,Stanford University |
Dhanda A.,Digital Forest |
Franklin G.F.,Stanford University
IEEE Transactions on Automatic Control | Year: 2010
Design of controls to move a flexible body such as a robot arm while minimizing unwanted vibrations has been described in many papers and presented in many forms. For the vibration reduction issue alone, it is shown that almost all the proposed designs can be formulated as optimal controls of either the fixed final time or the minimum time type. Furthermore, it is shown that under reasonable assumptions the two types have the same solution and are thus equivalent. Continuous time, tapped-delay-line input shaping filters, and discrete controls are considered. It is shown that the discrete equivalent of the general vibration reduction problem is a convex problem for the fixed final time case and quasi-convex for the free final time problem. The two formulations are compared in terms of computation complexity as well as practical implementation issues. © 2010 IEEE.
Yong Y.K.,University of Newcastle |
Liu K.,Digital Forest |
Moheimani S.O.R.,University of Newcastle
IEEE Transactions on Control Systems Technology | Year: 2010
A compliant XY nanopositioner is presented in this brief. The device is designed to have a very low cross-coupling between the X- and Y-axis. Despite this, during high-speed raster scans, the cross-coupling effect can not be ignored. In this brief, a H∞ controller is designed and implemented to minimize the X-to- Y cross-coupling of the nanoscale positioning stage, particularly at its mechanical resonance frequencies. The controller is augmented with integral action to achieve accurate tracking, as well as sufficient damping. Raster scan results over an area of 10 μm × 10 μm with small positioning errors are demonstrated. High-speed accurate raster scans of up to 100 Hz, with nanoscale resolution are also illustrated. © 2010 IEEE.
Malone C.A.,Digital Forest |
Sauer N.J.,Michigan State University |
Fenton T.W.,Michigan State University
Journal of Forensic Sciences | Year: 2011
Past studies and pediatric bone physiology indicate that younger individuals may heal at a faster rate. Additionally, in adults upper limb fractures heal faster than lower limb fractures; this trend is expected for pediatric fractures. This study aims to evaluate and compare rates of fracture repair in children based on age and skeletal element. Six stages are used to describe the bone repair process in 294 radiographs of tibial and radial fractures from 107 infants and young children. Healing rates are examined using ANOVA and Welch's t-test with a 95% confidence interval. Results indicate that younger individuals spend less time at stage 1, suggesting a delay in the start of healing. Furthermore, forearm fractures heal faster than leg fractures at stages 2 and 3, suggesting a role in the osseous reaction of bone healing. The healing schedule presented may allow the timing of injuries to be estimated from radiographs. © 2011 American Academy of Forensic Sciences.
Malone C.A.,Digital Forest |
Salyards M.J.,Digital Forest |
Hein M.,U.S. Air force
Journal of Forensic Sciences | Year: 2015
Skin detail of the hand is used in photographic comparisons, yet its reliability has not been evaluated. This study examines a count-based method for documenting skin features. In Part I, 14 individuals counted skin features on 40 color images of the hand, three of which were repeated. An average correlation value of 0.557 was obtained for interobserver assessment; values ranged from 0.545 to 0.832 for intra-observer assessment. The variation in correlation values for hands suggests that there are certain distinguishing characteristics that increase reliability. In Part II, 17 examiners assessed 20 nonrepeated grayscale images of hands by circling skin features. An average correlation value of 0.674 was obtained, but visual assessment of examiner markings suggested some examiners grouped features whereas others viewed them individually. The results suggest further research is warranted, some hands may be more suitable for comparisons, and a standardized method for examining skin features is needed. © 2015 American Academy of Forensic Sciences.
PubMed | 24th Air Force and Digital Forest
Type: Journal Article | Journal: Journal of forensic sciences | Year: 2016
Skin detail of the hand is used in photographic comparisons, yet its reliability has not been evaluated. This study examines a count-based method for documenting skin features. In Part I, 14 individuals counted skin features on 40 color images of the hand, three of which were repeated. An average correlation value of 0.557 was obtained for interobserver assessment; values ranged from 0.545 to 0.832 for intra-observer assessment. The variation in correlation values for hands suggests that there are certain distinguishing characteristics that increase reliability. In Part II, 17 examiners assessed 20 nonrepeated grayscale images of hands by circling skin features. An average correlation value of 0.674 was obtained, but visual assessment of examiner markings suggested some examiners grouped features whereas others viewed them individually. The results suggest further research is warranted, some hands may be more suitable for comparisons, and a standardized method for examining skin features is needed.