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Gauge Repeatability And Reproducibility Study On A Hemi-Shell With A Brown & Sharpe® Coordinate Measuring Machine (U), Lucas Valdez Aug 2011

Gauge Repeatability And Reproducibility Study On A Hemi-Shell With A Brown & Sharpe® Coordinate Measuring Machine (U), Lucas Valdez

Mechanical Engineering Student Publications

In engineering at LANL, everything relies on the quality of a product or process. Today dimensional inspection is a necessity to ensure customer specifications are met to the highest standard. Currently LANL’s main processes for dimensional inspection on hemi-shells are conducted on uniquely designed machines - Sheffield or Shell Measuring Machine (SMM). These specialized rotary contour machines were built to measure only the wall thickness, inner and outer contours of a hemi-shell. These machines are heavily dependent on the inspector and typically have very few personnel trained to use them. With no manufacturer support and age leading to production down ...


Packaging Strategy For High Voltage And High Shock Environments, Kevin Austin Aug 2011

Packaging Strategy For High Voltage And High Shock Environments, Kevin Austin

Mechanical Engineering Student Publications

The historical design approach for ensuring survivability in devices that operate at high voltages which would arc in air or that must survive substantial shock loadings employs an encapsulant whose dielectric strength prevents electrical breakdown and whose modulus prevents gross movement of the embedded components. While mostly successful, this approach presents some significant design challenges: (1) the high thermal expansion of the epoxy leads to large stresses during thermal cycles, (2) degassing of the epoxy before cure and careful encapsulation are essential to eliminate voids that could initiate dielectric breakdown, (3) the internal components are embedded deep within an impenetrable ...


Extended Kalman Filter Implementation For The Khepera Ii Mobile Robot, Thomas J. Otahal, Herbert G. Tanner Jan 2009

Extended Kalman Filter Implementation For The Khepera Ii Mobile Robot, Thomas J. Otahal, Herbert G. Tanner

Mechanical Engineering Faculty Publications

The accurate estimation of robot position and orientation in real-time is one of the fundamental challenges in mobile robotics. The Extended Kalman Filter is a nonlinear real-time recursive time domain filter that combines available sensor data to produce an accurate estimate of state, and has been successfully applied to the localization problem in mobile robotics and aircraft navigation. This report describes an Extended Kalman Filter implementa- tion for the Khepera II mobile robotics platform that seeks to produce accurate localization estimates in real-time using wheel odometry data, IR sensor range data, and compass heading data.


Information Surfing For Model-Driven Radiation Mapping, Andres Cortez, Herbert G. Tanner Jun 2007

Information Surfing For Model-Driven Radiation Mapping, Andres Cortez, Herbert G. Tanner

Mechanical Engineering Faculty Publications

In this report we develop a control scheme to coordinate a group of mobile sensors for radiation mapping of a given planar polygon region. The control algorithm is based on the concept of information surfing, where navigation is done by means of following information gradients, taking into account sensing performance as well as inter-robot communication range limitations. The control scheme provably steers mobile sensors to locations at which they maximize the information content of their measurement data, and the asymptotic properties of our information metric with respect to time ensures that no local information metric extremum traps the sensors indefinitely ...


Task-Driven Multi-Formation Control For Coordinated Uav/Ugv Isr Missions, Herbert G. Tanner Oct 2006

Task-Driven Multi-Formation Control For Coordinated Uav/Ugv Isr Missions, Herbert G. Tanner

Mechanical Engineering Faculty Publications

The report describes the development of a theoretical framework for coordination and control of combined teams of UAVs and UGVs for coordinated ISR missions. We consider the mission as a composition of an ordered sequence of subtasks, each to be performed by a different team. We design continuous cooperative controllers that enable each team to perform a given subtask and we develop a discrete strategy for interleaving the action of teams on different subtasks. The overall multi-agent coordination architecture is captured by a hybrid automaton, stability is studied using Lyapunov tools, and performance is evaluated through numerical simulations.


Thermodynamically Consistent Relations Involving Plasticity, Internal Energy And Thermal Effects, Howard Schreyer, Paul Maudlin Mar 2006

Thermodynamically Consistent Relations Involving Plasticity, Internal Energy And Thermal Effects, Howard Schreyer, Paul Maudlin

Mechanical Engineering Faculty Publications

Experimental data associated with plastic deformations indicate that the temperature is less than that predicted from dissipation based on plastic work. To obtain reasonable correlation between theoretical and experimental results, the plastic work is often multiplied by a constant β. This paper provides an alternative thermodynamic framework in which it is proposed that there is an additional internal energy associated with dislocation pile-up or increase in dislocation density. The form of this internal energy follows from experimental data that relates flow stress to dislocation density and to equivalent plastic strain. The result is that β is not a constant but ...


Increasing The Accuracy Of Cooperative Localization By Controlling The Sensor Graph, Deepti Kumar, Herbert G. Tanner Mar 2006

Increasing The Accuracy Of Cooperative Localization By Controlling The Sensor Graph, Deepti Kumar, Herbert G. Tanner

Mechanical Engineering Faculty Publications

We characterize the accuracy of a cooperative localization algorithm based on Kalman Filtering, as expressed by the trace of the covariance matrix, in terms of the algebraic graph theoretic properties of the sensing graph. In particular, we discover a weighted Laplacian in the expression that yields the constant, steady state value of the covariance matrix. We show how one can reduce the localization uncertainty by manipulating the eigenvalues of the weighted Laplacian. We thus provide insight to recent optimization results which indicate that increased connectivity implies higher accuracy and we offer an analysis method that could lead to more efficient ...


Almost Global Asymptotic Formation Stabilization Using Navigation Functions, Amit Kumar, Herbert G. Tanner Oct 2004

Almost Global Asymptotic Formation Stabilization Using Navigation Functions, Amit Kumar, Herbert G. Tanner

Mechanical Engineering Faculty Publications

We present a navigation function through which a group of mobile agents can be coordinated to achieve a particular formation, both in terms of shape and orientation, while avoiding collisions between themselves and with obstacles in the environment. Convergence is global and complete, subject to the constraints of the navigation function methodology. Algebraic graph theoretic properties associated with the interconnection graph are shown to affect the shape of the navigation function. The approach is centralized but the potential function is constructed in a way that facilitates complete decentralization. The strategy presented will also serve as a point of reference and ...