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- UAV (4)
- Unmanned aircraft (4)
- Compliant mechanisms (3)
- Bearings (2)
- Contact interactions (2)
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- Microstructure (2)
- Revolute joints (2)
- Springs (2)
- Autopilot (1)
- Bistable mechanisms (1)
- Decentralized control (1)
- Dual-stage (1)
- Electron micrographs (1)
- Fabrication (1)
- Fire monitoring (1)
- Grain boundaries (1)
- Grain boundary structure (1)
- Input constraint (1)
- Mechanical properties-elastic behavior (1)
- Mesostructure (1)
- Micromachining (1)
- Microstructure-texture (1)
- Misorientation (1)
- Mobile robot (1)
- Nanopositioner (1)
- Nonlinear tracking control (1)
- OIM (1)
- Obstacle avoidance (1)
- On-chip actuation (1)
- Orientation imaging microscopy (OIM) (1)
Articles 1 - 13 of 13
Full-Text Articles in Engineering
Fully Compliant Tensural Bistable Micro-Mechanisms (Ftbm), D. L. Wilcox, Larry L. Howell
Fully Compliant Tensural Bistable Micro-Mechanisms (Ftbm), D. L. Wilcox, Larry L. Howell
Faculty Publications
A new class of bistable mechanisms, the fully compliant tensural bistable micromechanism (FTBM) class, is introduced. The class consists of linear bistable micromechanisms that undergo tension loads, in addition to the bending loads present, through their range of motion. Proof-of-concept designs fabricated in two different microelectromechanical systems (MEMS) surface micromachining processes were demonstrated. Three sets of refined designs within the FTBM class were designed using optimization methods linked with nonlinear finite element analysis (FEA), then fabricated and tested. Measured force and displacement performance are compared to values obtained by FEA. On-chip actuation of the bistable mechanisms was achieved using thermomechanical …
Recovery Of The Grain Boundary Character Distribution Through Oblique Double-Sectioning, Brent L. Adams, David T. Fullwood, E. R. Homer
Recovery Of The Grain Boundary Character Distribution Through Oblique Double-Sectioning, Brent L. Adams, David T. Fullwood, E. R. Homer
Faculty Publications
This work was supported primarily by the MRSEC program of the National Science Foundation under DMR-0079996. A method for the retrieval of the complete grain boundary character distribution by oblique double-sectioning is proposed. The method, which is similar to the recovery of the orientation distribution from sets of incomplete pole-figures, is efficient and provides many advantages as compared to calibrated serial sectioning. As compared to standard stereological approaches, the new methodology retains the advantage of direct measurement of the grain boundary inclination parameters. Solutions to the fundamental equation of oblique double-sectioning are provided in the Fourier space, and some specifics …
A Compliant Contact-Aided Revolute Joint, Jessie R. Cannon, Larry L. Howell
A Compliant Contact-Aided Revolute Joint, Jessie R. Cannon, Larry L. Howell
Faculty Publications
This paper presents the compliant contact-aided revolute (CCAR) joint, a planar mechanism capable of performing the functions of a bearing and a spring. The pseudo-rigid-body model is used to predict the behavior of the CCAR joint, and this model is validated through the use of finite element analysis and prototype testing. The CCAR joint is shown to have high maximum rotation and lateral stiffness. A case study is presented, and manufacturing considerations are discussed for the macro, meso, and micro scales.
A Compliant Contact-Aided Revolute Joint, Jessie R. Cannon, Larry L. Howell
A Compliant Contact-Aided Revolute Joint, Jessie R. Cannon, Larry L. Howell
Faculty Publications
This paper presents the compliant contact-aided revolute (CCAR) joint, a planar mechanism capable of performing the functions of a bearing and a spring. The pseudo-rigid-body model is used to predict the behavior of the CCAR joint, and this model is validated through the use of finite element analysis and prototype testing. The CCAR joint is shown to have high maximum rotation and lateral stiffness. A case study is presented, and manufacturing considerations are discussed for the macro, meso, and micro scales.
Static And Dynamic Obstacle Avoidance For Miniature Air Vehicles, Jeffery Brian Saunders, Brandon Call, Andrew Curtis, Randal W. Beard, Timothy W. Mclain
Static And Dynamic Obstacle Avoidance For Miniature Air Vehicles, Jeffery Brian Saunders, Brandon Call, Andrew Curtis, Randal W. Beard, Timothy W. Mclain
Faculty Publications
Small unmanned air vehicles are limited in sensor weight and power such that detection and avoidance of unknown obstacles during flight is difficult. This paper presents a low power low weight method of detection using a laser range finder. In addition, a rapidly-exploring random tree algorithm to generate waypoint paths around obstacles known a priori is presented, and a dynamic geometric algorithm to generate paths around detected obstacles is derived. The algorithms are demonstrated in simulation and in flight tests on a fixed-wing miniature air vehicle (MAV).
Decentralized Perimeter Surveillance Using A Team Of Uavs, Timothy Mclain, Randal W. Beard, Derek Kingston, Ryan S. Holt, David W. Casbeer
Decentralized Perimeter Surveillance Using A Team Of Uavs, Timothy Mclain, Randal W. Beard, Derek Kingston, Ryan S. Holt, David W. Casbeer
Faculty Publications
This paper poses the cooperative perimeter-surveillance problem and offers a decentralized solution that accounts for perimeter growth (expanding or contracting) and insertion/deletion of team members. By identifying and sharing the critical coordination information and by exploiting the known communication topology, only a small communication range is required for accurate performance. Simulation and hardware results are presented that demonstrate the applicability of the solution.
Design And Characterization Of A Dual-Stage, Thermally Actuated Nanopositioner, Neal B. Hubbard, Larry L. Howell
Design And Characterization Of A Dual-Stage, Thermally Actuated Nanopositioner, Neal B. Hubbard, Larry L. Howell
Faculty Publications
A nanopositioner is presented that has two stages for independent coarse and fine position control. Thermal microactuators operate both stages. The first stage includes a bistable mechanism: it travels 52 micrometers between two discrete positions. The second stage is mounted on the first stage and moves continuously through an additional 8 micrometers in the same direction as the first stage. Three approaches to the control of the second stage were evaluated in terms of accuracy and manufacturability, and one was selected for the design of the nanopositioner. The device was surface micromachined in a two-layer polysilicon process. Experiments were performed …
Two-Dimensional Grain Boundary Percolation In Alloy 304 Stainless Steel, Brent L. Adams, John A. Basinger, David T. Fullwood, E. R. Homer
Two-Dimensional Grain Boundary Percolation In Alloy 304 Stainless Steel, Brent L. Adams, John A. Basinger, David T. Fullwood, E. R. Homer
Faculty Publications
This work was supported by the MRSEC program of the National Science Foundation under Award Number DMR-0079996. An experimentally-obtained percolation threshold for high-angle random grain boundary networks in alloy 304 stainless steel is compared to thresholds predicted by percolation theory. A discrepancy occurs in the two values (0.46 experimental and 0.65 theoretical). Possible reasons for the discrepancy are explored. The grain boundary network appears to be composed of two distinct sub-networks, with the 'outer' network acting as the dominant contributor to the percolating paths.
Experimental Nonlinear Tracking Control For Nonholonomic Mobile Robots With Input Constraints, Timothy Mclain, Randal W. Beard, Wei Ren, Ji-Sang Sun
Experimental Nonlinear Tracking Control For Nonholonomic Mobile Robots With Input Constraints, Timothy Mclain, Randal W. Beard, Wei Ren, Ji-Sang Sun
Faculty Publications
This paper presents experimental results of nonlinear trajectory tracking controllers for nonholonomic mobile robots with fixed-wing UAV-like input constraints. Programmed to emulate an unmanned air vehicle flying at constant altitude, a nonholonomic mobile robot is assigned to follow a desired trajectory to transition through a sequence of targets in the presence of static and dynamic threats. Two velocity controllers with input constraints are proposed for tracking control. Hardware results using these two velocity controllers are compared to simulation results of dynamic controllers based on nonsmooth backstepping to demonstrate the effectiveness of our approach.
Forest Fire Monitoring With Multiple Small Uavs, David W. Casbeer, Randal W. Beard, Timothy W. Mclain, Sai-Ming Li, Raman K. Mehra
Forest Fire Monitoring With Multiple Small Uavs, David W. Casbeer, Randal W. Beard, Timothy W. Mclain, Sai-Ming Li, Raman K. Mehra
Faculty Publications
Frequent and detailed updates of the development of a forest fire are essential for effective and safe fire fighting. Since a forest fire is typically inaccessible by ground vehicles due to mountainous terrain, small Unmanned Air Vehicles (UAVs) are emerging as a promising solution to the problem of monitoring large forest fires. In this paper we present an effective path planning algorithm for a UAV utilizing infrared images that are collected on-board in realtime. In order to demonstrate the effectiveness of our path planning algorithm in realistic scenarios, we implemented the forest fire propagation model EMBYR to simulate the time …
Finite Approximations To The Second-Order Properties Closure In Single Phase Polycrystals, Brent L. Adams, Xiang Gao, Surya R. Kalidindi
Finite Approximations To The Second-Order Properties Closure In Single Phase Polycrystals, Brent L. Adams, Xiang Gao, Surya R. Kalidindi
Faculty Publications
This work was supported at Brigham Young University and Drexel University by a grant from the US Army Research Office, through the Metallurgy Program headed by Dr. David Stepp. Extension of the first-order theory of microstructure design to considerations of morphological texture is addressed in this paper. The main challenges include the r-interdependence of the 2-point correlation functions of lattice orientation, construction of the corresponding microstructure hull, and its corresponding properties closure(s). It is shown that the correlation functions can be expressed in terms of an intermediate construct, called the texture function; the correlation functions have quadratic dependence in the …
Fabrication Of Hollow Waveguides With Sacrificial Aluminum Cores, John P. Barber, Donald B. Conkey, Jeffrey Ryan Lee, Neal B. Hubbard, Larry L. Howell, Aaron R. Hawkins, Gongliang Yin, Holger Schmidt
Fabrication Of Hollow Waveguides With Sacrificial Aluminum Cores, John P. Barber, Donald B. Conkey, Jeffrey Ryan Lee, Neal B. Hubbard, Larry L. Howell, Aaron R. Hawkins, Gongliang Yin, Holger Schmidt
Faculty Publications
We have developed a process to fabricate dielectric waveguide structures with long hollow cores formed by etching a sacrificial core material. The process is compatible with other planar silicon fabrication techniques. Using aluminum as the sacrificial material, we have investigated fabrication limits and design parameters that determine mechanical integrity of the waveguides. Internal pressure due to the production of gaseous compounds during the core removal process was identified as the yield-limiting factor. A mechanical model based on finite element analysis and confirmed by experiment, predicts ultimate pressures sustainable by these structures. Waveguides less than 10 m wide with 2- m-thick …
Autonomous Vehicle Technologies For Small Fixed-Wing Uavs, Randal Beard, Derek Kingston, Morgan Quigley, Deryl Snyder, Reed Christiansen, Walt Johnson, Timothy Mclain, Michael A. Goodrich
Autonomous Vehicle Technologies For Small Fixed-Wing Uavs, Randal Beard, Derek Kingston, Morgan Quigley, Deryl Snyder, Reed Christiansen, Walt Johnson, Timothy Mclain, Michael A. Goodrich
Faculty Publications
The objective of this paper is to describe the design and implementation of a small semi-autonomous fixed-wing unmanned air vehicle. In particular we describe the hardware and software architectures used in the design. We also describe a low weight, low cost autopilot developed at Brigham Young University and the algorithms associated with the autopilot. Novel PDA and voice interfaces to the UAV are described. In addition, we overview our approach to real-time path planning, trajectory generation, and trajectory tracking. The paper is augmented with movie files that demonstrate the functionality of the UAV and its control software.