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A Dynamic Optimal Trajectory Generator For Cartesian Path Following, Edward Red
A Dynamic Optimal Trajectory Generator For Cartesian Path Following, Edward Red
Faculty Publications
This paper considers a dynamic and adaptive trajectory generator for negotiating paths using S-curves. Applying constant jerk transitions between the constant acceleration and deceleration periods of the trajectory, the trajectory will optimally transition to the desired speed setting. Optimal is defined to be the minimum time to transition from the current speed to the set speed for the move segment when jerk and acceleration are limited. The S-curve equations will adapt to instantaneous changes in speed setting and path length. An integrated motion planner will determine allowable speeds and transitional profiles based on the remaining move distance.
Fuel Saving Strategies For Separated Spacecraft Interferometry, Timothy Mclain, Randal W. Beard, Christopher A. Bailey
Fuel Saving Strategies For Separated Spacecraft Interferometry, Timothy Mclain, Randal W. Beard, Christopher A. Bailey
Faculty Publications
Separated spacecraft interferometry missions will require spacecraft to move in a coordinated fashion to ensure minimal and balanced consumption of fuel. This paper develops strategies for determining interferometry mission plans that result in significant fuel savings over standard approaches. Simulation results demonstrate that valuable reductions in fuel consumption can be realized by combining the retargeting and imaging maneuvers required to image multiple stellar sources. Fuel-optimal imaging strategies have been developed for two-spacecraft interferometry missions similar to the proposed Space Technology 3 mission using chained local optimization methods. Based on these strategies, sampling pattern guidelines for space-borne interferometry missions have been …
Trajectory Planning For Coordinated Rendezvous Of Unmanned Air Vehicles, Timothy W. Mclain, Randal W. Beard
Trajectory Planning For Coordinated Rendezvous Of Unmanned Air Vehicles, Timothy W. Mclain, Randal W. Beard
Faculty Publications
A trajectory generation strategy that facilitates the coordination of multiple unmanned air vehicles is developed. Of particular interest is the planning of threat-avoiding trajectories that result in the simultaneous arrival of multiple UAVs at their targets. In this approach, paths to the target are modeled using the physical analogy of a chain. A unique strength of the planning approach is the ability to specify or alter the path length by adding or subtracting links from the chain. Desirable paths to the target are obtained by simulating the dynamics of the chain where threats apply repulsive forces to the chain and …
Statistical Continuum Theory For Large Plastic Deformation Of Polycrystalline Materials, Brent L. Adams, S. Ahzi, H. Garmestani, S. Lin
Statistical Continuum Theory For Large Plastic Deformation Of Polycrystalline Materials, Brent L. Adams, S. Ahzi, H. Garmestani, S. Lin
Faculty Publications
This paper focuses on the application of statistical continuum mechanics to the prediction of mechanical response of polycrystalline materials and microstructure evolution under large plastic deformations. A statistical continuum mechanics formulation is developed by applying a Green's function solution to the equations of stress equilibrium in an infinite domain. The distribution and morphology of grains (crystals) in polycrystalline materials is represented by a set of correlation functions that are described by the corresponding probability functions. The elastic deformation is neglected and a viscoplastic power law is employed for crystallographic slip in single crystals. In this formulation, two- and three-point probability …
Fuel Optimization For Constrained Rotation Of Satellite Formations, Timothy Mclain, Randal W. Beard, Fred Y. Hadaegh
Fuel Optimization For Constrained Rotation Of Satellite Formations, Timothy Mclain, Randal W. Beard, Fred Y. Hadaegh
Faculty Publications
This paper considers the problem of reorienting a constellation of spacecraft such that the fuel distributed across the constellation is both conserved and expended uniformly. Results are derived for constellations with an arbitrary number of spacecraft, assuming that the constellation is in free space, that the spacecraft mass is time invariant, and that the thrusters can produce thrust in any direction. An open-loop control algorithm is derived by minimizing a cost function that trades off total fuel minimization and fuel equalization. The associated optimization problem is shown to be amenable to standard algorithms. Simulation results using a four-spacecraft constellation are …