Resolved rate and torque control schemes for large scale space based kinematically redundant manipulators

Resolved rate control of kinematically redundant ground based manipulators is a challenging problem. The structural, actuator, and control loop frequency characteristics of industrial grade robots generally allow operation with resolved rate control; a rate command is achievable with good accuracy. However, space based manipulators are different, typically have less structural stiffness, more motor and joint friction, and lower control loop cycle frequencies. These undesirable characteristics present a considerable Point of Resolution (POR) control problem for space based, kinematically redundant manipulators for the following reason: a kinematically redundant manipulator requires an arbitrary constraint to solve for the joint rate commands. A space manipulator will not respond to joint rate commands because of these characteristics. A space based manipulator simulation, including free end rigid body dynamics, motor dynamics, motor striction/friction, gearbox backlash, joint striction/friction, and Space Station Remote Manipulator System type configuration parameters, is used to evaluate the performance of a documented resolved rate control law. Alternate schemes which include torque control are also evaluated

Kinematically redundant arm formulations for coordinated multiple arm implementations

Although control laws for kinematically redundant robotic arms were presented as early as 1969, redundant arms have only recently become recognized as viable solutions to limitations inherent to kinematically sufficient arms. The advantages of run-time control optimization and arm reconfiguration are becoming increasingly attractive as the complexity and criticality of robotic systems continues to progress. A generalized control law for a spatial arm with 7 or more degrees of freedom (DOF) based on Whitney's resolved rate formulation is given. Results from a simulation implementation utilizing this control law are presented. Furthermore, results from a two arm simulation are presented to demonstrate the coordinated control of multiple arms using this formulation

Investigation of Boundary Conditions for Flexible Multibody Spacecraft Dynamics

In support of both the Space Shuttle and International Space Station programs, a set of generic multibody dynamics algorithms integrated within the Trick simulation environment have addressed the variety of on-orbit manipulator simulation requirements for engineering analysis, procedures development and crew familiarization/training at the NASA Johnson Space Center (JSC). Enhancements to these dynamics algorithms are now being driven by a new set of Constellation program requirements for flexible multibody spacecraft simulation. One particular issue that has been discussed within the NASA community is the assumption of cantilever-type flexible body boundary conditions. This assumption has been commonly utilized within manipulator multibody dynamics formulations as it simplifies the computation of relative motion for articulated flexible topologies. Moreover, its use for modeling of space-based manipulators such as the Shuttle Remote Manipulator System (SRMS) and Space Station Remote Manipulator System (SSRMS) has been extensively validated against flight data. For more general flexible spacecraft applications, however, the assumption of cantilever-type boundary conditions may not be sufficient. This paper describes the boundary condition assumptions that were used in the original formulation, demonstrates that this formulation can be augmented to accommodate systems in which the assumption of cantilever boundary conditions no longer applies, and verifies the approach through comparison with an independent model previously validated against experimental hardware test data from a spacecraft flexible dynamics emulator

Development and Evaluation of an Order-N Formulation for Multi-Flexible Body Space Systems

This paper presents development of a generic recursive Order-N algorithm for systems with rigid and flexible bodies, in tree or closed-loop topology, with N being the number of bodies of the system. Simulation results are presented for several test cases to verify and evaluate the performance of the code compared to an existing efficient dense mass matrix-based code. The comparison brought out situations where Order-N or mass matrix-based algorithms could be useful

Social Campaigns for Community Participation in Environmental Management

This document serves as a compilation of lessons learned and recommendations from our semester’s work. Given MM’s interests, we chose to use community-based social marketing (CBSM) as a framework with which to evaluate strategic approaches to mobilize communities

Extensive features of tight oligosaccharide binding revealed in high-resolution structures of the maltodextrin transport/chemosensory receptor

AbstractBackground: Active-transport processes perform a vital function in the life of a cell, maintaining cell homeostasis and allowing access of nutrients. Maltodextrin/maltose-binding protein (MBP; Mr = 40K) is a receptor protein which serves as an initial high-affinity binding component of the active-transport system of maltooligosaccharides in bacteria. MBP also participates in chemotaxis towards maltooligosaccharides. The interaction between MBP and specific cytoplasmic membrane proteins initiates either active transport or chemotaxis. In order to gain new understanding of the function of MBP, especially its versatility in binding different linear and cyclic oligosaccharides with similar affinities, we have undertaken high-resolution X-ray analysis of three oligosaccharide-bound structures.Results: The structures of MBP complexed with maltose, maltotriose and maltotetraose have been refined to high resolutions (1.67 to 1.8 Å). These structures provide details at the atomic level of many features of oligosaccharide binding. The structures reveal differences between buried and surface binding sites and show the importance of hydrogen bonds and van der Waals interactions, especially those resulting from aromatic residue stacking. Insights are provided into the structural plasticity of the protein, the binding affinity and the binding specificity with respect to α/β anomeric preference and oligosaccharide length. In addition, the structures demonstrate the different conformations that can be adopted by the oligosaccharide within the complex.Conclusions: MBP has a two-domain structure joined by a hinge-bending region which contains the substrate-binding groove. The bound maltooligosaccharides have a ribbon-like structure: the edges of the ribbon are occupied by polar hydroxyl groups and the flat surfaces are composed of nonpolar patches of the sugar ring faces. The polar groups and nonpolar patches are heavily involved in forming hydrogen bonds and van der Waals contacts, respectively, with complimentary residues in the groove. Hinge-bending between the two domains enables the participation of both domains in the binding and sequestering of the oligosaccharides. Changes in the subtle contours of the binding site allow binding of maltodextrins of varying length with similarly high affinities. The fact that the three bound structures are essentially identical ensures productive interaction with the oligomeric membrane proteins, which are distinct for transport and chemotaxis

An Efficient Solution Method for Multibody Systems with Loops Using Multiple Processors

This paper describes a multibody dynamics algorithm formulated for parallel implementation on multiprocessor computing platforms using the divide-and-conquer approach. The system of interest is a general topology of rigid and elastic articulated bodies with or without loops. The algorithm divides the multibody system into a number of smaller sets of bodies in chain or tree structures, called "branches" at convenient joints called "connection points", and uses an Order-N (O (N)) approach to formulate the dynamics of each branch in terms of the unknown spatial connection forces. The equations of motion for the branches, leaving the connection forces as unknowns, are implemented in separate processors in parallel for computational efficiency, and the equations for all the unknown connection forces are synthesized and solved in one or several processors. The performances of two implementations of this divide-and-conquer algorithm in multiple processors are compared with an existing method implemented on a single processor

Crystal structures of I-SceI complexed to nicked DNA substrates: snapshots of intermediates along the DNA cleavage reaction pathway

I-SceI is a homing endonuclease that specifically cleaves an 18-bp double-stranded DNA. I-SceI exhibits a strong preference for cleaving the bottom strand DNA. The published structure of I-SceI bound to an uncleaved DNA substrate provided a mechanism for bottom strand cleavage but not for top strand cleavage. To more fully elucidate the I-SceI catalytic mechanism, we determined the X-ray structures of I-SceI in complex with DNA substrates that are nicked in either the top or bottom strands. The structures resemble intermediates along the DNA cleavage reaction. In a structure containing a nick in the top strand, the spatial arrangement of metal ions is similar to that observed in the structure that contains uncleaved DNA, suggesting that cleavage of the bottom strand occurs by a common mechanism regardless of whether this strand is cleaved first or second. In the structure containing a nick in the bottom strand, a new metal binding site is present in the active site that cleaves the top strand. This new metal and a candidate nucleophilic water molecule are correctly positioned to cleave the top strand following bottom strand cleavage, providing a plausible mechanism for top strand cleavage

Refinement and Evaluation of the Forest Management Plan for the Waiākea Timber Management Area

Hawai’i’s economy is 2 dimensional, relying both on agricultural products and tourism. In order for the state to have a more sustainable economy it’s going to need multiple sources of revenues and not rely primarily on one. Currently there is no successful model of timber harvesting in Hawaii. Developing a forestry industry in Hawaii would be very beneficial for the State and its people. In 1956, a model forest for commercial forestry was initiated in the 12,500-acre area called Waiākea on the Big Island. The initial objective of the Waiākea Timber management area (WTMA) was to establish a supply of forest resources to provide a continuous wood supply for a forest products industry. From 1956-1980, the area was monitored to determine the adaptability and growth potential of 84 introduced timber species. Due to inefficient start up problems regarding development and financial issues the planned major harvest never happened. This capstone improves upon the existing resource management plan through the knowledge I’ve gained through this masters program. I propose several types of analysis to track the success of the proposed management plan, including cost benefit, financial analysis on the revenue from the area, inventory of invasive species, population of native species that are in endangered, areas set aside for experiment and learning, and feedback from all levels of groups in Hawaiʻi by meetings, surveying, and questionnaires. In conclusion, this capstone presents a sustainable commercial harvest operation plan for WTMA. This plan promotes healthy land stewardship for WTMA and surrounding forest reserves, creating a new source of revenue that sustainably stimulates and supports the growth of the environment, and the welfare of people of Hawai’i

Mode Selection Techniques in Variable Mass Flexible Body Modeling

In developing a flexible body spacecraft simulation for the Launch Abort System of the Orion vehicle, when a rapid mass depletion takes place, the dynamics problem with time varying eigenmodes had to be addressed. Three different techniques were implemented, with different trade-offs made between performance and fidelity. A number of technical issues had to be solved in the process. This paper covers the background of the variable mass flexibility problem, the three approaches to simulating it, and the technical issues that were solved in formulating and implementing them