Tech Briefs

Improved Bearingless Switched-Reluctance Motor

Performance is better and design simpler, relative to a prior bearingless switched-reluctance motor. The Morrison rotor, named after its inventor, is a hybrid rotor for use in a bearingless switched-reluctance electric motor. The motor is characterized as bearingless in the sense that it does not rely on conventional mechanical bearings: instead, it functions as both a magnetic bearing and a motor. Bearingless switched-reluctance motors are attractive for use in situations in which large variations in temperatures and/or other extreme conditions preclude the use of conventional electric motors and mechanical bearings.

Posted in: Machinery & Automation, Briefs, TSP

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Compact, Pneumatically Actuated Filter Shuttle

This unit satisfies a special need for alternate observation in two spectral bands. A compact, pneu- matically actuated filter shuttle has been invented to enable alternating imaging of a wind-tunnel model in two different spectral bands characteristic of the pressure and temperature responses of a pressureand temperature-sensitive paint. This filter shuttle could also be used in other settings in which there are requirements for alternating imaging in two spectral bands. Pneumatic actuation was chosen because of a need to exert control remotely (that is, from outside the wind tunnel) and because the power leads that would be needed for electrical actuation would pose an unacceptable hazard in the wind tunnel. The entire shuttle mechanism and its housing can be built relatively inexpensively [

Posted in: Machinery & Automation, Briefs, TSP

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Software for Planning Scientific Activities on Mars

Mixed-Initiative Activity Plan Generator (MAPGEN) is a ground-based computer program for planning and scheduling the scientific activities of instrumented exploratory robotic vehicles, within the limitations of available resources onboard the vehicle. MAPGEN is a combination of two prior software systems: (1) an activity-planning program, APGEN, developed at NASA’s Jet Propulsion Laboratory and (2) the Europa planner/scheduler from NASA Ames Research Center. MAPGEN performs all of the following functions:

Posted in: Software, Briefs, TSP

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Software for Training in Pre-College Mathematics

The Intelligent Math Tutor (IMT) is a computer program for training students in pre-college and college-level mathe- matics courses, including fundamentals, intermediate algebra, college algebra, and trigonometry. The IMT can be executed on a server computer for access by students via the Internet; altern- atively, it can be executed on students’ computers equipped with compactdisk/ read-only-memory (CD-ROM) drives. The IMT provides interactive exercises, assessment, tracking, and an on-line graphing calculator with algebraic- manipulation capabilities. The IMT provides an innovative combination of content, delivery mechanism, and artificial intelligence. Careful organization and presentation of the content make it possible to provide intelligent feedback to the student based on performance on exercises and tests. The tracking and feedback mechanisms are implemented within the capabilities of a commercial off-the-shelf development software tool and are written in the Unified Modeling Language to maximize reuse and minimize development cost. The graphical calculator is a standard feature of most college and precollege algebra and trigonometry courses. Placing this functionality in a Java applet decreases the cost, provides greater capabilities, and provides an opportunity to integrate the calculator with the lessons.

Posted in: Software, Briefs

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Software for Simulating a Complex Robot

RoboSim (Robot Simulation) is a computer program that simulates the poses and motions of the Robonaut — a developmental anthropomorphic robot that has a complex system of joints with 43 degrees of freedom and multiple modes of operation and control. RoboSim performs a full kinematic simulation of all degrees of freedom. It also includes interface components that duplicate the functionality of the real Robonaut interface with control software and human operators. Basically, users see no difference between the real Robonaut and the simulation. Consequently, new control algorithms can be tested by computational simulation, without risk to the Robonaut hardware, and without using excessive Robonaut-hardware experimental time, which is always at a premium. Previously developed software incorporated into RoboSim includes Enigma (for graphical displays), OSCAR (for kinematical computations), and NDDS (for communication between the Robonaut and external software). In addition, RoboSim incorporates unique inverse-kinematical algorithms for chains of joints that have fewer than six degrees of freedom (e.g., finger joints). In comparison with the algorithms of OSCAR, these algorithms are more readily adaptable and provide better results when using equivalent sets of data.

Posted in: Software, Briefs, TSP

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Software Helps Retrieve Information Relevant to the User

The Adaptive Indexing and Retrieval Agent (ARNIE) is a code library, designed to be used by an application program, that assists human users in retrieving desired information in a hypertext setting. Using ARNIE, the program implements a comp- utational model for interactively learning what information each human user considers relevant in context. The model, called a “relevance network,” incrementally adapts retrieved information to users’ individual profiles on the basis of feedback from the users regarding specific queries. The model also generalizes such knowledge for subsequent derivation of relevant references for similar queries and profiles, thereby, assisting users in filtering information by relevance. ARNIE thus enables users to categorize and share information of interest in various contexts. ARNIE encodes the relevance and structure of information in a neural network dynamically configured with a genetic algorithm. ARNIE maintains an internal database, wherein it saves associations, and from which it returns associated items in response to a query. A C++ compiler for a platform on which ARNIE will be utilized is necessary for creating the ARNIE library but is not necessary for the execution of the software.

Posted in: Software, Briefs, TSP

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Software for Diagnosis of Multiple Coordinated Spacecraft

Distributed Real-Time Model-Based Diagnosis (DRMD) is a computer program for diagnosing faults in multiple spacecraft cooperating in a specific task (e.g., flying in formation to constitute an inter- ferometer). DRMD takes advantage of both (1) the superiority of model-based software for representing complex hardware systems (though not necessarily for making diagnoses in real time) and (2) the ability of rulebased software to provide diagnoses in real time. A multiple-spacecraft system is modeled as a set of interacting subsystems that comprise interacting components, each of which operates in one of a number of modes that define the relationships between its inputs and outputs. Then diagnosis is performed following a knowledge-compilation approach implemented in a three-step process: (1) A representation of the system is expanded into a network of processed components at compilation time; (2) a Boolean equation for the system is constructed at compilation time; and (3) the equation is evaluated iteratively at run time. The programming language used to express the model of the system defines observables and commands local to each subsystem, thereby facilitating the distribution of portions of the Boolean equation to multiple computers on the multiple spacecraft.

Posted in: Software, Briefs, TSP

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