16,181 research outputs found
Designing a Robotic Platform for Investigating Swarm Robotics
This paper documents the design and subsequent construction of a low-cost, flexible robotic platform for swarm robotics research, and the selection of appropriate swarm algorithms for the implementation of a swarm focused predominantly on target location. The design described herein is intended to allow for the construction of robots large enough to meaningfully interact with their environment while maintaining a low per-robot cost of materials and a low assembly time. The design process is separated into three stages: mechanical design, electrical design, and software design. All major design components are described in detail under the appropriate design section. The BOM for a single robot is also included, along with relevant testing information
Modular switched reluctance machines to be used in automotive applications
In the last decades industry, including also that of electrical machines and drives, was pushed near to its limits by the high market demands and fierce competition. As a response to the demanding challenges, improvements were made both in the design and manufacturing of electrical machines and drives. One of the introduced advanced technological solutions was the modular construction. This approach enables on a hand easier and higher productivity manufacturing, and on the other hand fast repairing in exploitation. Switched reluctance machines (SRMs) are very well fitted for modular construction, since the magnetic insulation of the phases is a basic design requirement. The paper is a survey of the main achievements in the field of modular electrical machines, (especially SRMs), setting the focus on the machines designed to be used in automotive applications
Towards Fully Additively-Manufactured Permanent Magnet Synchronous Machines: Opportunities and Challenges
With the growing interest in electrification and as hybrid and pure electric powertrains are adopted in more applications, electrical machine design is facing challenges in terms of meeting very demanding performance metrics for example high specific power, harsh environments, etc. This provides clear motivation to explore the impact of advanced materials and manufacturing on the performance of electrical machines. This paper provides an overview of additive manufacturing (AM) approaches that can be used for constructing permanent magnet (PM) machines, with a specific focus on additively-manufactured iron core, winding, insulation, PM as well as cooling systems. Since there has only been a few attempts so far to explore AM in electrical machines (especially when it comes to fully additively-manufactured machines), the benefits and challenges of AM have not been comprehensively understood. In this regard, this paper offers a detailed comparison of multiple multi-material AM methods, showing not only the possibility of fully additively-manufactured PM machines but also the potential significant improvements in their mechanical, electromagnetic and thermal properties. The paper will provide a comprehensive discussion of opportunities and challenges of AM in the context of electrical machines
Electrical Cable Design for Urban Air Mobility Aircraft
Urban Air Mobility (UAM) describes a new type of aviation focused on efficient flight within urban areas for moving people and goods. There are many different configurations of UAM vehicles, but they generally use an electric motor driving a propeller or ducted fan powered by batteries or a hybrid electric power generation system. Transmission cables are used to move energy from the storage or generation system to the electric motors. Though terrestrial power transmission cables are well established technology, aviation applications bring a whole host of new design challenges that are not typical considerations in terrestrial applications. Aircraft power transmission cable designs must compromise between resistance-per-length, weight-per-length, volume constraints, and other essential qualities. In this paper we use a multidisciplinary design optimization to explore the sensitivity of these qualities to a representative tiltwing turboelectric UAM aircraft concept. This is performed by coupling propulsion and thermal models for a given mission criteria. Results presented indicate that decreasing cable weight at the expense of increasing cable volume or cooling demand is effective at minimizing maximum takeoff weight (MTO). These findings indicate that subsystem designers should update their modeling approach in order to contribute to system-level optimality for highly-coupled novel aircraft.
Mobility (UAM) vehicles have the potential to change urban and intra-urban transport in
new and interesting ways. In a series of two papers Johnson et al.1 and Silva et al.2 presented four
reference vehicle configurations that could service different niches in the UAM aviation category. Of those,
this paper focuses on the Vertical Take-off and Landing (VTOL) tiltwing configuration shown in Figure 1.
This configuration uses a turboelectric power system, feeding power from a turbo-generator through a system
of transmission cables to four motors spinning large propellers on the wings. Previous work on electric cable subsystems leaves much yet to be explored, especially in the realm of
subsystem coupling. Several aircraft optimization studies1, 3, 4 only considered aircraft electrical cable weight
and ignored thermal effects. Electric and hybrid-electric aircraft studies by Mueller et al.5 and Hoelzen
et al.6 selected a cable material but did not investigate alternative materials. Advanced cable materials
have been examined by a number of authors: Alvarenga7 examined carbon nanotube (CNT) conductors for
low-power applications. De Groh8, 9 examined CNT conductors for motor winding applications. Behabtu
et al.,10 and Zhao et al.11 examined CNT conductors for a general applications. There were some studies
that examined the thermal effects of cables but they did not allow the cable material to change; El-Kady12
optimized ground-cable insulation and cooling subject constraints. Vratny13 selected cable material based
on vehicle power demand, and required resulting cable heat to be dissipated by the Thermal Management
System (TMS). None of these previous studies allowed for the selection of the cable material based on a
system level optimization goal. Instead, they focused on sub-system optimality such as minimum weight,
which comes at the expense of incurring additional costs for other subsystems. Dama14 selected overhead
transmission line materials using a weighting function and thermal constraints. However, that work was not
coupled with any aircraft subsystems like a TMS.
The traditional aircraft design approach, which relies on assembling groups of optimal subsystems, breaks
down when considering novel aircraft concepts like the tiltwing vehicle. In a large part, this is because novel
concepts have a much higher degree of interaction or coupling between subsystems. For example, when a
cable creates heat, this heat needs to be dissipated by the TMS, which needs power supplied by the turbine,
and delivering the power creates more heat. The cable, the TMS, and the turbine are all coupled. A change
to one subsystem will affect all the other subsystems, much to the consternation of subsystem design experts.
Multidisciplinary optimization is the design approach that can address these challenges. However, to fully
take advantage of this, we must change the way we think about subsystem design. Specifically, we must
move away from point design, and focus on creating solution spaces.
The work presented in this paper uses the multidisciplinary optimization approach with aircraft level
models to study the system-level sensitivity of cable traits: weight-per-length and resistance-per-length.
Additionally, we examined the effects of vehicle imposed volume constraints on these traits. This is useful
for three purposes: (1) to demonstrate a framework that can perform a coupled analysis between the aircraft
thermal and propulsion systems, (2) to provide a method by which future cable designs can be evaluated
against each other given a system-level design goal, (3) to provide insight into what cable properties may
be promising for future research. This last element is explored given the caveat that the models contained
in this analysis do not represent high-fidelity systems. Thus, while we can demonstrate coupling in between
systems, the exact system-level sensitivity to a given parameter may change if a subsystem model or the
assumptions governing that model change.
The organization of this paper is as follows, in Sec II we outline a method to combine the VTOL vehicle
design and cable information in order to produce cables sensitivity studies. Results analysis and discussion
are contained in Sec III. Conclusions are presented in Sec IV
Design and fabrication of a long-life Stirling cycle cooler for space application. Phase 3: Prototype model
A second-generation, Stirling-cycle cryocooler (cryogenic refrigerator) for space applications, with a cooling capacity of 5 watts at 65 K, was recently completed. The refrigerator, called the Prototype Model, was designed with a goal of 5 year life with no degradation in cooling performance. The free displacer and free piston of the refrigerator are driven directly by moving-magnet linear motors with the moving elements supported by active magnetic bearings. The use of clearance seals and the absence of outgassing material in the working volume of the refrigerator enable long-life operation with no deterioration in performance. Fiber-optic sensors detect the radial position of the shafts and provide a control signal for the magnetic bearings. The frequency, phase, stroke, and offset of the compressor and expander are controlled by signals from precision linear position sensors (LVDTs). The vibration generated by the compressor and expander is cancelled by an active counter balance which also uses a moving-magnet linear motor and magnetic bearings. The driving signal for the counter balance is derived from the compressor and expander position sensors which have wide bandwidth for suppression of harmonic vibrations. The efficiency of the three active members, which operate in a resonant mode, is enhanced by a magnetic spring in the expander and by gas springs in the compressor and counterbalance. The cooling was achieved with a total motor input power of 139 watts. The magnetic-bearing stiffness was significantly increased from the first-generation cooler to accommodate shuttle launch vibrations
Space Transportation Materials and Structures Technology Workshop
The Space Transportation Materials and Structures Technology Workshop was held on September 23-26, 1991, in Newport News, Virginia. The workshop, sponsored by the NASA Office of Space Flight and the NASA Office of Aeronautics and Space Technology, was held to provide a forum for communication within the space materials and structures technology developer and user communities. Workshop participants were organized into a Vehicle Technology Requirements session and three working panels: Materials and Structures Technologies for Vehicle Systems, Propulsion Systems, and Entry Systems
Solar energy bibliography
Listings are provided of technical briefs, reports, and papers pertaining to research being performed in the field of solar energy
A cryogenic rotation stage with a large clear aperture for the half-wave plates in the Spider instrument
We describe the cryogenic half-wave plate rotation mechanisms built for and
used in Spider, a polarization-sensitive balloon-borne telescope array that
observed the Cosmic Microwave Background at 95 GHz and 150 GHz during a
stratospheric balloon flight from Antarctica in January 2015. The mechanisms
operate at liquid helium temperature in flight. A three-point contact design
keeps the mechanical bearings relatively small but allows for a large (305 mm)
diameter clear aperture. A worm gear driven by a cryogenic stepper motor allows
for precise positioning and prevents undesired rotation when the motors are
depowered. A custom-built optical encoder system monitors the bearing angle to
an absolute accuracy of +/- 0.1 degrees. The system performed well in Spider
during its successful 16 day flight.Comment: 11 pages, 7 figures, Published in Review of Scientific Instruments.
v2 includes reviewer changes and longer literature revie
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