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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 127 records · Page 7

All sources NASA NTRS DOE OSTI

NASA NTRS2014

A Recommended New Approach on Motorization Ratio Calculations of Stepper Motors

Stepper motors are widely used on most spacecraft mechanisms requiring repeatable and reliable performance. The unique detent torque characteristics of these type of motors makes them behave differently when subjected to low duty cycle excitations where the applied driving pulses are only energized for a fraction of the pulse duration. This phenomenon is even more pronounced in discrete permanent magnet stepper motors used in the space industry. While the inherent high detent properties of discrete permanent magnets provide desirable unpowered holding performance characteristics, it results in unique behavior especially in low duty cycles. Notably, the running torque reduces quickly to the unpowered holding torque when the duty cycle is reduced. The space industry's accepted methodology of calculating the Motorization Ratio (or Torque Margin) is more applicable to systems where the power is continuously applied to the motor coils like brushless DC motors where the cogging torques are low enough not to affect the linear performance of the motors as a function of applied current. This paper summarizes the theoretical and experimental studies performed on a number of space qualified motors under different pulse rates and duty cycles. It is the intention of this paper to introduce a new approach to calculate the Motorization Ratios for discrete permanent magnet steppers under all full and partial duty cycle regimes. The recommended approach defines two distinct relationships to calculate the Motorization Ratio for 100 percent duty cycle and partial duty cycle, when the motor detent (unpowered holding torque) is the main contributor to holding position. These two computations reflect accurately the stepper motor physical behavior as a function of the command phase (ON versus OFF times of the pulses), pointing out how the torque contributors combine. Important points highlighted under this study are the torque margin computations, in particular for well characterized mechanisms. The rationale at CDR level versus TRR/TRB level will be discussed, aiming at avoiding too much conservatism for units that have extensive test and in flight heritage. A critical topic is related to the magnetic losses and how to sort out such phenomena as a function of the motor type being used. For instance, detent torque is a major contributor that has no reason to evolve during life and is not an uncontrolled torque loss.

Nalbandian, Ruben↗

NASA NTRS1988

Three axis attitude control system

A three-axis attitude control system for an orbiting body comprised of a motor driven flywheel supported by a torque producing active magnetic bearing is described. Free rotation of the flywheel is provided about its central axis and together with limited angular torsional deflections of the flywheel about two orthogonal axes which are perpendicular to the central axis. The motor comprises an electronically commutated DC motor, while the magnetic bearing comprises a radially servoed permanent magnet biased magnetic bearing capable of producing cross-axis torques on the flywheel. Three body attitude sensors for pitch, yaw and roll generate respective command signals along three mutually orthogonal axes (x, y, z) which are coupled to circuit means for energizing a set of control coils for producing torques about two of the axes (x and y) and speed control of the flywheel about the third (z) axis. An energy recovery system, which is operative during motor deceleration, is also included which permits the use of a high-speed motor to perform effectively as a reactive wheel suspended in the magnetic bearing.

Studer, Philip A.↗

NASA NTRS1993

Power Switching Device

The MOS-Controlled Thyristor is a new type of power switching device for faster and more efficient control and management of power electronics. It enables power electronic switching at frequencies of 50 to 100 thousand times a second with much lower power losses than other semiconductor devices. Advantages include electric power savings and smaller space. The device is used in motor and power controllers, AC & DC motor drives and induction heating. Early development was supported by Lewis Research Center (LEW) and other agencies. General Electric''s power semiconductor operation, the initial NASA contractor, was later purchased by Harris Semiconductor.

Source record↗

NASA NTRS2019

Thermal Design of Astrobee Perching Arm

This paper presents the thermal design of actuators in the perching arm of Astrobee robot that will operate inside the International Space Station (ISS) starting in 2019. Since the crew's safety is of the utmost importance on the ISS, all materials used in the Astrobee robot should meet the touch temperature requirements according to the ISS safety standards to protect crew from skin burns by controlling the exposure temperature. The Astrobee perching arm consists of 2-DOF (Degrees-of-Freedom)- arm servo motors and 1-DOF gripper DC motor, which are capable of overheating in the stalled condition. Thermal properties of two types of actuators are verified by monitoring the touch temperature in worst-case operations with no thermal protection. Then, the proper thermal protection designs have been conducted and installed to guarantee the safety in all conditions.

Park, In-Won↗

NASA NTRS2019

Thermal Design of Astrobee Perching Arm

This paper presents the thermal design of actuators in the perching arm of Astrobee robot that will operate inside the International Space Station (ISS) in starting 2019. Since the crew's safety is of the utmost importance on the ISS, all materials used in the Astrobee robot should meet the touch temperature requirements according to the ISS safety standards to protect crew from skin burns. The Astrobee perching arm consists of 2-DOF arm servo motors and 1-DOF gripper DC motor, which are capable of overheating when stalled, particularly given the lack of gravity-driven thermal convection in the ISS zero-gee environment. Thermal properties of two types of actuators are verified by monitoring the touch temperature in worst-case operations with no thermal protection. Then, the proper thermal protection designs have been conducted and installed to guarantee the safety in all conditions.

Park, In-Won↗

NASA NTRS1992

Project Ares 3

The mission of Project Ares is to design and fabricate an Earth prototype, autonomous flying rover capable of flying on the Martian surface. The project was awarded to California State University, Northridge (CSUN) in 1989 where an in-depth paper study was completed. The second year's group, Project Ares 2, designed and fabricated a full-scale flight demonstration aircraft. Project Ares 3, the third and final group, is responsible for propulsion system design and installation, controls and instrumentation, and high altitude testing. The propulsion system consists of a motor and its power supply, geartrain, and propeller. The motor is a four-brush DC motor powered by a 50-V NiCd battery supply. A pulley and belt arrangement is used for the geartrain and includes light weight, low temperature materials. The propeller is constructed from composite materials which ensures high strength and light weight, and is specifically developed to provide thrust at extremely high altitudes. The aircraft is controlled with a ground-based radio control system and an autopilot which will activate in the event that the control signal is lost. A transponder is used to maintain radar contact for ground tracking purposes. The aircraft possesses a small, onboard computer for collecting and storing flight data. To safeguard the possibility of computer failure, all flight data is transmitted to a ground station via a telemetry system. An initial, unpowered, low-level test flight was completed in August of 1991. Testing of systems integration in the second low-level test flight resulted in loss of elevator control which caused considerable damage on landing. Complete failure analysis and repairs are scheduled for September of 1992.

Raymer, Dan↗

NASA NTRS1997

Design of the Cassini Gimbal Actuator: Some Lessons Learned Along the Way

The evolution of a linear servoactuator design is presented. The linear actuator was needed to position Cassini's redundant rocket motors. A device design inherited from JPL's Mariner and Viking Mars missions served as a starting point. The various improvements made and the efforts involved in developing new component sources are discussed. Because the brush type DC motor from the old design was retained, special attention was placed on the reliability testing of the motor and mechanism at all stages of procurement and assembly.

actuators DC motors reliability lifetime↗

NASA NTRS2010

Development of the Upgraded DC Brush Gear Motor for Spacebus Platforms

The obsolescence of materials and processes used in the manufacture of traditional DC brush gear motors has necessitated the development of an upgraded DC brush gear motor (UBGM). The current traditional DC brush gear motor (BGM) design was evaluated using Six-Sigma process to identify potential design and production process improvements. The development effort resulted in a qualified UBGM design which improved manufacturability and reduced production costs. Using Six-Sigma processes and incorporating lessons learned during the development process also improved motor performance for UBGM making it a more viable option for future use as a deployment mechanism in space flight applications.

Berning, Robert H.↗

NASA NTRS1975

Low speed phaselock speed control system

A motor speed control system for an electronically commutated brushless dc motor is provided which includes a phaselock loop with bidirectional torque control for locking the frequency output of a high density encoder, responsive to actual speed conditions, to a reference frequency signal, corresponding to the desired speed. The system includes a phase comparator, which produces an output in accordance with the difference in phase between the reference and encoder frequency signals, and an integrator-digital-to-analog converter unit, which converts the comparator output into an analog error signal voltage. Compensation circuitry, including a biasing means, is provided to convert the analog error signal voltage to a bidirectional error signal voltage which is utilized by an absolute value amplifier, rotational decoder, power amplifier-commutators, and an arrangement of commutation circuitry.

Fulcher, R. W.↗

NASA NTRS1976

Development of a drive system for a sequential space camera

Breadboard models of single and dual motor drives for the shutter, claw and magazine of a space camera system were designed and tested. The single motor technique utilizes a single electronically commutated motor to drive the claw and shutter without resorting to a solenoid actuated clutch for pulse operation. Shutter speed is established by a combination of the cinemode speed and the opening of the conventional DAC two piece shutter. Pulse mode operation is obtained by applying power at a fixed clock rate and removing power at an appropriate point in the mechanical cycle such that the motor comes to rest by system friction. The dual motor approach utilizes a stepper motor to drive the shutter and an electronically commutated dc motor to drive the claw and magazine functions. The motors are synchronized electronically.

Sharpsteen, J. T.↗

NASA NTRS1982

Advanced axial field D.C. motor development for electric passenger vehicle

A wound-field axial-flux dc motor was developed for an electric vehicle drive system. The motor is essentially an axial-flux version of the classical Gramme-ring winding motor, but the active conductors are recessed into slots cut into the two opposite faces of the laminated tape-wound core ring. Three motors were built and tested in the program. The second (functional) model was a six-pole machine which weighed 88.5 kg. It developed 16.9 km (33.0 hp), and a max speed of 4800 rpm. Full load efficiency was 92% and predicted SAE D-cycle efficiency was 88%. The last engineering) model was a 4-pole machine with compoles, allowing a weight reduction to 45 kg (100 lbs.) while addressing some manufacturability problems. The engineering model was rated at 13.2 kw (17.6 hp) at 3000 rpm, with a peak power of 19.8 km (26.4 hp) and a max speed of 7200 rpm. Initial test results on this motor showed poor commutation and efficiency; the program was terminated without resolution of these problems.

Jones, W. J.↗

NASA NTRS1988

Dovetail Rotor Construction For Permanent-Magnet Motors

New way of mounting magnets in permanent-magnet, electronically commutated, brushless dc motors. Magnets wedge shaped, tapering toward center of rotor. Oppositely tapered pole pieces, electron-beam welded to rotor hub, retain magnets against centrifugal force generated by spinning rotor. To avoid excessively long electron-beam welds, pole pieces assembled in segments rather than single long bars.

Kintz, Lawrence J., Jr.↗

NASA NTRS1986

Torque-Summing Brushless Motor

Torque channels function cooperatively but electrically independent for reliability. Brushless, electronically-commutated dc motor sums electromagnetic torques on four channels and applies them to single shaft. Motor operates with any combination of channels and continues if one or more of channels fail electrically. Motor employs single stator and rotor and mechanically simple; however, each of channels electrically isolated from other so that failure of one does not adversely affect others.

Vaidya, J. G.↗

NASA NTRS1970

Brushless direct-current motors

Survey results are presented on the use of unconventional motor windings and switching sequences to optimize performance of brushless dc motors. A motor was built, each coil terminal having a separate, accessible lead. With the shaft and all electronics excluded, length and outside diameter measured 1.25 and 0.75 in., respectively.

Bahm, E. J.↗

DOE OSTI2020

Direct-DC Power in Buildings: Identifying the Best Applications Today for Tomorrow’s Building Sector

Driven by the increased use of direct current (DC) sources (photovoltaics, battery storage) and DC end-use devices (electronics, solid-state lighting, efficient motors), DC power distribution in buildings and DC microgrids have been proposed as a way to achieve greater efficiency, cost savings, and resiliency in a transitioning building sector. Despite these important benefits, several market and technological barriers inhibit the development of DC distribution, and the market for DC in buildings is still largely in the demonstration phase. Therefore, to jumpstart this technology, a clear path forward must emerge at this early stage of deployment. The goal of this paper is to define specific end-use cases for which DC distribution in buildings is a value proposition today by defining clear efficiency and resiliency benefits while addressing barriers to implementation. The paper begins with a technology and market assessment of DC distribution equipment, end uses, and technology standards. That is followed by results from an expert elicitation of DC power and building end-use professionals (e.g., electrical designers, building operators, engineers) and reports on-site visits and lessons learned from successful (and less successful) field deployments of DC distribution projects in North America. We present specific adoption pathways at the community and building level that can be implemented today, and evaluate them using qualitative and quantitative metrics, such as technology and market readiness, energy savings, and resiliency.

building-level electrical distribution↗

DOE OSTI2021

Direct-DC Power in Buildings: Identifying the Best Applications Today for Tomorrow’s Building Sector

Driven by the increased use of direct current (DC) sources (photovoltaics, battery storage) and DC end-use devices (electronics, solid-state lighting, efficient motors), DC power distribution in buildings and DC microgrids have been proposed as a way to achieve greater efficiency, cost savings, and resiliency in a transitioning building sector.Despite these important benefits, several market and technological barriers inhibit the development of DC distribution, and the market for DC in buildings is still largely in the demonstration phase. Therefore, to jumpstart this technology, a clear path forward must emerge at this early stage of deployment. The goal of this paper is to define specific end-use cases for which DC distribution in buildings is a value proposition today by defining clear efficiency and resiliency benefits while addressing barriers to implementation.The paper begins with a technology and market assessment of DC distribution equipment, end uses, and technology standards. That is followed by results from an expert elicitation of DC power and building end-use professionals (e.g., electrical designers, building operators, engineers) and reports on-site visits and lessons learned from successful (and less successful) field deployments of DC distribution projects in North America. We present specific adoption pathways at the community and building level that can be implemented today, and evaluate them using qualitative and quantitative metrics, such as technology and market readiness, energy savings, and resiliency.

Vossos, Evangelos↗

NASA NTRS1971

A motor canister designed for prolonged operation in space

A special canister was designed to protest the dc motors used on the ISIS 1 antenna unit. The canister is provided with a pressure-monitoring device and has a special shaft seal that imparts minimum load to the motor output shaft. The development and flight testing of the canister are discussed. Problems that were encountered during fabrication and inspection and the problems caused by material/lubricant incompatibility and low temperature are also discussed.

Wells, A.↗

NASA NTRS1972

Hybrid circuit modules for motor commutation and control

Thick film hybrid techniques are used to develop circuitry for a brushless dc motor commutator. The power commutator contains the driving circuit and an amplifier that controls the armature current. A position decoder contains digital integrated circuits which receive the signals from the armature position sensors and generate the driving signals for the power commutator in the proper sequence. These units drive motors with stall currents up to about 400 mA.

Dekramer, C.↗