Electronic beam switching commutator Patent
Using electron beam switching for brushless motor commutation
Studer, P. A.↗
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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.↗
The Goddard helical tape recorder
A spacecraft recorder was developed with the objective of functioning continuously for 5 years. The resulting design employed a metallic tape wound in a 200-turn helix. A direct drive, brushless dc torquer and servo speed control drove the recorder at 3 rpm for recording and 54 rpm for playback.
Martin, F. T.↗
High torque CMG rotary actuator
A high torque rotary actuator was designed, fabricated and tested. Exacting requirements were placed on performance and physical characteristics of the actuator, particularly in the area of stiffness, backlash, torque ripple, power and size and weight. A brushless dc motor was designed utilizing rare earth magnets to meet power and weight requirements. A 26-to-1 planetary roller gear transmission was selected to best meet overall requirements. The transmission utilizes parallel gear and roller paths to minimize backlash and breakaway torque.
Source record↗
Magnetic tape recorder for long operating life in space.
Magnetic tape recorders have long been used on satellites and spacecraft for onboard storage of large quantities of data. As satellites enter into commercial service, long operating life at high reliability becomes important. Also, the presently planned long-duration space flights to the outer planets require long-life tape recorders. Past satellite tape recorders have achieved a less than satisfactory performance record and the operating life of other spacecraft tape recorders has been relatively short and unpredictable. Most failures have resulted from malfunctions of the mechanical tape transport. Recent advances in electric motors and static memories have allowed the development of a new tape recorder which uses a very simple tape transport with few possible failure modes. It consists only of two brushless dc motors, two tape guides, and the recording heads. Relatively low tape tension, wide torque capability, and precise speed control facilitate design for mechanical reliability to match that of tape-recorder electronics.
Bahm, E. J.↗
A new approach to long-life noncontacting electromechanical devices
Brushless dc motors are finding increasing application in space. Likewise, with the advent of the light emitting diode, noncontacting encoders are gradually replacing sliding contact types. The direct drive concept has proved its merit and is now the preferred approach for tape recorders and low to moderate torque instrument drives. The final step in this evolution is the magnetic bearing, which now appears feasible for several applications. Where it can be applied in a totally noncontacting system, life and reliability will be a function of the electronic controls, where redundancy, derating, and quality assurance approaches virtually assure the desired lifetime and failure rate.
Devine, E. J.↗
A review of the technology of noncontacting systems
Advanced components are the fundamental building blocks of advanced systems and spacecraft. Non-contacting elements, including magnetic bearings, brushless and ironless armature motors, rotary transformers and encoders, are discussed. Most of the information presented in this paper has been generated from a continuing program of component development. The aim of this paper is to identify some of the important design features and provide a perspective on the state of development reached to date.
Studer, P. A.↗
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.↗
DC drive system for cine/pulse cameras
Camera-drive functions are separated mechanically into two groups which are driven by two separate dc brushless motors. First motor, a 90 deg stepper, drives rotating shutter; second electronically commutated motor drives claw and film transport. Shutter is made of one piece but has two openings for slow and fast exposures.
Gerlach, R. H.↗
Development of a magnetically suspended momentum wheel
An engineering model of a magnetically suspended momentum wheel was designed, fabricated, and tested under laboratory conditions. The basic unit consisted of two magnet bearings, a sculptured aluminum rotor, brushless dc spin motor, and electronics. The magnet bearings, utilizing rare-earth cobltrat-samarium magnets were active radially and passive axially. The results of the program showed that momentum wheels with magnetic bearings are feasible and operable, and that magnetic bearings of this type are capable of being used for applications where high capacity, high stiffness, and low power consumption are required. The tests performed developed criteria for improved performance for future designs.
Hamilton, S. B.↗
Reaction wheel assembly
The fabrication and testing of three reaction wheels with associated drive and system monitoring electronics and brushless dc spin motors are discussed; the wheels are intended for use in a teleoperator simulator. Test results are included as graphs.
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Development of a drive system for a sequential space camera
An electronically commutated dc motor is reported for driving the camera claw and magazine, and a stepper motor is described for driving the shutter with the two motors synchronized electrically. Subsequent tests on the breadboard positively proved the concept, but further development beyond this study should be done. The breadboard testing also established that the electronically commutated motor can control speed over a wide dynamic range, and has a high torque capability for accelerating loads. This performance suggested the possibility of eliminating the clutch from the system while retaining all of the other mechanical features of the DAC, if the requirement for independent shutter speeds and frame rates can be removed. Therefore, as a final step in the study, the breadboard shutter and shutter drive were returned to the original DAC configuration, while retaining the brushless dc motor drive.
Sharpsteen, J. T.↗
High torque DC motor fabrication and test program
The testing of a standard iron and standard alnico permanent magnet two-phase, brushless dc spin motor for potential application to the space telescope has been concluded. The purpose of this study was to determine spin motor power losses, magnetic drag, efficiency and torque speed characteristics of a high torque dc motor. The motor was designed and built to fit an existing reaction wheel as a test vehicle and to use existing brass-board commutation and torque command electronics. The results of the tests are included in this report.
Makus, P.↗
Step motor damping for high-inertia loads
Brushless tachometer generates signals for moving large and varying loads precisely. Stepper waveform generator sends short sequence of pulses to instruct control logic circuit to perform its function-that is, to select proper windings and directions of excitation to drive and damp motor. Control logic circuit bases decisions on following logic signals, derived from tachometer: rate direction, rate threshold, and position.
Veillette, L. J.↗
Alternate bearing design fabrication and test program, exhibit B
A 50 ft-lb-sec (FPS) reaction wheel was modified with an ironless armature brushless dc motor and a magnetic bearing suspension. The purpose was to demonstrate the performance of an alternate bearing concept, i.e., a magnetic bearing suspension, which could be used in Skylab type CMG's to meet the attitude control requirements of long term space stations. A magnetic suspension was built, installed and tested in the 50 FPS reaction wheel. A secondary effort included the build and test of a compatible reaction wheel motor. Performance characteristics of both are presented and discussed.
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Electromechanical flight control actuator, volume 1
An electromechanical actuator was developed that will follow a proportional control command with minimum wasted energy to demonstrate the feasibility of meeting space vehicle actuator requirements using advanced electromechanical concepts. The approach was restricted to a four-channel redundant configuration. Each channel has independent drive and control electronics, a brushless electric motor with brake, and velocity and position feedback transducers. A differential gearbox sums the output velocities of the motors. Normally, two motors are active and the other two are braked.
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A high speed pointing system
A laser ranging system for use with the Space Shuttle, and applied to a precise determination of the distance between points arrayed on different tectonic plates, i.e., along the San Andreas fault, spaced at distances of 25, 50, and 100 km, is discussed with attention to the orbiting pointing system. The mount carrying the system contains a single elliptical mirror which directs ten laser firings per second (15-18 firings to each target), and receives the light reflected from the target. The mirror and all moving structural parts are constructed of Be. The axes are equipped with 19-bit shaft angle encoders and brushless torque motors. Care is taken to avoid structural resonances, and to ensure a minimum of servo settling time. A Kalman filter is used with the microprocessor system to interpolate low data rate commands to the higher data rates required by the pointing system.
Winston, G. C.↗
Operational Loopwheel Suspension System for Mars Rover Demonstration Model
The loopwheel (or elastic loop) mobility concept, appears to be uniquely qualified to provide a high degree of mobility at low weight and stowage requirements for the next Mars mission now in the early planning stage. Traction elements compatible with sterilization and Mars surface environmental constraints were designed and are compatible with the rover mass, range and stowage requirements of JPL's point design Mars rover. In order to save cost, the loopwheel suspensions for the demonstration model were made of S-glass/epoxy instead of titanium, alloy specified for flight units. The load carrying fiberglass loop core is covered by a rubber tread on the outside. Reinforced rubber gear belts bonded along the inside edges provide positive engagement and transmission drive torques. A 12 Vdc drive motor with a 167:1 gear head is installed in the payload section of the hull. A chain drive transmits the motor power to the rear sprocket in the demonstration model, whereas future flight units would be directly driven by brushless hub motors within each sprocket and independent four-leg height control.
Trautwein, W.↗