DC Torque Motor Research Articles

OPTIMAL SHAPE DESIGN OF A DC TORQUE MOTOR

The optimal design of a small dc torque motor, acting as a position actuator, is considered. The magnetic field is simulated by means of a 2‐D finite element model, taking into account the magnetization curve of iron and permanent magnets. The optimum shape of the motor, exhibiting the minimum cost, subject to a set of behavioural constraints, is found by a stochastic optimizer of lowest order.

Influence of number of poles on the torque of DC brushless motors with auxiliary salient poles

The influence of the number of poles and inside or outside field structure on the torque of brushless DC motors with auxiliary salient poles has been investigated. Nonlinear finite-element-method analysis, associated with the integration of Maxwell's stress tensor, has shown that, for some structures, especially those with outside field, this influence can be significant and that four-pole outside-field motors are the most advantageous.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Model reference adaptive control of a direct-drive DC motor

An adaptive time-optimal position controller for a direct-drive DC motor with a design based on the model reference adaptive approach is presented. The high-acceleration torque of DC motors with permanent magnets permits direct coupling of the load to the motor axis, avoiding the use of a transmission with its inherent disadvantages (such as backlash and friction). However, direct coupling induces a large sensitivity to load variations, so the desired response and the reference model in the adaptive controller are adjusted to the motor capabilities. This is achieved by estimating the load inertia by means of a least-squares method and adjusting the reference model accordingly. The controller is tested on a direct-drive motor, and the results are compared with those obtained with a fixed proportional-integral-derivative controller. >

Development of an Advanced Hybrid Control System for a Cryogenic Spectrometer

NASA's Upper Atmosphere Research Satellite (UARS), to be launched in 1988, will study trace elements in the upper atmosphere. To make measurements, the UARS carries onboard a cryogenically-cooled infrared spectrometer called the Cryogenic Limb Array Etalon Spectrometer (CLAES), which operates at temperatures from 130 K to 13 K. CLAES combines a mUlti-position tilt-scanned Fabry-Perot etalon and filters to provide a high spectral resolution which permits identification of the desired chemical species from spectral radiance measurements. CLAES system requirements include angular positioning of individual etalons within the CLAES optical system, rapid rotation of the etalon holder to the next etalon to be used in measurement sequence, and mi nimi zati on of the thermal energy di ssi pated by the actuator. Since the etalons must operate below 20 K for 18 to 24 months on a limited cryogen supply, all thermal inputs must be minimized, and reliable long-life operation of electromechanical devices is required. A precision, hybrid position control system, capable of both rapid slewing between etalons and precise positioning of an individual etalon during measurement sequences, has been designed and tested at the Lockheed Palo Alto Research Laboratory. The system util izes a unique actuator concept which combines the features of a brushless dc torque motor and a stepper motor. Because the actuator can be used in a direct-drive mode, it eliminates the problems associated with gearboxes and reduces the number of required bearings.

The functional specificity of articulatory control and coordination

Favored interpretations of “compensatory” movements of the lips to unanticipated resistances applied to the jaw during a closing gesture have focused on afferent feedback control [e.g., Folkins and Abbs (1975)] or feedforward, open‐loop control processes [e.g., Abbs and Cole (1982)]. The present experiments sought to identify and analyze, using dynamic perturbation techniques, functional constraints among several articulators when they cooperate to produce n desired utterance. A brushless DC torque motor coupled to the subject's lower teeth via a custom‐made prosthesis was programmed to inject a 500‐g torque load to the jaw for 1.5 s during the vowel‐consonant transition in /baeb/ and /baez/ on 20%–25% of trials. Infrared L.E.D.s were attached to the lips and jaw and monitored using a modified SELSPOT optical tracking system. In experiment 1, increased downward displacement of the upper lip occurred in perturbed conditions for /b/ (p < 0.01) but not for /z/. Experiment 2 replicated this result and also showed, through hooked wire electrode recordings from a tongue muscle, a significant increase in electromyographic activity for /z/ prior to occlusion, but not for /b/. Closure and frication were attained on all trials without any obvious changes in timing. These highly distinctive patterns suggest that the jaw, lips, and tongue may be controlled and coordinated as a single, functional unit (a coordinative structure) that is unique and specific to the intended act. [Work supported by NINCDS and BRSG.]

Satellite-borne limb scanning UV spectrometer for thermospheric remote sensing

A concave grating Wadsworth spectrometer designed to scan the UV limb of the earth was flown on a Defense Department meteorological satellite to obtain measurements of atmospheric emissions in the 85-395-nm wavelength range as a function of height above the solid earth. The instrument field of view was 0.14 x 3.8 degrees corresponding to 6 km in the vertical and 230 km in the horizontal at the limb. The scanning motion was controlled by a momentum compensated dc-torque motor mechanism that panned the line of sight across the limb corresponding to tangent altitudes of 80-480 km. A set of three photon counting detectors, each viewing a separate exit slit, provided simultaneous coverage of the wavelength bands of 85-120 nm (EUV), 110-163 nm (far UV), and 290-395 nm (UV) at a wavelength resolution of 0.4, 0.8, and 1.2 nm, respectively. A separate photometric channel isolated the atmospheric sodium doublet at 589.0-589.6 nm. The grating position and instrument view angle were controlled by digital circuitry operating on hardwired and uplinked command instructions. The operating modes included a variety of scanning and fixed wavelength and view angle operations. A description of the instrument and several examples of the data are presented. These include the dayglow emissions from thermospheric oxygen and nitrogen that form the basis of a thermospheric density determination, auroral enhancements observed in these emissions and in hydrogen Ly-alpha, and nighttime sodium emissions.

EMG responses to rapid pull perturbation applied by a DC torque motor in man : M. Yokochi (Tokyo, Japan) A. Struppler and F. Velho (Munich, W. Germany)

EMG responses to rapid pull perturbation applied by a DC torque motor in man : M. Yokochi (Tokyo, Japan) A. Struppler and F. Velho (Munich, W. Germany)

A Three-Axis Flight Table with DC Torque Motors

The use of flight tables and the present state of the art are described and the specifications for the flight table are derived. Major stress is laid on building a relatively cheap model, that will, nevertheless, satisfy the present requirements. A detailed description of the various alternatives that exist when deciding upon the major components is given along with a discussion on the linear design of the servo loops and stability validations for the expected nonlinearities. A grapho-analytical jump prediction is presented and the wiper backlash problem is analyzed.

Highlights of a Brushless Direct-Drive Solar Array Control System Design

This paper summarizes a drive system design for controlling the position and rate of solar power arrays on orbiting spacecraft. There are no gears or sliding contact elements used anywhere in the system and only low-speed bearings are needed. Such mechanization is particularly well suited to solid lubrication techniques, and wear rates are very low, so that the drive system can operate directly in the space environment for long periods of time. Three major components were developed for implementation of this design concept. They are: 1) a brushless dc torque motor; 2) a rotary power transformer; and 3) an offset-tooth shaft position and rate sensor. These components are combined in a hybrid system configuration in which the signal processing and logic functions are performed by digital and linear integrated circuits. A root contour and describing function analysis, confirmed by experimentation, shows that several modes of limit cycle generation can occur in the vicinity of null. Compensation circuits are given that inhibit or suppress limit cycling and provide controlled electronic damping of the system. The system offers relatively high stiffness and can be operated at indefinitely low angular rates with minimum power consumption.

A pulsatile roller pump for cardiac bypass.

This short communication describes a cardiac bypass pump which produces a pulsatile flow. By driving a roller pump with a dc torque motor, it has been possible to provide electronic control of pulse rate and stroke volume. Flow and pressure recordings in dogs undergoing left-heart bypass are nearly physiological.

New Reverberation Chamber, Rotating Vane, and Microphone System Improve Discrete Frequency Measurements

A laboratory designed to help engineers produce quiet motors for automotive, household-appliance, and industrial-motor applications includes reverberation chambers of 16 000 cu ft, 8000 cu ft, and a semianechoic half-space. Numerous room proportions were investigated, and sizes adjusted to provide uniform modal spacing. In each reverberant room, ceilings and two walls were skewed, two tilted, to moderate the strength of axial and tangent modes and eliminate flutter. A rotating diffuser combining elliptical and conical sections for small air disturbance, a surface density of 1.8 lb/sq ft, projected dimensions of 14 ft × 15 ft or more from every view, and integral dc torque motor drive to 12 rpm without speed reduction was provided for the largest chamber. Variations in vane, source, and microphone locations and in acoustical absorption were investigated as were rate of vane rotation, of microphone distribution and sampling rate, and the effect of vane rotation upon the load seen by the source. Response is relatively good to 100 Hz, fair to 89 Hz, usable to 55 Hz.