Showing papers on "Rotational speed published in 1995"

Methods of transporting fluids within an analytical rotor

Abstract: The present invention provides an analytical rotor which holds a fluid in a chamber, typically to allow mixing with a reagent, and transfers the fluid to a receiving chamber in the rotor. The rotor comprises a holding chamber having an single exit duct and a receiving chamber connected to the holding chamber through the exit duct. The exit duct prevents flow at a first rotational speed and allows flow at a second, higher rotational speed. The exit duct may include a capillary passage in which capillary forces prevent flow until the rotational speed is increased. Alternatively, the exit duct may include a siphon.

Disk drive power management system and method

Abstract: A system and method for optimizing power consumption by a disk drive unit. The system and method monitor and analyze historical use data and calculate a predicted inactivity duration. The predicted inactivity duration is used to power-down the rotational speed of the drive to the first of one or more intermediate rotational speeds. Continued inactivity will result in further speed reduction until the drive is ultimately powered off. The drive increases rotational speed on demand.

Nonlinear speed observer for high-performance induction motor control

Abstract: In this paper, we consider the problem of estimating the angular velocity of an induction motor using encoder measurements. Two methods are compared. In the first method, the speed is found by calculating the backward difference of the position measurement and low-pass filtering the result. In the second method, the velocity is estimated using a nonlinear observer constructed using the known dynamic model of the induction motor. The performance of the two methods is evaluated in the context of their use for velocity feedback in a high-performance field-oriented control law. Experimental results demonstrate that the speed observer leads to a smoother operation of the motor in closed-loop. With the estimator based on differentiation, either the delay imposed by the low-pass filter is too large to maintain high bandwidth feedback, or the fluctuations in the estimated speed are so large that much more energy ends up being dissipated to achieve the same control task. >

Centrifugal Pump Performance During Transient Operation

Abstract: The effect of transient operation on the hydrodynamic performance of a centrifugal pump impeller was investigated experimentally. All experiments were conducted in the Naval Undersea Warfare Centers Impeller Test Facility (ITF), which was designed and built for transient and steady-state operation impeller research. TheITF provides transient operation through simultaneous control of both impeller rotational speed and flow rate over time. The impeller was accelerated from rest with peak angular accelerations up to 720 radians/s 2 and inlet flow mean accelerations up to 1.7 g, reaching a peak rotational speed of 2400 rpm and a flow rate of 416 l/s. The impeller was then decelerated to rest. Results showed substantial transient effects in overall impeller performance and demonstrated that the quasi-steady assumptions commonly used for the design of impellers that operate under high transient (accelerating or decelerating) conditions are not valid

Inertial drives for micro- and nanorobots: two novel mechanisms

Abstract: In micro or nanorobotics, high precision movement in two or more degrees of freedom is one of the main problems. Firstly, the positional precision has to be increased (< 10 nm) as the object sizes decrease. On the other hand, the workspace has to have macroscopic dimensions (1 cm3) to give high maneuverability to the system and to allow suitable handling at the micro/macro-world interface. As basic driving mechanisms for the ETHZ Nanorobot Project, two new piezoelectric devices have been developed. `Abalone' is a 3-dof system that relies on the impact drive principle. The 38 mm X 33 mm X 9 mm slider can be moved to each position and orientation in a horizontal plane within a theoretically infinite workspace. In the stepping mode it achieves a speed of 1 mm/s in translation and 7 deg/s in rotation. Within the actuator's local range of 6 micrometers fine positioning is possible with a resolution better than 10 nm. `NanoCrab' is a bearingless rotational micromotor relying on the stick-slip effect. This 10 mm X 7 mm X 7 mm motor has the advantage of a relatively high torque at low rotational speed and an excellent runout. While the maximum velocity is 60 rpm, it reaches its highest torque of 0.3 mNm at 2 rpm. Another benefit is the powerless holding torque of 0.9 mNm. With a typical step of 0.1 mrad and a local resolution 3 orders of magnitude better than the step angle, NanoCrab can be very precisely adjusted. Design and measurements of the characteristics of these two mechanisms will be presented and compared with the theoretical analysis of inertial drives presented in a companion paper. Finally their integration into the Nanorobot system will be discussed.© (1995) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Method of controlling speed change of hydraulic drive device for vehicle and speed change device

Abstract: The present invention relates to a method of controlling a speed change of a hydraulic driving apparatus for a vehicle and to a speed changing device which provide excellent traveling efficiency and controllability. To this end, the method of controlling a speed change comprises discriminating between at least a powering travel and a braking travel from an accelerating amount (θ) and rotational speed of a hydraulic motor (50) for controlling. At the time of the powering travel, a directional control valve (21) can be fully opened in response to the rotational speed (ωout) of the hydraulic motor (50) and the accelerating amount (θ). In addition, the speed changing device comprises an accelerating amount detection sensor (61a), a motor rotational speed sensor (52) for detecting a vehicle speed (V), and a control device (60) for discriminating, from the accelerating amount (θ) and the vehicle speed (V), between the powering travel and the braking travel for providing a control.

Method of fabricating dispersion compensation fiber

Abstract: In a method of fabricating DCF, the fiber is drawn while rotating said optical fiber preform, wherein a rotational speed of said optical fiber preform is 10 to 1,000 rpm, a drawing speed is 50 to 1,000 m/min, and a drawing tension is 2.4 to 13 kg/mm2.

Active feedback loop to control body pitch in STOL/VTOL free wing aircraft

Abstract: An aircraft control system for controlling an aircraft, particularly a free wing aircraft in low speed or hover regimes. An air speed sensor measures air speed of the aircraft and outputs an air speed signal to a control processor which processes the air speed signal with a speed control input signal. A control actuator actuates an aircraft control surface in response to the control surface control signal. The air speed sensor may include a shaft mounted impeller located in an airstream of the aircraft. A rotational speed sensor, coupled to the impeller, measures a rotational speed of the impeller and outputs a rotational speed signal as the air speed signal. In an alternative embodiment, the air speed sensor may include a vane located in an airstream of the aircraft and deflected in response to air flow in the airstream. In another embodiment, the speed sensor may include an angular position sensor which measures an angle between a free wing and the aircraft fuselage and outputs an angle measurement signal as the air speed signal. The aircraft control surface may comprises a control boom pivotally attached to a fuselage of the aircraft of a trim tab pivotally attached to a fuselage of the aircraft.

Heat pump type air conditioner and method for controlling a heat pump type air conditioner

Abstract: A heat pump type air conditioner having a refrigeration circuit including a variable speed compressor, a four-way valve, an indoor heat exchanger, an expansion device and an outdoor heat exchanger, and capable of operating in a cooling mode to cool a room and a heating mode to heat the room. The compressor speed is set in accordance with air conditioning load, such as the temperature difference between a setting room temperature and the actual room air temperature and the operation mode. An outdoor fan blows air through the outdoor heat exchanger which selectably rotates at a high speed or a low speed. The rotational speed of the outdoor fan is selected based on the operation mode, a cooling mode reference compressor rotational speed value, a heating mode reference compressor rotational speed value and the set compressor rotational speed. The cooling mode reference compressor rotational speed value is smaller than the heating mode reference compressor rotational speed value.

Aerodynamic characteristics of low-drag bicycle wheels

Abstract: A number of modern “aerodynamic” bicycle wheels were tested at full scale speeds in a windtunnel. The effects of wheel geometry, rotational speed and cross winds on drag force, side force and yawing moment were investigated. Compared with a conventional spoked wheel, all the “aerodynamic” wheels were found to give similar improvements in drag of approximately 25%. In cross wind conditions, aerodynamic characteristics were strongly dependent on wheel geometry, but essentially independent of wheel rotational speed.

System for detecting and accommodating gas turbine engine fan damage

Abstract: Foreign object ingestion damage detection and accommodation system for a gas turbine engine system having a gas turbine engine with multiple rotating members, such as a twin spool configuration. System includes speed sensors for sensing the rotational speed of at least two rotating members. Sensors are coupled to a controller which detects damage by comparing the sensed speed of the second rotational member to an expected speed. Expected speed is determined from the sensed speed of the first rotating member using a known characteristic relationship between the the first and second rotating member speeds for the given gas turbine engine design. Thrust loss accommodation is triggered when damage is detected. Accommodation mode provides a synthesized primary thrust control feedback signal in lieu of the sensed signal for a damaged rotational member. Synthesized signal is derived from the sensed speed for the undamaged rotational member.

On the Instability Mechanisms of a Disk Rotating Close to a Rigid Surface

Abstract: The instability mechanisms of a rotating disk, coupled to a rigid surface through a viscous fluid film at the interface, are investigated analytically. The fluid in the film is driven circumferentially by the viscous shear, and it flows outwards radially under centrifugal forces. The circumferential flow component creates an equivalent viscous damping rotating at one half the disk rotation speed. This film damping dissipates all backward traveling waves where the undamped wave speeds are greater than one half the disk rotation speed. The radial flow component creates a nonsymmetric stiffness in the disk-film system that energizes any wave mode at rotation speeds above its flutter speed. Instabilities in the disk-film system are of two types. A rotating damping instability is caused by the rotating film damping at rotation speeds above a critical value that is less than the flutter speed. A combination instability is caused by the combined effect of the film stiffness and damping at rotation speeds above a threshold that is greater than the flutter speed. The maximum rotation speed of stable disk vibration is bounded above by the lowest onset speed of rotating damping instability. This speed limit is predicted for two wall enclosure designs. The maximum stable rotation speed of a 5.25-inch diameter flexible, memory disk, separated from a rigid surface by a viscous air film, is shown to be more than 15 times greater than the maximum speed of the disk without the air film.

Variable speed induction generator-motor with controllable excitation frequency

Abstract: A variable velocity apparatus includes a wound-rotor induction machine having a primary winding connected to a power system having a power system frequency, a secondary winding excited by an alternating current (AC), a generator-motor shaft, and a load united with the generator-motor shaft. The apparatus includes a frequency detection element for detecting a change in the power system frequency, and a controller for changing a rotational speed of the induction machine based on the detected change in the power system frequency. The change in the rotational speed is made substantially equivalent to the detected change in the power system frequency, so as to maintain a slip frequency of the induction machine essentially constant when the power system frequency changes.

Optical disk reproducing apparatus for controlling the rotational speed of a spindle motor between a CLV control and a CAV control

Abstract: An optical disk reproducing apparatus uses a spindle motor having a low torque to reduced power consumption and manufacturing cost while maintaining a low error rate for reproduced data. The spindle motor is rotated at a constant rotational speed under a CAV control when a pick-up is moved. The rotational speed of the spindle motor is switched to a reference linear speed under a CLV control when a reproducing operation is performed. The reference linear speed is established for each of the zones of a recording area of an optical disk. The reference linear speed is determined by generating a zone clock set for each of the zones. A frequency error signal is generated by comparing the zone clock with the reproduction data so as to maintain the spindle motor at the reference linear speed determined by the zone clock.

Inverter control apparatus

Abstract: An inverter control apparatus for controlling a command frequency and a command voltage which are supplied to an inverter which then supplies AC power of a desired frequency, accordingly, to an induction motor. The inverter control apparatus receives a requested rotational speed of the motor and an actual rotational speed of the motor is obtained by detecting a frequency of a fluctuation component of a drive current supplied from the inverter to the induction motor. The difference between the requested rotational speed and the actual rotational speed represents a slip amount, which is added to the requested rotational speed to produce a command frequency. The command voltage is set to a voltage acquired when the monitored drive current is at a minimum value. Thus, the inverter control apparatus is able to maintain power consumption at the lowest possible level in response to changes in the operating environment without requiring a motor constant input or a motor speed detector, while compensating the slip ratio of the induction motor to maintain the motor speed at a target level.

Dynamic digital tracking filter

Abstract: A system for measuring the magnitude component corresponding to the once-per-revolution frequency or a multiple thereof of the vibration signal generated by a body rotating at a non-uniform rate. The output of a sensor detecting the acceleration of the vibration motion of the rotating body is decomposed into its frequency components. Simultaneously, the information contained in the output of a tachometer sensor for detecting the rotational speed of the rotating body is used to determine the variation of the rotational speed during the measurement interval. The speed variation information is selectively combined with the frequency components of the acceleration spectrum to yield the magnitude result that would be measured if the rotating body had a constant rotational speed. This method yields vibration information in select frequency bands that is corrected for the non-uniform rate of rotation of the body.

Propulsion control apparatus and method for a paver

Abstract: An apparatus is disclosed for controlling the propulsion and steering of a machine. The machine includes a hydrostatic system that drives a pair of ground engaging traction devices. An electronic controller receives operator signals indicative of a desired travel speed and direction, and determines a desired rotational speed of the ground engaging traction devices. The electronic controller produces command signals indicative of the determined speeds to regulate the speed of the ground engaging traction devices to the desired speed.

The response of a centrifugal pump to fluctuating rotational speed

Abstract: A theoretical and experimental study has been made on the dynamic characteristics of a centrifugal pump subject to sinusoidal changes in rotational speed. Time-dependent rotational speed, flow-rate, and total pressure rise are measured for a variety of amplitude and frequency of the fluctuating rotational speed. Measured flow-rate as well as total pressure rise is compared with the quasi-steady ones. Unsteady flow analysis is made for a two-dimensional circular cascade by use of the singularity method. The calculated frequency characteristics are compared with the corresponding experimental ones. The deviation of unsteady characteristics from quasi-steady ones is evident, and the numerical results agree qualitatively with the measured ones. It was found that with the increased frequency of rotational speed fluctuations the dynamic characteristics deviate remarkably from quasi-steady ones. Moreover, a criterion for the assumption of quasi-steady change is presented.

Apparatus and method for controlling an air conditioner

Abstract: A method and apparatus for controlling an air conditioner having a variable speed compressor to circulate a refrigerant in a refrigerating circuit. The control apparatus and method generates a rotational speed pattern which can be directly changed by a predetermined value through a controller operable by the user. The compressor rotational speed is also based on the rotational speed used in a previous operation of the compressor to take into account the time lag occurring between the time the air conditioner is operated and the time the conditioned air is actually circulated in the room. Basing compressor speed on previous operations of the compressor minimizes large fluctuations in room temperature due to inaccuracies in temperature detection.

Disc drive unit

Abstract: A disc driving apparatus for driving a magneto-optical disc recording medium (202) accommodated in a disc cassette (250) is proposed, said apparatus comprising a magnetic head (80) for applying a magnetic field to a magneto-optical disc, a magnetic-head moving mechanism (380) for moving said magnetic head between a loading position and an unloading position, an eject mechanism (360) for ejecting said disc cassette and a motor. The disc driving apparatus further comprises transmission means for transmitting a rotational force of said motor to said magnetic-head moving mechanism by rotation of said motor in its one rotational direction and for transmitting the rotational force of said motor to said eject mechanism by rotation of said motor in its other rotational direction and control means for controlling said motor so that a rotational speed of said motor in said other rotational direction is faster than rotational speed of said motor in said one rotational direction.

On the Global Stability of Magnetized Accretion Disks. II. Vertical and Azimuthal Magnetic Fields

Abstract: We investigate the global stability of a differentially rotating fluid shell threaded by vertical and azimuthal magnetic fields to linear, axisymmetric perturbations. This system, which models a thick accretion disk in the vicinity of its midplane, is susceptible to the Velikhov-Chandrasekhar (VC) instability in the absence of the azimuthal field. In most cases, the azimuthal field tends to stabilize the VC instability, although strong fields (Alfv\'en speed of order the characteristic rotational speed in our incompressible model) are required for complete stabilization. Stability diagrams are constructed, indicating critical values of the two fields for instability. We find an additional strong field instability that arises when the azimuthal Alfv\'en speed exceeds the characteristic rotational speed. This instability, in the case of a freely bounded configuration, has certain similarities to the sausage instability for interpenetrating fields in plasma physics, and may be important for very massive disks or filamentary molecular clouds. An application to the L1641 region in Orion A is briefly discussed. Finally, we find that the effect of a radially varying vertical field (without an azimuthal field) is mainly stabilizing.

Wave rotor charging process - Effects of gradual opening and rotation

Abstract: The wave rotor charging process under conditions of gradual opening accompanied by passage rotation is numerically simulated Insights into the response of the interface and kinematics of the flowfield to various opening times are given Since the opening time is inversely proportional to the rotational speed of the rotor, effects of passage rotation such as centripetal and Coriolis accelerations are intrinsically coupled to the gradual opening process Certain three-dimensional features associated with the charging process as a result of centripetal and Coriolis accelerations are illustrated It is shown that the interface between driver and driven gas acquires a three-dimensio nal distortion depending on the rotational speed and opening time Nomenclature a = speed of sound B = dimensionless ratio of time scales E = total energy per unit mass e = unit vector h,R = rothalpy L = passage length Mo, Mn = wheel Mach number based on tip radius and a reference speed of sound p = pressure RH = hub radius RT = tip radius RU = rotation parameter T = temperature t = time w = relative velocity vector y = ratio of specific heats 6 = azimuthal coordinate in a stationary reference frame 6' = azimuthal coordinate on the rotating passage p = density T = reference time scale 4> = passage sector angle ft = rotational speed Subscripts

On the Global Stability of Magnetized Accretion Disks. II. Vertical and Azimuthal Magnetic Fields

Abstract: We investigate the global stability of a differentially rotating fluid shell threaded by vertical and azimuthal magnetic fields to linear, axisymmetric perturbations. This system, which models a thick accretion disk in the vicinity of its midplane, is susceptible to the Velikhov-Chandrasekhar (VC) instability in the absence of the azimuthal field. In most cases, the azimuthal field tends to stabilize the VC instability, although strong fields (Alfv\'en speed of order the characteristic rotational speed in our incompressible model) are required for complete stabilization. Stability diagrams are constructed, indicating critical values of the two fields for instability. We find an additional strong field instability that arises when the azimuthal Alfv\'en speed exceeds the characteristic rotational speed. This instability, in the case of a freely bounded configuration, has certain similarities to the sausage instability for interpenetrating fields in plasma physics, and may be important for very massive disks or filamentary molecular clouds. An application to the L1641 region in Orion A is briefly discussed. Finally, we find that the effect of a radially varying vertical field (without an azimuthal field) is mainly stabilizing.

Motor assisted bicycle

Abstract: PURPOSE: To realize the appropriate power assist irrespective of the position of a transmission by directly calculating the rotational speed by the signal from a detector incorporated in a wheel to realize the control. CONSTITUTION: When a pedal is stepped in, a torque sensor incorporated in an electric driving device 4 detects the load, and transmits the signal to a micro computer incorporated in a control circuit 3. The micro computer calculates the torque required for the pedal load by the signal and the bicycle speed signal transmitted from a generator 1 to operate the electric driving device 4. The generator 1 incorporated in a front wheel generates the AC voltage corresponding to the rotational speed of the wheel. The voltage is pulsed, and the pulse is counted by the micro computer, and the actual speed of the bicycle is obtained based on the wheel size of the bicycle, and the electric driving device 4 is controlled so as to gradually reduce the assist ratio according to the actual speed.

Speed change control apparatus for an automatic transmission

Abstract: A speed change control apparatus for an automatic transmission includes a transmission control unit for controlling gear-changing. The control unit discriminates a fluid temperature/rotational speed zone based on the hydraulic fluid temperature and the engine speed at the start of gear-changing, and detects a time period from the end of dead-stroke elimination of an engagement-side hydraulic clutch to the start of actual gear-changing. In the case that a condition for executing learning correction is satisfied and if a time period from the end of the dead-stroke elimination to the start of the actual gear-changing is longer than an upper limit, the control unit increases a learning-correction time with which a dead-stroke-elimination time for the discriminated temperature/speed zone is calculated. The learning-correction time is decreased if such a time period is shorter than a lower limit. By carrying out the learning correction for various temperature/speed, occurrences of degraded shift response and shift shocks resulting from the presence of individual difference of the automatic transmission and an increase or decrease in the engine speed or fluid temperature can be prevented.

System for controlling disk drive by varying disk rotation speed when buffered data is above high or below low threshold for predetermined damping period

Abstract: A disk drive motor control system which dynamically varies the speed of the motor in accordance with the desired data transfer rate is provided This is accomplished by monitoring the transfer rate and lowering the speed when the transfer rate decreases and then raising the speed when the transfer rate increases Hysteresis is preferably built-in so that rapid oscillations between the two speeds do not occur

Method and system for controlling automatic transmission

Abstract: An automatic transmission control system is capable of quickly and accurately judging the normal state and faulty state of an input shaft rotation speed sensor and/or an output shaft rotation speed sensor. The system includes an input shaft rotation speed sensor condition judging device for judging whether an input shaft rotation speed sensor detecting a rotation speed NI of an input shaft of the automatic transmission is in a normal or faulty state, an output shaft rotation speed sensor condition judging device for judging whether an output shaft rotation speed sensor detecting a rotation speed No of an output shaft of the automatic transmission is in a normal or faulty state, a multiplying means for multiplying the rotation speed No of the output shaft with a current transmission gear ratio, and comparing and judging means for judging whether the multiplied value is coincident with the rotation speed NI of the input shaft. On the basis of those judgements, the output shaft rotation speed sensor is judged whether it is in the normal state or not by the output shaft rotation speed sensor condition judging device.

Flow in curved channels with a low negative rotation speed.

Abstract: Experiments on visualization of stabilizing and destabilizing flow in channels with curvature and rotation are described. Two test sections have been used, i.e., the rectangular channels with aspect ratios of 1 and 10, respectively. The results show the end view of flows in the region with a low negative rotation speed. In addition, a generalized Rayleigh criterion is formulated about the primary instability of flows in rotating curved channels to help in understanding the experimental results.