Showing papers on "Rotational speed published in 1996"

Method for optimizing the rotational speed of cooling fans

Abstract: A method for controlling cooling fans for variable electrical loads. A cooller monitors cooling fan output, ambient temperature and the electrical load. The controller then matches the fan speed and resulting cooling to the existing electrical load and ambient temperature. As a consequence, fan speed is maintained at a minimum necessary to sustain appropriate cooling levels. This minimizes the generation of structureborne and airflow noise.

Adaptive compensation for hard disc drive spindle motor manufacturing tolerances

Abstract: Apparatus and method for adaptively compensating for variations in rotational speed of a back emf commutated spindle motor in a hard disc drive. After the motor achieves nominal operating speed, the hard disc drive enters a learn mode during which systematic variations in operational speed of the spindle motor are characterized over a plurality of rotations, including characterization of the average timing of zero crossing signals with respect to reference frequency periods and characterization of the average time between successive zero crossing signals. The hard disc drive next enters a compensation mode, during which modified speed control timing signals and modified commutation timing signals are outputted in response to the average timing characterized during the learn mode.

Performance of a High-Solidity Wells Turbine for an OWC Wave Power Plant

Abstract: The paper describes an experimental investigation, and presents the results of the aerodynamic performance of a high-solidity Wells turbine for a wave power plant. A monoplane turbine of 0.6 m rotor diameter with guide vanes was built and tested. The tests were conducted in unidirectional steady airflow. Measurements taken include flow rate, pressure drop, torque, and rotational speed, as well as velocity and pressure distributions. Experimental results show that the presence of guide vanes can provide a remarkable increase in turbine efficiency.

Effects of rotating inlet distortion on multistage compressor stability

Abstract: In multispool engines, rotating stall in an upstream compressor will impose a rotating distortion on the downstream compressor, thereby affecting its stability margin. In this paper experiments are described in which this effect was simulated by a rotating screen upstream of several multistage low-speed compressors. The measurements are complemented by, and compared with, a theoretical model of multistage compressor response to speed and direction of rotation of an inlet distortion. For corotating distortions (i.e., distortions rotating in the same direction as rotor rotation), experiments show that the compressors exhibited significant loss in stability margin and that they could be divided into two groups according to their response. The first group exhibited a single peak in stall margin degradation when the distortion speed corresponded to roughly 50 percent of rotor speed. The second group showed two peaks in stall margin degradation corresponding to distortion speeds of approximately 25-35 percent and 70-75 percent of rotor speed. These new results demonstrate that multistage compressors can have more than a single resonant response. Detailed measurements suggest that the two types of behavior are linked to differences between the stall inception processes observed for the two groups of compressors and that a direct connection thus exists between the observed forced response and the unsteady flow phenomena at stall onset. For counterrotational distortions, all the compressors tested showed minimal loss of stability margin. The results imply that counterrotation of the fan and core compressor, or LP and HP compressors, could be a worthwhile design choice. Calculations based on the two-dimensional theoretical model show excellent agreement for the compressors, which had a single peak for stall margin degradation. We take this first-of-a-kind comparison as showing that the model, though simplified, captures the essential fluid dynamic features of the phenomena. Agreement is not good for compressors that had two peaks in the curve of stall margin shift versus distortion rotation speed. The discrepancy is attributed to the three-dimensional and short length scale nature of the stall inception process in these machines; this includes phenomena that have not yet been addressed in any model.

Encoder device for a rotational speed sensor and rolling-contact bearing equipped with such a device

Abstract: Encoder device for a rotational speed sensor of a rotating member of the bearing (1) mounted on a non-rotating member of the said bearing (1), of the type comprising a sensor (7) which is secured to an element that is fixed relative to the non-rotating member and in front of which an element forming a rotor moves in rotation with a small air gap, which element is equipped with an encoder (12) in the form of a multipole magnetized ring, capable of producing in the sensor a periodic signal of frequency proportional to the speed of rotation of the rotor element. The encoder (12) is fixed to an internal face of a rigid protection and support element (13) made of nonmagnetic metallic material, a corresponding external face of the protection element (13) moving in rotation in front of the sensor (7).

Apparatus for optimizing the rotational speed of cooling fans

Abstract: Apparatus for controlling cooling fans for variable electrical loads. A controller monitors cooling fan output, ambient temperature and the electrical load. The controller then matches the fan speed and resulting cooling to the existing electrical load and ambient temperature. As a consequence, fan speed is maintained at a minimum necessary to sustain appropriate cooling levels. This minimizes the generation of structureborne and airflow noise.

Method and apparatus for load balancing among multiple compressors

Abstract: Balancing the load between compressors is not trivial. An approach is disclosed to balance loads for compression systems which have the characteristic that the surge parameters, S, change in the same direction with rotational speed during the balancing process. Load balancing control involves equalizing the pressure ratio, rotational speed, or power (or functions of these) when the compressors are operating far from surge. Then, as surge is approached, all compressors are controlled, such that they arrive at their surge control lines simultaneously.

Centrifugal blood pump driver apparatus

Abstract: A centrifugal blood pump driver comprises a motor housing and the housing contains a motor for rotationally driving the centrifugal blood pump and a controller operatively associated with the motor for controlling the rotational speed of the motor; a speed selector for generating a selected speed signal signifying a selected rotational speed for the motor; sensors operatively associated with the motor or controller for sensing the rotational speed of the motor and outputting a monitor signal signifying such rotational speed; program memory for storage of a program of microprocessor readable instructions; a microprocessor under program control, in electrical connection with the controller, the speed selector, the sensor and the program memory, for receiving the selected speed signal and generating a speed control signal to the controller signifying the selected speed for the controller, and for receiving the monitor signal and outputting a display signal; a display in electrical communication with the microprocessor and responsive to the display signal for displaying information; motor housing circuitry for providing electrical communication among the controller, the speed selector, the sensor, the program memory, the microprocessor, and the display; and electrically conductive cable connected to the motor housing circuitry for transmitting electrical DC power to the motor housing circuitry from an external power source.

Effects of slots on the lateral vibration of a circular saw blade

Abstract: In the majority of cases, wood is cut at a high feed rate and high rotational speed by circular saw blades with tungsten carbide tips brazed on the periphery of metal circular plates. Slots are made at several places from the periphery towards the center of a saw blade to prevent lateral vibration, both in idling and cutting, and to prevent a drop in critical rotational speed caused by heat expansion on the blade periphery during the cutting operation. In this paper, variations of lateral vibration mode, natural frequency and critical rotational speed of a slotted circular saw blade are investigated experimentally and by numerical calculations. The lateral deflection of a circular saw blade at the critical rotational speed and at the rotational speed near it is examined by a timber-cutting experiment.

Numerical control apparatus

Abstract: A numerical control apparatus can process a workpiece at high speed and high precision while suppressing tool abrasion by maintaining optimum cutting conditions determined by a combination of spindle rotational speed and tool feed speed. A spindle rotational speed control section changes the speed of the spindle according to a tool feed speed obtained by a tool feed speed deciding section based on the shape of the tool moving path commanded by a machining program. Alternatively, the spindle rotational speed is changed by a spindle rotational speed control section based on a change in the contact position between the tool and the workpiece to be cut in the tool axial movement direction. Further, the spindle rotational speed may be changed by the spindle rotational speed control section based on the tool feed speed including tool axial movement direction data obtained by a feed speed deciding section based on the shape of the tool moving path.

Tire pneumatic pressure estimating apparatus

Abstract: To provide a tire pressure estimating system which is capable of estimating tire pressure based on a signal representing the rotational speed of a vehicle wheel via a small amount of processing by using low-capacity memory, a wheel speed sensor is provided for each wheel of a vehicle. A pulse signal output by the wheel speed sensor is supplied to a signal processor. In the signal processor, the rotational speed of each vehicle wheel is found from the pulse signal. The signal processor adopts a second-order linear prediction model for the rotational speed of the vehicle wheel and vibration of the tire using parameters identified from values of the rotational speed. A resonance frequency is then found from the identified parameters. Finally, the tire pressure is estimated from a linear relationship between the pressure and the resonance frequency.

Miniature centrifugal lighting assembly

Abstract: A miniaturized lighting apparatus for a rotating object includes a light-emitting diode (LED), a centrifugal switch, a tiny 3 volt power source, and electrical conduits. The switch is configured to provide power to the LED only upon application of a specific centrifugal force. As applied to an in-line roller skate wheel, the switch and LED may be sealed within the wheel, and the batteries never need replacement because the battery life exceeds the expected wheel life. An in-line skate wheel incorporating the lighting apparatus within it is activated to light the wheel at a predetermined centrifugal force equivalent to a given rotational speed of the wheel, such as 80 rpm. As applied to a reflector light for a bicycle wheel, the light draws power from the battery(ies) only while the wheel is turning at a minimum predetermined rotational speed such as 20 rpm. As applied to a rotatable flying disc, lighting apparatus are mounted on opposite sides of the disc, near the disc periphery. The switch is constructed to actuate the LED at a low rotational speed, and the disc itself is constructed of a phosphorescent material with persistent afterglow. Alternatively, a time delay may be incorporated into the lighting circuit to provide a delayed shut-off of current to the LED.

Process for the early recognition of hydroplaning of a vehicle tire on a wet road

Abstract: The invention provides a process for the advance recognition of the hydroplaning of a vehicle tire on a wet road, in which the rotational speed of the wheel carrying the tire is sensed by a rotational speed sensor and the frequency spectrum of the rotational wheel speed is evaluated. According to the invention, in the frequency range above 20 Hz, the natural resonance behavior of the rotational tire vibrations is evaluated continuously, and a conclusion on hydroplaning of the tire is drawn from detuning of the rotatory natural frequencies.

Method for determining rotational speed from machine vibration data

Abstract: A method of determining the rotational speed of a rotating shaft from machine vibration data. The vibration produced by the shaft is sensed to produce a test vibration signal at an unknown rotational speed of the shaft, which test vibrational signal is converted to a test frequency spectrum. A reference frequency spectrum, corresponding to a known rotational speed of the shaft, is provided, and a stretch factor is determined. The stretch factor provides optimum correlation between the test frequency spectrum and the reference frequency spectrum. The unknown speed of the rotating shaft is calculated using the known speed of the reference frequency spectrum and the stretch factor.

Apparatus for determining angular position and rotational speed using a rotating magnet and a directional magnetometer

Abstract: In a preferred embodiment, an apparatus for detecting the angular position, rotational speed, and/or acceleration of a rotatable member, including: an annular magnetic source circumferentially disposed on the rotatable member and rotatable therewith; a directional magnetometer having a toroidal core, disposed at a location in proximity to the magnetic source, with the rotatable member passing through the toroidal core, the directional magnetometer being oriented so as to detect the amplitude and/or change of amplitude of only a tangential magnetic flux field component of the magnetic source, and to provide outputs indicative thereof; and apparatus to receive the outputs and to determine therefrom the angular position, rotational speed, and/or acceleration of the rotatable member.

Process for dynamically adjusting the power for a vehicle having a fuel cell

Abstract: The invention provides a process for dynamically adjusting the power of an electric driving unit of a vehicle which is supplied with electric energy by a fuel cell, the power of the fuel cell or the provided fuel cell current being controlled by means of the supplied air volume flow. The air volume flow is adjusted by the rotational speed of a compressor, a desired rotational speed value being predetermined for the compressor based on an accelerator pedal demand. Simultaneously, based on the measured air flow volume, the actually available fuel cell current is determined and therefrom a corrected accelerator pedal demand is determined. During the starting operation, the accelerator pedal demand is supplied directly to the driving unit, whereas, at higher rotational speeds, it is limited by the corrected accelerator pedal demand.

On the azimuthal mode structure of rotating blade flow instabilities in axial turbomachines

Abstract: An experimental investigation is described to study the azimuthal structure of the rotating blade flow instability which was recently observed in axial turbomachines. An azimutnal mode analysis is applied to the unsteady pressures at the casing wall immediately upstream of the inlet plane of the rotor. The rotating instability is characterized as an unstable source with a narrow-band frequency and unsteady rotational speed. It is shown that there is only one dominant mode at each peak frequency of the rotating instability components, and subsequent modes are continuously numbered. The peaks due to the rotating instability modes are not tonal in nature but spread over a narrow band. The frequency variation observed can be explained by either a variation of the source frequency, a variation of the angular velocity of the modes, or a combination of both. Similar to rotating stall, which is a frozen flow pattern, the rotating instability source rotates in the same direction as the rotor at about half the shaft speed. The rotating instability components comprise azimuthal modes of much higher order than rotating stall. At highly throttled operation, both flow phenomena are observed at the same time. The mode orders of rotating instability and rotating stall are not harmonically related. In agreement with earlier studies, the tip clearance noise of axial flow machines is found to be generated by the interaction between the rotating instability pattern and the rotor blades.

Optical disk motor servo and method for closed loop speed control

Abstract: An optical disk drive in which changes in rotational speed are achieved under closed loop control, avoiding significant undershoots or overshoots in speed, increasing access time and reducing power. The speed control is suitable for use in a CLV system, in an CAV/CLV scheme, or in any system in which the speed of the disk must be changed at various times. Feedback from the motor, rather than data read from the disk, determines and controls motor speed during all search operations. The disk motor servo determines the desired motor speed for a target track through a speed profile table. The speed profile table can be designed to accommodate a combination of CAV mode and CLV mode of operation such that the disk drive system can run at the maximum data transfer rate permitted by the data processing electronics, or to minimize power consumption. Through closed loop control, the system ensures that the speed of the motor is quickly and accurately changed to the desired speed, typically by the time the optical pickup reaches a target track during a search operation. The closed loop control also allows the disk drive system to be designed for a lower tolerance level and still achieve jitter-free control. Thus the data rate can be increased due to the lower tolerance required. The access time is minimized because the CD-DSP can begin retrieving data as soon as the target track is reached, since the optical disk will generally already at the desired speed.

Low flow-rate pump

Abstract: A relatively power efficient, low flow-rate pump comprises an integral rotor-impeller on a hollow shaft which forms the rotational axis. The rotor-impeller is permanently magnetized with alternating poles about its periphery faces and at least two channels extend through the rotor-impeller from the interior of the hollow shaft to the periphery of the rotor-impeller. The diameter of the rotor-impeller is in the range of from about 5mm to about 30mm and the operating rotational speed of the rotor-impeller is from about 10,000 RPM to about 50,000 RPM.

Controller for turboal ternator

Abstract: A speed controller for a generator having a rotor includes a speed control input port for receiving a speed command signal, a proportional gain stage electrically connected to said speed control input port for amplifying the speed command signal to create an amplified signal, a turbine speed integrator operatively connected to the speed control input port for integrating the speed control signal to create an integrated signal, an adder for adding the amplified signal and the integrated signal to create a torque signal, a speed estimator for estimating the rotational speed of the rotor of the generator whereafter the speed estimator generates a rotational speed signal and a multiplier electrically connected to the adder and the speed estimator to multiply the rotational speed signal and the torque signal to create a power signal to be output by the speed controller.

Cavitation protection of pump governed according to rotational speed

Abstract: The flow ratios, with an operating revolutions per minute at the operating point of the pump, are compared by using the laws of similarity with the flow ratios of a point relevant to the design. They may be compared with regard to the net positive suction head value (NPSH). It can then be determined if the required pump-specific NPSH exceeds the NPSH in the existing system. The control system takes account of the operating characteristics of the pump.

Method for the field-oriented control of an induction motor

Abstract: A method for the field-oriented control of an induction motor (2) by means of a frequency converter (1) is disclosed, in which method a transformation angle (δ) is determined by estimation and is corrected in dependence on a rotational speed (ω mR ) of a rotor flux vector (i mR ) or of the induction motor (2) and/or in dependence on a delay time (T del ). In this connection it is desirable to improve the control behavior. To that end, the transformation angle (δ) is corrected a second time to compensate for a phase shift in the frequency converter (1).

Hydraulic drive device

Abstract: PROBLEM TO BE SOLVED: To increase the absorbing torque of a hydraulic pump using an engine whose performance is the same as a conventional type, to attain low noise, and to make the respective operations of the engine and the hydraulic pump efficient and optimum. SOLUTION: A hydraulic pump 2 is driven by an engine 1 for driving respective operation actuators 3, 4 with pressure oil from the hydraulic pump. A motor 8, which also serves as a generator, is fitted onto the hydraulic pump to allow the motor to conduct power generating operation and assist operation by means of the switching control of a switching control part 92 in a controller 9. If required absorbing torque exceeds the maximum assist torque in the first rotational speed correcting control of a rotational speed correction control part 91, the rotational speed of the engine of controlled so as to be increased, and the equivalent absorbing horsepower is exhibited by assist toque. When storage amount in a storing means 10 falls short in the second rotational speed correcting control is detected by a storage amount detecting means 101, the rotational speed of the engine is, the rotational speed of the engine is controlled so as to be increased and is changed from it assist operation are to a generating operation area. When the storage means is in a saturated state in the third rotational speed correcting control is detected, the rotational speed of the engine is controlled so as to be reduced, thus raducing the storage amount or electric energy consumed by the assist operation.

Striation-free coating method for high viscosity resist coating

Abstract: A method is proposed where striation-free coating of photoresist on a wafer is possible. This is accomplished by first prewetting the wafer with a particular agent, or solution, at a particular rate while the wafer is being accelerated to a predetermined rotational speed. Then the prewetting solution is cut off, after which the wafer is accelerated to a second rotational speed. Next, a photoresist of relatively high viscosity is dispensed concurrently with the wafer being accelerated to a third rotational speed, In order to achieve much reduced thickness variations than found in prior art, the third speed and the dispense rate are set at an unexpectedly lower value than that would be expected with a high viscosity photoresist. It is shown that with the disclosed method, critical dimensions of linewidths are preserved and product yield is improved.