Showing papers on "Rotational speed published in 1988"

High Order Subharmonic Response of High Speed Rotors in Bearing Clearance

Abstract: Subharmonic vibration refers to the response of a dynamic system to excitation at a whole-number multiple (n) of its natural frequency by vibrating asynchronously at its natural frequency, that is, at (1/n) of the excitation. The phenomenon is generally associated with asymmetry in the stiffness vs. deflection characteristic of the system. It may be characterized as the “bouncing” of the rotor on the surface of the stiff support, energized by every nth unbalance impulse prior to contact. Second, third and fourth order subharmonic vibration responses have previously been observed in high speed rotating machinery with such an asymmetry in the bearing supports. An incident is reported where 8th and 9th order subharmonic vibration responses have been observed in a high speed rotor. A simple but exact computer model of the phenomenon has been evolved based on the numerical integration of a finite difference formulation. Response curves and wave forms of rotor deflection at individual speeds are computed. It is shown that the response is a series of pseudo-critical peaks at whole-number multiples of the rotational speed. Very high orders of subharmonic vibration are found to be possible for systems with low damping and extreme nonlinearity.

Locomotive wheelslip control system

Abstract: A locomotive propulsion system includes wheelslip control with the following interrelated features: comparing the rotational speeds of the locomotive's separately driven wheels and detecting the highest and lowest; providing a reference speed value indicative of the rotational speed of a wheel that is not slipping; determining a desired maximum difference between the reference speed and a selected one of the detected speeds; deriving a speed error value by summing the reference speed, selected speed, and maximum difference; obtaining a wheelslip correction value which is a function of the speed error value; reducing the magnitude of voltage applied to the locomotive's traction motors in accordance with the correction value.

Automatic focusing circuit for automatically matching focus in response to video signal

Abstract: In an automatic focusing apparatus of a video camera, a first focus evaluating value which steeply changes and a second focus evaluating value which gently changes relative to the position of a lens, are detected in response to a video signal obtained in an image sensing circuit (4). A switching circuit (19) alternately selects the first and second focus evaluating values every one field, to apply the same to in-focus state detecting circuits (20, 21), respectively. The in-focus state detecting circuits (20, 21), together with a focusing motor control circuit (10), perform an automatic focusing operation by hill-climbing control. In addition, a calculating circuit (22) calculates the relative ratio of the first focus evaluating value to the second focus evaluating value. The focusing motor control circuit (10) sets the rotational speed of a focusing motor (3) to a normal speed when the calculated relative ratio is smaller than a predetermined value while setting the rotational speed of the focusing motor (3) to a low speed when it is larger than the predetermined value. Therefore, a lens (1) is moved at low speed when the focusing lens is in the vicinity of the in-focus position while being moved at high speed when it is in the defocused state.

Sprinkler having a flow rate compensating slow speed rotary distributor

Abstract: A rotary sprinkler head comprising a sprinkler body having an outlet defined by a selected nozzle for directing water under pressure communicated therewith into an atmospheric condition in a primary stream having a generally vertically extending axis A rotary distributor is mounted for rotational movement about a generally vertical rotational axis with respect to said sprinkler body in engaging relation with respect to the primary stream directed from said nozzle so as to be rotated thereby A speed reducer is provided to slow the rotational speed imparted to the distributor The distributor has surfaces for directing the primary stream outwardly in such a way as to create reactionary forces having net components acting tangentially to the axis of rotation of the distributor which do not increase substantially with increases in flow rates under constant pressure conditions thereby enabling the distributor to operate with a relatively narrow range of rotational speed changes within a relatively wide range of nozzle size changes

Sensorless brushless motor

Abstract: In a brushless motor of the kind not employing a sensor for detecting rotor position, a rotational reference position of the rotor is detected based on an induction voltage in a stator excitation coil, and an energization switching point of the stator excitation coil is determined to occur a delayed time from the reference position. The time delay is increased or decreased in response to the rotational speed of the motor, so that energization switching of the excitation coils is performed at the optimum position in accordance with corresponding changes in the rotational speed of the motor. Signal masking is performed so that noise generated by the excitation coil switching does not interfere with the detection of the rotor reference position.

Wheel speed sensor

Abstract: A magnetoresistive sensor monitors the passing of teeth on a rotating wheel and generates a DC biased speed signal. An amplifier compares this voltage with the capacitor voltage and charges or discharges the capacitor through a pair of parallel coupled, oppositely poled diodes to maintain the capacitor voltage equal to the DC biased speed signal. The voltage across the diode pair is supplied to a comparator switch to provide a pulse train having a frequency that is a measure of the rotational speed of the wheel.

Speed control system for a vehicle

Abstract: A vehicle speed control system is provided to maintain the vehicle speed at a target value. The control system includes a target vehicle speed determining section, a section for calculating a driving torque necessary to drive the vehicle at the target vehicle speed, a section for calculating a target engine rotational speed and an engine load torque and a section for calculating a control amount for controlling an opening of the throttle valve of the engine. The driving torque calculating section and the control amount calculating section are designed based on linear control theory on physical models describing the behavior of the vehicle and the engine, respectively, thereby improving the responsiveness of the control system compared to conventional PID control. The design of the control system is characterized by separate sections which reduces designing labor and which facilitate standardization of every section.

Cooling device for an internal combustion engine and method for controlling such a cooling device

Abstract: A device and method for cooling an internal combustion engine is disclosed in which a simple control circuit constructed of relatively inexpensive components enables the rotational speed of an electric motor employed in the cooling device to be controlled in adaptation to various temperature levels of a cooling circuit. The control circuit includes a power semiconductor which is used to drive the electric motor in certain speed ranges associated with predetermined temperature levels. The control circuit also incorporates a bypass circuit that permits the electrical motor to be driven in particular speed ranges without the use of the power semiconductor. Thus, the electric motor can be driven at one hundred percent of its speed capacity by eliminating a voltage drop associated with the power semiconductor.

Rotational effects on natural convection in a horizontal cylinder

Abstract: A numerical computation is carried out to study the interaction of rotation and natural convection inside a finite horizontal cylinder. The natural convection is due to differential heating on the two ends, while the rotation is along the axis of the horizontal cylinder. The aspect ratio, length of the cylinder to its radius, is 2.0. The Grashof number is fixed at 1.43 × 106 with air as a working fluid. The effect of rotation is examined with Gr/Re2 from 7.0 × 10−2 to ∞, which covers the range from rotation dominated flow to buoyancy dominated flow. It is found that when rotational speed is relatively small or Gr/Re2 » 1, the effect of rotation is to render the spatial heat flux distribution more uniform. As the rotational speed increases, the heat transfer rate distribution on the end surfaces is more homogenous and its level is also reduced. When the rotational speed is sufficiently high (Gr/Re2 « 1.0), heat transfer is by conduction only and the whole fluid inside the enclosure rotates as a rigid body. It is shown that there exists a rotation speed range in which one can have both relatively high and uniform heat transfer rates on the end walls.

Flywheel with a torsional damper

Abstract: A flywheel device with a torsional damper having a first spring mechanism (40) with a synthetic spring constant K1 and a second spring mechanism (50) with a synthetic spring constant K2, arranged in series with each other as a spring combination. The second spring mechanism (50) is controlled so as to be changed in operation between effective and ineffective states by a second spring mechanism operation controlling device (60). Thus, the vibrational characteristic of the flywheel device includes two characteristics, that is, spring constant K1 and spring constant K3 which is a synthesis of the spring constants K1 and K2. When the rotational speed of the flywheel device passes through the resonance speed of the vibrational characteristic with spring constant K1, the characteristic of the flywheel device is shifted to spring constant K3 and, as a result, there is no notable resonance speed throughout the entire range of rotational speeds. Due to this shift mechanism, it is not necessary to provide a continuously sliding friction mechanism against the flywheel device. Further, due to this omission of the continuously sliding friction mechanism, the torque variation absorbing effect at the standard range of rotational speeds is greatly improved.

Exposure method and apparatus therefor

Abstract: In an exposure method of the present invention, exposure light is radiated onto a peripheral portion of a substrate to be processed while the substrate is rotated, and the rotational speed of the substrate is selectively decreased when a specific peripheral portion reaches an exposure area, thereby performing predetermined exposure of the substrate. An exposure apparatus of the present invention includes a mounting table on which the substrate is mounted, a rotating mechanism for rotating the mounting table at a predetermined rotational speed, a light radiating element arranged to oppose a mounting surface of the mounting table, light amount control means for controlling the amount of light radiated from the light radiating element onto the substrate, and rotational speed control means for controlling the rotational speed of the mounting table in accordance with the radiation amount of light from the light radiating element.

Drive control device for vehicle

Abstract: In a continuously variable transmission, a target vehicle driving torque is obtained according to engine load, and a target rotational value of the continuously variable transmission possible to output the target vehicle driving torque is determined from a vehicle speed and an engine torque at that time. The target rotational value may be a target rotational speed of an input shaft of the continuously variable transmission, or, a target speed ratio between a rotational speed of an output shaft and a rotational speed of the input shaft. As a result, the target rotational value to which a driver's intention is properly reflected can be set irrespective of condition, i.e., a normal running condition or a speed change transitional condition. Further, it is unnecessary to provide a device such as a throttle actuator for controlling an engine output independently of an accelerator pedal.

Automatic focusing apparatus having a variable focusing speed and particularly suited for use with interlaced scanning

Abstract: In an automatic focusing apparatus of a video camera, a first focus evaluating value which steeply changes and a second focus evaluating value which gently changes relative to the position of a lens, are detected in response to a video signal obtained in an image sensing circuit (4). A switching circuit (19) alternately selects the first and second focus evaluating values every one field to apply the same to in-focus state detecting circuits (20, 21), respectively. The in-focus state detecting circuits (20, 21), together with a focusing motor control circuit (10), perform an automatic focusing operation by hill-climbing control. In addition, a calculating circuit (22) calculates the relative ratio of the first focus evaluating value to the second focus evaluating value. The focusing motor control circuit (10) sets the rotational speed of a focusing motor (3) to a normal speed when the calculated relative ratio is smaller than a predetermined value while setting the rotational speed of the focusing motor (3) to a low speed when it is larger than the predetermined value. Therefore, a lens (1) is moved at low speed when the focusing lens is in the vicinity of the in-focus position while being moved at high speed when it is in the defocused state.

Adaptive noise cancelling for magnetic bearing auto-balancing

Abstract: A separate adaptive noise canceller receiving a reference input of a rotor speed synchronization pulse is connected in the X and Y axis positional control loops of a magnetic bearing utilized to position a rotor suspended thereby. The output of the noise canceller is self-adjusting by the inclusion of an adaptive filter implementing a least mean square algorithm to force the gain of the control loop to zero at not only the fundamental of the rotational speed, but all harmonic frequencies thereof, thereby reducing the vibration and control system power dissipation of the magnetic bearing at the rotational fundamental as well as at the rotational harmonics.

A method of controlling brushless electric motors and control circuit therefor

Abstract: In order to control a brushless D.C. motor (1), use is made of a three-phase driver signal delivered by a rotor position sensor (3) for driving transistors (7) in a transistor bridge circuit (6). The transistor bridge circuit (6) supplies the windings (5a, 5b, 5c) in the stator (4) of the D.C. motor (1) with current pulses. Using a microprocessor control (12') in which the signals delivered by the rotor position sensor (3) for driving the transistors are processed, the commutation point for the transistors (7) is brought forward by a predetermined amount of time which is optionally constant or dependent on the rotational speed. By this precommutation, an increase in the torque is achieved in higher rotational speed ranges of the D.C. motor, independently of the rotational speed.

Steerable self-regulating concrete cutting saw

Abstract: A self-propelled concrete cutting saw in which the saw and self-propelled platform associated with the saw are both driven by hydraulic motors, with separate motors for each of the two propelling wheels so that the device may be steered by varying the speed of either of the wheels, with the speed of longitudinal movement of the saw through the concrete being controlled by the density of the concrete being cut by the saw so that the saw blade is operated at an optimum rotational speed.

Automated thermal transfer device and control system therefor

Abstract: A control system for a thermal transfer device in which a selected image is transferred from a strip of color carrying ribbon to a strip of image carrying tape and precise alignment between adjacent columns of vertical print is achieved by monitoring and controlling the rotational speed of the drive means for the thermal transfer device and activating the printing of each column of pixel data based upon positional information of the tape and ribbon determined in relation to the rotational speed of the drive means so that each column of pixel data is of a uniform and consistent width.

Crystal diameter controlling method

Abstract: Disclosed is a method of controlling the diameter of a single crystal produced by the Czochralski method. The diameter of a tapered portion of the single crystal is controlled by controlling the temperature of a melt in a crucible and the rotational speed of the crucible. The control range of the rotational speed of the crucible is made narrower as the diameter of the tapered portion approaches closer to that of a body portion, and the rotational speed is made constant while the body portion is grown.

Overspeed limiter for gas turbine aeroengine

Abstract: A fuel control system for a three spool gas turbine aeroengine has a fuel contorl unit incorporating an intermediate pressure spool overspeed limiter. A fuel control signal is produced which drives a fuel metering unit to meter the flow of fuel to the engine in accordance with control and sensor inputs as acted upon by predetermined control laws incorporated in the fuel control unit. The engine has variable inlet guide vanes (VIGV's) in one or more of its compressor stages and a safety problem arises in that if the VIGV's fail at an angle for low engine speed while the engine is accelerating to a high speed, the rotational speed of the intermediate pressure spool can increase very quickly. This can lead to overshooting of maximum acceptable levels of spool speed before known overspeed limiters have time to regain control. The problem is solved by incorporating an overspeed limiter function for the intermediate pressure spool whose speed limit setting is not just an upper limit as previously, but which varies between lower and upper limits as a function of at least one other internal working parameter of the engine such as the speed of the high pressure spool. The arrangement is such that whenever actual spool speed exceeds the variable limit, a signal is generated which is proportional to the difference between actual spool speed and the variable limit and which is used to reduce the fuel flow to the engine.

Process and extrusion apparatus for extruding a plastic web

Abstract: A plastic web is made by an extrusion apparatus having a plastics screw press, a metering pump with a volume flow depending on the rotation speed, an output die and a rolling unit with calendaring rolls. The flow of a thermoplastic material is regulated with the metering pump. The melt web issuing from the output die is cooled and calibrated. The process uses a metering pump which has substantially linear volume flow/rotation speed characteristics in the regulated range of rotation speeds and together with the rolling unit is part of a common computerized control system. The peripheral speed of the calendaring rolls is controlled so that it is proportional to the rotation speed of the metering pump. The special proportionality factor for the speed ratio is set by a computer which controls the roll speed so that no undesirable thickness variations or other product defects occur. Also additional components including a computer and controller which regulates the roll speed are provided to the extrusion apparatus so that the process according to my invention can be performed.

Lubrication of gear means for a wind energy installation

Abstract: A method of lubricating gear means for a wind energy installation comprises the steps of maintaining operational lubrication by an oil-circulating system (12 to 15) with injection lubrication, with the oil being cooled at the same time. The normal height (I) of the oil level in the gear means casing (11) is increased to a height (II) necessary for splash lubrication when the rotational speed of the gear means falls below a settable value. To increase the height of the oil level, an additional quantity of oil is fed to the casing (11) from a reservoir (17).

Control system for automotive automatic transmission including downshift select shock suppression arrangement

Abstract: When the select lever is shifted from D ranged to one of I or II ranges for the purposes of producing engine braking, the engine speed is momentarily increased to a level whereat the effect of coasting torque which tends to increase the rotational speed of the engine is obviated.

Blower motor control for an air conditioner

Abstract: A blower motor control for an air conditioner is carried out so that when a detected actual rotation speed has come into an allowable deviation range to a target rotation speed at the time of controlling the motor so as to approach its rotation speed to the target rotation speed, the output for adjusting the rotation speed is not changed. As a result, a stable rotation speed can be obtained as long as the load on the motor does not fluctuate. Furthermore, after the output has been fixed, the allowable deviation range is expanded to prevent the output from changing even if slight load fluctuation is caused. This allows stable controls.

Drive control with overload protection for a drill device

Abstract: Drive control for a drilling device including a universal motor is arranged so that the total available mains voltage is applied when a fraction of the motor torque, available for the full work range of the device, is reached. If a higher torque is desired, the motor torque/rotational speed curve follows the natural characteristic line until a load point is reached where current limitation occurs. Accordingly, as the motor speed decreases as the normal work range is exceeded, the operator of the drilling device is signaled concerning the load state due to the noise developed in the drilling device.