Rotational speed

About: Rotational speed is a research topic. Over the lifetime, 23327 publications have been published within this topic receiving 151696 citations. The topic is also known as: speed of revolution & revolution rate.

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.

Turbine engine arrangements

Abstract: A turbine engine arrangement is provided in which contra rotating shafts 104, 105 are respectively secured to a fan and a gearbox 106 which is also coupled to the shaft 104. In such circumstances the relative rotational speed ratio between the shafts 104, 105 can be determined with a first low pressure turbine 101 secured to the first shaft 104 arranged to rotate at a lower speed but provide high work whilst a second low pressure turbine 102 secured to the second shaft 105 rotates at a higher speed governed by the gearbox 106. By such an arrangement a smaller gearbox 106 may be used as less power is transferred through that gearbox 106 than with previous arrangements. By contra rotation of the turbines 101, 102 a lower flow deflection guide vane assembly 103 may be used and a further stator/guide vane assembly is not required between the turbines 101, 102.

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.

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.

Design, construction and characterization of a flightworthy piezoelectric solid state adaptive rotor

Abstract: The development of a new type of flightworthy adaptive rotor system is presented. By building upon earlier adaptive rotor work, a new miniature solid state adaptive rotor (SSAR) was built using directionally attached piezoelectric (DAP) torque-plates controlling Hiller servopaddles. These servopaddles change the rotor disk tilt and thereby induce changes in forces and moments for flight control. To demonstrate the concept, a 23.5 in diameter helicopter rotor was built using DAP servopaddles at the hub. The servopaddles were constructed from PZT-5H piezoceramic actuator sheets bonded symmetrically at . An aluminum substrate and a high temperature cure was used to provide precompression. Analytical modeling was accomplished by laminated plate theory along with strip theory aerodynamics and inertial relations. Because propeller moments are proportional to servopaddle deflections at a fixed rotational speed, it was possible to cancel them out by balancing an aeroelastic coupling between the center of mass, aerodynamic center and elastic axis. Bench testing of the SSAR showed that the rotor system could produce static servopaddle deflections in excess of with good agreement between theory and experiment. With the spinning rotor, the servopaddles demonstrated dynamic capability in excess of . As the rotor speed was increased, deviations between linear theory and experiment also increased. Nonetheless, the rotor still demonstrated servopaddle deflections at full rotor speed (1600 RPM). A detailed weight statement of the conventional and SSAR systems shows that the SSAR helicopter experienced a 40% reduction in flight control system weight, which resulted in an 8% cut in total aircraft gross weight, a 26% drop in parasite drag and a drop in flight control system part count from 94 components down to five.