Showing papers on "Rotational speed published in 2004"

Wind turbine Generator modeling and Simulation where rotational speed is the controlled variable

Abstract: To optimize the power produced in a wind turbine, the speed of the turbine should vary with the wind speed. A simple control method is proposed that will allow an induction machine to run a turbine at its maximum power coefficient. Various types of power control strategies have been suggested for application in variable speed wind turbines. The usual strategy is to control the power or the torque acting on the wind turbine shafts. This paper presents an alternative control strategy, where the rotational speed is the controlled variable. The paper describes a model, which is being developed to simulate the interaction between a wind turbine and the power system. The model is intended to simulate the behavior of the wind turbine using induction generators both during transient grid fault events and during normal operation. Sample simulation results for two induction generators (2/0.5 MW) validate the fundamental issues.

Power smoothing in wind generation systems using a sensorless vector controlled induction Machine driving a flywheel

Abstract: This paper presents a novel control strategy for power smoothing in generation systems in which power flow variations can occur. These variations are the norm in wind energy generation. The system is based on a sensorless vector controlled induction machine driving a flywheel. The induction machine is controlled to operate in a wide speed range by using flux weakening above rated speed. A speed observer is used to obtain the rotational speed in the whole speed range. In order to tune the speed observer and compensate for the parameter variation and uncertainties, a separate estimation of the speed is obtained from the rotor slot harmonics using an algorithm for spectral analysis. This algorithm can track fast dynamic changes in the rotational speed, with high accuracy. The control strategies have been experimentally verified on a 3.5-kW experimental setup with an induction machine and flywheel. The experimental results show the high level of performance obtained with the proposed sensorless vector control system.

Structural fatigue of pseudoelastic NiTi shape memory wires

Abstract: In this study, we consider the influence of wire diameter and rotational speed on fatigue rupture behaviour in bending rotation fatigue experiments. We show that the dependence of fatigue life on wire diameter and rotational speed is no longer observed when the bending rotation fatigue experiments are conducted in a silicon oil bath at constant temperature, or at low rotational speeds in air. Moreover, we qualitatively discuss the stress distribution in the wire during fatigue testing as a starting point for various mechanical investigations, such as the calculation of the dissipated energy in the wire during bending rotation experiments or the bending moment acting during bending rotation.

Control strategies for power smoothing using a flywheel driven by a sensorless vector-controlled induction machine operating in a wide speed range

Abstract: This paper presents a novel control strategy for power smoothing. The system is based on a sensorless vector-controlled induction machine driving a flywheel. The problem of regulating the DC-link voltage against input power surges or sudden changes in load demand is addressed. The induction machine is controlled to operate in a wide speed range by using flux weakening above rated speed. A model reference adaptive system observer is used to obtain the rotational speed in the whole speed range. The observer parameters are adapted during flux weakening in order to obtain close tracking of the flywheel speed. Experimental results for the operation of the induction machine between zero to more than twice base speed are presented and discussed.

Control of a Z-axis MEMS vibrational gyroscope

Abstract: This paper describes the design of the control loops in a z-axis, MEMS vibrational gyroscope operating in a vacuum enclosure. In this device, a silicon mass is driven through electrostatic actuator so that it has a sinusoidal linear motion, with a controlled speed. The design of a suitable controller, capable of maintaining the required speed and with prescribed restoring capabilities after shocks is briefly described in the paper. Attached to the driving mass, a second mass, free to move in the direction orthogonal to the motion of the first mass, is subjected to a Coriolis force, proportional to the product of the first mass speed by z-axis rotational speed. The sensing of the Coriolis force and, in turn, of the z-axis rotational speed, is performed in closed loop fashion, with a 1-bit quantized actuation. The restoring force that brings the motion of the second mass to zero is equivalent to the output bit stream of a band-pass sigma-delta converter and contains the information of the Coriolis force. The design of this second control loop and a detailed analysis on the signal-to-noise ratio achievable with the proposed design is reported.

Performance of a centrifugal pump running in inverse mode

Abstract: This paper presents the functional characterization of a centrifugal pump used as a turbine. It shows the characteristics of the machine involved at several rotational speeds, comparing the respective flows and heads. In this way, it is possible to observe the influence of the rotational speed on efficiency, as well as obtaining the characteristics at constant head and runaway speed. Also, the forces actuating on the impeller were studied. An uncertainty analysis was made to assess the accuracy of the results. The research results indicate that the turbine characteristics can be predicted to some extent from the pump characteristics, that water flows out of the runner free of swirl flow at the best efficiency point, and that radial stresses are lower than in pump mode.

Computational fluid dynamics modeling of the paddle dissolution apparatus: Agitation rate, mixing patterns, and fluid velocities

Abstract: The purpose of this research was to further investigate the hydrodynamics of the United States Pharmacopeia (USP) paddle dissolution apparatus using a previously generated computational fluid dynamics (CFD) model The influence of paddle rotational speed on the hydrodynamics in the dissolution vessel was simulated The maximum velocity magnitude for axial and tangential velocities at different locations in the vessel was found to increase linearly with the paddle rotational speed Path-lines of fluid mixing, which were examined from a central region at the base of the vessel, did not reveal a region of poor mixing between the upper cylin-drical and lower hemispherical volumes, as previously speculated Considerable differences in the resulting flow patterns were observed for paddle rotational speeds between 25 and 150 rpm The approximate time required to achieve complete mixing varied between 2 to 5 seconds at 150 rpm and 40 to 60 seconds at 25 rpm, although complete mixing was achievable for each speed examined An analysis of CFD-generated velocities above the top surface of a cylindrical compact positioned at the base of the vessel, below the center of the rotating paddle, revealed that the fluid in this region was undergoing solid body rotation An examination of the velocity boundary layers adjacent to the curved surface of the compact revealed large peaks in the shear rates for a region within∼3 mm from the base of the compact, consistent with a ‘grooving’ effect, which had been previously seen on the surface of compacts following dissolution, associated with a higher dissolution rate in this region

Load measuring device for rolling bearing unit and load measuring rolling bearing unit

Abstract: Revolution speeds nca, nib of rolling elements 9a, 9b are sensed by a pair of revolution speed sensors 21a, 21b. Also, a rotational speed ni of a hub 2 is sensed by a rotational speed sensor 15b. A sum 'nca+ncb' or a difference 'nca-nib' of the revolution speeds of rolling elements 9a, 9b in double rows is calculated based on sensed signals of the revolution speed sensors 21a, 21b, and then a ratio 'nca+nib/ni' or “nca-ncb/ni” of this sum or difference to the rotational speed ni is calculated. Then, the radial load or the an axial load is calculated based on the ratio 'nca+ncb/ni' or “ca-nib/ni' .

Modeling of Surge in Free-Spool Centrifugal Compressors: Experimental Validation

Abstract: The derivation of a compressor characteristic, and the experimental validation of a dynamic model for a variable speed centrifugal compressor using this characteristic, are presented. The dynamic compressor model of Fink et al. is used, and a variable speed compressor characteristic is derived by the use of energy transfer and loss analysis. It is demonstrated that taking into account the losses due to friction, incidence, mixing, and blade loading results in compressor characteristics that closely match the measured characteristics. The simulated response of the dynamic model was found to be in excellent agreement with the experimental results, both for set point changes using fuel flow and blow off and for surge oscillations. Analysis of the power spectrum of the in-surge rotational speed and pressure oscillations reveal that the simulated nonlinear oscillations match experimental values up to the third harmonic, both with respect to frequency and amplitude.

Prediction of rolling bed motion in rotating cylinders

Abstract: A mathematical model for the range of rolling bed motion has been developed to calculate the transverse solids motion in rotating cylinders. It is based on mass and momentum balances with physically specified and hence known initial conditions. The behavior of the bed material need only be described by two measurable parameters, the dynamic angle of repose and the angle of slope at the start of the boundary line (interface between the cascading layer and the plug flow region). The shape of the boundary line, the thickness of the cascading layer, the mass flow rate, and the velocity at the surface can be predicted as a function of rotation speed, filling degree, and cylinder diameter. No fitting parameter is needed for the calculation. To verify the model, experiments were carried out for many bed materials and rotating cylinder conditions. A correlation for the angle of slope at the start of the boundary line is given. The calculated results of the model are then compared to our own measurements and those reported in the literature. It is shown that the model agrees relatively well with the experiments. © 2004 American Institute of Chemical Engineers AIChE J, 50: 2783–2793, 2004

Air compressor and control method therefor

Abstract: For a motor that drives a compressed air generator, three operating modes which includes a powerful mode for rotating a motor in a high speed range, a silent mode for rotating the motor in a low speed range, and an automatic mode for automatically changing the rotation speed of the motor from the low speed to the high speed in accordance with a setup condition are prepared. A user can designate a desired operating mode by using an operating mode selection switch.

Supercharger with a planetary gear mechanism

Abstract: A supercharger of an engine comprises a motor/generator, a compressor provided in an air intake system of the engine, and a planetary gear mechanism The planetary gear mechanism includes a sun gear connected to a driving shaft of the engine, planetary gears connected to the motor/generator and a ring gear connected to the compressor The controller drives the motor/generator to control a rotational speed of the planetary gears Through the control of the rotational speed of the planetary gears, a rotational speed of the compressor is controlled independently of a rotational speed of the engine Thus, the rotation speed of the compressor can be continuously changed over a range from zero to a higher rotational speed than the engine rotational speed Any desired supercharged pressure can be generated independently of the engine rotational speed

Blade and ground speed control system

Abstract: A self-propelled mower with blade and ground speed controls. The mower includes a motor with an output shaft and a rotatable cutting blade mounted on a blade shaft. The motor may be an internal combustion engine. A torque transmitting mechanism such as a variable diameter pulley defines a rotational speed ratio between the output shaft and the blade shaft. A transmission is coupled to the output shaft. Sensors provide an electronic control unit with the blade speed, ground speed and engine speed. The ECU may be used to maintain either a desired blade speed or a desired ground speed. To maintain a desired blade speed, the ECU monitors the blade speed and, when the blade speed diverges from the desired speed, adjusts either the rotational speed ratio of the output shaft and blade shaft or the ground speed of the mower to maintain the desired blade speed.

Injection control system of internal combustion engine

Abstract: An electronic control unit (ECU) of an injection control system of an internal combustion engine measures an engine rotation speed in a period from a time point when an exhaust valve opens to a time point when a top dead center of a next cylinder is detected after a single injection is performed. The ECU calculates a rotation speed fluctuation caused by the single injection based on the engine rotation speed. The engine rotation speed provided immediately after the single injection is measured after a cylinder pressure increased by the single injection decreases to substantially the same level as the cylinder pressure provided in the case where the single injection is not performed. Therefore, the rotation speed fluctuation corresponding to torque generated by the single injection can be measured accurately.

Coupling for dual member pipe

Abstract: A coupling assembly (100) to interconnect an inner member (40) and an outer member (42) of a dual member drill string in torque transmitting engagement is disclosed. The coupling assembly (100) is adapted to transmit torque input from both members (40, 42) to a downhole tool. In one embodiment, the coupling assembly comprises a connector sub (102) that fixedly and non-fixedly couples both members. In another embodiment, the coupling assembly comprises a clutch mechanism (138) to interconnect both members when the rotational speed of the outer member exceeds the rotational speed of the inner member. In another embodiment, the coupling assembly comprises a mechanism to couple both members (40, 42) by axial downhole movement of the inner member (40) relative to the outer member (42). In another embodiment, the coupling assembly comprises a planetary gear system (556, 562, 558) that interconnects both members to provide high torque to the downhole tool at relatively low output speed of the dual member drill string.

Hybrid compressor device

Abstract: In a hybrid compressor for a vehicle where a vehicle engine is stopped when the vehicle is temporally stopped, a pulley, a motor and a compressor can be driven in independent from each other, and are connected to a sun gear, planetary carriers and a ring gear of a planetary gear. A rotational speed of the motor is adjusted by a controller, so that a rotational speed of the compressor is changed with respect to a rotational speed of the pulley. Accordingly, production cost of the hybrid compressor and the size thereof can be reduced, while a cooling function can be ensured even when the vehicle engine is stopped.

Tandem rotor wing rotational position control system

Abstract: A rotational position-adjusting system (6) for a vertical takeoff and landing aircraft (4) . The system (6) includes multiple detectors (60) that generate rotor signals. The rotor signals are indicative of the position of each rotor (8) of the aircraft (4) . The rotors (8) provide lift to the aircraft (4) . A controller (24) is coupled to the detectors (60) and adjusts the rotational speed of one or more of the rotors (8) in response to the rotor signals.

Adaptive optimal fuzzy control for variable speed fixed pitch wind turbines

Abstract: Automatic control is crucial to the efficiency and reliability of wind power generation systems. Variable speed fixed pitch wind turbines have strong nonlinear and unstable characteristics with many uncertain factors and disturbances at large wind speed ranges. Based on the motion equation of the generator and wind turbine, adaptive optimal fuzzy system for rotational speed control is proposed by using the algorithm of the nearest-neighbour clustering learning. This algorithm synthesizes both mechanical and electrical dynamics of wind energy conversion system. System identification is a part of the controller. The rotational speed reference is determined by estimated aerodynamic torque using Kalman filter. The method avoids the inaccuracy of measuring the wind speed. Simulation results verify the effectiveness of the proposed control methods.

Washington machine and method of performing spinning operation

Abstract: A method of performing a spinning operation of a washing machine is disclosed. First, a load weight of wet clothes contained in a tub is measured, and an optimal acceleration rate is calculated based upon the measured load weight. Finally, a rotational speed of the tub is gradually increased up to a predetermined speed at the calculated optimal acceleration rate such that the unbalanced distribution of the wet clothes within the tub is minimized.

Turbo chiller, compressor therefor, and control method therefor

Abstract: A compressor for a turbo chiller that can stably and efficiently operate in various operating states is provided. An aerodynamic feature map showing a rotating stall line at which rotating stall occurs is provided on a map represented by a flow parameter reflecting the volume flow based on the output thermal capacity of the chiller and by a pressure parameter reflecting the head based on the evaporator pressure and the condenser pressure. A minimum rotation speed obtaining unit obtains a minimum rotation speed from the pressure parameter and the rotating stall line on the aerodynamic feature map in the current operating state, and a rotation speed greater than or equal to the minimum rotation speed thus obtained is designated to the inverter.

Wind power generator

Abstract: PROBLEM TO BE SOLVED: To provide a wind power generator having such a clutch not requiring a big force to operate, unlike a friction clutch requiring a big force. SOLUTION: In this wind power generator, a generator shaft 5 connected to a turbine rotating shaft 3 through the clutch is rotated by the rotation of a turbine and the turbine rotating shaft 3 to generate a power by a generator. In the clutch 6, a tooth 34 is engaged with a tooth 44 when the rotational speed of the turbine rotating shaft 3 is equal to or higher than a predetermined value to connect a first rotating connection member 21 and a second rotating connection member. When the rotational speed of the turbine rotating shaft 3 is smaller than the predetermined value, the pressing part 50 of an electric actuator 23 presses the acting area 43a of an outer plate 43 downward. Then, a plurality of ribs 40 are deformed so that the radial outer ends thereof lower downward, and the outer plate 43 is displaced downward. Consequently, since the tooth 34 is disengaged from the tooth 44, the first rotating connection member 21 is separated from the second rotating connection member 22. COPYRIGHT: (C)2007,JPO&INPIT

Linear theory of a rotating internal part projectile configuration in atmospheric flight

Abstract: Dynamic modeling of the atmospheric flight mechanics of a projectile equipped with an internal rotating disk is investigated, and a modified projectile linear theory is established for this configuration. To model this type of projectile requires alteration of several of the coefficients of the epicyclic dynamics leading to changes in the fast and slow epicyclic modes. A study of the frequency and damping properties of the epicyclic modes is conducted by the systematic variation of disk orientation, location, mass, and rotational speed. It is shown that the presence of an internal rotating disk can causes substantial changes in the epicyclic dynamics, including instability, in some configurations.

Transmission input shaft speed measuring assembly

Abstract: A device for sensing the input shaft speed of an automotive automatic transmission that is driven by the engine through the fluid coupling of a torque converter The speed sensor device includes circumferentially spaced markings about the transmission input shaft and a speed sensor that is placed at close proximity to the circumferentially spaced markings through a hole in the torque converter stator shaft An electronic control unit (ECU) analyzes the sensor output signal and in the case of an active speed sensor it also functions as its power source During vehicle operation, the transmission input shaft rotates the target wheel in front of the speed sensor causing modulation of its output signal The electronic control unit analyzes the signal modulation and calculates the input shaft rotational speed A variety of sensor/target-wheel options and sensor mounting techniques could be used depending on the application constraints