Showing papers on "Rotor (electric) published in 2002"

Joint locking mechanism for mechanical arm

Abstract: The utility model relates to a joint locking mechanism for mechanical arm which includes an end shaft and a shaft base which are arranged on the arm pole. An end shaft is supported by the shaft base. The end shaft is provided with an electromagnetic clutch which has a semi clutch. The electromagnetic clutch is provided with an electromagnetic coil, a gag bit and a plurality of stationary plates and fixed with the shaft base. The semi clutch with a plurality of rotor plates is fixed with the end shaft. The stationary plates and the rotor plates are arranged at intervals and overlapped with the surface of the gag bit. The gag bit is provided with a spring which enables the stationary plates connected with the rotor plates through friction and makes the rotor plates stop. The utility model has the advantages of good fastening result, accurate fixing and convenient and flexible use.

Flat type-vibration motor

Abstract: PURPOSE: A flat vibration motor is provided to enhance the number of rotations and vibration characteristics by arranging an auxiliary magnet on an upper case. CONSTITUTION: A flat vibration motor(1) includes upper and lower cases(10,20), a shaft(15) inserted into the upper and lower cases(10,20), an eccentric rotor(30) eccentrically supported on an external part of the shaft(15), and a magnetic force generating unit fixed on an inside surface of the upper and lower cases(10,20) around a center of the eccentric rotor(30). A flange is formed on the upper and lower cases(10,20) to axially fix both ends of the shaft(15) at the center of the inside surface. A substrate(21) is attached on an upper surface of the lower case(20). An end of a pair of brushes(23) is fixed to the substrate(21) and upper end of the brushes(23) upwardly extends toward the eccentric rotor(30). The shaft(15) is a fixed shaft for allowing the eccentric rotor(30) to rotate. Both ends of the shaft are fixed to the flanges of the upper and lower cases. A bearing is inserted on an end of the center of the shaft(15). A shaft hole is formed on a side section of the eccentric rotor(30), and the bearing is inserted into the shaft hole, so that the eccentric rotor rotates about the shaft(15).

Variable-Speed Wind Power Generation Using a Doubly Fed Wound Rotor Induction Machine: A Comparison with Alternative Schemes

Abstract: In this paper, a wind energy conversion system (WECS) using a grid-connected wound rotor induction machine controlled from the rotor side is compared with both fixed speed and variable speed systems using a cage rotor induction machine. The comparison is done on, the basis of: (1) major hardware components required; (2) operating region; and (3) energy output due to a defined wind function using the characteristics of a practical wind turbine. Although a fixed speed system is more simple and reliable, it severely limits the energy output of a wind turbine. In case of variable speed systems, comparison shows that using a wound rotor induction machine of similar rating can significantly enhance energy capture. This comes about due to the ability to operate with rated torque even at supersynchronous speeds; power is then generated out of the rotor as well as the stator. Moreover, with rotor side control, the voltage rating of the power devices and DC bus capacitor bank is reduced. The size of the line side inductor also decreased. Results are presented to show the substantial advantages of the doubly fed system.

A method of tracking the peak power points for a variable speed wind energy conversion system

Abstract: In this paper, a method of tracking the peak power in a wind energy conversion system (WECS) is proposed, which is independent of the turbine parameters and air density. The algorithm searches for the peak power by varying the speed in the desired direction. The generator is operated in the speed control mode with the speed reference being dynamically modified in accordance with the magnitude and direction of change of active power. The peak power points in the P-/spl omega/ curve correspond to dP/d/spl omega/=0. This fact is made use of in the optimum point search algorithm. The generator considered is a wound rotor induction machine whose stator is connected directly to the grid and the rotor is fed through back-to-back pulse-width-modulation (PWM) converters. Stator flux-oriented vector control is applied to control the active and reactive current loops independently. The turbine characteristics are generated by a DC motor fed from a commercial DC drive. All of the control loops are executed by a single-chip digital signal processor (DSP) controller TMS320F240. Experimental results show that the performance of the control algorithm compares well with the conventional torque control method.

Navier-Stokes predictions of the NREL phase VI rotor in the NASA Ames 80-by-120 wind tunnel

Abstract: The application of an incompressible Reynolds Averaged Navier-Stokes solver to cases from the NREL/NASA Ames wind tunnel test is described. Six cases of the NREL PHASE-VI rotor in the upwind configuration under zero yaw and zero degrees tip pitch are computed. Favorable comparison of the computed results with measurements in the form of shaft torque, root moments, spanwise force distributions, and pressure distributions are shown. The good agreement documents the feasibility of 3D CFD computations in connection with prediction of the performance of new rotors. Additionally it is shown how CFD computations can be used to determine the three dimensional effects in rotor flows.© 2002 ASME

DITC-direct instantaneous torque control of switched reluctance drives

Abstract: This paper presents an online instantaneous torque control technique for switched reluctance machines called direct instantaneous torque control. The method comprises two novel aspects. First, torque is estimated as a function of terminal quantities, i.e., flux linkage and phase current. Hence, torque estimation is independent of the rotor position. Secondly, high-bandwidth drive performance is obtained by implementing a digital torque hysteresis controller. Thus, the method works without torque profile functions and auxiliary phase commutating strategies. Therefore, the control algorithm offers a wide drive operating range without the use of a high-resolution shaft position sensor or sensitive position estimation techniques. Experimental and simulation results are presented in this paper.

Sensorless control of interior permanent magnet machine drives with zero-phase-lag position estimation

Abstract: This paper presents an improved method to estimate rotor motion states for an interior permanent-magnet machine drive. This approach is based on the estimation of a saliency-based electromotive force (EMF) in the stationary reference frame using a state filter. The spatial information obtained from the estimated saliency-based EMF is used in an observer to estimate the motor motion states. By using the commanded torque as a feedforward input to the observer, the motion state estimation has zero-phase lag, providing a very-high-bandwidth estimate.

Design of a four-rotor aerial robot

Abstract: The design and fabrication of a prototype four-rotor vertical take-off and landing (VTOL) aerial robot for use as indoor experimental robotics platform is presented. The flyer is termed an X4-flyer. A development of the dynamic model of the system is presented and a pilot augmentation control design is proposed.

Gas turbine combustor

Abstract: PROBLEM TO BE SOLVED: To provide a centrifugal spray type gas turbine combustor where stable combustion is effected and carbon hardly adheres to an inner liner SOLUTION: A fourth part (3B) of the inner linear (3) is formed in a cylindrical shape in parallel with the outer peripheral surface of a rotor (1) A gas (S) is provided between the fourth part and the outer peripheral surface of the rotor and a part of air guided to a second space A4 flows through the gap and collides with a wall surface (31) of a deflection member (30) annexed to the rotor and bent to the outside in a radial direction and introduced in a combustion chamber (4) along a first part (3A) of the inner liner Further, fuel injected through a nozzle hole (22) of a fuel injection member (20) is agitated in a region surrounded by a protrusion (23) of the deflection member (30), the rotor, and the fuel injection member, flows in the combustion chamber

Dual-rotor, radial-flux, toroidally-wound, permanent-magnet machines

Abstract: A novel machine family-dual-rotor, radial-flux, toroidally wound, permanent-magnet (RFTPM) machines-is proposed in order to substantially improve machine torque density and efficiency. After the principles of operation, configurations, and features are discussed, the machine design and optimization guidelines are given. A prototype has been designed, built, and tested. The measured torque density of the prototype, which well matches the design value, is almost three times of that of the induction machine with the same power of 3 hp and speed. Meanwhile the efficiency is still kept high and the material cost is kept low by using ferrite magnets. Three novel approaches are proposed to reduce the cogging torque in the RFTPM machines, whose validity is verified by finite-element analysis results and experimental measurements.

Sensorless position control of permanent magnet synchronous machines without limitation at zero speed

Abstract: Sensorless position control of surface mounted permanent magnet synchronous machines (SMPMSM) still is a challenge High performance position control at low and zero speed is only possible using anisotropic effects being considered not in the fundamental-frequency machine models, but in extended high-frequency models This paper presents a new high-frequency injection method estimating the rotor position, which overcomes the small signal to noise ratio inherent to methods of this type published so far This enables to track even small saliencies typical for SMPM synchronous machines A small high-frequency voltage signal is injected into the rotor d-axis with no influence on the torque producing q-current The demodulation of the responding high-frequency current signal is independent on machine parameters Therefore the proposed method is independent on machine parameters and simply adaptable to different machines As only the high frequency current has to be processed for position estimation, there is no additional hardware necessary besides that for standard drives with field oriented control

Underwater ducted turbine

Abstract: An apparatus is disclosed for a turbine for generating electrical power from water or air flow comprising at least one rotor disk having a plurality of hydrofoil blades, guide vanes, a cylindrical housing, and a generator means. A rim generator comprising a magnet race rotor rim and fixed stator coils in the housing is used. The apparatus is fitted with a screen to stop the ingress of debris and marine life, and a skirt augmenter device to reduce the Betz effect. The apparatus is preferably for sub-sea deployment and driven by tidal currents, but may be powered by river current or wave driven air or by wind. The apparatus may be deployed on at least one telescoping pole, tethered to the sea-bed and kept buoyant by buoyant concrete in the housing, or inserted in a dam, under a barge or in a tidal power array.

On-field experience with online diagnosis of large induction motors cage failures using MCSA

Abstract: The experience gained by ENEL Produzione (previously the Italian Electric Board) on monitoring the cage condition of large induction motors is reported in this paper The diagnostic procedure is based on the motor current signature analysis and, in particular, on the two sideband current components near the frequency fundamental line that appear in the current power spectrum when a rotor bar/ring breakage occurs According to the developed procedure, a diagnostic index obtained from these components is stored and its trend as a function of time allows for the detection of the occurrence of a failure in most cases This event is clearly shown by the overcoming of a prefixed and triggered threshold Moreover, machines with particular rotor magnetic structure are considered In this case, unexpectedly high sideband components appear, even in the presence of healthy cages, and the test procedure was adapted to account for these conditions

Optimal design of horizontal-axis wind turbines using blade-element theory and evolutionary computation

Abstract: This paper describes a multi-objective optimization method for the design of stall-regulated horizontal-axis wind turbines. Two modules are used for this purpose: an aerodynamic model implementing the blade-element theory and a multi-objective evolutionary algorithm. The former provides a sufficiently accurate solution of the flow field around the rotor disc; the latter handles the decision variables of the optimization problem, i.e., the main geometrical parameters of the rotor configuration, and promotes function optimization. The scope of the method is to achieve the best trade-off performance between two objectives: annual energy production per square meter of wind park (to be maximized) and cost of energy (to be minimized). Examples of the best solutions found by the method are described and their performance compared with those of commercial wind turbines.

Mechanical sensorless control of PMSM with on-line estimation of stator resistance

Abstract: This paper provides an improvement in sensorless control performance of nonsalient-pole permanent-magnet synchronous machines. To ensure sensorless operation, most of the existing methods require that the initial position error as well as the parameters uncertainties must be limited. In order to overcome these drawbacks, we study them analytically and present a solution using an online identification method which is easy to implement and is highly stable. A stability analysis based on Lyapunov's linearization method shows the stability of the closed-loop system with the proposed estimator combined with the sensorless algorithm. This approach does not need a well-known initial rotor position and makes the sensorless control more robust with respect to the stator resistance variations at low speed. The simulation and experimental results illustrate the validity of the analytical approach and the efficiency of the proposed method.

Analysis and Application of Chorochronic Periodicity in Turbomachinery Rotor/Stator Interaction Computations

Abstract: A methodology for predicting the three-dimensional unsteady aerodynamics of the interaction between two turbomachinery blade rows that are in relative angular motion with one another is described. In this case, the kinematics of the blades introduce a chorochronic (space‐time) periodicity. This periodicity is analyzed in detail, and a mathematically straightforward methodology, based on Fourier series in µ (azimuth) and t (time), is presented for treating the interface between the two rows. These results are implemented in a computational method solving the three-dimensional Favre ‐Reynolds-averaged Navier ‐Stokes equations, with a near-wall wall-normalfree Reynolds-stress model. Only one blade passage per blade row is discretized. At the pitchwise boundaries, phase-lagged periodicity is applied using Fourier series in time. Both the pitchwise boundaries time harmonics and the interface chorochronic tµ harmonics are updated using a low-storage moving-averages technique. Computational results are presented and compared with measurements for a 1 1 -stage turbine, where the two stators have the same number of blades enabling the use of chorochronic periodicity. Sample results are also presented for a transonic inlet guide vane/rotor interaction, illustrating the ability of the interface treatment to handle shock waves.

A piezoelectric motor using two orthogonal bending modes of a hollow cylinder

Abstract: This paper proposes a compact ultrasonic motor with low manufacturing costs, a simpler driving circuit, and scalability. The stator of the motor presented in this paper consists of a hollow metal cylinder, whose outside surface was flattened on two sides at 90 degrees to each other, on which two rectangular piezoelectric plates were bonded. Because the cylinder has a partially square/partially circular outside surface, the stator has two degenerated bending modes that are orthogonal to each other. A wobbling motion is generated on the cylinder when only one piezoelectric plate is excited at a frequency between the two orthogonal bending modes. A rod through a pair of ferrules was used as the rotor of this motor. The prototype motor, whose stator was 2.4 mm in diameter and 10 mm in length, operated at 69.5 kHz, was experimentally characterized, and a maximum torque of 1.8 mNm was obtained.

An approach for sensorless position estimation for switched reluctance motors using artifical neural networks

Abstract: This paper presents a new approach to the sensorless control of the switched-reluctance motor (SRM). The basic premise of the method is that an artificial neural network (ANN) forms a very efficient mapping structure for the nonlinear SRM. Through measurement of the phase flux linkages and phase currents the neural network is able to estimate the rotor position, thereby facilitating elimination of the rotor position sensor. The ANN training data set is comprised of magnetization data for the SRM with flux linkage (/spl lambda/) and current (i) as inputs and the corresponding position (/spl theta/) as output in this set. Given a sufficiently large training data set, the ANN can build up a correlation among /spl lambda/, i and /spl theta/ for an appropriate network architecture. This paper presents the development, implementation, and operation of an ANN-based position estimator for a three-phase SRM.

Methods and apparatus for materials processing

Abstract: Methods and apparatus for processing materials employ two cylindrical members, one mounted within the other, defining an annular processing chamber (44). Preferably, the outer member is stationary (stator) (30), while the inner rotates (rotor) (42). The radial spacing (44) between the stator (30) inner surface (46) and the rotor (42) outer surface (46) is equal to or less than the back-to-back radial thicknesses of the two laminar boundary layers formed upon the surfaces (46).

Segmented arc generator

Abstract: A segmented arc generator is adapted to convert mechanical power such as wind or water power into electrical power at a wide range of wind or shaft speeds. A rotor has a plurality of salient poles disposed about a periphery of a rotor ring. A stator has a stator ring disposed radially about and in close proximity to the rotor ring. The stator ring includes a plurality of stator coils wound on a ferromagnetic structure and having permanent magnets imbedded within the structure. Relative motion between a rotor pole and a corresponding stator coil induces a coil voltage across that coil. A phase controlled converter in electrical communication with the stator coils rectifies the output voltage. A pulse width modulated inverter is in electrical communication with the phase controlled converter for converting the D.C. voltage output by the phase controlled converter to an A.C. voltage of controlled amplitude and phase relationship determined with respect to a voltage waveform present on a connected utility grid. A switching matrix selectively places the coils in series or parallel or a combination of series and parallel connections with respect to one another in response to control signals that are based on present operating conditions of the generator. A boost converter circuit provides and maintains a minimum D.C. voltage to the pulse width modulated inverter when the voltage induced in the coils falls below a threshold value.

Position detection and start-up algorithm of a rotor in a sensorless BLDC motor utilising inductance variation

Abstract: A method of identifying the rotor position of a brushless DC (BLDC) motor and driving a motor smoothly from standstill without any position sensors is presented. This is done by monitoring the current responses to the inductance variation on the rotor position. The rotor position at standstill is detected by comparing the first and second differences of six current pulses injected into every two phases of the motor. Once the motor starts up, a pulse train, composed of long and short pulses, is injected into the commutation phases corresponding to the maximum torque production and the next commutation phases in alternating fashion. It provides not only the torque, but also information about the next commutation timing when the current responses of the long and short pulses cross each other in the same time delay. A controller for a BLDC motor is developed using a PC, digital signal processor (DSP), inverter and communication circuits in order to verify the proposed algorithm experimentally. It shows that the proposed algorithm can drive a BLDC motor smoothly without any vibration or time delay up to medium speed compared with the conventional back-EMF algorithm. Beyond this medium speed, a sensorless algorithm for rotor-position detection is switched to the back-EMF method to drive a BLDC motor at high speed.

Flux observer with online tuning of stator and rotor resistances for induction motors

Abstract: This paper proposes an adaptive flux observer for induction motors, where stator and rotor resistances are estimated in online environments. The variation of motor parameters during operation degrades the performance of the controller and the flux observer. Among the parameters of induction motors, rotor resistance is a crucial one for flux estimation, and stator resistance also becomes critical in the low-speed region. Under the persistent excitation condition, the proposed method estimates the actual values of stator and rotor resistances simultaneously, which guarantees the exact estimation of the rotor flux. The persistent excitation condition is not satisfied when the electric torque of an induction motor is absent due to the lack of rotor currents. Even in this case, the proposed method achieves the correct estimation of the rotor flux. Simulations and actual experiments show that the rotor flux is estimated in all operating conditions and that both resistances converge to their actual values when the electrical motor torque exists.

Variable displacement pump

Abstract: A variable displacement pump has a cam ring, a rotor, a plurality of vanes, a pressure plate and a rear body. The cam ring is accommodated within a pump body. The rotor rotates within the cam ring. The plurality of vanes are inserted retractably into slits formed at regular intervals circumferentially in the rotor. The pressure plate and the rear body carry the cam ring and the rotor. A circular groove communicating to a back pressure inlet bore on a bottom portion of the slits is formed in a suction area on a face of the rear body on a side of the rotor. The groove is communicated via a communication passage to a passage between a power steering gear and a tank T to introduce a working oil after used in the power steering gear.

Rotors produced and driven in laser tweezers with reversed direction of rotation

Abstract: Micrometer size rotors are produced by light induced polymerization of light curing resin. The propeller shaped rotors trapped in laser tweezers are rotated by the trapping light. A rotor is built that changes the direction of rotation by changing its position relative to the focus. The design is based on the very high numerical aperture of the focused light in the tweezers: the light has a large average component of momentum pointing perpendicular to the optical axis, in the opposite direction before and behind the focus. This perpendicular component drives the rotation and the direction changes when the rotor is moving around the focus.

Vibratory loads reduction testing of the NASA/Army/MIT active twist rotor

Abstract: Recent studies have indicated that controlled strain-induced blade twisting can be attained using piezoelectric active fiber composite technology, and that such advancement may provide a mechanism for reduced rotorcraft vibrations and increased rotor performance. In order to validate these findings experimentally, a cooperative effort between the NASA Langley Research Center, the Army Research Laboratory, and the MIT Active Materials and Structures Laboratory has been developed. As a result of this collaboration a four-bladed, aeroelastically-scaled, active-twist model rotor has been designed and fabricated for testing in the heavy gas test medium of the NASA Langley Transonic Dynamics Tunnel. Initial wind tunnel testing has been conducted to assess the impact of active blade twist on both fixed- and rotating-system vibratory loads in forward flight. The active twist control was found to have a pronounced effect on all system loads and was shown to generally offer reductions in fixedsystem loads of 60% to 95%, depending upon flight condition, with 1.1o to 1.4o of dynamic blade twist observed. A summary of the systems developed and the vibratory loads reduction results obtained are presented in this paper.

Centrifugal turbine for breathing-aid devices

Abstract: The invention concerns an electric turbine (1) comprising a turbine rotor (4, 7), a turbine stator (2, 3), an electric motor member (5, 6) for driving the rotor (4, 7) in rotation relative to the stator (2, 3), and having the following features: the turbine stator (2, 3) comprises a stator body defining a compression chamber (12); the turbine rotor (4, 7) includes a plurality of blades (26, 27) integral with a shaft (4) mounted coaxially rotating in the body (2, 3) of the turbine stator; the electric motor member (5, 6) comprises a toroidal motor stator (6) housed in a motor housing (16, 23) of the turbine stator (2, 3), at the center of the toroidal compression chamber (12) and a motor rotor (5) mounted on the shaft (4) of the turbine rotor, axially opposite the motor stator (6).