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Showing papers on "Rotor (electric) published in 1994"


Proceedings ArticleDOI
02 Oct 1994
TL;DR: In this paper, a position sensorless control scheme for a doubly excited induction machine is proposed, which uses only the rotor voltages and currents as the feedback signals, which substantially reduces the costs and enhances the reliability.
Abstract: A novel control strategy to realize decoupled control of torque and reactive power for a doubly excited induction machine using a position sensorless scheme is proposed. The critical issues related to the torque angle estimation and control for a doubly excited induction machine are discussed. Compared to the other position sensorless schemes for a doubly fed machine, the proposed control method uses only the rotor voltages and currents as the feedback signals, which substantially reduces the costs and enhances the reliability of the position sensorless control of a doubly fed AC machine. Computer simulation and experimental results are given to verify the position sensorless control scheme. >

317 citations


Patent
16 Dec 1994
TL;DR: In this paper, the stator response at the signal frequency is detected to provide a correlation between the response at a signal frequency and the rotor position by a heterodyne detection process, by mixing signals at signal frequency with the measured stator currents, and filtering the mixed signals to isolate the signal indicative of rotor position.
Abstract: Power is provided to the stator windings of an AC machine which includes a component at the fundamental drive frequency for the machine and a superimposed signal component which is at a substantially higher frequency than the drive power. The rotor has saliencies which result in a change in impedance as seen at the stator windings to the high frequency excitation signal as a periodic function of rotor rotational position. Such saliencies are inherent in some permanent magnet synchronous and all synchronous reluctance machines, and may be provided by appropriate modification of the rotor of induction machines. The stator response at the signal frequency is then detected to provide a correlation between the response at the signal frequency and the rotor position. The detection of the response at the signal frequency is preferably carried out by a heterodyne detection process, by mixing signals at the signal frequency with the measured stator currents, and filtering the mixed signals to isolate the signal indicative of the rotor position. Conventional squirrel cage induction motors can be provided with sufficient spatial variations in the stator winding impedance as a function of rotor position in various ways, including varying the depth and/or width of the slots over the rotor conductive bars, by varying the cross-section of the bars, or by filling or partially filling some of the slots.

198 citations


Journal ArticleDOI
20 Jun 1994
TL;DR: In this article, a method for the estimation of changes in stator resistance during the operation of the induction machine is presented, which is implemented using proportional integral control and fuzzy logic control schemes.
Abstract: Direct torque control (DTC) of induction machines uses the stator resistance of the machine for estimation of the stator flux. Variations of stator resistance due to changes in temperature or frequency make the operation of DTC difficult at low speeds. A method for the estimation of changes in stator resistance during the operation of the machine is presented. The estimation method is implemented using proportional-integral (PI) control and fuzzy logic control schemes. The estimators observe the machine stator current vector to detect the changes in stator resistance. The performance of the two methods are compared using simulation and experimental results. Results obtained have shown improvement in DTC at low speeds.

187 citations


Journal ArticleDOI
TL;DR: Several types of AC bearingless motors have been proposed in this article, which have conventional four-pole stator windings and additional two-pole windings, whose currents produce radial forces acting on the rotor.
Abstract: Several types of AC bearingless motors are proposed. These bearingless motors have conventional four-pole stator windings and additional two-pole windings, whose currents produce radial forces acting on the rotor. General expressions of the machine inductances and radial forces are derived for the cylindrical rotor and salient-pole motors. No-load characteristics of laboratory squirrel-cage induction and reluctance-type synchronous bearingless motors are provided. The test motors were successfully driven by the control circuits. >

184 citations


Journal ArticleDOI
TL;DR: In this paper, a rigorous mathematical method is proposed for dealing with the ramp-rate limits in unit commitment and the rotor fatigue effect in economic dispatch, where the Lagrangian relaxation method is used to generate the unit commitment schedule with relaxed power balance constraints and a network model is adopted to represent the dynamic process of operating a unit over the entire study time span.
Abstract: In this study, a rigorous mathematical method is proposed for dealing with the ramp-rate limits in unit commitment and the rotor fatigue effect in economic dispatch An iterative procedure is employed to coordinate the unit commitment and the power dispatch for obtaining an economical solution within a reasonable time The Lagrangian relaxation method is used to generate the unit commitment schedule with relaxed power balance constraints A network model is adopted to represent the dynamic process of operating a unit over the entire study time span, as the required unit commitment schedule can be achieved by searching for the shortest path in the network In order to find the global optimal solution for the economic dispatch problem within personal computer resources, a piecewise linear model is used for thermal units Furthermore, linear programming is used in optimizing the benefits of ramping the units, with low operating cost against the cost of shortening the service life of the turbine rotor In this regard, linear programming is used to dispatch the power generation among committed units by considering a ramping penalty for the fatigue effect in rotor shafts, while preserving the operational constraints of the system as well as the generating units >

170 citations


PatentDOI
TL;DR: In this paper, a battery monitoring and charging system capable of determining when charging conditions are favorable, thereby adjusting the charging level to maximize fuel saving is presented, which increases the alternator field current to charge a battery during vehicle deceleration so that vehicle momentum, instead of engine power, is used to torque the shaft.

159 citations


Patent
09 Feb 1994
TL;DR: An artificial heart pump comprises a cylindrical stator provided between the inner surface of a casing and a rotor, and a rotating magnet and a stationary magnet differing in length in their N-S pole directions provided on the rotor and the stator.
Abstract: An artificial heart pump comprises a cylindrical stator provided between the inner surface of a casing and a rotor so as to establish a blood flow channel between the outer surface of the stator and the inner surface of the casing, and a rotating magnet and a stationary magnet differing in length in their N-S pole directions provided on the rotor and the stator with their N-S pole directions aligned parallel with the axis of rotation, the boundary between the N and S poles of the rotating magnet being positioned closer to a pivot than the boundary between the N and S poles of the stationary magnet.

143 citations


Patent
28 Sep 1994
TL;DR: In this article, an improved high pressure gas generator rotor for a gas turbine engine is described, in which a tie rod of unitary construction provides an axial compressive load across a plurality of nonbolted compressor and turbine components arranged in rotational driving arrangement, for example, by face splines and rabbets.
Abstract: An improved high pressure gas generator rotor for a gas turbine engine is disclosed in which a tie rod of unitary construction provides an axial compressive load across a plurality of non-bolted compressor and turbine components arranged in rotational driving arrangement, for example, by face splines and rabbets. An interim compressive load path solely through the compressor rotor portion is automatically provided upon relaxation of the operational compressive load in the rotor to maintain mechanical integrity of the compressor and facilitate assembly and maintenance activity. An anti-rotated midspan locknut on the tie rod obviates the need for additional, special tooling configured to clamp the compressor components during disassembly of the turbine.

140 citations


Patent
09 Jun 1994
TL;DR: In this paper, a hybrid alternator with a stator and a rotor is described, with the rotor having longitudinally separate wound field (24) and permanent magnet (38) rotor portions.
Abstract: A hybrid alternator includes a stator (10) and a rotor (20), with the rotor (20) having longitudinally separate wound field (24) and permanent magnet (38) rotor portions. A rotor excitation circuit applies a forward polarity to the wound field rotor portion (24) to increase output in a boosting mode at low RPMs and a reverse polarity to decrease output at high RPMs in a bucking mode to maintain a constant voltage output. Alternative embodiments combine a magnetic flux concentrating design for efficient low speed operation with integral strength for high speed capability. Dual voltage output is provided using only one stator winding. A three state voltage regulator allows voltage regulation without inducing reverse currents onto the power bus in the lightly loaded or no battery conditions. The regulator has automatic interlocking to automatically turn on and off without risk.

138 citations


01 Jan 1994
TL;DR: In this article, the authors focus on methods of achieving direct field orientation (DFO) of induction machines based on closed-loop, stator, and rotor flux observers which are well suited to both zero and very high-speed operation.
Abstract: This paper focuses on methods of achieving direct field orientation (DFO) of induction machines based on closed-loop, stator, and rotor flux observers which are well suited to both zero and very high-speed operation. Both observer topologies are dominated by a current model at zero and low speeds, and a voltage model at high speeds. Application of such rotor and stator flux observers to both stator and rotor direct field orientation is presented, including experimental results for three different methods. The influence which flux regulation has on parameter sensitivity of the complete DFO system is analyzed. A rotor-flux-regulated and -oriented system is shown to be sensitive to leakage inductance under high slip (i.e., field weakened) operation

132 citations


Patent
Daniel Lerner1, Peter Masak1
04 May 1994
TL;DR: In this article, an integrated modulator and turbine-generator includes a turbine impeller which is directly coupled by a drive shaft to a modulator rotor downstream from the impeller.
Abstract: An integrated modulator and turbine-generator includes a turbine impeller which is directly coupled by a drive shaft to a modulator rotor downstream from the impeller. The modulator rotor is further coupled by a drive shaft and a gear train to a three phase alternator downstream of the modulator rotor. The modulator stator blades are arranged downstream of and adjacent to the modulator rotor and the alternator is provided with a Hall effect tachometer. The turbine impeller directly drives the modulator rotor and the alternator generates power. The speed of rotation of the modulator rotor is adjusted by reference to the speed of rotation of the alternator as indicated by the tachometer and to a reference frequency. A control circuit including an electromagnetic braking circuit coupled to the tachometer and the stator windings of the alternator stabilizes the alternator speed and thus the rotor speed and modulates the rotor to obtain the desired frequency of the mudborne pressure wave by selectively shorting the stator windings of the alternator. During periods when braking is not applied, the alternator generates power for control and sensor electronics.

Proceedings ArticleDOI
13 Feb 1994
TL;DR: The switched reluctance motor (SRM) as discussed by the authors was developed for aircraft engine starter/generator applications, and it operates as a generator as well as a motor, which is unique in its operation as generator compared to other machines.
Abstract: The switched reluctance motor (SRM) is being developed for aircraft engine starter/generator applications. In these applications the SRM operates as a generator as well as a motor. This development is taking place because the SRM is unique in its operation as a generator compared to other machine types in that it does not employ permanent magnets or a field winding on its rotor. Thus the SRM generator does not possess the inherent problem of generating into a shorted winding like the permanent magnet machine (you cannot turn off the excitation). Because the SRM generator does not employ permanent magnets or a field winding, it is important to consider the nature of its excitation during generating in order to understand its operation and limitations. This is especially true during load faults or when generating AC. Also, as with all electric machines, the SRM as a generator is the dual of the SRM as a motor. This duality, in the case of the SRM, carries over into the control of the machine. >

Patent
08 Jun 1994
TL;DR: In this article, an AC dynamo-electric machine (10) comprising isolated dual stators (50 and 50B and 50C), each both concentrated windings energizable with single-phase AC, and main windings (53) and a single high inertia sleeve (75) and drive plate (74 and 74A) connected to a rotor shaft (70 - 73A).
Abstract: The invention comprises a versatile AC dynamo-electric machine (10) comprising isolated dual stators (50 and 50B and 50C), each both concentrated windings (53C) energizable with single-phase AC, and main windings (53) and a single high inertia sleeve (75) and drive plate (74 and 74A) connected to a rotor shaft (70 - 73A). The sleeve contains independent electrical rotors (80 and 80A), one for each stator. Each rotor has an innermost layer (82) of magnetizable permanent magnetic material in which the concentrated coils in the stator produce a desired pattern of magnetic poles reacting with the rotating field of the main windings. The machine can function a) as a synchronous AC motor, or b) a constant frequency output dual AC generator or c) as an AC motor-generator with long ride-through time. A UPS system (100) comprises the machine (10) in the motor-generator mode, with clutch means (124) to connect an engine (114) to the rotor shaft (73A) to start the engine.

Proceedings ArticleDOI
02 Oct 1994
TL;DR: A rotor position detection scheme which utilizes the characteristics of the synchronous reluctance motor, aimed at providing rotor position information particularly at low rotor speed, even at zero rotor speed is proposed.
Abstract: A rotor position detection scheme which utilizes the characteristics of the synchronous reluctance motor is proposed. In particular, the dependence of the self and mutual inductances on the rotor position is utilized. The motor currents are controlled by a transistor inverter in the manner of hysteresis current control. The inverter switching creates ripples in the phase currents. The rate change of current in the ripples is then detected and converted to a rotor position signal. The proposed scheme is aimed at providing rotor position information particularly at low rotor speed, even at zero rotor speed. Numerical analysis of the rate change of the phase current of the synchronous reluctance motor is also discussed. >

Patent
13 Oct 1994
TL;DR: In this article, a system for separating a fluid having heavier and lighter components is described, which includes a rotor having a rigid mounting member and an elastic diaphragm attached to the mounting member.
Abstract: A system for separating a fluid having heavier and lighter components. The system includes a rotor having a rigid mounting member and an elastic diaphragm attached to the mounting member, the diaphragm defining a chamber. The system also includes a chuck for holding the rigid mounting member of the rotor and for spinning the rotor around an axis. The pressure of a control fluid, preferably a control gas, disposed adjacent the rotor's diaphragm is varied in order to control the volume of the rotor. Pressurizing the control gas causes fluid to flow out of the rotor; applying a vacuum to the diaphragm draws fluid into the rotor.

Journal ArticleDOI
TL;DR: An approach is presented to the speed control of permanent magnet synchronous motors without mechanical transducers through the instantaneous stator flux position and an estimated value of the load angle through a closed-loop state observer.
Abstract: In the present paper an approach is presented to the speed control of permanent magnet synchronous motors without mechanical transducers. The rotor position, which is an essential component of any vector control scheme, is calculated through the instantaneous stator flux position and an estimated value of the load angle. A closed-loop state observer is implemented to compute the speed feedback signal. Experimental results on a laboratory tested motor drive are presented to validate the proposed procedure. >

Proceedings ArticleDOI
02 Oct 1994
TL;DR: In this article, a bearingless motor with the principles of permanent magnet type synchronous motors is proposed, in which additional 2-pole windings are wound together with 4-pole motor windings in stator slots.
Abstract: Super high-speed and high-power electric machines are required for turbomolecular pumps and spindle drives. High rotational speed and high power drives can be achieved with bearingless motors. In this paper, a bearingless motor with the principles of permanent magnet type synchronous motors is proposed. High power factor and high efficiency can be expected in permanent magnet type bearingless motors. The proposed bearingless motor is a 4 pole permanent magnet synchronous motor, in which additional 2-pole windings are wound together with 4-pole motor windings in stator slots. With currents of 2-pole windings, radial magnetic forces are produced to support a rotor shaft. Principles of radial force production of surface-mounted permanent magnet bearingless motors are analyzed mathematically. It was found that radial forces are efficiently produced by employing thin permanent magnets on the surface of rotor iron core. A test machine was built in order to measure inductance functions as well as relationships between voltages and currents.

Patent
21 Jan 1994
TL;DR: In this article, a cylindrical barrel is inserted into a motor stator and a motor rotor is coupled to the pump's impeller to prevent blood from being impelled more than once around the impeller chamber periphery.
Abstract: A centrifugal blood pump features a pump assembly (14) including a cylindrical barrel insertable into a motor stator (12). The barrel contains a motor rotor (58) which is directly coupled to the pump's impeller (40). The barrel can be oriented and locked in the motor stator in many different angular orientations. Hemolysis is prevented in spite of high speed operation by reducing the clearance between the impeller (40) and the impeller chamber, radiusing the edges of the impeller blades, and providing a deflector to prevent blood from being impelled more than once around the impeller chamber periphery. An efficient releasable locking mechanism is also disclosed, as is a preferred method of assembling the pump assembly with close tolerances.

Journal ArticleDOI
TL;DR: In this article, the spinup dynamics of axial dual-spin spacecraft composed of two rigid bodies: an asymmetric platform and an axisymmetric rotor parallel to a principal axis of the platform are considered.
Abstract: We consider spinup dynamics of axial dual-spin spacecraft composed of two rigid bodies: an asymmetric platform and an axisymmetric rotor parallel to a principal axis of the platform. The system is free of external torques, and spinup of the rotor is effected by a small constant internal axial torque. The dynamics are described by four first-order differential equations. Conservation of angular momentum and the method of averaging are used to reduce the problem to a single first-order differential equation which is studied numerically. This reduction has a geometric counterpart that we use to simplify the investigation of spinup dynamics. In particular, a resonance condition due to platform asymmetry and associated with an instantaneous separatrix crossing is clearly identified using our approach.

Patent
26 Jan 1994
TL;DR: In this paper, a fly bearing is used to assist the rotary movement of the rotor and pick up externally applied forces and moments in a multiple pole synchronous generator for gear-free horizontal axis wind power systems.
Abstract: The multiple pole synchronous generator is for gear-free horizontal axis wind power systems. The generator acts as the inner or outer rotor and includes a stator (8) and a rotor (11). The stator (8) and rotor (11) are connected to each other by a fly bearing (15). The bearing (15) assists the rotary movement of the rotor and also picks up externally applied forces and moments. Preferably the generator (1) includes, as integral components, a cooler (12), a seal (5), a brake system (6), a clamp box (7), signal transmission interfaces and bearing lubrication.

Patent
19 Sep 1994
TL;DR: In this article, a rotary shaft rotatably supported to the casing, a rotor body made of plastic, and a magnetic layer formed on an outer circumferential surface of the rotary body and made of rare earth plastic magnetic material.
Abstract: A miniature electric motor has a stator mounted within a casing and a rotor provided so as to face the stator. The rotor includes a rotary shaft rotatably supported to the casing, a rotor body into which the rotary shaft is inserted, the rotor body being made of plastic, and a magnetic layer formed on an outer circumferential surface of the rotary body and made of rare earth plastic magnetic material. Accordingly, it is possible to obtain a high torque even with a small amount of rare earth plastic magnet and to avoid separation or cracks of the magnetic layer.

Journal ArticleDOI
01 Jul 1994
TL;DR: In this article, the effect of cross magnetisation on the two-axis inductances of a reluctance synchronous machine was investigated by means of finite element analysis and measurements on an actual reluctance machine with a two flux barrier per pole rotor.
Abstract: The performance of a reluctance synchronous machine in terms of torque and power factor depends on the two-axis inductances Ld and Lq of the machine. A finite element analysis method is used to determine these inductances for a reluctance machine with a normal cross-laminated rotor with two flux barriers per pole. By varying the rotor dimensions, the change in the difference and ratio of the inductances is examined. The effect of cross magnetisation on the two axis inductances is investigated by means of finite element analysis and measurements on an actual reluctance synchronous machine with a two flux barrier per pole rotor. The measured torque of the current-controlled reluctance machine drive is also given and compared with calculated results showing the effect of cross magnetisation. Hence, important conclusions are arrived at regarding the rotor design and cross magnetisation effect.

Journal ArticleDOI
TL;DR: In this article, the authors define a stability region that guarantees both rotor angular stability and voltage stability in a differential algebraic equation (DAE) power system model, where the stability region does not intersect the impasse surface, the surface on which the bus voltage variables are not defined as functions of the generator rotor angles.
Abstract: The occurrence of a voltage collapse is often described as a small-signal stability problem resulting from a bifurcation of the equilibrium load flow equations as the bus loads and generator power injections incur small changes. However, during a transient period, a voltage collapse may occur as a bifurcation of the transient load flow equations as the generator rotor angles vary. The purpose of this paper is to address voltage collapse in the general context of a transient stability problem for a differential algebraic equation (DAE) power system model. In particular, we define a stability region that guarantees both rotor angular stability and voltage stability. The stability region does not intersect the "impasse surface," the surface on which the bus voltage variables are not defined as functions of the generator rotor angles. Bifurcation theory is used along with some recent results that characterize the stability boundary for DAE models, to show that an important component of the stability boundary is formed by the trajectories that are tangent to the impasse surface at a fold bifurcation point. An energy function transient stability method is developed that uses a sustained fault trajectory to find the first point of intersection with the impasse surface and then involves solving for the (stability) limiting trajectory that is tangent to the impasse surface at this point. This new transient stability method is somewhat similar in theory to the potential energy boundary surface method. Also, this method can be extended to develop stability estimates for power system models in which the stability region is more complex, possibly constrained by line power flow limits, voltage magnitude limits, etc. >

Journal ArticleDOI
TL;DR: In this article, the aerodynamic performance of a Savonius rotor has been studied by measuring the pressure distributions on the blade surfaces at various rotor angles and tip-speed ratios, and it is found that the pressure distribution on the rotating rotor differ remarkably from those on the still rotor especially on the convex side of the advancing blade, where a low pressure region is formed by the moving wall effect of the blade.
Abstract: The aerodynamic performance of a Savonius rotor has been studied by measuring the pressure distributions on the blade surfaces at various rotor angles and tip-speed ratios. It is found that the pressure distributions on the rotating rotor differ remarkably from those on the still rotor especially on the convex side of the advancing blade, where a low pressure region is formed by the moving wall effect of the blade. The torque and power performances, evaluated by integrating the pressure, are in close agreement with those by the direct torque measurement. The drag and side force performance is also studied.

Patent
Naoya Toida1, Yoshiaki Kotani1, Yoshihiro Iijima1, Junji Okuda1, Yoshihisa Hirose1 
01 Sep 1994
TL;DR: In this paper, a wheel motor for a vehicle is provided in which an electric motor is arranged in a central space defined in a wheel, to rotatably drive the wheel, and a gear reducer is also arranged in the central space of the wheel.
Abstract: A wheel motor for a vehicle is provided in which an electric motor is arranged in a central space defined in a wheel, to rotatably drive the wheel. A gear reducer is also arranged in the central space of the wheel, which has a plurality of gears including a final stage gear having an axial through hole formed therein. The electric motor includes a housing fixed to the vehicle body, a stator secured to the housing, a rotor rotatably fitted in a central space defined in the stator to generate the rotative driving force during rotation thereof, and an output shaft connected to the rotor through the gear reducer as well as to the wheel to be rotatively driven by the rotor, for transmitting the rotating output from the rotor through the gear reducer to the wheel. The output shaft extends through an axial through hole formed in the final stage gear of the gear reducer and an axial through hole formed in the rotor, and is rotatably supported by opposite end portions of the housing.

Patent
13 Jun 1994
TL;DR: In this article, the stator members are positioned such that the ends of the members form first and second planar rings of equal diameter to establish a gap there between the rotor and permanent magnets.
Abstract: An electrical generator has a plurality of C-shaped stator members which are made of magnetically permeable material. Each C-shaped stator member includes a respective stator winding, and the stator members are positioned such that the ends of the members form first and second planar rings of equal diameter to establish a gap therebetween. A flat, ring-shaped rotor defines a periphery, and a plurality of permanent magnets are positioned around the periphery. The rotor is positioned with the magnets of the rotor disposed in the gap defined by the stator members. Consequently, when the rotor is rotated by a prime mover to move the magnets through the gap, an electrical current is induced in the stator windings.


Journal ArticleDOI
TL;DR: In this paper, the dynamic behavior of externally excited rotor/stator systems with occasional, partial rubbing conditions is described. And the results of numerical simulations are presented in the form of bifurcation diagrams, rotor lateral vibration time, base waves, and orbits.
Abstract: This paper outlines the dynamic behavior of externally excited rotor/stator systems with occasional, partial rubbing conditions. The observed phenomenon have one major source of a strong nonlinearity: transition from no contact to contact state between mechanical elements, one of which is rotating. This results in variable stiffness and damping, impacting, and intermittent involvement of friction. A new model for such a transition (impact) is developed. In case of the contact between rotating and stationary elements, it correlates the local radial and tangential ("super ball") effects with global behavior of the system. The results of numerical simulations of a simple rotor/stator system based on that model are presented in the form of bifurcation diagrams, rotor lateral vibration time—base waves, and orbits. The vibrational behavior of the considered system is characterized by orderly harmonic and subharmonic responses, as well as by chaotic vibrations. A new result (additional subharmonic regime of vibration) is obtained for the case of heavy rub of an anisotropically supported rotor. The correspondence between numerical simulation and previously obtained experimental data supports the adequacy of the new model of impact.

Patent
25 Apr 1994
TL;DR: A vertical-axis, high-wind turbine for use with an electrical generator for producing power by converting the energy of wind currents into mechanical, rotational energy, which is then used to operate the electrical generator as mentioned in this paper.
Abstract: A vertical-axis, high-wind turbine for use with an electrical generator for producing power by converting the energy of wind currents into mechanical, rotational energy, which is then used to operate the electrical generator. Fixed, stationary stators, while providing significant structural integrity, direct currents having horizontal components into a rotor assembly, where the rotors of this assembly are responsive to the currents by imparting rotation upon a central vertical shaft. Both stators and rotors are designed with functional curved blades for greater efficiency in operation. In fact, the stators are designed with a double-curve which in many ways, discussed herein, perform at levels higher than either straight, or single-curved stators. The present turbine is not equipped with any braking system, or feathering system to withstand the high winds; instead, it is capable of actual operation and energy conversion of these high energy-potential winds.

Proceedings ArticleDOI
06 May 1994
TL;DR: In this paper, the Rayleigh-Ritz assumed mode energy method is used to model the distributed piezoceramics and the traveling-wave dynamics of the stator.
Abstract: A piezoelectric rotary ultrasonic motor is modeled for the purpose of predicting, a priori, motor performance as a function of design parameters. The Rayleigh-Ritz assumed mode energy method is used to model the distributed piezoceramics and the traveling-wave dynamics of the stator. Natural frequencies and dynamic modeshapes are obtained for a generally configured motor. Nonlinear normal and tangential interface forces between the rotor and stator are incorporated into the forcing function along with the linear piezoelectric forcing. Given the applied torque, applied axial loading, and piezo drive voltages as inputs to the model, general motor performance measures are obtained--namely speed, input power, output power, and efficiency. The approach presented here provides a general framework for modeling these motors as well as a design tool for optimizing prototypes with the added flexibility of allowing for a wide variety of geometries and materials.