WO2008051218A2

WO2008051218A2 - Permanent magnet reluctance machine and controller for using the same with a system

Info

Publication number: WO2008051218A2
Application number: PCT/US2006/041491
Authority: WO
Inventors: Nizar Al-Aawar
Original assignee: D & H Global Enterprise, Llc
Priority date: 2006-10-24
Filing date: 2006-10-24
Publication date: 2008-05-02
Also published as: WO2008051218A3; WO2008051218B1

Abstract

A permanent magnet reluctance machine (PMRM) uses electromagnetic interaction and the minimum reluctance principle to generate a developed torque that has wide constant torque to speed characteristics and a higher torque to weight ratio. The PMRM uses an axially laminated rotor with interleaved or alternating layers of permanent magnet and minimum reluctance areas that are separated by flux barriers. In this fashion, the PMRM has the characteristics of a permanent magnet machine and a synchronous reluctance machine.

Description

PATENT COOPERATION TREATY

APPLICATION

PERMANENT MAGNET RELUCTANCE MACHINE AND CONTROLLER FOR USING THE SAME WITH A SYSTEM

SPECIFICATION

A portion of the disclosure of this patent document contains material which is subject to copyright and trademark protection. The copyright and trademark owner has no objection to the facsimile reproduction by anyone of the patent document or the patent disclosure, as it appears in the World Intellectual Property Organization or the official office of any national patent file or records, but otherwise reserves all copyright and trademark rights whatsoever. FIELD OF THE INVENTION

The present invention relates generally to electric motoring devices and electric generating devices. More specifically, it relates to an axially laminated anisotropic (ALA) rotor with interleaved layers of permanent magnets and minimum reluctance material in a permanent magnet reluctance machine (PMRM), the layers being separated by flux barriers. It also relates to such a machine that can be used within the various systems where electric motoring devices and electric generating devices are used, and particularly where electric motoring devices and electric generating devices are used together, including electric vehicles and petroleum- electric hybrid vehicles, also known as hybrid-electric vehicles. Other uses would include avionics, electric generators and electric appliances, among others. It also relates more specifically to a controller for using the PMRM with such a system, the controller being identified as a power management and vehicle control unit

(PMVCU).

BACKGROUND OF THE INVENTION

The demand for economical and more environmentally friendly and fuel- efficient systems has increased in response to growing concerns for a clean environment and saving energy. Vehicles that utilize such systems are known as "hybrid" vehicles. Hybrid vehicles typically incorporate some sort of fueled propulsion power source, such as an internal combustion engine (ICE), with a rechargeable electrical energy storage system. Hybrid vehicles provide more miles per gallon than pure ICEs because the power drive system is more efficient at constant revolutions per minute, hybrid vehicles being low petroleum consuming vehicles which are also low polluting. Thus, hybrid vehicles serve to improve fuel consumption and decrease emissions. With the use of a well-designed electrical propulsion system with a rechargeable electrical energy storage system, the size of the ICE can also be significantly smaller, the length of its useful service life can be greatly extended, and its rate of degradation much reduced over time. Hybrid vehicles are often referred to as petroleum-electric vehicles, but are most commonly referred to as hybrid-electric vehicles (HEV). In addition, the well-designed electrical propulsion system must meet the demands for more fuel efficient systems, additional demands of low weight, compact components and high torque to weight ratios are being placed on developers and manufacturers of HEV systems.

Although there are others, the HEV is typically designed in one of two well- known ways, each defined by the way in which the electric and combustion portions of the vehicle drive-train are utilized in relation to one another. These are often referred to as "series" hybrid or "parallel" hybrid design. Hybrid vehicles may also be configured to utilize both series and parallel arrangements together. Such HEV systems are currently known as "complex" hybrid vehicles.

The series hybrid design uses an ICE that is not directly connected to the vehicle drive-train. Instead, the ICE powers an electrical generator. That is, electricity from the generator is fed to the motor, or motors, that propel the vehicle. Any excess energy that is generated by the ICE is used to charge a bank of onboard batteries. The advantage of the series hybrid is its simplicity due to the absence of any direct mechanical link between the ICE and the drive-train. This makes the series hybrid vehicle a most efficient vehicle for city driving and where driving may require many stops and starts. In such vehicles, the ICE can deliver power at a constant and efficient rate. For long distance or highway driving, losses in the electric transmission become more apparent, thus making the series hybrid vehicle less desirable for that type of driving. However, with the use of proper power management, even series configurations can be improved by determining the dominant parameters of either the ICE or the electrical motor in terms of the effect on the total power that can be produced by the vehicle. This concept will be discussed further later in this background of the invention.

In the parallel hybrid vehicle, both the electrical and internal combustion systems are directly connected to the same mechanical transmission. The ICE may serve as the dominant portion of the system and is used for primary power, the electric motor actuating when a power boost is needed. Alternatively, the electric portion of the system may operate alone. Some designs even combine an electrical generator and the motor into one unit, the unit being situated between the ICE and the mechanical transmission. In either the series or parallel hybrid vehicle, the ICE can be a much smaller and more efficient engine that in a conventional vehicle. The reason for this is that the engine can be sized for its average power demand rather than its peak power demand, thus maximizing the efficiency of the ICE as it operates within its range of highest efficiency, the standard ICE being required to operate over a much broader range of speed and power.

In this context, it is evident that by improving the electric propulsion system, and the electric controls and related components of a hybrid vehicle, the overall performance of the vehicle will improve. The choice of the electric motors (EM), or alternators, that are used plays an important role in improving the electrical systems used with the HEV. The alternator is a traditional device for converting mechanical energy to alternating current (AC) electrical energy, and vice versa, through an intermediate transformation of magnetic energy. That is, the alternator is made up of two essential elements - a stationary part called the stator and a rotating part called the rotor. The stator holds a three-phase winding called the armature. The rotor holds the field winding, which is excited by a direct current (DC), which is the field current// or a permanent magnet. The rotor is turned by a prime mover, producing a rotating magnetic field within the machine. This rotating magnetic field induces voltages within the stator windings. These voltages are sinusoidal with a magnitude that depends on the rotor excitation field, thus producing a rotating magnetic field that is rotating at the electrical angular velocity of the rotor. The alternator's electrical frequency is related to the rotor mechanical speed as follows: f= (p/2) x (n/60) where n is the rotor speed in revolutions per minute and p is the number of rotor poles. So the rotation of the rotor coupled with the field current I_f produce a rotating magnetic field that induces currents in the stator windings. On the other hand, a three-phase set of currents, each of equal magnitude and shifted in phase by 120°, flowing in the three-phase windings, produces a magnetic field of constant magnitude rotating at synchronous speed. The interaction between the rotor and the stator's synchronously rotating magnetic fields creates the developed torque of the machine.

In the case of the HEV, a combined motor/generator replaces the conventional separate generator and motor and performs both functions. This combined motor/generator device is referred to here as the PMRM. In this way, the PMRM of the HEV can crank the ICE when starting, provide additional mechanical power for acceleration of the vehicle, and charge the on-board batteries when the vehicle is running at a constant speed. It is essential for the PMRM to have a wide flat torque to speed characteristic and to provide good performance at high speeds. It is also essential for the PMRM to provide high torque to weight ratio as this will provide a wide efficient operating range for the ICE. Furthermore, it also should have a wide range of constant torque to speed characteristics. This will allow the complexity of the machine controller to be reduced, together with its cost. It also improves the performance of the HEV at high speeds which minimizes the use of the ICE and improves fuel consumption. The PMRM must also be very efficient which also improves the performance of the HEV.

For this purpose, the PMRM machine of the present invention would ideally use the electromagnetic interaction and the minimum reluctance principle to generate a developed torque that has wide constant torque to speed characteristics and a higher torque to weight ratio. The machine would also use an axially laminated rotor with interleaved or alternating layers of permanent magnet and minimum reluctance material separated by flux barriers. In this fashion, the machine would have the characteristics of a permanent magnet machine and a synchronous reluctance machine. Thus, the generated torque would be a summation of the interaction between the electromagnetic rotating fields of the stator and rotor and the reluctance torque. The reluctance torque is torque that is generated by trying to align the rotor to make a minimum reluctance path with the stator. The structure of the PMRM, which would use interleaved layers of permanent magnet with layers of minimum reluctance material, would force the flux to path through the layer of minimum reluctance material. The three-phase balance armature currents would set up a rotating magnetic force, thus the minimum reluctance path would keep rotating with it and the rotor would be forced to always turn.

This design would be modeled in a 2D finite element analysis that takes into account non-linearity and saturation effect in the magnetic material through a family of curves approach and it also accounts for the anisotropy resulting from the structure and the type of material used by using a reluctivity tensor in the modeling. The width of the flux path and the shape and volume of the permanent magnet along with the width of a stator tooth would be computed to optimize its performance such as, but not limited to obtaining maximum torque with minimum losses and ripples for all ranges of power and speed. Each stator tooth would contain a rib to counter the stator tooth effect and reduce the space harmonics, thus resulting in cleaner performance characteristics being obtained. Embedded bars of permanent magnet would be used as dampening bars to create back electromagnetic field, or back EMF, in case of disturbance. They could also be replaced with closed conductive loops. Along with the same structure of the PMRM the dimension of the parameters can be changed to suit different applications. The changes can be done to all parameters or any various combination of them. The major parameters are stator tooth width, the width of the flux paths, the width of the flux barriers, the volume of the permanent magnet and the shape of the permanent magnet. For example, for a generation system these parameters are calculated to obtain maximum output power, with minimum ripples and losses.

The PMRM of the present invention would be utilized with a controller, also identified in this application as a power management and vehicle control unit (PMVCU), whereby the power flow within an HEV is quantified and maximized. The PMVCU is an integrated system that is used to control the power management between the ICE and the electrical system. SUMMARY OF THE INVENTION

The machine of the present invention is a PMRM that uses electromagnetic interaction and the minimum reluctance principle to generate a developed torque that has wide constant torque to speed characteristics and a higher torque to weight ratio. The PMRM uses an axially laminated rotor with interleaved or alternating layers of permanent magnet and minimum reluctance areas that are separated by flux barriers. In this fashion, the PMRM combines and improves the characteristics of a permanent magnet machine and a synchronous reluctance machine. The developed PMRM is used in both generating mode and motoring mode. The effects of the material anisotropy on the energy performance characteristics of the PMRM are to direct the flux paths so that reluctance torque is added to the magnetic torque. As a result, the developed PMRM can produce high torque to weight ratios.

In the PMRM of the present invention, the number and the width of flux paths, along with the stator tooth width and shape can be varied to maximize the torque with minimum torque ripple and losses. These effects are evaluated from the simulation of indirectly coupled magnetic field-electric circuit models, which fully accounts for magnetic saturation and space harmonics to a time variant state space model describing the machine drive system. Furthermore, the simulation method fully accounts for non-linearity and saturation effects exhibited in the curved flux barrier regions of the PMRM.

The PMVCU is an integrated system that is used to control the power management between the ICE and the electrical system, including the PMRM. The PMVCU's purpose is to achieve optimum performance by driving both the ICE and the PMRM, and deciding whether the PMRM should function as a motor or as a generator at any given point in time. Use of the PMVCU in conjunction with an HEV system improves efficiencies in the ICE and the PMRM. Use of the PMRM within the HEV system actually reduces the complexity of the PMVCU. It also reduces the use of the ICE, improves fuel efficiency and reduces the number of batteries required. The foregoing and other features of the PMRM, the PMVCU and the exemplary HEV system that uses them in accordance with the present invention will be apparent from the detailed description that follows. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a front, top and right side perspective view of the PMRM constructed in accordance with the present invention.

Fig. 2A is a front, top and right side perspective view of the stator of the PMRM illustrated in Fig. 1.

Fig. 2B is a front, elevational view of the stator illustrated in Fig. 2A. Fig. 2C is a greatly enlarged front elevational view of a portion of the stator shown in Fig. 2A, taken along line 2C - 2C of Fig. 2B, and illustrating a small rise or bump on the representative stator teeth.

Fig. 3A is a front, top and right side perspective and exploded view of the PMRM shown in Fig. 1. Fig. 3B is a greatly enlarged top, front and right side perspective view of a representative rotor plate illustrated in Fig. 3A.

Fig. 4A is a front elevational view of the PMRM shown in Fig. 1.

Fig. 4B is a greatly enlarged partial front elevational view taken along line 4B- 4B of Fig. 4A and showing additional layers of flux barrier and permanent magnet added of one particular embodiment of the PMRM.

Fig. 5 is a front elevational view of the smallest of the four rotor plates shown in Fig. 3A.

Fig. 6 is a front elevational view of the longest of the four rotor plates shown in Fig. 3A. Fig. 7 is a greatly enlarged front elevational view of the rotor plate shown in Fig. 6 and taken along line 7 - 7 of Fig. 6 and illustrating the laminated construction of each of the rotor plates.

Fig. 8 is a greatly enlarged front, top and right side perspective view of the rotor core illustrated in Fig. 3A and taken along line 8 - 8 of Fig. 3A.

Fig. 9A is a schematic representation of an electric vehicle (EV) system using electric power drive by the PMRM only.

Fig. 9B is a schematic representation of a parallel HEV system using combustion power drive with electrical power drive assist by the PMRM. Fig. 9C is a schematic representation of a parallel HEV system using combustion power and using the PMRM as a generator for regeneration of the electrical power supply.

Fig. 9D is a schematic representation of a series HEV system using combustion power and the PMRM as a generator for regeneration of the electrical power supply and as an electrical power drive device.

Fig. 9E is schematic representation of a complex HEV system in accordance with the present invention.

Fig. 10 is a graph illustrating a representative torque ripple profile for a load with optimization of the PMRM of the present invention. Fig. 11 is a graph illustrating a representative torque ripple profile for a load that is not optimized by use of the PMRM.

Fig. 12 is a graph illustrating relatively wide flat torque versus speed performance using the PMRM of the present invention. Fig. 13 is a schematic diagram of one embodiment of a PMVCU that uses the PMRM of the present invention.

DETAILED DESCRIPTION In general, it is to be understood that the drive system analyzed in this detailed description includes a variable frequency carrier sinusoidal pulse width modulated inverter power conditioner and a four pole ALA rotor PMRM. The stator of the PMRM carries an armature winding as in any conventional induction machine but the teeth on the stator are shaped to minimize harmonic distortion. The PMRM rotor is constructed with axial magnetic laminations interleaved with insulation layers in flux barrier segments. Hence, "material" anisotropy and "structural" anisotropy are incorporated into the rotor design. Although this general description of the PMRM is provided in greater detail in the detailed description that follows, it is to be understood that the PMRM of the present invention is not limited in its application and that its performance characteristics can be varied by varying the size of its several physical components. That is, the PMRM of the present invention can be utilized in many applications and can take many different shapes and sizes, the essential components being described as follows.

Referring now to Fig.1 in greater detail, a PMRM, generally identified 10, that is constructed in accordance with the present invention is shown. The PMRM 10 includes a stator 80 and a rotor, the rotor being constructed of a number of different components. As shown, the rotor is a four pole device. However, it is to be understood that any even number of poles could be used within the PMRM of the present invention. As shown in Fig. 1 , the rotor is comprised of a core element 20, the core element 20 being mountable to a rotational shaft member 30. The rotor is further comprised of four sets of four differently-sized, minimum reluctance flux path regions, or plates 40, 50, 60, 70. The plates 40, 50, 60, 70 are curved members. Furthermore, the plates 40, 50, 60, 70 are preferably of uniform longitudinal length, but of different widths and curvature. As alluded to earlier, the precise physical dimensions of each of the plates 40, 50, 60, 70 is not a limitation of the present invention. The rotor is also comprised of other elements, as will be apparent by reference to Fig. 4B, for example, and by further description later in this application.

As shown in Figs. 2A and 2B, it will be seen that the stator 80 is a cylindrical member having a plurality of inwardly-extending and longitudinally-extending magnetic pole portions, or teeth 82. It is also to be understood that the teeth 82 may be angled in their orientation, that the teeth 82 may be sequenced to vary in height, or varied in other ways that would still come within the scope of the present invention. In the preferred embodiment PMRM 10 of the present invention, the stator 80 has forty-eight such teeth 82, the exact number of teeth 82 not being a limitation of the present invention. It is to be understood that, although such is not shown in the drawings, there are armature coil windings about the stator 80 and between the teeth 82 as in any other three-phase electrical inductor. A relatively large, open axial area 81 is defined within the plurality of teeth 82, this axial area 81 forming the area within which the assembled rotor elements 20, 30, 40, 50, 60, 70 are rotatably supported.

Each tooth 82 of the stator 80 includes a proximal tooth portion 83 that lies closest to the cylindrical outer shell 84 of the stator 80. See Fig. 2B. Each tooth 82 also includes a distal tooth portion 85. On top of the inwardly-directed surface of each distal tooth portion 85 is a longitudinally-extending rib 86. See Fig. 2C. As referred to earlier, this rib 86 is provided in the preferred embodiment as an important feature to reduce harmonics during rotation of the rotor elements. It is possible that the rib 86 may be configured as a discontinuous element along the distal tooth portion 85 and still come within the scope of the present invention. It is also possible that the width and/or the length of the stator tooth 82 may be varied, in accordance with any specific application. It is also possible that the tooth 82 profile could be changed and be configured in other shapes, such as an "L-shaped" tooth (not shown) having a plurality of ribs 86 with different and variable dimensions disposed on top of it, or facing inwardly towards the axial center of the stator 80.

Referring now to Fig. 3A, it shows, in exploded format, the PMRM 10 constructed in accordance with the present invention. As shown, the PMRM 10 includes the stator 80 within which are included a number of component parts that comprise the rotor 80 of the PMRM 10. More specifically, it will be seen that the rotor components comprise the rotational shaft member 30 and a four pole core element 20 that is mountable to the rotational shaft member 30. The rotor further comprises four sets of plates, each plate being a curved or arcuate-shaped member. More specifically, in this preferred embodiment it will be seen that there are four sets of differently-dimensioned plates. For example, the largest plates 40 that lie closest to the core element 20 each includes a plurality of permanent magnets 48 that are embedded within the plate 40. Similarly, successively smaller plates 50, 60, 70 are positioned effectively concentrically within the largest plate 40 and in that order. Each such plate 50, 60, 70 includes a corresponding set of permanent magnet rods 58, 68, 78, respectively. The permanent magnets 48, 58, 68, 78 are used as dampening bars to create back EMF in case of disturbance. It is to be understood, however, that the magnet rods 48, 58, 68, 78 could be replaced with conductive loops (not shown) within each of the plates 40, 50, 60, 70, respectively.

The arrangement of each plate 40, 50, 60, 70 relative to the other plates is best shown in Fig. 4A. Note that each plate 40, 50, 60, 70 is separated by the next adjacent plate by a layer 41 , 51 , 61, 71 , 81. Each layer 41 , 51, 61, 71 is, in the preferred embodiment, comprised of three separate elements. As shown in the partial sectional view of Fig. 4B, the first element is a thin layer 141 , 151 , 161 , that lays immediately adjacent the plates 40, 50, 60, respectively. This first element 141 , 151 , 161 , functions as a flux barrier. The second element is a layer of permanent magnet 241 , 251 , 261, 271 which lays immediately adjacent the thin layer of flux barrier 141 , 151 , 161, respectively. Each second element 241 , 251 , 261, 271 functions as a flux path together with the plates 40, 50, 60, 70, each of which functions as a minimum reluctance flux path. The third element is another thin layer 341 , 351 , 361 , 371 of flux barrier that lays immediately adjacent the next plates 40, 50, 60, 70 of minimum reluctance material.

Although the layers 41, 51 , 61, 71 , 81 are comprised, in the this embodiment, of three separate elements, it is to be understood that it would be possible to alternate the plates 40, 50, 60, 70 with interleaved permanent magnets 241 , 251, 261 , 271 only, but such would not be the most efficient design for the PMRM of the present invention. It is also possible to configure the first element 141 , 151 , 161, of flux barrier and/or the third element 341 , 351, 361, 371 of flux barrier as combined flux barrier and heat sink configurations. Furthermore, the first element 141, 151, 161 , and/or third element 341 , 351 , 361 , 371 of flux barrier could even be comprised of air with interposed flux barrier material in the form of air with flux barrier rods (not shown) that would match the curved contour of the plates 40, 50, 60, 70 and permanent magnet 241 , 251 , 261 , 271 that the flux barrier element would be interposed between. In any event, it is absolutely essential that the curvature of the plates 40, 50, 60, 70, the flux barrier elements 141 , 151, 161, 341 , 351 , 361 , 371 and the permanent magnets 241, 251 , 261 , 271 match in layered contour for optimum performance.

Note also that each plate 40, 50, 60, 70 includes a centrally-disposed set of rod-like permanent magnets 48, 58, 68, 78. Referring specifically to Fig. 3B, and illustrating the point particularly with respect to plate numbered 60, it will be seen that each plate 60 has two opposing edges 62. Each plate 60 also includes a centrally-disposed section 64. Extending longitudinally within the central portion 64 of the plate 60 is a plurality of apertures 66, 67. The apertures 66, 67 are sized somewhat differently from one another and a total of seven apertures are defined within each plate 60. The center aperture 67 is sized somewhat larger to receive a larger diameter permanent magnet rod 69 within it. To either side of the central aperture 67 are three smaller sized apertures 66, each of which is functionally adapted to receive a slightly smaller diametered rod 68 within it. It is also to be understood that other numbers of other-diametered rods could be used within the scope of the present invention, and depending upon the performance characteristics desired or required by the PMRM 10.

Although shown as a solid plate 60 with apertures 66, 67 defined within it, it is to be understood that this is not really how this embodiment of the PMRM plates 40, 50, 60, 70 that are utilized with the present invention are actually fabricated, as will become apparent.

Referring now to Figs. 5 and 6, it will be seen that the smallest plate 70 is also illustrated. The smallest plate shows two opposing side edges 72, a centrally disposed portion 74 and a plurality of apertures 76, 77. Similarly, Fig. 6 illustrates the largest plate 40 having similar edges 42, a centrally disposed area 44 and centrally-disposed apertures 46, 47. As shown in the greatly enlarged Fig. 7, it will be seen by carefully examining one edge 42 of the largest plate 40 that each plate is actually comprised of a plurality of laminations 43 of minimum reluctance material. In this embodiment, there are twenty such laminations per plate. It is to be understood that other numbers of laminations may be used per plate. While adding additional laminations minimizes eddy currents, such is done at greater manufacturing cost. The present invention is not limited to the precise number of laminations disclosed herein. Accordingly, it will also be understood that, in this embodiment, the permanent magnets are actually embedded within the laminations of each plate.

Referring now to Fig. 8, it shows the core member 20 of the rotor and one edge 42 of it in greatly enlarged fashion. It will be seen that this core member 20 is similarly made up of axially disposed laminations 23 as is the case with the plates 40, 50, 60, 70.

As alluded to earlier, the stator 80 in the illustrated embodiment of the present invention has forty-eight teeth 82. In this embodiment, the smallest rotor plate 70 spans five such teeth 82. The largest rotor plate 40 spans eleven such teeth 82. It is to be understood, however, that the basic design provided here can utilize a stator 80 having a different number of teeth 82 and plates 40, 50, 60, 70 having different dimensions without deviating from the scope of the present invention.

Referring now to Figs. 9A-9E, several schematic representations of the

PMRM as it is used in an EV application, in a parallel HEV application, in a series HEV application and in a complex HEV application are shown. In the basic configuration, as shown in each of the figures, the HEV system 100 is comprised of an internal combustion engine (ICE) 102, a clutch 104, the PMRM 106 and a transmission 108. In a typical vehicle, the transmission drives a differential 114 which, in turn, rotates the wheels 116 of the vehicle. The PMRM, or motor 106, is controlled by certain power electronics 112 and powered by a battery 110.

In Fig. 9A, the EV system 100 is shown to be in its "electric only" mode. That is, the ICE 102 is effectively disconnected by means of an open clutch 104. In this mode, only the electrical energy contained within the battery 110 is used to drive the motor 106 by virtue of certain power electronics 112 and the mechanical transmission 108.

Another mode that the motor 106 may be used in is where the ICE 102 is engaged 104 with the motor 106 such that the motor 106 is used to "boost" the drive train transmission 108. This is shown in Fig. 9B. In a third illustration, which is shown in Fig. 9C, the motor 106 is serving strictly as a generator wherein the ICE 102, which is mechanically coupled by means of the clutch 104, is used, in part, to recharge the battery 110, the primary drive mechanism for this mode being the ICE 102.

Although shown in a parallel HEV system 100, it is to be understood that the present invention is not limited to that system. The system 100 could also be arranged as a "series" HEV system, as shown in Fig. 9D, where the ICE 102 is used solely for the purpose of generating electricity for the battery 110, the motor 106 being propelled solely by electric power from the battery 110.

In Fig. 9E, a complex hybrid arrangement is illustrated. As shown, the complex HEV model is a combination of both the series and parallel HEV configuration. It contains several motors 106 and generators 118 connected to the ICE 102, battery pack 110, electric power unit 112 and transmission 108.

A power management and vehicle control unit (PMVCU) is used to control and optimize the performance of both the electrical and mechanical systems of the HEV by utilizing a mechatronic concept of "synergy." Synergy is a quantitative measure of the flow of power in the HEV. A fuzzy logic approach is used to vary the synergy number so that the HEV operates at optimal performance. Most HEV systems in existence today use a programmable logic control (PLC). In this embodiment, fuzzy logic control (FLC) was chosen because it can handle both non- linear data and linguistic knowledge. Although most hybrid systems in existence today use a rule base that is implemented by the PLC, the FLC can accomplish the same task more efficiently and without the use of look-up tables or interpolation. In classical set theory, an element of any universe can be either a member of the set or not. Fuzzy sets, however, are characterized by the fact that an element of the universe of discourse has a so-called degree of membership, determined by a membership function. This fuzziness, a characteristic of human thought and classification processes, can be useful in describing control policies for systems that are difficult to define simply in a precise mathematical fashion. An FLC makes use of fuzzy sets and of the methods of fuzzy logic to represent inputs and outputs. As in the case with many other intelligent control techniques, fuzzy logic is based on an input-output or black box relationship. However, the black box in this case is filled with rules inherited from knowledge of the system. Together, these rules form the rule base that represents the control laws. The main parts (i.e., procedures) of the controller are as follows: (1) fuzzification interface converts the controller inputs to data that the interference mechanism uses to activate and apply rules; (2) rule base that contains the information that an expert would use in controlling the HEV; interference mechanism, which applies the expert's knowledge in making control decisions; and (3) defuzzification interface, which is the transformation of the results from the interference process to crisp (i.e., definite) outputs.

The way that the FLC works and can be implemented is straightforward and intuitive. On the other hand, the mathematical formulation can be cumbersome. In the situation where the integration of the PMRM, which is configured to operate as a motor or a generator, the ICE and the PMVCU, the performance objective lies in the development of a control system that will allow the ICE to operate at or near its peak point of efficiency or at or near its best fuel line by applying the appropriate hardware, operation strategy, and control devices. The design objectives are to integrate these components "seamlessly." In other words, the driver of the HEV should be minimally aware that these components are operating within the HEV. Referring now to Fig. 13, it illustrates the use of the PMVCU, generally identified 400, in a vehicle 408 with a conventional power train 406, the driver 402 chooses accelerator and brake pedal angles based on the difference between the desired speed V_desi∞_d and actual speed V, which is ΔV. The driver also selects a gear to coordinate engine speed and vehicle speed V. In the HEV 408, two accelerator pedals would normally be necessary in order to control the operating points of both the ICE and the PMRM. In the PMVCU 400 of this invention, the fuzzy controller 404 gives the command signals to the PMRM and the ICE. This means that the driver 402 can operate just one input as the driver 402 is normally accustomed to doing. The PMVCU 400, representing power-train management, splits the driver input into two signals, one going to the control unit of the ICE and the other going to the controller of the PMRM. Because of this modification, it is possible to combine both the accelerator pedal input α and brake pedal input β together into one single input y which expresses the driver's desire to accelerate, decelerate or maintain vehicle speed. The brake signal is also required to control brake energy recuperation by using the PMRM 10 as a generator.

Fig. 13 shows the final state of development of the PMVCU 400 in accordance with the present invention. It includes a total of three estimators 410, 412, 414. The ICE optimum estimator 412 determines the optimal operating point of the ICE, given by engine speed (which translates into the actual vehicle speed) and the engine torque output TI_CE.OPT- This value is determined based on the control strategy chosen. In order to assure the necessary engine speed, the proper gear ratio must be chosen as well. In this system, the driver is given the proper gear selection by an audible signal. The optimum estimator 412 is based on the efficiency map or fuel use map of the ICE and is stored in a look-up table in the onboard computer.

The road load estimator 414 determines the actual load of the vehicle 408 as seen by the power train 406. It has to be provided with vehicle information such as the frontal area of the vehicle, drag coefficient, coefficient of rolling resistance, wheel radius, gear ratios, and total vehicle mass. The state of charge (SOC) of the battery pack has to be considered in order to decide whether the required torque contribution of the PMRM is possible or not. If the batteries are completely charged, the PMRM cannot be allowed to operate as a generator. If they are totally discharged, a positive torque contribution will not be possible. An SOC estimator 410 is, therefore, of special interest for this system 400. The PMVCU 400 was designed to be a general purpose fuzzy logic controller because the same controller can work with multiple control strategies.

Referring now to Figs. 10 and 11, it will be seen that the output torque profiles 202, 204 for the optimized and non-optimized HEV application, respectively, are illustrated graphically 200. In the optimized solution as shown in Fig. 10, the torque ripple is 27.7% in comparison to 52% for the non-optimized solution which is illustrated in Fig. 11. It is to be understood, however, that the output torque profiles could vary from those illustrated in Figs. 10 and 11, depending upon the particular characteristics of the PMRM 10 that is used and that the torque profiles are not limited to those illustrated.

Referring now to Fig. 12, it represents, in graphical form 300, how the torque level 304 is sustained up to relatively high speeds through optimization by use of the PMRM of the present invention. The graph 300 represents actual and projected performance data calculated by this inventor. In the application where the PMRM 10 of the present invention is not used, the torque level 314 begins to drop off 312 at about 50 MPH, after which the torque level 314 continues to drop off linearly 316. With the optimized use of the PMRM 10 of the present invention, the torque level 304 does not start to drop off 302 until speeds in excess of 150 MPH are realized, after which torque level tends to drop off rather linearly 306. It is to be understood, however, that the torque levels could vary from those illustrated in Fig. 12, depending upon the particular characteristics of the PMRM 10 that is used and that the torque levels are not limited to those illustrated. In accordance with the foregoing, it will be seen that a new, useful and non- obvious PMRM has been provided that uses electromagnetic interaction and the minimum reluctance principle to generate a developed torque that has wide constant torque to speed characteristics and higher torque to weight ratio. The PMRM of the present invention uses an axially laminated rotor with interleaved or alternating layers of permanent magnet in minimum reluctance areas that are separated, in the preferred embodiment, by flux barriers. In this fashion, the PMRM combines the characteristics of a permanent magnet machine and a synchronous reluctance machine to achieve best performance. The PMRM of the present invention can be used as a power drive mechanism and as an alternative power generation device in an HEV application. The PMRM can also be used in conjunction with a PMVCU, the PMVCU being used with a fuzzy controller to give command signals to the PMRM and to an internal combustion engine that is coupled with the PMRM in the HEV system.

Claims

CLAIMSI claim:

1. A permanent magnet reluctance machine (PMRM) comprising a cylindrically-shaped stator, the stator comprising a plurality of toothed stator magnetic pole portions, and a rotor that is rotatably supported within the stator, the rotor comprising a plurality of rotor pole structures each having, in alternating layered alignment, a plurality of permanent magnet structures and a plurality of minimum reluctance flux path structures.

2. The PMRM of claim 1 wherein said rotor further comprises a flux barrier structure disposed between adjacent layers of permanent magnet structure and minimum reluctance flux path structure.

3. The PMRM of claim 2 wherein each minimum reluctance flux path structure, flux barrier structure and permanent magnet structure is curved.

4. The PMRM of claim 2 wherein each minimum reluctance flux path structure comprises a plurality of laminated sheets of minimum reluctance material with at least one longitudinally-extending permanent magnet imbedded within said sheets.

5. The PMRM of claim 1 wherein the number of flux paths and the width of each path is determined to optimize performance of the PMRM in one or more aspects selected from a group consisting of obtaining maximum torque, obtaining minimum harmonics, obtaining minimum losses, obtaining maximum power, obtaining minimum weight, obtaining quiet operation, and obtaining cleaner electricity, wherein one or more performance constraints are selected from a group consisting of constant speed, constant input power, constant output voltage, and no constraints.

6. The PMRM of claim 1 wherein each tooth on the stator is shaped to optimize performance of the PMRM in one or more aspects selected from a group consisting of obtaining maximum torque, obtaining minimum harmonics, obtaining minimum losses, obtaining maximum power, obtaining minimum weight, obtaining quiet operation, and obtaining cleaner electricity, wherein one or more performance constraints are selected from a group consisting of constant speed, constant input power, constant output voltage, and no constraints.

7. The PMRM of claim 2 wherein the flux barrier structure can be fabricated from materials that have heat sink characteristics to slow the demagnetization and increase the life of the PMRM.

8. A permanent magnet reluctance machine (PMRM) comprising a cylindrically-shaped stator, the stator comprising a plurality of toothed stator magnetic pole portions, and a rotor that is rotatably supported within the stator, the rotor comprising a plurality of rotor pole structures that generate reluctance torque and magnetic torque and are configured to add the reluctance torque to the magnetic torque generated within the PMRM to improve the performance of the machine.

9. A hybrid electric vehicle (HEV) system comprising an internal combustion engine, an electric power storage means, a permanent magnet reluctance machine (PMRM), the PMRM comprising a cylindrically-shaped stator, the stator comprising a plurality of toothed stator magnetic pole portions, and a rotor that is rotatably supported within the stator, the rotor comprising a plurality of rotor pole structures each having, in alternating layered alignment, a plurality of permanent magnet structures and a plurality of minimum reluctance flux path structures, and power electronics electrically connected between the electric power storage means and the PMRM for controlling the PMRM.

10. The HEV system of claim 9 wherein the rotor of the PMRM further comprises a flux barrier structure disposed between adjacent layers of permanent magnet structure and minimum reluctance flux path structure.

11. The HEV system of claim 10 wherein each minimum reluctance flux path structure, flux barrier structure and permanent magnet structure is curved.

12. The HEV system of claim 10 wherein each minimum reluctance flux path structure comprises a plurality of laminated sheets of minimum reluctance material with at least one longitudinally-extending permanent magnet imbedded within said sheets.

13. The HEV system of claim 9 wherein the number of flux paths and the width of each path of the PMRM is determined to optimize performance of the PMRM in one or more aspects selected from a group consisting of obtaining maximum torque, obtaining minimum harmonics, obtaining minimum losses, obtaining maximum power, obtaining minimum weight, obtaining quiet operation, and obtaining cleaner electricity, wherein one or more performance constraints are selected from a group consisting of constant speed, constant input power, constant output voltage, and no constraints.

14. The HEV system of claim 9 wherein each tooth on the stator of the PMRM is shaped to optimize performance of the PMRM in one or more aspects selected from a group consisting of obtaining maximum torque, obtaining minimum harmonics, obtaining minimum losses, obtaining maximum power, obtaining minimum weight, obtaining quiet operation, and obtaining cleaner electricity, wherein one or more performance constraints are selected from a group consisting of constant speed, constant input power, constant output voltage, and no constraints.

15. The HEV system of claim 10 wherein the flux barrier structure can be fabricated from materials that have heat sink characteristics to slow the demagnetization and increase the life of the PMRM.

16. A hybrid electric vehicle (HEV) system comprising an internal combustion engine, an electric power storage means, a permanent magnet reluctance machine (PMRM), the PMRM comprising a cylindrically-shaped stator, the stator comprising a plurality of toothed stator magnetic pole portions, and a rotor that is rotatably supported within the stator, the rotor comprising a plurality of rotor pole structures that generate reluctance torque and magnetic torque and are configured to add the reluctance torque to the magnetic torque generated within the PMRM to improve the performance of the machine, and power electronics electrically connected between the electric power storage means and the PMRM for controlling the PMRM

17. A hybrid electric vehicle HEV system comprising an internal combustion engine, an electric power storage means, a permanent magnet reluctance machine (PMRM), the PMRM comprising a cylindrically-shaped stator, the stator comprising a plurality of toothed stator magnetic pole portions, and a rotor that is rotatably supported within the stator, the rotor comprising a plurality of rotor pole structures each having, in alternating layered alignment, a plurality of permanent magnet structures and a plurality of minimum reluctance flux path structures, and a power management and vehicle control unit (PMVCU) for controlling the PMRM and the internal combustion engine.

18. The HEV and PMVCU system of claim 17 wherein the rotor of the PMRM further comprises a flux barrier structure disposed between adjacent layers of permanent magnet structure and minimum reluctance flux path structure.

19. The HEV and PMVCU system of claim 18 wherein each minimum reluctance flux path structure, flux barrier structure and permanent magnet structure is curved.

20. The HEV and PMVCU system of claim 18 wherein each minimum reluctance flux path structure comprises a plurality of laminated sheets of minimum reluctance material with at least one longitudinally-extending permanent magnet imbedded within said sheets.

21. The HEV and PMVCU system of claim 17 wherein the number of flux paths and the width of each path of the PMRM is determined to optimize performance of the PMRM in one or more aspects selected from a group consisting of obtaining maximum torque, obtaining minimum harmonics, obtaining minimum losses, obtaining maximum power, obtaining minimum weight, obtaining quiet operation, and obtaining cleaner electricity, wherein one or more performance constraints are selected from a group consisting of constant speed, constant input power, constant output voltage, and no constraints.

22. The HEV and PMVCU system of claim 17 wherein each tooth on the stator of the PMRM is shaped to optimize performance of the PMRM in one or more aspects selected from a group consisting of obtaining maximum torque, obtaining minimum harmonics, obtaining minimum losses, obtaining maximum power, obtaining minimum weight, obtaining quiet operation, and obtaining cleaner electricity, wherein one or more performance constraints are selected from a group consisting of constant speed, constant input power, constant output voltage, and no constraints.

23. The HEV and PMVCU system of claim 18 wherein the flux barrier structure can be fabricated from materials that have heat sink characteristics to slow the demagnetization and increase the life of the PMRM.

24. A hybrid electric vehicle (HEV) system comprising an internal combustion engine, an electric power storage means, a permanent magnet reluctance machine (PMRM), the PMRM comprising a cylindrically-shaped stator, the stator comprising a plurality of toothed stator magnetic pole portions, and a rotor that is rotatably supported within the stator, the rotor comprising a plurality of rotor pole structures that generate reluctance torque and magnetic torque and are configured to add the reluctance torque to the magnetic torque generated within the PMRM to improve the performance of the machine, and power electronics electrically connected between the electric power storage means and the PMRM for controlling the

PMRM

25. The HEV and PMVCU system of claim 17 wherein the PMVCU utilizes an integrated fuzzy logic controller and mechatronic synergy principles to provide command signals to the PMRM and to the internal combustion engine to achieve the best performance in the HEV.