Five-phase fault-tolerant dual-rotor magnetic field modulation motor and design method thereof

Abstract

The invention relates to a five-phase fault-tolerant dual-rotor magnetic field modulation motor, which comprises a stator, an outer rotor and an inner rotor, the stator comprises a stator winding and a stator core, the stator is subjected to modular fault-tolerant setting, armature teeth are separated by fault-tolerant teeth, and the end part of each stator tooth of the fault-tolerant teeth and the armature teeth is split into small teeth to form a modulation pole; armature teeth and fault-tolerant teeth are designed to be unequal in width; the end parts of the inner rotor and the outer rotor are connected through a flange and coaxially output torque; a samarium-cobalt material is used for replacing a neodymium iron boron material at an easily demagnetized part of the motor so as to ensure the reliability of the motor under a high-temperature demagnetization fault; stator windings are concentrated in armature teeth, and high-thermal-conductivity materials are arranged at the ends of the windings and used for directly cooling the windings.

Description

Technical Field

[0001] The invention relates to the field of motor design, and in particular to a five-phase fault-tolerant dual-rotor magnetic field modulation motor design. Background Art

[0002] Against the backdrop of the rapid development of modern industrial technology, traditional hydraulic drive systems and pneumatic drive systems have been transformed into electric drive systems, with motors gradually becoming a key source of power. Equipment in a large number of workplaces has very stringent requirements on weight, volume, efficiency, etc. Most of their electric drive systems are powered by batteries, which have limited one-time energy. Therefore, how to achieve lightweight and high-efficiency design of the system's motors under complex working conditions and a wide speed and torque range, as well as accurate calculation of their losses, is a key technology and core difficulty in this field. Designing ultra-efficient, high-power / torque-density motors will greatly improve the efficiency and power / torque density of the corresponding electric drive systems, thereby increasing the equipment's carrying capacity and range.

[0003] Common drive motors include brushless DC motors, permanent magnet synchronous motors, and switched reluctance motors. In applications where space and energy are limited, torque / power density is an important performance indicator for evaluating system drive motors. When designing a motor, the torque density of the motor can be improved by changing the motor structure and topology under the premise of determining the material. The magnetic field density of new topology motors such as axial flux and transverse flux motors is large, which can effectively improve the magnetic field energy and torque density per unit volume of the motor, but their power factor is small, which will lead to more stringent requirements on the power supply and drive of the system. Dual-rotor motors have been proven to improve the torque density and power factor of the motor at the same time. As a special type of permanent magnet motor, the magnetic field modulation motor not only has the advantages of traditional permanent magnet motors, but also has advantages such as high torque density. It can not only directly improve the torque density by changing its topology, but also use the harmonic torque modulated by itself to further improve the torque density of the motor. At the same time, the pursuit of high torque density is likely to lead to a decrease in the reliability of the electric drive system. Summary of the invention

[0004] In order to ensure that the designed motor has the characteristics of high torque density and high reliability, the present invention provides a novel five-phase fault-tolerant dual-rotor magnetic field modulation motor and gives its design method. The technical solution is as follows:

[0005] A five-phase fault-tolerant dual-rotor magnetic field modulation motor comprises a stator, an outer rotor and an inner rotor. The stator comprises a stator winding and a stator core. The stator is modularly fault-tolerantly arranged. Armature teeth are separated by fault-tolerant teeth. The ends of each stator tooth of the fault-tolerant teeth and the armature teeth are split into small teeth to form modulation poles. The armature teeth and the fault-tolerant teeth are designed with unequal widths. The inner rotor and the outer rotor are formed by folding silicon steel sheets, and the ends are connected by flanges and output torque coaxially. Samarium cobalt materials are used instead of neodymium iron boron materials at the parts of the motor that are prone to demagnetization to ensure the reliability of the motor under high-temperature demagnetization faults. The stator windings are concentrated in the armature teeth, and high thermal conductivity materials are arranged at the ends of the windings to directly cool the windings.

[0006] Furthermore, the stator core is formed by stacking silicon steel sheets, and the windings are concentrated on the armature teeth.

[0007] Furthermore, the high thermal conductivity material is graphite.

[0008] The present invention also provides a design method for the five-phase fault-tolerant dual-rotor magnetic field modulation motor, adopts comparative experiments to determine the parameter design of the armature teeth and the fault-tolerant teeth, and then uses an improved gray algorithm to optimize the parameters including the split tooth structure.

[0009] 1. The design method according to claim 5 is characterized in that the design idea of ​​the armature teeth and the fault-tolerant teeth is to keep the slot opening unchanged, ensure that the increase in the armature tooth width is equal to the decrease in the fault-tolerant tooth width, the armature tooth tip width at the outer air gap is equal to the fault-tolerant tooth tip width, and the armature tooth tip width at the inner air gap is equal to the fault-tolerant tooth tip width, select initial parameters to design two groups of comparative experiments, both groups of studies ensure that the tooth tip width remains unchanged, and observe the changes in the motor output torque and torque pulsation by gradually increasing the tooth body width; the tooth tip width of the second group is larger than that of the first group; select the stator parameters designed when the output torque is maximum and the torque pulsation is minimum, and design a new experimental group until the torque pulsation is as minimum as possible and the motor output torque is as large as possible.

[0010] 2. The design method according to claim 6, characterized in that the improved grey algorithm specifically comprises:

[0011] Select the corresponding design variables, including performance indicators and constraints. The output performance indicators include torque density and motor efficiency. The constraints include the motor's cogging torque, volume, and weight. Select insensitive parameters that have a small impact on the optimization target and sensitive parameters that have a large impact on the optimization target. Optimize the split tooth parameters, including:

[0012] Add three variables, namely, the width between teeth, the width of the fault-tolerant tooth body and the opening of the slot, to the parameters to be optimized;

[0013] The value range of the substitution parameters is given, the parameter range of the split tooth is designed as above, and the remaining parameters are designed according to the corresponding constraints;

[0014] Determine the motor's sensitive parameters and further narrow the parameter range according to the response surface method requirements;

[0015] The non-independent parameters are removed by using constraint conditions, and the constraint conditions include that the amount of permanent magnets remains unchanged before and after optimization;

[0016] The improved grey wolf algorithm is used to optimize the split tooth parameters.

[0017] The five-phase fault-tolerant dual-rotor magnetic field modulation motor provided by the present invention combines the advantages of dual-rotor motors and magnetic field modulation motors, and uses a new process to reduce the volume and weight of the motor, thereby reducing the denominator of the torque density and further improving the torque density of the motor. In order to achieve high torque output of the motor under fault-tolerant operation, a modulatable dual-rotor permanent magnet structure is used to ensure fault-tolerant operation of the motor under demagnetization. For the design between the armature teeth and the fault-tolerant teeth, a comparative experiment is used to perform unequal width design, and the tiger-wolf algorithm is improved to optimize the motor, thereby suppressing the short-circuit current of the motor and improving the fault-tolerant performance of the motor. The motor winding adopts a modular design to improve the efficiency of the motor and the spatial independence of each winding, and the winding is directly cooled by a high thermal conductivity material block located at the end of the winding. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is the schematic diagram of the designed five-phase fault-tolerant dual-rotor magnetic field modulation motor;

[0019] Figure 2 It is a cross-sectional view of the motor assembly.

[0020] Figure 3 It is a hybrid permanent magnet structure.

[0021] The accompanying drawings are as follows

[0022] 1. Modulation pole 2. Outer rotor 3. Inner rotor 4. Inner rotor permanent magnet 5. Winding 6. Outer rotor permanent magnet 7. Fault-tolerant teeth 8. Armature teeth 9. High thermal conductivity cooling block 10. Screws 11. Iron plate bracket 12. Output shaft DETAILED DESCRIPTION

[0023] The five-phase fault-tolerant dual-rotor magnetic field modulation motor is mainly composed of three major structures, which are the outer rotor 2, the stator and the inner rotor 3 from the outside to the inside. There is an air gap between the stator and the outer rotor, and between the stator and the inner rotor, and the inner and outer rotors share a stator. The modulation pole 1 is located in the stator part, which is split from the armature teeth 8 and the fault-tolerant teeth 7. Unlike the traditional dual-rotor magnetic field modulation motor, the stator winding is concentrated in the armature teeth 8, and the fault-tolerant teeth 7 are used to separate adjacent windings; unlike the traditional five-phase fault-tolerant motor, both sides of the stator adopt a split tooth structure, and the inner and outer rotor permanent magnets can modulate the air gap magnetic field. The stator winding adopts a concentrated winding method. When a phase winding of the motor fails, the fault-tolerant teeth 7 can act as a barrier to the normal winding, and the other phase windings can continue to operate in fault-tolerant mode. Compared with the traditional three-phase motor, the fault-tolerant control of the five-phase motor has greater freedom. The winding is located between the inner and outer rotors, and the high thermal conductivity material 9 at the end of the winding is used to directly cool the winding. The high thermal conductivity material 9 is graphite. The outer rotor 2 and the inner rotor 3 are also made of laminated silicon steel sheets. The double rotors have the same number of poles. Both the inner and outer rotors are affixed with permanent magnets, and the permanent magnets on the inner rotor are magnetized in the same direction. The magnetic field emitted by the outer rotor permanent magnet 6 can interact with the stator magnetic field under the modulation of the modulation pole 1; the inner rotor permanent magnet 4 can interact with the stator magnetic field under the modulation of the modulation pole 1. The no-load permanent magnetic air gap flux density is composed of the fundamental magnetic flux density component generated by the permanent magnetic field and the useful harmonic components obtained by the modulation of the modulation pole. The motor stator is fixed to a vertical iron plate bracket 11 by screws 10, and the ends of the inner and outer rotors are fixed together by flanges to rotate synchronously with the output shaft 12.

[0024] The modulation poles of this motor can effectively adjust the harmonic magnetic field that can generate the fundamental wave back electromotive force. The end modulation poles of each stator tooth of the fault-tolerant tooth 7 are split into 4 small teeth to form a total of 40 modulation poles. The end modulation poles of each stator tooth of the armature tooth 8 are split into 4 small teeth to form a total of 40 modulation poles. The use of a split-tooth stator structure can reduce the span of the winding. There is a double-layer air gap between the inner and outer rotors and the middle stator of the motor. The modulation poles on both sides of the stator end can modulate the magnetic field of the inner and outer air gaps respectively. An effective bilateral magnetic field modulation effect is achieved in the hybrid stator structure motor. Taking the outer rotor permanent magnet 2 as an example, the p generated by the outer rotor permanent magnet 2 r After the pole-pair magnetic field is acted upon by Z modulation poles 1, the pole pair number p k,j The following formula should be satisfied:

[0025] p k,j =|kp r +jZ|(k=1,2,3,…j=±1,±2,±3…) (1)

[0027] Stator pole pair number p s The number of magnetic field pole pairs after modulation p 1,-1The magnetic flux density B generated by the five-phase fault-tolerant dual-rotor magnetic field modulation motor in the outer air gap is equal to the magnetic flux density B generated by the five-phase fault-tolerant dual-rotor magnetic field modulation motor in the outer air gap. om It consists of two parts. The first part is the fundamental wave component B of the permanent magnet magnetomotive force of the inner and outer rotors and the air gap permeance. om1 The second part is the harmonic component of the inner and outer rotor permanent magnet magnetomotive force and air gap permeance generated by phase interaction. om3 The interaction is as follows:

[0028]

[0029] In the formula, is the angle between any position on the air gap circumference and the center line of phase A, and θ is the position of the rotor.

[0030] Similarly, the components of the inner air gap magnetic flux density can be obtained. The dual rotor permanent magnet magnetic field and the harmonic / subharmonic magnetic field of the magnetic field modulation can increase the numerator of the torque density, thereby increasing the torque density of the motor.

[0031] Without changing or even reducing the space of the motor system, the mass and flatness of the motor are considered.

[0032] The split tooth design scheme adopted by the present invention is as follows:

[0033] The design idea of ​​the armature teeth and fault-tolerant teeth is to keep the slot opening unchanged and ensure that the increase in the armature tooth width is equal to the decrease in the fault-tolerant tooth width. The armature tooth tip width at the outer air gap is equal to the fault-tolerant tooth tip width, and the armature tooth tip width at the inner air gap is equal to the fault-tolerant tooth tip width. Select the initial parameters to design two groups of comparative experiments. Both groups of studies ensure that the tooth tip width remains unchanged, and observe the changes in the motor output torque and torque pulsation by gradually increasing the tooth width. The tooth tip width of the second group is larger than that of the first group. Select the stator parameters designed when the output torque is maximum and the torque pulsation is minimum, and design a new experimental group until the torque pulsation is as small as possible and the motor output torque is as large as possible.

[0034] Select the corresponding design variables according to the motor's use area, including performance indicators and constraints. The output performance indicators include torque density and motor efficiency. The constraints include the motor's cogging torque, volume, weight, etc. Select insensitive parameters that have little impact on the optimization target, and sensitive parameters that have a greater impact on the optimization target. Specific steps for optimizing split teeth:

[0035] Add three variables, namely, the width between teeth, the width of the fault-tolerant tooth body and the opening of the slot, to the parameters to be optimized;

[0036] The value range of the substitution parameters is given, the parameter range of the split tooth is designed as above, and the remaining parameters are designed according to the corresponding constraints;

[0037] Determine the motor's sensitive parameters and further narrow the parameter range according to the response surface method requirements;

[0038] The non-independent parameters are removed by using constraint conditions, and the constraint conditions include that the amount of permanent magnets remains unchanged before and after optimization;

[0039] The improved grey wolf algorithm is used for parameter optimization.

[0040] The performance of the proposed motor under the initial parameters is used as the standard value to calculate the relative value of each performance of the sample point, and then the relative performance of each is summed according to the weight to obtain the comprehensive weighted performance of the motor at the sample point. An appropriate function form is selected to fit the optimization equation between the weighted performance and the three independent sensitive parameters. Considering the highly nonlinear characteristics of the motor, the present invention adopts a fitting method based on the radial basis function:

[0041] The n independent sensitive parameters of the motor are written as S, as follows:

[0042] S=(h1,h2,…,h k ) (3)

[0043] The BBD layout of k independent sensitive parameters takes 2k+1 sample points, then the weighted performance F(S) when the motor sensitive parameter is expressed as S is:

[0044]

[0045] In the formula, a i represents the coefficient of each basis, ||SS i ||2 represents vector S and S i The second norm of the difference, S i represents the sensitivity parameter vector corresponding to the i-th sample point of the motor, p(||SS i ||2) represents ||SS i The multi-quadratic basis function of ||2 can be expressed as:

[0046]

[0047] Where m is the shape parameter, which can be expressed as:

[0048]

[0049] In the formula, min{||S i -S j ||2} represents the other sample points whose parameter values ​​are closest to the i-th sample point, and k0 is a constant.

[0050] According to the above content, the first response surface fitting is performed, and the fitting range is continuously narrowed through the response surface function to obtain the final weighted performance function F(S).

[0051] The improved gray wolf algorithm is used to find the optimal value of the weighting function and the optimal sensitive parameter. The n wolves in the wolf pack are randomly distributed in space, and the coordinates of the i-th wolf are the position vector S i , substitute it into the weighted performance function F(S), if F(S i ) is the largest, then it is approximately considered that the coordinates of the wolf are also the coordinates of the food. max The distance vector between the jth wolf and the food is:

[0052] d j =bS max -S j (7)

[0053] In the formula, b is a positive random number less than 1, indicating that the wolf cannot accurately determine the location of the food. The three wolves with the smallest distance to the food are called α wolf, β wolf, and γ wolf, respectively. These wolves are called alpha wolves, and their position coordinates are S α , S β , S γ The motor parameters represented by these three position vectors are closest to the most accurate parameters. The remaining wolves that are farther away from the food are called lambda wolves, and the position coordinates of these wolves are taken as S λ1 , S λ2 …, the motor parameters represented by these position vectors deviate greatly from the optimal parameters. The alpha wolf will move on its own and will also call on the lambda wolves to approach the food. The direction of movement of the lambda wolves is affected by the distance between them and the dominants. The distance vector between the jth wolf and the three dominants can be expressed as:

[0054]

[0055] Where a α 、a β 、a γ are all random quantities, indicating that wolf λ cannot accurately determine the position of the leader. After the jth wolf determines the direction of movement, the next step coordinate S jn It can be expressed as:

[0056]

[0057] After each wolf has a new coordinate, it is substituted into the weighted performance function F(S) again, and the location of the food and the allocation of the alpha wolf and the lambda wolf are re-determined according to the new optimization function. With repeated iterations, the wolf pack gets closer to the food step by step. When the number of iterations is large enough, the wolf pack is infinitely close to the food. The coordinates of α in the last iteration can be regarded as the location of the food, that is, the vector coordinate S α is the optimal parameter of the motor, F(S α ) is the best comprehensive weighted performance of the motor.

[0058] The initial positions of α wolf, β wolf, and γ wolf are related to the random layout. The random layout will lead to a large area of ​​unsearched area even after multiple iterations, resulting in a local optimal solution. To avoid the local optimal solution, the γ wolf should be able to explore the location without wolves independently, rather than being affected only by the alpha wolf and the remaining γ wolves, to enhance its autonomous action ability. Adding Levy flight to the coordinates of the γ wolf makes the direction and distance of the γ wolf's movement random, avoiding the situation of a local optimal solution.

[0059] In this way, the split teeth and other parameters of the motor are optimized, and the designed five-phase fault-tolerant dual-rotor magnetic field modulation motor integrates the dual rotor and split-tooth stator structure without increasing the amount of permanent magnets and the space occupied by the motor, thereby achieving higher torque density and air gap magnetic density in the smallest possible volume.

[0060] The inner rotor permanent magnet 4 and the outer rotor permanent magnet 6 of the designed motor use samarium cobalt materials instead of neodymium iron boron materials at the parts where the motor is prone to lose magnetism, that is, using Figure 3 The hybrid excitation structure of half-placed SmCo permanent magnet material and NdFeB permanent magnet material has a symmetrical magnetic circuit distribution. SmCo material still has a good magnetic energy product at a high temperature of 300°C, and can withstand higher temperatures without losing magnetism than NdFeB material, thereby improving the motor torque performance under NdFeB material demagnetization and ensuring the reliability of the motor under high temperature demagnetization faults.

[0061] The direction of the motor flux is determined according to the actual motor flatness to obtain the maximum torque density.

[0062] In summary, this motor has the following five advantages:

[0063] (1) Both sides of the stator adopt a split-tooth structure, which constitutes a modulatable bilateral permanent magnet rotor. While concentrating magnetic field, improving torque density and power factor, it ensures that the motor can still operate reliably in the event of unilateral demagnetization / demagnetization.

[0064] (2) The stator concentrated winding and the unequal width design of the armature teeth and fault-tolerant teeth make the motor have the characteristics of low mutual inductance and large self-inductance, which can reduce the electrical, magnetic and thermal coupling between the motor phase windings when a fault occurs, suppress the short-circuit current of the motor, and improve the fault-tolerant performance of the motor.

[0065] (3) The modulatable double-sided permanent magnet rotor can concentrate magnetic field, improve torque density and power factor, and ensure that the motor can still operate reliably in the event of unilateral demagnetization / demagnetization.

[0066] (4) In order to improve the motor torque performance when the NdFeB material loses magnetism, SmCo material is used instead of NdFeB material in the parts of the motor that are prone to losing magnetism, thus ensuring the reliability of the motor under high-temperature demagnetization failure.

[0067] The five-phase fault-tolerant dual-rotor magnetic field modulation motor is composed of an inner and outer motor, but still has only one mechanical port and one electrical port, so it can achieve the effect of reducing volume, reducing weight and increasing output torque.

[0068] The five-phase fault-tolerant dual-rotor magnetic field modulation motor essentially provides a function equivalent to the mechanical energy conversion of two motors. It can ensure that the middle stator and the inner and outer rotors work in coordination during operation. The inner and outer double rotors are connected together through the end disk, so the inner and outer rotors can rotate in the same direction and speed. Therefore, the motor has the characteristics of a single electrical and single mechanical port structure.

Claims

1. A five-phase fault-tolerant dual-rotor magnetic field modulation motor, comprising a stator, an outer rotor, and an inner rotor. The stator comprises stator windings and a stator core. The stator is modularly fault-tolerant, with armature teeth separated by fault-tolerant teeth. The ends of each stator tooth, both fault-tolerant and armature, are split into small teeth to form modulation poles. The armature teeth and fault-tolerant teeth are designed with unequal widths. The ends of the inner and outer rotors are flange-connected and coaxially output torque. Samarium-cobalt material replaces neodymium-iron-boron material in areas prone to demagnetization to ensure the motor's reliability in the event of high-temperature demagnetization failures. The stator windings are concentrated in the armature teeth, and high-thermal conductivity material is provided at the winding ends for direct cooling of the windings.

2. The five-phase fault-tolerant dual-rotor magnetic field modulation motor according to claim 1, characterized in that: The cores of the inner and outer rotors are made of folded silicon steel sheets, the ends of which are connected by flanges and output torque coaxially.

3. The five-phase fault-tolerant dual-rotor magnetic field modulation motor according to claim 1, characterized in that: The stator core is made of laminated silicon steel sheets, and the windings are concentrated on the armature teeth.

4. The five-phase fault-tolerant dual-rotor magnetic field modulation motor according to claim 1, characterized in that: The high thermal conductivity material is graphite.

5. The design method of a five-phase fault-tolerant dual-rotor magnetic field modulation motor according to any one of claims 1 to 4, characterized in that: The parameter design of armature teeth and fault-tolerant teeth is determined by comparative experiments, and then the improved grey algorithm is used to optimize the parameters including the split tooth structure.

6. The design method according to claim 5, characterized in that: The design idea of ​​the armature teeth and fault-tolerant teeth is to keep the slot opening unchanged, ensure that the increase in the armature tooth width is equal to the decrease in the fault-tolerant tooth width, the armature tooth tip width at the outer air gap is equal to the fault-tolerant tooth tip width, and the armature tooth tip width at the inner air gap is equal to the fault-tolerant tooth tip width. The initial parameters are selected to design two groups of comparative experiments. Both groups of studies ensure that the tooth tip width remains unchanged, and the changes in the motor output torque and torque pulsation are observed by gradually increasing the tooth body width; the tooth tip width of the second group is larger than that of the first group; the stator parameters designed when the output torque is maximum and the torque pulsation is minimum are selected, and a new experimental group is designed until the torque pulsation is as minimum as possible and the motor output torque is as large as possible.

7. The design method according to claim 6, characterized in that: The improved grey algorithm specifically includes: Select the corresponding design variables, including performance indicators and constraints. The output performance indicators include torque density and motor efficiency. The constraints include the motor's cogging torque, volume, and weight. Select insensitive parameters that have little impact on the optimization target, and sensitive parameters that have a greater impact on the optimization target. Optimize the split tooth parameters, specifically including: Add three variables, namely, the width between teeth, the width of the fault-tolerant tooth body and the slot opening, to the parameters to be optimized; The value range of the substitution parameters is given. The parameter range of the split tooth is designed as above, and the remaining parameters are designed according to the corresponding constraints; Determine the motor's sensitive parameters and further narrow the parameter range according to the response surface methodology; The non-independent parameters are removed by using constraint conditions, and the constraint conditions include that the amount of permanent magnets remains unchanged before and after optimization; The improved grey wolf algorithm is used to optimize the split tooth parameters.

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