Power distribution within electric machine

Abstract

An electric machine includes a stator and a rotor excitable by a magnetic field generated by the stator when receiving a stator current to produce relative motion between the rotor and the stator. The controller is configured to send a stator current through the stator at a current angle measured from a closest one of the poles of the rotor, determine a desired operational output of the electric machine, and determine a desired rotor motion corresponding to the desired operational output of the electric machine. The controller is further configured to calculate a vector control modulation applied to the stator that causes a desired rotor motion, and adjust a current angle of the stator current based on the vector control modulation to cause the rotor to perform the desired rotor motion and achieve a desired operational output of the electric machine.

Description

[0001] This application is a divisional application of the Chinese invention patent application filed on August 2, 2021 (application number: 202180063065.9, invention name: Power distribution within a motor).

[0002] This application claims priority under 35 USC §119(e) to U.S. patent application serial number 63 / 059,929, filed on July 31, 2020, the entire contents of which are incorporated herein by reference. Technical Field

[0003] The present invention relates to electric motors and generators. Background Art

[0004] An electric motor generally includes a stationary component, usually called a stator, and a rotating component, usually called a rotor. Electric current is converted into an electromagnetic field, which exerts a mechanical force or torque between the stator and the rotor, which can be used to do work. Generators work on a similar principle, where mechanical force is converted into electric current. Although mainly described with respect to rotational force or torque, the principles described herein also apply to linear motors. For linear motors, in some embodiments, the rotor acts as the stationary component, while the stator acts as the translating component. Summary of the invention

[0005] This disclosure describes techniques related to wirelessly transmitting power within electric machines.

[0006] An example implementation of the subject matter described in the present disclosure is an electric machine having the following features. The stator defines a plurality of stator magnetic poles with associated stator windings. The rotor defines a plurality of fixed rotor magnetic poles with associated rotor windings. The rotor defines a field that can be excited by the magnetic field generated by the stator windings to produce relative motion between the rotor and the stator. The rotor remains synchronized with the magnetic field generated by the stator during operation. The controller is configured to send current through the stator windings at a current angle measured from the closest one of the rotor magnetic poles. The controller is configured to adjust the current amplitude of the sent current in response to operating conditions. The controller is configured to adjust the current in response to operating conditions.

[0007] In some embodiments, the stator windings include concentrated windings.

[0008] In some embodiments, the stator windings include distributed windings.

[0009] In some embodiments, the stator windings include convex windings.

[0010] In some embodiments, the rotor windings include concentrated windings.

[0011] In some embodiments, the rotor windings include convex windings.

[0012] In some embodiments, the rotor windings include non-overlapping windings.

[0013] In some embodiments, the rotor includes permanent magnets. In some embodiments, the permanent magnets are substantially aligned with the rotor poles.

[0014] In some embodiments, the controller is further configured to excite the stator windings. In some embodiments, the controller is further configured to generate a stator magnetic field in the stator through the excited stator windings. In some embodiments, the controller is further configured to generate a corresponding rotor magnetic field in the ferromagnetic material in the rotor through the stator magnetic field. In some embodiments, the controller is further configured to generate a force tangential to the rotor through a magnetic field offset in the stator. In some embodiments, the controller is further configured to move the rotor through the generated tangential force. In some embodiments, the controller is further configured to maintain the magnetic flux in the rotor through the current in the rotor coil in response to the magnetic field offset. The stator magnetic field and the rotor remain synchronized with each other during operation.

[0015] An example implementation of the subject matter described in the present disclosure is a method of controlling an electric machine. Stator windings of a stator are energized to generate a stator magnetic field within the stator. A corresponding rotor magnetic field within a ferromagnetic material within a rotor is changed by the stator magnetic field. A force tangential to the rotor is generated by the offset of the stator magnetic field. The rotor is moved by the generated tangential force. The stator magnetic field and the rotor remain synchronized with each other during operation. In response to the magnetic field offset, the decay of the magnetic flux within the rotor is resisted by the current in the rotor coil. The current is sent through the stator winding at a current angle measured from the nearest rotor pole. In response to operating conditions, the current amplitude of the sent current is adjusted. In response to operating conditions, the current angle is adjusted.

[0016] An example embodiment of the subject matter described in the present disclosure is a wound field rotor synchronous machine having the following features. The stator defines a plurality of stator poles with associated stator windings. The rotor defines a plurality of rotor poles. The rotor is configured to rotate synchronously with the stator. The rotor includes a rotor winding associated with each rotor pole. The rotor winding is configured to be excited by a magnetic field generated by the stator winding. The excited rotor winding generates a rotor magnetic field. Permanent magnets are embedded in the rotor. A controller is configured to excite the stator winding. The controller is configured to generate a stator magnetic field in the stator by sending a control signal to the stator winding, which is achieved by sending a current through the stator winding at a current angle measured relative to the closest one of the rotor poles. The controller is configured to adjust the current amplitude of the sent current in response to operating conditions. The controller is configured to adjust the current angle in response to operating conditions.

[0017] In some embodiments, the permanent magnets are staggered from the rotor poles.

[0018] In some embodiments, the stator windings include concentrated windings.

[0019] In some embodiments, the stator windings include distributed windings.

[0020] In some embodiments, the stator windings include convex windings.

[0021] In some embodiments, the rotor windings include concentrated windings.

[0022] In some embodiments, the rotor windings include convex windings.

[0023] In some embodiments, the rotor windings include non-overlapping windings.

[0024] The details of one or more embodiments of the subject matter described in this disclosure are set forth in the accompanying drawings and the description below. Other features, aspects, and advantages of the subject matter will become apparent from the description, drawings, and claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] FIG. 1 is a schematic diagram of an example of an electric drive system.

[0026] 2 is a schematic diagram of an example power switch for an electrical winding.

[0027] 3A-3B are perspective and side views of an example electric machine.

[0028] 3C-3D are perspective and side views of an example motor.

[0029] 4 is a side view of an example electric machine.

[0030] 5A is a front view of an example rotor coil.

[0031] 5B is a perspective view of the rotor coil of FIG. 5A .

[0032] 5C is a side view of the rotor coil of FIGS. 5A and 5B .

[0033] 6 is a schematic diagram of an electric motor configured for control according to the present disclosure.

[0034] 7 is a block diagram of an example controller that may be used with aspects of the present disclosure.

[0035] 8 is a flow chart of a method that may be used with aspects of the present disclosure.

[0036] FIG. 9A is a flow chart of a method of responding to a torque increase request according to one aspect of the present disclosure.

[0037] 9B is another flow chart of a method of responding to a torque increase request according to one aspect of the present disclosure.

[0038] 9C is a flow chart of a method for starting a motor according to one aspect of the present disclosure.

[0039] 9D is a flow chart of a method of responding to a torque increase request according to one aspect of the present disclosure.

[0040] FIG. 10 is a graph of average magnetic field strength for various machine configurations.

[0041] Like reference numbers and numerals in the various drawings represent like elements. DETAILED DESCRIPTION

[0042] The present disclosure relates to a field-wound synchronous motor having an electromagnetically directly coupled rotor and stator. The rotor poles of the rotor are topologically and electrically fixed to the rotor surface. The rotor is substantially energy-isolated from the stator components, except for the stator windings. That is, the rotor field is configured to be excited by the magnetic field generated by the stator windings. The stator magnetic field and the rotor remain synchronized with each other during operation. During operation, a controller is configured to send current through the stator and actively adjust the current amplitude and angle in response to current or changing operating conditions. This motor can operate with the efficiency of a synchronous motor without the need for expensive rare earth magnets and without the need for separate brushes or excitation circuits to excite the windings within the rotor.

[0043] The motors described herein are characterized by short-circuited concentrated windings that define the rotor poles. While the use of short-circuited damping bars within the rotor has been proposed for transient damping, they tend to have limited frequency response. In contrast, short-circuited concentrated windings can provide effective transient damping over a wider frequency range. In addition, the various motors described in the present disclosure can take advantage of the inherent nonlinearity and asymmetry that occurs during saturation of the rotor backiron. That is, the inductance within the coil becomes asymmetric, resulting in a net torque.

[0044] Thus, the present disclosure provides subject matter for controlling motors or motors to achieve a variety of different goals. For example, the present disclosure provides systems and methods for achieving desired operating goals without requiring or reducing reliance on rare earth elements or wear elements, such as brushes or excitation circuits, or for improving other operating aspects of the system, such as producing a net torque designed to control undesirable torque ripple.

[0045] 1 shows an electric drive system 100, which includes an electric motor 102 and a motor controller 104 coupled to the electric motor 102. The motor controller 104 is configured to operate the electric motor 102 to drive a load 110. The load 110 may be an additional gear train, such as a gear set, a wheel, a pump, a compressor, or another motor, wherein multiple motors may be linked and run in parallel.

[0046] The electric motor 102 has an output shaft 107 that is rotatable relative to a motor housing 105, which is considered to be a reference relative to the rotation and other movements of the motor components. In use, the output shaft 107 can be coupled to a load 110, and when electrically activated by appropriate power and signals from the motor controller 104, the electric motor 102 can transfer rotational power to the load 110. The output shaft 107 can extend through the motor and be exposed at both ends, which means that rotational power can be transferred at both ends of the motor. The motor housing 105 can be rotationally symmetrical about the axis of rotation of the output shaft 107, but can be of any external shape, and can generally include a means for fixing the housing to other structures to prevent the housing from rotating during operation of the motor.

[0047] The electric motor 102 includes an active magnetic component 106 such as a stator and a passive magnetic component 108 such as a rotor. For illustrative purposes, hereinafter, a stator is used as a representative example of an active magnetic component and a rotor is used as a representative example of a passive magnetic component.

[0048] The rotor 108 is associated with the stator 106 and may be disposed within the stator 106, such as in an internal rotor radial gap motor, or parallel to the stator, such as in an axial gap motor, or in a linear motor. As described more fully below, properly controlled electrical activity in the stator 106 drives the motion of the rotor 108. The rotor 108 is rotationally coupled to the output shaft 107 so that any rotational component of the resultant rotor motion is transmitted to the output shaft 107, causing the output shaft 107 to rotate. The stator 106 is fixed to the electric motor 102 so that during operation, the rotor 108 moves around the stator 106 or parallel to the stator 106.

[0049] Current flowing through the loop of wire will produce a substantially uniform magnetomotive force (MMF), thereby generating motor poles within the area wrapped or surrounded. In a typical motor, this loop has a diameter sufficient to carry the desired current load, but is thin enough so that the skin depth of the drive frequency completely penetrates the loop. Many turns or overlapping loops of wire can be used to increase the magnetic field strength of the poles. This topology is often referred to as a wound field pole. Such a set of overlapping loops is called a coil. For the purposes of this disclosure, multiple coils acting together within a stator or rotor are referred to as windings. In some cases, the coils can overlap and surround multiple teeth on the rotor or stator. Such overlapping coils can be called an armature or distributed winding. The pole is the magnetic center of such a distributed winding, and therefore, depending on the drive current flowing through the winding, the pole can move relative to the individual coils within such a distributed winding.

[0050] The stator 106 defines a plurality of stator poles with associated electrical windings, and the rotor 108 includes a plurality of rotor poles, such as the examples shown in more detail throughout the present disclosure. The rotor 108 and the stator 106 together define a nominal air gap between the stator poles and the rotor poles, such as the examples shown in more detail throughout the present disclosure. The rotor 108 can move relative to the stator 106 along a motion direction.

[0051] FIG. 2 shows another example power switch 200 for a single electrical winding 132. The power switch 200 may have an H-bridge circuit including four switch elements 202a, 202b, 202c, 202d, with the electrical winding 132 at the center of the H-shaped configuration. The switch elements 202a, 202b, 202c, 202d may be bipolar or FET transistors. Each switch element 202a, 202b, 202c, 202d may be connected to a respective diode D1, D2, D3, D4. The diode is referred to as a capture diode and may be a Schottky type. The top of the bridge is connected to a power source, such as a battery Vbat, and the bottom is grounded. The gates of the switch elements 202a, 202b, 202c, 202d may be connected to the controller 104, which may be operable to send a corresponding control voltage signal to each switch element 202a, 202b, 202c, 202d. The control voltage signal may be a DC voltage signal or an AC (alternating current) voltage signal.

[0052] The switching elements 202a, 202b, 202c, 202d can be individually controlled by the motor controller 104 and can be independently turned on and off. In some cases, if the switching elements 202a and 202d are turned on, the left lead of the stator is connected to the power supply and the right lead is grounded. Current begins to flow through the stator, exciting the electrical winding 132 in the positive direction. In some cases, if the switching elements 202b and 202c are turned on, the right lead of the stator is connected to the power supply and the left lead is grounded. Current begins to flow through the stator, exciting the electrical winding 132 in the opposite reverse direction. That is, by controlling the switching elements, the electrical winding 132 can be excited / activated in either direction. Although primarily shown and described as using a single-phase H-bridge configuration, a typical six-switch inverter system can be used for a multi-phase motor without departing from the present disclosure.

[0053] The motor controller 104 can be configured to sequentially operate the switches 134 or 200 for corresponding pole excitation duty cycles to generate magnetic flux across the air gap between the stator poles and the rotor poles, as described in further detail throughout this disclosure. The switches can be controlled to sequentially excite the stator poles to generate a localized attractive force that pulls the rotor. This sequential excitation (or activation) can cause the rotor 108, the output shaft 107, and the load 110 to rotate.

[0054] Motor components and controls are sometimes discussed with reference to the D-axis 312 (examples shown in Figures 3A and 3B) and the Q-axis of the motor rotor and / or stator. The direct axis or D-axis 312 in the motor can be defined as the centerline of the poles perpendicular to the air gap 314 and can be applied to the stator poles 411 (see Figure 4) or the rotor poles 408. As seen in a synchronous reference frame, the rotor can be characterized by the D-axis 312 for each pole. In a wound rotor, the D-axis 312 is the center point of the combined magnetic center of the coils or field windings, regardless of whether the field windings are concentrated in a single large slot or dispersed in multiple smaller slots. The stator poles can be similarly characterized.

[0055] In the magnetic reference frame, the Q axis is orthogonal to the D axis (i.e., it is electrically 90° to the D axis). Typically, a force along the Q axis will produce an electromotive force, such as torque. Topologically, the Q axis of the rotor or stator is usually directly between the two magnetic poles.

[0056] In such a system, the control signal can be converted to DQ axis components, and a third z-axis component also exists and can be described as a signal or magnetic quantity that does not map directly to the D axis or Q axis, for example, a component that is orthogonal to the plane in which the Q and D components lie.

[0057] The current phasor angle 318 is the relative angle between the rotor pole D axis and the magnetic center of the stator (examples are shown in Figures 3A-3D). A positive current phasor angle indicates that the magnetic center of the stator is located in front of the rotor pole in the direction of motion. This situation causes the magnetic center of the stator to "pull" the rotor pole toward the magnetic center of the stator. Similarly, a negative current angle indicates that the magnetic center of the stator is behind the rotor pole. This situation "pulls" the rotor pole in the opposite direction. This negative current phasor angle 318 can be used in braking situations. In some embodiments, a current phasor angle 318 greater than 90° can be used. Such a large phasor current angle 318 can "push" adjacent poles in the direction of motion. Similarly, a current phasor angle 318 less than -90° can be used to "push" adjacent poles in the opposite direction, such as during a braking operation. The following equation can be used to convert the current phasor angle 318 between stationary and synchronous reference frames:

[0058] θ e =(P / 2)θ m (1)

[0059] Among them, θ e is the current phasor angle in the synchronous reference frame, P is the number of stator poles, θ m is the current phasor angle in the stationary reference frame. Regardless of the current phasor angle, it can be decomposed into a D-axis component and a Q-axis component. Typically, for the motors and generators described herein, the D-axis component is used to "charge" or adjust the field within the rotor poles, while the Q-axis component is used to apply force or torque to the rotor poles. Throughout this disclosure, adjusting the current phasor angle 318 and the current amplitude based on operating conditions is described in detail.

[0060] For example, the current angle, duty cycle, and D-axis to Q-axis current injection can all be changed. In some cases, during the D-axis injection period, an instantaneous D-axis current increase of at least 5%, 10%, 20%, or 30% can be achieved relative to the Q-axis current. In some cases, during the injection cycle, the reduction in the resulting current angle can be achieved, for example, 5-60 degrees, 10-50 degrees, 15-45 degrees, or 22.5-67.5 degrees. In some cases, an injection pulse width between 2-70 ms, 5-50 ms, or 10-25 ms can be used. In some cases, a charging duty cycle of 5%, 10%, 15%, or 25% of the total operating time can be used. In some cases, the current angle transition period from D-axis injection to normal operation is 500 µs to 15 ms, 2 ms-12 ms, or 4ms-10 ms, determined by the rotor current dropping to zero. In some cases, the change in current angle is less than 15 degrees, 10 degrees, or 5 degrees. In some cases, during D axis injection, the D axis and Q axis amplitudes are simultaneously varied by at least 5%, 10%, 20%, or 30%. The system can be operated as current control or voltage control. For example, regardless of specific operating parameters, the signal can be injected through a current source inverter, where the current injection pulsation amplitude variation is controlled within a desired tolerance.

[0061] As described throughout this disclosure, the coil structure on the rotor receives power / signals from the stator via an inductive coupling, including at least one ring around the rotor pole. In some embodiments, the rotor coil for the conductive ring forms a capacitor, wherein, in some embodiments, the capacitor is formed, inserted or defined by a specific portion of the rotor coil or conductive ring. In some embodiments, the rotor coil or conductive ring includes a resonant frequency. In some embodiments, the resonant frequency of the rotor coil is within the transmittable range of the magnetically permeable pole or rotor coil material.

[0062] In operation, the rotor poles can generate flux through the D-axis signal on the stator, while the coil structure resists the change in flux on the poles and flows current. The Q-axis signal on the rotor generates torque on the flux motor. In some topologies, such as in salient-pole winding synchronous motors, the maximum torque per ampere (MTPA) occurs at a current angle between 60-90 degrees. For given operating conditions (e.g., torque and speed), the controller establishes the MTPA (e.g., through a lookup table or a model-based estimator), which includes a combination of the D-axis and Q-axis currents (the main control components) that establish the current phasor angle. The current phasor angle can be modulated or oscillated to periodically maintain the desired level of rotor flux, which can be monitored by an observer or estimator, or established through a model-based approach. When the D-axis is modulated to increase the rotor flux, the amplitude of the Q-axis current can be proportionally modulated to limit torque pulsation and reduce any adverse effects of changing the current phasor angle, or to limit changes in the current phasor angle.

[0063] 3A-3B are perspective and side views of an example motor 300. The motor 300 includes a stator 302 that defines a plurality of stator poles with associated stator windings 304. A "motor pole" can be described as a topological portion on a stator or rotor that emits a unipolar magnetic flux across an air gap at a given point in time. When determining the number or location of poles for an electric motor, the magnetic flux carried in the back iron of the stator or rotor is taken into account. The poles are typically characterized by high field regions that can exceed 5000 gauss. The poles can come from permanent magnets or electromagnetic fields. Although the number of poles on a stator or rotor is typically fixed during manufacturing, in some embodiments described herein, the number of poles of the rotor, stator, or both can be changed during operation.

[0064] Although the presently illustrated stator 302 is presently illustrated as having distributed stator windings 304 , convex, centralized, and / or non-overlapping stators may similarly be used without departing from the present disclosure.

[0065] The rotor 306 defines a plurality of rotor poles 308 with associated rotor coils 310. The rotor poles 308 are topologically and electrically fixed on the rotor surface. A fixed pole rotor is a rotor in which the poles are topologically and electromagnetically fixed or held stationary relative to a synchronous reference frame, for example, the rotor 306 is a fixed pole rotor. That is, the rotor 306 will always rotate at substantially the same speed as the drive frequency provided by the stator, or in synchronization with the drive frequency provided by the stator (taking into account the inherent level of torque pulsation). The synchronous reference frame is the same as the magnetic reference frame. Therefore, fixed pole motors are often referred to as "synchronous" motors. Field wound rotors, surface PM rotors, reluctance motors, and internal PM rotors are all examples of fixed pole rotors. The fixed pole rotor design maximizes the utilization of ferromagnetic material in the rotor D axis 312 region (the center of the rotor poles), and in the case of a wound field rotor, ensures that the effective magnetic center is aligned with the D axis 312. Therefore, for a given size and power rating, a fixed pole rotor is considered more efficient than a moving pole rotor; however, a fixed pole rotor is difficult to control because it is challenging to maintain the fixed pole rotor at a constant current phasor angle under dynamic load conditions and dynamic operating speeds. For example, accelerating the motor or maintaining speed during load changes includes actively adjusting the current phasor angle 318, current amplitude, and / or drive frequency based on input from the position sensor 316. The concepts described herein are primarily applicable to synchronous motors because the stator field and the rotor (e.g., rotor 306) remain synchronized with each other during operation.

[0066] In contrast, the poles of a changing pole rotor are not topologically or electromagnetically fixed, but move relative to a stationary reference frame during operation. That is, the rotor will always "slip" and lag behind or become asynchronous with the drive frequency provided by the stator. For this reason, these motors are often referred to as "asynchronous" motors. Examples of changing pole rotors include wound and squirrel cage induction rotors, armature wound rotors, brushed motors, and other similar motors. While the shifting pole rotor is able to self-regulate the current phasor angle 318 during operation, a design compromise must be made between the D-axis ferromagnetic material and the Q-axis field windings to enable the poles to move evenly across the rotor surface. Therefore, in a changing pole rotor of a given size and power rating, such a motor has a higher resistance, requires a larger starting current, and has a lower field strength.

[0067] The field of the rotor 306 is configured to be excited by the magnetic field generated by the stator windings 304. The rotor 306 and the stator 302 are configured to move relative to each other in response to the excited rotor field. Except for the stator windings 304, the rotor 306 is substantially energy isolated from the components of the stator 302.

[0068] In an electric machine, the stator and rotor may be coupled to enable power transfer, signal transmission, and / or field modulation during operation. Coupling may be classified as direct or indirect. Direct coupling occurs between the stator 302 and the rotor 306, along a primary operating air gap (e.g., air gap 314). Indirect coupling occurs along a secondary interface away from the primary operating air gap.

[0069] Direct coupling is often characterized as an inductive coupling, e.g., a squirrel cage induction rotor is considered to be directly coupled to the stator. While direct coupling is common and easy to control in asynchronous machines, direct coupling to synchronous machines is difficult to control for reasons described in this disclosure. For example, it is often necessary to know the rotor position to ensure that current amplitude and / or frequency are properly maintained.

[0070] The indirect coupling runs along the secondary coupling and may be radially oriented or axially oriented and may communicate via electrical contact, inductive coupling along a separate air gap, capacitive coupling, or optical coupling. While the secondary coupling may be used for a variety of functions to improve the efficiency and / or overall controllability of the motor, additional components are often required which can increase the weight, complexity, failure frequency, and cost (operating and capital) of a machine utilizing such a system.

[0071] The couplings can be further classified as power couplings or signal couplings. Power couplings transfer power from the stator to the rotor for direct driving of the magnetomotive force along the primary operating air gap, thereby generating torque. Signal couplings transmit signals between the stator and the rotor that can be used to individually adjust circuits within the rotor or detect rotor conditions, such as temperature or position relative to a stationary reference frame. Signal couplings transmit very low power levels relative to the rated power of the motor, for example, less than 5% of the rated power of the motor. In some embodiments or under some operating parameters, it may be desirable for the signal coupling to transmit power at a level relative to the rated power of the motor, for example, 7.5%, 5%, 3%, or 2.5%.

[0072] Energy-isolated motors and generators, such as those described throughout this disclosure, primarily use direct coupling (within standard electromagnetic shielding tolerances) to transmit power and signals between the stator and rotor, without using indirect or secondary coupling. The electric machine described herein includes a direct coupling between the rotor 306 and the stator 302 for both power and signal coupling.

[0073] In some embodiments, when in position D as shown in FIG. 3B , or when transitioning from position D to position Q by modulation of the current phasor angle, the wound rotor may need to be charged or benefit from charging. Charging may mean generating current in one or more rotor windings, or transferring, increasing, or storing magnetic flux in the rotor, each of which may involve some power transfer from the stator to the rotor. This task can be accomplished in a variety of ways, for example, by adjusting the current phasor angle of the stator excitation in advance (e.g., appropriately advancing or retarding the current angle of the stator excitation), increasing the frequency of change of the stator excitation current phasor angle, increasing the amplitude of the excitation current in the stator (or any composite signal component thereof), or any combination thereof. In some cases, the rotor magnetic field may need to be weakened (e.g., reducing the level of current or magnetic flux present in the rotor and / or rotor field windings), for example, when operating at or near position D' (e.g., by transitioning from position Q to position D', or from position D' to Q'). This task can be accomplished in a variety of ways, such as modulating the current phasor angle (e.g., appropriately advancing or retarding the current angle of the stator excitation), reducing the frequency of the stator excitation current angle phasor changes, reducing the amplitude of the excitation excitation in the stator (or any of its resultant signal components), or any combination thereof. Alternatively or additionally, field weakening can be achieved by passive losses in the rotor field winding current caused by ohmic losses. In operation, in some embodiments, frequency and harmonic independence between the signal emitted by the stator and the fundamental operating frequency that determines the rotor speed can be observed. As will be described, the present disclosure recognizes that control of the motor can be achieved in such a way that, in addition to simply moving the rotor, additional goals are prioritized, such as increasing the efficiency of the system, controlling losses in the system, or mitigating the possibility of operating conditions that may damage or reduce the efficiency of the system. Further details regarding such a system are described in the present disclosure, for example, Figure 6 and related description.

[0074] 3C-3D are perspective and side views of an example motor 350. Motor 350 is substantially similar to motor 300, except for any differences described herein. Rotor 356 includes six rotor poles 358. Stator 352 includes distributed windings 354. Motor 350 has six rotor teeth (poles 358) and thirty-six stator teeth 370, resulting in a rotor tooth to stator tooth ratio of 1:6. This is different from electric motor 300, which includes four rotor teeth (poles 308) and twelve stator teeth 320, resulting in a rotor tooth to stator tooth ratio of 1:3. Other rotor tooth to stator tooth ratios may be used without departing from the present disclosure, for example, a ratio of 1:2 or 1:4 may also be used. Other rotor tooth to stator tooth ratios may be used without departing from the present disclosure, regardless of whether a convex concentrated stator winding is used or whether a distributed stator winding is used.

[0075] FIG. 4 is a side view of an example motor 400. The motor 400 is substantially similar to the motor 300 described previously, except for any differences described herein. The rotor 406 is an external rotor, while the stator 402 is an internal stator. In other words, the rotor 406 rotates around the stator 402 and around the stationary stator 402. The stator 402 defines a stator pole 411 having a concentrated, convex, non-overlapping stator winding 404. The rotor 406 includes a permanent magnetic material 416 embedded in the rotor 406. As shown, each rotor pole 408 includes four channels of permanent magnetic material 416, which are arranged in a generally "M"-shaped or "W"-shaped configuration; however, other arrangements may be used without departing from the present disclosure. The permanent magnetic material 416 may include a variety of materials, including ferrite, SmFeN, N35, N45. Although lower power permanent magnetic materials are generally used, a lower number of higher power magnetic materials may be used without departing from the present disclosure. Permanent magnetic material 416 may extend across the entire longitudinal length of each rotor pole 408, or partially across each rotor pole 408. In some embodiments, permanent magnetic material 416 may be comprised of multiple layers or laminations.

[0076] As shown, the permanent magnetic material 416 produces a net magnetic force that is substantially aligned with each rotor pole 408. In some embodiments, the permanent magnetic material can be arranged so that the net magnetic force from the permanent magnetic material 416 is staggered with the rotor poles 408. Generally, the arrangement of the permanent magnetic material depends on the desired cross-sectional flux density of the magnetic material within the rotor. In an embodiment where the permanent magnetic material 416 is located within the rotor coils 310, the flux for each group of permanent magnetic material 416 can be individually adjusted and / or modulated by adjusting the charging of the surrounding rotor coils 310. This embodiment also protects the magnets from demagnetization caused by strong stator fields. In an embodiment where the permanent magnetic material 416 is not surrounded by rotor coils, the flux regulation caused by the stator field can affect multiple groups of permanent magnetic material 416 within the rotor 406.

[0077] 5A-5C are front, side, and perspective views of an example rotor coil 310. As shown in FIGS. 3A, 3B, and 4, each rotor coil 310 acts as its own winding, with a single coil surrounding each pole, such as rotor pole 308 or 408. In this way, the rotor can be described as including concentrated, convex, and / or non-overlapping windings. In some embodiments, the winding direction of each coil can alternate with each adjacent rotor pole 308 or 408. For example, in an embodiment using a stator with convex, concentrated, and / or non-overlapping windings, this arrangement can be used. In some embodiments, the winding direction does not need to alternate between adjacent rotor poles. For example, in an embodiment using a stator with distributed windings, this arrangement can be used. Although coil 310 is shown as a single coil short-circuited by itself, other geometries can also be used, as long as each coil short-circuit itself and does not overlap with adjacent coils. Typically, rotor coils are often configured so that the current skin depth of the power transmission frequency completely penetrates the conductor of the coil. In the context of this disclosure, "current skin depth" refers to the depth from the surface of a conductor where current primarily flows, especially eddy currents induced by a magnetic field varying at a given frequency. For a given material, the skin depth can be calculated as:

[0078] δ ≈1 / √πfμσ(2)

[0079] Where 'f' is the magnetic switching frequency, µ is the magnetic permeability of the material in H / mm, and σ is the electrical conductivity of the material. Achieving full skin depth penetration within the rotor coil 310 allows for uniform inductance within the rotor coil 310. In some embodiments, the drive frequency may extend between 0 Hz and 20 Hz. In some embodiments, the drive frequency may range between 100 Hz and 2000 Hz. Typically, the rotor coils are arranged such that the decay of the magnetic flux within the rotor is resisted by current within the rotor coils in response to magnetic field excursions from the stator.

[0080] Traditionally, synchronous motors do not have a magnetizing current to magnetize the material, so the magnets must be magnetized at the factory or before installation. For this reason, if the magnetic material demagnetizes during operation (for example, because the stator imposes too much load on it), the magnets will be damaged or the motor will not work at all. The rotor coil 310 helps protect the permanent magnets from the potential demagnetization of the stator. When operating between the Q axis (90°) and the D axis (0°), a high level of charging occurs, which carries a considerable inductive decay (for example, to maintain the magnetic field). The decay can be observed by the current flowing through the rotor coil (310, 410) to resist the flux change. Under this control scheme (combined with coils 310 or 410), the rotor magnetic field can be modulated based on the current phasor angle. This can translate into a wide operating range during operation. In some cases, the operation of the D axis to the Q axis can allow for a shielding effect that protects the magnetic material, which allows less magnetic material, lower coercivity material, or both. Alternatively or additionally, the magnetic field weakening injected by the D axis is not constant compared to permanent magnet motors. Similarly, the rotor magnetic field can be modulated by the current amplitude flowing through the stator. In many cases, the current amplitude and the current phasor angle can be adjusted simultaneously to achieve the desired rotor magnetic field modulation.

[0081] 6 is a schematic diagram of an electric motor 600 in which the rotor 602 and stator 604 are aligned. Position D is defined as relative stator 604 and rotor 602 pole alignment (i.e., NS and SN). Positions Q and Q' are defined as completely misaligned poles (i.e., close to similar poles and opposite poles, respectively), or electrically orthogonal to D and D' because similar stator 604 and rotor 602 poles are aligned (i.e., NN and SS). In some embodiments, particularly in rotors with high saliency, peak torque occurs between the D and Q positions in a synchronous reference frame (e.g., due to their reluctance component). In other embodiments such as circular rotors (e.g., less convex machines), peak torque occurs between the Q and D' positions. In the case of permanent magnet motors, peak torque operation can result in demagnetization at high loads and the need to weaken the magnetic field at high speeds. Weaker magnets can be used to the detriment of size / weight and / or torque generation.

[0082] In some embodiments, permanent magnets may be used. In order to increase the magnetic flux capacity without the risk of demagnetization, the rotor windings described herein are used. At lower torques, the rotor winding current reduction can be allowed to reduce the cogging (resistive) torque and eliminate the need for active flux weakening of stronger permanent magnets. By using the modulation of the current phasor angle of the present invention, a wound rotor can be flux weakened or enhanced through a control mechanism (e.g., the current in the rotor field winding is reduced or increased and the flux in the rotor poles themselves). As a non-limiting example, the current phasor angle of the synchronous excitation from the stator can be modulated. In at least some configurations, no secondary control system or additional commutation hardware is required, such as in a wound rotor synchronous motor, such as for controlling the stator magnetic field).

[0083] As described herein, the wound rotor configuration according to the present disclosure does not require additional stator-rotor coupling elements. Instead, the stator windings and rotor windings and rotor laminations are used to transmit signals. This reduces cost and component parts, improves performance (e.g., eliminates ohmic losses of brushes), eliminates or controls physical contact and wear parts, reduces packaging size, and provides control flexibility compared to solutions that incorporate special detectors, sensors, wired or wireless connections, or brushes to transmit signals from the stator to the rotor.

[0084] As described throughout this disclosure, in systems where control signals may be converted to DQ axis components, a third z-axis component is also present, as shown in Figure 6, and may be described as a signal or magnetic quantity that does not map directly onto the D axis or the Q axis, for example, as shown, a component that is orthogonal to the plane in which the Q and D components may be defined.

[0085] In operation, field-oriented or vector control with specific modulation (e.g., signal or signal parameter modulation) can be used to control various aspects of the rotor field. These modulations can be used to adjust the signal excitation coupled between the stator and the rotor, as well as control the stator excitation wave relative to the rotor (e.g., relative position and amplitude). Thus, the stator and inverter can effectively "steer" the rotor response or the direct correlation of the current induced in the rotor windings. In other words, such control can produce a dynamic behavior of the machine that is a function of the current in the D-axis and Q-axis fields, coordinated by a controller such as controller 104 or controller 700 (Figure 7). In other strategies (e.g., torque generation), vector modulation can be used to help define the modulation of the current phasor angle.

[0086] The present disclosure recognizes that vector control modulation can be used to directly affect rotor reactions through applied stator signals. In addition, these rotor reactions can be modulated on the D axis or Q axis and can be achieved using current phasor angle modulation. The relative effectiveness of the current phasor angle modulation can be proportional to the amplitude and percentage change (e.g., over a period of time) of the modulation. The speed of adjusting the current phasor angle can be varied on the controller and can be selected based on the expected response of the rotor material or the rotor response. In some cases, the frequency can be selected based on the speed of the machine, while in other cases, a fixed modulation can be selected. The frequency of the modulation can be selected based on various considerations. For example, in some configurations, the frequency can be at least 2-4 times higher than the fundamental frequency of the machine. In other cases, the modulation can be 5-10 times higher than the fundamental frequency of the machine. In further configurations, the frequency can be 10-30 times higher than the fundamental frequency of the machine. For example, in some configurations, the frequency can be selected to prevent interaction with torque generation (e.g., reduce torque pulsation).

[0087] The current phasor angle can be controlled using vector component control, which can be achieved by letting i d 、i q and i z is described by the current at the fundamental frequency expressed in the DQ reference frame shown in Figure 6 (e.g., including the main control component of the current phasor angle). These signals can be modulated directly, or alternatively, an independent excitation modulation can be added on either D / Q axis, which is superimposed on the fundamental current to produce the total stator current:

[0088] (3)

[0089] (4)

[0090] (5)

[0091] Among them, i d 、i q and i z is the normal excitation current along each axis, , and z is an independent modulation signal that can be selected and controlled by a motor controller or other controller, as will be discussed further. The modulation can be selected to be sinusoidal or take any form, for example, such modulation can be further described as:

[0092] (6)

[0093] (7)

[0094] (8)

[0095] The modulation amplitude and frequency can be selected independently for each component and the vector sum to change the current phasor angle, or the main component can be changed by directly controlling the current phasor angle (γ):

[0096] (9)

[0097] (10)

[0098] (11)

[0099] Similarly, the set current phasor angle can be modulated, for example:

[0100] (12)

[0101] (13)

[0102] (12)

[0103] Here, the gamma modulation can be described, for example, as a sinusoidal oscillation around a fixed current angle:

[0104] (13)

[0105] (14)

[0106] (15)

[0107] In each case, modulation can be applied to a single axis without applying modulation to the other two axes and used to produce a rotor response. Alternatively or additionally, D-axis current modulation can be used, or D-axis current modulation can be varied together with Q-axis current modulation, with the goal of controlling or minimizing torque pulsation. If D-axis modulation is not sufficient, Q-axis modulation can be used. In some embodiments, Q-axis modulation is used in conjunction with D-axis modulation to form a rotating vector injection. Z-axis modulation itself does not affect torque pulsation and does not require knowledge of the DQ reference system. However, the effect of Z-axis modulation on the rotor is often limited, but can be used to couple the stator to the rotor for power or accessory information coupling (e.g., speed and / or position).

[0108] The frequency of the current modulation or the current phasor oscillation can be described by a duty cycle. The duty cycle can describe the operation divided between the main components of flux generation (e.g., D axis) and torque generation (e.g., Q axis). Under starting conditions, the duty cycle on the D axis can be 100%, or 75-100%, or 40-100%, which is used to generate hard flux on the rotor before the operation is separated between the D axis and the Q axis to produce torque, where there can be 50%-50% separation, 30%-70%, 20%-80%, 10%-90% separation (D axis: Q axis). This can also be manifested as an oscillation around the current phasor angle, where the current phasor angle and the resultant magnetic field vary around an angle of 5 degrees, 10 degrees, 20 degrees, or in some cases 30-45 degrees during steady-state or quasi-steady-state operation. In some embodiments, the frequency of the oscillation or amplitude modulation can be varied to cause rotor response and / or limit torque pulsations in operation.

[0109] Additionally, the control strategy may utilize higher frequency operation or pulsing to limit the amount of flux in the rotor coils that decays over time. That is, by shortening the time step between the rotor's MMF cycles (which decay over time), the change in flux through the rotor coils may be reduced to harden the flux and reduce any negative torque or associated torque ripple. Additional signal modifications such as skew signals, trapezoidal or pulse width modulation (PWM) techniques may be used to help flux produce the rotor, limit torque ripple and smooth the transition between current phasor angles on the fly.

[0110] Because the stator side current can correspond to the stator side voltage, the scheme including the signal embedded in the current can correspond to the equivalent scheme including the signal embedded in the voltage. Throughout this disclosure, the embodiments described with reference to the signal in the stator side voltage can be equivalent to and can also describe the signal in the stator side current, and vice versa.

[0111] As previously described, control of the rotor field can be manipulated by the controller through the stator windings using current phasor angle modulation. This modulation can be defined by amplitude and frequency and can be observed through the magnetic field, stator excitation, and main control components of the machine. Current phasor angle modulation can be used to transfer power to the AC coil, where the oscillation of the current angle is defined around a set operating point of the current angle defined by the DQ reference frame (for example, the current angle can be modulated to achieve a target torque per ampere MTPA). Current phasor angle modulation disturbances can be defined by the oscillation, amplitude, and frequency of the excitation field. Current amplitude modulation at a given current phasor angle can be used to transfer power to the rotor or induce a reaction in the rotor, where the maximum response can be seen at the current angle (in the DQ reference frame of a given magnetic pole) that is most coupled to the rotor. For example, for a wound rotor aligned with the D axis relative to the synchronous reference frame axis, the maximum power transfer will occur at a phasor current angle of 0° electrical angle (where 0° electrical angle is defined as the D axis of the synchronous reference frame).

[0112] FIG. 7 is a block diagram of an example controller 700 that can be used with aspects of the present disclosure. The controller 700 can be used to supplement or replace the motor controller 104 described above. In the former case, the controller 700 and the motor controller 104 can be combined into a single integrated controller, or the controller 700 and the motor controller 104 can be separate, discrete controllers. The controller 700 can monitor parameters of the motor (300, 400) and send signals to actuate and / or adjust various operating parameters of the motor (300, 400). As shown in FIG. 7, in some cases, the controller 700 includes a processor 750 (e.g., implemented as one or more processors) and a memory 752 (e.g., implemented as one or more memories), and the memory 752 contains instructions that cause the processor 750 to perform the operations described herein. The processor 750 is connected to an input / output (I / O) interface 754 for sending and receiving communications with components in the motor (300, 400), including, for example, a rotor position sensor or a current sensor. In some cases, the controller 700 may additionally communicate status with one or more of the various motor components of the motor (300, 400) and other sensors (e.g., temperature sensors, vibration sensors, and other types of sensors) disposed in the motor (300, 400) and send actuation and / or control signals thereto (including power or drive signals to the stator). The communication may be hardwired, wireless, or a combination of wired and wireless. In some embodiments, the controller 700 may be a distributed controller with different parts located in different locations, such as different sections of a vehicle. Additional controllers may be used in conjunction with the controller 700 as a standalone controller or a networked controller without departing from the present disclosure.

[0113] The controller 700 may have different levels of autonomy for controlling the motor (300, 400). For example, the controller 700 may begin to sense changes in load and / or speed, and the operator adjusts the power frequency, current amplitude, and / or current angle. Alternatively, the controller 700 may begin to sense changes in load and / or speed, receive additional input from the operator, and adjust the frequency, current amplitude, and / or current angle without other input from the operator. Alternatively, the controller 700 may begin to sense changes in load and / or speed, and adjust the frequency, current amplitude, and / or current angle without input from the operator. Typically, the controller 700 is capable of receiving a signal indicating a desired operating point, receiving a signal indicating a current operating point, and then being capable of adjusting the frequency, current amplitude, and / or current angle in response to converging the current operating point to the desired operating point.

[0114] For example, in operation, the controller may be a controller configured to excite the stator windings and generate a stator magnetic field within the stator by sending control signals to the stator windings. The controller may be configured to generate a stator magnetic field by sending current through the stator at a current angle and amplitude, and actively adjust the current angle and amplitude according to the operating conditions of the motor (300, 400). In some embodiments, the phasor current angle 318 increases in the direction of motion before the rotor poles (308, 408) during high torque conditions. That is, in situations where a greater current per unit of torque is required, an increased phasor current angle 318 may result. Typically, as the current phasor angle 318 increases, the rotor coils (310, 410) become more active (more current flows through the coils) due to the reduction in the D axis component 312. In other words, as the current phasor angle 318 increases, the field of each rotor winding decays faster. Greater activity within the coils results in increased torque ripple without mitigation; however, during the increase in the D-axis component experienced by each pole, the current amplitude can be increased, thereby offsetting the potential negative torque produced by the increased current angle 318. Alternatively or additionally, the phasor current angle 318 is reduced during high speed, low torque operation. Alternatively or additionally, the current angle can become negative during braking operations. Regardless of the operating mode used, the controller 700 is capable of adjusting the current angle and / or current amplitude to meet the current demand of the motor (300, 400) in a given situation.

[0115] In particular, the current phasor angles or current amplitudes of the main components of the machine can be adjusted on the fly to produce torque. In some cases, such as when the rotor has sufficient magnetic field strength, no magnetizing current can be applied (or less magnetizing current can be applied) compared to the previous time step. In other cases, such as when running at high speeds, the rotor field can be allowed to degrade to reduce the back electromotive force (EMF) and provide voltage margin, reduce cogging torque to limit torque ripple, and avoid active field weakening operation.

[0116] The controller is able to communicate with the rotor through the stator at a wide range of frequencies, such as between 50 and 1000 Hertz (Hz). In some embodiments, communication occurs between 100 and 1000 Hz. Regardless, the system is able to communicate changes faster than conventional systems. For example, conventional squirrel cage induction motors communicate at essentially 7 Hz. The ability to transmit at a higher frequency allows the controller 700 to proactively reduce torque pulsation regardless of operating conditions and quickly adjust to changes in operating conditions.

[0117] FIG8 is a flow chart of a method 800 that can be used with aspects of the present disclosure. All or part of the method 800 can be performed by the controller 700 and / or the controller 104. At 802, the stator coil is excited. At 804, the corresponding rotor magnetic field in the ferromagnetic material in the rotor is modified by the stator magnetic field. At 806, the offset of the stator magnetic field generates a force tangential to the rotor. At 808, the rotor is moved by the generated tangential force. The stator magnetic field and the rotor remain synchronized with each other during operation. At 810, in response to the magnetic field offset, the current in the rotor coil resists the decay of the magnetic flux in the rotor. At 812, the current is sent through the stator at a current angle. Typically, the current angle is located before the rotor pole in the direction of motion. In some cases, at 814, the current amplitude of the current is adjusted in response to operating conditions. In some cases, at 816, the current angle relative to the rotor pole (D axis) is adjusted in response to operating conditions. In particular, 814 and 816 are shown in dashed form because these two steps are not required and are not required in this order. That is, the current amplitude and the current angle can be adjusted independently of each other.

[0118] Thereafter, the operation output of the motor at the current time is compared with the expected operation output of the motor. If the operation output of the motor at the current moment is at the expected operation output of the motor, the motor continues to operate using the most recently adjusted stator current parameter. If not, the process is repeated to return to adjust at least one of the current amplitude or current angle of the stator current until the operation output of the motor at the current time is at the expected operation output of the motor.

[0119] Referring now to FIG. 9A , a non-limiting example of process control according to the present disclosure is provided. In particular, FIG. 9A provides an example flow chart of controlling a motor system to deliver increased torque 900 according to the present disclosure. Process 900 begins with a request or request for increased torque at 902. According to the present disclosure, satisfying the request can be conceptualized as executing two parallel work flows. However, in practice, the controller need not be programmed or designed to operate in independent, parallel, or different flows. To satisfy the request for increased torque 902, the controller determines that the increased torque can be achieved by increasing the rotor flux at 904. To do this, I dThe rotor flux is increased at 906, which increases at 908. This continues until the desired rotor torque is reached, and then at 910 I d However, in seeking to increase rotor flux, the controller recognizes that Q axis current modulation can be used, or varied along with D axis current modulation, in order to control or minimize torque ripple. Therefore, at 912, the controller also works to maintain torque performance. To this end, the controller also adjusts I q , thereby producing the desired torque increase at 916, but without the adverse effects of unstable torque performance, such as that caused by torque pulsation.

[0120] Referring now to FIG. 9B , another non-limiting example of a control process 918 for responding to a request for increased torque at 920 is provided. In response to the request at 920, the controller determines that the increased torque can be achieved by requesting an increase in rotor flux at 922. To achieve this, the controller seeks to modulate the current angle toward the D axis at 924, as this will easily increase the rotor flux at 924, which is further controlled by modulating the current angle toward the Q axis at 928. In parallel, the controller modulates the current angle at 930 by modulating I q To maintain torque performance, as described above. Therefore, as a result, at 934, the requested torque increase is delivered to.

[0121] Referring now to FIG. 9C , another non-limiting example of a control process for reaching a desired torque from startup is provided at 936. At startup, the rotor is locked at 938. To begin rotation, at 940, the current angle is modulated toward the D axis, and at 942, as the rotor moves toward the D axis, the rotor flux builds or increases. At 944, the current angle is modulated toward the Q axis, and the process continues until the desired torque is produced at 946.

[0122] 9D provides yet another non-limiting example of a control process for achieving a desired torque at 948. In this case, the process begins with the motor already at high speed 950. At 952, the duty cycle of the current angle modulation is reduced, and at 954, the amplitude of the current modulation is reduced. As a result, the rotor flux decreases at 956. As the rotor flux decreases, at 958, the back EMF decreases, and at 960, the cogging torque decreases. Given the high operating speed of the motor at 950, this control ultimately produces an increase in torque at 962.

[0123] Thus, the described systems and methods show a net increase in torque developed with sinusoidal excitation due to net rotor field D-axis current injection resulting from the asymmetric flux vector of the rotor field lines along the stator D-axis. Net D-axis current injection is therefore feasible in conventional circuits with analog circuits. The motor with the rotor coil structure will be less saturated, presenting a net benefit of shorting the coils in terms of average torque production. Net D-axis current injection enables greater surface current density to be achieved with equivalent stator excitation due to the reactive rotor coil current.

[0124] As shown in Figure 10, plots of average magnetic field strength are provided for three different interior permanent magnet machines. In the first machine, no coils were included. In the second machine, shorted coils were included. As is clear from Figure 10, the magnetic field strength of the machine with the coil structure is increased compared to the machine without the coil.

[0125] Thus, certain embodiments of the subject matter have been described. Other embodiments are within the scope of the following claims. In some cases, the actions recited in the claims can be performed in a different order and still achieve the desired results. Furthermore, the processes depicted in the accompanying drawings do not necessarily require the particular order shown, or sequential order, to achieve the desired results.

Claims

1. A method for controlling a motor, the method comprising: exciting a stator winding of a stator of the motor by means of a stator current; generating a stator magnetic field in the stator by means of energized stator windings; generating a corresponding rotor magnetic field in a ferromagnetic material in a rotor of the electric machine via the stator magnetic field, the rotor defining a plurality of rotor poles; generating a force tangential to the rotor by deflecting the stator magnetic field; moving a rotor by generating a force tangential to said rotor; In response to the displacement of the stator magnetic field, resisting the decay of the magnetic flux in the rotor by current in the rotor coil, wherein during operation of the motor, the stator magnetic field and the rotor remain synchronized with each other; and Achieving a target operating output of the motor.

2. The method according to claim 1, further comprising: Based on the target operation output of the motor, a current angle of a stator current measured from a closest one of the plurality of rotor poles is adjusted.

3. The method according to claim 2, wherein: Adjusting the current angle includes adjusting the current angle on only one axis of the electric machine.

4. The method according to claim 3, wherein: The one axis comprises one of a D axis or a Q axis of the electric machine.

5. The method according to claim 4, further comprising: determining a target rotor motion corresponding to a target operating output of the electric machine; When the rotor performs a target rotor motion, modulating the current on the D axis to control rotor torque pulsation; and Achieving the target operating output of the motor.

6. The method according to claim 1, further comprising: Based on a target operating output of the motor, a current magnitude of the stator current is adjusted independently of a current angle of the stator current.

7. The method according to claim 1, further comprising: A target rotor motion corresponding to the target operating output of the electric machine is determined.

8. The method according to claim 7, further comprising: calculating a vector control modulation applied to the stator that causes a target rotor motion; and The current angle of the stator current is adjusted based on the vector control modulation so that the rotor performs the target rotor motion and achieves the target operating output of the motor.

9. The method according to claim 8, further comprising: At least one of an amplitude or a frequency of a stator current is adjusted based on the vector control modulation.

10. The method according to claim 7, further comprising: adjusting at least one of the frequency or the amplitude of the stator current to cause the rotor to perform the target rotor motion; and When the rotor performs a target rotor motion and achieves a target operation output of the motor, the target operation output of the motor is achieved or rotor torque pulsation is controlled.

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