Architecture and control platform for integrated modular motor drive

Abstract

An integrated modular motor includes a rotor with permanent magnets and a stator with multiple modules. Each module has a winding and control board containing a switching circuit, current sensor, and controller. The controller controls switching to provide alternating current to the winding, creating electromagnetic fields that drive the rotor's permanent magnets. Controllers communicate with other modules and share current information. Modules are arranged in control districts, each containing an odd number of parallel-connected modules. Each module produces current offset from others in its district. One controller per district serves as leader, others as followers. A global controller commands all leader controllers to drive the rotor.

Description

MU1199630024.00275ARCHITECTURE AND CONTROL PLATFORM FOR INTEGRATED MODULAR MOTOR DRIVECROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. Provisional Patent Application No. 63 / 708,663, filed on October 17, 2024, and entitled “ARCHITECTURE AND CONTROL PLATFORM FOR INTEGRATED MODULAR MOTOR DRIVE,” which is herein incorporated by reference in its entirety.STATEMENT OF FEDERALLY SPONSORED RESEARCH

[0002] This invention was made with government support under DE-AR0001352 awarded by the Department of Energy ARPA-E Agency. The government has certain rights in the invention.BACKGROUND

[0003] Integrated Modular Motor Drives (IMMDs) are motor drives constructed from a number of modular phase-drive units that are interconnected in a ring to form the electrical core of the motor. Each of these phase-drive units includes both an iron core segment and its winding and an integrated power electronics module (IPEM) that is connected to the pole piece. The resulting integrated motor and driving electronics eliminates at least some of the need for separate drive electronics as well as wires and connectors typically required between a motor and electronic controls.

[0004] IMMD units are particularly advantageous because they enable a motor drive to continue operating when one or more of the phase-drive units fails, improving overall drive reliability. Replacement modules, moreover, can be standardized and produced at high volume to reduce drive costs. The risk of short circuits between windings is also reduced because the windings of the individual modules do not longer overlap, which minimizes the possibility of direct contact between the phase windings.

[0005] Although IMMD units, therefore, offer a number of advantages, there are also challenges associated with these types of systems. For example, because each module includes its own power electronics board, communications must be coordinated between the individual modules to control the overall operation of the motor. If a communication link fails, it can lead to loss of control, impacting performance. Further, if there is latency in communications between modules, real-time control may be negatively affected, and the motor may not be as responsive as1QB\630024.00275\ 99023718.3MU1199630024.00275 required for a given application. It can also be important for the IMMD systems to be scalable. For example, as systems grow, communication demands can increase, and it is important that the communications system be able to address these increased demands.

[0006] These and other issues are addressed by the following disclosure.SUMMARY OF THE DISCLOSURE

[0007] According to an aspect of the present disclosure, an integrated modular motor is provided. The integrated modular motor comprises a rotor comprising a plurality of permanent magnets. The integrated modular motor comprises a stator comprising a plurality of modules, wherein each of the plurality of modules comprises a winding and a control board. The control board for each module comprises a switching circuit coupled to the winding, a sensor for sensing current in the winding, and a controller configured to control switching of the switching circuit to provide an alternating current to the winding, the alternating current developing an electromagnetic field in the winding to drive the permanent magnets in the rotor. The controller is configured to communicate with the control boards corresponding to the other of the plurality of modules, and to communicate sensed current information to the other modules. The plurality of modules are arranged in a plurality of control districts, each control district comprising an odd-numbered set of n modules connected in parallel, each of the odd-numbered set of n modules in each control district being configured to produce a current offset from a current produced by the other of the odd- numbered set of n modules of the control district. The controller in one of the of the odd-numbered set of n modules includes a leader controller for controlling communications in the control district, and the other controllers in the control district are follower controllers. The integrated modular motor comprises a global controller, the global controller configured to provide commands to each of the leader controllers to drive the rotor.

[0008] According to other aspects of the present disclosure, the integrated modular motor may include one or more of the following features. The leader and the n-1 follower controllers may be connected in a daisy chain, each of the leader controller and the n-1 follower controllers may be programmed to acquire a sensed current corresponding to the winding, and the sensed currents may be transmitted as follows: the leader controller may transmit the corresponding sensed current to a predetermined first one of the n-1 follower controllers; in a predetermined chain of follower controllers, the first one of the n-1 controllers may transmit the sensed current corresponding to the leader controller and the sensed current corresponding to the receiving one2QB\630024.00275\ 99023718.3MU1199630024.00275 of the n-1 controllers to another of the n-1 controllers; the step may be repeated, with each of the n-1 follower controllers in the predetermined chain adding a sensed current corresponding to the receiving follower controller and the last follower controller in the predetermined chain may transmit the sensed currents corresponding to the leader controller and to each of the follower controllers to the leader controller. The motor may be a three-phase motor, and the leader may provide a sensed current value corresponding to the winding associated with the leader controller to a first follower controller, the first follower controller may provide a sensed current value associated with the first follower controller and a sensed current value corresponding to the winding associated with the first follower controller to a second follower controller; and the second follower controller may provide the sensed current value associated with the first follower controller and a sensed current value associated with the second follower controller current value to the leader controller. The leader controller may be programmed to calculate and transmit a pulse width modulation command to the switching circuit associated with each of the first and second follower controllers based on the sensed current values, and to control the switching circuit associated with the leader controller based on the calculated pulse width modulation command. The plurality of control districts may be connected in series to a direct current link voltage source, and the leader controller may be further programmed to calculate an adjustment current based on a difference between an actual direct current link voltage and a measured direct current link voltage. The leader controller may be programmed to perform a Clarke conversion, a Park conversion, and a space vector modulation to determine pulse width modulation gate pulses to be applied to the windings associated with each of the leader controller and the follower controllers, and to transmit these values to the follower controllers. Each of the leader controllers may be configured to provide voltage feedback to the global controller, and the global controller may be configured to calculate a current adjustment based on a comparison of the voltage feedback and an expected value of a de link voltage, and to provide the current adjustment to each of the leader controllers. The switching circuit may be an H-bridge inverter. The leader controllers may be in communication with and receive commands from the global controller. The plurality of modules may comprise eighteen modules. The plurality of control districts may comprise six. The global controller may be configured to detect a fault condition in one of the plurality of modules and to redistribute torque demand among remaining healthy modules in response to the fault condition. The fault condition may comprise a short circuit in one of the windings, and the global controller may be configured to disable the switching circuit associated with the faulty winding and adjust3QB\630024.00275\ 99023718.3MU1199630024.00275 torque references for the remaining modules in the affected control district. The leader controller in the affected control district may be configured to implement a proportional-integral-resonant controller to suppress oscillatory components arising from current imbalance caused by the fault condition. The global controller may be configured to adjust DC link voltage references for each control district during fault conditions to redistribute power among the plurality of control districts. The DC link voltage reference for a control district containing a faulty module may be reduced, and the DC link voltage references for remaining healthy control districts may be increased to maintain overall system power balance. The motor may be configured to continue operating with reduced torque contribution from a faulty control district while maintaining overall torque tracking performance through compensation by healthy control districts.

[0009] According to another aspect of the present disclosure, a stator for use in an integrated modular motor is provided. The stator comprises a plurality of modules, wherein each of the plurality of modules comprises a winding and a dedicated control board. The dedicated control board for each module comprises an inverter circuit coupled to the winding and a controller configured to control switching of the inverter circuit and communicate with at least one of the dedicated control boards corresponding to the other of the plurality of modules. The plurality of modules are arranged in a plurality of control districts, each control district comprising a set of three modules connected in parallel, each of the three modules in each control district being configured to produce a current offset one hundred and twenty degrees from a current produced by the other modules of the control district. The controller in one of the sets of three modules includes a leader controller, and the other controllers in the control district are first and second follower controllers.

[0010] According to other aspects of the present disclosure, the stator may include one or more of the following features. The leader and the first and second follower controller may be connected in a daisy chain, wherein the leader may provide a sensed current corresponding to the leader controller to the first follower controller, the first follower controller may provide the sensed current corresponding to the leader controller and a sensed current corresponding to the first follower controller to the second follower controller, and the second follower controller may transmit the sensed current corresponding to the leader controller, the sensed current corresponding to the first follower controller, and the sensed current corresponding to the second follower controller to the leader controller. The plurality of control districts may be connected in series to a direct current voltage source. The follower controllers may be configured to provide voltage and 4QB\630024.00275\ 99023718.3MU1199630024.00275 current feedback to the leader controllers corresponding to each control district, and the leader controllers may be configured to adjust commands to the follower controller to balance a de link voltage. The leader controllers may be configured to drive the switches in the inverter. The inverter circuit may be an H-bridge inverter. The stator may further comprise a global controller configured to provide commands to each of the leader controllers, wherein the leader controllers may be in communication with and receive commands from the global controller. The plurality of modules may comprise eighteen modules. The plurality of control districts may comprise six.

[0011] According to another aspect of the present disclosure, a method of fault-tolerant operation for an integrated modular motor comprising a plurality of modules arranged in control districts comprising an odd-numbered set of modules connected in parallel is provided. Each of the odd-numbered set of modules in each control district is configured to produce a current offset from a current produced by the other of the odd-numbered set of modules of the control district. The method comprises detecting a fault condition in one of the plurality of modules, disabling a switching circuit associated with the faulty module, reducing torque contribution from a control district containing the faulty module, redistributing torque demand among remaining healthy modules, and adjusting DC link voltage references for each control district to maintain power balance.

[0012] According to other aspects of the present disclosure, the method may include one or more of the following features. The method may further comprise implementing a proportionalintegral-resonant controller in the control district containing the faulty module to suppress second harmonic oscillations caused by current imbalance.BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Fig. 1 A is an example motor constructed with a segmented stator in accordance with the disclosure;

[0014] Fig. IB is a perspective view of a segment of the segmented stator structure shown in Fig. 1A;

[0015] Fig. 2 is an exploded view of the motor of Fig. 1A;

[0016] Fig. 3 is a top view of the motor of Fig. 1A;

[0017] Fig. 4 is a block diagram of a power electronics board that can be used to drive the windings in the individual stator segments of the motor of Figs. 1 - 3;5QB\630024.00275\ 99023718.3MU1199630024.00275

[0018] Fig. 5 is a schematic illustrating the interconnection architecture of the stator segments of the motor of Figs. 1 - 3 to provide a multi-phase motor;

[0019] Fig. 6 is a network diagram illustrating communications between the controllers in the motor of Figs. 1-3 using the interconnection architecture of Fig. 5;

[0020] Fig. 7 is a schematic illustrating a vector or field orient control implemented in the motor of Figs. 1 - 3;

[0021] Figs. 8A and 8B are a flow chart illustrating the process steps of a leader controller in the network of Fig. 6; and

[0022] Fig. 9 is a timing diagram of communications between leader and follower controllers.

[0023] Fig. 10 is a block diagram of an example proportional -integral-resonant (PIR) controller.DETAILED DESCRIPTION

[0024] Referring now to Fig. 1A, a machine drive 10 constructed using integrated motor modules with segmented stator modules is shown. The machine drive includes a rotor 13, and a segmented stator structure 12 which includes a plurality of open-slot iron core segments 11 aligned side by side, with slots 15 formed between each pair of adjacent open-slot core segments. The slots 15 are filled with coils or windings 14. Referring now also to Fig. IB, each of the segments in the segmented stator structure, here segment 12a, is associated with a power electronics board 68a for driving the corresponding winding 14a, as described below. The integrated modular motor drive (IMMD) concept provides a solution for applications that require high power density, efficiency, and reliability. The modular aspect of IMMDs makes them reliable candidates with fault-tolerant capabilities, where with the failure of one or two modules, the overall system can continue to function.

[0025] Referring now to Figs. 2 and 3, a perspective and an exploded view of an electrical machine 60 constructed with the machine drive of Fig. 1A as part of an integrated motor module drive is shown. As illustrated here, the electrical machine 60 includes the segmented stator 12, a motor 62, and corresponding shaft 63 that is driven by the rotor 13. A rotational sensor or encoder 65 may be coupled adjacent the rotor 13 to monitor the rotation angle. A power electronics drive board 68a ... 68n is associated with each stator segment 12a ... 12n in the segmented stator 12, here illustrated as a combined ring of boards 68. In some applications, heat sinks 64 or heat6QB\630024.00275\ 99023718.3MU1199630024.00275 exchangers 22 may also be provided as part of the machine 60 to maintain both the stator 12 and corresponding boards 68 within a defined temperature range. As illustrated here, each stator segment 12a... 12n and a corresponding power electronics board 68a ... 68n define an integrated motor module 17a ... 17n, and these modules can be combined to form an integrated motor module drive. For ease of description, the components of a generic integrated motor module may be identified as 17x, 12x, 68x, etc. hereafter. In one embodiment, the integrated modular motor drive 10 may include eighteen identical inverter modules 17x, where each module includes a GaN-based full-bridge power converter PCB, a DC capacitor bank PCB, a PCB busbar that connects the DC capacitor bank to the power converter PCB, and a dedicated control and communication PCB 68x.

[0026] Referring now to Fig. 4, a block diagram illustrating the components of each individual power electronics board 68a ... 68n is shown. Each power electronics board 68x includes a power electronics processor, controller, or microcontroller 70 that is in communication with a global controller 72 through a communication port 74. The communication port 74 may, for example, be provided as an integral part of the controller 70 or be provided as a separate transmitter / receiver component. The controller 70 provides commands to a gate driver 76 which controls switching electronics 78 to produce an AC signal at the motor windings or coils 14. The controller 70 also receives feedback from a current sensor 80 connected to the motor coil or winding 14, and from a voltage sensor 82 that monitors direct current (DC) link voltage 73 (Fig. 5) input to the switching electronics 78, as described below. Signal conditioning circuits 79 and 81 can include, by way of example, an anal og-to-digi tai convertor, amplification, and filtering between the current sensor 80 and voltage sensor 82, respectively. The switching electronics 78 can be, by way of example, an H-bridge having two parallel legs each with two switches, where the input to the H-bridge is a DC voltage source and the output can be a square or sinusoidal wave output voltage created by selectively closing and opening switches and varying the duty cycle. The H-bridge can use various types of semiconductor switches, including MOSFETS, IGBT’s, IGCTs, Thyristors, BJT, JFET, SCR, FET, Transistor, or other types of devices. Although the signal conditioning circuits are illustrated separately here, in some applications, these functions may be provided as part of the controller 70.

[0027] Referring now to Fig. 5, a diagram illustrating the interconnection of the individual modules 17x of the electrical machine 60 is shown. To provide an n-phase motor 62, an odd number of n modules 17x (17a, 17b ... 17n) are connected in parallel. These sets of parallel- connected modules are referred to hereafter as a “control district” 90x. Individual control districts7QB\630024.00275\ 99023718.3MU1199630024.0027590x can then be connected in series with other control districts 90x and a DC link voltage 73. Referring now also to Fig. 6, the global controller 72 is in communication, either directly or indirectly, with the controllers 70 on individual boards 68x, so that the global controller 72 can provide commands for driving the motor 62. The global controller 72 can also be in communication with a rotational sensor or encoder 65 that monitors the angle of the shaft 63 turned by the motor 62. Referring now to Fig. 5, the topology is highly modular, where each inverter module 17x drives a single motor coil pair 14x. Given the three-phase nature of the motor 62 and the presence of multiple identical inverter modules 17x, the system can be organized into multiple three-phase subsets or control districts 90x.

[0028] Referring now to Fig. 6, a network diagram illustrating communications between the global controller 72 and the control districts 90x is shown. As described above, there can be any number of control districts 90a ... 90m and each control district 90x can include any odd number of windings n, which together form an n-phase motor. Each winding 14x is associated with a corresponding power electronic boards 68x and controller 70x. Here, for ease of description, three control districts 90x are illustrated, each with three modules 17a, 17b, 17c, each including power electronic boards 68a, 68b, 68c and controllers 70a, 70b, 70c coupled to corresponding windings 14a, 14b, 14c, which together form a three-phase motor 62. As illustrated here, the network communications between the controllers 70a, 70b, 70c in the control district 90 are provided in a daisy-chain configuration. In this configuration, controller 70a is a “leader”, which is in communication with the global control 72, and the controllers 70b and 70c are “followers.” Data transmissions are initially sent from the leader 70a to the follower 70b. The follower 70b then sends data to follower 70c. Finally, the follower 70c sends communications to the leader 70a to close the communications loop between the connected controllers 70, as described more fully below. Each module 17x is equipped with an independent control and communication PCB 68x, enabling a semi-hierarchical control architecture.

[0029] Referring now to Fig. 7, a current regulator 100 for controlling motor 62 using a vector control is shown. The current regulator 100 operates on the leader controller 70a, receives two reference currents idref and iqref from the global controller 72, and an iadj value from a separate control process 106 which accounts for changes or fluctuations in the DC link voltage 73. The current regulator 100 also receives feedback of actual current from current sensors 80 corresponding to each of the power electronic modules 68a, 68b, and 68c in the corresponding control district 90x, and feedback regarding the rotational axis of the shaft 63 from encoder 65 8QB\630024.00275\ 99023718.3MU1199630024.00275(Fig. 5). The current regulator 100 provides commands for driving the windings 14a, 14b, 14c associated with each of the modules 17a, 7b, and 17c associated with the control district 90 as described below. Although, as described here, the current regulator 100 operates on the leader controller 70a, in some applications, these calculations may also be performed at the follower controllers 70b and 70c, and the resultant data compared between all of the controllers in the network. The control strategy can be designed to satisfy three obj ectives: DC link voltage reference tracking for each three-phase subset, rotor speed reference tracking, and torque reference tracking for the overall load. The latter two are achieved through field-oriented control (FOC), while the DC link voltage balancing controller 106 outputs an adjustment current that is added to the measured q-axis current to perform voltage regulation.

[0030] Referring still to Fig. 7, to determine the iadj value which compensates for fluctuations in the DC link voltage, control loop 106 receives sensed voltage values 110 from each of the voltage sensors 82 corresponding to modules 17a, 17b, and 17c in the control district 90, calculates a sum of the voltage values, and divides the sum by the number of modules 17x, which results in the average voltage for the control district 90. The average voltages for each control district 90x can then summed together, and the result can be divided by the number of control districts 90x to provide an overall average. For example, in a system with six control districts 90x, the average voltages of each control district are added, and the result is divided by six to provide a setpoint DC voltage 110 for each of the control districts 90x in the system. This voltage 110 can be compared against voltage 108 at comparator 112, which here can be an average voltage calculated by dividing the DC link voltage 73 by the number of control districts. The control and communication platform plays a pivotal role in obtaining fault-tolerant operations for IMMDs 10, ensuring DC link voltage balancing among inverter modules 17x, load reference torque tracking, and fault-tolerant operation.

[0031] In alternative configurations, the averaged sensed voltages calculated at each of the control districts 90x can be summed to provide an overall sensed voltage 110, and then the sum can be compared to the expected value of DC link voltage 73 (Fig. 5)) at comparator 112. Various other methods of comparing the DC link voltages at the control districts 90x to the overall expected DC link voltage will be apparent to those of skill in the art.

[0032] In alternative configurations, because the modules 17 in each control district are parallel, the voltage can be taken from one sensor 82 (Fig. 4) in each of the control districts 90x. However, acquiring the voltage from all of the sensors in a given module can be advantageous 9QB\630024.00275\ 99023718.3MU1199630024.00275 because the resultant average can minimize the effects of noise at individual sensors in the calculated value and provides some immunity against sensor faults by providing feedback which can be used to determine if the sensors are malfunctioning.

[0033] Referring still to Fig. 7, after comparator 112, the resultant voltage adjustment can be converted to an AC current adjustment value iadj using a proportional control 114, and the resultant iadj 115 is then provided to current regulator 100.

[0034] As described above, the leader controllers 70a are in communication with the global controller 72 and receive commands for driving the motor 62 from the global controller 72. The global controller 72 can be, by way of example, in communication with an external controller or user interface which provides a torque command to the global controller 72. The global controller 72 or the leader controllers 70a can resolve this torque value into idref and iqref commands 102 and 104, respectively, which are used current regulator 100 using, by way of example, a proportional constant and / or a lookup table.

[0035] Referring still to Fig. 7, as described above, the current regulator 100 also receives sampled current values ia, ib, and ic117 from current sensors 80 associated with windings 14a, 14b, 14c. At process step 120 the digital current values are converted into a dq reference frame. First, the digital current values ia, ib, and ic are converted into 2 phase current values ia, and ip using, by way of example, Clarke conversion. The conversion uses the fact that ia + ib + ic = 0, and sets: la = ia.

[0036] ip is then calculated as follows:Ip = (ib + 2ic) / 31 / 2

[0037] The resultant current values la and ip rotate with the rotor. The process step 120 therefore converts the current values from stationary to rotating coordinates. This conversion can be performed using a Park conversion, which converts la and ip to Id and Iq using the rotational angle of the motor acquired from encoder 65 as follows:

[0038] At process step 118, Id is adjusted by iadj. At comparators 122 and 124, current regulator 100 compares the 2-phase currents Iq and the adjusted Id to reference values idref 102 and iqref 104, respectively, and provides the output to proportional integral (PI) controls 126, 128 in which the P control performs amplification control according to the difference of the ideal value10QB\630024.00275\ 99023718.3630024.00275 and the actual measurement, and the I control performs amplification control according to the integration value of the difference. Although the inputs of PI control are the current values of the 2 transformed phases, the outputs are the voltage values of the corresponding 2 phases because the input signals of the motor driver which are the last outputs of the vector control are not current values but voltage values.

[0039] In fault conditions where a module experiences an imbalanced condition, such as when one phase is disabled due to a short circuit, a proportional-integral-resonant (PIR) controller may be deployed in the current regulator 100 to suppress oscillatory components that arise from the imbalance. Fig. 10 shows an example structure of a PIR controller. In the illustrated example, CDris the resonance frequency, and k , kt, and krare controller gains. The controller is tuned as follows: kp= LdCOc, kt= RsX CD ■ kr= 0.001x^ ;

[0040] where CDcis the current controller’s bandwidth. Transitioning from a balanced three-phase system to an imbalanced system introduces a negative-sequence component that rotates at an angular frequency of — D = —171 f , where f is the electrical frequency. Since the Park transformation operates at a reference frame rotating with CD, this imbalance results in a second harmonic component appearing in the dq-frame. In other words, the relative speed between the negative and positive sequences is twice the electrical angular frequency. To suppress this second harmonic, the PIR controller should be tuned accordingly, with the resonant frequency CDrset to 2ty.

[0041] Referring again to Fig. 7, in process step 130, the 2-phase voltage values Vq and Vd obtained through the PI controls 126 and 128 are returned to the stationary coordinate system from the rotating coordinates using a reverse Park conversion to obtain Va and VP, as follows:Va = Vd * cos© - Vq * sin©VP = Vd * sin© + Vq * cos©

[0042] A space vector modulation (SVM) can then be performed to inverse transform the 2-phase voltage back to a 3-phase voltage, where each phase is offset by 120 degrees. The positive and negative phases of input signals A+, B+, C+, A', B', and C’ are acquired by this conversion.11QB\630024.00275\ 99023718.3630024.00275Again, the angle information can be provided by the encoder 65. To reduce torque ripple in the system, carrier interleaving may be implemented across all three-phase subsets, where the carriers of multiple subsets are phase-shifted to achieve smoother overall torque output. For example, the carriers of the six control districts 90x can be phase-shifted by Ts / 6, where Tsis the switching period, resulting in interleaved carrier signals that reduce the overall system torque ripple.

[0043] Using three-dimensional vector notation, each 120 degree axis is set to (100), (010), and (001). Next, each axis is extended to the opposite direction from the origin, where the extension of (100) is centered between (010) and (001) and this extended axis is set to the vector (011). Similarly, as for the extension of (010), the extension is set to (101) and the extension of (001) is set to (110), producing six sectors, with the axes therefore offset at 60 degree angles, also referred to as a space vector hexagon.

[0044] The voltage Va and VP are put on this space as a vector V that is synthesized by vector composition of Va and Vp. Since the synthetic voltage V rotates together with a rotor, it moves from sector to sector in order, and the vector can be sampled at predetermined times as it rotates. To create the output waveform, a fixed cycle T is applied which is sufficiently short that the voltage vector V is essentially standing still. Time T is defined as:T = tl +t2 + t3

[0045] The time of t3 is “time to do nothing” in the sector 0 (abc) is set to (000) or (111) at this time. To assemble symmetric waves, tl and t2 are calculated by a unit of one half, and t3 is calculated by a unit of one fourth. During the whole 1 cycle, time for a, b, and c to be 1 is as follows. a=t 1 +t2+t3 / 2 b=t2+t3 / 2 c=t3 / 2

[0046] The time t3 / 2 of a, b, and c is the time in which a=b=c=l, and in which a=b=c=0, and during this time nothing is done to the motor. The voltage vector V in the sector 0 is decomposed into tl and t2. As a result, the voltage vector V (2 phases) has been changed into 3 phase signals of (Va, Vb, Vc) by space vector modulation. As the voltage vector V rotates through each sector in order, the values of tl and t2 of a, b, and t3 of c change, as do the negative phase values A-, B-, and C-.

[0047] Referring still to Fig. 7, based on the SVM, a three-phase inverter can be used to convert the input DC supply to a three-phase motor output using appropriate switching circuits.12QB\630024.00275\ 99023718.3MU1199630024.00275For example, a three-phase inverter with six switches can be used. In this configuration, there are eight valid switching configurations. Each switching configuration results in a specific voltage applied to the motor terminals. The voltages are basic space vectors and represent their magnitude and direction in a space vector hexagon. The switching states that correspond to the basic space vectors (for direction) and the null vectors (for magnitude) can be combined to approximate a voltage vector of any magnitude, at any position, within the space vector hexagon. For example, for every pulse width modulation (PWM) period, the reference vector is averaged by using a switching sequence of two adjacent space vectors for a specified duration of time and a null vector for the rest of the period.

[0048] The switches are controlled to assure that two switches in the same leg are not simultaneously turned on, which would short the DC supply. This requirement may be met by the complementary operation of the switches within a leg. i.e., if A+ is on then A- is off and vice versa. This leads to eight possible switching vectors for the inverter, VO through V7 with six active switching vectors and two zero vectors, as shown:

[0049] Referring again to Fig. 7, the output of the SVM algorithm of process 130 can be used to create gate pulse timing to control pulse-width modulation (PWM) at the three phase inverter switching circuit to create AC output waveforms which drive the 3 phase AC powered motor at varying speeds by calculating on- and off-gating times to generate the double hump 13QB\630024.00275\ 99023718.3MU1199630024.00275 modulation waveforms, and uses the gating times to generate appropriate gate pulses for the inverter switches. By controlling the switching sequence, and consequently the ON time duration of pulses, any voltage vector with varying magnitude and direction is achievable for every PWM period. Here, because the windings for each phase in the three phase circuits are associated with individual modules 17a, 17b, 17c, commands for the individual phases of the three phase motor are transmitted to and controlled by individual boards 68a, 68b, 68c, and their corresponding controllers 70a, 70b, 70c.

[0050] The process described above can be performed by the leader controller 70a of each control district 90, or by a combination of the global controller 72, lead controller 70a, and, in some cases, also the follower controllers 70b, 70c. Microcontrollers that include vector engines for performing these calculations are also available from Toshiba America, New York, New York, including, by way of example, the Arm® Cortex®-M4 Microcontrollers for Motor Control.

[0051] Referring now to Figs. 8A and 8B, a flow chart illustrating operation of the leader controllers 70a in each control district 90x is shown. Referring first to Fig. 8A, the controller 70a can receive a torque command (step 200) and the sensed angle of the motor (step 202) from the global controller 72. The leader controller 70a can read the voltage at voltage sensor 82 and transmit the voltage value to the global controller 72, which can transmit the measured voltage to the leader controllers 70a in other control districts 90x. The leader controller 70a receives the voltage values measured at each of the other control districts 90x from the global controller 72 and can use these values to calculate iadj using process 106, described above. Although as illustrated here, the leader controller 70a calculates iadj, the global controller 72 can calculate iadj and forward the calculated value to the leader controllers 70a in all of the control districts 90x.

[0052] Referring now to Fig. 8B, the leader controller 70a senses current at current sensor 80 corresponding to winding 14a and transmits the sensed current to the first follower controller 70b (step 210). The first follower controller 70b senses the current at winding 14b and can then forward the current associated with winding 14a and the current associated with winding 14b to the second follower controller 70c. Second follower controller 70c senses current at winding 14c and transmits the current values for all of the followers to the leader controller 70a (step 212). When the leader 70a has the input currents from each of the followers, and the calculated iadj, the leader controller can apply current regulator 100, which determines Va, Vb, and Vc and / or on and off gating times for the switching electronics 78 associated with controller 70a (step 214). The controller 70a then transmits the calculated voltages Vb and Vc to the follower controllers 70b and 14QB\630024.00275\ 99023718.3MU1199630024.0027570c in the control district 90 (step 216) and apply calculated gate timing commands to the winding associated with the leader controller 70a. The process can repeat until the leader controller 70a receives a signal from the global controller 72 to shut down. As described above, the controller 70a transmits voltage values Vb and Vc to the follower controllers 70b and 70c. The follower controllers 70a and 70b can then apply SVM or similar algorithms to determine the gate switching on off times for driving the winding 14c, 14b associated with the controllers. Alternatively, the leader controller 70a can determine gate timing for each of the controllers 70a, 70b, and 70c, and transmit the gate timing to the controllers 70b and 70c through the network.

[0053] In some alternative embodiments, the leader 70a can transmit all of the collected current data follower controllers 70b and 70c, and the follower controller 70b and 70c can then each apply current regulator 100 to calculate Va, Vb, and Vc, and forward these values through the daisy chain network until all processors have the voltages calculated by each controller 70a, 70b, and 70c. Each follower controller 70b and 70c can then compare the voltages received from the leader controller 70a to verify that the calculations are correct, or within an expected tolerance. If the calculated voltages Va, Vb, and Vc match, the controllers 70b and 70c can apply the corresponding voltage to the corresponding winding. If an error occurs, the controller uses the daisy chain connection to provide an error signal to the global controller 72.

[0054] Referring now to Fig. 9, a timing chart of communications between the leader controller 70a and the follower controllers 70b and 70c for acquiring and transmitting sensor values is shown. During a first timing period Tl, output from the voltage and current sensors 80 and 82 (Fig. 4) can be sampled and converted to digital signals by signal conditioning circuits 79 and 81, as described above, in each of the controllers 70a, 70b, 70c. ADCs in each controller 70a, 70b, and 70c begin data capture, while CLA task #4 handles data shifting in filters and variables. In the leader controller 70a, ADC inputs are assigned to registers, and ia is prepared for transmission during subsequent timing phases T2 and T3. In the follower controllers 70b and 70c, during T2, only ADC inputs are assigned. At T4, controller 70b receives ia from controller 70a and transmits it along with ib to controller 70c. In T5, controller 70c sends ia, ib, and ic back to controller 70a. At this point, controller 70a has all of the current feedback data to perform the dq current control calculations during T6. Controller 70a then sends the voltages Vb and Vc to controller 70b, which control the corresponding switching circuits to produce Vb at winding 14b. In T7, controller 70b passes Vc to controller 70c, and by T8, all modules 17a, 17b, and 17c and their corresponding15QB\630024.00275\ 99023718.3MU1199630024.00275 controllers 70a, 70b, and 70c have their reference voltages, and can apply PWM commands to the switching circuits in the next period.

[0055] In one implementation, the leader and follower controllers were successfully implemented using the C2000 microcontroller series from Texas Instruments of Austin. Texas. The controllers in the C2000 series include onboard receivers and transmitters which use a fast serial interface (FSI), a Texas Instruments protocol which provides a reliable and high speed communication platform having two independent Transmit (TX) and Receive (RX) cores. During the data transfer process, the C2000 series also provides inherent integrity checks before the transmitting and after receiving events without the interaction of the central processing unit.

[0056] The frame structures for the FSI communication can include Preamble and Postamble phases in which the data signal will be held high for four clock edges. The Preamble phase can flush a receiver module to prepare it for receiving a transmitted frame. The start and the end of a frame (SOF and EOF) can be identified with defined sequences of four bits. For example, a frame of 1001 bits can mark the start of the frame while a frame of 0110 can indicate the end of the frame. A Ping Frame and an Error Frame can also be used, where the Ping Frame can be used to check the communications link, and can be, for example, a transmission of 0000, and the error frame can be a transmission of 1111. A receiver corresponding to each controller 70a, 70b, and 70c can have a dedicated watchdog for monitoring for the Ping transmission. There are three parts of the Data Frame that a user can set before transmitting the data, i.e., User Data, Data, and Frame Tag. The User Data is an 8-bit value which contains the data that is being transferred which could have any size between 1 word (16-bit data) and 16 words. A CRC Byte can contain the result of the Cyclic Redundancy Check (CRC) which can be generated both by hardware and software to verify the integrity of the received data.

[0057] Although a daisy chain network is described above, other types of network communications systems can also be used. For example, where the leader controller has multiple receivers, each can be connected to a follower controller to receive transmissions from the followers.

[0058] The system is designed to support fault-tolerant operation. Given the redundant architecture comprising multiple identical modules 17x, if a fault occurs in any module 17x, the torque contribution of the corresponding control district 90x can be reduced or set to zero, depending on the fault severity. To maintain overall system performance, the remaining healthy modules 17x redistribute the torque and power demand among themselves. In addition to 16QB\630024.00275\ 99023718.3MU1199630024.00275 modifying torque references, DC link voltage 73 references also require adjustment during fault scenarios. Since the power flow in each control district 90x is determined by its individual DC link voltage 73, selectively adjusting these voltages enables power redistribution under fault conditions. For example, if a short circuit is detected in one of the motor windings 14x, the corresponding switching circuit 78 immediately opens all switches to avoid catastrophic failure. As a result, the affected control district 90x operates with only two healthy phases, introducing current imbalance. The system can continue to operate under such fault conditions, with the remaining healthy modules 17x compensating for the reduced output of the faulty module 17x.

[0059] Within this specification, embodiments have been described in a way which enables a clear and concise specification to be written, but it is intended and will be appreciated that embodiments may be variously combined or separated without parting from the invention. For example, it will be appreciated that the features described herein are applicable to all aspects of the embodiments described herein. Further, it is to be understood that the present disclosure is not limited in its application to the details of construction and the arrangement of components set forth in the description or illustrated in the drawings. The present disclosure is capable of other configurations and of being practiced or of being carried out in various ways. For example, although a specific ordered series of steps is described above, the order of these steps can be varied.

[0060] Additionally, although calculations are described at specific controllers in the system, the controller providing a specific function can be varied. For example, calculations comparing the expected DC link voltage versus a sum of the sensed DC link voltages corresponding to each control district can be performed at the leader controller for each control district or at the global controller and transmitted to the control districts. Further, although a single global controller 72 is illustrated here, two or more controllers can be combined to form the global controller, each controller receiving all communications, performing calculations, and crosschecking results.

[0061] Additionally, although an H-bridge inverter is described above as the switching circuit, other types of inverter circuits including, for example, full or half bridge inverters, push- pull inverters, sine and modified sine wave inverters can be used. As described above, the signal processing circuits can include amplification and filtering circuits. The amplification and filtering circuits can include transistors and / or operational amplifiers, resistors, and capacitors, as is known in the art.17QB\630024.00275\ 99023718.3MU1199630024.00275

[0062] Thus, it will be appreciated by those skilled in the art that, while the disclosure has been described above in connection with particular non-limiting examples and examples, the disclosure is not necessarily so limited, and numerous other constructions, examples, uses, modifications and departures from the non-limiting examples, examples and uses are intended to be encompassed by the claims attached hereto. The figures, similarly, depict selected configurations and are not intended to limit the scope of the present disclosure. The present disclosure is to be accorded the widest scope consistent with the principles and features disclosed herein.

[0063] Various features and advantages of the invention are set forth in the following claims.

[0064] The present disclosure has described one or more preferred embodiments, and it should be appreciated that many equivalents, alternatives, variations, and modifications, aside from those expressly stated, are possible and within the scope of the disclosure.18QB\630024.00275\ 99023718.3

Claims

630024.00275CLAIMS1. An integrated modular motor comprising: a rotor comprising a plurality of permanent magnets; a stator comprising a plurality of modules, wherein each of the plurality of modules comprises: a winding; and a control board, the control board for each module comprising: a switching circuit coupled to the winding; a sensor for sensing current in the winding; and a controller configured to: control switching of the switching circuit to provide an alternating current to the winding, the alternating current developing an electromagnetic field in the winding to drive the permanent magnets in the rotor; communicate with the control boards corresponding to the other of the plurality of modules, and to communicate sensed current information to the other modules; wherein the plurality of modules are arranged in a plurality of control districts, each control district comprising an odd-numbered set of n modules connected in parallel, each of the odd-numbered set of n modules in each control district being configured to produce a current offset from a current produced by the other of the odd-numbered set of n modules of the control district, and wherein the controller in one of the of the odd-numbered set of n modules includes a leader controller for controlling communications in the control district, and the other controllers in the control district are follower controllers; and a global controller, the global controller configured to provide commands to each of the leader controllers to drive the rotor.19QB\630024.00275\ 99023718.3MU1199630024.002752. The integrated modular motor of claim 1, wherein the leader and the n-1 follower controllers are connected in a daisy chain, each of the leader controller and the n-1 follower controllers is programmed to acquire a sensed current corresponding to the winding, and the sensed currents are transmitted as follows: a. the leader controller transmits the corresponding sensed current to a predetermined first one of the n-1 follower controllers; b. in a predetermined chain of follower controllers, the first one of the n-1 controllers transmits the sensed current corresponding to the leader controller and the sensed current corresponding to the receiving one of the n-1 controllers to another of the n-1 controllers; c. step(b) is repeated, with each of the n-1 follower controllers in the predetermined chain adding a sensed current corresponding to the receiving follower controller and the last follower controller in the predetermined chain transmits the sensed currents corresponding to the leader controller and to each of the follower controllers to the leader controller.

3. The integrated modular motor of claim 1, wherein the motor is a three-phase motor, and the leader provides a sensed current value corresponding to the winding associated with the leader controller to a first follower controller, the first follower controller provides a sensed current value associated with the first follower controller and a sensed current value corresponding to the winding associated with the first follower controller to a second follower controller; and the second follower controller provides the sensed current value associated with the first follower controller and a sensed current value associated with the second follower controller current value to the leader controller.

4. The integrated modular motor of claim 3, wherein the leader controller is programmed to calculate and transmit a pulse width modulation command to the switching circuit associated with each of the first and second follower controllers based on the sensed current values, and to control the switching circuit associated with the leader controller based on the calculated pulse width modulation command.20QB\630024.00275\ 99023718.3MU1199630024.002755. The integrated modular motor of claim 4, wherein the plurality of control districts are connected in series to a direct current link voltage source, and wherein the leader controller is further programmed to calculate an adjustment current based on a difference between an actual direct current link voltage and a measured direct current link voltage.

6. The integrated modular motor of claim 4, wherein the leader controller is programmed to perform a Clarke conversion, a Park conversion, and a space vector modulation to determine pulse width modulation gate pulses to be applied to the windings associated with each of the leader controller and the follower controllers, and to transmit these values to the follower controllers.

7. The integrated modular motor of claim 5, wherein each of the leader controllers is configured to provide voltage feedback to the global controller, and the global controller is configured to calculate a current adjustment based on a comparison of the voltage feedback and an expected value of a de link voltage, and to provide the current adjustment to each of the leader controllers.

8. The integrated modular motor of claim 1, wherein the switching circuit is an H- bridge inverter.

9. The integrated modular motor of claim 1, wherein the leader controllers are in communication with and receive commands from the global controller.

10. The integrated modular motor of claim 1, wherein the plurality of modules comprises eighteen modules.

11. The integrated modular motor of claim 1, wherein the plurality of control districts comprises six.

12. The integrated modular motor of claim 1, wherein the global controller is configured to detect a fault condition in one of the plurality of modules and to redistribute torque demand among remaining healthy modules in response to the fault condition.21QB\630024.00275\ 99023718.3MU1199630024.0027513. The integrated modular motor of claim 12, wherein the fault condition comprises a short circuit in one of the windings, and the global controller is configured to disable the switching circuit associated with the faulty winding and adjust torque references for the remaining modules in the affected control district.

14. The integrated modular motor of claim 13, wherein the leader controller in the affected control district is configured to implement a proportional-integral-resonant controller to suppress oscillatory components arising from current imbalance caused by the fault condition.

15. The integrated modular motor of claim 12, wherein the global controller is configured to adjust DC link voltage references for each control district during fault conditions to redistribute power among the plurality of control districts.

16. The integrated modular motor of claim 15, wherein the DC link voltage reference for a control district containing a faulty module is reduced, and the DC link voltage references for remaining healthy control districts are increased to maintain overall system power balance.

17. The integrated modular motor of claim 12, wherein the motor is configured to continue operating with reduced torque contribution from a faulty control district while maintaining overall torque tracking performance through compensation by healthy control districts.22QB\630024.00275\ 99023718.3MU1199630024.0027518. A stator for use in an integrated modular motor comprising: a plurality of modules, wherein each of the plurality of modules comprises: a winding; and a dedicated control board, the dedicated control board for each module comprising: an inverter circuit coupled to the winding; and a controller configured to: control switching of the inverter circuit; and communicate with at least one of the dedicated control boards corresponding to the other of the plurality of modules; wherein the plurality of modules are arranged in a plurality of control districts, each control district comprising a set of three modules connected in parallel, each of the three modules in each control district being configured to produce a current offset one hundred and twenty degrees from a current produced by the other modules of the control district, and wherein the controller in one of the sets of three modules includes a leader controller, and the other controllers in the control district are first and second follower controllers.

19. The stator of claim 18, wherein the leader and the first and second follower controller are connected in a daisy chain, wherein the leader provides a sensed current corresponding to the leader controller to the first follower controller, the first follower controller provides the sensed current corresponding to the leader controller and a sensed current corresponding to the first follower controller to the second follower controller, and the second follower controller transmits the sensed current corresponding to the leader controller, the sensed current corresponding to the first follower controller, and the sensed current corresponding to the second follower controller to the leader controller.

20. The stator of claim 18, wherein the plurality of control districts are connected in series to a direct current voltage source.23QB\630024.00275\ 99023718.3MU1199630024.0027521 . The stator of claim 18, wherein the follower controllers are configured to provide voltage and current feedback to the leader controllers corresponding to each control district, and wherein the leader controllers are configured to adjust commands to the follower controller to balance a de link voltage.

22. The stator of claim 21, wherein the leader controllers are configured to drive the switches in the inverter.

23. The stator of claim 18, wherein the inverter circuit is an H-bridge inverter.

24. The stator of claim 18, further comprising a global controller configured to provide commands to each of the leader controllers, wherein the leader controllers are in communication with and receive commands from the global controller.

25. The stator of claim 18, wherein the plurality of modules comprises eighteen modules.

26. The stator of claim 18, wherein the plurality of control districts comprises six.

27. A method of fault-tolerant operation for an integrated modular motor comprising a plurality of modules arranged in control districts comprising an odd-numbered set of modules connected in parallel, each of the odd-numbered set of modules in each control district being configured to produce a current offset from a current produced by the other of the odd-numbered set of modules of the control district, the method comprising: detecting a fault condition in one of the plurality of modules; disabling a switching circuit associated with the faulty module; reducing torque contribution from a control district containing the faulty module; redistributing torque demand among remaining healthy modules; and adjusting DC link voltage references for each control district to maintain power balance.

28. The method of claim 27, further comprising implementing a proportional-integral- resonant controller in the control district containing the faulty module to suppress second harmonic oscillations caused by current imbalance.24QB\630024.00275\ 99023718.3

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