Active motor current limiting for synchronous motor drives

Abstract

The present application discloses active motor current limiting of a synchronous motor drive. A method of controlling the operation of an electric motor includes: calculating a voltage-based torque limit based on a voltage constraint of a direct current (DC) bus that supplies power to an inverter to power the electric motor; calculating a current-based torque limit based on a motor current limit; determining a final torque limit based on: a voltage-based torque limit and a current-based torque limit; determining a limited command torque based on a torque command and a final torque limit; and generating at least one current command based on at least the limited command torque. A control system for controlling the operation of an electric motor is also provided.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This patent application claims priority to U.S. Provisional Patent Application Serial No. 63 / 088,585 filed on October 7, 2020, the entire contents of which are incorporated herein by reference. Technical Field

[0003] The present disclosure relates to electric machines, and in particular to using a motor drive to control the operation of an electric machine. Background Art

[0004] Vehicles such as automobiles, trucks, sport utility vehicles, crossovers, minivans, boats, aircraft, all-terrain vehicles, recreational vehicles, or other suitable vehicles often include one or more electric machines, such as electric motors, etc. For example, a vehicle may include one or more multi-phase electric machines configured to control various aspects of a steering system of the vehicle.

[0005] Power management is an important consideration when controlling an electric motor drive to regulate the power delivered to and recovered from the electric motor. Active power management involves considering multiple constraints simultaneously to determine the achievable torque. Constraints include supply voltage, supply (regeneration) current, and inverter (motor) current.

[0006] Optimal current command search techniques are used in some motor controllers, such as for controlling permanent magnet synchronous motors (PMSMs) in electric power steering (EPS) systems. Such techniques can take multiple inputs, including, for example, direct current (DC) bus voltage, motor speed, torque command, and machine parameters, to calculate optimal d-axis current commands and q-axis current commands based on these inputs. The optimal or optimized current commands can be d-axis current commands and q-axis current commands that are calculated or otherwise selected so as to satisfy one or more constraints (e.g., DC bus voltage constraints) while also causing the PMSM to produce the desired torque using the least amount of current.

[0007] Therefore, the torque output of the PMSM is maximized with the minimum current amplitude, which helps to reduce copper losses. In this technique, the actual machine current amplitude is not limited to a specific value. Instead, the technique makes the machine current amplitude as low as possible under given operating conditions. Summary of the invention

[0008] The present disclosure generally relates to using a motor drive to control the operation of an electric machine.

[0009] One aspect of the disclosed embodiment includes a method of controlling operation of an electric machine. The method includes: calculating a voltage-based torque limit based on a voltage constraint of a direct current (DC) bus that supplies power to an inverter to power the electric machine; calculating a current-based torque limit based on a motor current limit; determining a final torque limit based on: the voltage-based torque limit and the current-based torque limit; determining a limited command torque based on a torque command and the final torque limit; and generating at least one current command based at least on the limited command torque.

[0010] One aspect of the disclosed embodiment includes a control system for controlling the operation of an electric machine. The control system includes a processor and a memory. The memory includes instructions that, when executed by the processor, cause the processor to: calculate a voltage-based torque limit based on a voltage constraint of a direct current (DC) bus that supplies power to an inverter to power the electric machine; calculate a current-based torque limit based on a motor current limit; determine a final torque limit based on: a voltage-based torque limit and a current-based torque limit; determine a limited command torque based on a torque command and a final torque limit; and generate at least one current command based on at least the limited command torque.

[0011] One aspect of the disclosed embodiment includes a control system for controlling the operation of an electric motor. The control system includes an inverter including a plurality of switches operable to supply alternating current to the electric motor. The control system also includes a controller operable to: calculate a voltage-based torque limit based on a voltage constraint of a direct current (DC) bus that supplies power to the inverter to power the electric motor; calculate a current-based torque limit based on a motor current limit; determine a final torque limit based on: a voltage-based torque limit and a current-based torque limit; determine a limited command torque based on a torque command and a final torque limit; generate at least one current command based at least on the limited command torque; and selectively control the plurality of switches within the inverter based on at least one current command so that the inverter supplies alternating current to the electric motor.

[0012] These and other aspects of the disclosure are disclosed in the following detailed description of the embodiments, the appended claims and the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] The present disclosure is best understood by the following detailed description when read in conjunction with the accompanying drawings. It is emphasized that, according to common practice, the various features of the drawings are not drawn to scale. Instead, the sizes of the various features are arbitrarily expanded or reduced for clarity.

[0014] Figure 1 A schematic diagram of an electric power steering system in accordance with the principles of the present disclosure is generally shown.

[0015] Figure 2 A controller according to the principles of the present disclosure is generally shown.

[0016] Figure 3 A block diagram of a motor controller in accordance with the principles of the present disclosure is generally shown.

[0017] Figure 4 A block diagram generally illustrates an example algorithm for controlling an electric motor in accordance with aspects of the present disclosure.

[0018] Figures 5A-5D FIG. 1 shows a graph generally illustrating four different I values ​​for searching for maximum torque that satisfies DC bus voltage and inverter / motor current limit constraints in accordance with the principles of the present disclosure. d ,I q Trajectory.

[0019] Figure 6 is a flow chart generally illustrating a method of controlling the operation of an electric machine according to the principles of the present disclosure. DETAILED DESCRIPTION

[0020] The following discussion is directed to various embodiments of the present disclosure. Although one or more of these embodiments may be preferred, the disclosed embodiments should not be interpreted or otherwise used as limiting the scope of the present disclosure, including the claims. In addition, it will be understood by those skilled in the art that the following description has a wide range of applications, and the discussion of any embodiment is intended only to be an exemplary discussion of that embodiment, and is not intended to imply that the scope of the present disclosure, including the claims, is limited to that embodiment.

[0021] As discussed above, vehicles such as automobiles, trucks, sport utility vehicles, crossovers, minivans, boats, aircraft, all-terrain vehicles, recreational vehicles, or other suitable vehicles often include one or more electric machines, such as electric motors, etc. For example, a vehicle may include one or more multi-phase electric machines configured to control various aspects of a steering system of the vehicle.

[0022] Optimal current command search techniques are used in some motor controllers, such as for controlling permanent magnet synchronous motors (PMSMs) in electric power steering (EPS) systems. Such techniques can take multiple inputs, including, for example, DC bus voltage, motor speed, torque command, and machine parameters, to calculate optimal d,q axis current commands based on these inputs. The calculated d,q axis current commands can be selected to satisfy the DC bus voltage constraint while also optimizing the calculated d,q axis current commands for torque / current ratio.

[0023] Therefore, the torque output of the PMSM is maximized with the minimum current amplitude, which helps to reduce the copper loss in the windings of the PMSM. In this technology, the actual machine current amplitude is not limited to a specific value. Instead, the technology makes the machine current amplitude as small as possible under given operating conditions.

[0024] According to one aspect of the present disclosure, the motor current is limited is taken as a constraint in the optimization technique, where both the DC bus voltage and the machine current are kept within specified values.

[0025] According to one aspect of the present disclosure, a method of controlling the operation of an electric motor includes limiting the motor current. and the voltage constraint V of the DC bus 215 DC , both of which are used as constraints to solve the optimization problem, where the DC bus voltage and the machine current I i Both remain within the corresponding specified values. In addition to the voltage constraint V DC In addition, the motor current limit is considered as another constraint. The goal of the method and system of the present disclosure is to find a voltage constraint V that satisfies the DC bus 215. DC and motor current limit The maximum achievable torque.

[0026] Figure 1 A schematic diagram of an electric power steering system (EPS) 40 suitable for implementing the disclosed technology is generally shown. The EPS includes a steering mechanism 36 that includes a rack-and-pinion type mechanism having a toothed rack (not shown) within a housing 50 and a pinion (also not shown) located below a gear housing 52. When the operator input, hereinafter represented as the steering wheel 26 (e.g., hand wheel, etc.), is rotated, the upper steering shaft 29 is rotated, and the lower steering shaft 51 connected to the upper steering shaft 29 by a universal joint 34 causes the pinion to rotate. The rotation of the pinion causes the rack to move, which moves the tie rods 38 (only one shown), which in turn moves the steering knuckles 39 (only one shown), which rotate the steerable wheel(s) 44 (only one shown).

[0027] Electric power steering assistance is provided by a control system 24, which includes a controller 16 and an electric motor 19, which may be a permanent magnet synchronous motor (PMSM) and is also represented as motor 19. The controller 16 is powered by a vehicle power supply 10 via line 12. The controller 16 receives a vehicle speed signal 14 representing the vehicle speed from a vehicle speed sensor 17. The steering angle is measured by a position sensor 32, which may be an optically encoded sensor, a variable resistance sensor, or any other suitable type of position sensor, and which provides a position signal 20 to the controller 16. The motor speed may be measured using a tachometer or any other device and transmitted to the controller 16 as a motor speed signal 21. The position sensor 32 may be represented as ω. m The motor speed is measured, calculated, or a combination of measurement and calculation. For example, the motor speed ω m is calculated as the change in motor position θ measured by the position sensor 32 over a specified time interval. For example, it can be calculated according to the equation ω m =Δθ / ΔtThe motor speed ω m Determined as the derivative of the motor position θ, where Δt is the sampling time and Δθ is the change in position during the sampling interval. Alternatively, the motor speed can be derived from the motor position based on the rate of change of position with respect to time. It will be appreciated that there are many well-known methods for performing the function of the derivative.

[0028] As the steering wheel 26 is turned, the torque sensor 28 senses the torque applied to the steering wheel 26 by the vehicle operator. The torque sensor 28 may include a torsion bar (not shown) and a variable resistor type sensor (also not shown) that outputs a variable torque signal 18 to the controller 16 that is related to the amount of twist on the torsion bar. Although this is one type of torque sensor, any other suitable torque sensing device used with known signal processing techniques will suffice. In response to various inputs, the controller sends a command 22 to the motor 19, which provides torque assistance to the steering system through the worm 47 and worm gear 48, thereby providing torque assistance for vehicle steering.

[0029] It should be noted that while the disclosed embodiments are described with reference to motor control for electric steering applications, it will be understood that such references are illustrative only, and the disclosed embodiments may be applied to any motor control application employing an electric motor, e.g., steering, valve control, etc. In addition, the references and descriptions herein may be applicable to various forms of parameter sensors, including but not limited to torque, position, speed, etc. It should also be noted that hereinafter, for the sake of brevity and simplicity, references herein to electric machines, including but not limited to motors, will only refer to motors without limitation.

[0030] In the control system 24 as depicted, the controller 16 uses torque, position, speed, etc. to calculate (one or more) commands to deliver the required output power. The controller 16 is arranged to communicate with various systems and sensors of the motor control system. The controller 16 receives signals from each system sensor, quantifies the received information, and provides (one or more) output command signals in response thereto, in this case, for example, to the motor 19. The controller 16 is configured to develop (one or more) corresponding voltages output from an inverter (not shown), which can be optionally combined with the controller 16 and will be referred to as the controller 16 herein, so that when (one or more) corresponding voltages are applied to the motor 19, the desired torque or position is generated. In one or more examples, the controller 16 operates as a current regulator in a feedback control mode to generate the command 22. Alternatively, in one or more examples, the controller 16 operates in a feedforward control mode to generate the command 22. Because these voltages are related to the position and speed of the motor 19 and the desired torque, the position and / or speed of the rotor and the torque applied by the operator are determined. The position sensor 32 is connected to the steering shaft 51 to detect the angular position θ. The position sensor 32 can sense the rotational position based on optical detection, magnetic field changes, or other methods. The position sensor 32 may include one or more potentiometers, resolvers, synchronizers, encoders, etc. The position sensor 32 outputs a position signal 20, which indicates the angular position of the steering shaft 51 and thereby the angular position of the motor 19.

[0031] The desired torque may be determined by one or more torque sensors 28 transmitting a torque signal 18 indicative of the applied torque. Such torque sensors 28 and the torque signal(s) 18 therefrom may be responsive to a flexible torsion bar, T-bar, spring, or similar device (not shown) configured to provide a response indicative of the applied torque.

[0032] Position signal 20, motor speed signal 21, and (one or more) torque signal 18 are applied to controller 16. Controller 16 processes all input signals to generate values ​​corresponding to each signal, thereby obtaining rotor position values, motor speed values, and torque values ​​that can be used for processing in the algorithm specified in this article. It is usually also desirable to linearize, compensate, and filter the measurement signals such as those described above to enhance the characteristics of the acquired signal or eliminate undesirable characteristics of the acquired signal. For example, the signal can be linearized to increase the processing speed or to solve the large dynamic range of the signal. In addition, frequency or time-based compensation and filtering can be used to eliminate noise or avoid undesirable spectral characteristics.

[0033] In order to perform the specified functions and the desired processing, and the calculations therefor (e.g., identification of motor parameters, (one or more) control algorithms, etc.), the controller 16 may include, but is not limited to, (one or more) processors, (one or more) computers, (one or more) DSPs, memories, storage devices, (one or more) registers, timing, (one or more) interrupts, (one or more) communication interfaces, and input / output signal interfaces, etc., and combinations including at least one of the foregoing. For example, the controller 16 may include input signal processing and filtering to enable accurate sampling and conversion or acquisition of such signals from the vehicle's communication interface.

[0034] like Figure 2 Controller 16 may include any suitable controller as generally shown in FIG. 1 . Controller 16 may be configured to control, for example, various aspects of the vehicle (e.g., various aspects of the electric power steering system and / or other suitable features or components of the vehicle). Controller 16 may include a processor 60 and a memory 62.

[0035] The processor 60 may include any suitable processor, such as those described herein. Additionally or alternatively, the controller 16 may include any suitable number of processors in addition to or in addition to the processor 60. The memory 62 may include a single disk or multiple disks (e.g., a hard drive) and include a storage management module that manages one or more partitions within the memory 62. In some embodiments, the memory 62 may include flash memory, semiconductor (solid-state) memory, etc. The memory 62 may include random access memory (RAM), read-only memory (ROM), or a combination thereof. The memory 62 may include instructions that, when executed by the processor 60, cause the processor 60 to at least control various functions of the vehicle.

[0036] In some embodiments, the controller 16 can be configured to control various aspects of the motor (eg, the motor control system 200), such as Figure 3 . In some embodiments, as generally shown, the motor control system 200 may include a three-phase PMSM controller. However, the motor control system 200 may include any suitable number of phases. Additionally or alternatively, although the motor control system 200 is generally shown and described as being associated with a vehicle and its systems, the motor control system 200 may be configured to control any suitable application or be operatively associated with any suitable application in addition to (or in addition to) controlling the vehicle (e.g., the motor 19 may be used in any suitable application other than a vehicle, and the principles of the present disclosure may apply accordingly).

[0037] The present disclosure provides a motor control system 200 for controlling the operation of an electric machine (e.g., motor 19). The present disclosure can be applied to control various types of synchronous machines (e.g., PMSM, wound-pole machines, synchronous reluctance machines, etc.). The principles of the present disclosure can be used to control salient-pole machines and / or non-salient-pole machines. The principles of the present disclosure can be used to control wound-rotor synchronous machines.

[0038] The current reference calculator 202 converts the torque command T c Converted into d / q current reference I dqc , the d / q current reference I dqc It is then sent to the current controller 206. The current controller 206 can be a feedback regulator that uses the current measurement, or a feed-forward compensator. The temperature T can be fed to the parameter compensator 204 to adjust the PMSM electrical parameters as needed. The current controller 206 then generates a d / q voltage command, which is equivalent to the commanded modulation index m i and phase advance angle δ. m i and δ are converted into equivalent duty cycle signals d for each of the three phases a, b, c by the duty cycle generator 210 of the power converter switching module 208. a d b d c .

[0039] Once the equivalent duty cycle signal d is generated for each phase a d b d c , the pulse width modulator 212 generates corresponding on-times t for different switches (eg, FETs) in the phase arms of the power converter (eg, the inverter 216). a ,t b ,t c . Duty cycle signal d a d b d c Can be collectively labeled as d a,b,c , and the conduction time t a ,t b ,t c Can be collectively labeled as t a,b,c The inverter 216 powered by the power supply 214 then supplies the desired voltage to the motor (eg, motor 19), which generates a phase current I a ,I b ,I c and electromagnetic torque T e The inverter 216 is connected to the power supply 214 via a direct current (DC) bus 215. The position θ is then measured. r and phase current I a ,I b ,Ic The current is fed back to the position sensor 220 and the current sensor 222 of the control system to close the control loop. a ,I b ,I c Can be collectively labeled as I a,b,c The measured position θ m Used together with the phase current to calculate the measured d / q current I dqm , which is used for closed-loop current control. Voltage source inverters (VSI) are commonly used as power converters in PMSM-based electric drives. Each phase of the motor 19 is connected to a corresponding phase arm of the inverter 216, and each phase arm may have two or more switches.

[0040] Although the actual machine design and construction are different for three-phase PMSM and multi-phase (greater than three-phase) PMSM, for all these machines the same principles of vector control in a synchronous or d / q reference frame are possible by using appropriate transformation matrices to convert the phase currents and voltages into equivalent DC quantities in the synchronous coordinate frame.

[0041] Figure 4 1 is a block diagram of an example algorithm 300 for controlling an electric machine according to aspects of the present disclosure. Specifically, the example algorithm 300 includes a torque capability determination block 302 configured to determine a limited command torque T CmdLmtd .

[0042] The torque capacity determination block 302 includes an inverter / motor current limit block 304 that is configured to determine the torque capacity based on the motor current limit. Determining the torque limit based on current Motor current limit The current limit may be the smaller of the current values ​​that the inverter 216 and / or the motor (e.g., PMSM 19) are rated to handle. Alternatively or additionally, the motor current limit It may be based on the current rating of only the motor (e.g., PMSM 19) or the inverter 216. For example, where it is known that the current rating of the inverter 216 or PMSM 19 is not a limiting factor (e.g., where the current rating of the inverter 216 is significantly higher than the current rating of the motor).

[0043] The torque capacity determination block 302 also includes a voltage limit block 306 that is configured to constrain the voltage V of the DC bus 215 based on the voltage V DC To determine the torque limit based on voltage Voltage Constraint V DC The voltage constraint V DCThe voltage at which the DC bus 215 is rated to operate may be included. The DC bus 215 is constrained by a voltage V DC Operating at voltages other than those specified in the DC bus 215 may have adverse consequences, such as equipment failure and / or damage to hardware connected to the DC bus 215 .

[0044] The torque capacity determination block 302 also includes a torque limit arbitration block 308 configured to determine a final torque limit T based on: pk : Torque limit based on current and voltage-based torque limiting

[0045] The torque capacity determination block 302 also includes a torque command limit block 310 that determines the torque based on the commanded torque T c and the final torque limit T from the torque limit arbitration block 308 pk Determine the limited command torque T CmdLmtd The torque command limiting block 310 may be configured to limit the command torque T CmdLmtd Set to the commanded torque T Cmd and final torque limit T pk The smaller one.

[0046] The example algorithm 300 also includes a current command calculation block 320 configured to determine d-axis and q-axis current commands I for controlling operation of the inverter 216. * dq The current command calculation block 320 includes a maximum torque per ampere block 322 , which can be based on the limited command torque T CmdLmtd Determine preliminary motor current value Preliminary motor current value The optimization may be performed based on the maximum torque per ampere determination, which may include performing one or more calculations and / or other methods. Optimized motor current value A preliminary d-axis current may be included and the initial q-axis current The current command calculation block 320 also includes a maximum torque per voltage block 324, which can be configured to determine the d-axis and q-axis current commands I * dq , the maximum torque satisfies the limited command torque T CmdLmtd And optimized for voltage.

[0047] Used to determine the current limit of the motor and the voltage constraint V of the DC bus 215 DC The mathematical expression of the torque limit can include the following equation:

[0048] Vd =RI d +ω e L q I q (1)

[0049] V q =RI q +K e ω m -ω e L d I d (2)

[0050]

[0051]

[0052]

[0053] Figures 5A-5D FIG. 1 shows a graph generally illustrating four different I values ​​for searching for maximum torque that satisfies a DC bus voltage constraint and a motor current limit constraint according to the principles of the present disclosure. d ,I q Trajectory.

[0054] Specifically, Figure 5A A first plot 400 is included which shows the calculated current limit to meet the motor current limit. The d-axis current I d and q-axis current I q The first plot line 400 is the d-axis current I d The first q-axis current I based on the motor current equals to the predetermined minimum value qi1 With the d-axis current I d The second q-axis current I based on the motor current is equal to the predetermined maximum value. qi2 The predetermined minimum value may be, for example, zero or a positive or negative value that is less than the predetermined maximum value. Figure 5A Also included is a second plot line 402 which shows the calculated voltage V of the DC bus 215 that satisfies the voltage constraint V DC The d-axis current I d and q-axis current I q The second plot line 402 is the d-axis current I d The first voltage-limited q-axis current I qv1 With the d-axis current I d The second voltage-limited q-axis current I qv2 Extend between.

[0055] Figure 5AIt is shown that both plot lines 400, 402 are plotted for all d-axis currents I d The values ​​all have positive q-axis current I q The first plotted line 400 always has a corresponding q-axis current I smaller than the second plotted line 402. q The value of the q-axis current I q Therefore, in this case, the torque limit arbitration block 308 can set the final torque limit T pk Set equal to the current based torque limit

[0056] Figure 5B A first plot line 404 is included which shows the calculated current limit to meet the motor current limit. The d-axis current I d and q-axis current I q The first plotted line 404 is in the d-axis current I d The first q-axis current I based on the motor current equals to the predetermined minimum value qi1 With the d-axis current I d The second q-axis current I based on the motor current is equal to the predetermined maximum value. qi2 Extend between. Figure 5B Also included is a second plot line 406 which shows the calculated voltage V that satisfies the DC bus 215. DC The d-axis current I d and q-axis current I q The second plot line 406 is plotted on the d-axis current I d The first voltage-limited q-axis current I qv1 With the d-axis current I d The second voltage-limited q-axis current I qv2 Extend between.

[0057] Figure 5B It is shown that both plot lines 404, 406 are plotted for all d-axis currents I d The values ​​all have positive q-axis current I q The second plot line 406 always has a corresponding q-axis current I smaller than the first plot line 404. q The value of the q-axis current I q Therefore, in this case, the torque limit arbitration block 308 can set the final torque limit T pk Set equal to the voltage based torque limit

[0058] Figure 5C A first plot line 408 is included which shows the calculated current limit to meet the motor current limit. The d-axis current I d and q-axis current I q The first plot line 408 is the d-axis current I d The first q-axis current I based on the motor current equals to the predetermined minimum value qi1 With the d-axis current I d The second q-axis current I based on the motor current is equal to the predetermined maximum value. qi2 Extend between. Figure 5C Also included is a second plot line 410 that shows the calculated voltage V that satisfies the DC bus 215. DC The d-axis current I d and q-axis current I q The second plot line 410 is the d-axis current I d The first voltage-limited q-axis current I qv1 With the d-axis current I d The second voltage-limited q-axis current I qv2 Extend between.

[0059] Figure 5C The depiction lines 408, 410 are shown in the region (I d ,I q Therefore, when the current-based curve and the voltage-based curve intersect, the final torque limit T pk The determination should be based on the intersection of the curves represented by the plotted lines 408, 410. For example, the controller 16 may determine that the current limit corresponding to the motor current is The q-axis current is equal to the voltage constraint V corresponding to the DC bus 215 DC In the case of a q-axis current of (i.e., in the case where the plotted lines 408 and 410 intersect), the d-axis intersection current value I d_int The controller 16 can be based on the d-axis intersection current value I d_int To determine the final torque limit T pk For example, the controller 16 may determine the corresponding q-axis intersection current value I that satisfies the following two equations: q_int : used to meet the voltage constraint V of the DC bus 215 DC The voltage equation and the current limit for the motor The voltage equation may include the above equation (3); and the current equation may include the above equation (4). The corresponding q-axis intersection current value I q_int exist Figure 5C The controller 16 can then determine the d-axis intersection current value I based on the d-axis intersection current value I d_int The current value I intersecting the q axis q_intTo determine the final torque limit T pk For example, the controller 16 can calculate the d-axis intersection current value I d_int The current value I intersecting the q axis q_int Substituting into the torque equation for calculating torque based on the d-axis current and the q-axis current to calculate the final torque limit T pk The torque equation may include equation (5) above.

[0060] Figure 5D A first plot line 412 is included, which shows the calculated current limit I ilim The d-axis current I d and q-axis current I q The first plotted line 412 is the d-axis current I d The first q-axis current I based on the motor current equals to the predetermined minimum value qi1 With the d-axis current I d The second negative q-axis current (not shown) based on the motor current extends between 0 and 100° and is equal to the predetermined maximum value. Figure 5D Also included is a second plot line 414 which shows the calculated voltage V of the DC bus 215 that satisfies the voltage constraint V DC The d-axis current I d and q-axis current I q The second plot line 414 is the d-axis current I d The first voltage-limited q-axis current equal to the predetermined minimum value and the d-axis current I d The second voltage-limited q-axis current I qv2 The first voltage-limited q-axis current has a negative value and is not shown in the figure.

[0061] Figure 5D It is shown that for any d-axis current I d There is no q-axis current I less than or equal to each of the plot lines 412 and 414. q The value of the q-axis current I q Therefore, in this case, the torque limit arbitration block 308 can set the final torque limit T pk In other words, in the absence of a direct relationship between the two curves represented by the plotted lines 412 , 414 , the final torque limit T pk Can be set to zero.

[0062] Figure 65 is a flow chart generally illustrating a method 500 for controlling the operation of an electric machine. At 502, the method 500 calculates a voltage-based torque limit based on a voltage constraint of a direct current (DC) bus that supplies power to an inverter to power the electric machine. For example, the processor 102 may execute instructions implementing the voltage limit block 306 to calculate a voltage-based torque limit based on a voltage constraint V of the DC bus 215. DC To calculate the torque limit based on voltage

[0063] At 504, method 500 calculates a current-based torque limit based on the motor current limit. For example, processor 102 may execute a method to implement a torque limit based on the motor current limit. Determining the torque limit based on current The inverter / motor current limit block 304 is instructing.

[0064] At 506 , method 500 determines the final torque limit T based on pk : Torque limitation based on voltage and current-based torque limiting In some embodiments, the final torque limit T is determined pk Included in the voltage based torque limit and current-based torque limiting For example, the processor 102 may execute instructions implementing the torque limit arbitration block 308 to determine the final torque limit T based on the following items: pk : Torque limitation based on voltage and current-based torque limiting They are based on the current limit of the motor 19 and the inverter combination. and the voltage constraint V of the DC bus 215 DC The current limit of the motor 19 and inverter combination Also called motor current limiting

[0065] In some embodiments, the voltage-based torque limit and current-based torque limiting The arbitration includes: determining a first q-axis current I based on the motor current qi1 , which corresponds to a d-axis current I having a predetermined minimum value (eg, zero) d And corresponds to the motor current limit In voltage based torque limiting and current-based torque limiting The arbitration between the two can also include: determining a second q-axis current I based on the motor current qi2 , which corresponds to a d-axis current I having a predetermined maximum valued And corresponds to the motor current limit In voltage based torque limiting and current-based torque limiting The arbitration between the two can also include: determining the first voltage-limited q-axis current I qv1 , which corresponds to a d-axis current I having a predetermined minimum value d and corresponds to the voltage constraint V of the DC bus 215 DC . In voltage-based torque limiting and current-based torque limiting The arbitration between the two can also include: determining a second voltage-limited q-axis current I qv2 , which corresponds to a d-axis current I having a predetermined maximum value d and corresponds to the voltage constraint V of the DC bus 215 DC .

[0066] In voltage based torque limiting and current-based torque limiting The arbitration between the two may also include: determining a first q-axis current I based on the motor current qi1 and the first voltage-limited q-axis current I qv1 As a smaller value of one; and determine the second motor current based on the q-axis current I qi2 and the second voltage-limited q-axis current I qv2 The smaller value is used in the torque limit based on voltage. and current-based torque limiting The arbitration may also include: based on the first q-axis current I based on the motor current qi1 and the first voltage-limited q-axis current I qv1 The smaller value of the q-axis current I in the second motor current is based on the q-axis current I qi2 and the second voltage-limited q-axis current I qv2 The torque limit based on the current is selected as a smaller value and voltage-based torque limiting one of the.

[0067] In some embodiments, a current-based torque limit is selected. and voltage-based torque limiting One of the steps further includes: in response to determining a first q-axis current I based on the motor current qi1 is less than the first voltage-limited q-axis current I qv1 and a second q-axis current I based on the motor current qi2 Less than the second voltage-limited q-axis current Iqv2 Select current-based torque limit As the final torque limit T pk An example of this is in Figure 5A Shown in.

[0068] In some embodiments, a current-based torque limit is selected. and voltage-based torque limiting One of the embodiments further includes: in response to determining the first voltage-limited q-axis current I qv1 is less than the first q-axis current I based on the motor current qi1 and the second voltage-limited q-axis current I qv2 Less than the second q-axis current I based on the motor current qi2 , select voltage-based torque limit As the final torque limit T pk An example of this is in Figure 5B Shown in.

[0069] In some embodiments, the voltage-based torque limit and current-based torque limiting The arbitration between the two may also include: determining a first q-axis current I based on the motor current qi1 , which corresponds to a d-axis current I having a predetermined minimum value (eg, zero) d And corresponds to the motor current limit In voltage based torque limiting and current-based torque limiting The arbitration between the two may also include: determining a second q-axis current I based on the motor current qi2 , which corresponds to a d-axis current I having a predetermined maximum value d And corresponds to the motor current limit In voltage based torque limiting and current-based torque limiting The arbitration between the two may also include: determining a first voltage-limited q-axis current I qv1 , which corresponds to a d-axis current I having a predetermined minimum value d and corresponds to the voltage constraint V of the DC bus 215 DC . In voltage-based torque limiting and current-based torque limiting The arbitration between the two may also include: determining a second voltage-limited q-axis current I qv2 , which corresponds to a d-axis current I having a predetermined maximum value d and corresponds to the voltage constraint V of the DC bus 215 DC .

[0070] In voltage based torque limiting and current-based torque limiting The arbitration between the two may also include: determining a first q-axis current I based on the motor current qi1 and the first voltage-limited q-axis current I qv1 As a smaller value of one; and determine the second motor current based on the q-axis current I qi2 and the second voltage-limited q-axis current I qv2 The smaller value is used in the torque limit based on voltage. and current-based torque limiting The arbitration between the two may also include: determining a second q-axis current I based on the motor current qi2 and the second voltage-limited q-axis current I qv2 The smaller value of the first q-axis current I based on the motor current qi1 and the first voltage-limited q-axis current I qv1 The smaller value of corresponds to a different constraint. An example of this is Figure 5C , where the second voltage-limited q-axis current I qv2 (which is consistent with the voltage constraint V of the DC bus 215 DC associated) has a q-axis current I based on the second motor current qi2 The first q-axis current I based on the motor current is qi1 (It is related to the motor current limit associated) has a q-axis current I greater than the first voltage-based limit qv1 Small values. If the endpoints are swapped, similar results can be produced, including intersecting trace lines.

[0071] In some embodiments, the method 500 may further include: determining the d-axis intersection current value I d_int , at which the d-axis intersects the current value I d_int At, corresponding to the motor current limit The q-axis current is equal to the voltage constraint V corresponding to the DC bus 215 DC The q-axis current.

[0072] In some embodiments, the method 500 may further include: based on the d-axis intersection current value I d_int and based on the motor current limit corresponding to and the voltage constraint V of the DC bus 215 DC The q-axis current I of each q To determine the final torque limit T pk For example, the controller 16 may determine the corresponding q-axis intersection current value I that satisfies the following two equations:q_int : used to meet the voltage constraint V of the DC bus 215 DC The voltage equation and the current limit for the motor The voltage equation may include equation (3) above; and the current equation may include equation (4) above. The controller 16 may then calculate the current value I based on the d-axis intersection current value I d_int The current value I intersecting the q axis q_int To determine the final torque limit T pk For example, the controller 16 can calculate the d-axis intersection current value I d_int The current value I intersecting the q axis q_int Substituting into the torque equation for calculating torque based on the d-axis current and the q-axis current to calculate the final torque limit T pk The torque equation may include equation (5) above.

[0073] At 508, method 500 determines a limited command torque based on the torque command and the final torque limit. For example, processor 102 may execute instructions implementing torque command limit block 310 to limit the torque based on the commanded torque T c and final torque limit T pk Determine the limited command torque T CmdLmtd More specifically, the torque command limiting block 310 can limit the command torque T CmdLmtd Set to be limited not to exceed the final torque limit T pk The command torque T c .

[0074] At 510, method 500 generates at least one current command based at least on the limited command torque. For example, processor 102 may execute instructions implementing current command calculation block 320 to determine a d-axis current command and a q-axis current command I for controlling operation of inverter 216. * dq More specifically, the current command calculation block 320 may be based on the limited command torque T CmdLmtd , the d-axis current command and the q-axis current command I are calculated using the maximum torque per ampere determination result for optimizing the current command for torque production and / or the maximum torque per voltage determination result for optimizing the current command for the voltage to be applied to the motor 19. * dq .

[0075] In some embodiments, generating at least one current command includes determining at least one preliminary motor current value This will cause the motor 19 to use the least amount of current to produce the limited command torque T CmdLmtd This determination may be performed by the maximum torque per ampere block 322 .

[0076] In some embodiments, generating at least one current command includes: based on at least one preliminary motor current value Determine at least one current command, the preliminary motor current value Corresponding to the supply voltage of the DC bus 215 and the voltage constraint V of the DC bus 215 DC , and will cause the motor 19 to generate a limited command torque T CmdLmtd This determination may be performed by the maximum torque per voltage block 324 .

[0077] According to one aspect of the present disclosure, a method for controlling operation of an electric machine is provided. The method includes: calculating a voltage-based torque limit based on a voltage constraint of a direct current (DC) bus that supplies power to an inverter to power the electric machine; calculating a current-based torque limit based on a motor current limit; determining a final torque limit based on: a voltage-based torque limit and a current-based torque limit; determining a limited command torque based on a torque command and the final torque limit; and generating at least one current command based on at least the limited command torque.

[0078] According to one aspect of the present disclosure, the method of controlling the operation of the motor may further include: selectively controlling a plurality of switches within the inverter based on at least one current command to cause the inverter to supply current to the motor.

[0079] According to one aspect of the present disclosure, the motor current limit may be the smaller one of the current limit of the inverter and the current limit of the motor.

[0080] According to one aspect of the present disclosure, determining the final torque limit may further include arbitrating between a voltage-based torque limit and a current-based torque limit.

[0081] According to one aspect of the present disclosure, arbitrating between a voltage-based torque limit and a current-based torque limit may further include: determining a first motor-current-based q-axis current corresponding to a d-axis current having a predetermined minimum value and corresponding to a motor current limit; determining a second motor-current-based q-axis current corresponding to a d-axis current having a predetermined maximum value and corresponding to a motor current limit; determining a first voltage-limited q-axis current corresponding to a d-axis current having a predetermined minimum value and corresponding to a voltage constraint of a DC bus; determining a second voltage-limited q-axis current corresponding to a d-axis current having a predetermined maximum value and corresponding to a voltage constraint of a DC bus; determining one of the first motor-current-based q-axis current and the first voltage-limited q-axis current as a smaller value; determining one of the second motor-current-based q-axis current and the second voltage-limited q-axis current as a smaller value; and selecting one of the current-based torque limit and the voltage-based torque limit based on one of the first motor-current-based q-axis current and the first voltage-limited q-axis current as a smaller value and based on one of the second motor-current-based q-axis current and the second voltage-limited q-axis current as a smaller value.

[0082] According to one aspect of the present disclosure, selecting one of a current-based torque limit and a voltage-based torque limit may also include: selecting the current-based torque limit as the final torque limit in response to determining that a first motor-current-based q-axis current is less than a first voltage-limited q-axis current and a second motor-current-based q-axis current is less than a second voltage-limited q-axis current; and selecting the voltage-based torque limit as the final torque limit in response to determining that the first voltage-limited q-axis current is less than the first motor-current-based q-axis current and the second voltage-limited q-axis current is less than the second motor-current-based q-axis current.

[0083] According to one aspect of the present disclosure, arbitrating between a voltage-based torque limit and a current-based torque limit may further include: determining a first motor current-based q-axis current, which corresponds to a d-axis current having a predetermined minimum value and corresponds to a motor current limit; determining a second motor current-based q-axis current, which corresponds to a d-axis current having a predetermined maximum value and corresponds to a motor current limit; determining a first voltage-limited q-axis current, which corresponds to a d-axis current having a predetermined minimum value and corresponds to a voltage constraint of a DC bus; determining a second voltage-limited q-axis current, which corresponds to a d-axis current having a predetermined maximum value and corresponds to a voltage constraint of a DC bus; determining a first motor current-based ... second motor current-based q-axis current, which corresponds to a d-axis current having a predetermined maximum value and corresponds to a voltage constraint of a DC bus; determining a first motor current-based determining a second motor current-based q-axis current and a first voltage-limited q-axis current as a smaller value; determining a second motor current-based q-axis current and a second voltage-limited q-axis current as a smaller value; determining that the second motor current-based q-axis current and the second voltage-limited q-axis current as a smaller value correspond to different constraints than the first motor current-based q-axis current and the first voltage-limited q-axis current as a smaller value; determining a d-axis intersection current value at which the q-axis current corresponding to the motor current limit is equal to the q-axis current corresponding to the voltage constraint of the DC bus; and determining a final torque limit based on the d-axis intersection current value.

[0084] According to an aspect of the present disclosure, generating at least one current command may further include: determining at least one current command based on at least one preliminary motor current value, which preliminary motor current value corresponds to a supply voltage of the DC bus and a voltage constraint of the DC bus and will cause the motor to produce a limited command torque.

[0085] According to one aspect of the present disclosure, a control system for controlling operation of an electric machine includes a processor and a memory. The memory includes instructions that, when executed by the processor, cause the processor to: calculate a voltage-based torque limit based on a voltage constraint of a direct current (DC) bus that supplies power to an inverter to power the electric machine; calculate a current-based torque limit based on a motor current limit; determine a final torque limit based on: a voltage-based torque limit and a current-based torque limit; determine a limited command torque based on a torque command and the final torque limit; and generate at least one current command based on at least the limited command torque.

[0086] According to one aspect of the present disclosure, the instructions may further cause the processor to selectively control a plurality of switches within the inverter based on the at least one current command so that the inverter supplies current to the motor.

[0087] According to one aspect of the present disclosure, the motor current limit may be the smaller one of the current limit of the inverter and the current limit of the motor.

[0088] According to one aspect of the present disclosure, determining the final torque limit may further include arbitrating between a voltage-based torque limit and a current-based torque limit.

[0089] According to one aspect of the present disclosure, arbitrating between a voltage-based torque limit and a current-based torque limit may further include instructions for causing a processor to: determine a first motor-current-based q-axis current corresponding to a d-axis current having a predetermined minimum value and corresponding to a motor current limit; determine a second motor-current-based q-axis current corresponding to a d-axis current having a predetermined maximum value and corresponding to a motor current limit; determine a first voltage-limit-based q-axis current corresponding to a d-axis current having a predetermined minimum value and corresponding to a voltage constraint of a DC bus; determine a second voltage-limit-based q-axis current corresponding to a d-axis current having a predetermined maximum value and corresponding to a voltage constraint of a DC bus; determine one of the first motor-current-based q-axis current and the first voltage-limit-based q-axis current as a smaller value; determine one of the second motor-current-based q-axis current and the second voltage-limit-based q-axis current as a smaller value; and select one of the current-based torque limit and the voltage-based torque limit based on one of the first motor-current-based q-axis current and the first voltage-limit-based q-axis current as a smaller value and based on one of the second motor-current-based q-axis current and the second voltage-limit-based q-axis current as a smaller value.

[0090] According to one aspect of the present disclosure, selecting one of a current-based torque limit and a voltage-based torque limit may also include instructions causing the processor to: select the current-based torque limit as the final torque limit in response to determining that a first motor-current-based q-axis current is less than a first voltage-limited q-axis current and a second motor-current-based q-axis current is less than a second voltage-limited q-axis current; and select the voltage-based torque limit as the final torque limit in response to determining that the first voltage-limited q-axis current is less than the first motor-current-based q-axis current and the second voltage-limited q-axis current is less than the second motor-current-based q-axis current.

[0091] According to one aspect of the present disclosure, arbitrating between a voltage-based torque limit and a current-based torque limit may further include instructions for causing a processor to: determine a first motor current-based q-axis current, which corresponds to a d-axis current having a predetermined minimum value and corresponds to a motor current limit; determine a second motor current-based q-axis current, which corresponds to a d-axis current having a predetermined maximum value and corresponds to a motor current limit; determine a first voltage-limited q-axis current, which corresponds to a d-axis current having a predetermined minimum value and corresponds to a voltage constraint of a DC bus; determine a second voltage-limited q-axis current, which corresponds to a d-axis current having a predetermined maximum value and corresponds to a voltage constraint of a DC bus; determine the first motor current-based q-axis current and the first ... determining one of the second motor-current-based q-axis current and the second voltage-limit-based q-axis current as a smaller value; determining one of the second motor-current-based q-axis current and the second voltage-limit-based q-axis current as a smaller value to correspond to a different constraint than the first motor-current-based q-axis current and the first voltage-limit-based q-axis current as a smaller value; determining a d-axis intersection current value at which the q-axis current corresponding to the motor current limit is equal to the q-axis current corresponding to the voltage constraint of the DC bus; and determining a final torque limit based on the d-axis intersection current value and based on the q-axis current corresponding to each of the motor current limit and the voltage constraint of the DC bus.

[0092] According to one aspect of the present disclosure, generating at least one current command may further include: determining at least one current command based on at least one preliminary motor current value, which preliminary motor current value corresponds to a supply voltage of the DC bus and a voltage constraint of the DC bus and will cause the motor to produce a limited command torque.

[0093] According to one aspect of the present disclosure, a control system for controlling the operation of an electric motor includes an inverter having a plurality of switches operable to supply alternating current to the electric motor. The control system also includes a controller operable to: calculate a voltage-based torque limit based on a voltage constraint of a direct current (DC) bus supplying power to the inverter to power the electric motor; calculate a current-based torque limit based on a motor current limit; determine a final torque limit based on: a voltage-based torque limit and a current-based torque limit; determine a limited command torque based on a torque command and a final torque limit; generate at least one current command based at least on the limited command torque; and selectively control the plurality of switches within the inverter based on at least one current command so that the inverter supplies alternating current to the electric motor.

[0094] According to one aspect of the present disclosure, determining the final torque limit may further include arbitrating between a voltage-based torque limit and a current-based torque limit.

[0095] According to one aspect of the present disclosure, arbitrating between a voltage-based torque limit and a current-based torque limit may further include the controller being operable to: determine a first motor-current-based q-axis current corresponding to a d-axis current having a predetermined minimum value and corresponding to a motor current limit; determine a second motor-current-based q-axis current corresponding to a d-axis current having a predetermined maximum value and corresponding to a motor current limit; determine a first voltage-limit-based q-axis current corresponding to a d-axis current having a predetermined minimum value and corresponding to a voltage constraint of a DC bus; determine a second voltage-limit-based q-axis current corresponding to a d-axis current having a predetermined maximum value and corresponding to a voltage constraint of a DC bus; determine one of the first motor-current-based q-axis current and the first voltage-limit-based q-axis current as a smaller value; determine one of the second motor-current-based q-axis current and the second voltage-limit-based q-axis current as a smaller value; and select one of the current-based torque limit and the voltage-based torque limit based on one of the first motor-current-based q-axis current and the first voltage-limit-based q-axis current as a smaller value and based on one of the second motor-current-based q-axis current and the second voltage-limit-based q-axis current as a smaller value.

[0096] According to one aspect of the present disclosure, selecting one of a current-based torque limit and a voltage-based torque limit may further include the controller being operable to: select the current-based torque limit as the final torque limit in response to determining that a first motor-current-based q-axis current is less than a first voltage-limited q-axis current and a second motor-current-based q-axis current is less than a second voltage-limited q-axis current, and select the voltage-based torque limit as the final torque limit in response to determining that the first voltage-limited q-axis current is less than the first motor-current-based q-axis current and the second voltage-limited q-axis current is less than the second motor-current-based q-axis current.

[0097] The above discussion is intended to illustrate the principles and various embodiments of the present disclosure. Once the above disclosure is fully understood, many changes and modifications will become apparent to those skilled in the art. It is intended that the following claims be interpreted to include all such changes and modifications.

[0098] The word "example" is used herein to mean used as an example, instance or illustration. Any aspect or design described herein as an "example" is not necessarily to be interpreted as being more preferred or advantageous than other aspects or designs. On the contrary, the use of the word "example" is intended to present the concept in a specific way. As used in this application, the term "or" is intended to represent an inclusive "or" rather than an exclusive "or". That is, unless otherwise specified or clearly seen from the context, "X includes A or B" is intended to represent any natural inclusive arrangement. That is, if X includes A; X includes B; or X includes both A and B, then "X includes A or B" is satisfied in any of the foregoing cases. In addition, the article "a / an" used in this application and the appended claims should generally be interpreted as meaning "one or more", unless otherwise specified or clearly pointed to the singular form from the context. In addition, unless so described, the use of the term "embodiment" or "one embodiment" throughout the text is not intended to represent the same embodiment or embodiment.

[0099] The implementation of the systems, algorithms, methods, instructions, etc. described herein may be implemented in hardware, software, or any combination thereof. The hardware may include, for example, a computer, an intellectual property (IP) core, an application specific integrated circuit (ASIC), a programmable logic array, an optical processor, a programmable logic controller, microcode, a microcontroller, a server, a microprocessor, a digital signal processor, or any other suitable circuit. In the claims, the term "processor" shall be understood to include any of the foregoing hardware, alone or in combination. The terms "signal" and "data" are used interchangeably.

[0100] As used herein, the term module may include a packaged functional hardware unit designed for use with other components, a set of instructions executable by a controller (e.g., a processor executing software or firmware), a processing circuit configured to perform a specific function, and a self-contained hardware or software component that interfaces with a larger system. For example, a module may include an application specific integrated circuit (ASIC), a field programmable gate array (FPGA), an electrical circuit, a digital logic circuit, an analog circuit, a combination of discrete circuits, gate circuits, and other types of hardware, or a combination thereof. In other embodiments, a module may include a memory that stores instructions executable by a controller to implement the features of the module.

[0101] Furthermore, in one aspect, for example, the systems described herein may be implemented using a general purpose computer or general purpose processor with a computer program that, when executed, performs any corresponding method, algorithm, and / or instruction described herein. Additionally or alternatively, for example, a special purpose computer / processor may be utilized that may include other hardware for performing any method, algorithm, or instruction described herein.

[0102] In addition, all or part of the implementation of the present disclosure may take the form of a computer program product accessible from, for example, a computer usable or computer readable medium. A computer usable or computer readable medium may be, for example, any device that can tangibly contain, store, communicate, or transport a program for use by or in conjunction with any processor. The medium may be, for example, an electronic, magnetic, optical, electromagnetic device, or a semiconductor device. Other suitable media may also be used.

[0103] The above embodiments, implementations and aspects have been described to allow easy understanding of the present disclosure and are not intended to limit the present disclosure. On the contrary, the present disclosure is intended to cover various modifications and equivalent arrangements included within the scope of the appended claims, which scope should be given the broadest interpretation to cover all such modifications and equivalent structures permitted by law.

Claims

1. A method of controlling the operation of a motor, comprising: calculating a voltage-based torque limit based on a voltage constraint of a direct current (DC) bus supplying power to an inverter for powering the motor; calculating a current-based torque limit based on the motor current limit; determining a final torque limit based on: the voltage-based torque limit and the current-based torque limit; determining a limited command torque based on the torque command and the final torque limit; as well as At least one current command is generated based at least on the limited commanded torque.

2. The method according to claim 1, further comprising: A plurality of switches within the inverter are selectively controlled based on the at least one current command to cause the inverter to supply current to the motor.

3. The method according to claim 1, wherein: The motor current limit is the lesser of a current limit of the inverter and a current limit of the electric machine.

4. The method according to claim 1, wherein: Determining the final torque limit further includes arbitrating between the voltage-based torque limit and the current-based torque limit.

5. The method according to claim 4, wherein: Arbitrating between the voltage-based torque limit and the current-based torque limit further includes: determining a first motor-current-based q-axis current corresponding to the d-axis current having a predetermined minimum value and corresponding to the motor current limit; determining a second motor-current-based q-axis current corresponding to the d-axis current having a predetermined maximum value and corresponding to the motor current limit; determining a first voltage-limited based q-axis current corresponding to a d-axis current having a predetermined minimum value and corresponding to a voltage constraint of the DC bus; determining a second voltage-limited based q-axis current corresponding to the d-axis current having a predetermined maximum value and corresponding to a voltage constraint of the DC bus; determining one of the first motor current-based q-axis current and the first voltage limit-based q-axis current as a smaller value; determining one of the second motor current-based q-axis current and the second voltage limit-based q-axis current as a smaller value; and One of the current-based torque limit and the voltage-based torque limit is selected based on the smaller one of the first motor-current-based q-axis current and the first voltage-limit-based q-axis current and based on the smaller one of the second motor-current-based q-axis current and the second voltage-limit-based q-axis current.

6. The method according to claim 5, wherein: Selecting one of the current-based torque limit and the voltage-based torque limit further comprises: selecting the current-based torque limit as the final torque limit in response to determining that the first motor-current-based q-axis current is less than the first voltage-limit-based q-axis current and the second motor-current-based q-axis current is less than the second voltage-limit-based q-axis current; and In response to determining that the first voltage-limited q-axis current is less than the first motor-current-based q-axis current and the second voltage-limited q-axis current is less than the second motor-current-based q-axis current, the voltage-based torque limit is selected as the final torque limit.

7. The method according to claim 4, wherein: Arbitrating between the voltage-based torque limit and the current-based torque limit further includes: determining a first motor-current-based q-axis current corresponding to the d-axis current having a predetermined minimum value and corresponding to the motor current limit; determining a second motor-current-based q-axis current corresponding to the d-axis current having a predetermined maximum value and corresponding to the motor current limit; determining a first voltage-limited based q-axis current corresponding to a d-axis current having a predetermined minimum value and corresponding to a voltage constraint of the DC bus; determining a second voltage-limited based q-axis current corresponding to the d-axis current having a predetermined maximum value and corresponding to a voltage constraint of the DC bus; determining one of the first motor current-based q-axis current and the first voltage limit-based q-axis current as a smaller value; determining one of the second motor current-based q-axis current and the second voltage limit-based q-axis current as a smaller value; determining that the smaller one of the second motor current-based q-axis current and the second voltage limit-based q-axis current corresponds to a different constraint than the smaller one of the first motor current-based q-axis current and the first voltage limit-based q-axis current; determining a d-axis intersection current value at which a q-axis current corresponding to the motor current limit is equal to a q-axis current corresponding to a voltage constraint of the DC bus; and The final torque limit is determined based on the d-axis intersecting current value and based on a q-axis current corresponding to each of a motor current limit and a voltage constraint of a DC bus.

8. The method according to claim 1, wherein: Generating the at least one current command further includes determining the at least one current command based on at least one preliminary motor current value that corresponds to a supply voltage of the DC bus and a voltage constraint of the DC bus and that will cause the electric machine to produce the limited commanded torque.

9. A control system for controlling the operation of a motor, comprising: processor; as well as a memory comprising instructions which, when executed by the processor, cause the processor to: calculating a voltage-based torque limit based on a voltage constraint of a direct current (DC) bus supplying power to an inverter for powering the motor; calculating a current-based torque limit based on the motor current limit; determining a final torque limit based on: the voltage-based torque limit and the current-based torque limit; determining a limited command torque based on the torque command and the final torque limit; as well as At least one current command is generated based at least on the limited commanded torque.

10. The control system according to claim 9, wherein: The instructions further cause the processor to selectively control a plurality of switches within the inverter based on the at least one current command to cause the inverter to supply current to the motor.

11. The control system according to claim 9, wherein: The motor current limit is the lesser of a current limit of the inverter and a current limit of the electric machine.

12. The control system according to claim 9, wherein: Determining a final torque limit further includes arbitrating between the voltage-based torque limit and the current-based torque limit.

13. The control system according to claim 12, wherein: Arbitrating between the voltage-based torque limit and the current-based torque limit further comprises the instructions causing the processor to: determining a first motor-current-based q-axis current corresponding to the d-axis current having a predetermined minimum value and corresponding to the motor current limit; determining a second motor-current-based q-axis current corresponding to the d-axis current having a predetermined maximum value and corresponding to the motor current limit; determining a first voltage-limited based q-axis current corresponding to a d-axis current having a predetermined minimum value and corresponding to a voltage constraint of the DC bus; determining a second voltage-limited based q-axis current corresponding to the d-axis current having a predetermined maximum value and corresponding to a voltage constraint of the DC bus; determining one of the first motor current-based q-axis current and the first voltage limit-based q-axis current as a smaller value; determining one of the second motor current-based q-axis current and the second voltage limit-based q-axis current as a smaller value; as well as One of the current-based torque limit and the voltage-based torque limit is selected based on the smaller one of the first motor-current-based q-axis current and the first voltage-limit-based q-axis current and based on the smaller one of the second motor-current-based q-axis current and the second voltage-limit-based q-axis current.

14. The control system according to claim 13, wherein: Selecting one of the current-based torque limit and the voltage-based torque limit further comprises the instructions causing the processor to: selecting the current-based torque limit as the final torque limit in response to determining that the first motor-current-based q-axis current is less than the first voltage-limit-based q-axis current and the second motor-current-based q-axis current is less than the second voltage-limit-based q-axis current; as well as In response to determining that the first voltage-limited q-axis current is less than the first motor-current-based q-axis current and the second voltage-limited q-axis current is less than the second motor-current-based q-axis current, the voltage-based torque limit is selected as the final torque limit.

15. The control system according to claim 12, wherein: Arbitrating between the voltage-based torque limit and the current-based torque limit further comprises the instructions causing the processor to: determining a first motor-current-based q-axis current corresponding to the d-axis current having a predetermined minimum value and corresponding to the motor current limit; determining a second motor-current-based q-axis current corresponding to the d-axis current having a predetermined maximum value and corresponding to the motor current limit; determining a first voltage-limited based q-axis current corresponding to a d-axis current having a predetermined minimum value and corresponding to a voltage constraint of the DC bus; determining a second voltage-limited based q-axis current corresponding to the d-axis current having a predetermined maximum value and corresponding to a voltage constraint of the DC bus; determining one of the first motor current-based q-axis current and the first voltage limit-based q-axis current as a smaller value; determining one of the second motor current-based q-axis current and the second voltage limit-based q-axis current as a smaller value; determining that the smaller one of the second motor current-based q-axis current and the second voltage limit-based q-axis current corresponds to a different constraint than the smaller one of the first motor current-based q-axis current and the first voltage limit-based q-axis current; determining a d-axis intersection current value at which a q-axis current corresponding to the motor current limit is equal to a q-axis current corresponding to a voltage constraint of the DC bus; as well as The final torque limit is determined based on the d-axis intersecting current value and based on a q-axis current corresponding to each of a motor current limit and a voltage constraint of a DC bus.

16. The control system according to claim 9, wherein: Generating the at least one current command further includes determining the at least one current command based on at least one preliminary motor current value that corresponds to a supply voltage of the DC bus and a voltage constraint of the DC bus and that will cause the electric machine to produce the limited commanded torque.

17. A control system for controlling the operation of an electric motor, comprising: an inverter including a plurality of switches operable to supply alternating current to the motor; as well as A controller operable to: calculating a voltage-based torque limit based on a voltage constraint of a direct current (DC) bus supplying power to an inverter for powering the motor; calculating a current-based torque limit based on the motor current limit; determining a final torque limit based on: the voltage-based torque limit and the current-based torque limit; determining a limited command torque based on the torque command and the final torque limit; generating at least one current command based at least on the limited commanded torque; as well as The plurality of switches within the inverter are selectively controlled based on the at least one current command to cause the inverter to supply alternating current to the motor.

18. The control system according to claim 17, wherein: Determining the final torque limit includes arbitrating between the voltage-based torque limit and the current-based torque limit.

19. The control system of claim 18, arbitrating between the voltage-based torque limit and the current-based torque limit further comprising the controller being operative to: determining a first motor-current-based q-axis current corresponding to the d-axis current having a predetermined minimum value and corresponding to the motor current limit; determining a second motor-current-based q-axis current corresponding to the d-axis current having a predetermined maximum value and corresponding to the motor current limit; determining a first voltage-limited based q-axis current corresponding to a d-axis current having a predetermined minimum value and corresponding to a voltage constraint of the DC bus; determining a second voltage-limited based q-axis current corresponding to the d-axis current having a predetermined maximum value and corresponding to a voltage constraint of the DC bus; determining one of the first motor current-based q-axis current and the first voltage limit-based q-axis current as a smaller value; determining one of the second motor current-based q-axis current and the second voltage limit-based q-axis current as a smaller value; as well as One of the current-based torque limit and the voltage-based torque limit is selected based on the smaller one of the first motor-current-based q-axis current and the first voltage-limit-based q-axis current and based on the smaller one of the second motor-current-based q-axis current and the second voltage-limit-based q-axis current.

20. The control system of claim 19, wherein: Selecting one of the current-based torque limit and the voltage-based torque limit further includes the controller being operative to: selecting the current-based torque limit as the final torque limit in response to determining that the first motor-current-based q-axis current is less than the first voltage-limit-based q-axis current and the second motor-current-based q-axis current is less than the second voltage-limit-based q-axis current; as well as In response to determining that the first voltage-limited q-axis current is less than the first motor-current-based q-axis current and the second voltage-limited q-axis current is less than the second motor-current-based q-axis current, the voltage-based torque limit is selected as the final torque limit.

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