Patent Description:
In some prior art, an inverter and electric machine are tested or commissioned as a matched pair in a lab prior to installation into equipment. During the lab testing, the electric machine is characterized by generating one or more corresponding look-up tables associated with the electric machine to control properly the electric machine in compatible manner. First, the lab testing introduces possible additional labor costs into the combination of the inverter and electric machine. Second, the lab testing may limit the available electric machines, or the universe of compatible electric machines, for a corresponding inverter only to those pairs of inverters and electric machines that have been tested and characterized. According, there is a need for an inverter for controlling an electric machine without prior characterization.

<CIT> describes a device for estimating inductances of an electric machine having a salient-pole rotor. The device comprises a processing system that controls stator voltages to constitute a balanced multi-phase alternating voltage when the rotor is stationary. The processing system estimates a position of the rotor based on a negative sequence component of stator currents. To estimate the quadrature-axis inductance, the processing system controls direct-axis current to be direct current and quadrature-axis voltage to be alternating voltage. The quadrature-axis inductance is estimated based on the quadrature-axis alternating voltage and on quadrature-axis alternating current. To estimate the direct-axis inductance, the processing system controls direct-axis voltage to be alternating voltage and the quadrature-axis voltage to be zero. The direct-axis inductance is estimated based on the direct-axis alternating voltage and on direct-axis alternating current.

"<NPL>, describes a novel sensorless control algorithm for <NUM>-Phase BLDC motors with trapezoidal back-EMF. The proposed algorithms include both the new back-EMF estimation method by using the DC current model and a compensator for the electric parameter errors of the BLDC motor to improve performance of sensorless control more exactly. The back-EMF can be easily calculated from the electrical voltage equation. However, it has some errors at the commutation period. This error can be reduced by using the proposed sensorless control algorithm which is derived by using the mechanical and electrical equation simultaneously for the accurate estimation of the back-EMF. In this case, the back-EMF estimation is affected by the electric parameters. If the motor parameters have errors, there will be some errors of the estimated back-EMF. Therefore, a new algorithm is needed for parameter error compensation. Among the motor parameters, stator resistor and back-EMF constant are mainly affected by the temperature. Therefore, this paper proposes the new sensorless control algorithm with the real time compensation of the motor parameter variation according to temperature. The main attractive features of the proposed algorithm have the robustness to the parameter variation and the transient state, and the less torque ripple by using the DC-current model. The usefulness of the proposed sensorless control method is verified through the simulation.

"<NPL>, describes the maximum torque and speed of permanent-magnet synchronous motor (PMSM) drives when the inverter output voltage is filtered by an LC filter with a cutoff frequency well below the switching frequency. According to steady-state analysis, the filter affects the performance of the motor drive, especially at high speeds. The stator current is not equal to the inverter current, and due to the inverter current and inverter voltage limits, the torque-maximizing stator current locus differs from that of a drive without the filter. A field-weakening method is proposed for PMSM drives with an inverter output filter. The method is implemented and tested in a <NUM>-kW PMSM drive. The experimental results agree well with the analysis, and validate the high-speed performance of the proposed field-weakening method.

"<NPL>, describes that Permanent Magnet Synchronous Machines (PMSM) are more suitable in power train due to the space factor. The size of PMSM is small due to the energy density in the machine is very high. To generate additional torque salient pole PMSM is used since reluctance torque is generated. For accurate design of PI-controllers and for calculating reference currents, the knowledge of machine parameters are needed. Machine parameters are obtained in two ways i.e., either by using lookup tables (experimental methods) or by estimating machine parameters. Inductances are estimated from discrete model of PMSM i.e., online parameter estimator. At each instant inductances are estimated by sensing dc link voltage and current of inverter. Finally these estimated inductances are implemented in MTPA/MTPF (Maximum Torque Per Ampere/Maximum Torque Per field) algorithm to calculate reference direct and quadrature axis currents (i dref and i qref ).

The features of the claimed invention are provided in the independent claims, to which reference should now be made. Additional, optional features are provided in the dependent claims.

As used in this document, adapted to, arranged to or configured to means that one or more data processors, logic devices, digital electronic circuits, delay lines, or electronic devices are programmed with software instructions to be executed, or are provided with equivalent circuitry, to perform a task, calculation, estimation, communication, or other function set forth in this document.

An electronic data processor means a microcontroller, microprocessor, an arithmetic logic unit, a Boolean logic circuit, a digital signal processor (DSP), a programmable gate array, an application specific integrated circuit (ASIC), or another electronic data processor for executing software instructions, logic, code or modules that are storable in any data storage device.

In any of the equations referenced throughout this document and appended claims, the terms are defined as follows, where an asterisk (*) can modify the below current and voltages to mean commanded voltages and an torque to mean commanded torque:.

<FIG> is a block diagram of one illustrative embodiment of an electrical control system <NUM> for a vehicle in which implement loads (e.g., electric machines or alternating current electric motors) can be coupled or decoupled to the vehicle electronics. An electrical control system <NUM> of the vehicle has a power source <NUM>, such as an internal combustion engine that provides rotational energy to an electric machine, such as a generator or alternator. During operation, the alternator converts inputted rotational energy to alternating current electrical energy.

Within the power source <NUM>, the alternator output terminals are couped to an alternating-current (AC)-to-direct-current (DC) converter <NUM>, which may be referred to as a rectifier. The AC-to-DC converter <NUM> (e.g., rectifier) and one or more inverters (<NUM>, <NUM>, <NUM>) are coupled to a vehicle direct current (DC) bus <NUM>. Each inverter (<NUM>, <NUM>, <NUM>) can convert the DC bus voltage of the DC bus <NUM> to a corresponding alternating current output of one or more phases, which are available at connectors (<NUM>, <NUM>, <NUM> and <NUM>) as illustrated in <FIG>.

Further, each inverter (<NUM>, <NUM>, <NUM>) may be configured or programmed to output a different or targeted: (a) alternating current (AC) output level, (b) root mean squared voltage, or (c) peak-to-peak voltage that is matched or compatible with a removable load that may be connected or disconnected (e.g., independently, separately or collectively) from each respective inverter (<NUM>, <NUM>, <NUM>).

Although three inverters (<NUM>, <NUM>, <NUM>) and three corresponding loads (<NUM>, <NUM>, <NUM>) are illustrated in <FIG>, it is understood that virtually any number of inverters (<NUM>, <NUM>, <NUM>) and loads (e.g., m inverters and corresponding n loads respectively, where m and n are any positive whole numbers) can be supported by one or more DC buses, subject to the typical current capacity or other pragmatic engineering design limitations of the DC bus. As illustrated the first inverter <NUM> is removably coupled to a respective first load <NUM> via corresponding first connector <NUM>; the second inverter <NUM> is removably coupled to a respective second load <NUM> via corresponding second connector <NUM>; and the third inverter <NUM> is removably coupled to a respective third load <NUM> via a corresponding third connector <NUM> and fourth connector <NUM>. For example, each inverter (<NUM>, <NUM>, <NUM>) and its corresponding load (<NUM>, <NUM>, <NUM>), such as electric machine (e.g., alternating current motor) of an implement for a agricultural vehicle, a construction vehicle, heavy-equipment, lawn or turf care equipment, mining equipment, road maintenance, resurfacing or repair equipment, or another work vehicle, is connected by a connector (<NUM>, <NUM>, <NUM>, <NUM>), which may comprise a combination of a plug and socket, which configuration may adhere to ISO or other standards in practice.

<FIG> illustrates a block diagram of one embodiment of an inverter control system or its software and data modules <NUM>. In <FIG>, each block may represent a module. Each module may comprise software instructions, electronic hardware, or both. For example, the electronic data processor <NUM> (of <FIG>) may execute the software instructions, software and data modules <NUM> that are stored, read, retrieved, or accessed in the data storage device <NUM> via a data bus <NUM> to control an electric machine <NUM> coupled to the inverter control system.

In one embodiment, a first summer <NUM> receives an input of commanded torque <NUM> (T*) and estimated torque <NUM> (Tem) and outputs a first torque error <NUM> signal or data message for a sampling interval. As used throughout this document, reference number <NUM> represents the observed estimated torque, or the estimated, measured torque <NUM> (e.g., outputted by the torque estimation module <NUM>), which is generally based on measurements at the alternating current terminals (e.g., phase terminals) of the electric machine <NUM> (e.g., or in alternate configurations is based on a torque sensor associated with the rotor of the electric machine).

In one configuration, the first summer <NUM> is coupled to a torque compensation controller <NUM> controller (e.g., proportional integral controller or a proportional integral derivative (PID) controller). The torque compensation controller <NUM> controller receives the first torque error <NUM> signal (or data message) and the commanded torque <NUM> (T*) as inputs and determines the final commanded torque <NUM> (Tfinal*).

In one embodiment, the torque compensation controller <NUM> controller comprises a proportional integral controller. For example, the proportional integral controller can use feedback control in which one signal proportional to the error (e.g., first torque error <NUM> signal) is superimposed on a ramp obtained by integrating the corrected output (e.g., final commanded torque <NUM>), where the integral correction increases in response to the magnitude of the error (e.g., first torque error <NUM> signal) and the time during which the error persists.

In contrast, in an alternate embodiment, the torque compensation controller <NUM> uses a proportional integral derivative (PID) controller. A PID provides a correction based on proportional control, integral control and derivative control terms, where proportional control of an output parameter (e.g., final commanded torque <NUM>) is proportional to an error (e.g., first torque error <NUM> signal) and the derivative control adjusts or dampens the rate of change of the error correction. The output of the torque compensation controller <NUM> is capable of communication with a back-EMF adjustment module <NUM> and a second summer <NUM>.

The second summer <NUM> receives an input of the final commanded torque <NUM> (Tfinal*) and an estimated torque <NUM> resulting from equation-based control of the electric machine <NUM>, such as equation-based controller <NUM> (e.g., equation-based interior permanent magnet controller) that applies one or more of the following: (a) maximum torque per amp (MTPA) equations, and/or (b) field weakening (FW) equations. The second summer <NUM> outputs or provides a second torque error <NUM> signal based on a difference between the final commanded torque <NUM> and the estimated torque <NUM> (Test), which may comprise an equation-based estimated torque based on the MTPFA equations, FW equations, or both. The second summer <NUM> output is capable of communication to the torque-to-current controller <NUM>.

In one configuration, the torque-to-current controller <NUM> determines a commanded quadrature-axis current <NUM> (Iq*) based on the inputted second torque error <NUM> signal, which is outputted form the second summer <NUM>. The commanded quadrature-axis current <NUM> (Iq*) is applied to an equation-based control module <NUM>. The equation-based control module <NUM> determines or estimates a commanded current, such as commanded direct-axis current <NUM> (Id*) for the corresponding commanded quadrature-axis current <NUM> (Iq*) based on an estimated direct-axis inductance (Ld) and an estimated quadrature-axis inductance (Lq) of a respective electric machine <NUM>. Throughout this document, reference number <NUM> refers to: (a) commanded direct-axis current alone, or (b) the matched pair or combination (e.g., equation-determined combination from the equation based controller <NUM>) of commanded direct-axis current and quadrature-axis current.

For example, the inductance estimation module <NUM> may estimate the estimated direct-axis inductance (Ld) and an estimated quadrature-axis inductance (Lq) of a respective electric machine <NUM> to be consistent with one or more of the following: (a) maximum torque per amp (MTPA) equations, and/or (b) field weakening (FW) equations. Accordingly, the inductance estimation module <NUM> is configured to provide the estimated inductances as inputs to the equation-based control module <NUM>. Meanwhile, the equation-based control module <NUM> is capable of communicating estimated torque based on the commanded current (Id*, Iq*) to the second summer <NUM> and communicating the commanded current to the current regulator <NUM>.

In one configuration, the inductance estimation module <NUM> is configured to calculate or determine inductances that are bounded or constrained as a percentage of the nominal, initial, preliminary machine inductances of the electric machine <NUM>; moreover, the inverter <NUM> or data processor <NUM> is configured to use the calculated or determined inductances are if rotor speed and torque of the electric machine <NUM> is above a certain threshold to ensure that the current and voltage signals have an appropriate signal-to-noise ratio for accurate inductance calculation by the inductance estimation module <NUM>.

The current regulator <NUM> determines a commanded direct-axis voltage (Vd*) and a commanded quadrature-axis voltage (Vq*) that is provided to one or more of the following: (<NUM>) pulse-width modulation module <NUM>, (<NUM>) inductance estimation module <NUM> or inductance estimator, and (<NUM>) a torque estimation module or torque estimator <NUM>. As shown in <FIG>, the current regulator <NUM> is capable of communication with, or coupled to, the pulse-width modulation module <NUM>, such as a space-vector pulse-width modulation module.

In one embodiment, the pulse-width modulation module <NUM> drives a switching circuit <NUM>, such as power electronics switches (e.g., power field effect transistors or insulated gate bipolar junction transistors), with control signals <NUM>. As illustrated in <FIG> in conjunction with <FIG>, the first control signal (da) is associated with the first control terminals <NUM> of the first phase <NUM> of the switches (<NUM>, <NUM>); the second control signal (db) is associated with the second control terminals <NUM> of the second phase <NUM> of the switches (<NUM>, <NUM>); the third control signal (dc) is associated with the third control terminals <NUM> of the third phase <NUM> of the switches (<NUM>, <NUM>).

In turn, the switching circuit <NUM> is coupled to an electric machine <NUM>, such as a, interior permanent magnet, synchronous electric machine, or an alternating current electric motor or alternator. The electric machine <NUM> may have one or more phases that receive alternating current (e.g., sinusoidal control signals <NUM>) with different phase offsets to each other. Further, the electric machine <NUM> may be associated with a resolver, an encoder or another sensor for sensing an angular position, speed, velocity or acceleration of the rotor shaft.

In an alternate embodiment, the electric machine <NUM> may be associated with voltage sensors or current sensors associated with each phase or conductor that is coupled between the switching circuit <NUM> or electric machine <NUM>. As illustrated in <FIG>, the converter and velocity estimator <NUM>: (a) converts or transforms the observed three-phase current measurements (Ia, Ib, Ic) to equivalent d-q axis currents (Id, Iq) (e.g., as illustrated as data within rhomboid block <NUM>); (b) converts or transforms the observed three-phase voltage measurements (Va, Vb, Vc) to equivalent d-q axis voltages (Vd, Vq); (c) estimates the rotor velocity or rotor speed (such as the electrical rotor speed or velocity, ωe, as illustrated as data within rhomboid block <NUM>) of the rotor by determining angular position versus time of the rotor based on the observed three-phase current measurements (Ia, Ib, Ic) or observed three-phase voltage measurements (Va, Vb, Vc), transformed equivalents or electric machine parameters derived from such measurements or transformed equivalents.

For example, the converter and velocity estimator <NUM> may comprise one or more transformation modules that operate in accordance with the following features or processes. First, the estimator <NUM> may comprise a first transformation module (e.g., Clark transform module) that transforms the measured or observed three-phase currents or voltages into a two-axis, orthogonal stationary reference frame (e.g., Iα, Iβ).

Further, the estimator <NUM> may comprise a second transformation module (e.g., Park transform module). Second, following the Clark transformation, the Park transform module can transform the two-axis, orthogonal stationary reference frame into rotating reference frame, such as the observed direct-axis current (Id) and observed quadrature-axis current (Iq).

Third, the estimator <NUM> makes available or communicates any of the following data to the inductance estimation module <NUM> and the torque estimation module <NUM>: observed direct-axis current and observed quadrature-axis current, and electrical speed or electrical angular velocity of the rotor shaft of the electric machine <NUM>.

The inductance estimation module <NUM> is coupled to any of the following: (<NUM>) a resolver, encoder or sensor for sensing an angular position, speed, velocity or acceleration of the rotor shaft, (<NUM>) one or more current sensors or voltage sensors associated with the phase inputs between the switching circuit <NUM> and the electric machine <NUM>, (<NUM>) a transformation module, such as a Clark transformation module cascaded with, or in series with, a Park transform module, and/or (<NUM>) the converter and velocity estimator <NUM>.

In one embodiment, the inductance estimation module <NUM> is configured to receive any of the following: (<NUM>) a commanded direct-axis voltage (Vd*) from the current regulator <NUM>, (<NUM>) a commanded quadrature-axis voltage (Vq*) from the current regulator <NUM>, (<NUM>) a back EMF constant <NUM> from the back EMF adjustment module <NUM>, or (<NUM>) adjustment to the back EMF constant <NUM> from the back EMF adjustment module <NUM>. The inductance estimation module <NUM> provides an output to the equation-based controller <NUM>.

The back EMF adjustment module <NUM> is configured to receive a final commanded torque <NUM> and an estimated torque <NUM>. Meanwhile, the back EMF adjustment module <NUM> is configured to output a back EMF constant <NUM> or an adjustment to the back EMF adjustment module <NUM> based on the final commanded torque <NUM> and an estimated torque <NUM>.

The torque estimation module <NUM> is configured to receive the commanded direct-axis voltage (Vd*) and commanded quadrature-axis voltage (Vq*) from the current regulator <NUM>; the observed direct-axis current measurement (Id) and observed quadrature-axis current measurement (Iq) from the estimator <NUM> (or from sensors associated with the phase interconnections between the switching circuit <NUM> and the electric machine <NUM>), and electrical speed or electrical angular velocity of the rotor shaft of the electric machine <NUM>.

<FIG> is a block diagram of one embodiment of an inverter control system, where the switching circuit <NUM> is illustrated in greater detail. In <FIG>, the inverter comprises an electronic data processor <NUM>, a data storage device <NUM> and one or more data ports <NUM> coupled to a data bus <NUM> to support communications of data messages between or among the electronic data processor <NUM>, the data storage device <NUM>, one or more data ports <NUM> and data bus <NUM>.

In one embodiment, each phase of the switching circuit <NUM> comprises a low-side switch <NUM> and a high-side switch <NUM>. Further, the low-side switch <NUM> and the high-side switches <NUM> each have a control terminal and two switched terminals. For example, each low-side switch <NUM> and each high-side switch <NUM> comprises a semiconductor switch, such as a field effect transistor, or an insulated gate bipolar junction transistor. If the semiconductor switch comprises a field-effect transistor, the control terminal comprises a gate and the switched terminals comprise a source and drain. However, if the semiconductor switch comprises a bipolar junction transistor, the control terminal comprises a base or insulated gate and the switched terminals comprise an emitter and collector.

In one embodiment, each phase (<NUM>, <NUM>, <NUM>) of the switching circuit <NUM> comprises a low-side switch <NUM> and a high-side switch <NUM>, the low-side switch <NUM> and the high-side switch <NUM> each having a control terminal and two switched terminals. Each high-side switch <NUM> has its switched terminals coupled in parallel to a high-side diode <NUM>. Meanwhile, each low-side switch <NUM> has its switched terminals coupled in parallel to a low-side diode <NUM>.

In <FIG>, the first phase <NUM> comprises a low-side switch <NUM> and a high-side switch <NUM> with switched terminals coupled in series between the DC bus terminals <NUM>. The first control terminals <NUM> are connected between the data ports <NUM> and the control terminals of the switches (<NUM>, <NUM>) to control the pulse-width modulation signal outputted at the first output terminal <NUM>. The output of the first phase <NUM> is at a first output terminal <NUM>. For example, the pulse-width modulation can be configured to resemble, mimic, or attain a generally sinusoidal waveform at the first output terminal <NUM> (e.g., to control the electric machine in a motoring mode).

The second phase <NUM> comprises a low-side switch <NUM> and a high-side switch <NUM> with switched terminals coupled in series between the DC bus terminals <NUM>. The second control terminals <NUM> are connected between the data ports <NUM> and the control terminals of the switches (<NUM>, <NUM>) to control the pulse-width modulation signal outputted at the second output terminal <NUM>. The output of the second phase <NUM> is at a second output terminal <NUM>. For example, the pulse-width modulation can be configured to resemble, mimic, or attain a generally sinusoidal waveform at the second output terminal <NUM> (e.g., to control the electric machine in a motoring mode).

The third phase <NUM> comprises a low-side switch <NUM> and a high-side switch <NUM> with switched terminals coupled in series between the DC bus terminals <NUM>. The third control terminals <NUM> are connected between the data ports <NUM> and the control terminals of the switches (<NUM>, <NUM>) to control the pulse-width modulation signal outputted at the third output terminal <NUM>. The output of the third phase <NUM> is at a third output terminal <NUM>. For example, the pulse-width modulation can be configured to resemble, mimic, or attain a generally sinusoidal waveform at the third output terminal <NUM> (e.g., to control the electric machine in a motoring mode).

<FIG> illustrates one embodiment of a flow chart of a method for controlling an electric machine <NUM> via an inverter or controller that incorporates the software and data modules <NUM> of <FIG>. Further, the method of <FIG> may be used in conjunction with the inverter system <NUM> of <FIG>, where the inverter system <NUM> comprises an electronic data processor <NUM>, a data storage device <NUM>, and one or more data ports <NUM> coupled to a data bus <NUM> to support communications of data messages between or among the electronic data processor <NUM>, the data storage device <NUM>, one or more data ports <NUM> and data bus <NUM>. As illustrated in <FIG>, the software and data modules <NUM> may be stored in the data storage device <NUM> for execution by the electronic data processor <NUM>. Further, the electronic data processor <NUM> or inverter system <NUM> may be configured to operate an electric machine in a motoring mode, a regenerative braking mode, or in a power-generating mode.

In <FIG>, the method begins in step S200.

In step S200, a switching circuit <NUM> activates, modulates, or switches a low-side switch <NUM> and a high-side switch <NUM> of the inverter. For example, within any given phase (<NUM>, <NUM>, <NUM>) the low-side switch <NUM> is generally switched on or in an on-state, while the high-side switch is generally switched off or in an off-state; vice versa. To the extent that the switching circuit <NUM> has multiple phases, each phase can operate with a fixed or variable phase offset with respect to one or more other phases.

In step S202, a driver circuit, a pulse-width modulation module <NUM>, or an electronic data processor <NUM> is configured to provide control signals <NUM> to the control terminals (e.g., <NUM>, <NUM>, <NUM>) of the switching circuit <NUM>. For example, a driver circuit, a pulse-width modulation module <NUM>, or an electronic data processor <NUM> is configured to provide control signals <NUM> to the control terminals of the switching circuit <NUM> based on an commanded direct-axis input voltage (Vd*) and a commanded quadrature axis voltage (Vq*). Further, the current regulator <NUM> may provide or input the commanded direct-axis input voltage (Vd*) and a commanded quadrature axis voltage (Vq*) to the switching circuit <NUM>.

In step S203, the electronic data processor <NUM>, or a inductance estimation module stored in the data storage device <NUM>, estimates a direct-axis inductance (Ld) and a quadrature-axis inductance (Lq) associated with the electric machine <NUM> based on a back EMF constant <NUM> (λf or an estimated torque <NUM>), a commanded direct-axis voltage (Vd*), a commanded quadrature-axis voltage Vq*), an observed direct-axis current measurement (Id'), observed quadrature-axis current measurement (Iq'), and observed electrical rotor angular speed estimate (we'). Step S203 may be executed in accordance with various techniques, which may be applied separately or cumulatively.

Under a first technique, the electronic data processor <NUM>, or a inductance estimation module <NUM> stored in the data storage device <NUM>, estimates a direct-axis inductance (Ld) and a quadrature-axis inductance (Lq) associated with the electric machine <NUM> based on a back EMF constant <NUM> outputted by the back EMF module <NUM>, commanded direct-axis voltage (Vd*) outputted by the current regulator <NUM>, commanded quadrature-axis voltage (Vq*) outputted by the current regulator <NUM>, observed direct-axis current measurement (Id') outputted by the converter and velocity estimator <NUM> or a transformation module, observed quadrature-axis current measurement (Iq') outputted by the converter and velocity estimator <NUM> or a transformation module, and observed electrical rotor angular speed estimate (we') outputted by the converter and velocity estimator <NUM>, a sensorless position/motion estimator, an encoder or a resolver.

Under a second technique, the electronic data processor <NUM>, or an inductance estimation module <NUM> is configured to estimate a direct-axis inductance and quadrature-axis inductance associated with the electric machine <NUM> based on a first set of equations that assume a rotor resistance and magnetic flux, such as a constant rotor resistance and constant magnetic flux. For example, the rotor resistance may comprise a nominal, initial, preliminary or default rotor resistance that is storable and retrievable from the data storage device <NUM> by the processor <NUM> or storable and retrievable from a remote data storage device incorporated into the electric machine <NUM>. Similarly, the magnetic flux may comprise a nominal, initial, preliminary or default mutual magnetic flux that is storable and retrievable from the data storage device <NUM> by the processor <NUM> or storable and retrievable from a remote data storage device incorporated into the electric machine <NUM>.

In step S204, an electronic data processor <NUM> or torque estimation module <NUM> estimates an observed or estimated torque <NUM> associated with a rotor of the electric machine <NUM> based on one or more of the following data parameters: (a) commanded direct-axis voltage (Vd*) and a commanded quadrature axis voltage (Vq*); (b) observed direct-axis current measurement (Id') and an observed quadrature axis current measurement (Iq'), (c) observed electrical or mechanical angular rotor speed or velocity estimate (we'), and (d) one or more estimated inductance parameters. For example, an electronic data processor <NUM> or torque estimation module <NUM> is configured to estimate an observed or estimated torque <NUM> associated with a rotor of the electric machine <NUM> based on one or more of the following data parameters: (a) commanded direct-axis voltage and a commanded quadrature axis voltage; (b) observed direct-axis current and an observed quadrature axis current, and (c) observed electrical or mechanical angular rotor speed or velocity, where the observed or estimated torque <NUM> is proportional to the observed power consumption of the electric machine <NUM> (e.g., in a motoring mode).

In step S206, the electronic data processor <NUM> or pulse-width modulation module <NUM> provides a pulse-width modulated signal to the electric machine <NUM> based on the commanded direct-axis voltage and commanded quadrature-axis voltage.

In step S208, the electronic data processor <NUM> or a back electromotive force module <NUM> determines or derives a back EMF constant <NUM> or an adjustment to the back EMF constant <NUM> for a sampling interval or measurement time interval that is based on an estimated, observed torque and a commanded torque <NUM>. Further the back EMF constant <NUM> or adjusted back EMF constant, modifies the estimated inductances (Ld, Lq) that are applied with the equation-based control of the equation based controller <NUM> for the MTPA mode, the field weaking mode, or both.

In accordance with one embodiment, as set forth in <FIG>, <FIG> and <FIG> upon electrically connecting an electric machine <NUM> to a controller, the inverter operates based on preliminary or initial electric machine parameters (e.g., default machine parameters) associated with the corresponding electric machine <NUM> (e.g., interior permanent magnet electric machine) that are stored, read or retrieved from a data storage device <NUM> or that are stored, read and retrieved from a remote data storage device incorporated into the electric machine <NUM>. During operation of the electric machine <NUM> based on the initial electric machine parameters, an inductance estimator <NUM> of the controller is configured to estimate an estimated direct inductance and an estimated quadrature inductance associated with the electric machine <NUM> (e.g., without prior characterization, commissioning or testing to establish any reference parameters or look-up tables related to the electric machine <NUM>) based on a first set of equations that assume (e.g., a default, preliminary, or initial) rotor resistance and (e.g., a default, preliminary, or initial) magnetic flux (or a combination of (e.g., default, preliminary or initial) back EMF constant <NUM> and number pole pairs). Further, the inverter, electronic data processor <NUM> or inductance estimator <NUM> estimates the estimated direct inductance and estimated quadrature inductance to be consistent with an operating point or operating region of the maximum torque per amp (MTPA) curve, a maximum torque per voltage (MTPV) curve, and/or a field weakening (FW) region based on respective commanded direct-axis voltage (or current) and a commanded quadrature-axis voltage (or current). Typically, the MTPA (operational) mode and the equivalent MTPV (operational) mode or mutually exclusive to the FW (operational) mode of the combined inverter and electric machine <NUM>.

In one embodiment, a torque estimator <NUM> is configured to estimate an estimated torque (e.g., observed torque estimate) associated with a rotor of the electric machine <NUM> based on one or more of the following: (a) the respective commanded direct-axis voltage (or current) and a commanded quadrature-axis voltage (or current) that are derived from a raw commanded torque <NUM> (e.g., from an operator or end user of the electric machine), where the estimated torque (e.g., observed torque estimate) is generally proportional to the observed power consumption of the electric machine <NUM>, and/or (b) the respective commanded direct-axis voltage (or current), a commanded quadrature-axis voltage (or current, an estimated direct-axis inductance of the electric machine <NUM>, and an estimated quadrature-axis inductance of the electric machine <NUM>.

First, a torque-to-current controller <NUM> (e.g., proportional integral control) determines a commanded quadrature-axis current <NUM> based on a commanded torque <NUM>. Second, the electronic data processor <NUM> or equation-based control module <NUM> estimates the corresponding commanded direct-axis current to the commanded quadrature-axis current <NUM>: (a) to be consistent with an operating point of the maximum torque per amp (MTPA) curve and/or a field-weakening (FW) region based on respective commanded direct-axis voltage (or current) and a commanded quadrature-axis voltage (or current) and (b) based on the estimated direct inductance and estimated quadrature inductance.

A pulse-width-modulation (PWM) module <NUM> is configured to provide pulse-width modulated signals (e.g., for each phase) to the electric machine <NUM> based on the commanded direct-axis voltage and a commanded quadrature-axis voltage. A back-electromotive force constant <NUM> (e.g., to the commanded direct-axis voltage and the commanded quadrature-axis voltage) is derived from an estimated torque (e.g., observed torque estimate) and a commanded and a final commanded torque <NUM> to estimate any potential adjustment to the back EMF constant <NUM>, which, in turn, can shift, adjust or transition the operating point, the operating region, the MTPA mode, or the FW mode determined by the equation-based control <NUM>.

In accordance with the embodiment of <FIG>, an inverter for controlling an electric machine <NUM> comprises a switching circuit <NUM>. Each phase of a switching circuit <NUM> further comprises a low-side switch <NUM> and a high-side switch <NUM>. The low-side switch <NUM> and the high-side switch <NUM> each have a control terminal and two switched terminals. A driver circuit is configured to provide control signals <NUM> to the control terminals of the switching circuit <NUM>. A data storage device <NUM> is in communication with the electronic data processor <NUM>.

An equation-based control module <NUM> (of <FIG>) is stored in the data storage device <NUM> (of <FIG>). The equation-based control module <NUM> comprises software instructions for execution by the electronic data processor <NUM>. An inductance estimator <NUM> is stored in the data storage device. The inductance estimator <NUM> comprises software instructions for execution by the electronic data processor <NUM>. In particular, the inductance estimator <NUM> is configured to estimate direct inductance and quadrature inductance associated with the electric machine <NUM> based on a first set of equations that assume constant rotor resistance and constant magnetic flux.

In one embodiment, the inverter or software and data modules <NUM> do not store in the data storage device <NUM> (e.g. as a factory setting) one or more customized look-up tables that were characterized in a lab to be matched, tailored or aligned with a corresponding particular electric machine <NUM> to facilitate proper control of the electric machine <NUM>. However, in the data storage device <NUM> of the inverter <NUM> or a remote data storage device at the electric machine <NUM>, the inverter <NUM>, the electric machine <NUM>, or both may store a preliminary, initialization look-up table, file, set of records or other data structure that comprises general, preliminary or generic initial values of machine parameters that: (<NUM>) represent nominal, temporary or placeholder values, (<NUM>) allow the inverter and electric machine <NUM> to operate together temporarily for estimation final machine parameter values determined in accordance with one or more equations (e.g., via equation-based controller <NUM>) described in this disclosure, and (<NUM>) are replaced by the estimated final machine parameters that are determined in accordance with one or more equations described in this disclosure (e.g., via equation-based controller <NUM>), where the final machine parameters are automatically tailored or customized (e.g., during operation by an end under of the electric machine <NUM> and the corresponding inverter in the field, rather than a lab testing/commissioning/characterization by a skilled technician) to a particular pair or combination of inverter and electric machine <NUM>.

Accordingly, in one configuration, the data storage device <NUM> of the inverter <NUM> or remote data storage device of the electric machine <NUM> may store one or more of the following general initial values of machine parameters: direct-axis (d-axis) inductance, Ld (e.g., nominal, default, or initial direct-axis inductance); quadrature-axis (q-axis) inductance, Lq (e.g., nominal, default, or initial quadrature-axis inductance); stator resistance, Rs; back EMF constant <NUM>, λf; and pole pair number, p; where such initial or nominal values are not matched, customized or tailored to the electric machine <NUM>, but rather generic, adequate and sufficient to derive a matched, revised, aligned or tailored adjustment, or final values of machine parameters as the inverter and electric machine <NUM> operate in the field (e.g., or in distributed equipment to end users, rather than in a lab or factory calibration process).

To the extent that any general initial values of machine parameters, are stored in the remote data storage device <NUM> of the electric machine or its transceiver <NUM>, such general initial values of machine parameters or revised initial values of machine parameters can be communicated between the electric machine <NUM> and the inverter <NUM> via a data communications link <NUM>, where the initial values of the machine parameters can include, but are not limited to direct-axis (d-axis) inductance, Ld (e.g., nominal, default, or initial direct-axis inductance); quadrature-axis (q-axis) inductance, Lq (e.g., nominal, default, or initial quadrature-axis inductance); stator resistance, Rs; back EMF constant <NUM>, λf; and pole pair number, p.

As illustrated in <FIG>, the data communications link <NUM> may comprise: a first transceiver <NUM> at the inverter <NUM> and a second transceiver <NUM> at the electric machine <NUM> that communicate with each other via a communication channel <NUM>, such as a communications line, wireline, twisted pair(s), fiber optical cable, coaxial cable, wireless, optical, and/or electromagnetic communications. The communications channel <NUM> between the transceivers at the inverter <NUM> and electric machine <NUM> may comply with one or more technical standards or communication protocols: Ethernet (e.g., IEEE <NUM>, IEEE <NUM>, ETHERCAT devices and software for data communications and/or commercially available reduced-latency and reduced-jitter Ethernet interfaces), Controller Area Network (CAN data bus), ISO bus (ISO <NUM>), wireless local area network (e.g., IEEE <NUM>), Flat Panel Display Link (FDP), Low Voltage Differential Signaling (LFDS), or the like. ETHERCAT is a trademark of Beckhoff Automation GmbH.

In one embodiment, the first transceiver <NUM> at the inverter <NUM> is coupled to the data bus <NUM> (or one or more additional data ports <NUM>) that communicate with the data bus <NUM>. The transceivers (<NUM>, <NUM>) can communicate with each other via the communications channel <NUM> for one or more of the following: (a) to transmit, receive, store, retrieve, manage, process, and support communications of data messages, data packets or the like; (b) to transmit, receive, store, retrieve, manage, process and access initial values of machine parameters or revised initial values of machine parameters from the remote data storage device <NUM>; (c) to transmit, receive, store, retrieve, manage, process and to access voltage measurements, current measurements, and/or associated phase measurements, provided by one or more sensors <NUM>, which are associated with the alternating current terminals of the electric machine <NUM>, that are coupled to second transceiver <NUM> via one or more conductors <NUM>; (d) to transmit, receive, store, retrieve, manage, process and to access rotor speed measurements, encoder measurements and/or torque measurements provided by one or more sensors <NUM>, such as encoders, resolvers and torque sensors. As illustrated, each transceiver (<NUM>, <NUM>) may further comprise interface <NUM>, such as a digital-to-analog converter coupled to buffer memory for temporarily holding a buffer of data messages or data packets for processing, encoding, decoding, reception or transmission. In some configurations, the communications link <NUM> and associated communications channel <NUM> support real-time communications with acceptable latency and jitter characteristics suitable for control of the electric machine <NUM>.

The extended control modules comprise the equation-based control module <NUM>, the inductance estimator <NUM>, the back EMF module <NUM> and the torque estimator <NUM>, where any of the modules may incorporate software instructions for execution by the electronic data processor <NUM>. In one embodiment, an inductance estimator <NUM> is configured to estimate direct inductance (Ld) and quadrature inductance (Lq) associated with the electric machine <NUM> based on a first set of equations that assume constant stator resistance (Rs) and constant magnetic flux.

A torque estimator <NUM> is configured to estimate an observed torque associated with a rotor of the electric machine <NUM> based on, or derived from, a raw commanded torque <NUM> or the corresponding resultant commanded direct-axis voltage (Vd*) and a commanded quadrature-axis voltage (Vq*), where the estimated torque <NUM> can be configured to be proportional to the observed power consumption of the electric machine <NUM>. The raw commanded torque <NUM> is used to determine a corresponding commanded direct-axis current and a corresponding commanded quadrature-axis current (<NUM>, <NUM>) that given the estimated direct inductance and estimated quadrature inductance define an operating point or operating region consistent with one or more of the following target operating point parameters or operating region parameters: (a) maximum torque per amp (MTPA) curve or maximum torque per voltage curve (MTPV), (b) field-weakening (FW) voltage ellipse curve, and (c) a target set of torque-speed (e.g., rotor speed) curves, and (d) load on the electric machine <NUM>.

A pulse-width-modulation (PWM) module <NUM> is generally configured to provide pulse-width modulated signals to the electric machine <NUM> based on the commanded direct-axis voltage and a commanded quadrature-axis voltage.

In one embodiment, the commanded direct-axis voltage and the commanded quadrature-axis voltage are related to the corresponding commanded direct-axis current and the commanded quadrature-axis current (<NUM>, <NUM>) by the equations (e.g., inductance estimation equations) set forth in this disclosure based on variables such as stator resistance, direct axis inductance or quadrature axis inductance and electrical rotational speed of the rotor of the electric machine <NUM>.

The back EMF module <NUM> derives a back-electromotive force (e.g., back EMF) adjustment to the back EMF constant <NUM> (λf) from an observed, estimated torque <NUM> (Tem) and a final commanded torque <NUM> (Tfinal*). The back EMF module <NUM> can apply back EMF adjustment to adjust the final back EMF parameter that is used to calculate the final commanded currents and final estimated torque. For example, the back EMF module <NUM> is configured to revise or adjust previous (e.g., initial) commanded direct-axis current (Id*) and previous (e.g., initial) commanded quadrature-axis current <NUM> (Iq*) values with revised (e.g., final) commanded Id* and Iq* values, or their commanded direct-axis voltage and quadrature-axis voltage equivalents.

The inverter <NUM>, alone or in conjunction with the software and data modules <NUM>, may control the electric machine <NUM> in accordance with various techniques that may be applied cumulatively or separately.

Under a first technique, the current regulator <NUM>, software and data module <NUM> or electronic data processor <NUM> provides an output commanded direct-axis current <NUM>, which is associated with a respective input commanded direct-axis voltage, and an output commanded quadrature-axis voltage, which is associated with a respective commanded quadrature-axis current <NUM>.

Under a second technique, the commanded direct-axis voltage or current <NUM> and the commanded quadrature axis voltage or current <NUM> lie on a torque-speed curve (<NUM>) or within a torque speed region defined by multiple torque speed curves (<NUM>). For example, in the MTPA mode, the equation-based controller <NUM> is configured to determine commanded direct-axis voltage or current <NUM> and the commanded quadrature axis voltage or current <NUM> lie on a torque-speed curve (<NUM>) within the MTPA region, which is bounded by the MTPA curve <NUM>, the current limit circle <NUM> and the axis of the direct-axis current <NUM> (or alternately by the voltage ellipse <NUM>) of <FIG>. The torque-speed curve may be selected based on a torque load (e.g. Test <NUM>) on the electric machine <NUM> (e.g. traction drive motor or an implement electric motor for cutting or processing an agricultural, construction or building material), such as torque load range and/or speed range associated with a particular work task of a vehicle or machine on which the electric machine <NUM> operates.

Under a third technique, the torque estimator or torque estimation module <NUM> is configured communicate or cooperate with the torque compensation controller <NUM>, the torque-to-current controller <NUM>, and the equation-based controller <NUM> to estimate the commanded direct-axis voltage or current <NUM> and the commanded quadrature axis voltage or current (<NUM>, <NUM>) lie within a region of a torque speed curve bounded by a maximum quadrature-axis current <NUM> based on the estimated torque <NUM>, wherein torque estimator <NUM> is configured to estimate the estimated torque <NUM> (T or Tern) in accordance with the following equation: <MAT>.

Under a fourth technique, the equation-based control module <NUM> is configured to determine the commanded direct-axis voltage or current and the commanded quadrature axis voltage or current (<NUM>) to lie within a region of a torque-speed curve <NUM> bounded by a field weakening (FW) voltage ellipse <NUM> and a set of one or more maximum torque per amp (MTPA) curves <NUM>, wherein the field weakening voltage ellipse <NUM> is derived based on quadrature-axis current (iq), direct inductance (Ld), quadrature inductance (Lq) back-electromotive force constant (λf), DC voltage bus (Vdc), the rotor electrical velocity (ωe), and the modulation frequency of the alternating current signals applied to the electric machine <NUM> and wherein the set of one or more maximum torque per amp (MTPA) curves are derived based on quadrature-axis current (iq), direct inductance (Ld), quadrature inductance (Lq) back-electromotive force adjustment (λf). Further, it is possible to estimate a set of one or more operating MTPA curves (e.g., similar to illustrative MTPA curve <NUM>) based on a selection of d-axis current range and a corresponding torque range, although among MTPA curves there is generally a preferential or target MTPA within the operating region that has a greatest d-axis current range and a greatest torque (e.g., which may be required for efficient operation consistent with the applicable load or to meet an industrial application).

Under a fifth technique, the equation-based control module <NUM> is configured to determine the commanded direct-axis voltage or current and the commanded quadrature axis voltage or current (<NUM>) to lie within a region of a torque-speed curve <NUM> bounded by a field weakening (FW) voltage ellipse <NUM> and a set of maximum torque per amp (MTPA) curves, wherein the direct-axis current associated with the field weakening voltage ellipse <NUM> is determined consistent with the following equation: <MAT>.

Under a sixth technique, the equation-based control module <NUM>, alone or together with the extended control modules, are configured to determine the commanded direct-axis voltage or current and the commanded quadrature axis voltage or current (<NUM>) that lies within a region of a torque-speed curve bounded by a field weakening (FW) voltage ellipse and a set of maximum torque per amp (MTPA) curves, wherein the corresponding direct-axis current or corresponding set of maximum torque per amp curves is determined consistent with the following equation: <MAT>.

Under a seventh technique, the inverter <NUM> or the software and data modules <NUM> do not need a characterization look-up table that defines the electronic machine, such as an interior permanent magnet electric machine <NUM> (IPM). Instead, the inverter <NUM> or software data modules <NUM> comprises a first summer <NUM> that is coupled to an input of torque compensation controller <NUM> (e.g., proportional integral controller) and the output of the controller <NUM> is coupled to the equation-based controller <NUM>, where the equation-based controller <NUM> comprises an operating region estimator that has a maximum-torque-per-amp (MTPA) region estimation module and a field-weakening (FW) region estimation module. In one embodiment, the first summer <NUM> receives a commanded torque <NUM> and an estimated torque <NUM> output by a torque estimation module <NUM> to estimate an error signal that is applied to the torque-compensation controller <NUM>. In turn, the torque-compensation controller <NUM>, together with the torque-to-current controller <NUM>, are configured to provide commanded quadrature-axis current <NUM> to the equation-based controller <NUM> to support its estimation of the proper operating region: (a) on the d-q axis plane, that is associated with corresponding direct-axis current and quadrature-axis current, and (b) a proper torque and speed.

Under an eighth technique, the equation-based controller <NUM> or the electronic data processor <NUM> of the inverter <NUM> (or the torque estimation module <NUM>) determines the estimated torque (Test) <NUM> (or the estimated torque (Tem) <NUM>, respectively, where Tem is substitute for Test) in accordance with the following equation: <MAT>.

Under a ninth technique, the back-EMF module <NUM>, alone or in conjunction with the inductance estimation module <NUM> and the equation-based controller <NUM>, is configured to determine or adjust a back-EMF constant or final back EMF, λf, in accordance with the following equations: <MAT> <MAT>.

The back EMF constant <NUM> may be defined as the ratio of estimated, measured torque <NUM> (Tem or Test) to commanded torque Tcmd or final commanded torque <NUM>, Tfinal*. The back EMF constant <NUM> is multiplied by the initial back EMF, λinitial, to yield the final back EMF, λf, which may be referred to generally as back EMF. The back EMF constant <NUM> or back EMF adjustment ratio may be expressed as a percentage, a ratio or a fraction, all which are unitless. The back EMF constant <NUM> may represent a strength of a linked magnetic flux, such as a linked magnetic flux between the rotor permanent magnets and the stator electromagnets.

If the back-EMF module <NUM> is configured to adjust the back-EMF constant from a previous (e.g., initial) back-EMF constant to a next or revised (e.g., final) back EMF constant, where the adjustment may be expressed as a differential value, a percentage value, or a fraction. For example, the back-EMF module <NUM> or the electronic data processor may revise the next back-EMF constant (e.g., for a next sampling interval of the raw commanded torque (T*)) to be within a range (e.g., of approximately eighty-five percent to approximately one hundred and fifteen percent) of the previous or prior back EMF constant <NUM> (e.g., for the prior sampling interval prior to the next sampling interval of the raw commanded torque (T*)). Accordingly, the adjustment (e.g., differential adjustment) to the present or next back-EMF constant can be determined as a difference, a fractional or percentage change from the previous or prior back-EMF constant. The adjustment to the back EMF constant <NUM> may be used to provide an improved or more accurate estimate of the strength of the magnetic flux that is associated with operating the electric machine <NUM> for a time period (e.g., that supports time-averaging or statistical analysis of observations, measurements) under certain rotor speed, ambient temperature, load, or field weakening of permanent magnets in the electric machine <NUM> responsive to elevated ambient or operating conditions, or other operating conditions and parameters.

The adjustment of the back EMF constant <NUM> should be distinguished from adjustments to the commanded direct-axis current and commanded quadrature axis current that the electronic data processor <NUM> is configured to estimate and apply to the windings of the electric machine <NUM> to reduce or compensate: (a) for any first torque error <NUM>, which is a difference between the raw commanded torque <NUM> (T*) and the estimated torque <NUM> (Tem), and/or (b) for any second torque error <NUM>, which is difference between the final commanded torque <NUM> and measured estimated torque (Test) of the electric machine <NUM>. Similar to above current adjustments to the electric machine <NUM>, the adjustment of the back EMF constant <NUM> should be distinguished from any equivalent adjustments to the commanded direct-axis voltage and commanded quadrature axis voltage that the electronic data processor <NUM> is configured to determine and apply to the windings of the electric machine <NUM> to reduce or compensate: (a) for any first torque error <NUM>, which is a difference between the raw commanded torque <NUM> (T*) and the estimated torque <NUM> (Tem), and/or (b) for any second torque error <NUM>, which is difference between the final commanded torque <NUM> and measured estimated torque (Test) of the electric machine <NUM>.

Under a tenth technique, the inverter <NUM> or electronic data processor <NUM> uses the following initial, preliminary or default electric machine parameters that are storable in the data storage device <NUM> to control the electric machine <NUM> that are determined by one or more equations during start-up, initialization, or other first operation of the inverter coupled (e.g., electrically) to the respective electric machine <NUM>: Ld (e.g., measured in µH), Lq (measured in µH), Rs (measured in ohms), λf, (unitless ratio) and number of pole-pairs (P) of rotor and stator magnets, such as permanent magnets in the rotor and electromagnets in the stator. However, after the first start-up, first initialization or other first operation of the inverter coupled to the respective machine, the inverter may store automatically, without lab testing or intervention of skilled engineer, technician or any other person, the revised or refined versions (e.g., revised data sets with corresponding time/date stamps) of the electric machine parameters in a data storage device <NUM> (e.g., electronic non-volatile random access memory) for later access (as revised, adjusted or updated electric machine parameters based on the initial, preliminary or default electric machine parameters) upon the next start-up, next initialization, or next operation of the inverter coupled to the same respective electric machine <NUM>.

Under an eleventh technique, an equation-based method of this disclosure is configured to use a torque-to-current controller <NUM> (e.g., proportional integral (PI) controller) to determine a commanded quadrature-axis current <NUM> (Iq) based on a given final commanded torque <NUM> (Tfinal*), which is derived from the raw commanded torque <NUM> (T*). Next, the equation-based controller <NUM> is configured to determine the corresponding commanded direct axis current (Id) using the equations defined for the MTPA and/or FW (field-weakening) regions. To the extent that the torque-to-current converter <NUM> comprises a proportional integral controller, the controller <NUM> applies a second torque error <NUM> as feedback (based on estimated torque (Test) from the equation-based controller <NUM>) to control an output signal proportional to the second torque error <NUM> that is superimposed on a ramp obtained by integrating the commanded quadrature-axis current output <NUM>.

To estimate the inductance of the electric machine <NUM> during initialization, start-up, or operation of the electric machine <NUM> coupled to an inverter <NUM>, an electronic data processor <NUM> of the inverter <NUM> determines the direct-axis inductance, Ld, and quadrature-axis inductance, Lq, from steady-state voltage equations based on the initial, preliminary, default or nominal electric machine parameters (e.g., stored in the data storage device <NUM>) of stator resistance, Rs, and back-emf constant, λf. In one embodiment, the d-axis voltage and q-axis voltage (collectively d-q axis voltages) in the below equations are the filtered, commanded d-q axis voltages (Vd* and Vd*) outputted from the current regulator <NUM> (e.g., CVCR or Complex Vector Current regulator). The remaining variables including the observed direct-axis current, Id, the observed quadrature-axis current, Iq, and electric machine speed (ωe) are derived, by the converter and velocity estimator <NUM>, from measurements of the three phase voltages (da, db, and dc) at the terminals of the electric machine <NUM>. During initialization, start-up or operation of the electric machine <NUM> coupled to an inverter <NUM>, the data processor <NUM> of the inverter <NUM> determines or estimates Lq based on the equations below: <MAT> <MAT>.

During initialization, start-up or operation of the electric machine <NUM> coupled to an inverter <NUM>, the data processor <NUM> of the inverter <NUM> determines or estimates, Ld is derived from the Vq equations below: <MAT> <MAT>.

To execute the above inductance equations, the electronic data processor <NUM> may retrieve, read, access or obtain from the data storage device <NUM>, the initial values or nominal machine values for the stator resistance and back EMF constant <NUM> (λf).

In some embodiments, the back EMF may be defined as a voltage that results from multiplying the rotational mechanical velocity (ωmech) of the rotor of the electric machine <NUM> by the back EMF constant <NUM> (λf), as adjusted from time to time (e.g., each sampling interval) by an back EMF adjustment. The back EMF module or electronic data processor <NUM> may limit the adjustment of the back EMF constant to bound or constrain it within a certain percentage (e.g., approximately <NUM>% to <NUM>%) of the nominal, preliminary, or default EMF constant (e.g., that was stored in the data storage device <NUM> of the inverter <NUM> or remote data storage device of the electric machine.

For example, the back EMF is a voltage that opposes the voltages or currents applied to the stator windings of the electric machine <NUM>. The back EMF may arise from the inductance in the stator windings and the changes in the current applied to the stator windings. The back EMF leads to some loss of efficiency in the electric machine <NUM>, where the actual observed torque <NUM> (Tem) or estimated measured torque tends to be less than the raw commanded torque <NUM> (T*) in the absence of an adjustment to back EMF constant <NUM> or a corresponding compensation of increased current or voltage applied to the stator windings.

In practice, the stator resistance and back EMF constant <NUM> can fluctuate with respective changes in temperature, which can require a temperature adjustment or temperature compensation in the inductances of the electric machine <NUM>. For example, the electric machine <NUM> may include one or more temperature sensors that measure an observed temperature of a stator winding, electromagnet, a magnet, or the electric machine <NUM>, where the measured observed temperature is associated with a corresponding temperature coefficient (e.g., stored, read, accessible or retrievable from the data storage device <NUM>), where the data processor <NUM> multiplies a respective original inductance (e.g., Ld, Lq, or both) by the applicable corresponding temperature coefficient to determine a temperature-compensated inductance (e.g., Ldtc, Lqtc, or both) that reduces or eliminates temperature error in the Ld and Lq calculation. Accordingly, in any of the equations a temperature-compensated inductance may replace its counterpart uncompensated or original inductance.

A minimum threshold speed of the rotor of the electric machine <NUM> may refer to the base speed of the rotor. In some electric machines <NUM>, such as an internal permanent magnet motor (e.g., permanent magnet synchronous motor), the alternating current (AC) voltage at the machine terminals (e.g., three-phase winding terminals) or motor terminals reaches a maximum value at the base speed. For the base speed or a greater speed of the rotor of the AC electric machine <NUM>, the alternating current voltage can be used to charge an energy storage device, such as a capacitor or battery that are coupled to the DC bus terminals <NUM>.

In other electric machines <NUM>, such as a switched reluctance motor, at the base speed the back electromotive force (EMF) is proportional to (e.g., generally equal to) the voltage of the DC bus <NUM>. The back EMF generally increases with the rotor speed.

If the rotor speed of the electric machine <NUM> is equal to or greater than a minimum speed threshold (e.g., base speed) and if the torque (e.g., raw commanded torque <NUM>) of the electric machine <NUM> is equal to greater than a minimum torque, the electronic data processor <NUM> determines the inductance values in accordance with the above equations; the electronic data processor <NUM> applies the determined inductances to corresponding current calculations. However, if the rotor speed of the electric machine <NUM> is less than a minimum speed (e.g., base speed) threshold and if the torque (e.g., raw commanded torque <NUM>) of the electric machine <NUM> is less than a minimum torque, the data processor <NUM> will not estimate the inductances of the electric machine <NUM> based on the above equations to avoid potential inaccuracy associated with current and voltage signals with low signal-to-noise ratio. Instead, the data processor <NUM> or inverter <NUM> will wait one or more intervals and recheck whether the electric machine <NUM> is or remains less than a minimum speed threshold (e.g., base speed) and if the torque (e.g., raw commanded torque) of the electric machine <NUM> is or remains less than a minimum torque. If the commanded torque <NUM> or rotor speed of the electric machine <NUM> are below the thresholds, the data processor <NUM> may use and hold one or more of the following: (a) previous acceptable inductance values determined by the equations until the electric machine <NUM> transitions to higher load/ rotor speed condition that meets the above thresholds, or (b) nominal inductance values or initial inductance values provided by the manufacturer, its specifications, or by factory/lab measurements that apply to the corresponding electric machine <NUM>. In an alternate embodiment, the nominal inductance values or initial inductance values for a particular corresponding electric machine <NUM> are determined by reference to specifications or inductance values applicable to corresponding model number, serial number or both of the electric machine <NUM>, where the nominal inductance values or initial inductance values can be stored in a readable radio frequency (RF) identification tag attached to the electric machine <NUM>, provided the inverter is configured with a RF tag reader coupled to data ports <NUM> of <FIG>).

The data processor <NUM> or converter and velocity estimator <NUM> estimates a rotor speed of the electric machine <NUM> by a sensor-less (not a senseless) rotor speed detection mechanism, such as estimating the rotor speed by current sensors or voltage sensors on one or more alternating current phases (e.g., stator windings to which one or more substantially sinusoidal signals or quasi-sinusoidal signals that resemble or approximate true sinusoidal signals are applied) by the inverter <NUM> to the electric machine <NUM>. However, in an alternate embodiment, a rotor speed sensor (e.g., sensor <NUM> in <FIG>) may comprise an encoder, a resolver, or a magnetic field sensor associated with an embedded magnet or magnetized portion of the rotor to provide an estimated or observed rotor speed.

In an alternate embodiment, any current sensor, voltage sensor, voltage magnitude and phase sensor or current magnitude and phase sensor (e.g., individually or collectively sensors <NUM> in <FIG>); any encoder, resolver, magnetic field sensor, or torque sensor (e.g., individually or collectively sensor <NUM> in <FIG>) that measures or observes any operating parameters of electric machine <NUM> may be provide analog or digital signals, where analog signals are provided to a digital-to-analog converter and outputted to an interface <NUM> of the transceiver (<NUM>, <NUM>) associated with a communications link <NUM> for communicating data measurements or observations of voltage (da, db, dc), current (e.g., derived from da, db, dc), rotor mechanical speed, rotor electrical speed or torque to the data bus <NUM> (or one or more additional data ports <NUM>) of the inverter <NUM>, and/or to the converter and velocity estimator <NUM>.

If the observed rotor speed is less than or equal to a first rotor speed threshold, then the electronic data processor <NUM> or controller of the inverter <NUM> may operate in the MTPA region of the direct-quadrature current plane (e.g., defined by a combination of an inverter <NUM> and electric machine <NUM>) or in corresponding MTPA mode. The maximum quadrature axis current tends to be associated with a corresponding maximum operational torque or maximum operational torque region of the electric machine <NUM>. For the MTPA mode, the maximum quadrature-axis current Iq <NUM> is defined as the point where the MTPA curve <NUM> intersects the current limit circle <NUM>. Further, in the MTPA mode the electronic data processor <NUM> or controller of the inverter uses a first equation for estimation of peak Iq or maximum quadrature-axis current, Iq (e.g., <MAT>) based on MTPA region as follows: <MAT> where:
Is_max is the maximum quadrature-axis current of the stator windings of the electric machine <NUM> within the MTPA region or on the MTPA curve <NUM>.

In practice, the maximum quadrature-axis current of the stator windings may be aligned with or limited by the current ratings of the semiconductor switches (<NUM>, <NUM>) in the switching circuit <NUM> of the inverter <NUM>. For example, the first equation to determine maximum quadrature-axis current, Iq, (e.g., <MAT>) may represent the operating region (or peak Iq) where the MTPA curve intersects a current limit circle <NUM> (e.g., circumscribing an arc about an origin of the Iq and Id axes.

However, if the observed rotor speed is greater than a first rotor speed threshold or base speed of the electric machine <NUM>, then the electronic data processor <NUM> or controller of the inverter <NUM> may operate in the field-weakening region or the corresponding field weakening mode. In one embodiment, the filed weakening mode is generally mutually exclusive to the MTPA mode. Further, in the field weakening mode the electronic data processor <NUM> or controller uses a second equation for estimation of peak Iq or maximum, <MAT>, based on field weakening as follows: <MAT> where futil is the utilization factor with a range between <NUM> and <NUM>.

In one embodiment, the utilization factor measures the output power of the inverter <NUM> divided by the sum of power switched by or within each of the output semiconductor switches in the inverter, based on a corresponding duty cycle or fixed duty cycle. Therefore, limiting the utilization factor can protect the inverter <NUM> from thermal damage. In another embodiment, the utilization factor comprises a voltage utilization factor expressed as percentage of the dc bus voltage (e.g., <NUM> percent of the DC bus voltage).

Once an estimated rotor speed of the electric machine <NUM> is above the first rotor speed threshold or base speed of the machine, the current commands no longer track along the MTPA curve, but follow the voltage ellipse instead of the FW mode. For example, in the field weakening mode the Iq maximum limit is not based on Iqmax <NUM> for the MTPA mode, but rather based on the Iq maximum calculated within the FW region bounded by the current limit circle <NUM> and the voltage ellipse <NUM>; hence, the corresponding equations for the voltage ellipse apply in the FW mode. For example, in FW region, the maximum torque may be associated with the voltage ellipse curve <NUM>, and can possibly align with one or more torque speed curves <NUM>.

The data processor <NUM> or inverter <NUM> can apply the commanded quadrature-axis current Iq of the PI controller <NUM> into the equations of the equation-based controller <NUM> to calculate the corresponding commanded direct-axis current (Id command) or a matched pair of the commanded q-axis current and commanded d-axis current <NUM>. In one embodiment, for the MTPA region, the data processor <NUM> of the inverter <NUM> determines the current commands (e.g., commanded Id current <NUM>) such that the commanded torque <NUM> or the estimated, measured torque <NUM> is reached with the smallest current magnitude possible. In one embodiment, the equation-based controller <NUM> in the MTPA mode is configured to determine the corresponding commanded indirect-axis current (Id*) following the MTPA curve by applying the following equation: <MAT>.

The above commanded indirect-axis current (Id*) is a function of the estimated back EMF constant <NUM>, λf ; inductances <NUM> Lq, Ld; and commanded quadrature-axis current <NUM> (Iq or Iq*).

For the field weakening region, which is above the minimum threshold rotor speed (e.g., base speed) of the electric machine <NUM>, the voltage of the DC bus <NUM> may be limited, or rather place attendant limits on the extent of size of the FW voltage ellipse <NUM>. The commanded direct-axis current, <MAT> * for the field weakening mode, is a function of the voltage of the DC bus <NUM>, electric rotor speed of electric machine <NUM>, estimated inductances <NUM>, back-EMF constant <NUM>, and the commanded quadrature-axis current <NUM>, Iq*. The value of utilization factor, futil, is selected to protect the inverter <NUM>, where the value may range from <NUM> to <NUM>. For example, the utilization factor can be set to (use) ninety-five percent (e.g., <NUM>%) of the available voltage of DC bus <NUM> or its associated power, which may limit, scale or reduce the size of the FW voltage ellipse <NUM>. In the field weakening mode, the inverter or data processor operates above the minimum threshold speed of the electric machine <NUM>, the commanded current <NUM> (e.g., commanded direct-axis current) no longer tracks along the MTPA curve, but follows the voltage ellipse instead. The following equation gives the <MAT> as a function of the iq* command: <MAT>.

During operation, the inverter <NUM>, alone or together with the software and data modules <NUM>, automatically switch between the MTPA mode and FW mode based upon terminal voltage, or squared total terminal voltage the represents the sum of the squares. Regardless of which mode the inverter <NUM> is operating in, for a current sampling interval of the raw commanded torque and measured, estimated torque and associated measured, estimated (electric or mechanical) rotor speed ωe, direct-axis current (Id'), quadrature-axis current (Iq') <NUM>, the equation-based controller <NUM> or data processor <NUM> is configured to determine current commands (of d-axis and q-axis commanded currents) simultaneously for MTPA and FW regions, such as a first current command pair for the MTPA mode and a second current command pair for the FW mode. Further, based on estimated parameters, the current regulator <NUM> or data processor <NUM> is configured to determine the corresponding terminal voltages simultaneously for each region, including but not limited to the MTPA region and the FW region. For any phase the voltage of the stator winding can be measured or estimated based on measurements, which the converter and velocity estimator <NUM> transforms to the d-q reference frame or plane. For instance, within the d-q reference frame, a lowest voltage of any phase of the stator windings (of the electric machine <NUM>) represents the limiting terminal voltage; the data processor <NUM> determines which mode the inverter <NUM> operates in based on the such limiting terminal voltage, consistent with the following equation: <MAT>.

In one embodiment, the inverter <NUM> and the data processor <NUM> may transition between the FW mode and MTPA mode, or vice versa, via a hysteresis band based on observed terminal voltage (e.g., of the alternating current terminals of the electric machine <NUM>). For example, the hysteresis band may delay a transition between the modes for one or more sampling intervals or a predetermined time period until an average, mean or mode of the limiting terminal voltage suggests that a change is required. Therefore, the inverter <NUM> and the data processor <NUM> are configured with the hysteresis band to ensure that there is not instability or oscillation between modes which could cause disturbances with the control of the electric machine <NUM>.

The equation-based controller <NUM> is configured to determine estimated torque <NUM> (Test) based on the commanded direct-axis current and the commanded quadrature-axis current <NUM> in accordance with the following equation: <MAT> Further, estimated torque <NUM> (Test) serves as the feedback loop for the torque-to-current controller <NUM> (e.g., PI controller) to adjust the commanded Iq* <NUM> accordingly.

In an alternate configuration, to determine the estimated torque to be fed back to the controller <NUM>, to the back EMF adjustment module <NUM>, or within the software and data modules <NUM>, the equation-based controller <NUM> can also estimate torque using the terminal power equation with speed in accordance with the following equation: <MAT>.

<FIG> is a graph of illustrative time-varying estimated inductance(s) (<NUM>, <NUM>) versus time for one embodiment of the inverter <NUM> and its associated software and data modules <NUM>. The vertical axis represents inductance <NUM>, which may be expressed in Henries. The horizontal axis represents time <NUM>, where the convergence time <NUM> is shown in the dashed lines. The filtered or estimated quadrature-axis inductance <NUM> and filtered or estimated direct-axis inductance <NUM> are aligned on the same time scale of the horizontal axis.

At an initialization time <NUM>, the electronic data processor <NUM> or the inductance estimation module <NUM> starts by retrieving an initial, default or preliminary value of the inductances (Ld, Lq) from the data storage device <NUM>. During operation of inductance estimation module <NUM> or inductance estimator, alone or together with the software and data modules <NUM>, the inductance estimation module <NUM> converges on a final value or final inductance values (Ld, Lq) (e.g., sometimes even temperature-compensated inductances achieved over continuous operation of the electric machine <NUM> may take longer to converge) at a convergence time <NUM>, which coincides with the completion of the automated characterization or commissioning of the electric machine parameters while operating the inverter and electric machine <NUM> in the field, without any assistance of a skilled technician. For example, the inverter may comprise the electronic hardware of <FIG> and the software and data modules <NUM> of <FIG>.

<FIG> is a graph of the direct-quadrature current plane in which a first axis represents quadrature-axis current <NUM> (e.g., commanded quadrature axis current) and a second axis represents direct-axis current <NUM> (e.g., commanded direct-axis current) associated with targeted operational points or targeted operational regions for controlling the electric machine <NUM>. As shown, the horizontal axis indicates direct-axis current <NUM> in a rotating d-q axis reference frame. Meanwhile, the vertical axis indicates the corresponding quadrature-axis current <NUM> in the rotating d-q axis frame. Collectively, the direct-axis current and the quadrature-axis current define a d-q current plane. In one embodiment, the equation-based control module <NUM> or electronic data processor <NUM> uses equations, final look-up tables or other data structures that can control the electric machine <NUM> in accordance with an MTPA mode, a FW mode, or both consistent with the curves, operational regions, and operational points that are illustrated in <FIG>.

A first operational boundary of the electric machine <NUM> (e.g., interior permanent magnet synchronous electric machine) is defined by the current limit arc <NUM>, which is also referred to as the current limit circle. In the d-q current plane of <FIG>, the current limit arc <NUM> is defined by an arc (e.g., a circular portion) that is based on thermal and power handling capabilities of the electric machine <NUM> and the inverter (e.g., switching circuit <NUM>).

A second operational boundary of the electric machine <NUM> is defined by the voltage ellipse <NUM>, which is also referred to as a field weakening voltage ellipse. The first operational boundary and the second operational boundary can be applied cumulatively to determine the operational region of the electric machine <NUM> and respective inverter. Separate from the current limit arc, one or more voltage ellipses can be defined, where each voltage ellipse <NUM> corresponds to the electric rotational speed of the rotor of the electric machine <NUM>. Further, the higher the electric rotational speed of the rotor of the electric machine <NUM>, the smaller the radius of the elliptical arc of the voltage ellipse <NUM>. The voltage ellipse depends on the following constraints: direct-axis inductance, the quadrature-axis inductance, the electric rotational speed of the rotor and maximum design voltage (e.g., related to DC bus voltage) for the stator windings of the electric machine.

For the MTPA mode, the equation-based control module can select any of the following operational points or operational regions that are within the current limit arc <NUM> (e.g., in the operational region between the axes (iq axis <NUM>, id axis <NUM>) and the current limit arc <NUM>): (a) an operating point that is on the MTPA curve <NUM> and below the maximum quadrature-axis current (Iq) or maximum commanded quadrature-axis current, (b) an operating point that is at intersection of the MTPA curve <NUM> and associated with one or more targeted torque-speed curves <NUM>, (c) a first MTPA operational region that is bounded by the current limit arc <NUM> and the MTPA curve <NUM> and an axis <NUM> of the direct-axis current (e.g., commanded direct-axis current or horizontal axis of <FIG>) or alternately by the voltage ellipse <NUM>, (d) a second operational region that is bounded by the current limit arc <NUM> and the MTPA curve <NUM> and the direct-axis current <NUM> and associated with one or more targeted torque-speed curves.

For the field weakening mode, the equation-based control module <NUM> can select any of the following operational points or operational regions that are within the current limit arc <NUM> and the voltage ellipse <NUM> that corresponds to the electrical rotational speed of the rotor. Accordingly, at higher electrical rotational speeds of the rotor, the field weakening mode tends to have lesser operational region, relative to the greater operational region of the MTPA mode that is suitable for lower electrical rotational speeds. For example, the field weakening operational region of <FIG> is defined by the region bounded by the voltage ellipse <NUM>, the current limit circuit <NUM>, and the direct-axis current <NUM> (e.g., or the horizontal axis of <FIG>).

<FIG> is a block diagram of a method of torque estimation without a look-up table. During initialization and operation of the electric machine <NUM>, in response to commanded torque <NUM> a proportional integral controller <NUM>, in conjunction with an equation-based controller <NUM>, determine estimations of: (<NUM>) commanded direct-axis current and commanded quadrature-axis current (<NUM>), and (<NUM>) a maximum-torque-per-amp (MTPA), a field weakening (FW) curve.

In one configuration, the commanded torque <NUM> and an estimated torque <NUM> are inputted into a summer <NUM> for a sampling interval. The summer <NUM> outputs a torque error signal <NUM> for the sampling interval. The torque error signal <NUM> alone, or the torque error signal and the commanded torque <NUM> together, are communicated to the proportional integral controller <NUM> to determine: (a) a differential change in a commanded quadrature-axis current from a previous commanded quadrature-axis current from one or more previous sampling intervals, (b) a commanded quadrature-axis current.

The equation-based controller <NUM> determines the commanded direct-axis current and commanded quadrature-axis current (collectively commanded d-q axis current data <NUM>) that are: (a) consistent with the received commanded quadrature-axis current (from proportional integral controller <NUM>) or a differential change from the proportional integral controller <NUM>, and (b) based on the appropriate operational regions given the rotor electrical speed (or velocity) and commanded torque, where the operational regions comprise at least the MTPA mode and the FW mode. The equation-based controller <NUM> also determines the estimated torque consistent with the commanded direct-axis current and commanded quadrature-axis current, the operational mode (e.g., MTPA mode or FW mode) and the corresponding operational region or operational point within that operational mode.

<FIG> is a graph of commanded torque <NUM>, estimated torque <NUM>, and final torque <NUM> versus time. The vertical axis indicates torque <NUM>, which can be expressed in Newton-meters (N-m) The horizonal axis indicates time <NUM>. The commanded torque <NUM> is shown in thin dashed lines. The estimated torque <NUM> is illustrated in bold or thick dashed lines. The final torque <NUM> is illustrated in solid line. The progression of the commanded torque <NUM>, estimated torque <NUM> and final torque <NUM> is illustrated from an initialization time <NUM> (which is a start-up after applying electrical energy to the inverter of <FIG> or switching circuit (<NUM>) coupled to the electric motor <NUM>) to a convergence time <NUM>. At the convergence time <NUM>, the commanded torque <NUM> coincides substantially with the final torque output <NUM>, which also agrees with the estimated torque <NUM>. For example, at the convergence time <NUM>, the torque estimation module <NUM> provides an estimated torque (<NUM> or <NUM>) that aligns with, coincides with or equals the commanded torque (<NUM> or <NUM>).

The system of <FIG> is similar to <FIG>, except the torque compensation controller <NUM> of <FIG> is replaced by an outer loop controller <NUM> and the torque estimation module <NUM> is replaced by an outer loop estimator <NUM>. Further, in <FIG>, the estimated torque <NUM> is indicated as optional by the dashed lines. Like reference numbers in <FIG> and <FIG> indicate like elements.

In <FIG>, the outer control loop controller <NUM> comprises one or more of the following: a torque controller (e.g., <NUM>), a speed controller (or velocity controller), and a voltage controller. Accordingly, the outer loop controller <NUM> may be illustrated as containing blocks (composed of dashed lines to indicate their optional nature) that represent the control modules (e.g., software, electronics or both) for the torque controller, speed controller (or velocity controller) and/or a voltage controller.

Meanwhile, to support the outer loop controller <NUM>, the outer control loop estimator <NUM> comprises one or more of the following: (a) a torque estimation module, (b) a speed estimator or velocity estimator, and (c) a control voltage estimator (e.g., to derive such estimates, of torque, velocity and/or voltage, from measurements at the alternating current terminals <NUM> electric machine <NUM>). Accordingly, the outer control loop estimator <NUM> may be illustrated as containing blocks (composed of dashed lines to indicate their optional nature) that represent the control modules (e.g., software, electronics or both) for the torque estimation module, the speed estimator or velocity estimator, and the control voltage estimator.

In one embodiment, a torque estimation module (of the control loop estimator <NUM>) is configured to provide an estimated torque (Tem, such as optional Tem <NUM> indicated by dashed lines) of the rotor shaft of the electric machine <NUM> (e.g., to first summer <NUM>). The torque estimation module (of the control loop estimator <NUM>) may provide the estimated torque to facilitate one or more of the following control modes: (a) a collective torque control and speed control mode that uses the estimated torque and speed error (velocity error), and (b) a collective torque control and voltage control mode that uses estimated torque and voltage feedback error, and (c) a collective torque control, speed control and voltage control mode that uses the estimated torque, speed error (velocity error), and voltage feedback error control.

In one example, speed estimator or velocity estimator (of the control loop estimator <NUM>) is configured to provide, to the outer loop controller <NUM>, a speed error (or velocity error) of the rotor shaft of the electric machine <NUM> based on a difference between observed speed (e.g., observed rotor speed or observed velocity) from the converter and velocity estimator <NUM> and a target speed (e.g. target rotor speed, target rotor velocity, commanded speed, or commanded rotor velocity) of the rotor of the electric machine <NUM>. Further, the outer loop controller <NUM> can use the speed error/velocity error (alone or together with other error estimates, such as the torque error and voltage feedback error) to adjust the final commanded torque (Tfinal*), which represents a speed-adjusted, final commanded torque.

In another example, a control voltage estimator (of the outer control loop estimator <NUM>) is configured to provide, to the outer loop controller <NUM>, a voltage feedback error based on a difference between observed control voltages (e.g., at the respective alternating current terminals <NUM> to the electric machine <NUM> and after conversion or transformation, by converter and velocity estimator <NUM>, to the appropriate stationary and/or rotating d-q voltage axes) and corresponding target control voltages (e.g., commanded control voltages <NUM>, such as Vd* and Vq* available from the current regulator <NUM>). Further, the outer loop controller <NUM> can use the voltage feedback error (alone or together with other error estimates, such as the torque error and speed error or velocity error) to adjust the final commanded torque <NUM> (Tfinal*) to represent a voltage-feedback-adjusted, final commanded torque.

In one embodiment, the outer loop controller <NUM>, or one or more of its constituent control modules, comprise a proportional integral controller. For example, the proportional integral controller can use feedback control in which one signal proportional to the error (e.g., first torque error <NUM> signal, a speed error (or velocity error), and/or a voltage feedback error) is superimposed on a ramp obtained by integrating the corrected output (e.g., final commanded torque <NUM>), where the integral correction increases in response to the magnitude of the error (e.g., first torque error <NUM> signal, a speed error (or velocity error), and/or a voltage feedback error) and the time (e.g., one or more sampling intervals) during which the error persists.

In contrast, in an alternate embodiment, the outer loop controller <NUM>, or one or more of its constituent control modules, use a proportional integral derivative (PID) controller. A PID provides a correction based on proportional control, integral control and derivative control terms, where proportional control of an output parameter (e.g., final commanded torque <NUM>) is proportional to an error (e.g., first torque error <NUM> signal, a speed error (or velocity error), and/or a voltage feedback error) and the derivative control adjusts or dampens the rate of change of the error correction. The output of the outer loop controller <NUM> is capable of communication with a back-EMF adjustment module <NUM> and a second summer <NUM>.

In a speed control mode (or velocity control mode), alone or together with the torque control mode, the outer control loop controller <NUM> can provide the final estimated torque <NUM> of the rotor of the electric machine <NUM> based on the torque error and the speed error (or velocity error). Similarly, in the feedback voltage control mode, alone or together with the torque control mode, the outer control loop controller <NUM> can provide the final estimated torque of the rotor of the electric machine <NUM> based on the torque error and the voltage feedback error. In an aggregate control mode, the outer loop controller can provide the final estimated torque <NUM> of the rotor of the electric machine <NUM> based on any or all of the following: estimated torque error, estimated speed or velocity error, and estimated voltage feedback error.

In an alternate embodiment, the torque estimator (of the outer control loop estimator <NUM>) is deleted, inactive or disabled; hence, no estimated torque <NUM>, Tem, is provided as an input to the first summer <NUM> (as indicated by the dashed line terminating in the arrowhead), or such estimated torque <NUM>, Tem, may be set to zero. There is no, non-zero estimated torque <NUM> to generate the torque error <NUM>, such that the commanded torque <NUM>, T*, appears at the output (labeled torque error <NUM>) of first summer <NUM>. For instance, the commanded torque <NUM>, T* , altogether supports a operator or user input to control the torque of the electric machine <NUM>, without direct torque error (e.g., <NUM>) in the event of speed control, voltage control, or both (e.g., which may indirectly compensate for torque error).

In accordance with one embodiment, upon electrically connecting (e.g., removably, revocably, temporarily or permanently) an electric machine to a controller, a controller is well-suited to operate immediately the electric machine and to estimate direct inductance and quadrature inductance associated with the electric machine based on a first set of equations that assume constant rotor resistance and constant magnetic flux. Further, upon electrically connecting (e.g., removably, revocably, temporarily or permanently) an electric machine to a controller, a controller is well-suited to operate immediately the electric machine and to estimate direct inductance and quadrature inductance associated with the electric machine the without prior characterization, commissioning or testing to establish any reference parameters or look-up tables related to the electric machine. Accordingly, the controller or inverter may be installed or mounted on a vehicle, whereas the electric machine may be installed or mounted on an implement that supports a removable electric connection or coupling (e.g., between two mating parts of an electrical connector).

Even if the manufacturer of the vehicle is different than the manufacturer of the implement, such that technical parameters of the electric machine are not available or previously stored in the data storage device of the controller, the controller is sufficiently compatible with the unknown or uncharacterized machine to operate it until the controller can converge on a final control parameters based on the iterative application of equations that model the corresponding characteristics of the electric machine. The compatibility between the controller/inverter (on a vehicle) and a corresponding electric machine (e.g., on an implement to be mechanically and electrically coupled to the vehicle) can be referred to as the implement "hook-up and go" feature or "plug-and-play" feature.

Further, in the context of heavy equipment, construction equipment, mining equipment, road repair, maintenance and resurfacing equipment, and agricultural equipment, even if the electric machine is characterized or matched to an inverter or motor controller, the alternating current phase cables or conductors that connect the electric machine to the inverter can be different (e.g., longer or have different connectors) than in a lab or test fixture where the characterization or commission was done by a commission. Here, the aforementioned hook-up and go feature or plug and play features supports a self-propelled vehicle (e.g., tractor) with an inverter (e.g., motor controller) that may removably couple to (control) one or more alternating current electric machines on or associated with an implement that is mechanically connected or coupled to the tractor. Accordingly, the coupling between the inverter and the one or more alternating current electric machines may use cables that carry alternating current between the inverter and the one or more alternating current electric machines, where such cables and associated connectors can potentially introduce additional resistance and inductance, or impedance variation, in conjunction with the stator windings.

Claim 1:
An inverter (<NUM>) for controlling an electric machine (<NUM>), the inverter comprising:
a switching circuit (<NUM>) comprising a low-side switch and a high-side switch, the low-side switch and the high-side switching each having a control terminal and two switched terminals;
a driver circuit for providing control signals to the control terminals of the switching circuit;
a pulse width modulation module (<NUM>) for providing pulse-width modulated signals to the electric machine (<NUM>) based on a commanded direct-axis voltage (Vd*) and a commanded quadrature-axis voltage (Vq*);
an electronic data processor (<NUM>);
a data storage device (<NUM>) in communication with the electronic data processor;
a control module (<NUM>) stored in the data storage device, the control module comprising software instructions for execution by the electronic data processor, the control module characterized by:
an inductance estimator (<NUM>) to estimate direct inductance and quadrature inductance associated with the electric machine based on a first set of equations that assume constant rotor resistance and constant magnetic flux, wherein the first set of equations for estimation of the direct inductance, Ld, and quadrature inductance, Lq, comprise the following: <MAT> <MAT> <MAT> <MAT> where:
Ld is direct-axis inductance; Lq is quadrature-axis inductance; vd or Vd is direct-axis voltage; vq or Vq means quadrature-axis voltage; Rs is stator resistance; id or Id is direct-axis current; iq or
Iq is quadrature-axis current; λf iss the back emf constant; and
ωe is the electrical speed of the rotor;
a torque estimator (<NUM>) to estimate an observed torque (Tem) associated with a rotor of the electric machine based on the commanded direct-axis voltage and the commanded quadrature-axis voltage, where the observed torque is proportional to the observed power consumption of the electric machine;
and
a back-electromotive force module (<NUM>) configured to determine a back-electromotive force adjustment (λf) derived from the estimated, observed torque (Tem) and a commanded torque (Tfinal*).