阅读说明：本技术 使用平均同步坐标电流控制ac电机 (Controlling an AC motor using average synchronous coordinate current ) 是由 C.W.塞克雷斯特 于 2020-02-04 设计创作，主要内容包括：一种用于控制动力传动系系统中的电机的方法(其中从动负载连接到所述电机的转子)包括使用连接到所述电机的相绕组的电流传感器在采样周期的起始点处测量相电流。还在前一采样周期的中点处确定单独的相电流。在起始点和前一中点处确定所述转子的角位置,之后使用所述相电流和角位置计算所述电机在所述起始点和前一中点处的同步参考坐标电流。所述方法包括计算所述采样周期内的平均同步参考坐标电流并且使用所述平均值调节所述电机的操作。一种电气系统包括所述电机,功率逆变器模块,以及执行所述方法的控制器。(A method for controlling an electric machine in a powertrain system, wherein a driven load is connected to a rotor of the electric machine, includes measuring phase current at a start point of a sampling period using a current sensor connected to a phase winding of the electric machine. The individual phase currents are also determined at the midpoint of the previous sampling period. The angular position of the rotor is determined at a starting point and a previous midpoint, after which the phase currents and angular position are used to calculate synchronous reference coordinate currents for the motor at the starting point and the previous midpoint. The method includes calculating an average synchronous reference coordinate current over the sampling period and using the average to regulate operation of the motor. An electrical system includes the electric machine, a power inverter module, and a controller that performs the method.)

1. A method for controlling a multi-phase electric machine, the method comprising:

measuring phase currents of the multi-phase motor at a start point of a current sampling period using a set of current sensors;

determining the phase current at a midpoint of a previous sampling period, wherein the previous sampling period occurs immediately prior to the current sampling period;

determining, via a controller, an angular position of a rotor of the multi-phase electric machine at the starting point and the midpoint;

calculating, via the controller, synchronous reference coordinate currents of the multiphase motor at the starting point and the midpoint using the phase currents and the angular positions determined at the starting point and the midpoint;

calculating an average synchronous reference coordinate current over the duration of the current sampling period using the synchronous reference coordinate currents at the start point and the midpoint; and

adjusting torque and/or speed of the multi-phase electric machine via the controller using the average synchronous reference frame current.

2. The method of claim 1, wherein determining the phase current at the midpoint of the previous sampling period comprises measuring the phase current via the set of current sensors.

3. The method of claim 1, wherein determining the phase current at the midpoint of the previous sampling period comprises extrapolating the phase current via the controller.

4. The method of claim 1, wherein calculating the average synchronous reference coordinate current for the duration of the current sampling period comprises determining the average synchronous reference coordinate current for a current or future time instant using a current observer of the controller.

5. The method of claim 4, wherein calculating an average synchronization reference coordinate current over the duration of the previous sampling period comprises extrapolating the average synchronization reference coordinate current for the future time instant using an average synchronization reference coordinate current for the current and/or past time instants, wherein the average synchronization reference coordinate current for the current and/or past time instant is provided by the current observer.

6. The method of claim 5, wherein extrapolating the average synchronous reference coordinate current for the future time instant is accomplished by the controller using linear extrapolation.

7. The method of claim 5, wherein extrapolating the average synchronous reference coordinate current for the future time instant is accomplished by the controller using a second or higher order extrapolation.

8. The method of claim 1, the method further comprising:

determining a difference between the average synchronous reference frame current and the synchronous reference frame current for the current sampling period or the previous sampling period;

processing the difference by a low pass filter to produce a filtered difference; and

adjusting, via the controller, a set of synchronous reference coordinate current commands to the multi-phase motor in real time using the filtered difference.

9. The method of claim 1, wherein the multi-phase electric machine includes a rotor coupled to a set of road wheels of a motor vehicle, and wherein adjusting the torque or speed of the multi-phase electric machine includes controlling a corresponding torque or speed of the set of road wheels.

10. The method of claim 1, further comprising:

recording in the logic of the controller that the synchronous reference coordinate current is shaped as a rectified sine wave between simultaneous samples; and

deriving an average synchronous reference coordinate current over the duration of the current sampling period by solving the following equation:

wherein, I_x,avgIs the average synchronous reference coordinate current, I_x(k)、I_x(k-0.5) and I_x(k-1) is the synchronous reference coordinate current for time (k), (k-0.5), and (k-1), and wherein time (k) is the current sample, time (k-0.5) is the midpoint sample, and (k-1) is the previous sample.

Technical Field

Electric machines (e.g., traction motors or motor/generator units) are used in various powertrain systems to generate and transmit motor torque to a driven load. In some configurations, permanent magnets are attached to or disposed within laminations of the rotor, surrounded by the stator, and coupled to a driven load. The electromagnet is formed by a wound length of copper wire or strip conductor in individual slots of the stator so that the stator windings, when energized by a power source, will generate an electromagnetic field with alternating polarity.

Background

The resultant push-pull force of the interacting rotor and stator fields causes the rotor to rotate about its axis, which ultimately powers a driven load coupled to the rotor, e.g., via a set of intermediate planetary gear sets. The identity of the driven load varies with the intended application of the motor. Common electrically driven loads include, for example, road wheels or drive belts of motor vehicles, as well as drive shafts, conveyor systems, and elevators, where the torque and speed of the motor is varied in an application specific manner for these and other exemplary driven loads.

A proportional-integral controller may be used to regulate the output torque and speed of the motor. Machine control is typically implemented using independent current control loops for a synchronous reference coordinate (frame) defined by a direct axis (d-axis) and a quadrature axis (q-axis). As used in the art of motor control, the d-axis current and voltage are specific control parameters that are purposefully varied in real time to adjust the level of magnetizing flux in the stator, while the q-axis current and voltage are independently controlled to adjust the output torque and/or speed of the motor.

The synchronous reference coordinate axes (collectively referred to as dq axes) described above form a continuous rotation reference coordinate for machine control. In existing motor control schemes, the control effect of continuous coordinate rotation is typically ignored. However, the synchronous reference coordinate currents (i.e., the d-axis and q-axis currents described above) are not constant for the entire duration of a given sampling period. The lack of constancy may lead to errors in the estimation of real-time machine parameters, or errors in the characteristics of such parameters, particularly in the field of flux linkage, ac resistance and core loss estimation. These types of errors may ultimately result in torque producing errors and other undesirable effects.

Disclosure of Invention

As described herein, the methods and accompanying systems of the present disclosure are directed to helping to avoid undesirable performance degradation in the overall control of circuits having electric machines, particularly multi-phase/Alternating Current (AC) electric machines. In addition to the motor, the circuit may also include a multi-cell Direct Current (DC) battery pack, a Power Inverter Module (PIM) connecting the motor to the DC battery pack, and a controller. The disclosed method is implemented as a computer-executable algorithm for calculating and controlling the average synchronous coordinate current (i.e., d-axis and q-axis currents) of the motor in real time for a given sampling period, which may correspond to the Pulse Width Modulation (PWM) interval of the PIM.

Generally, the method samples the individual phase currents of the motor twice per sampling period (including intermediate samples) and extrapolates the intermediate sample positions of the synchronous reference coordinates. The sampled values and extrapolated intermediate sampled positions are then used to calculate or otherwise determine an average synchronous coordinate current of the motor. Thereafter, controlling the average synchronous reference current to regulate torque and/or speed operation of the electric machine may include controlling operation of a powertrain system in which the circuit is employed.

Particular embodiments of a method for controlling a multi-phase electric machine include: measuring phase current of the motor at a start point of a current sampling period using a set of current sensors; and also determines the phase current at the midpoint of the previous sampling period. As used herein, the term "previous sampling period" describes a sampling period that occurs immediately prior to the current sampling period. The method comprises the following steps: determining, via a controller, a position of a synchronous reference coordinate of the motor at the starting point and the midpoint. The phase current and the synchronous reference coordinate position are then used to calculate, via the controller, a synchronous reference coordinate current of the motor at the starting point and the midpoint. Thereafter, the method continues by calculating the average synchronous reference coordinate current for the duration of the current sampling period using current and midpoint synchronous reference coordinate currents. As part of the disclosed exemplary embodiments, the method may include adjusting torque and/or speed of the electric machine via the controller using the calculated average synchronous reference frame current.

Determining the phase current at the midpoint of the previous sampling period may include measuring the phase current via a current sensor or extrapolating the phase current via the controller.

Calculating the average synchronous reference coordinate current for the duration of the current sampling period may include determining an average synchronous reference coordinate current for a current or future time instant using a current observer of the controller. In this embodiment, calculating an average synchronization reference coordinate current may include extrapolating the average synchronization reference coordinate current for the future time instant using the average synchronization reference coordinate current for the current and/or past time instants. Extrapolating the average synchronous reference coordinate current for the future time instant may be accomplished by a controller using linear extrapolation or via second or higher order extrapolation.

In some embodiments, the method may comprise: determining a difference between an average synchronous reference coordinate current and an instantaneously sampled synchronous coordinate current for the current sampling period or the previous sampling period; processing the difference by a low pass filter to produce a filtered difference; and adjusting a set of synchronous reference coordinate current commands to the motor in real time via the controller using the filtered difference.

The electric machine may have a rotor coupled to a road wheel of the motor vehicle. In this embodiment, adjusting the torque or speed of the electric machine includes controlling a corresponding torque or speed of the road wheels.

In some configurations, the controller may record or assume in logic that the synchronous reference frame current is shaped as a rectified sine wave between simultaneous samples. Calculating the average synchronous reference frame current over the duration of the present sampling period may then comprise solving the following equation:

wherein, I_x,avgIs the average synchronous reference coordinate current, I_x(k)、I_x(k-0.5) and I_x(k-1) is the synchronous reference coordinate current for time (k), (k-0.5), and (k-1), and where time (k) is the current sample, time (k-0.5) is the midpoint sample,and (k-1) is the previous sample.

Also disclosed herein is an electrical system having an Alternating Current (AC) multi-phase electric machine with phase windings and a rotor. The electrical system also includes a Power Inverter Module (PIM) connected to the battery pack and the phase windings and configured to output an AC voltage to the phase windings in response to a pulse width modulated signal to charge the multi-phase electric machine. The current sensor measures a phase current of the motor. In this embodiment, the controller receives the measured phase current from the current sensor at a start point of a current sampling period and determines the phase current at a midpoint of a previous sampling period, wherein the previous sampling period occurred immediately prior to the current sampling period.

The controller also determines a synchronization reference coordinate position at the start point and the midpoint, calculates a synchronization reference coordinate current of the motor at the start point and the midpoint using the measured phase currents and the synchronization reference coordinate position, and calculates an average synchronization reference coordinate current for the duration of the current sampling period using the synchronization reference coordinate currents at the start point and the midpoint. Thereafter, the controller uses the average synchronous reference frame current to regulate operation of the motor.

The above summary is not intended to represent each possible embodiment or every aspect of the present disclosure. Rather, the foregoing summary is intended to exemplify some of the novel aspects and features disclosed herein. The above features and advantages and other features and advantages of the present disclosure are readily apparent from the following detailed description of the representative embodiments and modes for carrying out the present disclosure when taken in connection with the accompanying drawings and appended claims.

The following technical scheme is also included in the text.

Technical solution 1. a method for controlling a multiphase motor, the method comprising:

measuring phase currents of the multi-phase motor at a start point of a current sampling period using a set of current sensors;

determining the phase current at a midpoint of a previous sampling period, wherein the previous sampling period occurs immediately prior to the current sampling period;

determining, via a controller, an angular position of a rotor of the multi-phase electric machine at the starting point and the midpoint;

calculating, via the controller, synchronous reference coordinate currents of the multiphase motor at the starting point and the midpoint using the phase currents and the angular positions determined at the starting point and the midpoint;

calculating an average synchronous reference coordinate current over the duration of the current sampling period using the synchronous reference coordinate currents at the start point and the midpoint; and

adjusting torque and/or speed of the multi-phase electric machine via the controller using the average synchronous reference frame current.

Solution 2. the method of solution 1, wherein determining the phase current at the midpoint of the previous sampling period includes measuring the phase current via the set of current sensors.

Solution 3. the method of solution 1, wherein determining the phase current at the midpoint of the previous sampling period includes extrapolating the phase current via the controller.

Solution 4. the method of solution 1 wherein calculating the average synchronous reference coordinate current for the duration of the current sampling period includes determining the average synchronous reference coordinate current at the current or future time instant using a current observer of the controller.

Technical solution 5. the method of claim 4, wherein calculating an average synchronization reference coordinate current for the duration of the previous sampling period comprises extrapolating the average synchronization reference coordinate current for the future time instant using an average synchronization reference coordinate current for the present and/or past time instants, wherein the average synchronization reference coordinate current for the present and/or past time instants is provided by the current observer.

Solution 6. the method of solution 5 wherein extrapolating the average synchronous reference frame current at the future time is accomplished by the controller using linear extrapolation.

Solution 7. the method of solution 5 wherein extrapolating the average synchronous reference coordinate current at the future time is accomplished by the controller using a second or higher order extrapolation.

Technical solution 8 the method according to technical solution 1, further comprising:

determining a difference between the average synchronous reference frame current and the synchronous reference frame current for the current sampling period or the previous sampling period;

processing the difference by a low pass filter to produce a filtered difference; and

adjusting, via the controller, a set of synchronous reference coordinate current commands to the multi-phase motor in real time using the filtered difference.

Solution 9. the method of solution 1, wherein the multi-phase electric machine includes a rotor coupled to a set of road wheels of a motor vehicle, and wherein adjusting the torque or speed of the multi-phase electric machine includes controlling a corresponding torque or speed of the set of road wheels.

Solution 10. the method according to solution 1, further comprising:

recording in the logic of the controller that the synchronous reference coordinate current is shaped as a rectified sine wave between simultaneous samples; and

deriving an average synchronous reference coordinate current over the duration of the current sampling period by solving the following equation:

wherein, I_x,avgIs the average synchronous reference coordinate current, I_x(k)、I_x(k-0.5) and I_x(k-1) is the synchronous reference coordinate current for time (k), (k-0.5), and (k-1), and wherein time (k) is the current sample, time (k-0.5) is the midpoint sample, and (k-1) is the previous sampleAnd (6) sampling.

An electrical system according to claim 11, comprising:

an Alternating Current (AC) multi-phase electric machine having phase windings and a rotor;

a battery pack;

a Power Inverter Module (PIM) connected to the battery pack and the phase windings and configured to output an AC voltage to the phase windings in response to a Pulse Width Modulation (PWM) signal to charge the multi-phase electric machine;

a set of current sensors connected to the phase windings and operable to measure phase currents of the multi-phase motor; and

a controller configured to:

receiving the measured phase current from the set of current sensors at a start point of a current sampling period;

determining a phase current at a midpoint of a previous sampling period, wherein the previous sampling period occurs immediately prior to the current sampling period;

determining an angular position of the rotor at the starting point and the midpoint;

calculating a synchronous reference coordinate current of the multi-phase motor at the starting point and the midpoint using the measured phase currents and using the angular position of the rotor;

calculating an average synchronous reference coordinate current over the duration of the current sampling period using the synchronous reference coordinate currents at the start point and the midpoint; and

adjusting operation of the multi-phase electric machine using the average synchronous reference frame current.

The electrical system of claim 12, wherein the controller is configured to determine the phase current at the midpoint of the previous sampling period by measuring the phase current via the set of current sensors.

The electrical system of claim 11, wherein the controller is configured to determine the phase current at the midpoint by extrapolating the phase current.

Technical solution 14 the electrical system of claim 11, wherein the controller is configured to calculate the average synchronous reference coordinate current for the duration of the current sampling period by determining an average synchronous reference coordinate current at a current or future time using a current observer.

Claim 15 the electrical system of claim 14, wherein the controller is configured to calculate the average synchronous reference coordinate current for the duration of the current sampling period by extrapolating an average synchronous reference coordinate current for a current and/or past time using a current observer.

The electrical system of claim 15, wherein the controller is configured to extrapolate the average synchronous reference coordinate current at a future time using linear extrapolation.

The electrical system of claim 15, wherein the controller is configured to extrapolate the average synchronous reference coordinate current at the future time using a second or higher order extrapolation.

The electrical system of claim 15, wherein the controller is configured to:

determining a difference between the average synchronous reference coordinate current and a synchronous coordinate current for the current sampling period or the previous sampling period;

processing the difference by a low pass filter to produce a filtered difference; and

adjusting a synchronous reference coordinate current command to the motor in real time using the filtered difference.

The electrical system of claim 11, wherein the rotor is coupled to a set of road wheels of a motor vehicle, and the controller is configured to regulate operation of the multi-phase electric machine using the average synchronous reference coordinate current by varying at least one of a torque and a speed of the multi-phase electric machine.

Technical solution 20 the electrical system of claim 11, wherein the controller is configured to assume that the synchronous reference frame current is shaped as a rectified sine wave between the current sampling period and the previous sampling period, and calculate the average synchronous reference frame current over the duration of the current sampling period by solving the following equation:

wherein, I_x,avgIs the average synchronous reference coordinate current, I_x(k)、I_x(k-0.5) and I_x(k-1) is the synchronous reference coordinate current for time (k), (k-0.5), and (k-1), and wherein time (k) is the current sample, time (k-0.5) is the midpoint sample, and (k-1) is the previous sample.

Drawings

Fig. 1 is a schematic illustration of an exemplary powertrain system having a circuit including an electric machine and a controller, wherein the controller is configured to sample and control an average synchronous coordinate current of the electric machine in accordance with the present method.

Fig. 2A and 2B are schematic illustrations of analog voltage errors and current sampling errors, respectively, corrected using the disclosed method.

FIG. 3 is a plot of the present method for calculating the average synchronous coordinate current.

Fig. 4 is a flow chart describing an exemplary embodiment of the present method.

Fig. 5 and 6 are schematic control diagrams of possible embodiments of a method in the control logic of the controller shown in fig. 1.

The present disclosure is susceptible to various modifications and alternative forms, and some representative embodiments have been shown by way of example in the drawings and will be described in detail herein. The novel aspects of this disclosure, however, are not limited to the specific forms shown in the drawings. Rather, the present disclosure is to cover modifications, equivalents, combinations, and/or alternatives falling within the scope of the present disclosure as defined by the appended claims.

Detailed Description

Referring to the drawings, wherein like reference numbers refer to the same or similar components throughout the several views, an exemplary powertrain system 10 includes a powertrain having an electric machine (M)_E) 12, and an electrical system 35. The electric machine 12 is depicted as an electric traction motor of an exemplary motor vehicle 24, and will be described hereinafter in this context for illustrative consistency. However, the motor 12 may be used in a variety of applications, including rail vehicles/trains, aircraft, marine vessels, mobile platforms or robotic systems, as well as stationary power stations, elevators or drive systems. Regardless of the particular system in which the motor 12 is ultimately put into beneficial use, the output torque and speed of the motor 12 are controlled via the method 100, wherein code implementing the method 100 may be executed in real-time via the proportional-integral controller (C) 50.

As will be described in detail below with reference to fig. 2A-6, the controller 50 is configured to calculate and control an average synchronous reference coordinate (stator) current of the motor 12, i.e., the d-axis and q-axis stator currents described above, wherein the controller 50 performs this operation during a calibrated sampling period. The sampling period may coincide with the duration of a Pulse Width Modulation (PWM) interval used to control the motor 12 via a connected Power Inverter Module (PIM) 16.

In performing the method 100, the controller 50 automatically samples/measures individual phase currents of the motor 12, wherein in the exemplary three-phase embodiment of the motor 12, three measured phase currents I_a、I_bAnd I_cShown in fig. 1. Current sensors (S) located on or relative to at least two of the three exemplary phase legs_X) Measuring phase current (I)_a、I_bAnd I_c) Wherein in this example, a pair of current sensors (S)_X) Possibly for measuring two of the three phase currents, wherein the controller 50 calculates the third phase current.

As used herein, a given sampling period has a starting point that coincides with the end point of the immediately preceding sampling period. The controller 50 samples the phase current twice per calibrated sampling period. In the middle of each sampling period, the controller 50The synchronous reference coordinate position is sampled or extrapolated. Depending on the configuration of the motor 12, the synchronous reference coordinate position may or may not be associated with the angular position of the rotor 19 of the motor 12. For example, for an induction motor, the synchronous reference coordinate position is not associated with the position of the rotor, whereas for a permanent magnet motor, the angular position of the rotor and the synchronous coordinate position may coincide. Position sensor (S) may be used_P) (e.g., a rotary encoder or other suitable sensor) to measure the angular position of the rotor 19 as a set of input signals (arrow CC)_I) Wherein the controller 50 converts the angular position to a synchronous reference coordinate position as used herein. Between the above-described sampling or extrapolation of the synchronous reference coordinate position, the controller 50 derives and then controls the average synchronous coordinate current, wherein this control action occurs instead of controlling the instantaneously sampled synchronous coordinate current.

In the exemplary powertrain system 10 shown in fig. 1, an optional internal combustion engine (E) 17 has a set of engine cylinders 17C, e.g., four, six, eight, or more cylinders 17C. Reciprocating pistons (not shown) are disposed within the engine cylinders 17C, wherein the fuel combustion process ultimately generates an engine torque (arrow T) that is fed into the powertrain system 10_E). Engine torque (arrow T)_E) Can cross the input clutch (C)_I) (e.g., a rotating clutch or a hydrodynamic torque converter assembly) to an input member 21 of the transmission (T) 20. In the illustrated exemplary embodiment of the motor vehicle 24, the output member 121 of the transmission 20 outputs a transmission output torque (arrow T)_O) To one or more driven axles 22, wherein the driven axles 22 are coupled to a set of drive wheels 14, or in other applications of the motor, to another driven load, in the non-limiting exemplary embodiment of fig. 1.

Within powertrain system 10, electrical system 35 further includes a propulsion battery pack (B)_HV) 15. The battery pack 15 may be implemented as a multi-cell Direct Current (DC) power supply, where the subscript "HV" in fig. 1 indicates "high voltage", i.e., a voltage level sufficient to charge the motor 12 to a sufficient level to rotate the rotor 19. The battery pack 15 is supplied with a high-voltage DC voltageThe plus (+) and minus (-) bus rails of line 11 are electrically connected to the PIM16 described above. The PIM16 may be controlled using a PWM voltage control signal from the controller 50 or another control unit to output an alternating voltage (V) via a corresponding high voltage AC voltage bus 111_AC)。

The individual phase leads or windings of the electric machine 12 are energized via the AC voltage bus 111 to generate a motor output torque (arrow T)_M）. Motor output torque (arrow T)_M) Alone or in combination with engine torque (arrow T)_E) Together transmitted to the transmission 20 via the rotor 19 to provide input torque (arrow T) to the transmission 20_I). An Auxiliary Power Module (APM)25 in the form of a DC-DC converter may be connected to the high voltage bus 11 and configured to selectively output a low/auxiliary voltage via an auxiliary voltage bus 13. Auxiliary battery (B)_AUX) 26 (e.g., a 12V lead-acid battery) may be connected to the auxiliary voltage bus 13 and configured to act as an auxiliary power source within the powertrain system 10.

To implement the method 100 as described below, the controller 50 is programmed to receive an input signal (arrow CC) from the powertrain system 10 in real time (arrow CC)_I) Wherein the controller 50 is equipped with a processor (P) and a sufficient amount and type of memory (M). The memory (M) may comprise a tangible non-transitory memory, e.g. a read-only optical, magnetic and/or flash memory or the like. The controller 50 also includes a sufficient amount of random access memory, electrically erasable programmable read only memory, and the like, as well as high speed clocks and counters, analog-to-digital and digital-to-analog circuitry, and input/output circuitry and devices, because the method 100 enables the controller 50 to automatically generate and transmit output signals (arrow CC)_O) To the powertrain system 10 and/or the circuit 35 to control operation of the powertrain system 10 and/or the electric machine 12 as desired, wherein in some embodiments, a signal (arrow CC) is output_O) Also including the PWM control signal described above.

FIGS. 2A and 2B correspond to simulations of a current regulated system in which d-axis and q-axis currents are commanded to zero, i.e., I_d*= I_q0. In this case, the q-axis voltage command, shown as trace 30, calculated by controller 50Order (V)_qX) should be equal to back emfWhereinRepresented by trace 32. Furthermore, it is possible to provide a liquid crystal display device,represents the permanent magnet flux in the motor 12, andis the rotation speed of the synchronous reference coordinates. However, within a given calibrated sampling period, the average current is not actually zero, as shown in fig. 2B. Therefore, the current regulator 54 (see fig. 5 and 6) compensates for the current sampling error, and applies the correction voltage. In other words, the current sampling error appears as a disturbance to the current regulator 54.

To illustrate this possible error, a representative voltage difference (Δ V) is shown in FIG. 2A between traces 30 and 32, with voltage (V) depicted on the vertical axis. Time (t) is depicted in milliseconds, with the indicated time scales and amplitudes of fig. 2A and 2B being illustrative and non-limiting. The cause of this error is depicted in FIG. 2B, which depicts the q-axis current (I) in amperes (A)_q) Shown as trace 34 and converts d-axis current (I)_d) Shown as trace 36. For example, the value collected by the analog-to-digital control logic of controller 50 at discrete sampling point 38 at the intersection of traces 34 and 36 corresponds to zero in the synchronous coordinate at the sampling instant. However, the sampled values do not reflect the average synchronous coordinate current over the entire sampling period between successive sampled points 38. The method 100 is directed to solving this problem in the powertrain system 10 of fig. 1 or other systems using the electric machine 12.

Referring to fig. 3 and 4, the present method 100 has the shape of a rectified sine wave between successive samples by recording or assuming in the logic of the controller 50 both synchronous reference frame currents. Upon initialization (, the controller 50 proceeds to step S102 of fig. 4, and uses what is shown in fig. 1Current sensor (S) of the display_X) The individual phase currents of the motor 12 are sampled/measured. In the exemplary three-phase embodiment of the electric machine 12 of FIG. 1, for example, phase currents (I) are collected_a、I_bAnd I_c). Controller 50 may perform this operation within a calibrated sampling interval (k), where (k) is the current point in time, and also at the midpoint of the sampling interval (k-0.5), where (k) is nominally equal to 1 for simplicity of illustration, and "0.5" means half of the sampling interval, regardless of its actual duration.

Meanwhile, in step S103 of fig. 4, the controller 50 may use a position sensor (S)_P) To measure or sample the angular position of the rotor 19 and may then be converted to a synchronous reference coordinate position (theta)_e). When the motor 21 is a permanent magnet motor, step S103 may entail measuring the angular position (θ) of the rotor 19_r) Multiplied by the number of pole pairs (N) of the motor 21, i.e.:

when motor 21 is an induction motor, the conversion may include solving the following equations:

whereinIs the mechanical speed of the rotor 19 multiplied by the number of pole pairs, Rr is the resistance of the rotor 19, L_ratIs the inductance ratio, i.e. the ratio of the magnetizing inductance to the rotor inductance, i_qsIs a d-axis current, andis the d-axis rotor flux. Synchronizing coordinate positionsFrom synchronous speedIs determined.

The controller 50 also samples or estimates the synchronous reference coordinate position θ (k-0.5) at the midpoint of the sampling interval, where "k-0.5" represents this midpoint. Thus, controller 50 determines θ (k) and θ (k-0.5). For example, the latter value may be extrapolated by the controller 50 based on a measured or calculated rotational speed of the rotor 19 and one or more previously collected angular values. The controller 50 temporarily saves the results of steps S102 and S103, and proceeds to step S104.

At step S104 of fig. 4, the controller 50 calculates the synchronous reference coordinate current at the present time (k) (i.e., the start point of the present sampling period) and also at the midpoint (k-0.5) of the immediately preceding sampling period. Such values correspond to the synchronous coordinate current I in FIG. 3_x(k) And I_x(k-0.5) points 42 and 44, where the d and q axes are simply represented in FIG. 3 using the subscript "x", i.e., method 100 is performed for both axes. Since the process is continuous, the controller 50 of FIG. 1 has a buffer of past values in its memory (M) with the immediately preceding sampling period I_xThe synchronous reference coordinate current of (k-1) is also shown as point 46 in FIG. 3.

Step S106 of FIG. 4 includes calculating the average current, i.e., I, for the synchronous reference coordinates (both d-axis and q-axis)_x,avg. To this end, the controller 50 may optionally use the following equation:

wherein the obtained value I_x,avgIs shown in FIG. 3, and I_x,pk1Shown as point 48.

Fig. 5 and 6 depict a possible implementation of the method 100 in the control logic of the controller 50. In fig. 5, the exemplary control logic 50L is used to command (T) motor torque for the electric machine 12_m) Fed into a current command generation (I-GEN) logic block 52. The output of the logic block 52 (i.e., the commanded dq-axis synchronous coordinate current (I;)_dq) Along with other values) are fed into a current regulator (I-REG) 54, as disclosed below. The current regulator block 54 will eventually take the required voltage (V ×)_dq) The output is to the PWM strategy logic block 55, which PWM strategy logic block 55 in turn provides a PWM voltage signal (D) to the PIM 16.

As described above with reference to FIG. 1, the PIM16 receives a DC voltage (arrow Vdc) from the battery pack 15 and will isolate a phase current (I)_a、I_bAnd I_c) Output to the motor 12. Position sensor (S)_P) Measuring the angular position (θ) of the motor 12 (i.e., its rotor 19)_r) (see fig. 1) and feeds this measurement into the conversion block 23. The conversion block 23 outputs the above-mentioned synchronous reference coordinate position (θ)_e). Current sensors (S) disposed on at least two of the three exemplary phase legs_X) Measuring phase current (I)_a、I_bAnd I_c) Wherein in this example, two current sensors (S)_X) Possibly for measuring two of the three phase currents and the controller 50 calculates the remaining phase currents. Each half sample (T) of the controller 50_s/2) transmit the measurement results to the computation logic block 56, where (T)_s) Is the calibrated sampling period time. The computation logic block 56 will sample the phase current (I)_a、I_b、I_c) Converted into corresponding d-axis and q-axis average currents, i.e. I_d,avg(k-1) and I_q,avg(k-1). Thus, the logic block 56 generally corresponds to fig. 4. The current observer (I-OBS) 57 is then used to derive the average synchronous coordinate current for the current point in time (k), i.e. I_dq,avg(k)。

I_dq,avg(k) May be transmitted to the current regulator 54 as an input thereto, wherein the use of the current observer 57 eliminates the delay in the feedback path. That is, absent the current observer 57, the average current in the previous sampling period is used to introduce an additional sampling period delay in the current regulator feedback loop that is eliminated using the current observer 57. Ideally, however, the controller 50 is provided with an average synchronous coordinate current (i.e., I) at a future point in time (k +1) of the immediately following sample_dq,avg(k + 1)) as a reverseFed so as to counteract the inherent delay present in the PWM block 55.

Optionally, a current extrapolation block (I-EXT) 58 may be placed between the current regulator 54 and the current observer 57 to derive an average synchronous reference current for a future point in time (k +1), i.e., I_dq,avg(k + 1). The average synchronous reference frame current at the present and/or past time instants is provided by a current observer 57. For example, controller 50 may use linear extrapolation or higher order extrapolation in current extrapolation block 58 to derive a function of I_dq,avg(k) And/or I_dq,avgOne or more of the values of (k-n) (i.e., using I)_dq,avgPast value of) to derive a future value, i.e., I_dq,avg(k +1)。

Fig. 6 depicts an alternative embodiment of control logic 150L, control logic 150L including an optional Low Pass Filter (LPF) block 61 downstream of comparison logic block 59. In this embodiment, the block 56 calculates and outputs each average synchronous coordinate current (i.e., I) over the immediately preceding or previous sampling period_dq,avg(k-1)), and also outputs an instantaneously sampled synchronous coordinate current (I)_dq(k) ). Instantaneously sampled synchronous coordinate current I_dq(k) Fed into a current observer 57 and a comparison block 59. In comparison block 59, I is determined_dq(k) And I_dq,avg(k-1), i.e. the current of the instant sample and the average current over the immediately preceding sample, wherein said difference is represented by the arrow Δ I_dqAnd (4) showing. This difference is processed through the LPF block 61 to minimize noise, for example, by allowing the controller 50 to ignore delta values above the calibrated threshold.

The current of the synchronous coordinate is adjusted by the amount (arrow Delta I)_dq) Added to the original current command (arrow I) from the current command generation logic block 52_dq) Wherein the obtained values (arrows I;) are_dq) With synchronous coordinate speed (omega)_e) Together to the current regulator block 54. As will be appreciated, the coordinate velocity (ω) is synchronized_e) Possibly as a synchronous reference coordinate position (theta) from block 23_e) The time derivative of the output (d/dt) is derived. In the exemplary embodiment of fig. 6, the current regulator block 54 continues to control the instantaneous currentFlow, but modify the current generation command to achieve the desired average current. The average current may also be used as a feedback variable for a flux linkage look-up table of the controller 50 and/or for estimating motor torque.

Thus, when implemented in the exemplary powertrain system 10 of fig. 1 or other mobile or stationary system having an AC motor, the method 100 is directed to improving the current estimation technique by sampling phase current and rotor position twice per sampling period (at the end of the period, and again at the midpoint of the same period). In some embodiments, the speed and sampling period information may be used to estimate or extrapolate midpoint sample values. Thus, the method 100 approximates the synchronous reference current as a rectified sine wave within one cycle. Controlling the average current for the last sampling period induces a delay in the current regulator block 54 of fig. 5 and 6, wherein various methods are employed to compensate for the induced delay. These and other benefits will be readily apparent to those of ordinary skill in the art in view of the foregoing disclosure.

While some of the best modes and other embodiments have been described in detail, various alternative designs and embodiments exist for practicing the present teachings as defined in the appended claims. Those skilled in the art will recognize that modifications may be made to the disclosed embodiments without departing from the scope of the present disclosure. Moreover, the present concepts expressly include combinations and subcombinations of the described elements and features. The detailed description and drawings are supportive and descriptive of the present teachings, with the scope of the present teachings being limited only by the claims.