Method and device for controlling a brushless DC electric motor, in particular a drive motor for an airflow generator

Abstract

A method for controlling a brushless DC electric motor, in particular a drive motor for an airflow generator, said method comprising a step for controlling at least one operating parameter of said motor, in particular a speed of said motor, using an intensity and voltage of a flux current (Vd, Id) and a torque current (Vq, Iq), obtained in relation to a Park and / or Clarke transformation, applied to stator phase currents of said motor, said method further comprising a step for controlling a voltage of an electrical energy storage device supplying said motor, called battery voltage (Vbat), said method comprising a step for determining an intensity of a current from said storage device, called battery current (Ibat), said step for determining the intensity of the battery current (Ibat) comprising a calculation step (200) using reference values,including the battery voltage (Vbat) as well as the voltages and currents of the flux (Vd, Id) and torque (Vq, Iq) currents. Figure for the abbreviation: Figure 2,

Description

Title of the invention: Method and device for controlling a brushless DC electric motor, in particular a drive motor for an airflow generator

[0001] The invention relates to a method and device for controlling a brushless DC electric motor, in particular a drive motor for an airflow generator. It also relates to a digital management system, a computer program product, and a data recording medium for implementing said method.

[0002] In this field, it is known to control electric motors driven by a direct current supplied by an electrical energy storage battery. The current delivered by the battery is estimated in order to perform the control. A sufficiently accurate estimate is necessary for effective control. Indeed, otherwise, strategies for intentionally degrading motor performance, for example, strategies for reducing the motor's energy efficiency, particularly through flux degradation, may be induced by an incorrect estimation of the current supplied by the battery, whereas implementing such strategies is unnecessary given the actual value of this current.

[0003] Currently, the estimation of the current supplied by the battery is carried out from various measured and / or evaluated parameters and multidimensional data tables, from experimental design, allowing the value of the current intensity to be deduced from the measured and / or evaluated parameters.

[0004] However, these data tables require the use of large information storage units. Furthermore, their operation requires significant computing power.

[0005] The invention aims to overcome, at least in part, the aforementioned drawbacks and, to this end, proposes a method for controlling a brushless DC electric motor, in particular a motor for driving an airflow generator. This method comprises a step for controlling at least one operating parameter of the motor, in particular a speed of the motor, using the intensity and voltage of a flux current (Vd, Id) and a torque current (Vq, Iq), obtained in relation to a Park and / or Clarke transformation applied to stator phase currents of the motor. The method further comprises a step for controlling the voltage of an electrical energy storage device supplying the motor, referred to as the battery voltage (Vbat). The method also includes a step for determining the intensity of a current from the device. storage, called battery current (Ibat), said step of determining the intensity of the battery current (Ibat) including a calculation step using reference values ​​including the battery voltage (Vbat) as well as the voltages and intensities of the flux currents (Vd, Id) and torque currents (Vq, Iq).

[0006] Thus, thanks to the invention, the battery current is calculated instead of being determined from data tables requiring a large memory capacity and significant computing power. Furthermore, the reference values ​​used to determine the battery current are values ​​already available for operational control, particularly for motor speed and / or electrical energy storage device control.

[0007] According to various additional features of the invention, which may be taken together or separately and which constitute so many embodiments of the invention: - said calculation step uses the following calculation formula:

[0008] (K x (Vd x Id + Vq x Iq)) / Vbat

[0009] where K is a dimensionless coefficient, - the dimensionless coefficient K is approximately 1.5, with currents in Amperes and / or voltages in Volts. - the said battery voltage (Vbat) used in the said calculation formula is a voltage measured across the terminals of the said storage device, - a result from said calculation formula is provided as a value, possibly raw, of the battery current intensity (Ibat), in particular as long as the speed of said motor remains below a given threshold, - said step of determining the battery current intensity (Ibat) includes a step of filtering the result of said calculation formula, - said step of determining the battery current intensity (Ibat) includes a step of using data tables to take into account losses in the determination of the battery current intensity (Ibat), said losses being a function of the speed of said motor, - said data table exploitation step is carried out after said filtering step.

[0010] The invention also relates to a digital management system intended to be embedded in a motor vehicle, said system comprising hardware and / or software elements implementing the steps of the process described above.

[0011] The invention further relates to a computer program product comprising program code instructions recorded on a computer-readable medium to implement the steps of the process described above, when said program is running on a computer.

[0012] The invention also relates to a computer-readable data recording medium on which is recorded a computer program comprising program code instructions for implementing the steps of the process described above.

[0013] The invention will be better understood, and other objects, details, features and advantages thereof will become more apparent in the course of the detailed explanatory description that follows, of at least one embodiment of the invention given by way of purely illustrative and non-limiting example, with reference to the accompanying schematic drawings, among which:

[0014] [Fig-1] illustrates, according to a functional diagram, an example of implementation of the process in accordance with the invention;

[0015] [Fig.2] illustrates, according to a functional diagram, a first example of the implementation of a step for determining the intensity of a current according to the method according to the invention;

[0016] [Fig.3] illustrates, according to a functional diagram, a second example of implementation of the current intensity determination step according to the method according to the invention.

[0017] It should first be noted that the terms "first", "second", "third", ... are used only to distinguish the components concerned from each other and do not imply any order or possible importance of said components.

[0018] As illustrated in [Fig. 1], the invention relates to a method for controlling an electric motor 100. Said electric motor 100 is a brushless DC motor, in particular a drive motor for an airflow generator. Specifically, it is a drive motor for a blower in a heating, ventilation, and / or air conditioning system, for example, in the passenger compartment of a motor vehicle. A particular feature of such an application is that, preferably, said motor must be able to deliver increasing torque with increasing motor speed.

[0019] A brushless DC motor is understood to mean, in particular, an electrical machine comprising a rotor equipped with one or more permanent magnets. This machine further comprises stator windings and enables the commutation of current in said windings so as to create a rotating magnetic flux driving the rotor. It is configured for detecting an angular position of the rotor, preferably to allow orthogonality of a rotor magnetic flux with respect to the stator magnetic flux, as in DC motors, hence its name.

[0020] Said method includes a step of controlling one or more operating parameters of said engine 100. This includes, in particular, a step of controlling a The rotational speed V of said motor. Said control stage uses an intensity and voltage of a flux current Vd, Id and a torque current Vq, Iq, obtained in relation to a Park and / or Clarke transformation, applied to stator phase currents la, Ib, le of said motor. In other words, said motor 100 is subject to vector control, in particular for the purpose of controlling its speed.

[0021] As illustrated, the invention also relates to a digital management system intended to be embedded in a motor vehicle. This system comprises hardware and / or software elements implementing the steps of the control process described above. The hardware and / or software element(s) include, for example, one or more control devices equipped with digital processing means, such as one or more microprocessors, optionally integrated into an assembled printed circuit board.

[0022] The invention further relates to a speed control device V of the motor 100. Preferably, said control device includes said management system.

[0023] The control device is advantageously configured to generate a supply current for the motor. It includes, for this purpose, an inverter 102. The inverter 102 is configured to receive control currents from switches of the inverter 102. These control currents have voltages Va, Vb, and Vc respectively and are used to obtain, at the output of the inverter 102, a three-phase current, each phase of which corresponds to the stator phase currents Ia, Ib, and Ib of the motor 100, from a direct current supplying the inverter 102. The direct current has a voltage Vbat. The three-phase current is configured to generate the rotating magnetic flux of the motor 100.

[0024] Said device is further configured to perform vector control of said motor 100. It includes here for this purpose a first unit 104 configured to perform an inverted Clarke transformation and / or pulse width modulation, a second unit 106 configured to perform an inverted Park transformation, a torque control unit 108 and / or a flux control unit 110.

[0025] Said first transformation unit 104 is configured to convert intermediate current voltages Va and V[3] into each of the control current voltages Va, Vb, Vc. Said second transformation unit 106 is configured to obtain the intermediate current voltages Va and V[3] from the torque current, exhibiting voltage Vq, and from the flux current, exhibiting voltage Vd.

[0026] Said torque control unit 108 is configured to define the voltage Vq of the torque current from a difference between a control current Iqref and a measured current Iqm of said torque current, in particular using a proportional, integral and / or derivative regulator.

[0027] Said flow control unit 110 is configured to set the voltage Vd of the flow current from a difference between a control intensity Idref and a measured intensity Idm of said flow current, in particular using a proportional, integral and / or derivative regulator.

[0028] Said device is configured to operate in open loop and / or closed loop. For example, it is configured to operate in open loop during a motor start-up phase 100 and to switch to closed loop thereafter, once a minimum speed is reached and / or according to various parameters.

[0029] To operate in open-loop speed control, the device is configured to receive control information, for example in the form of a square wave signal representing the intensity Iqref of the torque current to be applied. The value of the square wave is determined, for example, from the characteristics of the motor.

[0030] To operate in closed-loop speed control, said device further includes here a third unit 112 configured to perform a Clarke transformation, a fourth unit 114 configured to perform a Park transformation, a unit 116 for estimating the speed and / or angular position of the rotor of the motor 100 and / or a speed control unit 118.

[0031] Said third transformation unit 112 is configured to convert the current intensities la, Ib, le of the supply current into the intermediate current intensities la and I[3. Said fourth transformation unit 114 is configured to obtain the torque current intensities Iq and flux current intensities Id from the intermediate current intensities la and I[3. Said unit 116 for estimating the speed and / or angular position of the motor rotor 100 is configured to operate from the voltages Va and V[3 as well as the intermediate current intensities la and I[3.

[0032] The speed control unit 118 is configured to deliver a torque current value Iq to be applied to the torque control unit 112 from a difference between the target speed Vc and the speed information Vm delivered by said estimation unit 116.

[0033] It should also be noted that the information relating to the rotor position is used at the level of said second and fourth transformation units 106, 112 of inverted Park and Park. The said intensities of the torque currents Iqm and flux Idm delivered by said fourth transformation unit 114 are thus described as measured and / or estimated.

[0034] Moreover, in the application in question, the intensity Idref of the flux current used for control is preferably zero.

[0035] According to the illustrated embodiment, the concepts of open loop and closed loop should be understood in relation to the speed and / or angular position of the rotor. The system thus operates in open-loop speed control when it receives no feedback on the speed, or even on the angular position of the rotor. This does not, however, preclude a feedback loop using the measured and / or estimated torque and flux current values ​​Iqm and Idm. Conversely, the system operates in closed-loop speed control when it receives feedback on the speed, or even on the angular position of the rotor.

[0036] For switching from one control mode to another, said device here comprises a first and a second rocker unit 120, 122.

[0037] The first flip-flop unit 120 is configured to allow the device to take into account the value of the torque current intensity Iqref during open-loop operation, according to the position marked 01 on the [Fig.l], and to take into account the value of the torque current intensity Iqref coming from the speed control unit 118 during closed-loop operation, according to the position marked Cl on the [Fig.l].

[0038] The second flip-flop unit 122 is configured not to return the value of the rotor position to said second and fourth transformation units 106, 112 during open-loop operation, according to the position marked 01 on [Fig.1], and to take into account this value during closed-loop operation, according to the position marked Cl on [Fig.1].

[0039] Said first and second toggle units 120, 122 are configured to switch from one control mode to another according to the operating modes, according to the arrows marked 124, 126.

[0040] To optimize the motor's operation, it is advantageous to determine the intensity of a current, referred to as battery current Ibat, from an electrical energy storage device (not shown) supplying said motor 100. This battery current Ibat corresponds, according to the embodiment illustrated above, to the direct current supplying the inverter 102, either directly or via a direct current / direct current converter (also not shown). The control method according to the invention thus includes, in this respect, a step for determining said battery current Ibat.

[0041] For this purpose, it includes a step of controlling a voltage of the current coming from said energy storage device, called battery voltage Vbat and corresponding here to the voltage of the direct current supplying the inverter 102.

[0042] As illustrated in Figures 2 and 3, according to the invention, said step of determining the battery current intensity Ibat comprises a calculation step 200 exploiting reference values, including the battery voltage Vbat as well as the voltages and intensities of the flux currents Vd, Id and the torque currents Vq, Iq.

[0043] In this way, the battery current Ibat is calculated instead of being determined from multidimensional data tables requiring a large memory capacity. Moreover, the reference values ​​Vbat, Id, Iq, Vd, Vq used to determine the battery current are values ​​already available within the framework of motor speed control V and / or electrical energy storage device control.

[0044] Said calculation step 200 uses, for example, the following calculation formula:

[0045] (K x ( Vd x Id + Vq x Iq )) / Vbat (F)

[0046] where K is a dimensionless coefficient which is approximately 1.5, the intensities being given, for example, in Amperes and the voltages, for example, in Volts.

[0047] According to one aspect of the invention, said battery voltage Vbat used in said calculation formula (F) is a voltage Vbatnc measured across said storage device. This is, for example, an uncompensated voltage, measured with the highest possible accuracy.

[0048] According to another aspect of the invention, which can be combined with the previous one, a result of said calculation formula (F) is given as the value of the battery current intensity Ibat as long as the speed V of said motor 100 remains below a given threshold, for example a speed of around 3,000 rpm. Beyond this speed threshold, other strategies will then be used.

[0049] According to a first embodiment, the result of the calculation formula (F) is used as the value, for example in Amperes, of the battery current Ibat.

[0050] According to another embodiment, as more particularly illustrated [Fig.2], said step of determining the intensity of the battery current Ibat further includes a step 202 of filtering the result of said calculation formula (F).

[0051] According to this embodiment, calculation step 200 provides a raw result Ibatb, thanks to calculation formula (F), and filtering step is applied to raw result Ibatb to provide a filtered value Ibatf of the battery current Ibat, with Ibatb and Ibatf being given, for example, intensities in Amperes. This embodiment smooths out any fluctuations in the result directly given by calculation (F). In particular, it involves a low-pass filter.

[0052] According to one aspect of the invention, losses are neglected. Such an approach is particularly relevant up to the threshold speed mentioned above.

[0053] Alternatively, as illustrated in [Fig. 3], said step of determining the battery current intensity Ibat further comprises a step 204 of using data tables to take into account losses in determining the intensity of said battery current Ibat, said losses being a function of the speed V of said motor 100. This refers, for example, to one or more one-dimensional tables, and therefore less complex than the multi-dimensional tables used in the state of the art. The speed V of the motor 100 used for the operation of said table(s) is, in particular, the speed Vm delivered by said estimation unit 116 according to the embodiment of the control method according to the invention illustrated in [Fig. 1].

[0054] According to this embodiment, the battery voltage Vbat used as input to the calculation step 200 is possibly said uncompensated battery voltage Vbatnc.

[0055] Said data table operation step 204 is carried out, for example, after said filtering step 202 and is therefore operated on the filtered value Ibatf of the battery current Ibat and the process according to the invention delivers, at the end of said data table operation step 204, a compensated value Ibatc of the battery current Ibat which will be advantageously used for the control of the motor 100.

Claims

Demands

1. A method for controlling a brushless DC electric motor (100), in particular a motor for driving an airflow generator, said method comprising a step of controlling at least one operating parameter of said motor (100), in particular a speed of said motor, exploiting an intensity and a voltage of a flux current (Vd, Id) and a torque current (Vq, Iq), obtained in relation to a Park and / or Clarke transformation, applied to stator phase currents (la, Ib, le) of said motor (100), said method further comprising a step of controlling a voltage of an electrical energy storage device supplying said motor, said battery voltage (Vbat), said method comprising a step of determining an intensity of a current from said storage device, said battery current (Ibat),said step of determining the battery current intensity (Ibat) comprising a calculation step (200) using reference values ​​including the battery voltage (Vbat) as well as the voltages and intensities of the flux currents (Vd, Id) and torque currents (Vq, Iq).

2. Method according to claim 1 wherein said calculation step (200) exploits the following calculation formula (F): (K x ( Vd x Id + Vq x Iq )) / Vbat Where K is a dimensionless coefficient.

3. A method according to any one of the preceding claims wherein said battery voltage (Vbat) used in said calculation formula (F) is a voltage (Vbatnc) measured across said storage device.

4. A method according to any one of the preceding claims wherein a result of said calculation formula (F) is delivered as a value of the battery current intensity (Ibat), possibly gross, in particular as long as the speed of said motor (100) remains below a given threshold.

5. A method according to any one of the preceding claims wherein said step of determining the battery current intensity (Ibat) comprises a step (202) of filtering the result (Ibatb) of said calculation formula (F).

6. A method according to any one of the preceding claims wherein said step of determining the battery current intensity (Ibat) comprises a step (204) of operating data tables enabling the consideration of losses in the determination of the battery current intensity (Ibat), said losses being a function of the speed of said motor (100).

7. A method according to the preceding claim taken in its connection with claim 5 in which said data table exploitation step (204) is carried out after said filtering step (202).

8. A digital management system intended to be embedded in a motor vehicle, said system comprising hardware and / or software elements implementing the steps of the process according to any one of the preceding claims.

9. Product computer program comprising program code instructions recorded on a computer-readable medium to implement the steps of the process according to any one of claims 1 to 7, when said program is run on a computer.

10. A computer-readable data recording medium on which is recorded a computer program comprising program code instructions for implementing the process steps of the process according to any one of claims 1 to 7.

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