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 motor for driving an airflow generator, said method comprising a speed control step (V) of said motor, said control step comprising an open-loop motor speed control step and a closed-loop motor speed control step, said method comprising a switching step between a first control parameterization (KpOl, KiOl), corresponding to open-loop speed control (V), and a second control parameterization (KpCl, KiCl), corresponding to closed-loop speed control (V). Figure for the abstract: 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 the field of airflow generators for automotive heating, ventilation and / or air conditioning systems, it is known to control the speed of the electric motors used to drive the flow generators by switching from open-loop control to closed-loop control.

[0003] However, it was found that the engine was the source of particularly noticeable noise pollution with this type of control strategy.

[0004] The invention aims to overcome at least in part the previous drawbacks and proposes to this end a method for controlling a brushless DC electric motor, in particular a drive motor for an airflow generator, said method comprising a speed control step for said motor, said control step comprising a motor speed control step in open loop and a motor speed control step in closed loop, said method comprising a switching step between a first control parameterization, corresponding to open loop speed control, and a second control parameterization, corresponding to closed loop speed control.

[0005] Thanks to the invention, a reduction in noise related to motor behavior is observed. Indeed, the applicant observed that the noise generated by this type of cause occurred primarily during the open-loop control phase. Thus, modifying the control parameters in relation to the control modes makes it possible to limit or even eliminate such noise.

[0006] According to various additional features of the invention, which may be taken together or separately and which constitute so many embodiments of the invention:

[0007] - said first and second settings include parameters of one or several units for determining the supply voltage values ​​of said motor,

[0008] - the said unit(s) of determination are configured to calculate said supply voltages by comparison of a reference current with a measured and / or evaluated current,

[0009] - said reference current and / or said measured and / or evaluated current are currents, flux currents, Id and / or torque currents, Iq, obtained in relation to a Park and / or Clarke transformation of stator phase currents of said motor,

[0010] - said parameters include a proportional gain factor and / or a factor of integral gain to be applied to a difference between said reference current and said measured and / or evaluated current,

[0011] - said gain factors exploited in open loop are much lower than the factors of gains exploited in a closed loop,

[0012] - closed-loop operation is performed by comparison to a target speed at an estimated and / or measured speed.

[0013] 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.

[0014] 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.

[0015] 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.

[0016] 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:

[0017] [Fig-1] illustrates, using a flowchart, an example of implementation of the process in accordance with the invention;

[0018] [Fig.2] illustrates, according to a functional diagram, an example of implementation of the process according to the invention.

[0019] 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.

[0020] As illustrated in [Fig. 1], the invention relates to a method for controlling a brushless DC electric motor, in particular a drive motor of an airflow generator. This refers in particular to a drive motor for a blower in a heating, ventilation and / or air conditioning system, for example, in a motor vehicle passenger compartment. A key feature of such an application is that, ideally, the motor should be able to deliver increasing torque with increasing motor speed.

[0021] 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.

[0022] The method includes a step 2 for controlling the speed V of the motor. Advantageously, this speed control step 2 occurs during the starting phase of the motor up to a target speed Vc, which can take various values. For example, the target speed Vc is between 400 and 5,000 revolutions per minute.

[0023] The target speed value Vc is derived, for example, from a step 4 of selecting and / or determining said target speed Vc. In the case of application to an airflow generator of a heating, ventilation and / or air conditioning device, it is, for example, the result of a selection step using a selector device, in particular located on a vehicle control panel. Alternatively, in particular in the case of a regulated heating, ventilation and / or air conditioning device, it is the result of a determination step using a digital control system for said heating, ventilation and / or air conditioning device, in particular based on input information characteristic of ambient temperature and / or humidity conditions as well as a desired temperature and / or a selected operating mode of said heating, ventilation and / or air conditioning device.In each case, the target speed value Vc is preferably chosen from a limited number of values, for example four to eight possible speeds, each corresponding to a given airflow generated by the airflow generator driven by the motor.

[0024] Said step 4 of selecting the target speed Vc is preferably concomitant with a motor start-up. In the embodiments mentioned above, the target speed Vc corresponds, for example, to that associated with the position in which the selector element is located or to that determined by the digital control system of the heating, ventilation and air conditioning device at the time of a engine start-up, in particular when said system is triggered, whether at the time of starting the vehicle or at the command of the driver or a passenger of the vehicle.

[0025] The method further comprises a step 6 of measuring and / or estimating the motor speed V. This step 6 is preferably continued beyond the start-up phase, in particular to ensure that the target speed Vc is maintained and / or to ensure, where applicable, that a new target speed, chosen and / or determined during motor operation, is reached.

[0026] Said step 2 comprises an open-loop motor speed control step 8 and a closed-loop motor speed control step 10. Such a strategy allows, in particular, for a rapid motor start-up thanks to the open-loop control step followed by finer speed adjustment thanks to the closed-loop control step.

[0027] According to the illustrated embodiment, the method according to the invention further comprises a test step 14 located between the open-loop control step 8 and the closed-loop control step 10 to determine the transition from one to the other. Such a transition will take place, for example, at a predefined fixed speed and / or according to other parameters.

[0028] According to the invention, said method comprising a switching step between a first control parameterization, corresponding to open-loop speed control, and a second control parameterization, corresponding to closed-loop speed control.

[0029] Thanks to such a change in control parameterization, a reduction in noise related to motor behavior is observed, in particular its high-frequency speed variations, by using a parameterization specific to each of the open-loop and closed-loop control stages.

[0030] As illustrated in [Fig.2], said first and second parameterizations include, for example, KpOi, KiOi; Kpa, Kia parameters of one or more units 20, 22 for determining supply voltage values ​​of said motor.

[0031] The said unit(s) 20, 22 of determination are configured to calculate said supply voltages by comparison of a reference current with a measured and / or evaluated current.

[0032] In the illustrated embodiment, for a first 20 of said determination units, said reference current and / or said evaluated current are currents, referred to as torque currents, Iq. For a second 22 of said determination units, said reference current and / or said evaluated current are currents, referred to as flux currents, Id. Said torque currents Iq and said flux currents Iq are obtained in relation to a Park and / or Clarke transformation of stator phase currents of said motor, particularly in the context of vector control of said motor.

[0033] The parameters are the same for the first and second determination units 20, 22, whether for open-loop or closed-loop control. Alternatively, and not shown, the parameters are different between the first determination unit 20 and the second transformation unit 22, whether for open-loop and / or closed-loop control.

[0034] Said control parameters include a proportional gain factor KpOi; Kpa and / or an integral gain factor KiOi; Kia to be applied to a difference between said reference current and said measured and / or evaluated current. In other words, here, the proportional gain factor KpOi to be applied during the open-loop control step 8 is different from the proportional gain factor Kpa to be applied during the closed-loop control step. Independently or cumulatively, the integral gain factor KiOi to be applied during the open-loop control step 8 is different from the integral gain factor Kia to be applied during the closed-loop control step.

[0035] The said gain factors exploited in open loop are, for example, much lower than the gain factors exploited in closed loop, in particular by at least a factor of 5, or even 10.

[0036] As will be developed later, closed-loop operation is performed by comparing the target speed Vc to the evaluated and / or measured speed V.

[0037] The invention further relates to a motor speed control device, the motor being designated 100 in [Fig. 2]. The control device is advantageously configured to generate a supply current for the motor. It comprises, 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 has an intensity Ia, Ib, and Ie respectively, from a direct current supplying the inverter 102. The direct current has a voltage Vdc. The three-phase current is configured to generate the rotating magnetic flux of the motor 100.

[0038] As already indicated in connection with the description of the method according to the invention, said device is further configured to perform vector control of said motor 100. For this purpose, it comprises a first unit 104 configured to perform an inverted Clarke transform and / or pulse-width modulation, a second unit 106 configured to perform an inverted Park transform, a torque control unit 108, corresponding to said first determination unit 20, and / or a flow control unit 110, corresponding to said second determination unit 22 mentioned above.

[0039] 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, here presenting a voltage Vq, and a flux current, here presenting a voltage Vd.

[0040] Said torque control unit 108 is configured to define the voltage Vq of the torque current from a difference between a control intensity Iqref and a measured intensity Iqm of said torque current, in particular using a proportional, integral and / or derivative regulator exploiting the gain factors mentioned above.

[0041] Said flow control unit 110 is configured to define 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 exploiting the gain factors mentioned above.

[0042] 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.

[0043] 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.

[0044] 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 and flux current intensities Iq and 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.

[0045] 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.

[0046] 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 reverse 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.

[0047] Moreover, in the application in question, the intensity Idref of the flux current used for control is preferably zero.

[0048] 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 control when there is no feedback on the speed, or even on the angular position of the rotor. This does not, however, preclude a feedback loop using the values ​​of the current intensity Iqm and Idm of the measured and / or estimated torque and flux currents. Conversely, the system is in closed-loop speed control when it operates with feedback on the speed, or even on the angular position of the rotor.

[0049] For switching from one control mode to another, said device here comprises a first and a second rocker unit 120, 122.

[0050] The first flip-flop unit 120 is configured to allow the device to take into account the value of the torque current intensity Iqref from the square wave signal when the open-loop motor control step 8 is active, according to the position marked 01 on the [Fig.2], and to take into account the value of the torque current intensity Iqref from the speed control unit 118 when the closed-loop motor control step 10 is active, according to the position marked Cl on the [Fig.2].

[0051] 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 when the open-loop motor control step 8 is active, according to the position marked 01 on [Fig.2], and to take this value into account when the closed-loop motor control step 10 is active, according to the position marked Cl on [Fig.2],

[0052] The device further includes a third flip-flop unit 128 for modifying the values ​​of the gain factors used by the torque control unit 108 and / or the flow control unit 110. In the position shown 01, the values ​​of the gain factors used will be KpOl and KiOl for open-loop operation. In the position shown Cl, the values ​​of the gain factors used will be KpCl and KiCl for closed-loop operation.

[0053] Said first, second and third toggle units 120, 122, 128 are configured to switch from one control mode to another according to the operating modes, according to the arrows marked 124, 126, 130.

[0054] The invention also relates to a digital management system intended to be embedded in a motor vehicle. This system comprises hardware and / or software components implementing the steps of the control process described above. The hardware and / or software components include, for example, one or more control units equipped with digital processing means, such as one or more microprocessors, optionally integrated into an assembled printed circuit board. Preferably, the control device according to the invention comprises the management system.

Claims

Demands

1. Method of controlling a brushless DC electric motor, in particular a drive motor for an airflow generator, said method comprising a step (2) of controlling a speed (V) of said motor, said control step (2) comprising a step (8) of open-loop motor speed control and a step (10) of closed-loop motor speed control, said method comprising a switching step between a first setting (KpOi, KiOi) of the control, corresponding to open-loop speed control (V), and a second setting (Kpa, KiCi) of the control, corresponding to closed-loop speed control (V).

2. Method according to claim 1 wherein said first and second parameterizations comprise parameters (KpOi, KiOi; Kpa, KiCi) of one or more determination units (20, 22) of voltage values ​​(Vq, Vd) supplying said motor.

3. Method according to the preceding claim wherein said determination unit(s) (20, 22) are configured to calculate said supply voltages (Vq, Vd) by comparison of a reference current (Iqref, Idref) with a measured and / or evaluated current (Iqm, Idm).

4. Method according to the preceding claim wherein said reference current (Iqref, Idref) and / or said measured and / or evaluated current (Iqm, Idm) are currents, said flux, (Id) and / or, said torque (Iq), obtained in relation to a Park and / or Clarke transformation of stator phase currents of said motor.

5. A method according to any one of claims 2 to 4 wherein said parameters include a proportional gain factor (Kpoi, Kpa) and / or an integral gain factor (KiOi, Kia) to be applied to a difference of said reference current (Iqref, Idref) and said current (Iqm, Idm) measured and / or evaluated.

6. A method according to the preceding claim in which said gain factors (KpOi, KiOi) operated in open loop are much lower than the gain factors (Kpa, Kia) operated in closed loop.

7. A method according to any one of the preceding claims, wherein the closed-loop operation is carried out by comparison of a target speed (Vc) to an evaluated and / or measured speed (Vm).

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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