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 starting step (2) of said motor, said starting step (2) comprising an initial starting step (8), said initial starting step (8) being carried out by open-loop control of said motor until a threshold temperature (Ts) of the supply current control elements of said motor is reached or exceeded. Figure for the abstract: Figure 1

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 motor for driving an airflow generator, especially in cold weather. 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 by applying a rotation speed setpoint to them and ensuring that this setpoint is reached in a minimum time.

[0003] In cold weather, with such a strategy, the applicant observed that unwanted micro-shutdowns of the engines occur, which lengthens the time to reach the desired speed. In the case of engines used to generate airflow, such as blowers used in heating, ventilation and / or air conditioning (HVAC) systems, this can cause a delay in proper temperature regulation of a passenger compartment and discomfort for the occupants.

[0004] The applicant hypothesized that such micro-stops originated at least in part from electronic motor control devices, in particular from electrical capacitors used in these devices, the performance of these capacitors dropping in cold temperatures.

[0005] A first solution to this problem would be to choose more robust electronic components for motor control. However, these are expensive, which limits their appeal.

[0006] The invention aims to overcome at least in part the previous drawbacks and proposes to this end a method of controlling a brushless DC electric motor, in particular a drive motor for an airflow generator, said method comprising a starting step of said motor, said starting step comprising an initial starting step, said initial starting step being carried out by open-loop control of said motor until a threshold temperature of control elements for supplying currents of said motor is reached or exceeded.

[0007] The use of open-loop motor control generates higher currents and consequently a more rapid heating of the motor control components. This helps to limit the risk of micro-interruptions during startup. Furthermore, this result is achieved without using different electronic components than those employed for operation at more moderate temperatures. It is therefore possible to retain the same printed circuit boards, or at the very least, to continue using electrolytic capacitors for motor control.

[0008] In other words, according to the invention, preferably, said method is implemented using a control element comprising a printed circuit board, assembled, and / or one or more electrolytic capacitors, optionally implanted on said board.

[0009] According to various additional features of the invention, which may be taken together or separately and which constitute so many embodiments of the invention:

[0010] - said threshold temperature is approximately -30°C,

[0011] - said open-loop control is an open-loop speed control,

[0012] - said control elements are configured to operate in open loop at based on the current supply instructions for said motor,

[0013] - said currents are flux currents Id and / or torque currents Iq, obtained in relation with a Park and / or Clarke transformation of stator phase currents of said motor,

[0014] - said control elements include a temperature sensor and said The startup step uses information from said sensor to determine whether said threshold temperature has been reached or exceeded.

[0015] - said method includes a preliminary step of controlling the temperature of said control components, the said initial start-up step occurring if the temperature of the control components is less than or equal to said threshold temperature,

[0016] - said initial start-up step occurs for a maximum time,

[0017] - said initial starting step is intended to power said motor without exceeding maximum current and / or rotational speed values,

[0018] - said start-up step aims to achieve a target rotational speed for said engine,

[0019] - said startup step includes a final startup step aimed at to reach said target speed, said final start-up stage occurring after said initial start-up stage, said final start-up stage including a closed-loop speed control stage to reach said target speed.

[0020] 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.

[0021] 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.

[0022] 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.

[0023] 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:

[0024] [Fig. 1] illustrates, according to a flowchart, an example of implementation of the process according to the invention;

[0025] [Fig.2] illustrates, according to a functional diagram, an example of implementation of the process according to the invention.

[0026] 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.

[0027] As illustrated in [Fig. 1], the invention relates to a method for controlling a brushless DC electric motor, in particular a drive motor for an airflow generator. Specifically, it relates to 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, the motor must be able to deliver increasing torque with increasing motor speed.

[0028] 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.

[0029] The method according to the invention comprises a step 2 of starting said motor preferably up to a target speed Vc which may take different values. Said target speed Vc is, for example, between 400 and 5,000 revolutions per minute.

[0030] 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.

[0031] Said step 4 of selecting the target speed Vc is preferably concomitant with a start of step 2 of starting the engine. In the embodiments mentioned above, the target speed Vc corresponds, for example, to that associated with the position in which the selector member is located or to that determined by the digital control system of the heating, ventilation and air conditioning device at the time of 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.

[0032] The method further advantageously comprises a step 6, parallel to said starting step 2, for measuring and / or estimating the motor speed V. This step 6 is preferably continued beyond the starting step 2, 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.

[0033] According to the invention, said starting step includes an initial starting step 8, said initial starting step 8 being carried out by open loop control of said motor until a threshold temperature Ts of control elements of supply currents of said motor is obtained or exceeded.

[0034] The use of open-loop motor control generates higher currents and consequently a faster heating of the motor control components, which helps to limit the risks of micro-interruptions at start-up.

[0035] As will be detailed below in relation to [Fig.2], said open loop control is here an open loop speed control.

[0036] Said threshold temperature is approximately -30°C. In other words, as long as the control elements of the supply currents of said motor do not have a temperature greater than -30°C, the motor control takes place in open loop, at least until certain limits are reached.

[0037] Said control elements are advantageously configured to operate in open loop based on supply current setpoints for said motor. Said currents are, for example, 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, particularly within the framework of a vector control of said motor.

[0038] Preferably, said control devices include a temperature sensor and said start-up step 2 uses information from said sensor to determine whether said threshold temperature Ts has been reached or exceeded.

[0039] The method advantageously includes a preliminary step 10 for checking a temperature T of said control elements. The initial start-up step 8 then occurs if said temperature T of the control elements is less than or equal to said threshold temperature Ts.

[0040] Such an embodiment is illustrated in [Fig. 1], from which it can be seen that the method according to the invention comprises a test step 12 located upstream of the initial start-up step 8. If the result of the test T < Ts is positive, said initial start-up step is activated. Otherwise, the start-up step comprises a start-up step 16 in a standard mode, for example, a start-up beginning with open-loop speed control followed by closed-loop speed control, the switch from one to the other occurring at a predetermined speed or according to other criteria.

[0041] For safety reasons, said initial starting step 8 advantageously occurs for a maximum duration. Alternatively or cumulatively, said initial starting step 8 is intended to supply said motor without exceeding predetermined maximum current and / or speed values. For speed, this could be, for example, 5,000 rpm.

[0042] Preferably, said start-up step 2 includes a final start-up step 18 aimed at reaching the target rotational speed. Said final start-up step 18 occurs after said initial start-up step 8. Said final start-up step 18 includes, or even consists of, a closed-loop speed control step to reach said target speed. In other words, according to this embodiment, the speed control switches from an open-loop mode to a closed-loop mode once the threshold temperature Ts is reached.

[0043] Such an embodiment is illustrated in [Fig. 1], from which it can be seen that the process according to the invention comprises another test step 20 located between the open-loop control step 8 and the closed-loop control step 18. If the result of the test T < Ts is positive, the process loops back to the initial start-up step 8. If the result of the test T < Ts is negative, the process proceeds to the final start-up step 18.

[0044] The invention also relates to a digital management system intended to be embedded in a motor vehicle. Said system comprises hardware and / or software elements implementing the steps of the control process described above.

[0045] The hardware and / or software component(s) include, for example, the control elements mentioned above. The control element(s) are advantageously equipped with digital processing means, such as one or more microprocessors, optionally integrated into a printed circuit board, and / or one or more electrolytic capacitors, optionally mounted on said board. The temperature sensor of the temperature element(s) used to measure the temperature T in question according to the invention is mounted, for example, on or near said board, or even in close proximity to the electrolytic capacitor(s).

[0046] As illustrated in [Fig. 2], the invention further relates to a motor speed control device, designated 100 in that figure. Preferably, said control device comprises said management system.

[0047] The control device is advantageously configured to generate the supply currents for the motor. It includes an inverter 102 for this purpose. 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.

[0048] 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.

[0049] 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 a current, said to be a couple, presenting a voltage Vq and a current, said to be flux, presenting a voltage Vd.

[0050] 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.

[0051] Said flow control unit 110 is configured to set the voltage Vd of the flow current from a difference between a control current Idref and a measured current Idm of said flow current, in particular using a proportional, integral and / or derivative regulator.

[0052] 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.

[0053] 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.

[0054] 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.

[0055] 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.

[0056] 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.

[0057] Moreover, in the application in question, the intensity Idref of the flux current used for control is preferably zero.

[0058] 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.

[0059] For switching from one control mode to another, said device here comprises a first and a second rocker unit 120, 122.

[0060] 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].

[0061] 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],

[0062] 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.

Claims

Demands

1. Method of controlling a brushless DC electric motor, in particular a drive motor for an airflow generator, said method comprising a starting step (2) of said motor, said starting step (2) comprising an initial starting step (8), said initial starting step (8) being carried out by open-loop control of said motor until a threshold temperature (Ts) of control elements for the supply currents of said motor is reached or exceeded.

2. Method according to claim 1 wherein said threshold temperature (Ts) is about -30°C.

3. A method according to any one of the preceding claims wherein said open-loop control is an open-loop speed control.

4. A method according to any one of the preceding claims wherein said control elements comprise a printed circuit board, assembled, and / or one or more electrolytic capacitors.

5. A method according to any one of the preceding claims wherein said control members include a temperature sensor and said start-up step uses information from said sensor to determine whether said threshold temperature (Ts) has been reached or exceeded.

6. A method according to any one of the preceding claims comprising a preliminary step (12) of checking a temperature of said control elements, said initial start-up step (8) occurring if the temperature (T) of the control elements is less than or equal to said threshold temperature (Ts).

7. A method according to any one of the preceding claims wherein said starting step (2) is aimed at achieving a target rotational speed (Vc) for said motor, said starting step (2) comprising a final starting step (18) aimed at achieving said target speed (Vc), said final starting step (18) occurring after said initial starting step (8), said final starting step (18) comprising a closed-loop speed control step to achieve said target speed (Vc).

8. A digital management system intended to be embedded in a motor vehicle, said system comprising elements hardware and / or software 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.