Method for controlling the starting of an electric motor, in particular a drive motor for an airflow generator

Abstract

A method for controlling the starting of an electric motor, in particular a drive motor for an airflow generator, said method comprising successively a first step (1) of accelerating said motor, according to a first acceleration rate (K1), and a second step of accelerating said motor, according to a second acceleration rate (K2), lower than the first acceleration rate (K1), said first and second steps (1, 2) being activated at least when an ambient temperature is below a threshold, referred to as cold ambient conditions. Figure for the abstract: Figure 1

Description

Title of the invention: Method for controlling the starting of an electric motor, in particular a drive motor for an airflow generator

[0001] The invention relates to a method for controlling the starting of an electric motor, in particular a drive motor for 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 for controlling the start-up of an electric motor, in particular a drive motor for an airflow generator, said method comprising successively a first stage of acceleration of said motor, according to a first rate of acceleration, and a second stage of acceleration of said motor, according to a second rate of acceleration, lower than the first rate of acceleration, said first and second stages being activated at least when an ambient temperature is below a threshold, said cold ambient conditions.

[0007] According to the applicant's findings, starting with a high acceleration rate and then switching to a lower acceleration rate subsequently allows to limit the risk of unwanted motor shutdowns while maintaining a relatively short start-up time, even in cold ambient temperatures. This is achieved without using different electronic components than those used for operation in warmer 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 an assembled printed circuit board and / or one or more electrolytic capacitors, optionally mounted on said board. Said control element is advantageously configured to deliver a direct current, having a stabilized voltage, used to power switches employed to generate the current supplying the motor.

[0009] Preferably, taking into account the applications intended, said motor delivers increasing torque with an increase in the rotational speed of said motor.

[0010] According to various additional features of the invention, which may be taken together or separately and which constitute so many embodiments of the invention: - the first step is applied until a certain speed, called the pivot speed, of motor rotation is obtained, - said second acceleration stage is applied from said pivot velocity, - said process includes a step of controlling the ambient temperature, - the said ambient temperature control step takes place before the said first step, - said threshold for cold ambient conditions is -30° Celsius, - said pivot rotation speed is between 1,500 and 2,500 revolutions per minute, particularly between 1,700 and 2,300 revolutions per minute, - said first acceleration rate is between 500 and 1,000 revolutions per minute per second, in particular between 750 and 850 revolutions per minute per second, - said second acceleration rate is less than 200 revolutions per minute per second, - said second acceleration rate is between 75 and 125 revolutions per minute per second, - said second stage ends when a target rotational speed is reached, - said target rotation speed is between 3,000 and 4,500 revolutions per minute, in particular between 3,600 and 3,900 revolutions per minute, - said method includes a step of controlling the engine rotational speed during said first and second acceleration steps, - said rotation speed control step includes a step of determining a setpoint speed, at a given instant, from said first and second acceleration rates, - said speed control step includes the use of a first control loop exploiting a difference between said setpoint speed and a rotation speed of said motor, resulting from a measurement and / or calculation, and delivering information relating to a setpoint current, - said speed control step includes the use of a second control loop exploiting a difference between the setpoint current and a current flowing in said motor, resulting from a measurement and / or calculation, - said process includes, for the implementation of said first and / or second acceleration steps, a step of operating software in which said first and / or second acceleration rates are predefined, - said process includes a step of determining values ​​for the first acceleration rate and / or the second acceleration rate, - said process includes an information transmission step, said information comprising said values ​​of the first acceleration rate and / or the second acceleration rate, - said transmission step uses a data bus, in particular a LIN bus, - the aforementioned first and second steps are applied in the case of a cold start, - the said first and second steps are applied with different values ​​of the first acceleration rate and / or the second acceleration rate at each start in the case of successive starts of said engine, - said motor is a direct current motor.

[0011] 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.

[0012] 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.

[0013] 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.

[0014] 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 which 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:

[0015] [Fig-1] is a flowchart corresponding to an example of implementation of the process according to the invention;

[0016] [Fig.2] is a graph schematically illustrating an evolution of a motor rotation speed according to an example of implementation of the method according to the invention;

[0017] [Fig.3] illustrates in functional form an example of a control device allowing implementation of the process according to the invention.

[0018] 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.

[0019] As illustrated in [Fig. 1], the invention relates to a method for controlling the starting of an electric motor, in particular a drive motor for an airflow generator. Specifically, this concerns 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.

[0020] Said motor is preferably controlled by means of a control unit comprising digital processing means, such as one or more microprocessors, optionally integrated into an assembled printed circuit board. Said board further comprises, for example, electrolytic capacitors. Said control unit is advantageously configured to be integrated into the control device referred to later in relation to [Fig. 3]. Said control device is preferably intended to be installed in the motor vehicle.

[0021] Said method successively comprises a first step 1 of accelerating said engine, according to a first acceleration rate K1, and a second step 2 of accelerating said engine, according to a second acceleration rate K2. The latter is lower than the first acceleration rate. The said first and second stages 1, 2 are activated at least when an ambient temperature is below a threshold, called cold ambient conditions.

[0022] The applicant has observed that such a strategy, consisting of starting with a high acceleration rate and then switching to a lower acceleration rate, makes it possible to limit unwanted micro-stops of the engine encountered in cold conditions, well below 0°C, while benefiting from a relatively short start-up time, on the order of twenty seconds, whereas using a single high acceleration rate leads to unwanted micro-stops of the engine that can prolong the start-up time to approximately one minute. Furthermore, such results are maintained with control devices, such as those mentioned above, of standard technology.

[0023] The first step is preferably applied until a certain rotational speed, referred to as the pivot speed, is reached, and / or the second acceleration step is applied from this pivot speed. In other words, the first and second steps 1, 2 are carried out consecutively without any intermediate variation in the engine acceleration. Advantageously, the second step 2 ends when a target rotational speed is reached.

[0024] In one embodiment, said first acceleration rate is between 500 and 1,000 revolutions per minute per second, in particular between 750 and 850 revolutions per minute per second. By way of example, said first acceleration rate is approximately 800 revolutions per minute per second.

[0025] Said second acceleration rate is less than 200 revolutions per minute per second. It is, in particular, between 75 and 125 revolutions per minute per second. By way of example, said second acceleration rate is approximately 100 revolutions per minute per second.

[0026] Said target rotational speed is between 3,000 and 4,500 revolutions per minute, in particular between 3,600 and 3,900 revolutions per minute. By way of example, it is approximately 3,750 revolutions per minute.

[0027] Said pivot rotation speed is between 1,500 and 2,500 revolutions per minute, in particular between 1,700 and 2,300 revolutions per minute.

[0028] Figure 2 illustrates the rotational speed of the electric motor as a function of time in such an example of starting the electric motor. In this figure, the x-axis represents time, in seconds, and the y-axis, the rotational speed of the motor, in revolutions per minute. The motor starts at time t0. It can be observed that the rotational speed initially increases sharply, along a first slope corresponding to the first acceleration rate K1, then from the pivot speed, shown as Vp, it increases less sharply, along a second slope corresponding to audit second acceleration rate K2, until reaching the target speed, illustrated Vc. It then remains constant.

[0029] Referring again to [Fig. 1], it can be seen that, advantageously, the process includes a step 3 for controlling the ambient temperature. The process further includes a step 4 for testing whether the threshold of cold ambient conditions has been crossed, exploiting said ambient temperature. Here, said step 3 for controlling the ambient temperature and / or said test step 4 occur before said first step 1.

[0030] In the illustrated example, as long as the cold ambient conditions threshold is not exceeded, the control and / or test steps 3 and 4 are executed, and the engine then starts preferentially according to a simplified strategy, for example, with a single engine acceleration rate until a desired engine speed is reached, in particular until the target speed is reached. Conversely, once the cold ambient conditions threshold is exceeded, the acceleration steps 1 and 2 are executed. When the target speed is then reached, the control and / or test steps 3 and 4 are repeated. Alternatively, once an initial start has taken place, the control and / or test steps 3 and 4 are no longer performed, at least during the same vehicle journey.

[0031] Said cold ambient conditions threshold is preferably defined by a temperature threshold, for example -30° Celsius. In other words, according to this example, the first and second acceleration stages 1, 2 are activated to start the engine if the ambient temperature is below -30°C.

[0032] Advantageously, the method includes a step for controlling the motor's rotational speed during the first and / or second acceleration stages. This rotational speed control step includes, for example, a step for determining a setpoint speed at a given instant, based on the first and second acceleration rates. This rotational speed control step further includes, in particular, the use of a first control loop exploiting a difference between the setpoint speed and a motor rotational speed obtained from a measurement and / or calculation, and providing information relating to a setpoint current. This speed control step also optionally includes the use of a second control loop exploiting a difference between the setpoint current and a current flowing through the motor, obtained from a measurement and / or calculation.The engine speed is regulated to ensure it follows the desired acceleration phases.

[0033] In [Fig.2], it is understood that such regulation is obtained by applying a voltage pulse during the said first and / or second acceleration steps.

[0034] Alternatively or cumulatively, such regulation is obtained by switching from an open-loop control mode to a closed-loop control mode, in particular from a certain threshold, notably a speed threshold.

[0035] Advantageously, said method includes, for an implementation of said first and / or second acceleration steps 1, 2, a software exploitation step 5.

[0036] In a first embodiment, said first and / or second acceleration rate Kl, K2 are predefined in said software.

[0037] Alternatively, the method includes a step of determining the values ​​of the first acceleration rate and / or the second acceleration rate K1, K2. Said first and / or second acceleration rates are, for example, derived from a calculation and / or a choice among different possible values ​​stored in a memory, said calculation and / or said choice exploiting one or more input data.

[0038] The method then includes a step of transmitting information comprising said values ​​of the first acceleration rate and / or the second acceleration rate, in particular to the control unit. This transmission step uses a data bus, in particular a LIN bus.

[0039] Preferably, said first and / or second steps 1, 2 are applied in the case of a cold start, that is to say, when the engine and its possible control unit have not been stressed for a significant period of time.

[0040] Alternatively or cumulatively, said first and / or second steps 1, 2 are applied with different values ​​of the first acceleration rate and / or the second acceleration rate at each start in the case of successive starts of said engine.

[0041] To this end, said method may optionally include a step of checking the time elapsed since a previous use of said engine and / or said control device to determine whether it is a cold start and / or a case of successive starts.

[0042] An example of a motor control device enabling the implementation of the method according to the invention is illustrated in [Fig.3] where said motor is identified as 100.

[0043] Said control device is advantageously configured to generate a supply current for said motor. It includes, for this purpose, an inverter 102. Said inverter 102 is configured to receive control currents from switches of said inverter 102. Said control currents have respective voltages Va, Vb, Vc and are used to obtain at the output of said inverter 102 a three-phase current, each phase of which has a respective intensity la, Ib, le, from a direct current supplying said inverter 102. Said direct current has here a voltage Vdc. Said three-phase current is configured to generate the rotating magnetic flux of said motor 100.

[0044] 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.

[0045] 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.

[0046] 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.

[0047] 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.

[0048] 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.

[0049] 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.

[0050] Said third transformation unit 112 is configured to convert the intensities la, Ib, le of the supply current into the intensities la and I[3 of the intermediate currents. Said fourth transformation unit 114 is configured to obtain the intensities Iq, Id of the torque and flux currents from the intensities la and I[3 of the intermediate currents. Said speed estimation unit 116 and / or the The angular position of the rotor of motor 100 is configured to operate from the voltages Va and V[3 as well as the intensities la and I[> of intermediate currents.

[0051] 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.

[0052] 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.

[0053] Moreover, in the application in question, the intensity Idref of the flux current used for control is preferably zero.

[0054] 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.

[0055] For switching from one control mode to another, said device here comprises a first and a second rocker unit 120, 122.

[0056] 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].

[0057] 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],

[0058] The engine acceleration rate can thus be controlled by monitoring its speed.

[0059] 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. Said system includes, for example, said control element described above.

[0060] The invention also 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.

[0061] The invention further relates to a data recording medium, readable by a computer, on which is recorded a computer program comprising program code instructions intended for an implementation of the steps of the process described above.

Claims

Demands

1. Method of controlling the starting of an electric motor, in particular a drive motor of an airflow generator, said method comprising successively a first step (1) of accelerating said motor, according to a first rate of acceleration (Kl), and a second step of accelerating said motor, according to a second rate of acceleration (K2), lower than the first rate of acceleration (Kl), said first and second steps (1,2) being activated at least when an ambient temperature is below a threshold, said cold ambient conditions.

2. Method according to claim 1 implemented using a control element comprising a printed circuit board, assembled, and / or one or more electrolytic capacitors.

3. A method according to any one of the preceding claims wherein the first step (1) is applied until a rotational speed (Vc), said pivot speed, of the motor is obtained and / or said second acceleration step (2) is applied from said pivot speed (Vc).

4. Method according to the preceding claim wherein said pivot rotation speed (Vc) is between 1,500 and 2,500 revolutions per minute, in particular between 1,700 and 2,300 revolutions per minute.

5. A method according to any one of the preceding claims comprising an ambient temperature control step (3), said ambient temperature control step (3) occurring before said first step (1).

6. A method according to any one of the preceding claims wherein said threshold of cold ambient conditions is -30° Celsius.

7. A method according to any one of the preceding claims wherein said second step (2) ends when a target rotational speed (Vc) is reached.

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. A computer program product comprising program code instructions recorded on a computer-readable medium for carrying out the steps of the process according to any

10. claims 1 to 7, when said program runs on a computer. 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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