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

Abstract

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

Description

[0001] Method for controlling the starting of an electric motor, in particular a drive motor for an airflow generator

[0002] The invention relates to a method for controlling the starting of an electric motor, in particular a motor 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.

[0003] In this field, it is known to control electric motors by applying a rotational speed setpoint and ensuring that this setpoint is reached in a minimum time.

[0004] In cold weather, with this strategy, the applicant observed that unwanted micro-shutdowns of the engines occur, lengthening the time to reach the desired operating 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 occupants.

[0005] The applicant hypothesized that such micro-stops originated at least in part from electronic motor control devices, including electrical capacitors used in these devices, the performance of these capacitors dropping in cold temperatures.

[0006] One possible solution to this problem would be to choose more robust electronic components for motor control. However, these are expensive, which limits their appeal.

[0007] 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.

[0008] According to the applicant's findings, starting with a high acceleration rate and then gradually decreasing it reduces the risk of unwanted motor stalling while maintaining a relatively short start-up time, even in cold ambient temperatures. This result is achieved without using different electronic components than those used for operation in warmer temperatures. Therefore, the same printed circuit boards can be used, or at the very least, electrolytic capacitors can be used to control the motors.

[0009] In other words, according to the invention, preferably, the 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. This control element is advantageously configured to deliver a direct current with a stabilized voltage, used to power switches employed to generate the current supplying the motor.

[0010] Preferably, taking into account the intended applications, said motor delivers increasing torque with an increase in the rotational speed of said motor.

[0011] According to various additional features of the invention, which may be taken together or separately and which constitute so many embodiments of the invention:

[0012] - the first step is applied until a certain speed, called the pivot speed, of motor rotation is obtained,

[0013] - said second acceleration stage is applied from said pivot velocity,

[0014] - said process includes a step of controlling the ambient temperature,

[0015] - the said ambient temperature control step takes place before the said first step,

[0016] - said cold ambient conditions threshold is -30° Celsius, - 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,

[0017] - 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,

[0018] - said second acceleration rate is less than 200 revolutions per minute per second,

[0019] - said second acceleration rate is between 75 and 125 revolutions per minute per second,

[0020] - said second stage ends when a target rotational speed is reached,

[0021] - 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,

[0022] - said method includes a step of controlling the engine rotational speed during said first and second acceleration steps,

[0023] - said rotation speed control step includes a step of determining a setpoint speed, at a given instant, from said first and second acceleration rates,

[0024] - 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,

[0025] - 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,

[0026] - 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,

[0027] - said method includes a step of determining values ​​of the first acceleration rate and / or the second acceleration rate, - said method includes a step of transmitting information, said information comprising said values ​​of the first acceleration rate and / or the second acceleration rate,

[0028] - said transmission step uses a data bus, in particular a LIN bus,

[0029] - the aforementioned first and second steps are applied in the case of a cold start,

[0030] - 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,

[0031] - said motor is a direct current motor.

[0032] 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.

[0033] 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.

[0034] 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.

[0035] The invention will be better understood, and other objects, details, features and advantages thereof will become more apparent from the following detailed explanatory description 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:

[0036] [Fig 1] is a flowchart corresponding to an example of implementation of the process according to the invention; [Fig 2] is a graph schematically illustrating an evolution of a motor rotation speed according to an example of implementation of the process according to the invention;

[0037] [Fig 3] illustrates in functional form an example of a control device enabling implementation of the process in accordance with the invention.

[0038] It should first be noted that the terms "first", "second", "third", ... are only used to distinguish the components concerned from each other and do not imply any order or possible importance of said components.

[0039] As illustrated in Figure 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, the motor must be able to deliver increasing torque with increasing motor speed.

[0040] The 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. This board further includes, for example, electrolytic capacitors. The control unit is advantageously configured for integration into the control device described later in relation to Figure 3. This control device is preferably intended to be installed in the motor vehicle.

[0041] The method comprises successively a first step 1 of accelerating the motor, according to a first acceleration rate K1, and a second step 2 of accelerating the motor, according to a second acceleration rate K2. The latter is lower than the first acceleration rate. The first and second steps 1 and 2 are activated at least when an ambient temperature is below a threshold, referred to as cold ambient conditions.

[0042] The applicant observed that a strategy of starting with a high acceleration rate and then transitioning to a lower rate helps to limit unwanted engine micro-stops, which occur in cold conditions well below 0°C, while maintaining a relatively short start-up time of around twenty seconds. In contrast, using a single high acceleration rate results in unwanted engine micro-stops that can extend the start-up time to approximately one minute. Furthermore, these results are consistent with standard technology control devices, such as those mentioned above.

[0043] The first step is preferably applied until a target 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 and 2, are carried out consecutively without any intermediate variation in engine acceleration. Advantageously, the second step, 2, ends when a target rotational speed is reached.

[0044] 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.

[0045] The second acceleration rate is less than 200 revolutions per minute per second. Specifically, it is between 75 and 125 revolutions per minute per second. For example, the second acceleration rate is approximately 100 revolutions per minute per second.

[0046] The target rotational speed is between 3,000 and 4,500 revolutions per minute, specifically between 3,600 and 3,900 revolutions per minute. For example, it is approximately 3,750 revolutions per minute.

[0047] Said pivot rotation speed is between 1,500 and 2,500 revolutions per minute, specifically between 1,700 and 2,300 revolutions per minute.

[0048] Figure 2 illustrates the rotational speed of the electric motor as a function of time in such an example of an electric motor start-up. In this figure, the x-axis represents time, in seconds, and the y-axis, the motor's rotational speed, in revolutions per minute (rpm). The motor starts at time t0. We observe that the rotational speed initially increases sharply, following a first slope corresponding to the first acceleration rate K1. Then, from the pivot speed, shown as Vp, it increases less sharply, following a second slope corresponding to the second acceleration rate K2, until it reaches the target speed, shown as Vc. It then remains constant.

[0049] Referring again to Figure 1, we observe 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 ambient temperature control step 3 and / or said testing step 4 occur before said first step 1.

[0050] In the illustrated example, as long as the cold ambient temperature threshold is not exceeded, 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, specifically until the target speed is reached. However, once the cold ambient temperature threshold is exceeded, acceleration steps 1 and 2 are executed. When the target speed is reached, control and / or test steps 3 and 4 are repeated. Alternatively, once the first start has occurred, control and / or test steps 3 and 4 are no longer performed, at least during the same vehicle journey.

[0051] This 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 and 2 are activated to start the engine if the ambient temperature is below -30°C.

[0052] 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 from the first and second acceleration rates. This rotational speed control step further includes, in particular, the use of a first control loop that exploits the difference between the setpoint speed and the motor's rotational speed, obtained from a measurement and / or calculation, and provides information relating to a setpoint current. This speed control step also includes, optionally, the use of a second control loop that exploits the difference between the setpoint current and a current flowing through the motor, obtained from a measurement and / or calculation.We are regulating the engine speed so that it follows the desired acceleration phases.

[0053] Figure 2 shows that such regulation is achieved by applying a voltage pulse during the said first and / or second acceleration stages.

[0054] Alternatively or cumulatively, such regulation is achieved by switching from an open-loop control mode to a closed-loop control mode, particularly from a certain threshold, notably a speed threshold.

[0055] Advantageously, the said process includes, for an implementation of the said first and / or second acceleration steps 1, 2, a step 5 of operating a software.

[0056] In a first embodiment, said first and / or second acceleration rate K1, K2 are predefined in said software.

[0057] Alternatively, the method includes a step of determining the values ​​of the first acceleration rate and / or the second acceleration rate K1, K2. The said first and / or second acceleration rate are, for example, derived from a calculation and / or a choice among different possible values ​​stored in a memory, the said calculation and / or choice exploiting one or more input data.

[0058] The process then includes a step of transmitting information comprising the 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.

[0059] Preferably, the 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.

[0060] 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.

[0061] To this end, the said process may optionally include a step of checking the time elapsed since a previous use of the said engine and / or said control device to determine whether it is a cold start and / or a case of successive starts.

[0062] An example of a motor control device enabling the implementation of the process according to the invention is illustrated in figure 3 where said motor is identified as 100.

[0063] The control device is advantageously configured to generate a supply current for the motor. It includes an inverter 102 for this purpose. The inverter 102 is configured to receive control currents from its switches. 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 for the motor 100.

[0064] The 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.

[0065] The 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. The second transformation unit 106 is configured to obtain the intermediate current voltages Va and V|3 from the torque current, which here has a voltage Vq, and a flux current, which here has a voltage Vd.

[0066] The said torque control unit 108 is configured to define the torque current voltage Vq from the difference between a control current Iqref and a measured current lq m said torque current, in particular with the aid of a proportional, integral and / or derivative regulator.

[0067] The 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.

[0068] 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 lq re f of the torque current to be applied. The value of the square wave is determined, for example, from the characteristics of the motor.

[0069] To operate in closed-loop speed control, said device further includes here a third unit 1 12 configured to perform a Clarke transformation, a fourth unit 1 14 configured to perform a Park transformation, a unit 1 16 for estimating the speed and / or angular position of the rotor of motor 100 and / or a speed control unit 1 18.

[0070] The third transformation unit 112 is configured to convert the supply currents Ia, Ib, and Ie into the intermediate currents Ia and Il. The fourth transformation unit 114 is configured to obtain the torque and flux currents Iq and Id from the intermediate currents Ia and Ip. The unit 116 for estimating the speed and / or angular position of the motor rotor 100 is configured to operate from the voltages Va and Vl, as well as the intermediate currents Ia and Il.

[0071] The speed control unit 1 18 is configured to deliver a torque current value Iq to be applied to the torque control unit 1 12 from a difference between the target speed Vc and the speed information Vm delivered by said estimation unit 1 16.

[0072] It should also be noted that the rotor position information is used at the level of the second and fourth transformation units 106, 1 12 of inverted Park and Park. The said torque current intensities lq m and Idm fluxes delivered by said fourth transformation unit 1 14 are thus qualified as measured and / or estimated.

[0073] Furthermore, in the application in question, the intensity Idref of the flux current used for control is preferably zero.

[0074] According to the illustrated embodiment, the concepts of open and closed loops 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 lq. mand Idm of the measured and / or estimated torque and flux currents. The system, however, is in closed-loop speed control when it operates with feedback on the speed, or even on the angular position of the rotor.

[0075] For switching from one control mode to another, the said device here includes a first and a second toggle unit 120, 122.

[0076] The first 120 flip-flop unit is configured to allow the device to take into account the value of the torque current intensity lq re f from the square wave signal when open loop motor control step 8 is active, according to the position marked Ol in Figure 2, and to take into account the value of the torque current intensity lqref from the speed control unit 1 18 when closed loop motor control step 10 is active, according to the position marked Cl in Figure 2.

[0077] The second flip-flop unit 122 is configured not to return the value of the rotor position at the level of said second and fourth transformation units 106, 1 12 when the open-loop motor control step 8 is active, according to the position marked Ol in Figure 2, and to take into account this value when the closed-loop motor control step 10 is active, according to the position marked Cl in Figure 2.

[0078] The engine's acceleration rate can thus be controlled by monitoring its speed.

[0079] 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, the control unit described previously.

[0080] 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.

[0081] 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 implementing the steps of the process described above.

Claims

DEMANDS 1. Method for 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 (K1), and a second step of accelerating said motor, according to a second rate of acceleration (K2), lower than the first rate of acceleration (K1), 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. 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. 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. Computer-readable data recording medium on which is recorded a computer program comprising program code instructions for implementing the steps of the process according to any one of claims 1 to 7.

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