Drive torque cut-off management method for rotating electric machines

Abstract

The invention relates to a method for controlling a rotating electric machine (10) of a vehicle, the rotating electric machine (10) comprising a stator (18) and a rotor (19), the electric machine comprising a control module (14) capable of generating a stator command (Comm_stat) as a function of the torque and the torque gradient to be applied to the electric machine (10), characterized in that: - after a demand for activating a drive mode of the electric machine (10), the method comprises a step of applying a setpoint torque (T_cons_ecu) and a setpoint torque gradient (G_cons_ecu) sent by a motor control computer, and - after a demand for stopping a previously activated motor mode and independently of the torque (T_cons_ecu) and the torque gradient (G_cons_ecu) requested by the computer (15), the method comprises a step of applying a zero setpoint torque (T_cons_mel) and a predetermined torque gradient (G_cons_mel) to the electric machine (10).

Description

Technical Field

[0001] The invention relates to a method for controlling a motor torque cut-off of a rotating electrical machine. Background Art

[0002] In a known manner, the reversible electric machine can be coupled to the heat engine, in particular via an accessory front end.

[0003] This electric machine, commonly referred to as an alternator starter, can operate in generator mode to charge the vehicle's battery or in motor mode to supply torque to the vehicle.

[0004] Generator mode can be used in regenerative braking functions, allowing the electric motor to supply electrical energy to the battery during braking phases.

[0005] The electric motor mode can be used in particular for a function that automatically stops and restarts the thermal engine depending on the traffic situation (STT function known as "Stop and Start"), a thermal engine stall assistance function, a function known as boost that allows the electric motor to intermittently assist the thermal engine during phases of driving in thermal mode, and a freewheel function known as coasting, which makes it possible to automatically open the traction chain without any specific action by the driver in order to reduce the engine speed or stop the engine, thereby minimizing fuel consumption and pollutant emissions.

[0006] In known electric machines, stopping in starter mode during activation of protection (thermal, time or speed) causes the switching elements of the inverter of the electric machine to open. The current contained in the stator then returns to the vehicle's onboard network, generating a torque surge at the accessory front end and an overvoltage on the onboard network. Summary of the invention

[0007] The object of the present invention is to effectively eliminate this drawback by proposing a method for controlling a rotating electrical machine of a motor vehicle, the rotating electrical machine comprising a stator and a rotor, the rotating electrical machine comprising a control module capable of generating a stator command as a function of the torque and the torque gradient applied to the rotating electrical machine, characterized in that:

[0008] - following a demand for activation of the motor mode of the rotary electric machine, in particular during starting of a thermal engine of a motor vehicle, the method comprises a step of applying a set torque and a set torque gradient sent by an engine computer of the motor vehicle; and

[0009] Following a demand to stop a previously activated motor mode, and independently of the torque and torque gradient requested by an engine computer of the motor vehicle, the method comprises a step of applying a setpoint torque equal to zero and a predetermined torque gradient to the rotary electric machine.

[0010] The invention thus makes it possible to continue controlling the electric machine after the need for a stop motor mode in order to reduce the current collected before the switching elements of the inverter are fully opened. This thus prevents torque surges in the motor vehicle and overvoltages on the onboard network.

[0011] According to one embodiment, the predetermined torque gradient depends on the rotational speed of the rotating electrical machine.

[0012] According to one embodiment, the greater the rotation speed of the rotating electrical machine, the lower the predetermined torque gradient.

[0013] According to one embodiment, the demand for the stop motor mode is generated after the end of the torque application period.

[0014] According to one embodiment, the need to stop the motor mode arises after a temperature threshold has been exceeded.

[0015] According to one embodiment, the need for the stop motor mode arises after a rotational speed threshold of the rotating electrical machine has been exceeded.

[0016] According to one embodiment, the control module may also generate a stator command based on the temperature of the rotor.

[0017] According to one embodiment, the control module may generate a rotor command based on the torque and the torque gradient to be applied to the rotating electric machine.

[0018] According to one embodiment, the rotor command is a value of the field current.

[0019] According to one embodiment, the stator command is defined by a lead angle between a voltage of the stator and an electromotive force of the rotating electrical machine, an opening angle of a switching element of the inverter, and a ripple voltage.

[0020] According to one embodiment, the rotating electrical machine is an alternator starter.

[0021] The invention also relates to a control module for a rotating electrical machine, characterized in that it comprises a memory storing software instructions for implementing the method for controlling a rotating electrical machine as defined above.

[0022] The invention also relates to a method for controlling a rotating electrical machine of a motor vehicle, the motor vehicle comprising a stator and a rotor, the rotating electrical machine comprising a control module capable of generating a stator command and a rotor command as a function of a torque and a torque gradient to be applied to the rotating electrical machine, characterized in that:

[0023] - following a demand for activation of the motor mode of the rotary electric machine, in particular during starting of a thermal engine of a motor vehicle, the method comprises a step of applying a set torque and a set torque gradient sent by an engine computer of the motor vehicle; and

[0024] Following a demand to stop a previously activated motor mode, and independently of the torque and torque gradient requested by an engine computer of the motor vehicle, the method comprises a step of applying a setpoint torque equal to zero and a predetermined torque gradient to the rotary electric machine.

[0025] The aforementioned features may be applied to the latest invention individually or in combination.

[0026] The invention will be better understood by reading the following description and examining the accompanying drawings, which are provided purely by way of illustration and not limitation of the invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 is a schematic functional representation of an alternator starter implementing the method according to the invention for optimizing the transition of an electric machine from one operating mode to another;

[0028] Figure 2 is a schematic representation of functional blocks integrated in a control unit according to the invention, which control unit makes it possible to control the application of torque to an electric machine;

[0029] Figure 3 is a diagram of signals that may be observed during implementation of the control method according to the invention;

[0030] Figure 4 A graph showing a method for determining an internal torque gradient of a motor according to the rotational speed of the motor.

[0031] From one figure to another, identical, similar or analogous elements retain the same reference numerals. DETAILED DESCRIPTION

[0032] Figure 1 An alternator starter 10 according to the invention is schematically represented. The alternator starter 10 is designed to be installed in a vehicle comprising an on-board electrical network connected to a battery 12. The on-board electrical network can be of the 12 V, 24 V or 48 V type. The alternator starter 10 is coupled to the heat engine 11 in a known manner via a system 11 ' with a belt or chain implanted in the front end of the accessories.

[0033] Furthermore, the alternator starter 10 can communicate with the engine computer 15 according to a communication protocol of the LIN (Local Interconnect Network) type or the CAN (Controller Area Network, which is a serial system bus) type.

[0034] The alternator starter 10 may operate in an alternator mode, which is also known as a generator mode or a motor mode.

[0035] Specifically, the alternator starter 10 includes an electrical component 13 and a control module 14 .

[0036] More specifically, the electrotechnical component 13 comprises an induced element 18 and an inductor element 19. According to one example, the induced element 18 is a stator and the inductor 19 is a rotor comprising an excitation coil 20. As a variant, the rotor comprises a set of metal plates and permanent magnets. The stator 18 comprises N phases. In the example considered, the stator 18 comprises three phases U, V and W. According to a variant, the number of phases N can be equal to 5 for a five-phase machine, 6 for a machine of the six-phase or double three-phase type, or 7 for a seven-phase machine. The phases of the stator 18 can be coupled in the form of a triangle or a star. Combinations of triangle and star couplings can also be envisaged.

[0037] The control module 14 includes an excitation circuit 141 including a chopper to generate an excitation current injected into the excitation coil 20. The excitation current can be measured, for example, by a shunt-type resistor.

[0038] The measurement of the angular position and angular velocity of the rotor 19 may be performed by means of Hall effect analog sensors H1 , H2 , H3 and associated magnetic targets 25 that rotate integrally with the rotor 19 .

[0039] The control module 14 further comprises a control circuit 142 comprising, for example, a microcontroller which controls the inverter 26 according to command signals obtained from the engine computer 15 and received via the signal connector 24 .

[0040] The inverter 26 has arms each comprising two switching elements, which make it possible to selectively connect the corresponding phases U, V, W of the stator 18 to ground or to the supply voltage B+ of the battery 12, depending on their on or off state. The switching elements are preferably power transistors of the MOSFET type.

[0041] refer to Figure 2 and Figure 3 , a description of a method according to the invention for controlling the torque of an electric machine during an aborted start-up phase of a thermal engine is provided below. The control module 14 may include a memory storing software instructions for its implementation.

[0042] More specifically, at the instant t0, when the thermal engine of the motor vehicle is started, during the demand for activation of the motor mode of the rotary electric machine, the engine computer 15 sends via the communication bus a corresponding command Inst_dem_ecu as well as a set torque T_cons_ecu and a set gradient G_cons_ecu to the electric machine 10. This start of the thermal engine takes place, for example, in the context of a function of automatically stopping and restarting the thermal engine according to traffic conditions (the so-called STT function of "stop and start").

[0043] Function block 27 forwards these values ​​to another function block 28, which can generate a stator command Comm_stat and, in particular, a rotor command Comm_rot based on these torque and torque gradient values. Function blocks 27, 28 are preferably integrated in control module 14. The rotor command Comm_rot corresponds to the excitation current value. The stator command Comm_stat is defined by the lead angle, the opening angle of the switching element and the ripple voltage. The lead angle corresponds to the phase difference between the voltage circulating in each phase of the stator 18 (controlled by the switching elements of the inverter 26) and the electromotive force of the motor 10. The opening angle corresponds to the electrical angle at which the switching element is at the potential B+ of the battery.

[0044] Therefore, if Figure 3 As shown, the motor 10 is in the starting state Dem_on. The internal set torque T_cons_mel corresponds to the set torque T_cons_ecu sent by the engine computer, for example 70 N.m, and the set torque gradient G_cons_mel corresponds to the set torque gradient G_cons_ecu sent by the engine computer 15, for example 200 N.m / s

[0045] At time t1, after a demand D to stop the previously activated motor mode, for example after the end of an alarm period corresponding to a thermal engine start failure, block 27 applies to the electric machine a set torque T_cons_mel equal to zero and a predetermined set torque gradient G_cons_mel of, for example, about 500 N.m / s. These values ​​are applied independently of the torque T_cons_ecu and the torque gradient G_cons_ecu requested by the engine computer 15.

[0046] The predetermined torque gradient G_cons_mel depends on the speed Wmel of the motor 10. Preferably, the greater the speed, the lower the predetermined torque gradient. Figure 4 The chart shown defines the internal torque gradient G_cons_mel of the motor according to the rotational speed Wmel of the motor. When the speed Wmel of the motor is lower than the threshold value S1 (for example, 400rpm), the chart sets a constant maximum value G_max of G_cons_mel, for example, 500N.m / s. When the speed Wmel of the motor is greater than the threshold value S2 (for example, 1200rpm), the chart sets a constant minimum value G_min of G_cons_mel, for example, 100N.m / s. When the rotational speed Wmel evolves from S1 to S2, the gradient G_cons_mel decreases linearly from the maximum value G_max to the minimum value G_min. It should be understood that other forms of charts can be conceived, in particular according to the evolution of polynomial or exponential functions, etc.

[0047] It can be observed that, in contrast to the strategy of opening the switching elements of the inverter 26, no overvoltage occurs on the on-board network during the implementation of the method for controlling a machine according to the invention (see the current curve Idc_edt on the on-board network obtained using the conventional strategy, and the curve Idc_inv obtained during the implementation according to the invention).

[0048] Then, the motor 10 enters a startup-suspended state Susp_dem, which lasts for about 100 ms, for example.

[0049] At time t2 , the motor 10 may then return to the start state Dem_on, in which the set torque T_cons_ecu and the torque gradient G_cons_ecu are applied to the motor.

[0050] At time t3, at the end of the warning period, block 27 applies to motor 10 a set torque T_cons_mel equal to zero and a set gradient G_cons_mel of, for example, about 400 N.m / s, by bypassing the values ​​T_cons_ecu, G_cons_ecu of engine computer 15. Motor 10 then enters a state Susp_dem' of startup suspension that lasts about 200 ms.

[0051] At time t4 , the motor 10 then enters a start state Dem_on in which the set torque T_cons_ecu and the set torque gradient G_cons_ecu are applied to the motor 10 .

[0052] At time t5, after having exceeded a speed threshold of the electric machine (this speed threshold corresponds, for example, to a threshold for the autonomy of the thermal engine), block 27 applies a set torque T_cons_mel equal to zero and a set torque gradient G_cons_mel of, for example, about 100 N.m / s to the electric machine 10. As the start of the thermal engine has been successful, the electric machine 10 transmits a corresponding state Mth_ok to the communication bus.

[0053] As a variant, the demand D to stop the motor mode may arise after a temperature threshold of the electric machine 10 has been exceeded, in particular the temperature at the stator 18 , the rotor 19 or a demand for a command or the power electronics of the electric machine.

[0054] Once the torque of the motor 10 has become zero, the phases of the stator 18 may be short-circuited, for example during a time period of about 10 ms±10%, in order to eliminate Joule losses from residual currents in the stator 18 .

[0055] It will be appreciated that the foregoing description is provided purely by way of example and does not limit the scope of the invention and that replacement of different elements with any other equivalents would not constitute a departure from the invention.

[0056] Furthermore, different features, variants and / or embodiments of the present invention can be associated with each other according to various combinations, as long as they are not incompatible or mutually exclusive.

Claims

1. A method for controlling a rotating electrical machine (10) of a motor vehicle, the rotating electrical machine (10) comprising a stator (18) and a rotor (19), the rotating electrical machine (10) comprising a control module (14), the control module (14) being capable of generating a stator command (Comm_stat) as a function of a torque to be applied to the rotating electrical machine (10) and a torque gradient, characterized in that: - following a demand for activation of the motor mode of the rotary electric machine (10), during starting of the thermal engine of the motor vehicle, the method comprises a step of applying a set torque (T_cons_ecu) and a set torque gradient (G_cons_ecu) sent by the engine computer of the motor vehicle; and - After a demand (D) for stopping a previously activated motor mode, and independently of a set torque (T_cons_ecu) and a set torque gradient (G_cons_ecu) requested by an engine computer (15) of the motor vehicle, the method comprises a step of applying to the rotary electric machine (10) a predetermined torque (T_cons_mel) equal to zero and a predetermined torque gradient (G_cons_mel).

2. The method according to claim 1, characterized in that The predetermined torque gradient (G_cons_mel) depends on the rotation speed (Wmel) of the rotating electrical machine (10).

3. The method according to claim 2, characterized in that The greater the rotation speed (Wmel) of the rotary electric machine (10), the lower the predetermined torque gradient (G_cons_mel).

4. The method according to any one of claims 1 to 3, characterized in that The demand (D) for the stop motor mode is generated after the end of the torque application period.

5. The method according to any one of claims 1 to 3, characterized in that The demand for the stop motor mode (D) arises after a temperature threshold has been exceeded.

6. The method according to any one of claims 1 to 3, characterized in that The demand (D) for the stop motor mode is generated after a rotation speed threshold of the rotating electrical machine (10) has been exceeded.

7. The method according to any one of claims 1 to 3, characterized in that The control module (14) is capable of generating a rotor command (Comm_rot) which is a value of an excitation current according to a torque to be applied to a rotating electric machine (10) and a torque gradient.

8. The method according to any one of claims 1 to 3, characterized in that The stator command (Comm_stat) is defined by the lead angle between the voltage of the stator (18) and the electromotive force of the rotating electric machine (10), the opening angle of the switching element of the inverter (26), and the ripple voltage.

9. The method according to any one of claims 1 to 3, characterized in that The rotating electrical machine (10) is an alternator starter.

10. A control module (14) for a rotating electrical machine (10), characterized in that: The control module (14) comprises a memory storing software instructions for implementing a method for controlling a rotating electrical machine (10) as defined in any one of claims 1-9.

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