FR3078215A1 - METHOD FOR ASSISTING THE SETTING OF A THERMAL MOTOR BY A ROTATING ELECTRIC MACHINE - Google Patents

Abstract

The invention relates mainly to a method of assisting the setting of a motor vehicle heat engine (11) by generating a resistive torque by a rotating electrical machine (10), said rotating electrical machine (10) comprising: - a wound rotor (19) to be traversed by an excitation current (lex), and - a stator (18) comprising a plurality of phases (U, V, W), characterized in that said method comprises: - a step receiving a set torque (Tcons), - a step of measuring the rotational speed (Wmel) of the rotor (19) of the rotating electrical machine, - an application step at the input of a mapping, the setpoint torque (Tons) and the rotational speed (Wmel) of the rotor (19) to obtain a value of a target excitation current; - a step of application of an excitation current (lexc) to the wound rotor (19) corresponding to the target excitation current while the phases of the stator (18) are half its short circuit, so that the rotating electrical machine (10) generates the resistive torque.

Description

METHOD FOR ASSISTING THE SETTING OF A HEAT ENGINE

BY A ROTATING ELECTRIC MACHINE

The present invention relates to a method for assisting the stalling of a heat engine by a rotary electric machine.

In a manner known per se, a reversible electric machine can be coupled to the heat engine, in particular via the accessories front.

This electric machine, commonly called alternator-starter, is capable of operating in a generator mode to recharge a battery of the vehicle as well as in an engine mode to provide a torque to the vehicle.

The generator mode can be used in a regenerative braking function allowing the electric machine to supply electrical energy to the battery during a braking phase.

The engine mode can in particular be used in an automatic engine stop and restart function according to the traffic conditions (so-called STT function for stop and start in English), a stall assist function, so-called boost function in English allowing the electric machine to punctually assist the heat engine during a taxiing phase in thermal mode, and a freewheeling function, called coasting in English, used to automate the opening of the powertrain without any explicit action by the driver to reduce engine speed or stop it to minimize fuel consumption and polluting emissions.

When implementing the stall assist function, improper control of the torque setpoint can lead to various problems. Thus, an excessively low torque drawdown generates vibrations of the engine and therefore of the vehicle; while taking too much torque from the engine is likely to damage the components on the front of the heat engine accessories.

The present invention aims to effectively remedy these drawbacks by proposing a method for assisting the stalling of a heat engine of a motor vehicle, by generation of a resistive torque by a rotary electric machine, said rotary electric machine comprising:

- a wound rotor intended to be traversed by an excitation current, and

- a stator comprising several phases, characterized in that said method comprises:

- a step of receiving a setpoint torque,

a step of measuring the speed of rotation of the rotor of the rotary electric machine,

a step of application at the input of a map, the setpoint torque and the speed of rotation of the rotor to obtain a value of a setpoint excitation current,

- A step of applying an excitation current to the wound rotor corresponding to the set excitation current while the phases of the stator are short-circuited, so that the rotating electric machine generates the resistive torque.

The invention thus makes it possible, thanks to the use of mapping establishing the correspondence between the excitation current and the setpoint torque, to precisely control the electric machine in torque. This avoids the problems of engine vibration and early deterioration of the components on the accessory front.

According to one implementation, the mapping is constructed by changing the excitation current and the speed of rotation of the rotor to determine a corresponding torque, then the mapping is returned so as to be able to apply the speed of rotation of the rotor and the torque of setpoint at the input of said mapping.

According to one implementation, the setpoint torque comes from an engine computer.

According to one implementation, said method includes a step of regulating the excitation current applied to the wound rotor as a function of the set excitation current.

According to one implementation, the rotational speed of the rotor is measured using analog Hall effect sensors.

According to one implementation, the rotary electric machine is an alternator-starter.

The invention also relates to a control module for a rotating electric machine, characterized in that it includes a memory storing software instructions for implementing the method for assisting the stalling of a thermal engine of a motor vehicle such as than previously defined.

The invention also relates to a control module for a rotating electrical machine characterized in that it comprises a programmable logic circuit, for example in the form of an FPGA (for FieldProgrammable Gâte Array in English) or CPLD (for Complex Programmable Logic Device in English), or an integrated circuit, for example an ASIC (for application-specific integrated circuit in English), configured for the implementation of the method for estimating a direct current generated by the rotating electric machine as previously defined.

The invention will be better understood on reading the description which follows and on examining the figures which accompany it. These figures are given only by way of illustration but in no way limit the invention.

Figure 1 is a functional schematic representation of the alternator starter implementing the method according to the invention of assistance in stalling of a heat engine of a motor vehicle;

FIG. 2 is a schematic representation illustrating the integration of the torque setpoint in the stall assist function of the heat engine according to the present invention;

Figure 3 is a schematic representation of the principle of torque control according to the present invention;

FIG. 4 is an example of a map providing an excitation current for the rotor as a function of a setpoint torque and a speed of rotation of the rotary electric machine.

Identical, similar, or analogous elements retain the same reference from one figure to another.

Figure 1 shows schematically an alternator-starter 10 according to the invention. The alternator-starter 10 is intended to be installed in a vehicle comprising an on-board electrical network connected to a battery 12. The on-board network may be of the 12V, 24V, or 48V type. The alternator-starter 10 is coupled to a heat engine 11 in a manner known per se by a belt system 11 'or chain installed on the accessory front.

In addition, the alternator-starter 10 is able to communicate with an engine computer 15 according to a communication protocol of the LIN type (Local Interconnect Network in English or Local Internet Network in French) or CAN (Controller Area Network in English which is a serial system bus).

The alternator-starter 10 can operate in alternator mode also called generator mode or in engine mode.

The alternator-starter 10 notably comprises an electrotechnical part 13 and a control module 14.

More specifically, the electrotechnical part 13 comprises an armature element 18 and an inductor element 19. In one example, the armature 18 is the stator, and the inductor 19 is a rotor comprising an excitation coil 20. The stator 18 comprises a number N of phases. In the example considered, the stator 18 has three phases U, V and W. As a variant, the number N of phases may be equal to 5 for a five-phase machine, to 6 for a machine of the hexaphase or double three-phase type or to 7 for a heptaphase machine. The phases of the stator 18 can be coupled in a triangle or a star. A combination of triangle and star coupling is also possible.

The control module 14 comprises an excitation circuit 141 integrating a chopper to generate an excitation current which is injected into the excitation coil 20. The measurement of the excitation current can be carried out for example using '' a shunt type resistor.

The angular position and the angular speed of the rotor 19 can be measured by means of analog Hall effect sensors H1, H2, H3 and an associated magnetic target 25 which is integral in rotation with the rotor 19.

The control module 14 further comprises a control circuit 142, comprising for example a microcontroller, which controls an inverter 26 as a function of a control signal from the engine computer 15 and received via a signal connector 24.

The inverter 26 has arms each comprising two switching elements making it possible to selectively connect a corresponding phase U, V, W of the stator 18 to the ground or to the supply voltage B + of the battery 12 as a function of their on state or blocked. The switching elements are preferably MOSFET type power transistors.

Is described below with reference to Figures 2 and 3, the method according to the invention of stalling assistance of the heat engine 11, by generation of a resistive torque by the electric machine 10. This resistive torque is obtained in short -circuiting the phases of the stator 18 and applying a lexc excitation current to the wound rotor 19. The invention aims to precisely adapt the lexc excitation current as a function of the need for resistive torque emitted by the engine computer 15.

The control module 14 may include a memory storing software instructions for its implementation. As a variant, the control module 14 includes a programmable logic circuit, for example in the form of an FPGA (for Field-Programmable Logic Array in English) or CPLD (for Complex Programmable Logic Device in English), or an integrated circuit , for example an ASIC (for application-specific integrated circuit in English) configured for the implementation of the method according to the invention for estimating the current delivered by the electric machine 10.

More specifically, the torque control module M1 receives a setpoint torque Tcons, in particular from the engine computer 15, as well as a measurement of the speed of rotation Wmel of the rotor. The rotational speed of the rotor Wmel is measured using analog Hall effect sensors.

The setpoint torque Tcons and the speed of rotation Wmel are applied at the input of a map C1 shown in FIG. 4 to obtain at output a corresponding value of a setpoint excitation current lexc_cons. The C1 mapping is advantageously constructed by changing the excitation current lexc and the speed of rotation of the rotor Wmel to determine a corresponding torque; then the map is returned so as to be able to apply the speed of rotation Wmel and the setpoint torque Tcons at the input.

An excitation current lexc corresponding to the setpoint torque lexc_cons is applied to the wound rotor 19 while the phases of the polyphase stator 18 are short-circuited to ground, so that the rotary electrical machine 10 generates the resistive torque.

To this end, the lexc_cons setpoint excitation current is applied to the M2 control module (see Figure 2). In a manner known per se, this module M2 comprises a comparator for comparing the value of the lexc excitation current applied to the rotor 19 with the reference current lexc_cons in order to determine a difference. This current difference is applied at the input of a corrector, for example of the PI (for Proportional and Integral) or PID (for Proportional Integral and Derivative) type in order to deduce therefrom a duty cycle transmitted to the excitation circuit 141 of the rotor coil 19. This gives a lexc excitation current corresponding to the set excitation current lexc_cons.

Of course, the foregoing description has been given by way of example only and does not limit the scope of the invention from which one would not depart by replacing the various elements with any other equivalent.

Furthermore, the various features, variants, and / or embodiments of the present invention can be combined with one another in various combinations, insofar as they are not incompatible or mutually exclusive of one another.

Claims (8)

1. Method for assisting the stalling of a heat engine (11) of a motor vehicle, by generation of a resistive torque by a rotary electric machine (10), said rotary electric machine (10) comprising: - a wound rotor (19) intended to be traversed by an excitation current (lex), and - a stator (18) comprising several phases (U, V, W), characterized in that said method comprises: - a step of receiving a setpoint torque (Tcons), a step for measuring the speed of rotation (Wmel) of the rotor (19) of the rotary electric machine, a step of application at the input of a map, of the setpoint torque (Tcons) and of the rotation speed (Wmel) of the rotor (19) to obtain a value of a setpoint excitation current (lexc_cons) , a step of applying an excitation current (lexc) to the wound rotor (19) corresponding to the set excitation current (lexc_cons) while the phases of the stator (18) are short-circuited, so that the rotating electrical machine (10) generates the resistive torque. 2. Method according to claim 1, characterized in that the map (C1) is constructed by changing the excitation current and the speed of rotation (Wmel) of the rotor (19) to determine a corresponding torque then the map is returned so as to be able to apply the speed of rotation of the rotor (Wmel) and the setpoint torque (Tcons) at the input of said mapping. 3. Method according to claim 1 or 2, characterized in that the setpoint torque (Tcons) comes from an engine computer (15). 4. Method according to any one of claims 1 to 3, characterized in that it comprises a step of regulating the excitation current (lexc) applied to the wound rotor (19) according to the set excitation current ( lexc_cons). 5. Method according to any one of claims 1 to 4, characterized in that the rotational speed (Wmel) of the rotor (19) is measured using analog Hall effect sensors (H1, H2, H3). 6. Method according to any one of claims 1 to 5, 5 characterized in that the rotary electric machine (10) is an alternator-starter. 7. Control module (14) for a rotating electrical machine (10) characterized in that it includes a memory storing software instructions for implementing the method of assisting in the setting of a heat engine of a motor vehicle. as defined in any one of claims 1 to 6. 8. Control module (14) for a rotary electrical machine characterized in that it comprises a programmable logic circuit or an integrated circuit configured for the implementation of the estimation process 15 of a direct current generated by the rotary electric machine as defined according to any one of claims 1 to 6.