WO2013153304A1

WO2013153304A1 - Method and system for controlling an electric machine of an electric vehicle

Info

Publication number: WO2013153304A1
Application number: PCT/FR2013/050651
Authority: WO
Inventors: Didier GILBERTAS; Tammam BASBOUS
Original assignee: Renault S.A.S.
Priority date: 2012-04-13
Filing date: 2013-03-26
Publication date: 2013-10-17
Also published as: FR2989479B1; EP2836390A1; FR2989479A1

Abstract

The invention relates to a system for controlling an electric machine of an electric vehicle in order to generate a torque setpoint for a given speed, said torque setpoint and said speed corresponding to a first operating point of said electric machine. The control system includes means for modulating the torque setpoint, which are configured to generate a modulated torque setpoint and to provide the modulated torque setpoint to said electric machine, said modulated torque setpoint alternating between a low value (Chas), the absolute value of which is lower than the absolute value of said torque setpoint, and a high value (Chaut), the absolute value of which is greater than the absolute value of said torque setpoint, said high value and said speed corresponding to a second operating point of said electric machine for which the power output is greater than the first operating point.

Description

System and method for controlling an electric machine equipping an electric vehicle

The technical field of the invention is the control systems and more particularly the torque control systems of an electric motor fitted to a vehicle, for example an electric traction vehicle.

The operation of an electric motor can be defined by the speed value of the engine and the value of the torque that it exerts. These two values correspond to an operating point of the motor. Electric motors generally have operating points for which their energy efficiency, that is to say the ratio between the electrical energy consumed and the mechanical energy generated, is favorable, especially by comparing them.

These more energy efficient operating points are generally in limited operating areas that do not always correspond to the operating areas of the engine when operating on the road.

It is planned, according to the state of the art, to use multi-speed gearboxes to allow a comparison or even a correspondence of the more favorable operating zones and the operating zones used.

However, the use of these gearboxes implies on the one hand an increased complexity, an overweight and an additional cost and on the other hand the gear change is not always very easy to manage by the driver of the vehicle or the automatic transmission control.

It is known from the state of the art to use a speed regulator which makes it possible to regulate the speed by means of oscillations of the speed of movement of the vehicle around a target value. However, it is proposed to improve the fuel consumption of the vehicle and not the fuel efficiency as such.

It is known from patent application WO 03/023209 to modulate the motor torque. However, the teaching of this document is limited to the case of internal combustion engines. In view of the foregoing, an object of the invention is to provide a control method of an electric machine that can solve at least in part the disadvantages mentioned above.

The object of the invention is therefore to provide a control system for an electric machine fitted to an electric vehicle, for generating a torque setpoint for a given speed of the electric machine, said torque setpoint and said speed corresponding to a first point of operation of said electric machine.

According to a general characteristic, this system comprises means for modulating the torque setpoint configured to generate a modulated torque setpoint and supplying the modulated torque setpoint to said electric machine, said modulated setpoint alternating a low value whose absolute value is lower. to the absolute value of said torque setpoint and a high value whose absolute value is greater than the absolute value of said torque setpoint, said high value and said speed corresponding to a second operating point of said electric machine for which the efficiency energy is greater than the first operating point.

It is thus proposed a control of an electrical machine that allows without the use of a mechanical system, a closer or even a correspondence of the operating zones of the electric machine more favorable from the point of view of energy efficiency and operating areas of the machine used during road use. It is then possible to obtain a better energy efficiency.

In addition, it is possible to avoid operating zones according to which the energy efficiency is not very favorable.

According to one characteristic, the modulation means are configured to adjust the ratio between the duration during which the modulated setpoint takes the high value and the period of the modulated setpoint, the average value of the modulated torque setpoint supplied to the electrical machine being equal. said torque setpoint. Thus, by simply adjusting the ratio of the duration that the high value takes with respect to the period of alternation between the high value and the low value (or period of the modulated setpoint), it is possible to obtain a modulated torque setpoint whose the average value is equal to that of the setpoint. There is therefore a transfer of mechanical energy from the electrical machine to a transmission shaft of the vehicle which is identical to that obtained with the torque setpoint but with a modulated torque setpoint.

According to another characteristic, the modulation means are configured to adjust the high value, the average value of the modulated torque setpoint supplied to the electrical machine being equal to said torque setpoint.

Thus, it is also possible to obtain a modulated torque setpoint whose average value is equal to that of the setpoint by adjusting the high value of the modulated setpoint.

According to yet another characteristic, the modulation means are configured to adjust the period of the modulated setpoint.

This adjustment can be used to mitigate problems of stability, noise and vibrations due to the chopped operation of the electric machine.

According to one embodiment, the low value taken by the modulated torque setpoint is the zero value corresponding to a non-power supply of the electric machine.

This system is particularly suitable for generating a modulated setpoint whose average value is low (for example less than 25% of the maximum torque of the electric machine). Indeed, a modulated torque setpoint whose value is high for reduced periods of time is then sufficient to obtain said average value. In fact, this high torque value allows an energy efficiency of the electric machine close to its maximum.

In addition, the stability, noise and vibration problems mentioned above are less critical in the case of a deposit modulated torque having a low average value (for example less than 25% of the maximum torque of the electric machine).

The invention also relates to a control method of an electric machine equipping an electric vehicle comprising:

a generation of a torque setpoint for a given speed of the electric machine, said speed setpoint and said torque setpoint corresponding to a first operating point of said electric machine.

According to a general characteristic, the method further comprises:

a modulation of the coupling setpoint e to generate a modulated torque setpoint, said modulated setpoint alternating a low value whose absolute value is lower than the absolute value of said torque setpoint and a high value whose absolute value is greater than the absolute value of said torque setpoint; and

a supply to the electric machine of said speed setpoint and said modulated torque setpoint, said high value and said speed corresponding to a second operating point of said electric machine for which the energy efficiency is higher than the first operating point.

According to one characteristic, the method further comprises a step of adjusting a ratio between the duration during which the modulated setpoint takes the high value and the period of the modulated setpoint, the average value of the modulated torque setpoint supplied to the electric machine being equal to said torque setpoint.

According to another characteristic, the method further comprises a step of adjusting the high value, the average value of the modulated torque setpoint supplied to the electrical machine being equal to said torque setpoint.

According to yet another characteristic, the method further comprises a step of adjusting the period of the modulated setpoint.

According to a mode of mi is implemented, the low value taken by the modulated torque setpoint is the zero value corresponding to a non-power of the electric machine. Other objects, features and advantages will appear on reading the following description given solely as a non-limitative example and with reference to the appended drawings in which:

- Figure 1 illustrates a block diagram of a control system according to an embodiment of the invention;

FIG. 2 illustrates a block diagram of a control method according to a mode of implementation of the invention;

FIG. 3 illustrates a torque set modulated according to a mode of mi implementation; and

FIG. 4 illustrates operating points according to an embodiment of the invention.

FIG. 1 schematically illustrates a VEL electric vehicle equipped with a GMP motopropulsor unit. The GMP powertrain comprises an electric machine MEL and a COMM control system of said electric machine MEL.

The COMM system supplies the electric machine MEL with a torque setpoint for a given speed. The electric machine MEL then operates according to an operating point corresponding to the given speed and the torque setpoint.

The torque setpoint can be positive or negative. A positive torque setpoint corresponds to a motor torque demand to be exerted by the electric machine MEL on a transmission shaft of said vehicle, this mechanical energy being finally transmitted to the wheels to ensure the movement of the vehicle. On the contrary, a negative torque setpoint corresponds to the resistive torque exerted by the MEL machine to recover the mechanical energy from the wheels during braking of the vehicle for example.

The COMM system generates a torque setpoint C l for a given RI speed, as a function of the speed required by the driver of the vehicle VIT and CR driving conditions (inclination of the road, current speed of the vehicle, state of the road). . For example, in the case of a speed of 60 km / h stabilized corresponding to a speed RI = 5000 rpm, the torque setpoint C l generated is C l = 1 0 Nm for a normal incline and road condition. The instruction Cl if it were supplied as such to the electric machine MEL would correspond with the RI regime at a first operating point PI of the electric machine MEL.

The COMM system further comprises MM modulation means. These means MM are configured to calculate a modulated torque setpoint CM from the generated torque setpoint C1. The means MM are also configured to supply the modulated torque setpoint CM to the electric machine MEL.

The modulated instruction CM is the result of a modulation of the set point C1. This modulation may for example be carried out according to the method known as MLI for Modulation by Pulse Width well known to those skilled in the art.

According to this PWM method, the modulated setpoint CM alternates a low value Cb _as whose absolute value is lower than the absolute value of said torque setpoint Cl (| Cb _as | <| C1 |) and a high value Chaut whose absolute value is greater than the absolute value of said torque setpoint Cl (| Chaut |> | C1 |).

The high value High of the modulated setpoint CM and the RI regime correspond to a second operating point P2 of the electric machine MEL. Advantageously, the energy efficiency for the second operating point P2 is greater than the energy efficiency for the first operating point P1.

During the alternation of the setpoint between high High and Low low, the RI regime remains almost constant. Its value oscillates very weakly around the given speed because it is the torque realized by the machine MEL which is chopped.

According to the PWM method, the average value of the modulated set point CM is equal to the set point Cl. For this purpose, the modulation means MM will adjust one or both of the following parameters:

a ratio a (a = Tl / T) between the duration T1 during which the modulated setpoint takes the high value High and the period of the modulated setpoint or the period of the alternation T between the high value High and the low value Cbas ; and - High value Chaut-

In fact, in the case where the low value Cb _as of the modulated setpoint CM is the zero value corresponding to a non-power supply of the motor, it suffices that the equation Chaut / Cl = a is respected for the average value of the setpoint modulated CM is equal to the reference Cl.

Thus, in the case of a positive Cl torque setpoint, the energy transmitted to the transmission shaft by the electric machine is identical that is provided to the electrical machine for the RI regime, the Cl torque setpoint or the modulated instruction CM.

On the contrary, in the case of a negative Cl torque setpoint, the mechanical energy recovered from the wheels during a braking of the vehicle for example is identical that is provided to the electric machine for the RI regime, the set point Cl or the modulated setpoint CM.

It is thus possible to operate the electric machine MEL with a more favorable energy efficiency by transmitting or receiving the same electrical or mechanical energy respectively.

However, with the modulation of the torque setpoint, the operation of the electric machine is chopped. This type of operation can cause stability, noise and vibration problems. To compensate for these problems, several solutions are possible:

a solution for adjusting the period T of the modulated setpoint or the period of alternation between the low value and the high value (T =

T1 + T0, with Tl already defined and T0 the duration during which the modulated setpoint takes the low value Cb _as ) and specific alternation sequences to limit the vibrations. For example, to obtain modulated setpoint having an average value of equal to a set point Cl = 10 Nm, it is possible to carry out 1 motor revolution at 40 N.m., followed by 3 motor revolutions at 0 Nm with an alternating frequency of 20 Hz; and

a solution for filtering the oscillations of the torque exerted by the passive-type electric machine, for example by means of a flywheel placed on the transmission shaft or flexible elements placed between the rotor of the motor and the drive shaft.

FIG. 2 illustrates a mode of implementation of the control method according to the invention. It includes 6 stages.

During a first step 1, a torque setpoint C1 is generated for a given speed RI, as a function of a speed of movement of the vehicle VIT and driving conditions CR. The RI regime is in fact imposed by the speed of movement of the vehicle VIT, the gear ratio between the engine and the wheels of the vehicle and the transmission of the wheels of the vehicle.

In the following step 2, the ratio a is adjusted between the duration T1 during which the modulated setpoint takes the high value High and the period T of the modulated setpoint.

Then, in the following step 3, the high value High of the modulated setpoint is adjusted.

The period T of the modulated set point is then adjusted (step

4) ·

Then, in the following step 5, the torque setpoint C1 is modulated to generate the modulated torque setpoint CM.

Finally, step 6 is a step of supplying the electrical machine with the instruction CM.

The order of steps 1 to 6 illustrated in Figure 2 is an example of implementation and could be modified according to the technology of the control.

FIG. 3 comprises a marker comprising two axes, a horizontal axis representing the time and a vertical axis representing the value of the torque in Nm. On this reference there is a first curve representing the setpoint CM alternating the high value High and the low value Cb. _as (here Cb _as = 0) and a second curve which represents an average of the setpoint CM. The second curve may correspond according to one embodiment to the torque setpoint Cl.

It can be seen that the increase in the duration T 1 of the high values of the setpoint CM corresponds to an increase in the average of the setpoint CM. In this figure is also represented:

- the period of the modulated setpoint T;

the ratio a between the duration T i during which the modulated setpoint takes the high value High and the period T of the modulated setpoint or alternation period between the high value High and the low value Cb _as ; and

- High value Chaut - Figure 4 comprises a reference comprising two axes, a horizontal axis representing the RPM of the electric machine MEL and a vertical axis representing the value of torque in Nm On this reference mark are several curves C _{1 50} , C _{1 00} , C 50 and C 1 50 delimiting several energy-inefficient operating zones and three operating points P2, PI and PO.

The point P I corresponds to an operation of the electric machine MEL with the set point C l = 30 N.m and the speed R I = 3000 rpm. This point is below the curve C 50 and is therefore in an operating zone for which the energy efficiency is low. The powertrain losses are then 1450 W.

The point P0 corresponds to an operating point of the electric machine MEL with the speed RI = 3000 rpm and the low value of the torque set point Cb _as = 0, this zero value of the torque setpoint corresponding to a non-power supply of the engine. The powertrain losses for the operating point P0 are reduced to 100W.

The point P2 corresponds to an operation of the electric machine MEL with the high value of the torque set point Chaut = 100 N.m and R I = 3000 rpm. Powertrain losses for P2 operating point are 4000W

It is necessary for the average of the modulated set point CM to be equal to the set point C l to comply with the equation a = Chaut / C l. This implies T l / T = 0.3 with Ch values _at t = 100 Nm and C l = 30 Nm. That is to say that for each period of the modulated set point T, CM = 100 Nm for 30% of the period T and CM = 0 Nm for the remaining 70% of the period T. This corresponds to a functioning of the electrical machine following the point P2 for 30% of the time and following the PO point for 70%> of the time.

The powertrain losses are then: 0.3 x 4000PF + 0.7 x 100W = 1210W.

Thus, a 12% decrease in losses is obtained with respect to operation following the point P I only for the same energy transmitted to the transmission shaft.

Claims

1. Control system (COMM) of an electric machine (MEL) equipping an electric vehicle (VEL), for generating a torque setpoint (C l) for a given speed (RI) of the electric machine (MEL), said setpoint of torque and said speed (RI) corresponding to a first operating point (PI) of said electric machine,

characterized in that it comprises means (MM) for modulating the torque setpoint (C l) configured to generate a modulated torque setpoint (CM) and supplying the modulated torque setpoint to said electric machine (MEL), said modulated reference (CM) alternating a low value (Cb _as ) whose absolute value is lower than the absolute value of said torque setpoint (C l) and a high value (Chaut) whose absolute value is greater than the absolute value of said torque setpoint (C l), said high value (C aut) and said speed (RI) corresponding to a second operating point (P2) of said electrical machine for which the energy efficiency is greater than the first operating point.

2. System according to claim 1, wherein the modulation means (MM) are configured to adjust the ratio (a) between the duration (T l) during which the modulated setpoint takes the high value and the period (T) of the modulated setpoint, the average value of the modulated torque setpoint (CM) supplied to the electrical machine (MEL) being equal to said torque setpoint (C l).

3. System according to one of claims 1 or 2, wherein the modulation means are configured to adjust the high value (Halt), the average value of the modulated blow set (CM) supplied to the electrical machine ( MEL) being equal to said torque setpoint (C l).

4. System according to one of revendi cations 2 or 3, wherein the modulation means (MM) are configured to adjust the period (T) of the modulated set.

5. System according to any one of claims 1 to 4, wherein said low value (C _{b as} ) taken by the modulated torque setpoint is the zero value (C _low = 0) corresponding to a non-power of the electric machine (EMAIL) .

6. A method of controlling an electric machine equipping an electric vehicle comprising generating a torque setpoint (C l) for a given speed (RI) of the electric machine (MEL), said speed (RI) and said setpoint a torque (C l) corresponding to a first operating point of said electric machine,

characterized in that the method further comprises:

a modulation of the torque setpoint for generating a modulated torque setpoint (CM), said modulated setpoint alternating a low value (C _bas ) whose absolute value is lower than the absolute value of said torque setpoint (C l) and a high value (C _aut ) whose absolute value is greater than the absolute value of said torque setpoint (C l); and

a supply to the electrical machine (MEL) of said modulated torque setpoint (CM), said high value (C _aut ) and said speed (RI) corresponding to a second operating point (P2) of said electric machine (MEL); where the energy efficiency is higher than the first operating point.

7. The method according to claim 6, further comprising a step of adjusting a ratio (a) between the duration (T 1) during which the modulated setpoint takes the high value and the period (T) of the modulated setpoint, the average value of the modulated torque setpoint (CM) supplied to the electrical machine (MEL) being equal to said torque setpoint (C l).

8. Method according to one of claims 6 or 7, further comprising a step of adjusting the high value (C _high ), the value average of the modulated torque setpoint (CM) supplied to the electrical machine (MEL) being equal to said torque setpoint (Cl).

9. Method according to any one of claims 7 and 8, further comprising a step of adjusting the period (T) of the modulated setpoint.

10. Method according to any one of claims 6 and 9, wherein said low value (C _low ) taken by the modulated torque setpoint (CM) is the zero value (C _low = 0) corresponding to a no power of the electric machine (MEL).