FR3132470A1 - DETERMINATION OF THE TORQUE REQUIRED OF AN ELECTRIC DRIVE MACHINE OF A VEHICLE IN A DEGRADED TRAVEL MODE - Google Patents

Abstract

A method is implemented in a vehicle comprising a powertrain, comprising an electric drive machine supplying or recovering a requested torque, and a degraded travel mode at at least one target speed. This method comprises a step (10-60) in which, when the mode is established, the torque requested is controlled as a function of the actual speed of the land vehicle and of a first value representative of a difference between the target speed and the speed real. Picture 3

Description

DETERMINATION OF THE TORQUE REQUIRED FROM AN ELECTRIC DRIVE MACHINE OF A VEHICLE IN A DEGRADED TRAVEL MODE Technical field of the invention

The invention relates to land vehicles having a degraded mode of travel (or emergency mode, or in English "limp home mode"), and more precisely the control of the torque requested from the electric motive machine of the powertrain of such vehicles when the degraded travel mode is used.

State of the art

Certain land vehicles, possibly of the automobile type, include a powertrain (or GMP) comprising at least one electric driving machine and have a degraded travel mode (or emergency or even limp home mode) which is established in the event of detection of a problem within the GMP or the main (or traction) battery associated with this electric motor machine.

It is recalled that the degraded mode of travel consists of imposing a movement of the land vehicle at a speed less than or equal to a target speed, generally relatively low (typically between 15 km/h and 40 km/h), in order to avoid immediate immobilization and a priori not essential at the moment in question and therefore allow the driver to park his land vehicle in a secure location or to contact an after-sales service for an inspection.

Usually, so that the (land) vehicle can travel at the target speed in the degraded travel mode, the electric driving machine is asked for a torque (positive or negative) which is a function of the actual current speed of the vehicle only. For this purpose, a vehicle computer can, for example, store a table (or map) establishing a correspondence between speeds and torques, and obtained during testing or development phases.

A main disadvantage of this type of table (or map) lies in the fact that each torque associated with a speed has been determined for a vehicle traveling on a flat lane (or without slope) and with an average weight. Consequently, in the degraded travel mode the real speed of the vehicle varies (and therefore is not constant) depending at least on the slope of the traffic lane taken by the vehicle, which can hinder its driver, for example to park it. This results from the fact that when the vehicle is traveling on an uphill lane it needs more torque than is required of its electric prime mover to reach the target speed, whereas if the vehicle is traveling on a downhill lane it needs less torque than is required of its electric prime mover to reach the target speed. This disadvantage is all the more accentuated as the gap between the aforementioned average weight and the actual (current) weight of the vehicle is large.

The invention therefore aims in particular to improve the situation.

Presentation of the invention

To this end, it proposes in particular a control method intended to control the torque requested from an electric driving machine of a powertrain of a land vehicle having a degraded mode of movement at at least one target speed.

This control method is characterized by the fact that it comprises a step in which, when the mode is established, the requested torque is controlled as a function of a real speed of the land vehicle and a first value representative of a deviation between the target speed and the actual speed.

Thanks to this mode of controlling the torque requested from the electric driving machine, during the degraded travel mode, the real speed of the land vehicle is substantially constant whatever the slope of the traffic lane on which it is traveling and whatever its weight, which helps avoid disturbing the driver.

The control method according to the invention may include other characteristics which can be taken separately or in combination, and in particular:

- in its step we can determine an absolute value of the difference (between the target speed and actual speed), then, when this determined absolute value is greater than a first chosen threshold, we can determine a second value representative of a percentage difference between the target speed and actual speed, then the first value can be determined as a function of this second determined value, then the requested torque can be determined as a function of the actual speed and the first determined value;

- in the presence of the first option, in its step we can determine a first value equal to a result of a product between the second value and a chosen corrective coefficient;

- in the presence of the last sub-option, in its step the corrective coefficient can be chosen according to the real speed and/or the percentage of deviation;

- also in the presence of the last sub-option, in its step we can determine the requested torque by multiplying a theoretical torque associated with the real speed and the first value increased by a value equal to one;

- also in the presence of the first sub-option, in its step, when the determined absolute value becomes lower than the first threshold at an instant, we can determine a theoretical torque associated with the real speed and we can use this determined theoretical torque as that torque requested when a chosen duration has elapsed since this moment;

- in the presence of the last sub-option, in its step the duration can be chosen according to the real speed and/or the percentage of deviation.

The invention also proposes a computer program product comprising a set of instructions which, when executed by processing means, is capable of implementing the control method of the type of that presented above to control a torque requested from an electric driving machine of a powertrain of a land vehicle having a degraded mode of movement at at least one target speed.

The invention also proposes a control device intended to equip a land vehicle comprising a powertrain, comprising an electric motor machine capable of providing or recovering a requested torque, and a mode of movement degraded to at least one target speed.

This control device is characterized by the fact that it comprises at least one processor and at least one memory arranged to carry out the operations consisting, when the mode is established, of triggering a check of the requested torque as a function of an actual speed of the land vehicle and a first value representative of a difference between the target speed and the actual speed.

The invention also proposes a land vehicle, possibly of the automobile type, and comprising a powertrain, comprising an electric driving machine capable of providing or recovering a requested torque, a mode of movement degraded to at least one target speed, as well as a control device of the type presented above.

Brief description of the figures

Other characteristics and advantages of the invention will appear on examination of the detailed description below, and the appended drawings, in which:

schematically and functionally illustrates an exemplary embodiment of a land vehicle comprising an all-electric GMP and a supervision computer comprising a control device according to the invention,

schematically and functionally illustrates an exemplary embodiment of a GMP supervision calculator comprising an exemplary embodiment of a control device according to the invention, and

schematically illustrates an example of an algorithm implementing a control method according to the invention.

Detailed description of the invention

The invention aims in particular to propose a control method, and an associated DC control device, intended to allow control of the torque requested from an MME electric motor machine of a powertrain (or GMP) of a land vehicle V when the degraded travel mode is used (or established).

In what follows, we consider, by way of non-limiting example, that the land vehicle V is of the automobile type. This is for example a car, as illustrated in the . But the invention is not limited to this type of land vehicle. It concerns in fact any type of land vehicle comprising a powertrain (or GMP) comprising at least one electric driving machine and having a degraded mode of travel (or emergency or even limp home mode). Thus, it concerns, for example, utility vehicles, camper vans, minibuses, coaches, trucks, motorcycles, recreational vehicles (snowmobiles, karts), tracked vehicles, transport vehicles, roads, construction machinery, and agricultural machinery, for example.

Furthermore, we consider in what follows, by way of non-limiting example, that the land vehicle V comprises a powertrain (or GMP) of all-electric type (and therefore whose traction is ensured exclusively by at least one driving machine electric MME). But the GMP could be hybrid as long as the degraded mode of movement of its vehicle is carried out exclusively using the torque supplied or recovered by its electric motor.

It is recalled again that the degraded mode of movement consists of imposing a movement of the (land) vehicle V at a speed which is less than or equal to a target speed vc by controlling the torque cd requested from the electric motive machine MME. It should be noted that in the degraded travel mode it is possible to provide first and second target speeds respectively for forward and reverse travel.

We have schematically represented on the a (land) vehicle V comprising an electric GMP transmission chain and a DC control device according to the invention.

The transmission chain has a GMP which is, here, purely electric and therefore which includes, in particular, an electric driving machine MME, an AM motor shaft, a main (or traction) battery BP and an AT transmission shaft. Here we mean “electric driving machine” an electric machine arranged so as to provide or recover torque to move the vehicle V.

The operation of the GMP is supervised by a CS supervision computer.

The electric driving machine MME (here an electric motor) is coupled to the main (or traction) battery BP, in order to be supplied with electrical energy during a rolling phase, and to supply this main battery BP with current (electric ) regenerative during a regenerative braking phase. It is coupled to the AM motor shaft, to provide it with torque by rotational drive. This motor shaft AM is here coupled to a reduction gear RD which is also coupled to the transmission shaft AT, itself coupled to a first train T1 (here of wheels), preferably via a differential D1. The operation of the electric motor machine MME is controlled by a machine computer CM, and supervised by the supervision computer CS.

This first train T1 is here located in the front part PVV of the vehicle V. But in a variant this first train T1 could be the one which is here referenced T2 and which is located in the rear part PRV of the vehicle V.

The main BP battery can, for example, comprise electrical energy storage cells, possibly of the electrochemical type (for example of the lithium-ion (or Li-ion) or Ni-Mh or Ni-Cd type). Note that the cells (for storing electrical energy) can possibly be grouped in modules that are identical or different from each other.

For example, the main BP battery can be of the low voltage type (typically 450 V for illustration purposes). But it could be medium voltage or high voltage.

It will be noted that the electric driving machine MME can also be coupled to an electrical energy generator which can, for example, be a converter and responsible for supplying electrical energy, coming from the main battery BP and converted, to a very useful service battery. low voltage (especially for recharging) and an on-board network.

As mentioned above, the invention proposes in particular a control method intended to allow control of the torque cd requested from the electric motor machine MME when the degraded travel mode is used (or established).

This (control) method can be implemented at least partially by the DC control device (illustrated in Figures 1 and 2) which comprises for this purpose at least one processor PR1, for example a digital signal (or DSP ("DSP") Digital Signal Processor")) and at least one MD memory. This DC control device can therefore be produced in the form of a combination of electrical or electronic circuits or components (or “hardware”) and software modules (or “software”). For example, it can be a microcontroller.

The memory MD is live in order to store instructions for the implementation by the processor PR1 of at least part of the control process. The processor PR1 may include integrated (or printed) circuits, or several integrated (or printed) circuits connected by wired or non-wired connections. By integrated (or printed) circuit we mean any type of device capable of performing at least one electrical or electronic operation.

In the example illustrated non-limitingly in Figures 1 and 2, the DC control device is part of the GMP CS supervision computer. But this is not obligatory. Indeed, the DC control device could include its own calculator, or it could be part of the CM machine calculator, for example.

As illustrated without limitation on the , the (control) method, according to the invention, comprises at least one step 10-60 which is implemented each time the degraded travel mode is used (or established) in the vehicle V.

In this step 10-60 we (the DC control device) control the torque cd which is requested from the electric driving machine MME as a function of the real (current) speed vr of the vehicle V and a first value v1 which is representative of the difference ev between the (one) target speed (of the degraded travel mode) vc and this actual speed vr (i.e. ev = vc – vr). The actual speed vr is known permanently and precisely in the vehicle V, in particular by the supervision computer CS (for example it may be provided by an ESP/ABS type function (ESP: “Electronic Stability Program”), ABS : “Anti-Blocking System”).

This mode of controlling the requested torque cd is particularly advantageous because it makes it possible to have in the degraded mode of movement a real speed vr of the vehicle V which is substantially constant whatever the slope (upward or downward or zero) of the track. traffic on which it circulates and whatever its weight. Thus, the driver is not disturbed during the degraded mode of travel, and in particular when parking his vehicle V.

It will be understood that it is at least the processor PR1 and memory MD of the control device DC which are arranged to carry out the operations consisting, when the degraded travel mode is used, of controlling the torque cd which is requested from the electric motor machine MME as a function of the actual speed vr of the vehicle V and the first value v1 (representative of the difference ev between the target speed vc and the actual speed vr).

It will be noted that step 10-60 can include a sub-step 10 in which we (the DC control device) can start by determining an absolute value vae of the deviation ev (i.e. vae = |ev| = |vc - vr|), and a sub-step 20 in which we (the DC control device) can compare this determined absolute value vae to a first chosen threshold s1.

Then, when this determined absolute value vae is greater than the first threshold s1 chosen (i.e. vae > s1), we (the DC control device) can determine, in a sub-step 30 step 10-60, a second value v2 which is representative of a percentage difference pe between the target speed vc and the actual speed vr, then determine the first value v1 as a function of this second value v2.

For example, the deviation percentage pe can be equal to the ratio between the deviation ev and the target speed vc (i.e. pe = ev/vc = (vc-vr)/vc (in %)). We can therefore have a negative or positive deviation percentage pe depending on whether vc is less or greater than vr.

Also for example, the second value v2 can be equal to the deviation percentage pe (i.e. v2 = pe). But this is not obligatory.

Then, step 10-60 can include a sub-step 40 in which (the control device DC) can determine the requested torque cd as a function of the real speed vr and the first determined value v1 (function of v2) .

It will be noted that, when in sub-step 20 the determined absolute value vae is less than or equal to the first threshold s1 chosen (i.e. vae ≤ s1), we (the DC control device) can, for example, determine, in a sub-step -step 50 of step 10-60, a theoretical torque ct(vr) associated with the real speed vr and use this determined theoretical torque ct(vr) as the requested torque cd.

For example, the theoretical torque ct(vr) can be determined within a table (or map) establishing a correspondence between (real) speeds and (requested) torques, and determined during testing or implementation phases. to the point of a vehicle similar to that concerned (V) for an average on-board load. Note that we can use a table (or map) for forward travel and another table (or map) for reverse. It should also be noted that the (each) table (or map) can, for example, be stored in the DC control device. It should also be noted that instead of using a table (or map) we can use at least one mathematical formula (or equation) giving the requested torque cd as a function of the real speed vr.

It will also be noted that in substep 30 the control device DC) can, for example, determine a first value v1 which is equal to the result of the product between the second value v2 (here equal to the percentage of difference pe) and a chosen corrective coefficient cc (i.e. v1 = v2*cc (with here v2 = pe)). This corrective coefficient cc is intended to improve the precision of determining the requested torque cd. Note that the percentage of difference pe can be negative or positive, the first value v1 can therefore also be negative or positive.

For example, in substep 30 of step 10-60 the corrective coefficient cc can be chosen as a function of the real speed vr and/or the deviation percentage pe. In this case, we can, for example, use a law (or map) defining the evolution of the corrective coefficient cc as a function of the real speed vr and/or the percentage of deviation pe, and determined during test phases and development of a vehicle similar to that concerned (V).

But this is not obligatory. Indeed, the corrective coefficient cc can be fixed (or constant) whatever the real speed vr and/or whatever the percentage of deviation pe.

Also for example, in sub-step 40 of step 10-60, we (the control device DC) can, for example, determine the requested torque cd by multiplying a theoretical torque ct(vr) which is associated with the real speed vr and the first value v1 increased by a value equal to one (i.e. cd = ct(vr)*(1 + v1)). Thus, when the first value v1 is negative the requested torque cd is less than the theoretical torque ct(vr), which is adapted to the case where the vehicle V is traveling on a downward slope, and when the first value v1 is positive the requested torque cd is greater than the theoretical torque ct(vr), which is suitable for the case where the vehicle V is traveling on an upward slope.

As indicated above, the theoretical torque ct(vr) can be determined within the aforementioned table (or map), which establishes a correspondence between (real) speeds and (requested) torques. Note that here we can also use a table (or map) for forward travel and another table (or map) for reverse. Note also that instead of using a table (or map) we can here also use at least one mathematical formula (or equation) giving the requested torque cd as a function of the real speed vr.

It should also be noted that a return to a classic operating mode can be expected when the determined absolute value vae becomes permanently lower than the first threshold s1 again. For this purpose, when the determined absolute value vae becomes less than the first threshold s1 at a time t (i.e. vae ≤ s1 from t), we (the DC control device) can, for example, determine, in a sub- step 60 of step 10-60, a theoretical torque ct(vr) which is associated with the real speed vr (and presented above), and use this determined theoretical torque ct(vr) as the requested torque cd when a chosen duration dc has elapsed since this instant t. This amounts to performing substep 50 when the duration dc has elapsed. In order to implement this option we (the DC control device) can trigger a time delay having the first chosen duration dc as soon as the determined absolute value vae becomes less than the first threshold s1 at an instant t, and when this time delay expires (and that we always have vae < s1), we (the DC control device) uses the determined theoretical torque ct(vr) as the requested torque cd.

For example, in sub-step 60 of step 10-60 the duration dc can be chosen as a function of the real speed vr and/or the deviation percentage pe. In this case, we can, for example, use a law (or map) defining the evolution of the duration dc as a function of the real speed vr and/or the percentage of deviation pe, and determined during test phases and development of a vehicle similar to that concerned (V).

But this is not obligatory. Indeed, the duration dc can be fixed (or constant) whatever the real speed vr and/or whatever the percentage of deviation pe.

The degraded travel mode (or Limp Home mode) is inhibited when the problem initially detected and which triggered its establishment is no longer present, for example after the driver has turned off the ignition of vehicle V and then restarted the ignition of vehicle V .

But, we can also provide an operating option in which we inhibit (at least) temporarily the degraded mode of movement when the driver presses in a certain way on the brake pedal PF of vehicle V. For example, we can provide a interval of percentage of depression of the brake pedal PF which induces a dosage of the requested torque cd, and beyond this interval the degraded travel mode is temporarily inhibited. For example, this interval can include the first ten percent of depression of the PF brake pedal, and its upper and lower limits are hereinafter called second s2 and third s3 thresholds (with s3 different from 0%).

In this case, we can, for example, have the operation described below.

When the PF brake pedal is completely released (0%), the control method described above is implemented. When the PF brake pedal is pressed by a percentage which is greater than the second threshold s2, the degraded travel mode is temporarily inhibited. When the brake pedal PF is pressed by a percentage ppf which is between the second s2 and third s3 thresholds (i.e. s2 < ppf < s3), we (the DC control device) can, for example, determine the requested torque cd using the formula: cd = ct(vr)*(1+v1)*cc'. cc’ is another corrective coefficient which can, for example, be determined by the DC control device using the formula: cc’ = (s2 – ppf)/s2.

Note also, as illustrated non-limitatively in the , that the supervision computer CS (or the computer of the DC control device) can also include a mass memory MM1, in particular to store the tables (or maps), the real speeds and the possible ppf percentages of depression of the pedal PF brake, as well as any intermediate data involved in all its calculations and processing. Furthermore, this CS supervision calculator (or the DC control device calculator) can also include an IE input interface for receiving at least the actual speeds and any ppf percentages, to use them in calculations or processing, possibly after having formatted and/or demodulated and/or amplified them, in a manner known per se, by means of a digital signal processor PR2. In addition, this supervision computer CS (or the computer of the DC control device) can also include an output interface IS, in particular to deliver each requested torque cd which must control the electric motor machine MME in real time during the degraded travel mode. , and a possible message (or order) for temporary inhibition of the degraded travel mode.

It will also be noted that the invention also proposes a computer program product (or computer program) comprising a set of instructions which, when executed by processing means of the electronic circuit (or hardware) type, such as for example the processor PR1 is capable of implementing the control method described above to control the torque cd requested from the electric driving machine MME of the GMP of the vehicle V during the degraded travel mode.

Claims (10)

Method for controlling the torque requested from an electric motor machine (MME) of a powertrain of a land vehicle (V) having a degraded mode of movement at at least one target speed, characterized in that it comprises a step (10-60) in which, when said mode is established, said requested torque is controlled as a function of a real speed of said land vehicle (V) and a first value representative of a difference between said target speed and speed real. Method according to claim 1, characterized in that in said step (10-60) an absolute value of said deviation is determined, then, when said determined absolute value is greater than a first chosen threshold, a second value representative of a percentage difference between said actual speed and target speed, then, then the first value is determined as a function of said second determined value, then said requested torque is determined as a function of said actual speed and said first determined value. Method according to claim 2, characterized in that in said step (10-60) a first value equal to a result of a product between said second value and a chosen corrective coefficient is determined. Method according to claim 3, characterized in that in said step (10-60) said corrective coefficient is chosen as a function of said real speed and/or of said deviation percentage. Method according to claim 3 or 4, characterized in that in said step (10-60) said requested torque is determined by multiplying a theoretical torque associated with said actual speed and said first value increased by a value equal to one. Method according to one of claims 2 to 4, characterized in that in said step (10-60), when said determined absolute value becomes lower than said first threshold at an instant, a theoretical torque associated with said real speed is determined and we uses this determined theoretical torque as the requested torque when a chosen duration has elapsed since said instant. Method according to claim 6, characterized in that in said step (10-60) said duration is chosen as a function of said actual speed and/or of said deviation percentage. Computer program product comprising a set of instructions which, when executed by processing means, is capable of implementing the control method according to one of claims 1 to 7 to control a torque requested at a electric motive machine (MME) of a powertrain of a land vehicle (V) having a degraded mode of movement at at least one target speed. Control device (DC) for a land vehicle (V) comprising a powertrain, comprising an electric motor machine (MME) capable of supplying or recovering a requested torque, and a mode of movement degraded to at least one target speed, characterized in that it comprises at least one processor (PR1) and at least one memory (MD) arranged to carry out the operations consisting, when said mode is established, of triggering a control of said requested torque as a function of an actual speed of said land vehicle (V) and a first value representative of a difference between said target speed and actual speed. Land vehicle (V) comprising a powertrain, comprising an electric motor machine (MME) capable of providing or recovering a requested torque, and a mode of movement degraded to at least one target speed, characterized in that it further comprises a control device (DC) according to claim 9.