DECELERATION CONTROL BY RECOVERY OF RECYCLING TORQUE IN A LAND VEHICLE

Abstract

A control method is implemented in a land vehicle and comprising a powertrain comprising at least one electric motor capable of recovering a regenerative braking torque, defined by a first deceleration setpoint depending on a second deceleration setpoint representative of a deceleration desire of the driver and limited by a third deceleration setpoint, to decelerate the vehicle. This method comprises a step (10-20) in which, in the presence of second and third deceleration setpoints, a fourth deceleration setpoint is determined as a function of the third deceleration setpoint and a chosen minimum evolution gradient of the latter, then the first deceleration setpoint is chosen from the largest of the second and fourth deceleration setpoints. Figure 3

Description

Title of the invention: CONTROL OF DECELERATION BY RECOVERY OF RECYCLING TORQUE IN A LAND VEHICLE Technical field of the invention

[0001] The invention relates to land vehicles comprising a powertrain comprising at least one electric motor capable of recovering a regenerative braking torque, and more precisely the control of the deceleration of such vehicles by recovery of regenerative braking torque. State of the art

[0002] Certain land vehicles, possibly of the automobile type, comprise a powertrain (or GMP) comprising at least one electric motor associated with a main battery (or "power" or even "traction") and capable of recovering a regenerative braking torque to decelerate them. It will be noted that this recovered regenerative braking torque is usually transformed by the electric motor into a recharging current intended to recharge the main battery, when this proves possible.

[0003] It should also be noted that the GMP can be all electric or hybrid (thermal and electric).

[0004] Furthermore, the term "electric motor" here means an electric machine arranged to provide (positive) torque to move its vehicle when it is supplied with electrical energy and to recover (negative) regenerative braking torque to decelerate the vehicle. It will be noted that in a braking phase of a vehicle, the electric motor can provide full braking, or participate in braking in combination with the braking system of its (land) vehicle.

[0005] Generally, the regenerative braking torque, which an electric motor of a GMP must recover, is defined by a first deceleration instruction which is a function of a second deceleration instruction representative of the deceleration desire of the driver of the vehicle and limited by a third deceleration instruction which varies over time.

[0006] In some GMPs, the first deceleration instruction is equal to the greater of the second and third deceleration instructions. In this case, the torque that is requested by the driver to decelerate his vehicle (and which is represented by the second (negative) deceleration instruction) is limited by the capacity of the GMP (represented by the third (negative) deceleration instruction). It will be noted that this The capacity of the GMP depends on various parameters, such as (but not limited to) the capacity of the main battery being recharged, mechanical losses, and efficiency.

[0007] In the presence of such a method of determining the first deceleration setpoint, the upward (and therefore less negative) variations of the third deceleration setpoint can cause a reduction in the deceleration, and the downward (and therefore more negative) variations of the third deceleration setpoint can cause an increase in the deceleration without the driver requesting it. However, such deceleration variations prevent good control of the vehicle and degrade the driving pleasure of the vehicle.

[0008] It will be noted that the upward variations in the third deceleration setpoint are inevitably applied to the regenerative braking torque that the electric motor must recover, and therefore the loss of deceleration is possibly unpleasant but inevitable.

[0009] The invention therefore aims in particular to improve the situation in the presence of downward variations in the third deceleration setpoint (for example resulting from an increase in the recharging capacity of the main battery). Presentation of the invention

[0010] It proposes in particular for this purpose a control method intended to be implemented in a land vehicle and comprising a powertrain comprising at least one electric motor capable of recovering a regenerative braking torque, defined by a first deceleration instruction depending on a second deceleration instruction representative of a desire to decelerate by a driver of the vehicle and limited by a third deceleration instruction, to decelerate the vehicle.

[0011] This control method is characterized by the fact that it comprises a step in which, in the presence of second and third deceleration instructions, a fourth deceleration instruction is determined as a function of the third deceleration instruction and a chosen minimum evolution gradient of the latter, then the first deceleration instruction is chosen from the largest of the second and fourth deceleration instructions.

[0012] Thanks to the invention, it is now possible to reduce, or even eliminate, the influence of downward variations in the third deceleration setpoint, which makes it possible to improve the control and driving pleasure of the vehicle.

[0013] The control method according to the invention may include other characteristics which may be taken separately or in combination, and in particular:

[0014] - in its step, we can determine the fourth deceleration instruction in choosing the largest of the third deceleration instruction and the minimum evolution gradient;

[0015] - in its step, we can determine the minimum evolution gradient at an instant t in function of a difference between first and fourth deceleration instructions obtained previously at a time t-1;

[0016] - in the presence of the last option, in its step, the greater the difference, the more the corresponding minimal evolution gradient can be strongly negative, and the smaller the difference the weaker the corresponding minimal evolution gradient can be;

[0017] - also in the presence of the last option, in its step, we can determine the minimum evolution gradient at time t as a function of the current speed of the vehicle;

[0018] - in the presence of the last sub-option, in its step, we can determine the minimum evolution gradient in a table establishing a correspondence between torques, vehicle speed and difference between first and fourth deceleration instructions, and minimum evolution gradients, and as a function of the difference determined at time t-1 and the current speed of the vehicle.

[0019] The invention also provides a computer program product comprising a set of instructions which, when executed by processing means, is capable of implementing a control method of the type presented above, in a land vehicle and comprising a powertrain comprising at least one electric motor capable of recovering a regenerative braking torque, defined by a first deceleration instruction depending on a second deceleration instruction representative of a desire to decelerate by a driver of the vehicle and limited by a third deceleration instruction, to decelerate the vehicle, to control the deceleration by recovery of regenerative braking torque.

[0020] The invention also proposes a control device intended to equip a land vehicle and comprising a powertrain comprising at least one electric motor capable of recovering a regenerative braking torque, defined by a first deceleration instruction depending on a second deceleration instruction representative of a desire to decelerate by a driver of the vehicle and limited by a third deceleration instruction, to decelerate the vehicle.

[0021] 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, in the presence of second and third deceleration instructions, in determining a fourth deceleration instruction as a function of the third deceleration instruction and a chosen minimum evolution gradient of the latter, then in choosing the first deceleration instruction from the largest of the second and fourth deceleration instructions.

[0022] The invention also proposes a land vehicle, possibly of the automobile type, and comprising, on the one hand, a powertrain comprising at least one electric motor capable of recovering a regenerative braking torque, defined by a first deceleration instruction depending on a second deceleration instruction representative of a desire to decelerate by a driver of the vehicle and limited by a third deceleration instruction, to decelerate the vehicle, and, on the other hand, a control device of the type presented above. Brief description of the figures

[0023] Other characteristics and advantages of the invention will appear on examining the detailed description below, and the appended drawings, in which:

[0024] [Fig. 1] schematically and functionally illustrates an exemplary embodiment of a land vehicle comprising a GMP transmission chain with two electric motors associated with a main battery and supervised by a supervision computer, and a control device according to the invention,

[0025] [Fig.2] schematically and functionally illustrates an exemplary embodiment of a machine calculator associated with one of the electric motor machines of the GMP of [Fig.l] and comprising an exemplary embodiment of a control device according to the invention,

[0026] [Fig.3] schematically illustrates an example of an algorithm implementing a control method according to the invention, and

[0027] [Fig.4] schematically illustrates within a diagram examples of time evolutions of first (cdl), second (cd2), third (cd3) and fourth (cd4) deceleration instructions (in Nm) in the presence of the invention. Detailed description of the invention

[0028] The invention aims in particular to propose a control method, and an associated control device DS, intended to enable control of the deceleration of a land vehicle V by recovery of regenerative braking torque by an electric motor machine MM2 of its powertrain (or GMP).

[0029] In the following, it is considered, by way of non-limiting example, that the land vehicle V is of the automobile type. It is for example a car, as illustrated in [Fig.l]. But the invention is not limited to this type of land vehicle. It relates in fact to any type of land vehicle comprising a GMP transmission chain comprising at least one electric motor associated with a rechargeable battery and capable of recovering regenerative braking torque to decelerate it. Thus, it relates to utility vehicles, camper vans, minibuses, coaches, trucks, motorcycles, road machinery, construction machinery, agricultural machinery, and recreational vehicles (karts), for example.

[0030] Furthermore, it is considered in the following, by way of non-limiting example, that the land vehicle V comprises a transmission chain with a powertrain (or GMP) of the all-electric type (and therefore whose drive is provided exclusively by at least one electric motor MMj). But the GMP could be of the hybrid type (thermal and electric).

[0031] [Fig.l] schematically shows a (land) vehicle V comprising a GMP transmission chain with first MM1 (j = 1) and second MM2 (j = 2) electric motors, a supervision computer CS, an on-board network RB, a service battery BS, a main battery BP, a converter CV, and a control device DC2 according to the invention.

[0032] The on-board network RB is an electrical power supply network to which electrical (or electronic) equipment (or components) that consume electrical energy are coupled.

[0033] The service battery BS is responsible for supplying electrical energy to the on-board network RB, in addition to that supplied by the CV converter powered by the main battery BP via a main electrical circuit, and sometimes instead of this CV converter. For example, this service battery BS can be arranged in the form of a very low voltage type battery (typically 12 V, 24 V or 48 V). It is rechargeable at least by the CV converter. It is considered in the following, by way of non-limiting example, that the service battery BS is of the 12 V Lithium-ion type.

[0034] The main electrical circuit (or "high voltage" or "power") is connected, on the one hand, to the main battery BP via an interface device, and, on the other hand, to electronic equipment, such as for example the CV converter and the first MM1 and second MM2 electric motors. It also allows the main battery BP to be recharged by an external power source and temporarily coupled to a charging connector of the vehicle V.

[0035] The transmission chain has a GMP which is here purely electric and which comprises, in particular, the first electric motor MM1, a first motor shaft AMI, a first transmission shaft ATI, the second electric motor MM2, a coupling device DC2, a second motor shaft AM2, and a second transmission shaft AT2.

[0036] Here, the term “electric motor” means an electric machine arranged so as to provide (positive) torque to move the vehicle V when it is supplied with electrical energy by the main battery BP, and possibly to recover (negative) torque in the transmission chain during regenerative braking phases to decelerate the vehicle V.

[0037] It will be noted that the GMP could comprise only the first electric motor MM1 (providing torque for at least one train of the vehicle V) or only the second electric motor MM2 (providing torque for at least one other train of the vehicle V).

[0038] The operation of the transmission chain (and therefore of the GMP) is supervised by a CS supervision computer.

[0039] The first electric motor MM1 (here an electric motor) is coupled to the main battery BP via the main electrical circuit, at least in order to be supplied with electrical energy.

[0040] Furthermore, this first electric motor MM1 is coupled to the first motor shaft AMI, to provide it with torque by rotational drive. This first motor shaft AMI is here coupled to a first reducer RDI which is also coupled to the first transmission shaft ATI, itself coupled to a first train T1 (here of wheels), preferably via a differential DV.

[0041] 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.

[0042] The operation of the first electric motor MM1 is controlled by a first machine computer CM1, and supervised by the supervision computer CS.

[0043] The second electric motor MM2 (here an electric motor) is coupled to the main battery BP via the main electrical circuit, in order to be supplied with electrical energy and to supply this main battery BP with electrical energy during a regenerative braking phase.

[0044] Furthermore, the second electric motor MM2 is coupled to the second motor shaft AM2, to provide it with torque by rotational drive. This second motor shaft AM2 is here coupled to a second reducer RD2 which can be coupled, here via a coupling device DC1, to the second transmission shaft AT2, itself coupled, here, to the second train T2 (here of wheels), preferably via a differential DR.

[0045] During a regenerative braking phase, the second electric motor MM2 can recover a regenerative braking torque cfr, defined by a first deceleration setpoint cdl which is a function of a second deceleration setpoint cd2 representative of the deceleration desire of the driver of the vehicle V, to decelerate the latter (V). This second deceleration setpoint cd2 is limited by a third deceleration setpoint cd3 which varies over time because it represents the current capacity of the GMP (a function, for example, of the capacity currently being recharged of the main battery BP, of mechanical losses, and of efficiencies).

[0046] It will be noted that the regenerative braking torque cfr recovered by the second machine electric motor MM2 is transformed by the latter (MM2) into charging current intended to recharge the main battery BP, when this proves possible.

[0047] The operation of the second electric motor MM2 is controlled by a second machine computer CM2, and supervised by the supervision computer CS.

[0048] The coupling device DC1 can be placed in coupled and decoupled states, depending on a state setpoint generated by the GMP supervision computer CS. For example, this coupling device DC1 can be a dog clutch. But this is not an obligation.

[0049] The CV converter is also responsible, here, during the driving phases of the vehicle V for converting part of the electric current stored in the main battery BP to supply converted electric current to the on-board network RB and the service battery BS (to recharge it). It will be noted, as illustrated non-limitingly in [Fig.l], that the CV converter can be part of a charger CH.

[0050] The main battery (or power or traction battery) BP may, for example, comprise electrical energy storage cells, possibly electrochemical (for example of the lithium-ion (or Li-ion) or Ni-Mh or Ni-Cd type). Also for example, the main battery BP may be of the low voltage type (typically 450 V or 600 V for illustrative purposes). But it could be of the medium voltage or high voltage type.

[0051] It will also be noted that in the example illustrated non-limitingly in [Fig.l] the vehicle V also comprises a distribution box BD to which the service battery BS, the converter CV and the on-board network RB are coupled. This distribution box BD is responsible for distributing in the on-board network RB the electrical energy stored in the service battery BS or produced by the converter CV, for the supply of the electrical components (or equipment) coupled to the on-board network RB according to power supply requests received (in particular from the supervision computer CS of the GMP).

[0052] It will also be noted that the vehicle V has a current speed vev which is estimated, preferably periodically. For example, this period may be between 10 milliseconds and 100 milliseconds. As an illustrative example, the period may be equal to 50 milliseconds.

[0053] As mentioned above, the invention proposes in particular a control method intended to allow the control of the deceleration of the vehicle V by recovery of regenerative braking torque cfr by its electric motor MM2.

[0054] This (control) method can be implemented at least partially by the control device DS (illustrated at least partially in Figures 1 and 2) which comprises for this purpose at least one processor PR1, for example a digital signal processor (or DSP ("Digital Signal Processor")), and at least one MD memory. This DS 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.

[0055] The memory MD is RAM in order to store instructions for the implementation by the processor PR1 of at least part of the control method. The processor PR1 may comprise integrated (or printed) circuits, or several integrated (or printed) circuits connected by wired or wireless connections. An integrated (or printed) circuit is understood to mean any type of device capable of carrying out at least one electrical or electronic operation.

[0056] In the example illustrated non-limitingly in Figures 1 and 2, the control device DS is part of the second machine computer CM2 (associated with the second electric motor machine MM2). But this is not obligatory. Indeed, the control device DS could comprise its own dedicated computer, or could be part of another computer of the vehicle V, such as for example the supervision computer CS.

[0057] As illustrated non-limitingly in [Fig. 3], the (monitoring) method, according to the invention, comprises a step 10-20 which is implemented each time the vehicle V must be subject to deceleration by recovery of regenerative braking torque cfr by its second electric motor MM2, and therefore there is a second deceleration instruction cd2 (representative of the driver's desire to decelerate) and a third deceleration instruction cd3 limiting this second deceleration instruction cd2.

[0058] Step 10-20 of the method comprises a sub-step 10 in which, in the presence of second cd2 and third cd3 deceleration instructions, a fourth deceleration instruction cd4 is determined (for example the control device DC2) as a function of the third deceleration instruction cd3 and a minimum evolution gradient gc chosen for the latter (cd3).

[0059] Step 10-20 of the method also comprises a sub-step 20 in which one (for example the control device DC2) chooses the first deceleration setpoint cdl (which defines the regenerative braking torque cfr to be recovered by the second electric motor MM2) from among the largest of the second cd2 and fourth cd4 deceleration setpoints, i.e. cdl = max(cd2; cd4).

[0060] It will be understood that the fourth deceleration instruction cd4 determined constitutes a filtered version of the third deceleration instruction cd3 intended to reduce, and if possible eliminate, the influence of the downward variations (and therefore the most negative) of the third deceleration instruction cd3.

[0061] Thanks to this new method of determining the first deceleration instruction cdl, which tends to reduce, or even eliminate, the influence of downward variations in the third deceleration instruction cd3, we reduce, or even prevent, increases in deceleration that are not requested by the driver. This results in an improvement in the control of the vehicle V and the driving pleasure of the vehicle V.

[0062] For example, in sub-step 10 of step 10-20 one (for example the control device DC2) can determine the fourth deceleration setpoint cd4 by choosing the largest of the third deceleration setpoint cd3 and the minimum evolution gradient gc, i.e. cd4 = max(cd3; gc). We therefore have a fourth deceleration setpoint cd4 which is a gradient limitation function having as a parameter, in particular, the minimum evolution gradient gc which limits the influence of the downward variations of the third deceleration setpoint cd3.

[0063] Also for example, in sub-step 10 of step 10-20 one (for example the control device DC2) can determine the minimum evolution gradient gc(t) at a time t as a function of the difference dcc(tl) between the first cdl(tl) and fourth cd4(tl) deceleration instructions obtained previously at time t-1. Here a feedback loop is used in which one can determine at the first time t=l the minimum evolution gradient gc(t=l) by using a first deceleration instruction cdl(t=0) chosen from the largest of the second cd2(t=0) and third cd3(t=0) deceleration instructions at time t=0, i.e. cdl(t=0) = max(cd2(t=0); cd3(t=0)).

[0064] Also for example, in sub-step 10 of step 10-20, the greater the difference dcc, the more the corresponding minimum evolution gradient gc can be strongly negative. Conversely, the smaller the difference dcc, the more the corresponding minimum evolution gradient gc can be weakly negative. The law of evolution of the minimum evolution gradient gc as a function of the difference dcc can be of different types. For example, it can be linear or quadratic or even exponential. It will be noted that it is possible to use a first law of evolution of a first type for increasing differences dcc, and a second law of evolution of a second type for decreasing differences dcc.

[0065] Also for example, in sub-step 10 of step 10-20 one (for example the control device DC2) can determine the minimum evolution gradient gc at time t as a function in addition of the current speed vev of the vehicle V. Indeed, the greater the current speed vev, the more one can use a strongly negative minimum evolution gradient gc. The fact of finding a “significant” deceleration is in fact less troublesome at high speed than at low speed, because at low speed one generally seeks to control the position of the vehicle V (for example to stop it on the line of a STOP) more than at high speed.

[0066] Also for example, in sub-step 10 of step 10-20 we (for example the control device DC2) can determine the minimum evolution gradient gc in a correspondence table (or mapping) as a function of the difference dcc(tl) determined at time t-1 and the current speed vev of the vehicle V. This correspondence table establishes a correspondence between torques, vehicle speed and difference between first and fourth deceleration instructions, and minimum evolution gradients. It will be understood that the minimum evolution gradient which corresponds to the difference dcc(tl) and the current speed vev is determined in this correspondence table, and that this minimum evolution gradient is the minimum evolution gradient gc(t). This correspondence table can be determined in the laboratory or during a test or development phase of a vehicle similar to the vehicle V.

[0067] [Fig. 4] schematically illustrates a diagram showing an example of respective time evolutions of first cdl (k = 1), second cd2 (k = 2), third cd3 (k = 3) and fourth cd4 (k = 4) deceleration instructions (in Nm) in the presence of the invention, with a materialization of some minimal evolution gradients gc. As can be seen by observing the time evolution of the first deceleration instruction cdl, the fourth deceleration instruction cd4 makes it possible to significantly reduce the influence of the downward variations of the third deceleration instruction cd3.

[0068] It will also be noted, as illustrated non-limitingly in [Fig. 2], that the second machine computer CM2 (or the computer of the control device DS) can also comprise a mass memory MEM, in particular for storing each second deceleration instruction cd2, each third deceleration instruction cd3 and each possible current speed vev, as well as any intermediate data involved in all its calculations and processing operations. Furthermore, this second machine computer CM2 (or the computer of the control device DS) can also comprise an input interface IE for receiving at least each second deceleration instruction cd2, each third deceleration instruction cd3 and each possible current speed vev, to use them in calculations or processing operations, 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 second machine calculator CM2 (or the calculator of the control device DS) can also include an output interface IS, in particular to deliver a message containing the first determined deceleration instruction cdl.

[0069] 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 deceleration by recovery of regenerative braking torque in vehicle V.

Claims

Claims

1. Control method for a land vehicle (V) and comprising a powertrain comprising at least one electric motor (MMj) capable of recovering a regenerative braking torque, defined by a first deceleration setpoint depending on a second deceleration setpoint representative of a desire to decelerate of a driver of said vehicle (V) and limited by a third deceleration setpoint, to decelerate said vehicle (V), characterized in that it comprises a step (10-20) in which, in the presence of second and third deceleration setpoints, a fourth deceleration setpoint is determined as a function of said third deceleration setpoint and a chosen minimum evolution gradient of the latter, then said first deceleration setpoint is chosen from the largest of said second and fourth deceleration setpoints.

2. Method according to claim 1, characterized in that in said step (10-20) said fourth deceleration setpoint is determined by choosing the largest of said third deceleration setpoint and said minimum evolution gradient.

3. Method according to claim 1 or 2, characterized in that in said step (10-20) said minimum evolution gradient is determined at a time t as a function of a difference between first and fourth deceleration instructions obtained previously at a time t-1.

4. Method according to claim 3, characterized in that in said step (10-20) the greater said difference, the more strongly negative said corresponding minimum evolution gradient is, and the smaller said difference, the more weakly negative said corresponding minimum evolution gradient is.

5. Method according to claim 3 or 4, characterized in that in said step (10-20) said minimum evolution gradient is determined at said instant t as a function, in addition, of a current speed of said vehicle (V).

6. Method according to claim 3 or 4 taken in combination with claim 5, characterized in that in said step (10-20) said minimum evolution gradient is determined in a table establishing a correspondence between torques, vehicle speed and difference between first and fourth deceleration instructions, and minimum evolution gradients, and as a function of said difference determined at said instant t-1 and at said current speed of said vehicle (V).

7. 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 6, in a land vehicle (V) and comprising a powertrain comprising at least one electric motor (MMj) capable of recovering a regenerative braking torque, defined by a first deceleration instruction depending on a second deceleration instruction representative of a desire to decelerate by a driver of said vehicle (V) and limited by a third deceleration instruction, to decelerate said vehicle (V), to control the deceleration by recovery of regenerative braking torque.

8. Control device (DC2) for a land vehicle (V) and comprising a powertrain comprising at least one electric motor (MMj) capable of recovering a regenerative braking torque, defined by a first deceleration setpoint depending on a second deceleration setpoint representative of a desire to decelerate by a driver of said vehicle (V) and limited by a third deceleration setpoint, to decelerate said vehicle (V), characterized in that it comprises at least one processor (PR1) and at least one memory (MD) arranged to carry out the operations consisting, in the presence of second and third deceleration setpoints, in determining a fourth deceleration setpoint as a function of said third deceleration setpoint and a chosen minimum evolution gradient of the latter,then choosing said first deceleration instruction from the largest of said second and fourth deceleration instructions.,

9. Land vehicle (V) comprising a powertrain comprising at least one electric motor (MMj) capable of recovering a regenerative braking torque, defined by a first deceleration instruction depending on a second deceleration instruction representative of a desire to decelerate by a driver of said vehicle (V) and limited by a third deceleration instruction, to decelerate said vehicle (V), characterized in that it further comprises a control device (DS) according to claim 8.

10. Vehicle according to claim 9, characterized in that it is of the automobile type.

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