METHOD FOR CONTROLLING THE WHEEL ASSEMBLY OF A MOTOR VEHICLE POWERTRAIN

Abstract

One aspect of the invention relates to a method 100 for controlling the front and rear wheel assemblies of a vehicle's powertrain, comprising the steps of: Determining 101 a driving torque setpoint; Determining 102 a distribution ratio of said driving torque setpoint between said front and rear wheel assemblies; Determining 103 a derivative of said distribution ratio; Determining 104 a derivative of a torque gradient to be applied to said front wheel assembly and a derivative of a torque gradient to be applied to said rear wheel assembly as a function of said setpoint, said ratio, and said derivative of said ratio determined; Filtering 105 said derivatives of a torque gradient; Controlling 106 the torques applied to said front and rear wheel assemblies as a function of said filtered derivatives of a torque gradient. Figure 4

Description

Title of the invention: METHOD FOR CONTROLLING WHEEL ASSEMBLIES OF A POWERTRAIN OF A MOTOR VEHICLE

[0001] The present invention relates to a method for controlling a front wheel set and a rear wheel set of a powertrain of a four-wheel drive motor vehicle. The invention finds an application with a powertrain of a four-wheel drive motor vehicle of the electric, hybrid or thermal type.

[0002] In a manner known per se, a 4x4 type hybrid powertrain may comprise a front wheel set comprising at least one drive member, namely a heat engine and / or an electric traction motor. A coupling and decoupling device makes it possible to selectively couple and decouple the heat engine and / or the electric traction motor with the front wheel set. The coupling and decoupling device takes the form, for example, of a gearbox, in particular of the automatic type. In order to be able to isolate the electric traction motor from the heat engine during a pure electric driving mode, a clutch is interposed between the heat engine and the electric traction motor.

[0003] Furthermore, a rear wheel set may comprise a second electric traction motor associated with a speed reducer and a device for coupling and decoupling the second electric traction motor with the rear wheels of the vehicle. The coupling and decoupling device may consist of a dog clutch device, a clutch or a gearbox.

[0004] In order to reduce the oscillations of the powertrain when passing through the mechanical clearances present in the powertrain, it is known to implement a preventive comfort filter function making it possible to filter the raw driver torque setpoint. This function therefore has a preventive correction action on the oscillations generated by this passage of the mechanical clearances. This function makes it possible to significantly improve the longitudinal comfort of the motor vehicle.

[0005] More particularly, as illustrated in [Fig.l], in order to reduce this oscillation phenomenon, it is known to distribute a torque setpoint from the driver 1 making it possible to obtain a desired acceleration of the vehicle into an unfiltered torque setpoint from the front wheel set 2 and an unfiltered torque setpoint from the rear wheel set 3. The unfiltered torque setpoint from the front wheel set 2 is then filtered by means of a first preventive approval filter 4 and the torque setpoint from the unfiltered rear wheel set 3 is also filtered by means of a second preventive approval filter 5.

[0006] According to this implementation, the distribution of the torque setpoint of the driver 1 is carried out upstream of the first and second preventive approval filters 4, 5.

[0007] When the driver's torque demand is constant, it is possible that the torque distribution between the front wheel set and the rear wheel set is automatically modified by a vehicle computer, for example following overheating of the front electric motor. In such a situation, an inconvenience may be perceived by the driver due to different torque dynamics between the front wheel set and the rear wheel set. This inconvenience may be generated by the vehicle slowing down on a flat road while the driver requests a constant torque. This intervention by the computer may be intrusive to the driver.

[0008] [Fig.2] illustrates this phenomenon. Curve C6 illustrates the driver's torque setpoint. Curve C7 illustrates the torque applied to the front wheelset and curve C8 illustrates the torque applied to the rear wheelset. Curve C9 represents the vehicle speed. Thus, we can see a change in the vehicle speed while the driver's torque setpoint is constant.

[0009] More specifically, when changing the torque distribution 80Nm => 20Nm on the front wheel set and 20Nm => 80Nm on the rear wheel set, it can be seen that the torque dynamics on the front wheel set are faster than on the rear wheel set. In other words, the torque change made on the front wheel set is faster than the torque change made on the rear wheel set. This phenomenon illustrated by T1 can be explained by the fact that it is not the same electric motor or by the mechanical dispersion. These different torque dynamics have an impact on the speed of the vehicle even though this is not the driver's intention.

[0010] The aim of the invention is in particular to propose a method making it possible to avoid this type of inconvenience due to a change in torque distribution between the front wheel set and the rear wheel set.

[0011] In this context, the invention thus relates, in its broadest acceptance, to a method for controlling a front wheel set and a rear wheel set of a powertrain of a four-wheel drive motor vehicle comprising the steps, executed by powertrain control means, of: • Determining a torque setpoint from the driver; • Determine a distribution ratio of said driver torque instruction between the front wheel set and the rear wheel set; • Determine a derivative of said distribution ratio; • Determine a derivative of a torque gradient to be applied to the front wheel set and a derivative of a torque gradient to be applied to the rear wheel set, said derivative of a torque gradient to be applied to the front wheel set and said derivative of a torque gradient to be applied to the rear wheel set being a function of said driver torque setpoint, said distribution ratio and said derivative of the distribution ratio determined; • Filtering said derivative of a torque gradient to be applied to the front wheel set and said derivative of a torque gradient to be applied to the rear wheel set to avoid oscillations on the front and rear wheel sets; • Control a torque applied to the front wheel set as a function of said derivative of a torque gradient to be applied to the filtered front wheel set and a torque applied to the rear wheel set as a function of said derivative of a torque gradient to be applied to the filtered rear wheel set.

[0012] Torque dynamics represents the ability of a motor to provide an incremental torque gradient (i.e. motor) or a decremental torque gradient (i.e. motor brake). Torque dynamics therefore vary from one motor to another either because it is not the same motor or because there is mechanical dispersion. Thanks to the step of determining the derivatives of a torque gradient to be applied to the front and rear wheel sets, a control of the torque dynamics of each wheel set prior to the filtering step is carried out with the objective of respecting the driver's torque setpoint. Thus, the desired torque requested by the driver is respected.More particularly, thanks to the invention, if the driver's torque setpoint is constant, the road is flat and the torque distribution is modified, no modification of the vehicle speed will occur despite the change in torque distribution between the front and rear wheel sets.

[0013] In addition to the characteristics which have just been mentioned in the preceding paragraph, the method according to the invention may have one or more complementary characteristics among the following, considered individually or according to all technically possible combinations.

[0014] According to a non-limiting aspect of the invention, the derivative of a torque gradient to be applied to the front wheel set is defined by the following function: Here r,cons . . ^'ons . ^ams . ^tcons — A XL + A XL • With : * CæyS = Derivative of a torque gradient to be applied to the front wheel set; • Cœns _ driver COUpie instruction; . £ <cons = Dérivée d’un couple motopropulseur prédéterminé ; , jçcons _ Ratjo the distribution of said torque instruction from the driver to be applied to the front wheel set; . j^cons _ Derivative of said distribution ratio of said driver torque instruction to be applied to the front wheel set.

[0015] According to a non-limiting aspect of the invention, the derivative of a torque gradient to be applied to the rear wheel set is defined by the following function: = _ x + _ Kc^ x • With : qCO!1S= Derivative of a torque gradient to be applied to the rear wheel set. back ; • Q«>ns _ Qons jgnc Driver's COUPING; . ç,œns _ Derived from a predetermined powertrain torque; • tokens _ Distribution ratio of said driver torque instruction to be applied to the front wheel set; • j^cons _ Derivative of said distribution ratio of said driver torque instruction to be applied to the front wheel set.

[0016] According to a non-limiting aspect of the invention, the derivative of a torque gradient to be applied to the front wheel set and the derivative of a torque gradient to be applied to the rear wheel set determined are limited by predetermined powertrain torque derivative values.

[0017] According to a non-limiting aspect of the invention, the step of determining a distribution ratio of the driver's torque setpoint between a front wheel set and a rear wheel set is carried out according to energy criteria.

[0018] According to a non-limiting aspect of the invention, the steps of the method are repeated periodically according to a period of between 1 ms and 20 ms.

[0019] Another aspect of the invention relates to control means comprising a memory storing software instructions for implementing the method defined according to any one of the aforementioned aspects of the invention.

[0020] One aspect of the invention relates to a powertrain of a four-wheel drive motor vehicle comprising control means such as those mentioned above.

[0021] The powertrain can be electric, hybrid or thermal.

[0022] The invention and its various applications will be better understood by reading the following description and examining the accompanying figures.

[0023] [Fig-1] illustrates, in a schematic manner, a filtering of a couple applied to a train of front wheels and a torque applied to a set of rear wheels according to the state of the art.

[0024] [Fig.2] schematically illustrates curves making it possible to illustrate a torque dynamic resulting from the implementation of the filtering illustrated in [Fig.l].

[0025] [Fig.3] schematically illustrates a powertrain of a four-wheel drive motor vehicle according to an exemplary embodiment of the invention.

[0026] [Fig.4] illustrates an example of execution of the steps of a method according to the invention.

[0027] [Fig.5] illustrates a change in torque distribution between a set of front wheels and a rear wheel set of a powertrain of a vehicle made using the method according to the invention.

[0028] Unless otherwise specified, the same element appearing in different figures has a single reference.

[0029] Figures 1 and 2 have been described in the preamble to the description.

[0030] [Fig. 3] illustrates a powertrain 10 of a four-wheel drive motor vehicle comprising control means 11 arranged to execute the steps of the method for controlling a front wheel set and a rear wheel set of the powertrain according to the invention.

[0031] According to a non-limiting exemplary embodiment, the control means 11 are formed by a vehicle control unit, also called VCU (for Vehicle Control Unit in English).

[0032] The control means 11 comprise at least one processor and at least one memory storing software instructions for implementing the method according to the invention.

[0033] The powertrain 10 is of the hybrid type and comprises a front wheel set 12 comprising a heat engine 13 and a first electric traction motor 14. A coupling and decoupling device 15 makes it possible to selectively couple and decouple the heat engine 13 and / or the first electric traction motor 14 with the front wheel set 12. The coupling and decoupling device 15 takes the form of a gearbox. In order to be able to isolate the first electric traction motor 14 from the heat engine 13 during a pure electric driving mode, a clutch 16 is interposed between the heat engine 13 and the first electric traction motor 14.

[0034] Furthermore, the powertrain 10 also comprises a rear wheel set 17 provided with a second electric traction motor 18 associated with a speed reducer 19 and a device 20 for coupling and decoupling the second electric traction motor 18 with the rear wheels of the powertrain 10. The coupling and decoupling device 20 may consist of a dog clutch device, a clutch or a gearbox.

[0035] [Fig. 2] illustrates, schematically, the steps of an example of implementation of the method 100 according to the invention. The steps are executed by the control means 11 of the powertrain 10.

[0036] The method 100 comprises a step 101 of determining a driver torque setpoint. This driver torque setpoint is also called an IVC setpoint (for "Driver Will Interpretation"). This driver torque setpoint corresponds to the driver torque setpoint enabling a desired acceleration of the vehicle to be obtained and can be transmitted from a vehicle accelerator pedal position sensor to the control means 11.

[0037] The method 100 also comprises a step 102 of determining a distribution ratio of the driver's torque setpoint between the front wheel set 12 and the rear wheel set 17 of the powertrain 10.

[0038] The distribution ratio of the torque setpoint can be determined based on energy criteria, such as a state of charge of the vehicle's traction battery or a high temperature of the first or second electric traction motor 14, 18 limiting their performance. The distribution ratio can be transmitted to the control means 11 by a module (not shown) external to the control means 11.

[0039] The method 100 then comprises a step 103 of determining a derivative of the distribution ratio of the driver's torque setpoint between the front wheel set 12 and the rear wheel set 17 of the powertrain 10. This derivative can be calculated by the control means 11 or transmitted to the control means 11 by the module external to the control means 11.

[0040] Depending on the driver's torque setpoint, the distribution ratio and the derivative of the distribution ratio determined by the control means 11, the method 100 comprises a step 104 of determining a derivative of a torque gradient to be applied to the front wheel set 12 and a derivative of a torque gradient to be applied to the rear wheel set 17.

[0041] According to a non-limiting exemplary embodiment, the derivative of a torque gradient to be applied to the front wheel set 12 is defined by the following function: Ccons Trècms ^cons reduced ^cons Av = K xC +KXC • With : * C^yS = Derivative of a torque gradient to be applied to the front wheel set 12; • qcous _ driver COUpie instruction; . çcons _ Derived from a predetermined powertrain torque; • KL°'1S _ j^utio of distribution of the driver's torque instruction to apply to the front wheel set 12; • j^cons _ Derived from the distribution ratio of the driver's torque setpoint to be applied to the front wheel set 12.

[0042] According to a non-limiting exemplary embodiment, the derivative of a torque gradient to be applied to the rear wheel set 17 is defined by the following function: = - Kâonx x C™ + ( 1 - Kcm,x} x C*™ • With : icons AR = Derivative of a torque gradient to be applied to the train of rear wheels 17; • Qtons _ driver torque setting; . c«ms _ Derived from a predetermined powertrain torque; • Kcons _ Ratio of distribution of the driver's torque setpoint to apply to the front wheel set 12; . jçcchis _ Derived from the driver's torque setpoint distribution ratio to be applied to the front wheel set 12.

[0043] According to a non-limiting embodiment, the derivative of a torque gradient to be applied to the front wheel set 12 and the derivative of a torque gradient to be applied to the rear wheel set 17 determined are limited by predetermined drivetrain torque derivative values.

[0044] These predetermined powertrain torque derivative values ​​thus form a minimum torque limitation and a maximum torque limitation making it possible to control and obtain the same torque dynamics on the front wheel set 12 and on the rear wheel set 17. These predetermined powertrain torque derivative values ​​can for example be recorded in a map.

[0045] The method 100 then comprises a filtering step 105 of filtering the derivatives of a torque gradient to be applied to the front 12 and rear 17 wheel sets previously determined.

[0046] For this purpose, a first filtering function 21 is used to filter the determined derivative of a torque gradient to be applied to the front wheel set 12. This first filtering function 21 makes it possible to avoid oscillations on the front wheel set 12 when the mechanical clearances of the front wheel set 12 pass through the heat engine 13 and / or the first electric traction motor 14.

[0047] Furthermore, a second filtering function 22 is used to filter the determined derivative of a torque gradient to be applied to the rear wheel set 17. This second filtering function 22 makes it possible to avoid oscillations on the rear wheel set 17 when the mechanical clearances of the rear wheel set 17 pass through the second electric traction motor 18.

[0048] The method 100 then comprises a step 106 of controlling a torque applied to the front wheel set 12 as a function of the derivative of a torque gradient to be applied to the filtered front wheel set and a torque applied to the rear wheel set 17 as a function of the derivative of a torque gradient to be applied to the rear wheel train 17 filtered.

[0049] For this purpose, the control means 11 can transmit a first torque setpoint to a controller of the thermal engine 13 and / or of the first electric traction motor 14. The first torque setpoint corresponds to the filtered derivative of a torque gradient to be applied to the front wheel set 12. The control means 11 can also transmit a second torque setpoint to a controller of the second electric traction motor 18. The second torque setpoint corresponds to the filtered derivative of a torque gradient to be applied to the rear wheel set 17.

[0050] The steps of the method 100 according to the invention can be repeated periodically according to a period of between 1 ms and 20 ms, typically 10 ms.

[0051] [Fig. 5] illustrates a change in torque distribution between the front wheel set 12 and the rear wheel set 17 carried out using the method 100 according to the invention.

[0052] More particularly, • The CIO curve illustrates the driver's torque setpoint in Nm; • Curve Cil illustrates the torque applied to the front wheel set 12 in Nm • Curve C12 illustrates the torque applied to the rear wheel set 17 in Nm; • Curve C13 illustrates the derivative of a torque gradient to be applied to the front wheel set 12 in Nm / s; • Curve C14 illustrates the derivative of a torque gradient to be applied to the rear wheel set 17 in Nm / s; • Curve C15 illustrates a limitation of maximum torque in Nm / s; • Curve C16 illustrates a minimum torque limitation in Nm / s; • Curve C17 illustrates the vehicle speed in km / h.

[0053] More particularly, when changing the torque distribution 80Nm => 20Nm on the front wheel set 12 and 20Nm => 80Nm on the rear wheel set 17, it can be seen that the torque dynamics on the front wheel set 12 are identical to those of the rear wheel set 17. Thus, the speed of the vehicle remains constant while the torque distribution is modified.

[0054] In other words, the differences in torque dynamics of the front wheel set 12 and the rear wheel set 17 due to the mechanical dispersions and / or the differences of the electric traction motors 14, 18 are compensated by the step 104 of determining a derivative of a torque gradient to be applied to the front wheel set 12 and a derivative of a torque gradient to be applied to the rear wheel set 17.

Claims

Claims

1. Method (100) for controlling a front wheel set (12) and a rear wheel set (17) of a powertrain (10) of a four-wheel drive motor vehicle comprising the steps, executed by control means (11) of said powertrain (10), of: - Determine (101) a driver torque instruction; - Determine (102) a distribution ratio of said driver torque setpoint between said front wheel set (12) and said rear wheel set (17); - Said method (100) being characterized in that it comprises the steps of: - Determine (103) a derivative of said distribution ratio; - Determine (104) a derivative of a torque gradient at apply to said front wheel set (12) and a derivative of a torque gradient to be applied to said rear wheel set (17), said derivative of a torque gradient to be applied to said front wheel set (12) and said derivative of a torque gradient to be applied to said rear wheel set (17) being a function of said driver torque setpoint, said distribution ratio and said derivative of said distribution ratio determined; - Filtering (105) said derivative of a torque gradient to be applied to said front wheel set (12) and said derivative of a torque gradient to be applied to said rear wheel set (17) to avoid oscillations on said front and rear wheel sets (12, 17); - Control (106) a torque applied to said front wheel set (12) as a function of said filtered derivative of a torque gradient to be applied to said front wheel set (12) and a torque applied to said rear wheel set (17) as a function of said filtered derivative of a torque gradient to be applied to said rear wheel set (17).

2. Method (100) according to any one of the preceding claims, characterized in that the derivative of a torque gradient to be applied to the front wheel set (12) is defined by the following function: icons rrcons ., ^cons . r^rcons .„ ^cons Ay — A XL + A XL With: . çcons = Derivative of a torque gradient to be applied AV on the front wheel set (12); • çcons _ Driver COUpie instruction; . ^œns _ Derived from a predetermined powertrain torque; • j^cons _ Ratio I distribution of said driver torque instruction to be applied to the front wheel set (12); . j^-eons _ Derivative of said distribution ratio of said driver torque instruction to be applied to the front wheel set (12).

3. Method (100) according to any one of the preceding claims, characterized in that the derivative of a torque gradient to be applied to the rear wheel set (17) is defined by the following function: AR - -K xC +[1-A jxC - With: * Derivative of a torque gradient to be applied on the rear wheel set (17); • Qtons _ Driver torque setting; . ^cons = Derivative of a predetermined powertrain torque; • Kcons _ Ratio of the distribution of said driver torque instruction to be applied to the front wheel set (12); . j^cons _ Derivative of said distribution ratio of said driver torque instruction to be applied to the front wheel set (12);

4. Method (100) according to any one of the preceding claims, characterized in that the derivative of a torque gradient to be applied to the front wheel set (12) and the derivative of a torque gradient to be applied to the rear wheel set (17) determined are limited by predetermined powertrain torque derivative values.

5. Method (100) according to any one of the preceding claims, characterized in that the step of determining (102) a distribution ratio of the driver torque setpoint between a front wheel set (12) and a rear wheel set (17) is carried out as a function of energy criteria.

6. Method (100) according to any one of the preceding claims, characterized in that the steps of the method (100) are repeated periodically according to a period of between 1 ms and 20 ms.

7. Control means (11) comprising a memory storing software instructions for implementing the method (100) defined according to any one of the preceding claims.

8. Powertrain (10) of a four-wheel drive motor vehicle comprising control means (11) according to the preceding claim.

9. Automotive powertrain (10) according to the preceding claim, characterized in that it is electric or hybrid.

10. Automotive powertrain (10) according to claim 8, characterized in that it is thermal.

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