Method for estimating the load of a vehicle in a low-speed manoeuvring situation, and vehicle

Abstract

The invention relates to a method for estimating the load of a motor vehicle in a low-speed manoeuvring situation, the method comprising a repetition of the steps: a – acquiring a current mode relating to the transmission lever; b – acquiring information of a current direction of movement of the vehicle, which can adopt three values: forward, backward and undetermined; c - acquiring information on a current forward speed of the vehicle; d - calculating a load ratio as a function of a torque delivered by the power train to the wheels and an observed acceleration, this ratio being representative of the current load of the vehicle, the load being influenced in particular by the local gradient of the roadway, rising or falling, the step of calculating the load ratio being suspended in the case where the information on the direction of movement is undetermined or in the case where the information on the direction of movement is opposite to the current mode.

Description

[0001] DESCRIPTION TITLE OF THE INVENTION: METHOD FOR ESTIMATING THE LOAD OF A VEHICLE IN A LOW-SPEED MANEUVERING SITUATION

[0001] The present invention claims priority from French application No. 2402230 filed on 06.03.2024, the content of which (text, drawings and claims) is incorporated herein by reference.

[0002] The invention relates to a method for estimating the load of a vehicle, particularly in a low-speed maneuvering situation.

[0003] The intrinsic load of a vehicle is highly variable, particularly due to the presence of passengers or various loads in the luggage compartment. The load can also concern the coupling of a possible trailer or the presence of a roof box. The concept of half payload or full payload is often used to refer to a reference load, but in practice the actual load is always different.

[0004] In addition to the intrinsic load, the vehicle may face an apparent load linked to the gradient of the road traveled by the vehicle. Thus, there is a greater apparent load when the road is uphill and a lesser apparent load when the road is downhill.

[0005] It is known that knowledge of the vehicle load is useful for adapting the transmission gear shift laws accordingly in an automatic gearbox.

[0006] The present invention is particularly concerned with estimating the load of the vehicle during very low speed maneuvers, typically parking maneuvers.

[0007] We are also particularly interested in vehicles equipped with a controlled gearbox, that is to say where the driver has, among other things, a transmission mode called D ('Drive') to go forward and a transmission mode called R ('Reverse') to go backward.

[0008] The invention presented below is particularly relevant for the case of hybrid-powered vehicles, namely those equipped with an internal combustion engine and an electric powertrain. However, the present invention is also applicable to conventional vehicles with only a thermal engine, and the present invention is also applicable to 100% electric vehicles.

[0009] In known solutions, a load ratio calculation is carried out based on a torque delivered by the powertrain to the wheels and based on an acceleration observed by deriving the travel speed information. However, it turns out that the calculation carried out does not take into account the direction of travel of the vehicle; it is carried out indifferently and indistinctly in forward and reverse gear.

[0010] Parking maneuvers often involve a series of small movements, sequentially forward and then backward, or in other words, alternating small forward and backward movements, before arriving at the desired final position and stopping the vehicle cycle.

[0011] Furthermore, it turns out that when parking, some drivers switch the transmission mode a little prematurely, that is to say they select mode R while the vehicle is still moving forward a little, or conversely they select mode D while the vehicle is still moving backward a little.

[0012] The inventors therefore sought to improve the known method for estimating the vehicle load, by taking into account in an improved manner the gradient of the road traveled and on the other hand to manage in a more clever way the transient phases of switching between the R and D modes (and vice versa).

[0013] To this end, the present invention proposes a method for estimating the load of a motor vehicle in a low-speed maneuvering situation, the method comprising a repetition of the steps: a- a step of acquiring a current mode relating to the transmission lever, said current mode being able in particular to take the values ​​D and R, b- a step of acquiring information on the current direction of movement of the vehicle, said direction of movement information being ternary and being able to take three values: Forward, Backward, and Indeterminate, c- a step of acquiring information on the current forward speed of the vehicle, a time derivation of said forward speed information making it possible to obtain information on observed acceleration, d- a step of calculating a load ratio, obtained as a function of a torque delivered by the powertrain to the wheels and as a function of an observed acceleration, this ratio being representative of the current load of the vehicle,said load being influenced in particular on the one hand by the total rolling mass of the vehicle and on the other hand by the local gradient of the roadway, rising or falling, characterized in that the step of calculating the load ratio is suspended in the case where the current direction of travel information is undetermined or in the case where the current direction of travel information is opposite to the current mode.,

[0014] Expressed in another way, we suspend the conventional calculation leading to the estimation of the load ratio in the case of unavailability of the direction of movement information and also in the case of a divergence between the position of the lever and the direction of movement.

[0015] More precisely, the phrase "the case where the direction of travel information is opposite to the current mode" concerns a divergence (inconsistency) according to two distinct cases: - the transmission lever is on R and the direction of travel is forward - the transmission lever is on D and the direction of travel is backward.

[0016] Thanks to the provisions promoted above, the results of the load estimation calculation are only taken in conditions where it gives a relevant and reliable result, and for the other cases, we will see below that we operate with previous values ​​of load ratio, possibly reversed. We will thus see that there is a substantial benefit in the case where the vehicle moves on a track with a certain upward or downward gradient.

[0017] Detailed knowledge of the vehicle load during low-speed maneuvers allows for better management of the reduction of certain potential gear noises, particularly in hybrid mode.

[0018] It is generally noted that the transmission lever has at least four positions: P, R, N, D. There may also be auxiliary positions for manual control modes and regenerative braking proportion options.

[0019] In the presentation, the D and R positions are of particular interest. These two positions indicate the driver's desire to move forward or backward, respectively.

[0020] We note that the transmission lever can be a lever with mechanically stable and defined positions, or the transmission lever can be of the impulse type, namely with unstable positions and return to a rest position, the active or engaged mode then being managed by a computer to which the lever is connected.

[0021] It should be noted that the term "low speed" in this document means speeds between 0 and 10 km / h, and very often for small maneuvers speeds between 0 and 6 km / h.

[0022] According to one embodiment, it is provided that in the event of a change of mode in progress, e.g. D to R or R to D, the output of the load ratio calculation is reversed before the calculation is suspended.

[0023] It is noted that the behavior is different depending on whether the unavailability for the calculation is generated by information of undetermined direction of movement or whether the unavailability for the calculation is generated by an inconsistency between the direction of movement and the driver's intention to move.

[0024] In the second case, we use the knowledge of the driver's desire to reverse the direction of travel to reverse the estimated load ratio, which makes it possible to effectively take into account the case of maneuvering on a sloping track.

[0025] More precisely, if the track is rising when the vehicle is moving forward, the estimated charge is positive, whereas conversely the track will be falling when the vehicle is moving backward, and the inversion of charges will give a negative charge which is more faithful to reality than the calculations as they were done previously.

[0026] According to one embodiment, in the case where the direction of travel information becomes undetermined, the last value of the load ratio is used during the suspension of the load ratio calculation step.

[0027] Unlike the previous case, the vehicle speed information becomes so weak that the direction can no longer be determined, and therefore the process provides, in the event of the direction of travel becoming undetermined, to retain the load ratio last calculated for the rest of the regulation.

[0028] According to one embodiment, the load ratio calculation step is resumed as soon as the direction of travel information is Forward or Backward and the direction of travel information is consistent with the current mode.

[0029] The calculation of the load ratio estimate starts again as soon as the direction of travel is known and the current mode corresponds to the same direction. The calculation of the load ratio estimate starts again as soon as the two pieces of information are consistent, e.g. either both forward or both backward.

[0030] According to one embodiment, the load ratio is calculated by calculating an acceleration normally expected for a torque delivered by the powertrain (GMP) to the wheels and subtracting the observed acceleration.

[0031] This produces an acceleration difference which can be transformed into an estimated load by means of a reference to a calibration table or to analytical formulas.

[0032] According to one embodiment, the calculation of a load ratio uses a kinematic model.

[0033] The kinematic model was established during preliminary tests on multiple loading instances and vehicles corresponding to the technical platform of the vehicle of interest.

[0034] According to one embodiment, the steps of acquiring current mode information (a-) and direction of movement information (b-) are each carried out with a frequency at least equal to 20 Hz. The decision is thus taken in real time, at most every 50 ms there is no response time effect. According to a particular embodiment, the frequency can be of the order of 50 Hz with a recurrence task of 20 milliseconds.

[0035] The invention further relates to a motor vehicle comprising a powertrain (GMP) controlled at least in part by a control unit configured to implement the method as described above.

[0036] According to one embodiment, it is the vehicle's ABS / ESP computer which provides the direction of travel information and the forward speed information.

[0037] According to one embodiment, the powertrain (GMP) is hybrid. The powertrain comprises an internal combustion engine and an electric drive train equipped with an electric traction / propulsion motor.

[0038] According to one embodiment, the transmission is robotized and the transmission mode control is impulse. This configuration favors early control change, because the lever operation is very easy and light. The relevance of the present invention thus proves high for this type of configuration.

[0039] The invention will be further detailed by the description of non-limiting embodiments, and on the basis of the appended figures illustrating variants of the invention, in which: [Fig. 1] schematically illustrates a vehicle in a low-speed maneuvering situation on an inclined track having an upward slope; [Fig. 2] shows a functional block diagram of a control system according to an example of the present invention; [Fig. 3] illustrates a logic diagram illustrating an example of logic applied within the framework of the present invention; [Fig. 4] shows a logic diagram illustrating an example of a parking maneuver; [Fig. 5] is analogous to Figure 4 and illustrates another example of a parking maneuver.

[0040] In the various figures, the same references designate identical or similar elements. For reasons of clarity of the presentation, certain elements are not necessarily represented to scale.

[0041] Figure 1 represents a motor vehicle VH moving on an inclined track 7. In the example illustrated, track 7 is ascending when the vehicle moves forward, noted AV. The track is descending when the vehicle moves backward, noted ARR.

[0042] The inclination of the track has the value of the angle α. As known, the effect of gravity on the dynamics of the vehicle is expressed as gx sine(α) applied to the mass of the vehicle, g being the acceleration of Earth's gravity.

[0043] As already mentioned in the introductory part, the intrinsic load of a vehicle (its mass) is eminently variable, in particular due to the presence of passengers or various loads in the luggage compartment or roof box.

[0044] Loading can also involve the coupling of a possible trailer; this element has an influence on the total rolling mass of the vehicle and, of course, this increases the effect of gravity and inertial terms.

[0045] In addition, the effect of the inclination α of track 7 results in an apparent charge: mxgx sine(α). This apparent charge is positive when the vehicle is moving uphill and it is negative when the vehicle is moving downhill.

[0046] The vehicle is powered by a GMP powertrain, arranged on the front axle in the illustrated example. Note that it is not excluded that there is also an electric drivetrain on the rear axle.

[0047] In the illustrated example, the powertrain is a hybrid unit with an internal combustion engine 1 and an electric machine 2.

[0048] However, the invention is also applicable in the context of a conventional powertrain with a single thermal engine and, moreover, the invention is also applicable in the context of a 100% electric vehicle.

[0049] It is noted that the present invention covers all types of vehicle: private vehicle, utility vehicle, van, truck and so on.

[0050] In Figure 2, an example of a hybrid powertrain is illustrated in which an internal combustion engine 1 and an electric machine 2 each selectively deliver torque to a gearbox 3. The output shaft of the gearbox drives, via a differential, the wheels of the train in question. A single wheel 59 is illustrated in Figure 2.

[0051] In the illustrated configuration, the electrical machine ME, 2 is controlled, via an inverter, marked 22 by a control unit marked 12.

[0052] The thermal combustion engine ICE also called thermal engine is controlled by another control unit marked 11.

[0053] A supervisory calculator is also called a control unit and marked 10.

[0054] The vehicle is equipped with a control unit 4 for the transmission mode of the gearbox. This is a pulse control solution, for example, with a central neutral position and two positions on either side. It should be noted that there may also be two other overtravel positions on either side, i.e. a total of four unstable positions and one neutral position.

[0055] According to another configuration, the transmission mode control member is conventional with stable positions for each of the positions P, R, N, D as well known per se.

[0056] The invention is in reality not limited to a particular embodiment of the transmission mode control member.

[0057] However, in all cases, the desire to move expressed by the driver is materialized by the engagement of either a mode of movement called D as 'Drive' to go forward, or a mode of movement called R as Reverse to go backward.

[0058] Furthermore, the vehicle is equipped with a braking computer 5 performing at least the ABS function and often in practice also the dynamic stability function known by the acronym ESP.

[0059] The braking computer 5 periodically provides information on the vehicle's travel speed VV. This information is obtained from the speed measured on all four wheels and, in the event of braking or slipping, on the fastest wheels.

[0060] Here, the travel speed information is also called the current advance speed VV. This information is delivered in real time via a periodic frame of the spontaneous emission type on the CAN multiplexed network. Typically, the sending recurrence frequency is 100 Hz, i.e. one frame every 10 milliseconds.

[0061] Furthermore, the braking computer 5 periodically delivers the vehicle's direction of travel information. The direction of travel information is ternary. The direction of travel information can take three values: Forward, Backward, and Indeterminate. This information is obtained from the signals measured on the four wheels, which can advantageously be double signals in quadrature with each other, which makes it possible to instantly determine the direction of rotation of each wheel. When the wheel rotation speed is too low, it turns out that the direction of travel information can no longer be established with certainty and then the direction of travel information is delivered with the 'indeterminate' value IND.

[0062] When the travel speed is too low, for example less than 1.5 km / h or less than 1 km / h, it is no longer possible to determine the direction of travel and the information on the direction of travel then becomes indeterminate.

[0063] Furthermore, the vehicle is equipped with an accelerator pedal 8 with an electronic sensor which delivers a signal proportional to the depression of said accelerator pedal (^ pedal or ^ accel).

[0064] Furthermore, the vehicle is equipped with a brake pedal 9 with at least one switch.

[0065] Turning to Figure 3, the proposed method begins with the acquisition steps which are described below.

[0066] An acquisition step (denoted a-) of the current mode concerning the transmission lever is provided. As already indicated, the current mode can in particular take the values ​​D and R, without excluding other values. This step is represented on the flowchart of figure 3 by the box marked 61.

[0067] A step is planned for acquiring the vehicle's direction of travel information (marked b-). As a reminder, the direction of travel information can take three values: Forward, Backward, and Undetermined. This step is represented in Figure 3 by the box marked 62.

[0068] An acquisition step (noted c-) of information on the advance speed of the vehicle VV is planned.

[0069] If the direction of travel information is equal to “undetermined”, then the calculation of the load ratio is suspended, which is represented by box 65 in Figure 3.

[0070] As known per se, a time derivation of the forward speed information makes it possible to obtain information on the observed acceleration of the vehicle.

[0071] At step d- of the process represented essentially by boxes 63 and 64 in Figure 3, it is first verified that the direction of movement information is not "unavailable" and that the information is in R mode or in D mode.

[0072] In box 63, the method evaluates the consistency of the two pieces of information: direction of movement and transmission mode. There is consistency in the following two cases: - the transmission mode is on D and the direction of movement is forward - the transmission mode is on R and the direction of movement is backward.

[0073] Conversely, there is a divergence in the following two cases: - the transmission mode is on R and the direction of travel is forward - the transmission mode is on D and the direction of travel is backward.

[0074] When there is consistency, the output of box 63 is YES and box 64 representing the calculation of the load ratio is implemented.

[0075] The load ratio is estimated by first calculating an acceleration normally expected for a torque delivered by the powertrain (GMP) to the wheels.

[0076] Furthermore, by deriving the forward speed information, we obtain the observed acceleration of the vehicle.

[0077] Then, the observed acceleration is subtracted from the calculation of the normally expected acceleration, which gives an observed acceleration difference.

[0078] This acceleration difference is transformed into an estimated load by means of a reference to a calibration table 15 or to analytical formulas.

[0079] As a supplement or alternative, a kinematic model of the vehicle can be used to convert the observed acceleration difference to the estimated vehicle load.

[0080] Naturally, aerodynamic effects are neglected given the low speeds involved.

[0081] Returning to Figure 3, conversely, when there is a divergence in direction of travel, the output of box 63 is NO (arrow 68) and the calculation of the load ratio is suspended.

[0082] However, it is planned that prior to the suspension, an inversion of the load ratio is carried out, which is materialized by box 66.

[0083] The process is recurrent, it is executed frequently, for example at least every 50 ms. Note that it is not necessary for the acquisitions of incoming information to be made at the same sampling frequency.

[0084] In Figures 4 and 5, the top line indicates the transmission mode. The area below indicates the vehicle's travel speed in absolute value. The area below indicates the direction of travel as received by the control unit that implements the method. The line below indicates the binary suspension information of the load ratio calculation.

[0085] The area below shows the calculated load ratio values. The load ratio is shown as a solid line when it is the result of a real-time calculation, and as a thin dotted line when it is derived from previously calculated values ​​(calculation suspended).

[0086] The lowest line indicates both the acceleration on the gas pedal and the action on the brake pedal.

[0087] Figure 4 illustrates a case where the driver waits for the vehicle to actually stop before changing direction on the transmission control lever. For example, he uses the brake pedal for this, as illustrated on the bottom line of the timing diagram. Note that Figure 4 also illustrates maneuvers on flat ground without a slope.

[0088] The timing diagram begins with a forward arrival with slowing down to 0.

[0089] At time t1, the speed VV becomes very small and the direction of travel information becomes indeterminate. This is a reason for suspending the load ratio calculation as illustrated by arrow 69 in figure 3. The binary suspension information denoted SUSP changes to 1. At time t2, the speed VV is actually equal to 0. At time t3, the driver switches the transmission control lever from position D to position R. Just after the driver applies a little gas, which can be seen on the dotted curve representing the acceleration at the bottom of the graph. At time t4, the speed VV takes off from 0, but is still below the determination threshold; it is only at time t5 that the direction of travel information changes from the indeterminate value IND to the rear value ARR. At time t5, the binary suspension information SUSPre changes to 0. The load ratio calculation can be carried out again.

[0090] Reverse movement generally occurs between times t4 and t6.

[0091] At time t6, the speed falls below the indeterminacy threshold and the direction of travel information changes from the rear value ARR to the indeterminate value IND. The binary suspension information noted SUSP changes to 1.

[0092] After the speed is actually equal to 0, the driver switches the transmission control lever from position R to position D (time t7). Immediately after this, the driver applies a little more gas. The speed VV rises from 0, but is still below the determination threshold; it is only at time t8 that the direction of travel information changes from the undetermined value IND to the rear value AV. The load ratio calculation can be carried out again.

[0093] Forward movement generally occurs between times t8 and t9.

[0094] The speed falls below the indeterminacy threshold at time t9 and the direction of travel information changes from the forward value AV to the indeterminate value IND. The load ratio calculation is suspended again.

[0095] At time tv, the driver shifts the transmission control lever from position D to position R. Immediately afterward, the driver applies a little more gas. Reverse gear movement generally occurs between times tw and tx with the same logic as before.

[0096] The driver then shifts the transmission control lever from position R to position D (instant ty). A very slight forward movement may occur.

[0097] The driver then shifts the transmission control lever from position D to position P (instant tz). The parking maneuver is then completed.

[0098] The calculation of the load ratio is carried out from the beginning until t1 then from t5 until t6 then from t8 until t9 then from tw until tx. The rest of the time, the calculation of the load ratio is suspended.

[0099] In Figure 5, there are usually early transmission mode reversals. In addition, this is a case where the vehicle is performing parking maneuvers on an inclined lane, uphill in the illustrated case.

[0100] The timing diagram begins with an arrival in forward gear AV, with a slowdown to 0.

[0101] At time ta, the driver shifts the transmission control lever from position D to position R, before the speed reaches 0. There is a discrepancy between the current mode and the direction of travel observed; the load ratio calculation is reversed before being suspended. The binary suspension information SUSP changes to 1.

[0102] At time tb, the speed VV becomes very small and the direction of travel information becomes indeterminate IND. At time tc, the speed VV is actually equal to 0. At the same time, the driver applies the throttle, which can be seen on the dotted curve at the bottom of the graph. The speed starts from 0 and the backward movement begins at time td. At time te, the binary suspension information SUSP returns to 0. The calculation of the load ratio can start again.

[0103] At time tf, the driver shifts the transmission control lever from position R to position D, before the speed has reached 0. Here too there is an inconsistency between the actual direction of travel (reverse) and the driver's wish (mode D). The binary suspension information SUSP changes to 1

[0104] At time tg, the speed VV becomes very small and the direction of travel information becomes indeterminate IND. At time th, the speed VV is actually equal to 0. At the same time, the driver applies the throttle. The speed starts from 0 and forward movement begins at time ti. At time tj, the binary suspension information SUSP returns to 0. The calculation of the load ratio starts again. Forward movement generally occurs between times tj and tl with the same logic as before.

[0105] At time tk, the driver shifts the transmission control lever from position D to position R, before the speed reaches zero. Here too there is an inconsistency between the actual reverse direction of travel and the driver's desired mode D.

[0106] At time tl, the direction of movement information becomes undetermined IND.

[0107] The reverse movement generally occurs between times tm and tn with the same logic as before.

[0108] At time tp, the driver shifts the transmission control lever from position R to position D, before the speed reaches zero. The forward movement that follows is infinitesimal.

[0109] The driver then shifts the transmission control lever from position D to position P (instant tq). The parking maneuver is then completed.

[0110] According to a special provision, it should be noted that the calculation of the discharge ratio may be suspended for reasons other than those set out above, for example in the event of actuation of the brake pedal or the shifting of the transmission lever to position N in a non-transient manner.

[0111] It should be noted that the functional distribution between the control units marked 10, 11 and 12 in Figure 2 depends on the configuration of the technical platform.

[0112] In the example shown, the direction of travel information is provided by the brake computer. However, it should be noted that it is not excluded that the direction of travel information is obtained by another means, for example from a very precise GPS positioning system or from an external camera system.

[0113] According to an exemplary embodiment, the estimated load of the vehicle is broken down into a continuous component always present with the same positive sign and a component which reverses when the direction of travel is reversed.

[0114] It may be planned to acquire track inclination information, either by means of a specific inclinometer sensor or delivered by a precise mapping system. Knowledge of the local inclination makes it possible to calculate the inverting component and to deduce the continuous component.

Claims

CLAIMS1. Method for estimating the load of a motor vehicle in a low-speed maneuvering situation, the method comprising a repetition of the steps:a- a step of acquiring a current mode relating to the transmission lever, said current mode being able in particular to take the values ​​D and R,b- a step of acquiring information on the current direction of movement of the vehicle, said direction of movement information being ternary and being able to take three values: Forward, Backward, and Indeterminate,c- a step of acquiring information on the current forward speed of the vehicle, a time derivation of said forward speed information making it possible to obtain information on observed acceleration,d- a step of calculating a load ratio, obtained as a function of a torque delivered by the powertrain (GMP) to the wheels and as a function of an observed acceleration, this ratio being representative of the current load of the vehicle,said load being influenced in particular on the one hand by the total rolling mass of the vehicle and on the other hand by the local gradient of the roadway, rising or falling, characterized in that the load ratio calculation step is suspended in the case where the current direction of travel information is undetermined or in the case where the current direction of travel information is opposite to the current mode.

2. Method according to claim 1, characterized in that in the case of a change of mode in progress, eg D to R or R to D, the output of the load ratio calculation is inverted before the suspension of the calculation.

3. Method according to any one of claims 1 to 2, characterized in that in the case where the direction of travel information becomes undetermined, the last value of the load ratio is used during the suspension of the load ratio calculation step., 4. Method according to any one of claims 1 to 3, characterized in that the step of calculating the load ratio is resumed as soon as the direction of travel information is Forward or Reverse and the direction of travel information is consistent with the current mode.

5. Method according to any one of claims 1 to 4, characterized in that the load ratio is calculated by calculating an acceleration normally expected for a torque delivered by the powertrain (GMP) to the wheels and subtracting the observed acceleration.

6. Method according to claim 5, characterized in that the calculation of a load ratio uses a kinematic model.

7. Method according to any one of claims 1 to 6, characterized in that the steps of acquiring current mode information (a-) and direction of travel information (b-) are each carried out with a frequency at least equal to 20 Hz.8.Motor vehicle comprising a powertrain (GMP) controlled at least in part by a control unit configured to implement the method according to any one of claims 1 to 7.

9. Motor vehicle according to claim 8, characterized in that the powertrain (GMP) is hybrid.

10. Motor vehicle according to any one of claims 8 to 9, characterized in that the transmission is robotized and the transmission mode control is impulse.

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