METHOD FOR ESTIMATING THE LOAD OF A VEHICLE DURING LOW-SPEED MANEUVERING

Abstract

The invention relates to 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- acquisition of a current mode relating to the transmission lever, b- acquisition of information on the current direction of movement of the vehicle, which can take three values: Forward, Backward, and Indeterminate, c- acquisition of information on the current forward speed of the vehicle, d- calculation of a load ratio as a function of a torque delivered by the powertrain to the wheels and of an observed acceleration, this ratio being representative of the current load of the vehicle, said 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. Figure 3

Description

Title of the invention: METHOD FOR ESTIMATING THE LOAD OF A VEHICLE IN A LOW MANEUVERING SITUATION SPEED

[0001] The invention relates to a method for estimating the load of a vehicle, in particular in a low-speed maneuvering situation.

[0002] 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 may 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.

[0003] In addition to the intrinsic load, the vehicle may face an apparent load linked to the gradient of the road traveled by said vehicle. Thus there is a greater apparent load when the road is uphill and a lesser apparent load when the road is downhill.

[0004] It is known that knowledge of the vehicle load is useful for adapting the transmission gear change laws accordingly, in an automatically controlled gearbox.

[0005] The present invention is particularly concerned with estimating the load of the vehicle during very low speed maneuvers, typically parking maneuvers.

[0006] 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') for going forward and a transmission mode called R ('Reverse') for going backward.

[0007] The invention presented below is particularly relevant for the case of vehicles with hybrid engines, 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.

[0008] In known solutions, a load ratio calculation is carried out as a function of a torque delivered by the powertrain to the wheels and as a function of an acceleration observed by deriving the travel speed information. It turns out, however, 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.

[0009] Parking maneuvers often involve a series of small movements, sequentially forward and then backward, or in other words an alternation of small movements forward and backward, before arriving at the desired final position and stopping the vehicle cycle.

[0010] Furthermore, it appears that during parking maneuvers, 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.

[0011] 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 manner the transient phases of switching between the R and D modes (and vice versa).

[0012] 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 concerning 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 able to take three values: Forward, Backward, and Undetermined, c- a step of acquiring information on the current advance speed of the vehicle, a time derivation of said advance 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 load ratio calculation step is suspended in the case where the current direction of movement information is undetermined or in the case where the current direction of movement information is opposite to the current mode.

[0013] Expressed in another way, the conventional calculation leading to the estimation of the load ratio is suspended 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.

[0014] More precisely, the expression "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 in R and the direction of travel is forward - the transmission lever is in D and the direction of travel is backward.

[0015] 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 is moving on a track with a certain upward or downward gradient.

[0016] 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.

[0017] 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.

[0018] In the presentation, it is the D and R positions which are of particular interest. These two positions show the driver's desire to go forward or backward respectively.

[0019] It is noted 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.

[0020] It should be noted that the expression "low speed" means in this document speeds between 0 and 10 km / h, and very often for small maneuvers speeds between 0 and 6 km / h.

[0021] According to one embodiment, it is provided that in the event of a mode change in progress, eg D to R or R to D, the output of the load ratio calculation is inverted before the calculation is suspended.

[0022] 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 depending on whether the unavailability for the calculation is generated by an inconsistency between the direction of movement and the driver's desire to move.

[0023] 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.

[0024] More precisely, if the track is rising when the vehicle is moving forward, the estimated load is positive, whereas conversely the track will be falling when the vehicle is moving backward, and the inversion of loads will give a negative load which is more faithful to reality than the calculations as they were done previously.

[0025] According to one embodiment, in the case where the direction of movement information becomes undetermined, the last value of the load ratio is used during the suspension of the load ratio calculation step.

[0026] Unlike the previous case, the vehicle speed information becomes so low that the direction can no longer be determined, and therefore the method provides, in the event of the direction of travel becoming undetermined, to retain the load ratio last calculated for the rest of the regulation.

[0027] According to one embodiment, the load ratio calculation step is resumed as soon as the direction of movement information is Forward or Backward and the direction of movement information is consistent with the current mode.

[0028] The calculation of the load ratio estimate starts again as soon as the direction of movement 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.

[0029] 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.

[0030] This results in an acceleration difference which can be transformed into an estimated load by means of a reference to a calibration table or to analytical formulas.

[0031] According to one embodiment, the calculation of a load ratio uses a kinematic model.

[0032] The kinematic model was established during preliminary tests on multiple loading and vehicle instances corresponding to the technical platform of the vehicle of interest.

[0033] 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.

[0034] 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 previously.

[0035] According to one embodiment, it is the vehicle's ABS / ESP computer which delivers the direction of travel information and the forward speed information.

[0036] 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.

[0037] According to one embodiment, the transmission is robotized and the mode control The transmission is impulse. This configuration favors early control changes, because the lever operation is very easy and light. The relevance of the present invention is thus high for this type of configuration.

[0038] 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.l] schematically illustrates a vehicle in a low-speed maneuvering situation on an inclined track with an upward gradient; [Fig.2] shows a functional block diagram of a control system according to an example of the present invention; [Fig.3] illustrates a flowchart illustrating an example of logic applied within the framework of this; [Fig.4] shows a flowchart illustrating an example of a parking maneuver; [Fig.5] is analogous to [Fig.4] and illustrates another example of a parking maneuver.

[0039] In the various figures, the same references designate identical or similar elements. For reasons of clarity of the description, certain elements are not necessarily represented to scale.

[0040] [Fig.l] represents a motor vehicle VH moving on an inclined track 7. In the example illustrated, track 7 is rising when the vehicle moves forward, noted AV. The track is descending when the vehicle moves backward, noted ARR.

[0041] The inclination of the track has the value of the angle a. As known, the effect of gravity on the dynamics of the vehicle is expressed according to gx sine(a) applied to the mass of the vehicle, g being the acceleration of Earth's gravity.

[0042] 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.

[0043] The loading can also concern 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 the inertial terms.

[0044] In addition, the effect of the inclination a of track 7 results in an apparent charge: mxgx sine(a). This apparent charge is positive when the vehicle is moving uphill and it is negative when the vehicle is moving downhill.

[0045] The vehicle is powered by a GMP powertrain, arranged on the front axle in the illustrated example. It is noted that it is not excluded that there is also an electric powertrain on the rear axle.

[0046] In the illustrated example, the powertrain is a hybrid unit with an internal combustion engine 1 and an electric machine 2.

[0047] 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.

[0048] It is noted that the present invention covers any type of vehicle: private vehicle, utility vehicle, van, truck and so on.

[0049] In [Fig. 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 [Fig. 2].

[0050] In the illustrated configuration, the electrical machine ME, 2 is controlled, via an inverter, marked 22 by a control unit marked 12.

[0051] The thermal combustion engine ICE also called thermal engine is controlled by another control unit marked 11.

[0052] A supervisory computer is provided, also called a control unit and marked 10.

[0053] The vehicle is equipped with a control member 4 for the transmission mode of the gearbox. This is a solution with impulse control, for example, with a neutral central 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.

[0054] 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.

[0055] The invention is in reality not limited to a particular embodiment of the transmission mode control member.

[0056] 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.

[0057] 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.

[0058] The braking computer 5 periodically delivers the information on the vehicle's travel speed VV. This information is obtained from the speed measured on the four wheels and, in the event of braking or slipping, on the fastest wheels.

[0059] The movement speed information is also called current advance speed VV. This information is delivered in real time via a periodic frame of the type spontaneous transmission on the CAN multiplexed network. Typically the sending recurrence frequency is 100 Hz, or one frame every 10 milliseconds.

[0060] 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 of 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.

[0061] When the speed of movement 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 movement and the information on the direction of movement then becomes indeterminate.

[0062] 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 (0 pedal or 0 accel).

[0063] Furthermore, the vehicle is equipped with a brake pedal 9 with at least one switch.

[0064] Turning to [Fig.3], the proposed method begins with the acquisition steps which are described below.

[0065] A step is provided for acquiring (denoted a-) the current mode concerning the transmission lever. 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 [Fig.3] by the box marked 61.

[0066] A step is provided for acquiring (denoted b-) the vehicle's direction of travel information. As a reminder, the direction of travel information can take three values: Forward, Backward, and Undetermined. This step is represented in [Fig.3] by the box marked 62.

[0067] A step of acquisition (denoted c-) of information on the forward speed of the vehicle VV is provided.

[0068] 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 [Fig.3].

[0069] 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.

[0070] At the step noted d- of the process represented essentially by boxes 63 and 64 in [Fig.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.

[0071] In box 63, the method evaluates the consistency of the two pieces of information, on the one hand direction of movement and on the other hand mode of transmission. There is consistency in the following two cases: - the transmission mode is on D and the direction of travel is forward - the transmission mode is in R and the direction of travel is backward.

[0072] Conversely, there is divergence in the following two cases: - the transmission mode is in R and the direction of travel is forward - the transmission mode is on D and the direction of travel is backward.

[0073] When there is consistency, the output of box 63 is YES and box 64 representing the calculation of the load ratio is implemented.

[0074] The load ratio is estimated by first calculating an acceleration normally expected for a torque delivered by the powertrain (GMP) to the wheels.

[0075] Furthermore, by deriving the forward speed information, the observed acceleration of the vehicle is obtained.

[0076] Then, the observed acceleration is subtracted from the calculation of the normally expected acceleration, which gives an observed acceleration difference.

[0077] This acceleration difference is transformed into an estimated load by means of a reference to a calibration table 15 or to analytical formulas.

[0078] In addition or as an alternative, a kinematic model of the vehicle can be used to move from the observed acceleration difference to the estimated load of the vehicle.

[0079] Naturally, aerodynamic effects are neglected given the low speeds involved.

[0080] Returning to [Fig.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.

[0081] However, it is provided that prior to the suspension, an inversion of the load ratio is carried out, which is materialized by the box 66.

[0082] The method is recurrent, it is executed frequently, for example at least every 50 ms. It is noted that it is not necessary for the acquisitions of the incoming information to be made at the same sampling frequency.

[0083] 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 still 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.

[0084] The area below illustrates the calculated load ratio values. The load ratio is represented by a solid line when it results from a real-time calculation, and it is represented by a thin dotted line when it comes from previously calculated values ​​(calculation suspended).

[0085] The lowest line indicates both acceleration on the accelerator pedal and action on the brake pedal.

[0086] [Fig.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 [Fig.4] also illustrates maneuvers on flat ground without a slope.

[0087] The timing diagram begins with an arrival in forward gear with slowing down to 0.

[0088] At time t1, the speed VV becomes very small and the direction of travel information becomes indeterminate. This is a reason for suspending the calculation of the load ratio as illustrated by arrow 69 in [Fig.3]. The binary suspension information noted 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 SUSP changes back to 0. The calculation of the load ratio can be carried out again.

[0089] The reverse movement generally occurs between times t4 and t6.

[0090] 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.

[0091] 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, the driver applies the throttle a little more. The speed VV takes off 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 calculation of the load ratio can be carried out again.

[0092] Forward movement generally occurs between times t8 and t9.

[0093] The speed falls below the uncertainty threshold at time t9 and the information direction of travel changes from the forward value AV to the undetermined value IND. The load ratio calculation is suspended again.

[0094] At time tv, the driver shifts the transmission control lever from position D to position R. Immediately after, the driver applies a little more gas. Reverse gear movement generally occurs between times tw and tx with the same logic as before.

[0095] The driver then switches the transmission control lever from the position R to position D (instant ty). A very slight forward movement may occur.

[0096] The driver then shifts the transmission control lever from position D to position P (instant tz). The parking maneuver is then completed.

[0097] The calculation of the load ratio is carried out from the beginning until tl 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.

[0098] In [Fig.5], there are generally anticipated reversals of transmission mode. Furthermore, this is a case where the vehicle is performing parking maneuvers on an inclined track, rising in the illustrated case.

[0099] The timing diagram begins with an arrival in forward gear AV, with a slowdown to 0.

[0100] At time ta, the driver switches the transmission control lever from position D to position R, before the speed has reached 0. There is a discrepancy between the current mode and the direction of travel observed; the calculation of the load ratio is reversed before being suspended. The binary suspension information SUSP changes to 1.

[0101] At time tb, the speed VV becomes very small and the direction of movement information becomes indeterminate IND. At time te, the speed VV is actually equal to 0. At the same time, the driver applies the throttle again, 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.

[0102] At time tf, the driver switches 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 movement (rear) and the driver's wish (mode D). The binary suspension information SUSP changes to 1

[0103] At time tg, the speed VV becomes very small and the direction of movement information becomes indeterminate IND. At time th, the speed VV is actually equal to 0. In parallel, the driver applies the throttle. The speed starts from 0 and the 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. The forward movement generally occurs between times tj and tl with the same logic as before.

[0104] At time tk, the driver switches the transmission control lever from position D to position R, before the speed is zero. Here too there is an inconsistency between the actual reverse direction of travel and the driver's desire in mode D.

[0105] At time tl, the direction of movement information becomes undetermined IND.

[0106] The reverse movement generally occurs between times tm and tn with the same logic as before.

[0107] At time tp, the driver switches the transmission control lever from position R to position D, before the speed reaches zero. The forward movement that follows is infinitesimal.

[0108] The driver then switches the transmission control lever from position D to position P (time tq). The parking maneuver is then completed.

[0109] According to a particular provision, it should be noted that the calculation of the load ratio can be suspended for a reason 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.

[0110] It should be noted that the functional distribution between the control units marked 10, 11 and 12 in [Fig.2] depends on the configuration of the technical platform.

[0111] In the example illustrated, the direction of travel information is delivered by the braking 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 even from an external camera system.

[0112] 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.

[0113] It may be provided to acquire the 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 component which is reversed and to deduce the continuous component.

Claims

Claims

1. 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 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.,

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

3. Method according to any one of claims 1 to 2, characterized in that in the case where the direction of movement information becomes undetermined, the last value of the load ratio is used during the suspension of the step of calculating the load ratio.

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 Backward 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 a normal acceleration- badly 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 movement 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. d / . 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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