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

Abstract

The invention relates to a method for estimating the load of a motor vehicle during low-speed maneuvering. The method comprises repeating the following steps: a- acquiring a current mode for the transmission lever; b- acquiring information on the vehicle's current direction of travel, which can take three values: Forward, Reverse, and Indeterminate; c- acquiring information on the vehicle's current forward speed; d- calculating a load ratio based on the torque delivered by the powertrain to the wheels and the observed acceleration. This ratio is representative of the vehicle's current load. The load is influenced, in particular, by the local road gradient, whether uphill or downhill. The load ratio calculation step is suspended if the direction of travel information is indeterminate or if the direction of travel information 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, particularly in low-speed maneuvering situations.

[0002] The intrinsic load of a vehicle is highly variable, particularly due to the presence of passengers or various loads in the luggage compartment. Loading may also include the hitch of a trailer or the presence of a roof box. The concepts of half payload or full payload are 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 encounter an apparent load related 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 accordingly the shift laws of the transmission ratios in an automatic gearbox.

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

[0006] We are also particularly interested in vehicles equipped with a pilot-operated 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.

[0007] The invention presented below is particularly relevant to hybrid vehicles, namely those equipped with an internal combustion engine and an electric drivetrain. However, the present invention is also applicable to conventional vehicles with only internal combustion engines, and the present invention is also applicable to 100% electric vehicles.

[0008] In known solutions, a load ratio calculation is performed based on the torque delivered by the powertrain to the wheels and on an acceleration observed by deriving the speed information. However, it turns out that the calculation performed does not take into account the direction of travel of the vehicle; it is performed indiscriminately and indiscriminately in forward and reverse.

[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 too early, that is to say they select the R mode while the vehicle is still moving forward a little, or conversely they select the D mode while the vehicle is still moving backward a little.

[0011] The inventors therefore sought to improve the known method for estimating vehicle load, taking into account in an improved way the slope of the road traveled and on the other hand to manage in a more clever way the transient phases of switching between 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 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, Reverse, and Indeterminate, c- a step of acquiring information on the current forward speed of the vehicle, a time derivative of said forward speed information allowing obtaining information on the 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 slope of the road, uphill or downhill, characterized in that the load ratio calculation step is suspended in the case where the current direction of travel information is indeterminate or in the case where the current direction of travel 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 specifically, the phrase "the case where the direction of travel information is opposed to the current mode" concerns a divergence (inconsistency) according to two distinct cases: - the transmission lever is in R and the direction of movement is forward - the transmission lever is in D and the direction of movement is backward.

[0015] Thanks to the provisions described above, the results of the load estimation calculation are only used under conditions where it provides a relevant and reliable result. For other scenarios, we will see below that we work with previous load ratio values, possibly reversed. We will thus see that there is a substantial benefit when the vehicle is traveling on a road with a certain uphill or downhill gradient.

[0016] Detailed knowledge of 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, positions D and R are of particular interest. These two positions indicate the driver's intention to move 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 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.

[0021] According to one embodiment, it is provided that in the event of a mode change 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.

[0022] It is noted that the behavior is different depending on whether the unavailability for calculation is generated by information of indeterminate direction of movement or whether the unavailability for calculation is generated by an inconsistency between the direction of movement and the driver's intention to move.

[0023] In the second case, we take advantage of the knowledge of the driver's intention 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 track on a slope.

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

[0025] According to one embodiment, in the case where the direction of travel information becomes indeterminate, 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 weak that the direction can no longer be determined, and therefore the process provides, in the event of the direction of travel becoming indeterminate, for the retention of the load ratio last calculated for the continuation of the regulation.

[0027] 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.

[0028] The load ratio estimation calculation restarts as soon as the direction of travel is known and the current mode corresponds to the same direction. The load ratio estimation calculation restarts 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 a normally expected acceleration for a torque delivered by the powertrain (PW) 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 instances of loading and vehicles corresponding to the technical platform of the vehicle of interest.

[0033] According to one embodiment, the acquisition steps for current mode information (a-) and direction of movement information (b-) are each performed at a frequency of at least 20 Hz. The decision is thus made in real time; at most every 50 ms, there is no response time effect. According to a particular embodiment, the frequency can be on the order of 50 Hz with a recurrence interval of 20 milliseconds.

[0034] The invention further relates to a motor vehicle comprising a powertrain (PW) controlled at least in part by a control unit configured to implement the method as described above.

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

[0036] According to one embodiment, the powertrain is hybrid. The powertrain comprises an internal combustion engine and an electric drivetrain equipped with an electric traction / propulsion motor.

[0037] According to one embodiment, the transmission is robotized and the mode control of The transmission is impulse-driven. This configuration facilitates early control changes, as lever operation is very easy and light. The present invention is therefore highly relevant to this type of configuration.

[0038] The invention will be further detailed by describing non-limiting embodiments, and based on the accompanying 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 slope; [Fig.2] shows a functional principle diagram of a control system according to an example of the present invention; [Fig.3] illustrates a logic diagram showing an example of logic applied in the context 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 reference numerals designate identical or similar elements. For the sake of clarity, some elements are not necessarily shown to scale.

[0040] Fig. 1 represents a motor vehicle VH moving on an inclined track 7. In the illustrated example, track 7 is ascending when the vehicle is moving forwards, denoted AV. The track is descending when the vehicle is moving backwards, denoted 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 sin(a) applied to the mass of the vehicle, g being the acceleration due to 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 load may also relate to 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.

[0044] Furthermore, the effect of the inclination a of track 7 results in an apparent load: mxgx sin(a). This apparent load is positive when the vehicle is moving uphill and negative when the vehicle is moving downhill.

[0045] The vehicle is powered by a powertrain, arranged on the front axle in the illustrated example. It should be noted that it is possible that there may also be an electric drivetrain on the rear axle.

[0046] In the illustrated example, the powertrain is a hybrid group 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 internal combustion engine and furthermore the invention is also applicable in the context of a 100% electric vehicle.

[0048] It is noted that the present invention covers all types of vehicles: private vehicles, utility vehicles, vans, trucks and so on.

[0049] Figure 2 illustrates an example of a hybrid powertrain in which an internal combustion engine 1 and an electric machine 2 each selectively deliver torque to a gearbox 3. The gearbox output shaft drives, via a differential, the wheels of the axle in question. Only one wheel 59 is shown in Figure 2.

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

[0051] The internal combustion engine (ICE), also called the internal combustion engine, is controlled by another control unit identified as 11.

[0052] A supervisory computer, also called a control unit and identified as 10, is planned.

[0053] The vehicle is equipped with a control element 4 for the transmission mode of the gearbox. This is a pulse-controlled solution, for example, with a neutral center position and two positions on either side. It should be noted that there can 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 element is conventional with stable positions for each of the positions P,R,N,D as well known in itself.

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

[0056] However, in all cases, the driver's intention to move is materialized by engaging either a mode of movement called D for 'Drive' to go forward, or a mode of movement called R for 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 control unit 5 periodically outputs the vehicle's travel speed information VV. This information is obtained from the speed measured on all four wheels and, in the event of braking or skidding, on the fastest wheels.

[0059] Here too, the information regarding travel speed is referred to as the current feed speed VV. This information is delivered in real time via a periodic frame of the type at Spontaneous transmission on the CAN multiplexed network. Typically the transmission frequency is 100 Hz, i.e., one frame every 10 milliseconds.

[0060] Furthermore, the braking control unit 5 periodically provides information on the direction of travel of the vehicle. The direction of travel information is ternary. The direction of travel information can take three values: Forward, Reverse, and Undetermined. This information is obtained from signals measured on the four wheels, which can advantageously be dual signals in quadrature with each other, allowing the direction of rotation of each wheel to be determined instantly. When the wheel rotation speed is too low, the direction of travel information can no longer be established with certainty, and the direction of travel information is then delivered with the value 'undetermined' (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 of 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 depressment 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] An acquisition step (denoted a-) of the current mode for the transmission lever is planned. As already indicated, the current mode can take the values ​​D and R, among others. This step is represented on the logic diagram in [Fig. 3] by the box labeled 61.

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

[0067] A step is planned for acquiring (denoted c-) information on the vehicle's forward speed VV.

[0068] If the direction of travel information is equal to "indeterminate", 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 advance speed information makes it possible to obtain an observed acceleration information 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. Consistency exists in the following two cases: - The transmission mode is in D and the direction of travel is forward. - the transmission mode is in R and the direction of travel is towards the rear.

[0072] Conversely, there is divergence in the following two cases: - The transmission mode is in reverse (R) and the direction of travel is forward. - the transmission mode is in D and the direction of travel is backwards.

[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 (PW) to the wheels.

[0075] Furthermore, by deriving the advance speed information, we obtain the observed acceleration of the vehicle.

[0076] Next, 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 go 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 the 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 planned that prior to the suspension, the load ratio will be reversed, which is materialized by the box 66.

[0082] 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 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 it indicates the vehicle's speed in absolute value. The area below that indicates the direction of travel as received by the control unit implementing the process. The line below that indicates the binary information for suspending the load ratio calculation.

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

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

[0086] Figure 4 illustrates a case where the driver waits for the vehicle to come to a complete stop before changing direction using the transmission control lever. For example, the driver uses the brake pedal, as shown on the bottom line of the timing diagram. Figure 4 also illustrates maneuvers on a flat, level surface.

[0087] The timing diagram begins with an arrival in forward motion with deceleration to 0.

[0088] At time t1, the speed VV becomes very low and the direction of travel information becomes indeterminate. This is a reason for suspending the load ratio calculation, as illustrated by arrow 69 in [Fig. 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 moves the transmission control lever from position D to position R. Immediately afterward, the driver slightly increases the throttle, which is visible on the dotted curve representing acceleration at the bottom of the graph. At time t4, the speed VV rises 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 reverse value ARR. At time t5, the binary suspension information SUSP returns to 0. The load ratio calculation can then be performed again.

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

[0090] At time t6, the speed falls below the indeterminate threshold and the direction of travel information changes from the value rear ARR to the indeterminate value IND. The binary suspension information denoted SUSP changes to 1.

[0091] After the speed reaches 0, the driver moves the transmission control lever from position R to position D (time t7). Immediately afterward, the driver applies a little throttle. The speed VV starts to rise from 0, but is still below the determination threshold; it is only at time t8 that the direction of travel information changes from the indeterminate value IND to the reverse value AV. The load ratio calculation can then be performed again.

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

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

[0094] At time tv, the driver moves the transmission control lever from position D to position R. Immediately afterward, the driver applies a little throttle. The reverse movement generally occurs between times tw and tx, following the same logic as before.

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

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

[0097] The load ratio calculation is performed from the beginning up to tl, then from t5 to t6, then from t8 to t9, and then from tw to tx. The load ratio calculation is suspended for the remainder of the time.

[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, uphill in the illustrated case.

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

[0100] At time ta, the driver moves 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 observed direction of travel; the load ratio calculation is reversed before suspension. The SUSP binary information changes to 1.

[0101] At time tb, the speed VV becomes very small and the direction of travel information becomes indeterminate IND. At time te, the speed VV is actually equal to 0. Simultaneously, the driver applies more throttle, which is shown on the dotted line at the bottom of the graph. The speed starts from 0 and the rearward movement begins at time td. At time te, the binary suspension information SUSP returns to 0. The load ratio calculation can then begin again.

[0102] At time tf, the driver moves the transmission control lever from position R to position D, before the speed reaches 0. Here again, there is an inconsistency between the actual direction of travel (reverse) and the driver's intention (D mode). The binary information from the SUSP suspension changes to 1.

[0103] 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. Simultaneously, 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 load ratio calculation restarts. Forward movement generally occurs between times tj and tl with the same logic as before.

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

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

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

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

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

[0109] According to a particular provision, it should be noted that the calculation of the load ratio can be suspended for reasons other than those set out above, for example in the event of actuation of the brake pedal or the non-fugitive movement of the transmission lever to the N position.

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

[0111] In the illustrated example, the direction of travel information is provided by the braking control unit. However, it should be noted that it is possible that the direction of travel information could be obtained by another means, for example from a highly accurate GPS positioning system or even from an external camera system.

[0112] According to an example embodiment, the estimated load of the vehicle is decomposed 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 possible to acquire the track inclination information, either by means of a specific inclinometer sensor or provided by a precise mapping system. Knowledge of the local inclination makes it possible to calculate the inverting component and deduce the DC component.

Claims

Demands

1. 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 to take the values ​​D and R, b- a step of acquiring information on the current direction of travel of the vehicle, said direction of travel information being ternary and being able to take three values: Forward, Reverse, and Indeterminate, c- a step of acquiring information on the current forward speed of the vehicle, a time derivative of said forward speed information allowing to obtain information on the 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 slope of the road, uphill or downhill, characterized in that the load ratio calculation step is suspended in the case where the information on the current direction of travel is undetermined or in the case where the information on the current direction of travel is opposite to the current mode.

2. Method according to claim 1, characterized in that in case of mode change 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.

3. A method according to any one of claims 1 to 2, characterized in that in the case where the direction of travel information becomes indeterminate, the last value of the load ratio is used during the suspension of the load ratio calculation step.

4. A method according to any one of claims 1 to 3, characterized in that 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.

5. A method according to any one of claims 1 to 4, characterized in that the load ratio is calculated by calculating a normal acceleration. poorly expected for a torque delivered by the powertrain (PW) 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. A 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 of at least 20 Hz.

8. Motor vehicle comprising a powertrain (PW) 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 (PW) 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-driven.

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