WO2017068386A1

WO2017068386A1 - Method of optimization of the dynamic functions of a vehicle

Info

Publication number: WO2017068386A1
Application number: PCT/IB2015/002133
Authority: WO
Inventors: Jean-Baptiste Doray; Frédéric BEHOUCHE
Original assignee: Volvo Truck Corporation
Priority date: 2015-10-20
Filing date: 2015-10-20
Publication date: 2017-04-27

Abstract

The present invention provides a method of implementing the safety dynamic functions of a vehicle with its actual height of gravity center. Said method comprises a step of assessing the height of the gravity center according to the weight of the vehicle, and a step of modifying the reference value of the height of the gravity center during the mission.

Description

Method of optimization of the dynamic functions of a vehicle

The present invention relates to a method of optimization of the dynamic control functions of a vehicle, and in particular the ESC functions. The vehicle is preferably an industrial vehicle. Background

Dynamic control of a vehicle is known to assist the driver in keeping the control of his vehicle. The dynamic control includes the ESC functions, which automatically detect an abnormal trajectory of a vehicle and correct its behavior. The ESC functions are usually calibrated according to the mass and/or the height of the center of gravity (H_cog) of the vehicle. However, the mass and/or H_cog is not necessary constant from one travel to the other. Thus, the ESC functions should be updated with the actual H_cog for each travel. Several methods are used to determine the H_cog of a vehicle. Some of those methods are based on the slippage rate of the wheels, such as described in WO2011036511. Other methods are based on the yaw rate of the vehicle like in EP 1749722. Each of these methods provides an estimation of Hcog. However, it is crucial that the value of H_cog updated within the dynamic control devices corresponds to the true and precise value of H_cog. Therefore, the present invention aims at providing a more reliable H_cog value.

Summary of the invention

It is the aim of the present invention to provide a method of optimizing the dynamic functions of a vehicle, and in particular an industrial vehicle, according to its actual driving status. In particular, the present method comprises steps aiming at providing an optimized calibration of the Hcog value according to the weight of the vehicle. The method further comprises steps aiming at determining the real H_cog value based on convergent iterations. The last step of this method is to implement into the dynamic control system, and in particular into the ESC functions, an updated value of the H_cog of the vehicle, in such a way to induce an adequate activation of the ESC functions, according to the real driving status of the vehicle.

To this extend, the present method comprises the steps of: a) Determining a first H_cog value, at start of a mission,

b) Comparing said H_cog value with one or more of an initial reference value and default reference value, c) Determining whether the conditions to modify one or more of the initial and default reference values are satisfied,

d) If said conditions are satisfied, then modifying the initial reference value and/or the default reference value to obtain an intermediate reference value,

d') Optionally storing the intermediate reference value determined during the mission e) Repeating the preceding steps a certain number of times,

f) Determining a real value of the H_cog of said vehicle,

g) Updating the dynamic control functions of said vehicle with an effective value H_eff of the Hcog.

h) Modifying the initial reference value to an updated reference value.

For the purpose of the present invention a mission should be understood as a travel from a starting point to a destination with a given payload. The start of a given mission is for example determined at key-on, and the end of said mission may be determined at key-off. However, other alternatives may be envisaged. For example, a new start of mission may be considered under variation of the weight of the vehicle, due to change of the payload, or at specific geographical positions.

The Hcog value is determined several times while the vehicle is running. The H_cog value may be determined by any known method, including the methods which analyze the behavior of the vehicle on road. It is preferably determined according to the method described in WO201 1036511 or a similar method, using the slippage rate of the wheels. This provides the advantage to not include sensors to the vehicle, in addition to the sensors already involved in existing functions. In particular, the wheel rotation sensors used in the determination of the slippage rate of the wheels are already used by the ESC functions. The H_cog values, are preferably determined during accelerations phases of the vehicle, which can be true accelerations of the vehicle, or on the contrary, braking phases of the vehicle.

The Hcog values, determined during the mission, are each compared to one or more reference values, which can be an initial reference value, a default reference value, or an intermediate reference value. An initial reference value denotes an H_cog value corresponding to the current weight of the vehicle, and already determined along a previous mission, or at the manufacturing of the vehicle. The aim of such an initial reference value is to easily determine an approximate value of H_cog, knowing the weight of the vehicle. It can be for instance an H_cog value of a calibration line wherein several H_cog values are already known with respect to given vehicle weights.

The intermediate reference value denotes an intermediate H_cog value, or a set of intermediate H_cog values, previously determined during the current mission. A default reference value denotes a H_cog value independent from the weight of the vehicle. A default reference value can be for instance the highest possible H_cog value.

While an initial reference value or an intermediate reference value can be modified during or at the end of a mission, a default reference value remains preferably unchanged during the life of the vehicle. When comparing an H_cog value to one or more reference values, either initial, or intermediate, it can be determined that said reference value is modified, that is to say that the reference value is either increased or decreased by a certain amount. The modification of the reference value may be subject to one or more conditions, including one or more of the difference between the H_cog value and said reference value, the standard deviation of the H_cog values determined during the mission, and the H_cog value itself. In particular each of the above parameters may determine a threshold value above which a reference value can be modified. The modification of a reference value may be subject to one or several other conditions.

The same process may be repeated at each H_cog determination, wherein each H_cog value is compared to one or more of the initial reference value, default reference value, and intermediate reference value, and wherein one or both of the initial and intermediate reference value is modified. Alternatively, the process may be stopped after a certain number of iterations.

Out of this process, a new initial reference value may be obtained, which can be used as a reference value for the following mission. In other word, the calibration line is updated with a new H_cog value for a given vehicle weight. This means that at least a part of the data is saved at the end of the mission and uploaded at starting of the following mission.

In addition, a converging H_cog value is obtained thanks to the successive modifications of intermediate reference values. Such an H_cog value, obtained by the converging method, is considered as the real H_C02 value. The present method further comprises the step of updating the dynamic control systems with an effective H_cog value, which is based on the real H_cog value, or a reference value, or a combination of both.

The present invention is further directed to an arrangement, within a vehicle equipped with dynamic control systems, allowing the application of the method described herein. In particular, said arrangement comprises sensors, computing systems, and memories, and is connected to the dynamic control systems in such a way that updated key reference values of the H_cog are considered by the dynamic control systems

The present invention also encompasses a vehicle equipped with such an arrangement, wherein the method herein described is processed.

Brief description of the drawings

Figure 1 : Calibration line, updated with a new reference value of H_cog for a given vehicle weight

Figure 2; flow chart showing the iterative process of determining a real value of H_cog and the update of the calibration line

Figure 3: schematic arrangement according to the present invention

Detailed description

At start of a given mission (100), the weight of the vehicle is determined (1 10) and the corresponding H_cog value is deduced (120) and considered as the initial reference value H_rero for the purpose of the dynamic control functions. In other word the H_refD is initially considered as the true H_cog value in the settings of the ESC.

The initial reference value H_rei_¾, corresponding to the weight of the vehicle, is for example determined according to a calibration line stored in a permanent memory (130). Said calibration line can comprise a certain number of vehicle weight values associated to the corresponding H_cog values, as shown in figure 1. In particular, a fixed value of H_cog may be defined, corresponding to the weight of the vehicle when it is empty. Additional values are provided, including one H_cog value corresponding to the maximum authorized weight of the vehicle, and intermediate H_cog values, each corresponding to intermediate vehicle weights. Preferably, the calibration line comprises 2 to 10 values in addition to the H_cog value corresponding to the weight of the empty vehicle, or between 4 and 8 values. The calibration line is preferably predetermined at the time the vehicle is manufactured.

From the beginning of the mission (100), and for at least a certain time during the mission, the H_COg value is regularly determined (220). Any method of determination may be used to determine the H_cog value. The H_cog value is preferably evaluated according to the slippage rate of the wheels of the vehicle during acceleration phases, as described in WO2011036511. For example, H_cog may be determined at each braking phase during the mission or for a predetermined number of braking operations

According to a first option, a first H_cog value Hi is compared to the initial reference value H_refo (240). It is checked whether the conditions to change the initial reference value are satisfied (340). In case these conditions are satisfied, the reference value H_refo is modifiedto an intermediate reference value H_ren (440). In particular, the initial reference value can be increased to an intermediate reference value H_refi, higher than H_rero, if the determined Hi is higher than H_rera. On the contrary, the reference value H_refo is decreased to an intermediate reference value H_ren, lower than H_rero, if the determined value Hi is lower than the initial reference value H_rero. The intermediate reference value H_refi is temporarily stored in a memory (540) and used as a new reference value in an iterative process. In addition, the determined H_cog value Hi may be stored in another memory (560). The process is iterated, with a second H_cog value H₂, determined during the same or a separate acceleration phase, wherein H₂ is compared with the intermediate reference value H_ren, generated after the previous H_cog determination.

In a general way, the process is iterated n times (500) wherein n corresponds to 3 to about 500 iterations, preferably 4 to 200, and more preferably 5 to 100 iterations. H_n values are thus sequentially determined (220), and compared to the H_re_f¾(_n-i), as shown in figure 2. According to a second option, the first H_cog value Hi, determined during the first braking phases of the mission (220), is compared to the default reference value H_refd (250). The default reference value H_refd is independent from any previous measurement or calibration. The default reference value H_refd is preferably the highest possible H_cog value corresponding to the vehicle, and therefore remains unchanged from one mission to the other. The default reference value H_refd is also independent from any vehicle weight measurement. It is checked whether the conditions to change the default reference value H_refd are satisfied (350). If these conditions are satisfied, the default reference value H_refd is then modified to an intermediate reference value H_refd(n-i₎ (450). The new intermediate reference value H_refd is temporarily stored in a memory, and involved in subsequent iterative operations. The iteration process (500) is performed as above.

Depending on the vehicle type and the expected degree of optimization, the first H_cog value H_\ can be compared to one or both of the initial reference value H_refl) (240) and the default reference value H_refd, (250) according to the first and the second options above-mentioned. . Preferably, the first H_cog value is simultaneously compared to both initial reference value H_refo and default reference value H_refd, and each of the initial reference value H_refo and default reference value H_refd may be modified to a corresponding intermediate reference value H_refo(n- l) and H_refd(n-i), wherein H_refO(n-i) and H_refd(n-i) can be equal or different. The conditions under which the initial reference values H_refo (340) and H_refd (350) are modified are not necessarily the same.

The standard deviation 6_C0g is also determined (230) after each H_cog evaluation, taking into consideration all the H_cog values determined since the start of the mission and stored in the memory (560). The standard deviation 6_C0g is determined before or simultaneously to the comparison of a H_cog value H_n with the corresponding reference value (240, 250), and may be included in the conditions under which one or more of the reference values H_refo, H_refd, H_refo(n- i)j Hrefd(n-i ) are modified (340, 350).

In general way, one or more of the reference values H_refo, H_refd, H_ref0(n-i)₅ H_refd(n-i) is modified if the difference between H_n and said reference value is higher than a threshold value.

Such a threshold value may be the standard deviation 6_c0g itself. In other words, a reference value may be modified if the difference between Hn and said reference value is higher or equal to the standard deviation 6_C0g .Alternatively, said threshold value can be a value higher than the standard deviation 6_C0g by a certain amount, such as about 10% or about 20% or about 50%. The conditions of modification (340, 350) are independently determined for each of the reference values H_refo, H_ref_d, H_refo(_n-i), H_refd(n-i).

Also, the range of modification of a reference value (440, 450) may be conditioned to certain parameters. It may be determined that reference value H_refo, H_refd, H_ref0(n-i), H_refd(n-i) is modified by a certain predetermined ratio, such as around 10% or around 20% or around 30% of the corresponding reference value. In a first alternative, one or more of the reference values Hrefl), Hrefd, H_refO(n-i), H_refd(n-i) can be modified by a predetermined metric value, such as about 0.10 meter, or about 0.20 meter, or about 0.50 meter. In a second alternative, the variation of one or more of the reference values H_refo, H_refd, H_refo(n-i), H_refd(_n-i) may depend on the difference between the determined H_cog value H_n and said reference values. More particularly a high difference between the H_cog value H_n and a given reference value initiates a large modification of said reference value, whereas a low difference between the H_cog value H_n and said reference value initiates a small modification of the reference value H_re¾_n-i)- The difference between the determined H_cog value H_n and a reference value may be considered high if it is higher than about 1 meter, or about 0.50 meter, and it can be considered low if it is for example below about 0.50 meter, or below about 0.30 meter. Also, the modification of a reference value can be considered large if it is larger than about 0.50 meter, and small if it is lower than 0.20 or 0.10 meter.

In a third alternative, a given reference value may be modified in such a way that it becomes equal to the H_n value just determined.

Above and below, a modification of a given reference value is meant for an increase or a decrease of said reference value, in the extend it is feasible. For example the specific default reference value H_{re d} may only decrease if it is chosen as the highest possible value.

The above described n iterations (500), starting either from an initial value H_refo or a default reference value H_refd, or both, allow to converge to the real H_cog value (600) with a good accuracy. In more details, a real value H_reai_d of the H_cog can be deduced only from the convergence starting from the default reference value H_ref_d (650). Alternatively, a real value H_reaio (640) of H_cog can be determined only by the mean of the convergent iterations starting from the initial reference value H_refo- For a better accuracy, the real value H_reai of the H_cog of the vehicle is the average of both values H_reaid and H_reaio, simultaneously obtained during the iterations (640, 650). The number n of iterations (500) may be predetermined to a certain amount, such as around 10, or 50, or 200 iterations. Alternatively, the convergent iterations, either based on the initial reference value H_refo or the default reference value H_refd,can stop as soon as the difference between a measured H_cog value H_n and one or more of its corresponding reference values H_refo, Hrefd, H_refo(_n-i), H_ref_d(n-i) is in the same range as the standard deviation 6_C0g. In a further alternative, the iterations may stop after the difference between the measured H_cog value H_n and one or more of the corresponding reference values H_refo, H_ref_d, H_refo(_n-i), H_ref_d(_n-i) remains in the order of the standard deviation <5_cog after 2 or 3 consecutive H_cog determinations. Under these conditions, it is reasonably considered that a real value of H_cog is determined.

Thus, a real value of H_cog is determined after a limited number of iterations. However, the process may start again at certain points of time during a given mission, to determine a new real value of the H_cog and compare it to the real value previously determined in the mission. Certain points of time include for example regular time periods at which the iterative process is launched during the mission, specific geographical positions, like for example before a portion of road comprising turns and slopes such as in mountains. The iterative process may thus be initiated a number p of times (900) during a given mission, wherein p is comprised between 1 and 100 or more. The newly determined real value H_reaip is compared to the previously determined real value H_reai(p-i) (910). In case the newly determined real value H_reai_p of H_cog differs from the previously determined real value H_reai(_{p- 1}) by a certain amount, such as about 10% or 20% or more than 50%, then a dysfunction in the dynamic control system may be detected (920). In this specific case, alert signals may be provided to the driver, either visual or audio or both. In addition, automatic settings may be adopted for the purpose of the dynamic functions. For example, in case divergent real values of H_cog are determined during a same mission, the dynamic control functions may automatically consider the initial reference value Hrero or the default reference value H_refd in such a way that best safety running conditions are adopted. Once the real value of H_cog is determined (600), according to the above-described iterative process, an efficient value H_eff of H_cog is computed and uploaded within the dynamic control systems (700). H_eff replaces any previous reference value considered by the dynamic control systems of the vehicle, and in particular the ESC functions. The threshold activation of the ESC functions will thus be determined according to this H_eff value. Depending on the selected parameters, H_eff may be one of the values previously determined like Hreaio, H_reaid, H_reai. Alternatively, any one of these previously determined values H_reaio, H_reaid, Hreai may be compared to the initial reference value H_rero, and an average value can be computed to provide H_eff. Otherwise, the highest of the previously determined values H_reai₀, H_reaid, Hreai, and Hrefo may be selected as H_eff in such a way that the best safety conditions are applied. During the iterative process above described, each H_cog value H_n is thus compared to one or more of the corresponding intermediate reference values H_refl)(n-i) and H_refd(n-i) to provide an efficient value H_eff that is uploaded into the ESC functions. One or more of the sets of intermediate reference values H_refo(n-i) stored in a memory (540), H_refd(n-i) stored in another memory (550) or determined H_cog values H_n, stored in a third memory (560), may simultaneously be used to update the calibration line with a new reference value H_reftr(800). The set of the H_cog values H_n, is preferably used to the update of the calibration line.

The update of the calibration line can occur for instance at the end of a mission, taking into account all the values of H_cog determined during the mission and stored in the temporary memory (560, 550), or only a certain number of these values. The initial reference value H_refo can be updated to in such a way that a certain amount of the considered H_cog values determined during the mission are below the updated reference value A certain amount of the H_cog values may be for example 100%, or 95% or 90% of the H_cog values.

Alternatively, the initial reference value H_refo can be updated during the mission. In that case, the initial reference value H_rero is updated to a new reference value H_reft)' at each H_cog determination under specific conditions. Said specific conditions include one or more of the followings:

- Hrefo is updated to H_refo' in such a way that a certain amount of the H_n values determined since the beginning of the mission is below Η_Γβω'· A certain amount can be about 100%, about 95% or about 90%.

- Hrefo is updated to H_reft)' at a given iteration n, only if the corresponding H_n value is higher than the standard deviation 6_C0g of all the H_cog values determined since the beginning of the mission.

Hrefo is updated to H_refD' at a given iteration n, only if the corresponding H_n value is higher than the standard deviation e_cog of all the H_cog values determined since the beginning of the mission by a certain amount. A certain amount can be about 10%, or 20% or 50%.

Hrefo is updated to H_ref0' at a given iteration n, only if the corresponding H_n value differs from the previous value H(_n-1) by a certain amount. A certain amount can be about 10%, or 20% or 50%. Hrefo is updated to H_refl)' at a given iteration n, only if the difference between the corresponding H_n value and the previous value H_(n-1) is higher than the standard deviation 6_C0g.

Alternatively, the calibration line can be updated during the mission, after a certain number m of H_cog values have been determined. The number m can be chosen to provide a statistically relevant set of values. For example, m can be comprised between 5 and 100 H_cog values, preferably between 10 and 50 H_eog values.

In all instances, the updated calibration line is stored in a memory (130) and used at the starting of the following mission. Thus, based on the updated calibration line, an initial reference value H_reflr can be determined according to the new weight of the vehicle.

The present invention also encompasses an arrangement allowing the update of the H_cog value and its implementation into the dynamic control systems. In particular such an arrangement comprises :

- an H_cog determination module M_cog,

- a first computation module C₂,

- a calibration module C_a,

- a second computation module C₃, and - a dynamic control module D_m.

The H_cog determination module M_cog allows to determine the height of the gravity center H_cog of the vehicle. To this extend it may comprise one or more sensors Si. Such sensors may be of various type, like wheel rotation sensors SI, used to determine the slippage rate of the wheels, pressure sensors S₂, used to determine the weight of the vehicle, or any other sensors Si, which can be used to determine the H_cog value. The H_cog computation module further comprises a calculator Ci, used to compute the data received from the sensors Si, S₂, S,, in such a way that a value H_n of the H_cog can be provided. The H_cog determination module M_cog may further be connected to external sensors like the vehicle speed sensors, in such a way that accelerations phases can be recognized. Thus, calculations of the H_cog value can be triggered upon variation of speed of the vehicle. The H_cog determination module M_cog can alternatively, or in addition, be activated upon other events, like the braking pedal activation, or the accelerator pedal activation. M_cog provides series of H_cog values, H_n, which are stored in a first memory mi. The memory mi is preferably a RAM, storing the data computed during a mission, and erased at the end of the mission.

The arrangement of the present invention further comprises a first computation module C₂, which computes the H_n data stored in the memory mi. In particular, the first computation module C₂ comprises at least a standard deviation calculation module M_Sd, and a convergence computation module C_m. The standard deviation calculation module M_sd allows to determine the standard deviation of the H_n values stored in mi during a mission. The convergence computation module C_m allows to determine the difference between each H_cog value determined in Ci and a reference value. The first computation module C₂ may further be provided with a memory m₂ to store intermediate values, like incremental H_ref values. The first computation module C₂ thus produces either a new reference value H_reflr or a real H_cog value H_reai, or both of them.

The calibration module C_a comprises a memory m₃ to store the reference value H_ref¾ of the H_cog corresponding to a given vehicle weight, and an update module U_ref to update the reference values H_rero to a new reference value The data stored in the memory m₃ remain after the vehicle is switched off, in such a way that they can be loaded at the following key-on.

The second computation module C₃ allows to determine an effective value H_eff to implement to the dynamic control module, based on the data received at least from C₂ and C_a. Said effective value H_eff is uploaded within the dynamic control systems D_m, and in particular within the ESP functions. The present invention further relates to a vehicle comprising such an arrangement, and able to implement in the dynamic control systems an optimized value of the height of the gravity center H_cog, according to the method described herein.

Claims

Claims :

1. A method for optimizing the dynamic control functions of a vehicle, said method comprising the steps of:

a) Determining a value Hi of the height of the gravity center H_cog of said vehicle, at start of a mission (220),

b) Comparing the H_cog value Hi determined in step a) with one or more of the initial reference value H_rero (240), and default reference value H_refd (250),

c) Determining whether the conditions to modify one or more of the initial reference value Hrefo (340) and default reference value H_refd (350) are satisfied,

d) If said conditions of step c) are satisfied, then modifying one or more of the initial reference value H_refo (440) and default reference value H_refd (450) to obtain the corresponding intermediate reference values H_reroi , and H_refdi ,

e) Repeating the steps a), b), c) and d) a number n of times (500) wherein a H_cog value H_n is determined in step a), wherein said H_n value is compared to one or more of the intermediate reference values H_ref0(n-i) and H_refd(_n-i) in steps b) and c), and wherein said intermediate reference value H_refD(n-i) and H_refd(_n-i) are modified to the corresponding new intermediate reference values HrefOn and H_refdn in step d). f) Determining a real value H_reai of the H_cog of said vehicle (600),

g) Updating the dynamic control functions of said vehicle with an effective value H_eff of the H_cog (700).

h) Modifying the original reference value H_rero with an updated reference value H_refD'(800).

2. A method according to claim 1 , wherein said H_cog value H_\ is step a) and H_n in step e) are determined by the computation of the slippage rate of the wheels of the vehicle.

3. A method according to claims 1 or 2, wherein said conditions in step c) include the fact that H_n is higher than the standard deviation <5_cog of the H_n values determined from the start of the mission.

4. A method according to any one of the preceding claims, wherein the modification of the reference value in step d) corresponds to an increase or a decrease of said reference value, and wherein said predetermined amount corresponds to about 10% of the reference value to be modified.

5. A method according to any one of the preceding claims, wherein said number n of iterations is determined to provide a statistically relevant number of measurements.

6. A method according to any one of the preceding claims, wherein the effective value H_eff of H_COg implemented to the dynamic control functions in step g) is the highest of the real value H_reai determined in step f) and the reference value H_refo.

7. A method according to any one of the preceding claims, wherein H_refo' in step h) is determined in such a way that about 95% of the values H_n of H_cog measured during the mission are under the new initial reference value H_refo'.

8. A method according to any one of the preceding claims, wherein the updated reference value Hreffl' is saved in a calibration line at the end of the mission (130), and uploaded at start of the following mission.

9. An arrangement comprising : an Hcog determination module M_cog.

a computation module C₂,

a calibration module C_a,

a computation module C₃, and

a dynamic control module D_m,

10. A vehicle comprising the arrangement of claim 9, wherein the dynamic control functions are optimized according to the method described in claims 1 to 8.