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 _re ro for the purpose of the dynamic control functions. In other word the H _re fD is initially considered as the true H _cog value in the settings of the ESC.

The initial reference value H _re i _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 _ref o (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 _ref o is modifiedto an intermediate reference value H _re n (440). In particular, the initial reference value can be increased to an intermediate reference value H _ref i, higher than H _re ro, if the determined Hi is higher than H _re ra. On the contrary, the reference value H _ref o is decreased to an intermediate reference value H _re n, lower than H _re ro, if the determined value Hi is lower than the initial reference value H _re ro. The intermediate reference value H _ref i 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 H ₂ , determined during the same or a separate acceleration phase, wherein H ₂ is compared with the intermediate reference value H _re n, 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 _r e _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 _re fd(n-i ₎ (450). The new intermediate reference value H _re fd 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 _re fd, (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 _re fo and default reference value H _re fd, and each of the initial reference value H _re fo and default reference value H _re fd may be modified to a corresponding intermediate reference value H _ref o(n- l) and H _re fd(n-i), wherein H _re fO(n-i) and H _re fd(n-i) can be equal or different. The conditions under which the initial reference values H _re fo (340) and H _re fd (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 _re fo, H _re fd, H _re fo(n- i)j Hrefd(n-i ) are modified (340, 350).

In general way, one or more of the reference values H _re fo, H _re fd, H _re f0(n-i) ₅ H _re fd(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 _re fo, H _re f _d , H _re fo( _n -i), H _re fd(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 _re fo, H _re fd, H _re f0(n-i), H _re fd(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 _r efO(n-i), H _re fd(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 _re fo, H _re fd, H _re fo(n-i), H _re fd( _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 _re ¾ _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 _ref o or a default reference value H _re fd, or both, allow to converge to the real H _cog value (600) with a good accuracy. In more details, a real value H _rea i _d of the H _cog can be deduced only from the convergence starting from the default reference value H _re f _d (650). Alternatively, a real value H _rea io (640) of H _cog can be determined only by the mean of the convergent iterations starting from the initial reference value H _ref o- For a better accuracy, the real value H _rea i of the H _cog of the vehicle is the average of both values H _rea id and H _rea io, 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 _ref o or the default reference value H _re fd,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 _ref o, Hrefd, H _ref o( _n -i), H _re f _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 _ref o, H _re f _d , H _re fo( _n- i), H _re f _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 _rea ip is compared to the previously determined real value H _rea i(p-i) (910). In case the newly determined real value H _rea i _p of H _cog differs from the previously determined real value H _re ai( _{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 _re fd 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 _e ff of H _cog is computed and uploaded within the dynamic control systems (700). H _e ff 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 _rea id, H _rea i. Alternatively, any one of these previously determined values H _rea io, H _rea id, Hreai may be compared to the initial reference value H _re ro, and an average value can be computed to provide H _e ff. Otherwise, the highest of the previously determined values H _rea i ₀ , H _rea id, Hreai, and Hrefo may be selected as H _e ff 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 _re fd(n-i) to provide an efficient value H _e ff that is uploaded into the ESC functions. One or more of the sets of intermediate reference values H _re fo(n-i) stored in a memory (540), H _ref d(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 _re ftr(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 _ref o 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 _ref o can be updated during the mission. In that case, the initial reference value H _re ro is updated to a new reference value H _re ft)' at each H _cog determination under specific conditions. Said specific conditions include one or more of the followings:

- Hrefo is updated to H _re fo' in such a way that a certain amount of the H _n values determined since the beginning of the mission is below Η _Γβ ω'· A certain amount can be about 100%, about 95% or about 90%.

- Hrefo is updated to H _re ft)' 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 _re fD' 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 _re f0' 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 _refl r 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 C ₂ ,

- a calibration module C _a ,

- a second computation module C ₃ , 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 S ₂ , 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, S ₂ , 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 C ₂ , which computes the H _n data stored in the memory mi. In particular, the first computation module C ₂ 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 C ₂ may further be provided with a memory m ₂ to store intermediate values, like incremental H _ref values. The first computation module C ₂ thus produces either a new reference value H _refl r or a real H _cog value H _rea i, or both of them.

The calibration module C _a comprises a memory m ₃ 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 _re ro to a new reference value The data stored in the memory m ₃ 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 C ₃ allows to determine an effective value H _eff to implement to the dynamic control module, based on the data received at least from C ₂ 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.