Handling machine comprising a processing unit configured to output an indication of longitudinal stability, and corresponding method

Abstract

The invention relates to a material handling machine (1) comprising a chassis (2), a material handling system (300) carried by the chassis (2), a front axle (5) and a rear axle (6) supporting the chassis (2) on the ground, and a sensor system (100). The front axle (5) is a non-oscillating axle and the rear axle (6) is an oscillating axle. The sensor system (100) comprises a strain gauge (16) disposed on the rear axle (6), and two force sensors (15G, 15D) each fixed on the front axle (5) spaced along a transverse direction (Y) of the material handling machine (1). The force sensors (15G, 15D) are used together with the strain gauge (16) to provide an indication of the longitudinal stability of the material handling machine (1), and optionally an indication of its lateral stability. Also described are corresponding methods (1000, 2000, 3000, 4000) for indicating the stability of a handling machine.

Description

DOMAINE DE L'INVENTION

[0001] The present invention relates generally to handling machines and the indication of the longitudinal stability of the machine.

[0002] Such a machine can notably be made in the form of a telescopic handler, mechanical excavator, bucket loader or other. ART ANTERIEUR

[0003] Material handling machines are commonly equipped with a strain gauge at the rear axle to assess the longitudinal stability of the material handling machine.

[0004] There figure 1A Figure 101 schematically represents, in a top view, such a handling machine. The handling machine 101 comprises a chassis 102, a front axle 105, and a rear axle 106. The front axle 105 carries two front wheels 105A, and the rear axle 106 carries two rear wheels 106A. The front wheels 105A can be steered, although not shown; the rear wheels 106A can also be steered, as shown in the figure. figure 1B and the figure 1C The F1 arrow on the figure 1A indicates the forward direction of travel of the handling machine 101. A strain gauge 116 is located on the rear axle 106. If the signal from the strain gauge 116 decreases, the force applied to the ground via the rear axle 106 decreases, potentially indicating that the handling machine 101 is tipping forward around the front axle 105, as indicated by the dashed arrow TR on the figure 1A . Thus, the signal from the strain gauge 116 allows, among other things, the evaluation of the longitudinal stability of the handling machine 101.

[0005] However, such a handling machine 101 is not entirely satisfactory due to the following problem. When the rear wheels 106A are turned as indicated by the dashed arrows RWT on the figure 1B and the figure 1C The rear wheels 106A exert a force on the rear axle 106. This force increases with the steering angle of the rear wheels 106A, and becomes very significant when the rear wheels 106A reach their limit (RWB markings on the figure 1C ) at their maximum steering angle. This force disrupts the signal from strain gauge 116 and therefore the evaluation of the stability of the handling machine 101 using strain gauge 116.

[0006] The present invention aims to provide a new handling machine and a corresponding stability indication method to overcome all or part of the problems described above. RESUME DE L'INVENTION

[0007] To this end, the invention relates to a handling machine comprising a chassis, a handling system carried by the chassis, a front axle and a rear axle supporting the chassis on the ground, and a sensor system, in which the front axle is a non-oscillating axle and the rear axle is an oscillating axle, in which the sensor system comprises a strain gauge disposed on the rear axle, and two force sensors each fixed on the front axle spaced along a transverse direction of the handling machine, each force sensor being further fixed to or in contact with the chassis so as to measure a vertical support force of the chassis on said force sensor, the handling machine further comprising a processing unit connected to the sensor system, the processing unit being configured to: calculate a first average and a second average, the first average being an average of the vertical support forces measured by the two force sensors at a first instant, and the second average being an average of the vertical support forces measured by the two force sensors at a second instant subsequent to the first instant;determine whether an absolute difference between the second mean and the first mean is greater than a first threshold, the first threshold being non-zero; and if not (in other words, if it is determined that said absolute difference is not greater than the first threshold), provide an indication of the longitudinal stability of the handling machine as a function of the stress measured by the strain gauge at the first instant; if so (in other words, if it is determined that said absolute difference is greater than the first threshold), provide said indication of longitudinal stability as a function of at least the stress measured by the strain gauge at the second instant or as a function of the stress measured by the strain gauge at the first instant corrected as a function of an arithmetic difference between the second mean and the first mean.

[0008] The above-described configuration of the processing unit is based on the observation that strain gauge measurement alone is not always sufficient to accurately determine the longitudinal stability of the handling machine. Indeed, as mentioned above in relation to the prior art, this measurement can be affected by the steering of the rear wheels. Therefore, the invention takes into account the absolute difference between the second and first averages. If this absolute difference exceeds the first threshold, then the vertical load on the chassis at the front axle has changed significantly between the first and second times, indicating that the longitudinal stability of the handling machine has been significantly affected.It is therefore necessary to determine the longitudinal stability indication based on the most recent stress measurement—that is, the stress measured by the strain gauge at the second instant—or by correcting the stress measured by the strain gauge at the first instant. Conversely, if the absolute difference does not exceed the first threshold, then the vertical load of the chassis on the front axle has not changed significantly between the first and second instants, indicating that the longitudinal stability of the handling machine has not been significantly affected. A variation in the stress measured by the strain gauge between the first and second instants is therefore not indicative of the longitudinal stability of the handling machine, particularly because it could be due to the steering of the rear wheels.This is why the longitudinal stability indication is determined based on the stress measured by the strain gauge at the first instant, and not based on the stress measured by the strain gauge at the second instant.

[0009] In summary, the invention aims to improve the reliability of the longitudinal stability indication provided by the processing unit. As will be described later, this longitudinal stability indication can be displayed to a handling machine operator and / or used to stop one or more movements that could cause the handling machine to tip forward around the front axle.

[0010] The handling machine may also include one or more of the following features taken in any technically permissible combination.

[0011] According to one embodiment of the invention, the two force sensors are fixed on the front axle on either side of a longitudinal axis of the handling machine, the longitudinal axis being orthogonal to the transverse direction of the handling machine.

[0012] According to one embodiment of the invention, the processing unit is configured to: if it is determined that said difference in absolute value is greater than the first threshold, deliver said longitudinal stability indication as a function of the stress measured by the strain gauge at the second instant to the exclusion of other quantities measured by the sensor system.

[0013] According to one embodiment of the invention, the processing unit is configured to: if it is determined that said difference in absolute value is not greater than the first threshold, calculate a strain gauge drift, the drift being an arithmetic difference between the strain measured by the strain gauge at the second instant and the strain measured by the strain gauge at the first instant, and deliver said longitudinal stability indication as a function of the strain measured by the strain gauge at the first instant uncorrected as a function of said drift; if it is determined that said difference in absolute value is greater than the first threshold, deliver said longitudinal stability indication as a function of the strain measured by the strain gauge at the second instant corrected as a function of said drift, in particular reduced by said drift.

[0014] According to one embodiment of the invention, the processing unit is configured to: if it is determined that said difference in absolute value is greater than the first threshold, deliver said indication of longitudinal stability as a function of the stress measured by the strain gauge at the first instant corrected as a function of an arithmetic difference between the second mean and the first mean, in particular reduced by said arithmetic difference multiplied by a conversion coefficient.

[0015] According to one embodiment of the invention, the handling machine further comprises a display unit connected to the processing unit, and the processing unit is further configured to control the display of the longitudinal stability indication on the display unit.

[0016] According to one embodiment of the invention, the handling machine further comprises a cabin. In one embodiment, the display unit is located in the cabin.

[0017] According to one embodiment of the invention, the processing unit is further configured to: calculate a first deviation and a second deviation, the first deviation being a difference between the vertical support force measured by one of the two force sensors at the first instant and the first average, and the second deviation being a difference between the vertical support force measured by said force sensor at the second instant and the second average; determine if a difference in absolute value between the second deviation and the first deviation is greater than a second threshold, the second threshold being non-zero in the negative (in other words, if it is determined that the difference in absolute value between the second deviation and the first deviation is not greater than the second threshold), deliver an indication of lateral stability of the handling machine as a function of the first deviation;If so (in other words, if it is determined that the absolute difference between the second deviation and the first deviation is greater than the second threshold), issue said lateral stability indication based on the second deviation.

[0018] According to one embodiment of the invention, the processing unit is further configured to control the display of the lateral stability indication on the display unit.

[0019] According to one embodiment of the invention, the first instant and the second instant are separated by at most 10 milliseconds, more preferably by at most 5 milliseconds, more preferably still by at most 1 millisecond.

[0020] The invention also relates to a method for indicating the stability of a handling machine comprising a chassis, a handling system carried by the chassis, a front axle and a rear axle supporting the chassis on the ground, and a sensor system. wherein the front axle is a non-oscillating axle and the rear axle is an oscillating axle, wherein the sensor system comprises a strain gauge disposed on the rear axle, and two force sensors each fixed on the front axle spaced along a transverse direction of the handling machine, each force sensor further being fixed to or in contact with the chassis so as to measure a vertical support force of the chassis on said force sensor, the method comprising: calculating a first average and a second average, the first average being an average of the vertical support forces measured by the two force sensors at a first instant, and the second average being an average of the vertical support forces measured by the two force sensors at a second instant subsequent to the first instant;determine if the absolute difference between the second mean and the first mean is greater than a first threshold, the first threshold being non-zero; and if not, provide an indication of the longitudinal stability of the handling machine as a function of the stress measured by the strain gauge at the first instant; if so, provide said indication of longitudinal stability as a function of at least the stress measured by the strain gauge at the second instant or as a function of the stress measured by the strain gauge at the first instant corrected as a function of an arithmetic difference between the second mean and the first mean.

[0021] Such a process offers the same advantages as those described above in relation to the handling machine. These are therefore not repeated for the sake of brevity. The process may also include one or more of the following features in any technically feasible combination.

[0022] According to one embodiment of the invention, the method comprises: if it is determined that said difference in absolute value is greater than the first threshold, deliver said longitudinal stability indication as a function of the stress measured by the strain gauge at the second instant to the exclusion of other quantities measured by the sensor system.

[0023] According to one embodiment of the invention, the method comprises: if it is determined that said difference in absolute value is not greater than the first threshold, calculate a strain gauge drift, the drift being an arithmetic difference between the strain measured by the strain gauge at the second instant and the strain measured by the strain gauge at the first instant, and deliver said longitudinal stability indication as a function of the strain measured by the strain gauge at the first instant uncorrected as a function of said drift; if it is determined that said difference in absolute value is greater than the first threshold, deliver said longitudinal stability indication as a function of the strain measured by the strain gauge at the second instant corrected as a function of said drift.

[0024] According to one embodiment of the invention, the method comprises: if it is determined that said difference in absolute value is greater than the first threshold, deliver said indication of longitudinal stability as a function of the stress measured by the strain gauge at the first instant corrected as a function of an arithmetic difference between the second mean and the first mean.

[0025] According to one embodiment of the invention, the method further comprises: calculate a first deviation and a second deviation, the first deviation being a difference between the vertical support force measured by a force sensor among the two force sensors at the first instant and the first average, and the second deviation being a difference between the vertical support force measured by said force sensor at the second instant and the second average; determine if a difference in absolute value between the second deviation and the first deviation is greater than a second threshold, the second threshold being non-zero; if negative, provide an indication of lateral stability of the handling machine as a function of the first deviation; if positive, provide said indication of lateral stability as a function of the second deviation.

[0026] It is specified that all the characteristics presented in relation to the handling machine are applicable to the process and vice versa. BREVE DESCRIPTION DES DESSINS

[0027] Other features and advantages of the invention will become apparent from the following description, which is purely illustrative and not limiting and should be read in conjunction with the accompanying drawings, on which: [ Fig. 1A ] there Figure 1A is a schematic top view of the chassis of a material handling machine according to the prior art; [ Fig. 1B ] there Figure 1B is a view analogous to the Figure 1A , explaining the effect of rear wheel steering in prior art; Fig. 1C ] there Figure 1C is another view analogous to the Figure 1A , explaining the effect of rear wheel steering in prior art; Fig. 2 ] there Figure 2 is a schematic side view of a lifting arm material handling machine, according to one embodiment of the invention; [ Fig. 3 ] there Figure 3 is a schematic top view of the chassis of the material handling machine Figure 2 ; Fig. 4A ] there Figure 4A is a schematic view, from the rear, of the material handling machine Figure 2 ; Fig. 4B ] there Figure 4B is a partial schematic view, from the front, of the material handling machine Figure 2 ; Fig. 4C ] there Figure 4C is a schematic perspective view of one of the sensors shown on the Figure 4B ; Fig. 5 ] there Figure 5 is a schematic view of a processing unit of the material handling machine Figure 2 , according to one embodiment, to which sensors and control equipment are connected; [ Fig. 6 ] there Figure 6 is a flowchart comprising steps of a process for indicating the stability of the handling machine of the Figure 2 , according to one embodiment; [ Fig. 7 ] there Figure 7 is a flowchart comprising steps of a process for indicating the stability of the handling machine of the Figure 2 , according to another embodiment; [ Fig. 8 ] there Figure 8 is a flowchart comprising steps of a process for indicating the stability of the handling machine of the Figure 2 , according to yet another embodiment; [ Fig. 9 ] there Figure 9 is a flowchart comprising steps of a process for indicating the stability of the handling machine of the Figure 2 , according to yet another embodiment. DESCRIPTION DETAILLEE

[0028] The concept of the invention is described more fully below with reference to the accompanying drawings, in which embodiments of the concept of the invention are shown. In the drawings, the size and relative sizes of the elements may be exaggerated for clarity. Similar numbers refer to similar elements in all the drawings. However, this concept of the invention can be implemented in many different forms and should not be construed as being limited to the embodiments set forth herein. Rather, these embodiments are offered so as to make this description complete and to communicate the scope of the concept of the invention to those skilled in the art.

[0029] A reference throughout the specification to "an embodiment" means that a particular feature, structure, or characteristic described in relation to an embodiment is included in at least one embodiment of the present invention. Thus, the appearance of the phrase "in an embodiment" in various places throughout the specification does not necessarily refer to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.

[0030] With reference to the figures, a handling machine is proposed equipped with a processing unit configured to deliver an indication of the machine's longitudinal stability.

[0031] On the figure 2 An example of a handling machine 1 with a lifting arm has been shown. The handling machine 1 comprises a chassis 2 supported on the ground by means of a front axle 5 and a rear axle 6.

[0032] With reference to the figure 2 and to the figure 3 The front axle 5 carries two front wheels 5A and the rear axle 6 carries two rear wheels 6A. Not shown, the front wheels 5A and the rear wheels 6A can be steered.

[0033] The handling machine 1 includes a motorized system for moving the machine on the ground. The motorized system for moving the machine includes, for example, an electric motor and / or an internal combustion engine, and a transmission system to the wheels 5A, 6A and a steering control system enabling, on the one hand, the driving of the wheels 5A, 6A, and on the other hand, the steering of the wheels 5A, 6A and thereby directing the movement of the machine. The arrow F on the figure 3 indicates the forward direction of movement of handling machine 1.

[0034] Chassis 2 carries a handling system 300 and an actuation system allowing the handling system 300 to be moved relative to chassis 2.

[0035] The handling system 300 includes a lifting arm 3. The lifting arm 3 is articulated to the chassis 2 so that it can be moved around a pivot axis P between a lowered position and a raised position. In the example shown, the pivot axis P is closer to the rear axle 6 than to the front axle 5, and specifically behind the rear axle 6.

[0036] The handling system 300 also includes a handling device 3A located at the end of the lifting arm 3. In one embodiment, the handling device 3A comprises a tool holder and a tool that is detachably attached to this tool holder. Alternatively, the tool can be detachably integrated into the tool holder, or the tool can be directly attached to the end of the lifting arm 3.

[0037] The actuation system includes a lifting actuator, such as a hydraulic or electric cylinder, for moving the lifting arm 3 around the pivot axis P between its lowered and raised positions. The actuation system may further include a handling actuator, such as a hydraulic or electric cylinder, for moving the handling device 3A relative to the end of the lifting arm 3.

[0038] The lifting arm 3 can be telescopic, in which case the actuation system includes an actuator for extending the lifting arm 3, such as a hydraulic cylinder or a hydraulic jack. Alternatively, the lifting arm 3 can be non-telescopic.

[0039] The handling machine 1 further comprises a cab 4 supported by the chassis 2. The cab 4 is configured so that an operator of the handling machine 1 can sit in the cab 4 and operate the handling machine 1 from the cab 4. For this purpose, the cab 4 includes a human-machine interface, which may include a joystick, and the handling machine 1 includes a processing unit 8, comprising, for example, a computer. The processing unit 8 is connected to the human-machine interface and allows the operator to control the handling machine 1 via the human-machine interface. More specifically, the processing unit 8 allows the operator to control all or some of the following functions: the movement of the handling machine 1 relative to the ground, the position of the lifting arm 3, the extension of the lifting arm 3 if the lifting arm 3 is telescopic, the position of the handling device 3A, etc.For this purpose, the processing unit 8 can be configured to control the motorized system for moving the machine, the lifting actuator, the lifting arm extension actuator 3, the handling actuator, etc.

[0040] In addition, a display device 9 is arranged in the cab 4 in a position where the display device 9 is visible to the operator who has taken a seat in the cab 4.

[0041] Now, referring to figures 3 à 5 , the handling machine 1 further includes a sensor system 100. This sensor system 100 includes a strain gauge 16 and two force sensors 15G, 15D.

[0042] There figure 4A is a view of the handling machine 1 according to arrow A on the figure 3 and thus shows the handling machine 1 in view from the rear. As shown, the strain gauge 16 is arranged on the rear axle 6, and the rear axle 6 is oscillating, that is to say that the rear axle 6 is pivotally mounted on the chassis 2 so as to be able to pivot around a pivot axis Q (cf. figure 4A ) which is parallel to a longitudinal axis X (cf. figure 3 ) of the handling machine 1.

[0043] There figure 4B is a view of the handling machine 1 according to arrow B on the figure 3 and thus shows the handling machine 1 as viewed from the front. On the figure 4B The cab 4 and the handling system 300 are not shown to avoid cluttering the drawing. As shown, the force sensors 15G and 15D are each fixed to the front axle 5, and the front axle 5 is non-oscillating, meaning that the front axle 5 is mounted non-pivoting to the chassis 2. Furthermore, the force sensors 15G and 15D are fixed to the chassis 2 in such a way as to measure a vertical support force from the chassis 2 on the force sensors 15G and 15D.

[0044] In one example, as shown on the figures 4B And 4C , the 15G, 15D force sensors are annular load cells (“pancake load cells” in English) which have a plurality of through holes 155 (cf. figure 4C ) to receive fixing elements 255 (cf. figure 4B ), such as nuts or screws, to fix the force sensors 15G, 15D to both the front axle 5 and the chassis 2. Reference 159 on the figure 4C refers to a connection cable for connecting force sensors 15G, 15D, for example to the processing unit 8.

[0045] Alternatively, the 15G, 15D force sensors can be in contact with chassis 2 but not fixed to chassis 2.

[0046] As depicted on the figure 3 and the figure 4B The force sensors 15G and 15D are fixed to the front axle of the handling machine 1, spaced along a transverse Y direction, where the transverse Y direction and the longitudinal X axis are orthogonal. In other words, the force sensors 15G and 15D are spaced apart along the transverse Y direction. Preferably, as shown in the figure 3 , the force sensors 15G, 15D are fixed on the front axle 5 on either side of the longitudinal axis X, in which case the force sensor 15G is a left-side force sensor and the force sensor 15D is a right-side force sensor.

[0047] Now referring to the figure 5 , the processing unit 8 is connected to the sensor system 100, so that the processing unit 8 can acquire the quantities measured by the sensor system 100, namely the vertical support force FG measured by the force sensor 15G, the vertical support force FD measured by the force sensor 15D, and the stress CG measured by the strain gauge 16.

[0048] In addition, the processing unit 8 is connected to the display unit 9, so that the processing unit 8 can control the display unit 9. The processing unit 8 can also be connected to a speaker 9A, which can for example be placed in cabin 4.

[0049] With reference to the figure 6 , we now describe a stability indication method 1000 to indicate at least a longitudinal stability of the handling machine 1. The steps described below of method 1000 can be implemented by the processing unit 8. For this purpose, in one example, the processing unit 8 includes a computer which executes a suitable computer program.

[0050] In step 1010 of process 1000, the vertical support force FG, the vertical support force FD, and the stress CG at time T2 are acquired and stored in memory. Prior to step 1010, the vertical support force FG, the vertical support force FD, and the stress CG at time T1 were stored in memory. Time T2 is later than time T1, typically by a fixed time step ΔT = T2 - T1, and corresponding to an acquisition frequency of the processing unit 8. Preferably, the time step ΔT should be small, for example, at most 10 milliseconds, more preferably at most 5 milliseconds, and even more preferably at most 1 millisecond.

[0051] In step 1020, a first average M(T1) and a second average M(T2) are calculated, where: M(T1) is an arithmetic mean of the vertical support forces FG and FD measured at time T1, in other words: M(T1) = (FG(T1) + FD(T1)) / 2; M(T2) is an arithmetic mean of the vertical support forces FG and FD measured at time T2, in other words: M(T2) = (FG(T2) + FD(T2)) / 2. Alternatively, M(T1) and M(T2) can be calculated differently, for example as a geometric or harmonic mean.

[0052] In step 1030, it is determined whether the absolute difference between the second mean M(T2) and the first mean M(T1) exceeds a vertical force threshold S_C. In other words, it is determined whether the inequality: M T 2 − M T 1 > S_C is verified or not, where the value of S_C is strictly positive and therefore non-zero.

[0053] In the negative (“N” on the figure 6 In other words, if inequality (11) is not satisfied, process 1000 proceeds to a step 1040 in which FG(T1) and FD(T1) are replaced in memory by FG(T2) and FD(T2), that is: FG(T1) ← FG(T2) and FD(T1) ← FG(T2), and to a step 1045 in which an indication of the longitudinal stability of the handling machine 1 is provided as a function of the stress CG(T1) measured at time T1. Process 1000 then returns to step 1010.

[0054] If yes ("Y" on the figure 6 In other words, if inequality (11) is satisfied, process 1000 proceeds to a step 1050 in which FG(T1), FD(T1) and CG(T1) are replaced in memory by FG(T2), FD(T2) and CG(T2), that is: FG(T1) ← FG(T2), FD(T1) ← FG(T2), CG(T1) ← CG(T2), and to a step 1055 in which an indication of the longitudinal stability of the handling machine 1 is provided as a function of the stress CG(T2) measured at time T2. Process 1000 then returns to step 1010.

[0055] The longitudinal stability indication delivered at step 1045 and step 1055 can be determined in various ways, for example by comparing the stress CG(T1) or CG(T2) (as appropriate) to several thresholds different from each other.

[0056] The longitudinal stability indicator can be displayed on the display unit 9, controlled by the processing unit 8, for example, as a green-orange-red color code, with green indicating good longitudinal stability, orange indicating acceptable longitudinal stability, and red indicating poor longitudinal stability. Optionally, in the event of poor longitudinal stability, the processing unit 8 can activate the loudspeaker 9A to alert the operator of the handling machine 1.

[0057] In addition or as an alternative, the longitudinal stability indication can be taken into account by the processing unit 8 to stop one or more movements likely to cause the handling machine 1 to tip forward around the front axle 5. For example, in the event of poor longitudinal stability, the processing unit 8 can cut off the lifting actuator to prevent further lifting of the lifting arm 3, and / or cut off the extension actuator of the lifting arm 3 to prevent further deployment of the lifting arm 3 when it is telescopic.

[0058] Method 1000 is based on the observation that simply measuring the stress CG with the strain gauge 16 is not always sufficient to correctly determine the longitudinal stability of the handling machine 1. Indeed, as indicated above in relation to the prior art, this measurement can be affected by the steering of the rear wheels 6A. Therefore, with Method 1000, the absolute difference |M(T2) - M(T1)| is taken into account. If this absolute difference is greater than S_C, then the vertical support force of the chassis 2 on the front axle 5 has changed significantly between times T1 and T2, indicating that the longitudinal stability of the handling machine 1 has been significantly affected. It is therefore necessary to determine the longitudinal stability indicator based on the most recent measurement of the stress CG, namely CG(T2).Conversely, if the absolute difference is not greater than S_C, then the vertical load force of the chassis 2 on the front axle 5 has not changed significantly between times T1 and T2, indicating that the longitudinal stability of the handling machine 1 has not been significantly affected. A change in CG between times T1 and T2 is therefore not indicative of the longitudinal stability of the handling machine 1, particularly because it could be due to the steering of the rear wheels 6A. This is why the longitudinal stability indicator is determined as a function of CG(T1), and not as a function of CG(T2).

[0059] The value of S_C can be fixed according to various characteristics of the handling machine 1 and / or the time step ΔT.

[0060] It should be noted that in process 1000, the determination of the longitudinal stability indication delivered in step 1045 is carried out as a function of CG(T1) to the exclusion of other quantities measured by the sensor system 100. This does not, however, preclude the longitudinal stability indication from being delivered as a function of one or more quantities that are not measured by the sensor system 100 but are stored in memory in the processing unit 8, for example the mass of the handling machine 1 and / or a mass distribution of the handling machine 1. Similarly, the determination of the longitudinal stability indication delivered in step 1055 is carried out as a function of CG(T2) to the exclusion of other quantities measured by the sensor system 100.

[0061] With reference to the figure 7 A stability indication process 2000 is described according to another embodiment. The steps of process 2000 that are identical to those of process 1000 bear the same reference numbers and are not described again except where necessary.

[0062] The 2000 method differs from the 1000 method in that it also considers a drift D in the measurement of the stress CG by the strain gauge 16. More specifically: Step 1040 is replaced by a step 2040 in which, in addition to performing the memory assignments FG(T1) ← FG(T2) and FD(T1) ← FG(T2), the drift D is calculated as the arithmetic difference between CG(T2) and CG(T1): D ← CG(T2) - CG(T1). Step 1045, on the other hand, remains unchanged; that is, the longitudinal stability indication is provided as a function of CG(T1) to the exclusion of other quantities measured by the sensor system 100, without taking into account the drift D calculated in step 1040; Step 1050 is replaced by a step 2050 in which, in addition to performing the memory assignments FG(T1) ← FG(T2), FD (T1) ← FG(T2), CG (T1) ← CG(T2), CG(T2) is corrected according to the drift D, for example by subtracting the drift D: CG (T2) ← CG(T2) - D; unlike step 1055, the longitudinal stability indication delivered in step 2055 is determined according to CG(T2) thus corrected.

[0063] In this way, the longitudinal stability indication delivered at step 2055 is determined not only based on the most recent measurement of the CG stress, namely CG(T2), but also taking into account previous measurements of the CG stress thanks to the drift D. This tends to make the longitudinal stability indication delivered at step 2055 more reliable.

[0064] With reference to the figure 8 A stability indication process 3000 is described according to yet another embodiment. The steps of process 3000 that are identical to those of process 1000 bear the same reference numbers and are not described again except where necessary.

[0065] The 3000 method differs from the 1000 method in that it also considers an arithmetic difference between M(T2) and M(T1) to correct the measurement of the CG stress by the strain gauge 16. More specifically: Step 1050 is replaced by a step 3050 in which, in addition to performing the memory assignments FG(T1) ← FG(T2) and FD (T1) ← FG(T2), the quantity CGcorr = CG(T1) - C_C_J * (M(T2) - M(T1)) is calculated before performing the memory assignment CG (T1) ← CG(T2); step 3055 is identical to step 1055 except that the longitudinal stability indication is determined as a function of CGcorr and not of CG(T2).

[0066] C_C_J designates a strictly positive (and therefore non-zero) conversion factor between the force sensors 15G, 15D and the strain gauge 16. In this way, the longitudinal stability indication provided in step 3055 is determined not only based on a measurement of the stress CG, but also by taking into account the evolution of the vertical support force of the chassis 2 on the front axle 5 between times T1 and T2. This tends to make the longitudinal stability indication provided in step 3055 more reliable.

[0067] With reference to the figure 9 , a stability indication method 4000 is described according to yet another embodiment, to indicate both longitudinal stability of the handling machine 1 and lateral stability of the handling machine 1. The steps described below of method 4000 can be implemented by the processing unit 8.

[0068] To indicate the longitudinal stability of the handling machine 1, process 4000 implements the steps described above from process 1000, 2000 or 3000, and in addition the steps shown on the figure 9 .

[0069] In step 4010, analogous to step 1010, the vertical support force FG and the vertical support force FD at time T2 are acquired and stored in memory. Prior to step 4010, the vertical support force FG, the vertical support force FD, and the stress CG at time T1 were stored in memory.

[0070] In step 4020, the first mean M(T1) and the second mean M(T2) are calculated analogously to step 1020. In addition, a first deviation DG(T1) and a second deviation DG(T2) are calculated, where: DG(T1) is a difference between the vertical support force FG measured at time T1 and the first average M(T1), in other words: DG(T1) = FG(T1) - M(T1); DG(T2) is a difference between the vertical support force FG measured at time T2 and the second average M(T2), in other words: DG(T2) = FG(T2) - M(T2).

[0071] In step 4060, it is determined whether the absolute difference between the second deviation DG(T2) and the first deviation DG(T1) exceeds a differential vertical force threshold S_C_D. In other words, it is determined whether the inequality: DG T 2 − DG T 1 > S_C_D is verified or not, where the value of S_C_D is strictly positive and therefore not zero.

[0072] In the negative (“N” on the figure 9 In other words, if inequality (I2) is not satisfied, process 4000 proceeds to step 4070 (identical to step 1040) in which FG(T1) and FD(T1) are replaced in memory by FG(T2) and FD(T2), that is: FG(T1) ← FG(T2) and FD(T1) ← FG(T2), and to step 4075 in which a lateral stability indication of the handling machine 1 is provided as a function of the first deviation DG(T1). Process 4000 then returns to step 4010.

[0073] If yes ("Y" on the figure 9 In other words, if inequality (I2) is satisfied, process 4000 proceeds to step 4080, identical to step 4070, and to step 4085, in which a lateral stability indication of the handling machine 1 is provided as a function of the second deviation DG(T2). Process 4000 then returns to step 4010.

[0074] The lateral stability indication delivered at step 4075 and step 4085 can be determined in various ways, for example by comparing the deviation DG(T1) or DG(T2) to several thresholds different from each other.

[0075] The lateral stability indicator can be displayed in conjunction with the longitudinal stability indicator on the display unit 9, controlled by the processing unit 8, and optionally according to a color code as described above for the longitudinal stability indicator. Optionally, in the event of poor lateral stability, the processing unit 8 can activate the loudspeaker 9A to alert the operator of the handling machine 1.

[0076] In addition or as an alternative, the lateral stability indication can be taken into account by the processing unit 8 to stop one or more movements likely to cause the handling machine 1 to tip over on its side.

[0077] Method 4000 is based on the observation that force sensors 15G, 15D can also be used to determine the lateral stability of the handling machine 1. Therefore, with method 4000, the absolute value difference |DG(T2) - DG(T1)| is taken into account. If this absolute value difference is greater than S_C_D, then the distribution of the vertical support force of the chassis 2 on the front axle 5 along the front axle 5 has changed significantly between times T1 and T2, and it is therefore necessary to determine the lateral stability indication based on the most recent measurements of the vertical support forces FG and FD, and thus based on DG(T2).Conversely, if the difference in absolute value is not greater than S_C_D, then the distribution of the vertical support force of the chassis 2 on the front axle 5 along the front axle 5 has not significantly changed between times T1 and T2, and the lateral stability indication is determined as a function of DG(T1).

[0078] The value of S_C_D can be fixed according to various characteristics of the handling machine 1 and / or the time step ΔT.

[0079] Although steps 4020 and subsequent steps of process 4000 have been described in terms of a difference between the vertical support force FG(T1) or FG(T2) and M(T1) or M(T2), it is quite clear that FD can be considered instead of FG, since the roles of FG and FD are symmetrical. Indeed, FD(T1) - M(T1) is equal in absolute value to FG(T1) - M(T1) and has the opposite sign.

[0080] The invention is not limited to the embodiments illustrated in the drawings.

[0081] Furthermore, the term "including" does not exclude other elements or steps. In addition, features or steps described with reference to one of the embodiments set out above may also be used in combination with other features or steps from other embodiments set out above.

Claims

1. A material handling machine (1) comprising a chassis (2), a material handling system (300) carried by the chassis (2), a front axle (5) and a rear axle (6) supporting the chassis (2) on the ground, and a sensor system (100), wherein the front axle (5) is a non-oscillating axle and the rear axle (6) is an oscillating axle, wherein the sensor system (100) comprises a strain gauge (16) disposed on the rear axle (6), and two force sensors (15G, 15D) each fixed to the front axle (5) spaced along a transverse direction (Y) of the material handling machine (1), each force sensor (15G, 15D) further being fixed to the chassis (2) or in contact with the chassis (2) so as to measure a vertical bearing force of the chassis (2) on said force sensor (15G, 15D), the material handling machine (1) further comprising a processing unit (8) connected to the sensor system (100),the processing unit (8) being configured to: - calculate (1020) a first average (M(T1)) and a second average (M(T2)), the first average (M(T1)) being an average of the vertical support forces (FG, FD) measured by the two force sensors (15G, 15D) at a first instant (T1), and the second average (M(T2)) being an average of the vertical support forces (FG, FD) measured by the two force sensors (15G, 15D) at a second instant (T2) subsequent to the first instant (T1); - determine (1030) if a difference in absolute value between the second average and the first average is greater than a first threshold (S_C), the first threshold being non-zero; and - if negative, provide (1045) an indication of the longitudinal stability of the handling machine (1) as a function of the stress (CG(T1)) measured by the strain gauge (16) at the first instant; - if affirmative, provide (1055,2055) said longitudinal stability indication as a function of at least the stress (CG(T2)) measured by the strain gauge (16) at the second instant or as a function of the stress (CG(T1)) measured by the strain gauge (16) at the first instant corrected as a function of an arithmetic difference between the second mean (M(T2)) and the first mean (M(T1))., 2. Handling machine (1) according to claim 1, wherein the two force sensors (15G, 15D) are fixed on the front axle (5) on either side of a longitudinal axis (X) of the handling machine (1), the longitudinal axis (X) being orthogonal to the transverse direction (Y) of the handling machine (1).

3. Handling machine (1) according to any one of claims 1 to 2, wherein the processing unit (8) is configured to: - if it is determined that said difference in absolute value is greater than the first threshold (S_C), deliver (1055) said longitudinal stability indication as a function of the stress (CG(T2)) measured by the strain gauge (16) at the second instant to the exclusion of other quantities measured by the sensor system (100).

4. Handling machine (1) according to any one of claims 1 to 2, wherein the processing unit (8) is configured to: - if it is determined that said difference in absolute value is not greater than the first threshold (S_C), calculate (2040) a drift (D) of the strain gauge (16), the drift (D) being an arithmetic difference between the stress (CG(T2)) measured by the strain gauge (16) at the second instant and the stress (CG(T1)) measured by the strain gauge (16) at the first instant, and deliver (1045) said longitudinal stability indication as a function of the stress (CG(T1)) measured by the strain gauge (16) at the first instant uncorrected as a function of said drift (D);- if it is determined that said difference in absolute value is greater than the first threshold (S_C), deliver (2055) said indication of longitudinal stability as a function of the stress (CG(T2)) measured by the strain gauge (16) at the second instant corrected as a function of said drift (D).; 5. Handling machine (1) according to any one of claims 1 to 2, wherein the processing unit (8) is configured to: - if it is determined that said difference in absolute value is greater than the first threshold (S_C), deliver (3055) said longitudinal stability indication as a function of the stress (CG(T1)) measured by the strain gauge (16) at the first instant corrected as a function of an arithmetic difference between the second mean (M(T2)) and the first mean (M(T1)).

6. Handling machine (1) according to any one of claims 1 to 5, wherein the handling machine (1) further comprises a display unit (9) connected to the processing unit (8), and wherein the processing unit (8) is further configured to control the display of the longitudinal stability indication on the display unit (9).

7. Handling machine (1) according to claim 6, wherein the handling machine (1) further comprises a cabin (4), the display unit (9) being arranged in the cabin (4).

8. Handling machine (1) according to any one of claims 1 to 7, wherein the processing unit (8) is further configured to: - calculate (4020) a first deviation (DG(T1)) and a second deviation (DG(T2)), the first deviation being a difference between the vertical support force measured by a force sensor (15G) among the two force sensors (15G, 15D) at the first instant and the first average (M(T1)), and the second deviation being a difference between the vertical support force measured by said force sensor (15G) at the second instant and the second average (M(T2)); - determine (4060) whether a difference in absolute value between the second deviation and the first deviation is greater than a second threshold (S_C_D), the second threshold being non-zero; - if not, provide (4075) a lateral stability indication of the handling machine (1) as a function of the first deviation (DG(T1));- if so, deliver (4085) said lateral stability indication as a function of the second deviation (DG(T2)).; 9. Handling machine (1) according to claim 8 taken in combination with any one of claims 6 to 7, wherein the processing unit (8) is further configured to control the display of the lateral stability indication on the display unit (9).

10. Handling machine (1) according to any one of claims 1 to 9, wherein the first instant (T1) and the second instant (T2) are separated by at most 10 milliseconds.

11. A method (1000, 2000, 3000, 4000) for indicating the stability of a material handling machine (1) comprising a chassis (2), a material handling system (300) carried by the chassis (2), a front axle (5) and a rear axle (6) supporting the chassis (2) on the ground, and a sensor system (100), wherein the front axle (5) is a non-oscillating axle and the rear axle (6) is an oscillating axle, wherein the sensor system (100) comprises a strain gauge (16) disposed on the rear axle (6), and two force sensors (15G, 15D) each fixed to the front axle (5) spaced apart along a transverse direction (Y) of the material handling machine (1), each force sensor (15G, 15D) further fixed to the chassis (2) or in contact with the chassis (2) so as to measure a vertical support force of the chassis (2) on said force sensor (15G, 15D), the method comprising: - calculating (1020) a first average (M(T1)) and a second average (M(T2)),the first average (M(T1)) being an average of the vertical support forces (FG, FD) measured by the two force sensors (15G, 15D) at a first instant (T1), and the second average (M(T2)) being an average of the vertical support forces (FG, FD) measured by the two force sensors (15G, 15D) at a second instant (T2) subsequent to the first instant (T1); - determine (1030) if a difference in absolute value between the second average and the first average is greater than a first threshold (S_C), the first threshold being non-zero; and - if negative, provide (1045) an indication of the longitudinal stability of the handling machine (1) as a function of the stress (CG(T1)) measured by the strain gauge (16) at the first instant; - if positive, provide (1055,2055) said longitudinal stability indication as a function of at least the stress (CG(T2)) measured by the strain gauge (16) at the second instant or as a function of the stress (CG(T1)) measured by the strain gauge (16) at the first instant corrected as a function of an arithmetic difference between the second mean (M(T2)) and the first mean (M(T1))., 12. Method (1000) according to claim 11, wherein the method comprises: - if it is determined that said difference in absolute value is greater than the first threshold (S_C), delivering (1055) said longitudinal stability indication as a function of the stress (CG(T2)) measured by the strain gauge (16) at the second instant to the exclusion of other quantities measured by the sensor system (100).

13. Method (2000) according to claim 11, wherein the method comprises: - if it is determined that said difference in absolute value is not greater than the first threshold (S_C), calculate (2040) a drift (D) of the strain gauge (16), the drift (D) being an arithmetic difference between the stress (CG(T2)) measured by the strain gauge (16) at the second instant and the stress (CG(T1)) measured by the strain gauge (16) at the first instant, and deliver (1045) said longitudinal stability indication as a function of the stress (CG(T1)) measured by the strain gauge (16) at the first instant uncorrected as a function of said drift (D); - if it is determined that said difference in absolute value is greater than the first threshold (S_C), deliver (2055) said indication of longitudinal stability as a function of the stress (CG(T2)) measured by the strain gauge (16) at the second instant corrected as a function of said drift (D).

14. Method (3000) according to claim 11, wherein the method comprises: - if it is determined that said difference in absolute value is greater than the first threshold (S_C), delivering (3055) said longitudinal stability indication as a function of the stress (CG(T1)) measured by the strain gauge (16) at the first instant corrected as a function of an arithmetic difference between the second mean (M(T2)) and the first mean (M(T1)).

15. A method (4000) according to any one of claims 11 to 14, wherein the method further comprises: - calculating (4020) a first deviation (DG(T1)) and a second deviation (DG(T2)), the first deviation being a difference between the vertical support force measured by a force sensor (15G) among the two force sensors (15G, 15D) at the first instant and the first average (M(T1)), and the second deviation being a difference between the vertical support force measured by said force sensor (15G) at the second instant and the second average (M(T2)); - determining (4060) whether a difference in absolute value between the second deviation and the first deviation is greater than a second threshold (S_C_D), the second threshold being non-zero; - if not, providing (4075) an indication of the lateral stability of the handling machine (1) as a function of the first deviation (DG(T1)); - if so, deliver (4085) said lateral stability indication as a function of the second deviation (DG(T2)).

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