Method for controlling a fuel cell in a work machine

Abstract

The invention relates to a method for controlling a fuel cell (18) of a work machine (1), the method comprising the following steps: - determining an operating mode of the work machine (1) from among at least two operating modes as a function of at least one variable chosen from: a "driver presence" variable (V2); a "motor speed" variable; a "machine speed" variable (V3); a "loading mode activity" variable (V4); a "stabilizer" variable (V5); a "recharge" variable (V6); a "control activity" variable (V1); - determining a state of charge of the energy storage unit (10); and - controlling the fuel cell (18) with a predetermined setpoint as a function of the state of charge of the energy storage unit (10) and the operating mode of the work machine thus determined. Figure for the abstract: Fig. 3

Description

Description of the invention: Method for controlling a fuel cell of a work machine technical field The invention relates to the field of work machines comprising a load-handling device, an electric motor configured to move the work machine or operate the load-handling device, an energy storage unit configured to supply the electric motor with electrical energy, and a fuel cell generating electrical energy to power the electric motor. Such a machine may, in particular, be implemented in the form of a telescopic handler, excavator, bucket loader, or other similar equipment. The invention relates more particularly to the field of control methods for a fuel cell of a work machine. Technological background It is known from prior art, and in particular from document WO2008041892, that construction equipment includes a power source, which may be an internal combustion engine or a fuel cell, and several power-consuming systems connected to the power source. The equipment also includes an external power source, which may be a battery. This document also relates to a method for operating the work machine, which, following the detection of an operational power demand parameter such as a brake pedal press, balances the supplied power with the demanded power according to a real-time forecasting model that takes into account the detection of the operational parameter. When the demanded power exceeds the supplied power, balancing is achieved by adding the torque of the external power source to the torque of the primary power source. The external power source thus provides the additional power predicted by the forecasting model, at least temporarily to allow sufficient time for the primary source to reach the required power. However, such a process is complex to implement and requires powerful computers to calculate the predicted power output of the device in real time. Furthermore, with such a process, and in the case of a fuel cell as the power source, the fuel cell's setpoint must be constantly adjusted as soon as the power demand changes, which can prematurely damage the fuel cell. Summary One idea behind the invention is to simplify the control of the fuel cell. According to one embodiment, the invention provides a method for controlling a fuel cell of a work machine comprising a load handling device formed of an arm and a tool, at least one electric motor configured to move the work machine and / or actuate the load handling device, an energy storage unit configured to supply energy to at least one electric motor and a fuel cell connected to the energy storage unit and configured to charge the energy storage unit, a first control element configured to control the electric motor and a second control element configured to control the load handling device, the method comprising the following steps: - determine one operating mode of the work machine from among at least two operating modes as a function of at least one variable chosen from: a "driver presence" variable representing the presence of a person in a driver's seat of the work machine; a variable "machine speed" representing the speed of movement of the working machine: a variable "loading mode activity" representative of the activity of the load handling device; a "stabilizer" variable representing the position of one or more stabilizers; a "recharge" variable representing the state of a button that activates a recharge mode; and a "control activity" variable representing the activity of the first control unit and / or the second control unit; - determine the state of charge of the energy storage unit; and - control the fuel cell with a predetermined setpoint based on the state of charge of the energy storage unit and the operating mode of the working machine thus determined. Thanks to these features, the control method allows for simple control of the fuel cell by identifying operating modes and the state of charge of the energy storage unit. Indeed, determining the operating mode allows for a straightforward evaluation of the power required from the energy storage unit using various variables, thus adapting the fuel cell setpoint to charge the storage unit as needed. Furthermore, the method allows for adapting the fuel cell setpoint based on the state of charge of the energy storage unit, for example, by providing for a more or less important setpoint power of the fuel cell depending on whether the energy storage unit is lightly charged, moderately charged or fully charged. According to some embodiments, such a process may include one or more of the following characteristics. According to one embodiment, the work machine includes a first electric motor which is configured to move the work machine and a second electric motor which is configured to operate the load handling device. According to one embodiment, the operating mode of the working machine can also be determined as a function of a "motor speed" variable representing the speed of the second electric motor which is configured to operate the load handling device. According to one embodiment, one of the operating modes is an idle mode which is determined by means of the variable "driver presence", the variable "control activity" and optionally the aforementioned variable "engine speed". According to one embodiment, the process comprises the following steps: - receive the variable "driver presence" and the variable "control activity", the variable "driver presence" being able to take a first value when a person is present on a driver's seat of the machine and a second value when no person is present on the driver's seat, the variable "control activity" being able to take a first value when the first control element and the second control element are in a neutral position and being able to take a second value when the first control element or the second control element is in an active position; - determine that the operating mode is the idle mode when the variable "control activity" is equal to the first value and the variable "driver presence" is equal to the second value. According to one embodiment, the process comprises the following steps: - receive the variable "driver presence", the variable "control activity" and the variable "engine speed", the variable "driver presence" being able to take a first value when a person is present on a driver's seat of the machine and a second value when no person is present on the driver's seat, the variable "control activity" being able to take a first value when the first control element and the second control element are in a neutral position and being able to take a second value when the first control element or the second control element is in an active position; - compare the variable "engine speed" to a predetermined engine speed threshold, - determine that the operating mode is idle mode when the variable "engine speed" has a value below the pre-determined engine speed threshold, the variable "control activity" is equal to the first value and the variable "driver presence" is equal to the second value. According to one embodiment, one of the operating modes is an idle mode determined by means of the variable "recharge", and the variable "control activity", and optionally the variable "engine speed". According to one embodiment, the process comprises the following steps: - receive the variable "recharge" and the variable "command activity", the variable "recharge" being able to take a first value when the recharge mode activation button is in the active state and a second value when the recharge mode activation button is in the inactive state, the variable "command activity" being able to take a first value when the first control element and the second control element are in a neutral position and being able to take a second value when the first or second control element is in an active position; - determine that the operating mode is the idle mode when the variable "control activity" is equal to the first value and the variable "recharge" is equal to the second value. According to one embodiment, the process comprises the following steps: - receive the variable "recharge", the variable "control activity" and the variable "motor speed", the variable "recharge" being able to take a first value when the recharge mode activation button is in the active state and a second value when the recharge mode activation button is in the inactive state, the variable "control activity" being able to take a first value when the first control element and the second control element are in a neutral position and being able to take a second value when the first or second control element is in an active position; - compare the variable "engine speed" to a predetermined engine speed threshold, - determine that the operating mode is idle mode when the variable "engine speed" has a value below the pre-determined engine speed threshold, the variable "control activity" is equal to the first value and the variable "recharge" is equal to the second value. According to one embodiment, the first control element is a three-position selector switch (forward / neutral / reverse), the selector being capable of assuming three positions: the neutral position, a forward position, and a reverse position. The selector is in an active position in the forward position, which is configured to issue a request for forward movement of the work machine, and in the reverse position, which is configured to deliver a request to move the work machine in reverse. In one embodiment, the second control element is a joystick capable of being tilted upwards, downwards, to the right, or to the left. Tilting the joystick upwards sends a request to lower the arm, tilting it downwards sends a request to raise the arm, and tilting it to the left or right sends a request to tilt the tool in one direction or the other. According to one embodiment, when the first control element is a three-position selector and the second control element is a joystick, the variable "control activity" is able to take the first value when the three-position selector is in the neutral position and the joystick is in the neutral position, not toggled by a user, and is able to take a second value when the three-position selector is in the forward or backward position, or the joystick has been toggled by a user from the neutral position. According to one embodiment, the variable "driver presence" is obtained using a presence sensor configured to deliver a signal when a mass measurement on the seat greater than a determined mass threshold is detected on the seat, the method comprising a step of comparing a measurement of the mass exerted on the seat to a value of the determined mass threshold, the value of the determined mass threshold being for example greater than 10 kg, more preferably greater than 15 kg, and a step of assigning to the variable "driver presence" the first value when the mass measurement is greater than said predetermined mass threshold. According to one embodiment, the electric motor includes a motor shaft and the variable "motor speed" is measured using a speed sensor delivering a representative measurement of the rotational speed of the motor shaft of the electric motor, for example a capacitive Hall effect sensor. According to one embodiment, the predetermined motor speed threshold is equal to the speed value of the electric motor in idle mode plus a constant, said predetermined motor speed threshold being for example between 50 rpm and 1000 rpm, preferably between 100 rpm and 500 rpm, for example equal to 300 rpm. According to one embodiment, one of the operating modes is a charging mode which is determined by means of the variable "driver presence", the variable "charging", the variable "control activity", and optionally the variable "engine speed". According to one embodiment, the process comprises the following steps: - receive the variable "driver presence", the variable "command activity", and the variable "recharge", the variable "driver presence" being able to take a first value when a person is present on a seat of the machine and a second value when no person is present on the seat, the variable "recharge" being able to take a first value when the recharge mode activation button is in the active state and a second value when the recharge mode activation button is in the inactive state, the variable "control activity" being able to take a first value when the first control element and the second control element are in a neutral position and being able to take a second value when the first or second control element is in an active position; - determine that the operating mode is the charging mode when the variable "command activity" is equal to the first value, the variable "driver presence" is equal to the first value and the value "charging" is equal to the first value. According to one embodiment, the process comprises the following steps: - receive the variable "driver presence", the variable "control activity", the variable "engine speed" and the variable "recharge", the variable "driver presence" being able to take a first value when a person is present on a seat of the machine and a second value when no person is present on the seat, the variable "recharge" being able to take a first value when the recharge mode activation button is in the active state and a second value when the recharge mode activation button is in the inactive state, the variable "control activity" being able to take a first value when the first control element and the second control element are in a neutral position and being able to take a second value when the first control element or the second control element is in an active position; - compare the variable "engine speed" to a predetermined engine speed threshold, - determine that the operating mode is the recharge mode when the variable "engine speed" has a value lower than the pre-determined engine speed threshold, the variable "control activity" is equal to the first value, the variable "driver presence" is equal to the first value and the value "recharge" is equal to the first value. According to one embodiment, one of the operating modes is a road mode which is determined by means of the variable "machine speed", optionally the variable "engine speed", and optionally the variable "control activity" According to one embodiment, the process comprises the following steps: - receive the variable "machine speed", - compare the variable "machine speed" to a pre-defined machine speed threshold determined, - determine that the operating mode is road mode when the variable "machine speed" has a value greater than the pre-determined machine speed threshold. According to one embodiment, the process comprises the following steps: - receive the variable "machine speed" and the variable "control activity", the variable "control activity" being able to take a first value when the first control element and the second control element are in a neutral position and being able to take a second value when the first or second control element is in an active position - compare the variable "machine speed" to a predetermined machine speed threshold, - determine that the operating mode is route mode when the variable "control activity" is equal to the second value and the variable "machine speed" has a value greater than the predetermined machine speed threshold. According to one embodiment, the process comprises the following steps: - receive the variable "machine speed", the variable "control activity" and the variable "motor speed", the variable "control activity" being able to take a first value when the first control element and the second control element are in a neutral position and being able to take a second value when the first control element or the second control element is in an active position; - compare the variable "engine speed" to a predetermined engine speed threshold, - compare the variable "machine speed" to a predetermined machine speed threshold, - determine that the operating mode is road mode when the variable "engine speed" has a value greater than the pre-determined engine speed threshold and the variable "machine speed" has a value greater than the predetermined machine speed threshold, or when the value of the variable "control activity" is equal to the second value and the variable "machine speed" has a value greater than the predetermined machine speed threshold. According to one embodiment, the "machine speed" value is measured using a speed sensor, for example a capacitive Hall effect sensor located in a gearbox or on a rear axle. According to one embodiment, the predetermined machine speed threshold is for example between 10 and 30 km / h, preferably between 10 and 20 km / h, for example equal to 16 km / h. According to one embodiment, one of the modes of operation is a mode loading which is determined by means of the variable "machine speed", the variable "control activity", the variable "loading mode activity", and optionally the variable "engine speed". According to one embodiment, the process comprises the following steps: - receive the variable "machine speed", the variable "control activity", and the variable "loading mode activity", the variable "loading mode activity" being able to take a first value in response to the detection of a hydraulic flow setpoint of a tool tilt cylinder within a predetermined range for a duration greater than a predetermined duration threshold and to the detection of an arm angle within a predetermined range, and to take a second value otherwise, the variable "control activity" being able to take a first value when the first control element and the second control element are in a neutral position and being able to take a second value when the first control element or the second control element is in an active position; - compare the variable "machine speed" to a predetermined machine speed threshold, - determine that the operating mode is the loading mode when the variable "control activity" is equal to the second value, the variable "machine speed" has a value lower than the predetermined machine speed threshold, and the variable "loading mode activity" is equal to the first value. According to one embodiment, the process comprises the following steps: - receive the variable "machine speed", the variable "engine speed", the variable "control activity", and the variable "loading mode activity", the variable "loading mode activity" being capable of taking a first value in response to the detection of a hydraulic flow setpoint of a tool tilt cylinder within a predetermined range for a duration exceeding a predetermined time threshold and to the detection of an arm angle within a predetermined range and to taking a second value otherwise, the variable "control activity" being capable of taking a first value when the first control element and the second control element are in a neutral position and being capable of taking a second value when the first or second control element is in an active position; - compare the variable "engine speed" to a predetermined engine speed threshold, - compare the variable "machine speed" to a predetermined machine speed threshold, - determine that the operating mode is the loading mode when the "engine speed" variable has a value greater than the engine speed threshold predetermined, the variable "machine speed" has a value less than the predetermined machine speed threshold, and the variable "loading mode activity" is equal to the first value, or when the value of the variable "control activity" is equal to the second value, the variable "machine speed" has a value less than the predetermined machine speed threshold, and the variable "loading mode activity" is equal to the first value. In one embodiment, the hydraulic flow setpoint of a tool tilt cylinder is detected by means of a flow sensor mounted on the tilt cylinder. The hydraulic flow setpoint of the tilt cylinder is, for example, between -100% and -30% of the predetermined maximum flow rate of the tilt cylinder and between 30% and 100% of the predetermined maximum flow rate of the tilt cylinder. Negative flow values ​​correspond to the tool tilting in the loading direction, and positive values ​​correspond to the tool tilting in the dumping direction. The predetermined time threshold is, for example, greater than 1 second (sec), preferably between 1 and 2 sec, and more preferably equal to 1.5 sec. In one embodiment, the detection of an arm angle is performed by means of an angle sensor located near the arm. The predetermined range is, for example, between 0 and 10° and between 30 and 70°. According to one embodiment, one of the operating modes is a handling mode determined by means of the variable "machine speed", the variable "loading mode activity", the variable "stabilizer", the variable "control activity", and optionally the variable "motor speed". According to one embodiment, the process comprises the following steps: - receive the variable "machine speed", the variable "control activity", the variable "loading mode activity", and the variable "stabilizer"; the variable "loading mode activity" being able to take a first value in response to the detection of a hydraulic flow setpoint of a tool tilt cylinder within a predetermined range for a duration greater than a predetermined duration threshold and to the detection of an arm angle within a predetermined range, and to take a second value otherwise;the variable "stabilizer" being able to take a first value when at least one stabilizer is in an operating position and being able to take a second value when no stabilizer is in the operating position, the variable "control activity" being able to take a first value when the first control element and the second control element are in a neutral position and being able to take a second value when the first or second control element is in an active position; ; - compare the variable "machine speed" to a predetermined machine speed threshold, - determine that the operating mode is the handling mode when the variable "control activity" is equal to the second value, the variable "machine speed" has a value lower than the predetermined machine speed threshold, the variable "activity of the load handling device" is equal to the first value, and the variable "stabilizer" is equal to the second value. According to one embodiment, the process comprises the following steps: - receive the variable "machine speed", the variable "engine speed", the variable "control activity", the variable "loading mode activity", and the variable "stabilizer"; the variable "loading mode activity" being able to take a first value in response to the detection of a hydraulic flow setpoint of a tool tilt cylinder within a predetermined range for a duration greater than a predetermined duration threshold and to the detection of an arm angle within a predetermined range, and to take a second value otherwise;the variable "stabilizer" being able to take a first value when at least one stabilizer is in an operating position and being able to take a second value when no stabilizer is in the operating position, the variable "control activity" being able to take a first value when the first control element and the second control element are in a neutral position and being able to take a second value when the first or second control element is in an active position; - compare the variable "engine speed" to a predetermined engine speed threshold, - compare the variable "machine speed" to a predetermined machine speed threshold, - determine that the operating mode is the handling mode when the variable "engine speed" has a value greater than the predetermined engine speed threshold, the variable "machine speed" has a value less than the predetermined machine speed threshold, the variable "activity of the load handling device" is equal to the first value, and the variable "stabilizer" is equal to the second value or when the value of the variable "control activity" is equal to the second value, the variable "machine speed" has a value less than the predetermined machine speed threshold, the variable "activity of the load handling device" is equal to the first value, and the variable "stabilizer" is equal to the second value. According to one embodiment, one of the operating modes is a handling mode on a stabilizer which is determined by means of the variable "machine speed", the variable "loading mode activity", the variable "stabilizer", of the "control activity" variable and optionally of the "motor speed" variable. According to one embodiment, the process comprises the following steps: - receive the variable "machine speed", the variable "control activity", the variable "loading mode activity", and the variable "stabilizer"; the variable "loading mode activity" being able to take a first value in response to the detection of a hydraulic flow setpoint of a tool tilt cylinder within a predetermined range for a duration greater than a predetermined duration threshold and to the detection of an arm angle within a predetermined range;the variable "stabilizer" being able to take a first value when at least one stabilizer is in an operating position and being able to take a second value when no stabilizer is in the operating position, the variable "control activity" being able to take a first value when the first control element and the second control element are in a neutral position and being able to take a second value when the first or second control element is in an active position; - compare the variable "machine speed" to a predetermined machine speed threshold, - determine that the operating mode is the handling mode on stabilizer when the variable "control activity" is equal to the second value, the variable "machine speed" has a value lower than the predetermined machine speed threshold, the variable "activity of the load handling device" is equal to the first value, and the variable "stabilizer" is equal to the first value. According to one embodiment, the process comprises the following steps: - receive the variable "machine speed", the variable "engine speed", the variable "control activity", the variable "loading mode activity", and the variable "stabilizer"; the variable "loading mode activity" being able to take a first value in response to the detection of a hydraulic flow setpoint of a tool tilt cylinder within a predetermined range for a duration greater than a predetermined duration threshold and to the detection of an arm angle within a predetermined range;the variable "stabilizer" being able to take a first value when at least one stabilizer is in an operating position and being able to take a second value when no stabilizer is in the operating position, the variable "control activity" being able to take a first value when the first control element and the second control element are in a neutral position and being able to take a second value when the first control element or the second element; the control is in an active position; - compare the variable "engine speed" to a predetermined engine speed threshold, - compare the variable "machine speed" to a predetermined machine speed threshold, - determine that the operating mode is the handling mode on stabilizer when the variable "engine speed" has a value greater than the predetermined engine speed threshold, the variable "machine speed" has a value less than the predetermined machine speed threshold, the variable "activity of the load handling device" is equal to the first value, and the variable "stabilizer" is equal to the first value or when the value of the variable "control activity" is equal to the second value, the variable "machine speed" has a value less than the predetermined machine speed threshold, the variable "activity of the load handling device" is equal to the first value, and the variable "stabilizer" is equal to the first value. According to one embodiment, the fuel cell control step comprises the following sub-steps: - compare the determined state of charge to a threshold state of charge, - when the state of charge is above the state of charge threshold, control the fuel cell with a predetermined setpoint having a first setpoint value, - when the state of charge is below the state of charge threshold, control the fuel cell with a predetermined setpoint having a second setpoint value, the second setpoint value being greater than the first setpoint value. According to one embodiment, the stage of determining the state of charge comprises the following sub-steps: - determine the state of charge at a given time t; - determine the state of charge at a time t+dt, dt being a pre-determined time interval; - compare the state of charge at time t and the state of charge at time t+dt; - when the state of charge at time t+dt is less than the state of charge at time t, determine that the energy storage unit is in discharge phase; - when the state of charge at time t+dt is greater than the state of charge at time t, determine that the energy storage unit is in the charging phase; in which the fuel cell control stage includes, during the discharge phase of the energy storage unit, the following sub-stages: - compare the determined state of charge to a first threshold of state of charge; - when the state of charge is above the first state of charge threshold, control the fuel cell with a predetermined setpoint having a first setpoint value, - when the state of charge is below the first state of charge threshold, command the fuel cell with a predetermined setpoint having a second setpoint value, the second setpoint value being greater than the first setpoint value; and in which the fuel cell control step includes, during the energy storage unit charging phase, the following sub-steps: - compare the determined state of charge to a second state of charge threshold, the first state of charge threshold being different from the second state of charge threshold, - when the state of charge is above the second state of charge threshold, control the fuel cell with a predetermined setpoint having the first setpoint value, - when the state of charge is below the second state of charge threshold, control the fuel cell with a predetermined setpoint having the second setpoint value. According to one embodiment, the second state of charge threshold is greater than the first state of charge threshold. According to one embodiment, the first and second setpoint values ​​correspond to two of the following setpoint values: - a "zero" setpoint value at which the fuel cell is switched off, - a "slowed down" setpoint value corresponding to a power delivered by the fuel cell between 2 and 25% of a maximum power of the fuel cell; - an "average" setpoint value corresponding to a power delivered by the fuel cell between 25 and 85% of the maximum power of the fuel cell; - a "maximum" setpoint value corresponding to a power delivered by the fuel cell greater than 85% of the maximum power of the fuel cell. According to one embodiment, the "average" setpoint value is adjusted over the lifetime of the working machine according to the following steps: - initialize the "average" setpoint value to a predetermined initial setpoint value, - calculate the average power delivered during one or more operating cycles of the working machine, - modify the "average" setpoint value according to the calculated average power. According to one embodiment, the fuel cell is a dihydrogen fuel cell. According to one embodiment, the energy storage unit comprises one or more batteries, for example of the lead-acid type or the lithium-ion type. According to one embodiment, the invention also provides a control unit for a work machine comprising a load-handling device consisting of an arm and a tool, at least one electric motor configured to move the work machine and / or actuate the load-handling device, an energy storage unit configured to supply energy to the electric motor, a fuel cell connected to the energy storage unit and configured to charge the energy storage unit, a first control element configured to control the electric motor, and a second control element configured to control the load-handling device, the control unit being configured to: - determine one operating mode of the work machine from among at least two operating modes as a function of at least one variable chosen from: a "driver presence" variable representing the presence of a person in a driver's seat of the work machine; a "machine speed" variable representing the speed of movement of the working machine; a variable "loading mode activity" representative of the activity of the load handling device; a "stabilizer" variable representing the position of one or more stabilizers; a "recharge" variable representing the state of a button activating a recharge mode; a "control activity" variable representing the activity of the first control unit and / or the second control unit; and - determine the state of charge of the energy storage unit; and - control the fuel cell with a predetermined setpoint based on the state of charge of the energy storage unit and the operating mode of the working machine thus determined. According to one embodiment, the invention also relates to a computer program product comprising program code instructions for executing the steps of a control process according to any of the embodiments proposed above, when said program is executed by a control unit. According to one embodiment, the invention also provides a work machine comprising a load-handling device consisting of an arm and a tool, at least one electric motor configured to move the work machine and / or actuate the load-handling device, an energy storage unit configured to supply energy to the electric motor, and a fuel cell connected to the energy storage unit and configured to charge the unit. energy storage, and in which the working machine includes a control unit according to any one of the embodiments. Brief description of the figures The invention will be better understood, and other objects, details, features and advantages thereof will become more apparent from the following description of several particular embodiments of the invention, given solely by way of illustration and not limitation, with reference to the accompanying drawings. [Fig.1] The [Fig.1] is a schematic representation of a work machine in the form of a telescopic handler according to one embodiment. [Fig.2] Fig.2 is a schematic illustration of the power supply system of a work machine, of the type shown in Fig.1. [Fig.3] Fig.3 represents a flowchart of the step of determining an operating mode of the fuel cell control process according to an embodiment. [Fig.4] The [Fig.4] is a diagram representing the setpoint value of the fuel cell as a function of the operating mode on the x-axis and the state of charge of the storage unit on the y-axis, for a charging phase of the storage unit according to an embodiment. [Fig.5] The [Fig.5] is a diagram representing the setpoint value of the fuel cell as a function of the operating mode on the x-axis and the state of charge of the storage unit on the y-axis, for a discharge phase of the storage unit according to an embodiment. Description of the implementation methods With reference to [Fig. 1], a work machine 1 is described. The work machine 1 has a movable chassis 2. To this end, the work machine 1 has wheels 3 or tracks and an electrical power supply system, not shown. The electrical power supply system includes an electric motor 11 for moving the work machine 1 and a transmission device that couples said electric motor 11 to the wheels 3 or tracks, thus enabling the work machine 1 to move. The work machine 1 has two axles, each mounted on the chassis 2 and each equipped with two wheels 3. The work machine 1 also includes a driver's cab 4 which is supported by the chassis 2. The driver's cab 4 is equipped with a driver's station including a seat where the driver can operate the forklift. The driver's station also includes control equipment for the work machine 1, such as a steering wheel, an accelerator pedal, and a brake pedal. The driver's station is also equipped with one or of several actuation elements which allow the movement of a load handling device to be controlled, for example, including a lifting arm 5. The work machine 1 also includes one or more retractable stabilizers 9 which are attached to the chassis 2. The stabilizers 9 can therefore move from a retracted position to an operating position in which the stabilizers 9 are in contact with the ground and at a distance from the wheels 3 and allow to increase the stability of the work machine 1. The work machine 1 may include, for example, two stabilizers 9 at the front on either side of the machine 1 or four stabilizers 9 at each of the wheels 3. In one embodiment, the lifting arm 5 is telescopic, meaning its length is variable. To achieve this, the lifting arm 5 comprises at least two parts, one of which slides inside the other, and a telescoping cylinder (not shown) with a first and second end attached to the first and second parts of the lifting arm 5, respectively. In this case, the work machine 1 can be, in particular, a telescopic handler. In another embodiment, the lifting arm 5 is a fixed-length arm. The working machine 1 also includes a lifting cylinder 6 which has a first end which is mounted articulated on the frame 2 of the working machine 1 and a second end which is mounted articulated on the lifting arm 5. Furthermore, the lifting arm 5 is also equipped with a tool 7, such as a bucket or fork, which is designed to receive a load. The tool 7 is hinged to the distal end of the lifting arm 5. The tool 7 is pivotally mounted relative to the lifting arm 5 by means of a tilting cylinder 8. In relation to [Fig.2], the different elements of the electrical power supply system of the working machine 1 are described below. The working machine 1 includes an electrical energy storage unit 10. The electrical energy storage unit 10 includes, for example, one or more batteries, for example, of the lead-acid or lithium-ion type. The electrical energy storage unit 10 is electrically connected to at least one electric motor 11 in order to supply it with energy. In the embodiment shown, the electrical energy storage unit 10 powers the electric motor 11 for moving the work machine 1 and a drive device 12 of the handling device comprising the lifting arm 5 and the tool 7, the drive device 12 also comprising an electric motor. The electric motor 11 is intended to propel the work machine 1. To this end, the electric motor 11 is coupled by a transmission device 21 to one axle 22 of the work machine 1 or to both axles 22. The transmission device 21 may be a mechanical device or a hy- draulique. The drive unit 12 of the load handling device may include an electric motor and electric actuators. The drive unit 12 may also be electro-hydraulic and include a pump driven by an electric motor, one or more hydraulic actuators, such as the cylinder 6 for raising the lifting arm 5, hydraulic distributors, etc. The work machine 1 includes at least one control element 13, such as an accelerator pedal, which is configured to deliver actuation requests for the electric motor 11 to a control unit 14. The work machine 1 also includes at least one control element 9, such as a three-position forward / neutral / reverse selector, which is configured to deliver requests to the electric motor 11 to move into forward, reverse, or neutral. When the control element 9 is not actuated, it is in a neutral center position, and when it is switched by a user, the control element 9 moves to a forward position to deliver a request to move into forward, and to a reverse position to deliver a request to move into reverse.The work machine 1 also includes at least one control element 15 of the load handling device, for example of the joystick type, which is configured to deliver actuation requests of the load handling device to the control unit 14. Furthermore, the working machine 1 includes a state of charge evaluation device 16 which is associated with the electrical energy storage unit 10 and which is configured to determine a value of the state of charge of the electrical energy storage unit 10 and transmit it to the control unit 14. The state of charge is a relative measure of the amount of stored energy corresponding to the ratio between the charge of the electrical energy storage unit 10 at a certain time and its total capacity, at the origin. According to one embodiment, the charge state evaluation device 16 includes a voltage sensor which delivers a measurement of the open-circuit voltage across the terminals of the electrical energy storage unit 10. Since the voltage across the terminals of the electrical energy storage unit 10 varies according to its charge level, such a measurement of the voltage across the terminals of the electrical energy storage unit 10 makes it possible to estimate its charge state. According to another embodiment, the state of charge assessment device 16 includes a coulomb counter which measures the current during the charging or discharging of the energy storage unit and integrates it, which makes it possible to determine the quantity of charges injected or withdrawn from the electrical energy storage unit 10 and thus to quantify its state of charge. In a manner known per se, the control unit 14 is configured to control in particular the electric motor 11 and the drive device 12 of the load handling device according to the actuation requests of the electric motor 11 and the load handling device respectively delivered by the control elements 9 and 13 and the control element 15. The power supply system includes a tank 17 for storing hydrogen and a fuel cell 18. Tank 17 is, for example, suitable for storing hydrogen in gaseous form at a maximum pressure between 300 and 700 bar, for example, around 350 bar. In another embodiment, tank 17 is suitable for storing hydrogen in solid form as metal hydrides. In yet another embodiment, the tank can also be adapted for storing hydrogen in liquid form. The tank 17 is connected to the fuel cell 18 by a circuit 19, which is equipped with a pressure regulator (not shown) to reduce the hydrogen pressure. The fuel cell 18 is also equipped with an air compressor to compress the combustion air entering the cells of the fuel cell 18. The fuel cell may also include a humidifying device to humidify the hydrogen and the air entering the fuel cell 18. As is known in itself, the fuel cell 18 is the site of an oxidation-reduction reaction which transforms hydrogen from reservoir 17 and oxygen from the air supplied by the compressor into electricity, water and heat. The working machine | also includes a cooling device, not shown, for cooling the fuel cell 17 and a water collection device, not shown, for collecting the water rejected by the fuel cell 18. The working machine 1 also includes power electronic equipment 20 which includes in particular a DC / DC voltage converter which is connected, on one side, to the fuel cell 18 and on the other side to the electrical energy storage device, here batteries 10. The DC / DC voltage converter allows the voltage level delivered by the fuel cell 18 to be converted to the voltage level required by the batteries 18. The control unit 14 is also configured to control the batteries 10 according to the power required by the electric motor 11 and the drive device 12, and to control the fuel cell 18 according to a control method detailed in more detail below with reference to Figures 3 to 5. In the working machine 1 as described, the fuel cell 18 allows to increase the autonomy of the storage unit 10 by supplying it with electrical energy according to the setpoint applied to the fuel cell 18. The inventors noted that it was preferable to avoid the state of charge of the storage unit 10 reaching its maximum value of 100% so as not to damage the storage unit 10, and to avoid the state of charge of the storage unit 10 reaching its minimum value so as not to cause the working machine 1 to stop when there was potentially fuel remaining in the tank 17. Furthermore, the inventors observed that it was possible to identify distinct operating modes of a work machine 1 by means of different variables. In these operating modes, the work machine 1 demands different power levels from the electric motor 11 and the drive device 12, and therefore places greater or less stress on the storage unit 10. That is why the inventors proposed a method for controlling a fuel cell as described below. The control process for fuel cell 18 thus comprises the following steps: - determining an operating mode from a list of operating modes based on different variables, - determining the state of charge of the storage unit 10, - the control of the fuel cell with a predetermined setpoint based on the state of charge of the energy storage unit and the operating mode of the working machine thus determined. Figure [Fig.3] represents a flowchart of the step of determining an operating mode of the fuel cell control process according to an implementation method. In the embodiment shown, a list of operating modes has been established: - an M1 charging mode, - an M2 slow-motion mode, - a handling mode on the M3 stabilizer, - an M4 handling mode, - an M5 charging mode, - an M6 road mode. In order to determine which operating mode the working machine 1 is in, the following list of variables was used, as shown in [Fig.3]: - a "motor speed" variable representing the speed of the electric motor of the drive device 12, the "motor speed" variable V1 having a value which is compared to a motor speed threshold SI; - a "control activity" variable V1 representing the activity of the control unit 9 and / or the control unit 15, the "control activity" variable V1 being able to take a first value N1 when the control unit 9 and the control unit 15 are in a neutral position and being able to take a second value N2 when the control unit 9 or the control unit 15 is in an active position, - a variable "driver presence" V2 representing the presence of a person on a driver's seat of the work machine 1, the variable "driver presence" V2 being able to take a first value NI when a person is present on a seat of the machine and a second value N2 when no person is present on the seat, - a "machine speed" variable V3 representing the speed of movement of the working machine 1, the "machine speed" variable V3 having a value which is compared to a machine speed threshold S2; - a variable "loading mode activity" V4 representing the activity of the load handling device, the variable "loading mode activity" being able to take a first value N1 in response to the detection of a hydraulic flow setpoint of a tool tilt cylinder 7 included in a predetermined range for a duration greater than a predetermined duration threshold and / or to the detection of an arm angle included in a predetermined range, and to take a second value N2 otherwise; - a "stabilizer" variable V5 representing the position of one or more stabilizers, the "stabilizer" variable V5 being able to take a first value N1 when at least one stabilizer is in an operating position and being able to take a second value N2 when no stabilizer is in the operating position: - a variable "recharge" V6 representing the state of a button to activate a recharge mode, the variable "recharge" V6 being able to take a first value NI when the activation button of the recharge mode is in the active state and a second value N2 when the activation button of the recharge mode is in the inactive state. However, in other embodiments, this list may include more or fewer operating modes depending on the identified need. Similarly, other variables could be used to determine the different operating modes. Furthermore, the first value N1 of variables V1, V2, V4, V5, and V6 may be the same for each of these variables (for example, equal to 1 or "Yes") or may be different. Likewise, the second value N2 of variables V1, V2, V4, V5, and V6 may be the same for each of these variables (for example, equal to 1 or "Yes"). to O or to "No") or be different. The determination of the different modes of operation according to the implementation method represented in [Fig.3] will now be described. Regarding the M1 charging operating mode, this mode is determined by means of the "driver presence" variable V2, the "control activity" variable V1, and the "charging" variable V6. Indeed, firstly, the control unit 14 receives a value of the variable "control activity" V1, a value of the variable "driver presence" V2 and a value of the variable "recharge" V6. Then, the control unit 14 determines that the operating mode is the recharge mode M1 when the value of the variable "driver presence" V2 is equal to the first value NI, the value of the variable "recharge" V6 is equal to the first value NI, and the value of the variable "control activity" V1 is equal to the first value NI. Regarding the M2 idle operating mode, this mode is determined in two different ways. According to the first method, this M2 mode is determined by means of the variable "driver presence" V2 and the variable "control activity" V1. Indeed, firstly, the control unit 14 receives a value of the variable "control activity" V1 and a value of the variable "driver presence" V2. Then, the control unit 14 determines that the operating mode is the idle mode M2 ​​when the value of the variable "driver presence" V2 is equal to the second value N2, and the value of the variable "control activity" V1 is equal to the first value NI. According to the second method, this M2 mode is determined by means of the variable "recharge" V6 and the variable "command activity" V1. Indeed, firstly, the control unit 14 receives a value from the variable "recharge" V6 and a value from the variable "control activity" V1. Then, the control unit 14 determines that the operating mode is the idle mode M2 ​​when the value of the variable "recharge" V6 is equal to the second value N2, and the value of the variable "control activity" V1 is equal to the first value NI. Regarding the M6 ​​route operating mode, this mode is determined by means of the "control activity" variable V1, and the "machine speed" variable V3. First, the control unit 14 receives a value for the "control activity" variable V1 and a value for the "machine speed" variable V3. Then, the control unit 14 compares the value of the "machine speed" variable V3 to the machine speed threshold S2. Finally, the control unit 14 determines that the operating mode is route mode M6 when the value of the "control activity" variable V1 is equal to the second value N2 and the value of the "speed" variable machine » V3 is greater than or equal to the machine speed threshold S2. Regarding the M5 loading operating mode, this mode is determined by means of the variable "control activity" V1, the variable "machine speed" V3, and the variable "loading mode activity" V4. First, the control unit 14 receives a value for the "control activity" variable V1, a value for the "machine speed" variable V3, and a value for the "loading mode activity" variable V4. Then, the control unit 14 compares the value of the "machine speed" variable V3 to the machine speed threshold S2. Finally, the control unit 14 determines that the operating mode is the MS loading mode when the value of the "control activity" variable V1 is equal to the second value N2, the value of the "machine speed" variable V3 is less than the machine speed threshold S2, and the value of the "loading mode activity" variable V4 is equal to the first value NI. Regarding the handling operating mode M4, this mode is determined by means of the variable "control activity" V1, the variable "machine speed" V3, the variable "loading mode activity" V4 and the variable "stabilizer" V5. First, the control unit 14 receives a value for the "control activity" variable V1, a value for the "machine speed" variable V3, a value for the "loading mode activity" variable V4, and a value for the "stabilizer" variable V5. Then, the control unit 14 compares the value of the "machine speed" variable V3 to the machine speed threshold S2. Finally, the control unit 14 determines that the operating mode is handling mode M4 when the value of the "control activity" variable V1 is equal to the second value N2, the value of the "machine speed" variable V3 is less than the machine speed threshold S2, the value of the "loading mode activity" variable V4 is equal to the second value N2, and the value of the "stabilizer" variable V5 is equal to the second value N2. Regarding the handling mode on stabilizer M5, this mode is determined by means of the variable "control activity" V1, the variable "machine speed" V3, the variable "loading mode activity" V4 and the variable "stabilizer" V5. First, the control unit 14 receives a value for the "control activity" variable V1, a value for the "machine speed" variable V3, a value for the "loading mode activity" variable V4, and a value for the "stabilizer" variable V5. Then, the control unit 14 compares the value of the "machine speed" variable V3 to the machine speed threshold S2. Finally, the control unit 14 determines that the operating mode is handling mode M4 when the value of the "control activity" variable V1 is equal to the second value N2, the value of the variable If the machine speed V3 is lower than the machine speed threshold S2, the value of the load mode activity variable V4 is equal to the second value N2, and the value of the stabilizer variable VS is equal to the second value N2. Regarding the control activity variable V1, in another implementation, the control activity variable V1 can be used in the operating mode determination step in combination with another variable, namely a motor speed variable. The motor speed variable represents the speed of the electric motor of the drive device 12 that actuates the load handling device. The motor speed variable V1 thus has a value that is compared to a motor speed threshold SI.Thus, in this alternative embodiment, when the "control activity" variable is equal to the first value NI and the value of the "motor speed" variable V1 is less than the motor speed threshold S1, then the control unit 14 determines that it is either operating mode MI or operating mode M2. Furthermore, when the "control activity" variable is equal to the second value N2 or the value of the "motor speed" variable V1 is greater than or equal to the motor speed threshold S1, then the control unit 14 determines that it is one of the operating modes M3 to M6. Regarding the "loading mode activity" variable V4, in another embodiment, the "loading mode activity" variable V4 can take the values ​​NI and N2 depending on another parameter.Indeed, in this case, the variable "loading mode activity" V4 represents the identification of tool 7 and is capable of taking a first value N1 in response to the detection by a tool authentication device that tool 7 is of the bucket type, and of taking a second value N2 in response to the detection by a tool authentication device that tool 7 is of the fork type. The authentication device can be an RFID transceiver, tool 7 being equipped with an RFID chip, an optical sensor, or any other type of suitable authentication device. When the operating mode is determined, the control unit 14 will then determine the state of charge of the storage unit 10 and advantageously in which phase the storage unit 10 is located. To do this, the control unit 14 receives the state of charge at time t and the state of charge at time t+dt from the storage unit 10 using the state of charge evaluation device 16, where dt is a predetermined time interval. The control unit 14 thus compares the state of charge at time t with the state of charge at time t+dt. Then, the control unit 14 determines that when the state of charge at time t+dt is lower than the state of charge at time t, the storage unit 10 is in the discharge phase (SOC-). And, the control unit 14 determines that when the state of charge at time t+dt is higher than the state of charge at time t, the storage unit 10 is SOC+ charging phase. Once the operating mode, the state of charge at time t and advantageously the phase of the storage unit 10 have been determined, the control process moves on to the control stage of the fuel cell 18. Figures 4 and 5 illustrate for one embodiment of the diagrams representing the setpoint value of the fuel cell 18 to be applied to the fuel cell 18 as a function of the operating mode on the abscissa (horizontal axis) and on the ordinate (vertical axis) of the state of charge of the storage unit 10, [Fig.4] concerning the discharge phase and [Fig.5] the charging phase of the storage unit 10. Thus, the control unit 14, when the operating mode of the working machine 1 and the mode of the storage unit 10 are known, will compare the state of charge at time t with predetermined state of charge thresholds dependent on the operating mode of the working machine 1 and the mode of the storage unit 10. In the embodiment shown in Figures 4 and 5, six state-of-charge thresholds LI to L6 are represented, ranging from 0 to 100% of the maximum state-of-charge of the storage unit 10, and exhibit decreasing values, namely L1>L2>L3>L4>L5>L6. In these diagrams, solid lines represent changes in setpoint values ​​when the load state exceeds a threshold L1-L6 or when the operating mode is modified. Dashed lines illustrate the value of each threshold for all operating modes. As shown in Figures 4 and 5, it is advantageous to incorporate hysteresis between the charging phase (SOC+) and the discharging phase (SOC-) of the storage unit 10 for each operating mode. Indeed, the storage unit 10 can switch from charging to discharging mode and vice versa very rapidly as soon as the setpoint of the fuel cell 18 is modified. Thus, crossing a state-of-charge threshold that modifies the setpoint value could trigger a switch from charging to discharging mode and vice versa. Therefore, for the same operating mode, the state-of-charge thresholds that modify the fuel cell setpoint value are different when the storage unit 10 is in the charging phase (SOC+) and when it is in the discharging phase (SOC-). In the embodiment shown, the state of charge threshold of a given operating mode for switching from a first setpoint value to a second setpoint value during the discharge phase of the storage unit 10 is lower than the state of charge threshold of said operating mode for switching from the first setpoint value to the second setpoint value during the recharge phase of the storage unit. 10. In the embodiment shown, only the MI operating mode does not exhibit hysteresis. In other words, the charge state threshold is the same during the charging and discharging phases. As shown in Figures 4 and 5, the embodiment provides for the use of four different setpoint values, namely: - a "zero" setpoint value C1 at which the fuel cell is stopped, - a "slowed down" setpoint value C2 corresponding to a power delivered by the fuel cell between 2 and 25% of a maximum power of the fuel cell; - an "average" setpoint value C3 corresponding to a power delivered by the fuel cell between 25 and 85% of the maximum power of the fuel cell; - a "maximum" setpoint value C4 corresponding to a power delivered by the fuel cell greater than 85% of the maximum power of the fuel cell. Advantageously, the "average" setpoint value C3 is dynamic, meaning it is modified during the lifetime of the work machine 1 by a learning method, i.e., based on the past use of the work machine 1. Specifically, the "average" setpoint value C3 is initialized to a predetermined initial setpoint value, which could, for example, correspond to 50% of the maximum power of the fuel cell 18. Then, an average power output is calculated during one or more operating cycles of the work machine 1. The "average" setpoint value C3 is then modified according to this calculated average power. A cycle can be defined, for example, by identifying a start-up and a shutdown of the work machine 1. The example of how figures 4 and 5 are implemented will be described in more detail later. Figure 4 relates more specifically to the SOC+ recharge phase of storage unit 10. In operating mode M1, the fuel cell 18 is intended to be controlled with: - a "zero" setpoint value C1 when the state of charge is between LI and 100%, and - an "average" setpoint value C3 when the state of charge is between 0% and LI. In operating mode M2, the fuel cell 18 is intended to be controlled with: - a "zero" setpoint value C1 when the state of charge is between L2 and 100%, - a "slowed down" setpoint value C2 when the state of charge is between L3 and L2, - an "average" setpoint value C3 when the state of charge is between L5 and L3, and - a "maximum" setpoint value C4 when the state of charge is between 0% and L5. In operating mode M3, the fuel cell 18 is intended to be controlled with: - a "zero" setpoint value C1 when the state of charge is between L2 and 100%, - a "slowed down" setpoint value C2 when the state of charge is between L3 and L2, - an "average" setpoint value C3 when the state of charge is between LS and L3, and - a "maximum" setpoint value C4 when the state of charge is between 0% and L5. In operating mode M4, the fuel cell 18 is intended to be controlled with: - a "zero" setpoint value C1 when the state of charge is between L2 and 100%, - an "average" setpoint value C3 when the state of charge is between L5 and L2, and - a "maximum" setpoint value C4 when the state of charge is between 0% and L5. In operating mode M5, the fuel cell 18 is intended to be controlled with: - a "zero" setpoint value C1 when the state of charge is between L2 and 100%, - an "average" setpoint value C3 when the state of charge is between L4 and L2, and - a "maximum" setpoint value C4 when the state of charge is between 0% and LA. In operating mode M6, the fuel cell 18 is intended to be controlled with: - a "zero" setpoint value C1 when the state of charge is between LI and 100%, and - a "maximum" setpoint value C4 when the state of charge is between 0% and LI. Figure 5 relates more specifically to the SOC- discharge phase of storage unit 10. In operating mode M1, the fuel cell 18 is intended to be controlled with: - a "zero" setpoint value C1 when the state of charge is between LI] and 100%, and - an "average" setpoint value C3 when the state of charge is between 0% and LI. In operating mode M2, the fuel cell 18 is intended to be controlled with: - a "zero" setpoint value C1 when the state of charge is between LA and 100%, - an "average" setpoint value C3 when the state of charge is between L6 and LA, and - a "maximum" setpoint value C4 when the state of charge is between 0% and L6. In operating mode M3, the fuel cell 18 is intended to be controlled with: - a "zero" setpoint value C1 when the state of charge is between LA and 100%, - an "average" setpoint value C3 when the state of charge is between L6 and LA, and - a "maximum" setpoint value C4 when the state of charge is between 0% and L6. In operating mode M4, the fuel cell 18 is intended to be controlled with: - a "zero" setpoint value C1 when the state of charge is between L3 and 100%, - an "average" setpoint value C3 when the state of charge is between L6 and L3, and - a "maximum" setpoint value C4 when the state of charge is between 0% and L6. In operating mode M5, the fuel cell 18 is intended to be controlled with: - a "zero" setpoint value C1 when the state of charge is between L3 and 100%, - an "average" setpoint value C3 when the state of charge is between L6 and L3, and - a "maximum" setpoint value C4 when the state of charge is between 0% and L6. In operating mode M6, the fuel cell 18 is intended to be controlled with: - a "zero" setpoint value C1 when the state of charge is between L2 and 100%, and - a "maximum" setpoint value C4 when the state of charge is between 0% and L2. The embodiment described above is only one example of a manifestation of the invention. Other embodiments could be used. These embodiments could thus include a different number of operating modes, different charge state thresholds and in a different number, as well as different fuel cell setpoints. Indeed, for example, intermediate setpoints could be introduced between the C1-C4 setpoints, a number less than or greater than 6 for the number of charge state thresholds, etc. The steps of the fuel cell control process 18 are repeated regularly according to a predetermined time interval in order to determine whether the operating mode of the working machine 1, the state of charge of the storage unit 10 and / or the phase of the storage unit 10 have been modified in order to determine whether the setpoint applied to the fuel cell 18 needs to be changed. The functions and steps described above can be implemented as a computer program or via hardware components (e.g., programmable gate arrays). Specifically, the functions and steps performed by the control unit can be carried out by instruction sets or computer modules implemented in a processor or controller, or by dedicated electronic components or FPGA or ASIC-type components. It is also possible to combine computer and electronic components. When it is specified that a control unit is configured to perform a given operation, this means that this element includes computer instructions and the corresponding means of execution which enable the said operation to be carried out and / or that this element includes corresponding electronic components. In particular, the steps of the process proposed above can be implemented in a non-transient computer program that includes program code instructions for executing the steps of said process. This program can then be executed by a processor of a work machine such as that proposed above. 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. Although the invention has been described in connection with several particular embodiments, it is clearly evident that it is by no means limited to them and that it includes all technical equivalents of the means described as well as their combinations if these fall within the scope of the invention. The use of the verb "comporter", "comprendre" or "include" and its conjugated forms does not exclude the presence of other elements or steps than those stated in a claim. In claims, any reference sign in parentheses should not be interpreted as a limitation of the claim.

Claims

Demands

1. Method for controlling a fuel cell (18) of a machine work (1) comprising a load handling device formed of an arm and a tool, at least one electric motor (11, 12) which is configured to move the working machine (1) and / or operate the load handling device, a storage unit (10) of energy configured to power at least one motor electric (11, 12) and a fuel cell (18) which is connected to the unit energy storage (10) and which is configured to charge the unit energy storage (10), a first control unit (9) configured to control the electric motor (11) and a second component of control (15) to control the load handling device, The process involves the following steps: - determine an operating mode (M1-M6) of the machine work (1) among at least two modes of operation depending on of at least one variable (V1-V6) chosen from: a variable "driver presence" (V2) representative of the presence of a person in a driver's seat of the work machine (1); a variable "machine speed" (V3) representing the speed of de- placement of the working machine (1); a variable "loading mode activity" (V4) representative of the activity of the load handling device; a "stabilizer" variable (V5) representing the position of one or several stabilizers; a "recharge" variable (V5) representing the state of a button activating a charging mode; a variable "order activity" representative of the activity of the first control unit and / or second control unit; And - determine a state of charge of the energy storage unit (10); and - control the fuel cell (18) with a predetermined setpoint- completed (C1-C4) depending on the state of charge of the storage unit (10) of energy and operating mode (M1-M6) of the machine work (1) thus determined.

2. Method for controlling a fuel cell (18) according to claim- indication 1, in which one of the operating modes is a mode slowdown (M2) which is determined by means of the variable "presence driver” (V2) and the variable “control activity” (V1).

3. Method for controlling a fuel cell (18) according to claim- Indication 2, in which the process comprises the following steps: - receive the variable "driver presence" (V2) and the variable "command activity" (V1), the variable "driver presence" (V2) being able to take on a first value when a person is present on a driver's seat of the work machine (1) and a second value when no one is present in the seat driver, the variable "control activity" (V1) being capable of take a first value when the first control unit (9) and the second control unit (15) were not activated by a user and being able to take a second value when the first control unit (9) or the second control unit (15) was activated by a user; - determine that the operating mode is idle mode (M2) when the variable "order activity" is equal to the first value and that the variable "driver presence" (V2) is equal to the second value.

4. Method of controlling a fuel cell (18) according to one of the re- demands | to 3, in which one of the modes of operation is a charging mode (M1) which is determined by means of the variable " driver presence” (V2), of the variable “control activity” (V1), and the variable "recharge" (V6).

5. Method for controlling a fuel cell (18) according to claim- Indication 4, in which the process comprises the following steps: - receive the variable "driver presence" (V2), the variable "activity command” (V1), and the “recharge” variable (V6), the “ "conductor presence" (V2) being able to take a first value when a person is present in a seat of the machine and a second value when no one is present in the seat”, the variable "recharge" (V6) being able to take a first value when the charging mode activation button is in the active state and a second value when the mode activation button recharge is in the inactive state, the variable "command activity" (V1) being able to take on a first value when the first organ of control (9) and the second control element (15) are in a neutral position and being able to take a second value when the first control unit (9) or the second control unit (15) is in an active position; - determine that the operating mode is charging mode (M1) when the variable "command activity" (V1) is equal to the first value, the variable "driver presence" (V2) is equal to the first value and the "recharge" value is equal to the first value.

6. Method of controlling a fuel cell (18) according to one of the re- demands | to 5, in which one of the modes of operation is a road mode (M6) which is determined by means of the variable "speed machine » (V3).

7. Method for controlling a fuel cell (18) according to claim- Indication 6, in which the process comprises the following steps: - receive the variable "machine speed" (V3), - compare the variable "machine speed" (V3) to a speed threshold predetermined machine (S2), - determine that the operating mode is road mode (M6) when the variable "machine speed" (V3) has a value su- greater than the predetermined machine speed threshold (S2).

8. Method of controlling a fuel cell (18) according to one of the re- claims 1 to 7, in which one of the modes of operation is a loading mode (M5) which is determined by means of the variable " machine speed” (V3), of the variable “control activity” (V1) and of the variable "loading mode activity" (V4).

9. Method for controlling a fuel cell (18) according to claim- Indication 8, in which the process comprises the following steps: - receive the variable "machine speed" (V3), the variable "activity of command”, and the variable “loading mode activity” (V4), the variable "loading mode activity" (V4) being capable of taking a first value in response to the detection of a hy- flow rate setpoint draulic of a tool tilt cylinder within a pre- determined for a period exceeding a pre-defined duration threshold determined and to the detection of an angle of the arm within a range predetermined and to take a second value otherwise, the variable "command activity" (V1) being capable of taking a first value when the first control unit (9) and the second control element (15) are in a neutral position and being able to take on a second value when the first organ of control (9) or the second control element (15) is in a active position; - compare the variable "machine speed" (V3) to a speed threshold predetermined machine (S2), - determine that the operating mode is charging mode when the variable "command activity" (V1) is equal to the second value, the variable "machine speed" (V3) presents a value lower than the predetermined machine speed threshold (S2), and the variable "loading mode activity" (V4) is equal to the first value.

10. Method of controlling a fuel cell (18) according to one of the re- claims 1 to 9, in which one of the modes of operation is a handling mode (M4) determined by means of the variable "speed machine” (V3), of the variable “control activity” (V1), of the variable "loading mode activity" (V4) and the variable "stabilizer" (V5).

11. Method for controlling a fuel cell (18) according to claim- Indication 10, in which the process comprises the following steps: - receive the variable "machine speed" (V3), the variable "activity of command" (V1), the variable "loading mode activity" (V4), and the variable "stabilizer" (V5); the variable "activity of the mode" loading » (V4) being able to take a first value in response upon detection of a hydraulic flow setpoint from a cylinder tool tilt (7) within a predetermined range for a period exceeding a predetermined duration threshold and the detection of an arm angle (5) within a predetermined range and to take a second value otherwise; the variable "sta- biliator” (V5) being capable of taking a first value when at minus one stabilizer (9) is in an operating position and being able to take a second value when no stabilizer (9) is not in the operating position, the variable "activity of "command" (V1) being able to take a first value when the first control unit (9) and the second control unit (15) are in a neutral position and are able to take a second value when the first control unit (9) or the second control unit (15) is in an active position; - compare the variable "machine speed" (V3) to a speed threshold predetermined machine (S2), - determine that the operating mode is the handling mode (M4) when the variable "command activity" (V1) is equal to the second value, the variable "machine speed" (V3) presents a value lower than the predetermined machine speed threshold (S2), the The variable "activity of the load handling device" is equal to the first value, and the variable "stabilizer" (V5) is equal to the second value.

12. Method of controlling a fuel cell (18) according to one of the re- demands 1 to 11, in which the stack control step to com- fuel (18) comprises the following sub-steps: - compare the determined state of charge to a threshold state of charge {L1-L6), - when the state of charge is above the state of charge threshold (L1-L6), control the fuel cell (18) with a predetermined setpoint (C1-C4) having a first setpoint value, - when the state of charge is below the state of charge threshold (L1-L6), control the fuel cell (18) with a predetermined setpoint (C1-C4) having a second setpoint value, the second value of setpoint being greater than the first setpoint value.

13. Method of controlling a fuel cell (18) according to one of the re- demands 1 to 11, in which the stage of determining the state of The process involves the following sub-steps: - determine the state of charge at a given time t; - determine the state of charge at a time t+dt, dt being an interval of predetermined time; - compare the state of charge at time t and the state of charge at time t+dt - when the state of charge at time t+dt is less than the state of charge at At time t, determine that the energy storage unit (10) is in discharge phase (SOC-); - when the state of charge at time t+dt is greater than the state of charge At time t, determine that the energy storage unit (10) is in charging phase (SOC+); in which the fuel cell control stage (18) comprising in discharge phase (SOC-) of the storage unit (10) energy, the following sub-steps: - compare the determined state of charge to a first threshold state of charge (L1-L6); - when the state of charge is greater than the first state of charge threshold, control the fuel cell (18) with a predetermined setpoint (C1-C4) having a first setpoint value, - when the state of charge is below the first state of charge threshold, control the fuel cell (18) with a predetermined setpoint having a second setpoint value, the second setpoint value being greater than the first setpoint value; and in which the fuel cell control step (18) comprising in charging phase (SOC+) of the storage unit (10) energy, the following sub-steps: - compare the determined state of charge to a second state threshold of charge (L1-L6), the first charge state threshold being different from the second charge state threshold, - when the state of charge is greater than the second state threshold of charge, control the fuel cell (18) with a prede- completed (C1-C4) having the first setpoint value, - when the state of charge is below the second state threshold of charge, control the fuel cell (18) with a prede- completed (C1-C4) having the second setpoint value.

14. Method for controlling a fuel cell (18) according to claim- indication 12 or claim 13, wherein the first and the second setpoint value corresponds to two of the values ​​of The following instructions apply: - a "zero" setpoint value (C1) for which the battery to be com- fuel (18) is stopped, - a "slowed down" setpoint value (C2) corresponding to a power delivered by the fuel cell (18) between 2 and 25% of a maximum power of the fuel cell (18); - an "average" setpoint value (C3) corresponding to a power delivered by the fuel cell (18) between 25 and 85% of the maximum power of the fuel cell (18); - a "maximum" setpoint value (C4) corresponding to a power delivered by the fuel cell (18) greater than 85% of the maximum power of the fuel cell (18).

15. Method for controlling a fuel cell (18) according to claim- indication 14, in which the "average" setpoint value (C3) is adjusted over the working life of the machine (1) according to the Next steps: - initialize the "average" setpoint value (C3) to a value of predetermined initial instruction, - calculate the average power delivered during one or more cycles activities of the working machine (1), - modify the "average" setpoint value (C3) according to the Average power calculated.

16. Control unit (14) for a work machine (1) comprising a load handling device consisting of an arm (5) and a tool (7), at least one electric motor (11) which is configured to move the work machine (1) and / or operate the device load handling, a configured energy storage unit (10) to power the electric motor (11), a com- battery fuel (18) which is connected to the energy storage unit (10) and which is configured to charge the energy storage unit (10), a first control unit {9) configured to control the motor electrical (11) and a second control element (15) configured for order the load handling device, the unit of command (14) being configured for: - determine an operating mode (M1-M6) of the machine work (1) among at least two modes of operation depending on of at least one variable chosen from: a variable "driver presence" (V2) representative of the presence of a person in a driver's seat of the work machine (1); a variable "machine speed" (V3) representing the speed of de- placement of the working machine (1); a variable "loading mode activity" (V4) representative of the activity of the load handling device; a "stabilizer" variable (V5) representing the position of one or several stabilizers; a "recharge" variable (V6) representing the state of a button activating a charging mode; a variable "order activity" (V1) representing the activity of the first control unit (9) and / or of the second control unit order (15); and - determine a state of charge of the energy storage unit (10); and - control the fuel cell (18) with a predetermined setpoint- completed (C1-C4) depending on the state of charge of the storage unit (10) of energy and operating mode (M1-M6) of the machine work thus determined.

17. | Product computer program comprising code instructions program for executing the steps of a control process according to any one of claims 1 to 15, when said program is executed by a control unit (14).

18. Work machine (1) comprising a handling device load consisting of an arm (5) and a tool (7), at least one motor electric (11) which is configured to move the working machine (1) and / or operate the load handling device, a unit of energy storage (10) configured to power the motor electric (11), a fuel cell (18) which is connected to the unit of energy storage (10) and which is configured to charge the unit of energy storage (10), a first control unit (9) configured to control the electric motor (11) and a second component of control (15) configured to control the handling device of charge, and in which the working machine (1) comprises a unit control (14) according to claim 16.