FR3092811A1 - METHOD AND SYSTEM FOR DRIVING AN ELECTRIC AXLE OF A TRAILER OR SEMI-TRAILER - Google Patents

Abstract

The invention relates to a method of controlling an electric axle (2) of a vehicle towed (1) by a towing vehicle (1c) to form a convoy, said axle (2) being associated with at least one electric motor ( 9) to provide traction assistance to the convoy during traction by the towing vehicle (1c), consisting in determining a torque setpoint (C) for the electric motor (9) using force data relating to to the tractive force exerted by the towing vehicle (1c), consisting in using sensors arranged on the convoy to provide measured data relating to said convoy, using an inertial sensor arranged on the towed vehicle (1) to provide measured or calculated data relating to the acceleration of the convoy, merge the data from the sensors present on the convoy, said merge of the data being based on the use of at least one calculation algorithm, and estimate by calculation the tractive effort. Figure for the abstract: Fig 2.

Description

METHOD AND SYSTEM FOR CONTROLLING AN ELECTRIC AXLE OF A TRAILER OR SEMI-TRAILER

The present invention relates to the general technical field of vehicles, for example road vehicles and convoys of the classic or specific type trailers and semi-trailers when it comes, for example, to car carriers.

The invention also relates to the technical field of the hybridization of vehicles, in which an axle is integrated associated with an electric, hydraulic or pneumatic motorization to ensure its drive at least intermittently.

The present invention relates more particularly to a method and a system for controlling an electric axle. The latter thus allows a trailer or semi-trailer to provide traction/braking assistance to the towing vehicle.

State of the art

It is known to equip a trailer or semi-trailer with an electric motor, which delivers a torque to an axle, in particular during acceleration phases of said vehicle.

For example, through document EP 2 394 890, a solution for assisting the piloting of two motor-wheels of a trailer is known, in which, by means of a force sensor, a force of traction between the towing vehicle and the towed vehicle. Such a solution has a number of drawbacks. Indeed, the values measured by such a sensor are often unreliable. This lack of reliability is linked in particular to persistent mechanical stresses at the level of the connection between vehicles and no longer corresponding to the real-time state of the connection of the towed and tractor vehicles and to changes in temperature during such measurement processes. The steering of the axle cannot then be precise and reliable. In addition, the cost of a force sensor is very high.

Also known through document US 7,743,859, a traction assistance solution in which sensors for determining the traction setpoint are located on the towing vehicle. Such a solution has the major drawback that it is totally dependent on the tractor vehicle.

The object of the present invention aims to overcome the drawbacks of the prior art by proposing a new method for controlling an electric axle of a trailer or a semi-trailer.

Another object of the present invention is to provide a new axle steering system for implementing the method for steering said axle.

Another object of the present invention aims to provide a new axle steering system making it possible to ensure interoperability with various types of tractor vehicles without modifying the existing interfaces.

The objects assigned to the invention are achieved with the aid of a power control method for an electric axle of a towed vehicle, of the trailer or semi-trailer type, towed by a towing vehicle to form a convoy, said electric axle being associated with at least one electric motor to provide traction assistance to the convoy during traction by the tractor vehicle, consisting in determining a torque setpoint for the electric motor by using a force datum relating to the traction force exerted by the towing vehicle on the convoy, characterized in that it comprises the steps:
- using physical parameter sensors placed on the convoy to provide measured data relating to said convoy,
- using an inertial sensor placed on the towed vehicle to provide measured data relating to the acceleration of the convoy,
- performing a fusion of the data from the sensors present on the convoy, said fusion of the data being based on the use of at least one calculation algorithm,
- estimate by calculation and from the result of the data fusion, the traction force to determine the force datum, and
- calculate in real time a torque setpoint for the electric motor to contribute to the tractive or braking forces of the convoy.

According to an example of implementation, the fusion of the data coming from the sensors comprises the use of a Kalman filter, which performs at least the fusion of the data coming from the sensors, in particular the data coming from the inertial sensor, the speed of the electric motor, the mass of the convoy and the torque setpoint transmitted to the electric motor to provide estimated values of the physical and dynamic parameters of the convoy.

According to an example implementation, the estimation of the effort datum comprises the following steps:
- (e1) from a torque setpoint supplied to the electric motor using the force applied to the wheel of the electric axle, estimate the traction force and the reference speed V _R of the convoy corresponding to values predicted or estimated relating to the towed vehicle, thus determining a dynamic state of the convoy,
- (e2) measure the acceleration and speed values of the convoy,
- (e3) readjusting the dynamic state according to the difference between the actual measured values and the predicted values and according to the Kalman gain calculated on the basis of the confidences attributed to the measured quantities,
- Repeat steps (e1), (e2) and (e3) continuously.

According to an exemplary implementation, the data comprises values measured via an EBS system (“Electronic Braking System” or “Electronic Braking System”).

According to an exemplary implementation, the mass of the convoy is estimated from the mass of the towed vehicle, measured by the EBS system, the mass of the towing vehicle being substantially constant.

According to an example of implementation, the control method consists in reducing the torque setpoint of the electric motor according to a linear law of reduction gain as a function of the radius of gyration of the towed vehicle resulting from a non-parallelism between said towed vehicle and the towing vehicle, using the estimated values of the speed of the towed vehicle in yaw and of the longitudinal speed.

According to an exemplary implementation, the steering method consists in using values corresponding to the slope of the vehicle.

According to an exemplary implementation, the piloting method consists in using an inertial sensor to measure acceleration values along a vertical axis of the towed vehicle so as to take account of vibrations resulting from irregularities in the road, which are likely to generate erroneous tensile stress values.

The objects assigned to the invention are also achieved with the aid of a control system characterized in that it comprises an electric motor associated with an electric axle and equipped with a position sensor, an inverter, a system of high voltage battery type power supply, an EBS system, at least one wheel speed sensor, a data fusion and filtration system for fusing sensor data, at least one at least one axis inertial sensor for perform a longitudinal acceleration measurement, a control system comprising a filtration system, a control logic to manage the traction chain and to provide the torque setpoint of the electric motor.

According to an exemplary embodiment, the system comprises a battery recharging system.

According to an exemplary embodiment, the inertial sensor comprises three axes performing respectively a longitudinal, transverse and vertical acceleration measurement.

According to an exemplary embodiment, the system comprises a gyroscope.

According to an exemplary embodiment, the system comprises an ABS or EBS system

According to an exemplary embodiment, the control logic integrates a fuel consumption model of the tractor vehicle, used to determine to what extent the piloting process must be triggered.

According to an exemplary embodiment, the data filtration and fusion system integrates a model of the friction of the wheel on the ground and/or a model of the friction of the air on the cabin of the convoy.

According to an exemplary embodiment, the control system equips a trailer.

According to an exemplary embodiment, the piloting system equips a semi-trailer.

The objects assigned to the invention are also achieved using a computer program product that can be loaded directly into a memory unit of a computer, a digital tool or a computer system, to drive the implementation of the steps of a control method presented above, when the instructions of said computer program product are executed on the computer, the digital tool or the computer system.

The steering method in accordance with the invention has the enormous advantage of ensuring complete independence from the tractor vehicle during its implementation. The steering method can thus be implemented when the trailer or semi-trailer is towed by an old tractor vehicle, not designed specifically for trailers or semi-trailers equipped with at least one electric axle.

The control system in accordance with the invention thus has the advantage of operating in a totally autonomous manner in the determination of the traction forces, while integrating control and command functionalities which will allow it to be integrated into standardized systems integrating exchanges of traction data between the tractor vehicle and the towed vehicle. The control system according to the invention is therefore interoperable between standard tractors and tractors equipped with a serial interface dedicated to traction systems for trailers.

The piloting method advantageously makes it possible to secure the piloting method in bends, in a reliable and economical manner.

The control system advantageously makes it possible to detect slowdowns in the convoy, in order to detect braking linked to the retarders installed on the towing vehicles which do not always generate signals on the braking components of the goods transport trailer.

The control system makes it possible to assist the towing vehicle in such a way that the user does not perceive the assistance, in particular by generating little or no vibrations or longitudinal jerks.

Brief description of figures

Other characteristics and advantages of the invention will appear on reading the detailed description which follows, description made with reference to the appended drawings, given by way of non-limiting illustrative examples, in which:

Figure 1 is an illustration of a semi-trailer comprising an electric axle control system according to the invention;

FIG. 2 is an illustration of a trailer comprising a system for controlling an electric axle according to the invention;

FIG. 3 is a perspective view of an exemplary embodiment of an electric axle controlled by means of the control method according to the invention;

FIG. 4 is a perspective view of another exemplary embodiment of an electric axle controlled by means of the control method according to the invention;

FIG. 5 is a functional flowchart of an example of implementation of the piloting method in accordance with the invention;

FIG. 6 schematically illustrates an application of the piloting method in accordance with the invention; and

FIG. 7 illustrates an advantage resulting from the implementation of the piloting method in accordance with the invention.

Detailed disclosure of the invention

In the following, a structurally and functionally identical element, represented in different figures, is assigned a single and same numerical or alphanumeric reference.

In the following, the use of the terms "disengageable" or "in a disengaged state" should be understood in the broad sense, i.e. "not ensuring transmission of movement". These terms can therefore also relate to dog clutch devices and not only to clutch devices.

FIG. 1 illustrates a towed vehicle 1 of the semi-trailer type shown partially in transparency to visualize an electric axle 2 associated with an electric motor and a conventional axle 3. A power supply system 4 is integrated in the lower part of said semi -trailer. The electric axle 2 equipped with a central mechanism according to the invention can alternatively also equip a trailer, or any other road vehicle.

Indeed, the towed vehicle 1 can be any type of road vehicle, but preferably a trailer or a semi-trailer, for example a trailer or a semi-trailer of a car transporter.

In the following, reference will be made more particularly and in a non-limiting manner to a trailer 1.

Figure 2 is an illustration of a trailer 1 comprising an electric axle 2 steering system. The trailer 1 also comprises a front axle 3, non-motorized and secured to a drawbar 1a. The latter is connected at a coupling pin 1b to a tractor vehicle 1c.

FIG. 3 shows an external view and in perspective of an embodiment of the electric axle 2, comprising a central casing 5 integrating a rotational movement transmission 5a. The transmission of rotational movement 5a can be of the mechanical type, comprising for example sprockets, a belt and/or a chain. The transmission of rotational movement 5a can also be of the hydraulic, pneumatic type or of any other known type.

The electric axle 2 also comprises two hollow axle ends 6 connected to the casing 5 with one of their ends, for example by bolting or by welding. The other end of the axle ends 6 has a hub 7 on which is mounted a wheel 8. The latter can be made as a single or double wheel. The axle ends 6 can be made in one piece with the casing 5.

The electric axle 2 also comprises an electric motor 9, mounted on the casing 5 and having a rotary shaft 9a parallel to the axis of the axle 2. The electric motor 9 is capable of driving the wheels 8 and/or a or more auxiliary equipment 10. An auxiliary equipment 10 is for example a hydraulic or pneumatic system. A rotary member advantageously constitutes the rotation shaft of the auxiliary equipment 10.

According to one embodiment, the rotary member constitutes a power take-off accessible from outside the casing 5 and capable of being coupled to the auxiliary equipment 10.

By way of example, the hydraulic system is a hydraulic pump 10′ mounted on the casing 5, for example in the extension of the electric motor 9. Each auxiliary equipment 10 preferably comprises at least one rotary member, for example provided to be driven at rotation by the electric motor 9 or by the rotation of the wheels 8.

Advantageously, the electric motor 9 can operate reversibly to recharge the energy supply system 4, for example during the braking phases of the convoy.

The electric axle 2 comprises at least one wheel 8 mounted on each axle end 6. Advantageously, it also comprises a braking system, a suspension system 11 and a damping system 12. These systems are known as such and are therefore not further described.

The energy supply system 4 is rechargeable and embedded in the trailer 1. It is provided to supply the electric motor 9 with electrical energy. The energy supply system 4 advantageously comprises at least one electric energy reserve of the electric battery or supercapacitor type.

According to one embodiment, the axle ends 6 fixed to the casing 5 each comprise a shaft 6a establishing the kinematic connection between the hub 7 and the transmission of rotational movement 5a of the casing 5.

The casing 5 is advantageously made in two parts, for example to allow the assembly of the transmission elements.

The electric motor 9 is connected to the rotational movement transmission 5a via an at least partially disengageable kinematic connection, comprising for example a disengaging or dog clutch device. It is in fact important to have a clutch or dog clutch device provided between the electric motor 9 and a differential so as to drive the load or auxiliary equipment 10, when stationary, without driving the wheels 8. In fact, said disengagement or dog clutch device can be provided in several places.

The at least partially disengageable kinematic link is provided to allow activation and deactivation of the kinematic link between the electric motor 9 and the rotational movement transmission 19 and/or between said electric motor 9 and the rotary member of the auxiliary equipment 10.

It makes it possible to couple or not on the one hand the rotary shaft of the motor 9 to a shaft connected to a wheel 8 and on the other hand the rotary shaft shaft of the electric motor 9 to the rotary member of the auxiliary equipment 10.

According to an exemplary embodiment, the rotational movement transmission 5a can have several reduction ratios, of the gearbox type.

The clutch or dog clutch device, as well as any synchronism device, are not necessarily necessary if you change gear when stationary or without a load.

According to an exemplary embodiment, the rotational movement transmission 5a incorporates a transmission and a differential.

Advantageously, the rotational movement transmission 5a integrates a reduction between the rotary shaft 9a of the electric motor 9 and the shaft 6a of the axle ends 6. It can for example be made in one, two or three stages to adapt the speed of the electric motor 9 to the speed of the wheels 8 depending on the specific characteristics of the electric motor 9. It is also possible to have a reduction between the shaft of the electric motor 9 and the rotary member of the auxiliary equipment 10.

According to an exemplary embodiment of the axle 2, each hub 7 can also incorporate a reducer, this to allow greater amplification.

Figure 4 is a perspective view of another embodiment of the electric axle 2, capable of being controlled by means of the control method according to the invention. In this exemplary embodiment, the electric motor 9 is kinematically connected to the rotary motion transmission 5a via a motor shaft 9a. the motor 9 is therefore offset from the axle 2. The piloting method in accordance with the invention can be envisaged on architectures of this type, for example in retrofitting for convoys integrating a plurality of motors. By way of example, we can cite Australian “Power-trains”, that is to say convoys made up of a tractor vehicle and a multitude of trailers which could all be equipped with an electric axle.

FIG. 5 is a functional flowchart of an example of implementation of the piloting method in accordance with the invention.

The tractor vehicle 1c thus receives information I0, including in particular control instructions and disturbances, coming from the road/journey and/or from a driver. The towing vehicle 1c then transmits coupling forces and braking instructions I1 to the trailer 1 comprising the electric axle 2.

The trailer 1 is equipped with a control system 20 making it possible to implement a control strategy, in this case a control of the electric axle 2. The control system 20 comprises for example a calculation unit 30 and a control logic 40.

The calculation unit 30 makes it possible to transmit information I5 and/or measurements to the control logic 40.

The primary information I5 includes for example:
- the speed from the EBS system,
- the braking instructions from the braking system of the tractor 1c, modulated by the EBS system,
- the mass of trailer 1, obtained either by measuring the pressure in the suspension bellows or by reading information from the EBS system if the latter has this type of measurement,
- the condition of the various equipment of the train's traction chain, namely:
(a) at the level of an inverter and of the electric motor 9, the temperature, the power available, the operating states,
(b) at the level of the energy supply system 4 or battery, the state of charge, the power available for charging or discharging, the operating states,
(c) at the charger level, the state of the battery charger to determine whether the user wishes to recharge the battery,
- the longitudinal acceleration measurement from an inertial sensor
- measurements of acceleration or angular rotation speeds provided by an inertial sensor, along the axes other than the longitudinal acceleration.

The calculation unit 30 makes it possible, from primary information I2, to calculate secondary information, in particular the reference speed V _R of the trailer 1 and the slope P to which said trailer 1 is subjected.

The reference speed V _R is calculated from the EBS speed and the speed of the electric motor. Knowing the variation of maximum acceleration of the convoy in traction and in braking, it is possible to determine a speed approaching the real speed of the convoy, particularly in situations of low grip where the wheels risk slipping relative to the ground. The literature is extremely important on this subject. This reference speed V _R is important so that it correlates with the acceleration values seen by the accelerometer.

The estimated value of the slope P is obtained in the following way. The slope P to which the convoy and the trailer 1 is subjected is calculated by combining the reference speed V _R and the instantaneous acceleration measured by the inertial sensor: a _{accelerometer} (t).

The variations of the reference speed V _R are limited in order to reject potential adhesion losses, then the result is derived to obtain the acceleration of the convoy relative to the ground: a _REF (t).

If the wheel-ground contact is considered to show little or no slip, we can note:
a _acceleration (t) = a _REF (t) + g * sin(θ)
where θ is the angle of the pitch slope to which the convoy is subjected, g being the acceleration due to gravity. It is therefore possible to estimate the angle θ by subtracting the acceleration seen by the reference speed from the longitudinal acceleration seen by the accelerometer.

The estimated slope information is low frequency to detect the phases during which the trailer is uphill or downhill. Filtering is performed to filter the consecutive slope values by limiting the derivative of this signal. This makes it possible to have a stable signal which feeds the control logic 40.

The control logic 40 makes it possible to manage the traction chain of the convoy and supplies the torque setpoint C to the electric motor 9 according to the states of the various components.

The control system 20 also comprises a data filtration and fusion system 50, also called an estimator, which makes it possible to estimate the tractive effort of the towing vehicle 1c on the convoy, as a function of real values measured, for example by sensors, and this to adjust the torque setpoint C to the electric motor 9 to provide assistance which is correlated with the acceleration desired by the driver. This estimator makes it possible to determine an image value of the tractive effort of the towing vehicle 1c on the convoy, while subtracting the value of effort supplied by the electric motor 9.

The data filtration and fusion system 50 advantageously comprises an extended Kalman filter. The latter is known as such and will therefore not be described in more detail. Other formalisms of estimators, such as deterministic Luenberger observers or others, would be quite possible.

The control system is designed to transmit the information I2 coming from the trailer 1 and the electric axle 2 to the calculation unit 30. This information I2 includes in particular:
- measurements relating to the acceleration and the state of the sensors, in particular the longitudinal, lateral and vertical acceleration and measurements from a three-axis gyroscope,
- information from the electric motor 9, in particular the speed of rotation of the motor 9, the instantaneous motor torque, the state of the electric motor 9, namely the temperature, the power delivered,
- information from the EBS system, in particular the mass of the convoy or the mass on axles 2 and 3, brake control pressure, braking status, RSS (stability assistance system) or ABS triggers linked to the operation of the EBS system, the differential speed of the axle(s) 2, 3,
- information coming from the energy source 4 or battery, in particular the operating state, the state of charge, the maximum current, the maximum voltage.

Information I3 and I5, relating in particular to the reference speed V _R and to the slope P are transmitted respectively to the data filtration and fusion system 50 and to the control logic 40.

The information I3 includes in particular the acceleration measurement value, the mass of the trailer or the mass of the convoy obtained by interpolation, the instantaneous torque applied by the electric motor 9 on the axle 2, the reference speed V _R or the speed provided by the EBS system and the rotational speed of the electric motor 9.

The information I5 includes in particular the information I2 to which is added the reference speed V _R and the slope P.

The data filtration and fusion system 50 then transmits information I4, namely the estimated and adjusted tractive effort, to the control logic 40. The latter then generates information I6 corresponding to a torque setpoint C that it transmits to the electric motor 9 of axle 2.

FIG. 6 schematically illustrates an application of the piloting method in accordance with the invention. The piloting method actually makes it possible to implement securing the convoy in bends.

In bends, the estimate of the forces presented above must not result in a situation that risks compromising the stability of the convoy. The latter is linked to the non-parallelism between the towing vehicle 1c and the trailer 1 in bends, when said trailer 1 is connected to the towing vehicle 1c via a drawbar 1a and/or a coupling pin 1b.

Thus, to avoid overturning or jackknifing phenomena, the speed of rotation of the trailer 1 in yaw and the cant angle are estimated and enter into the regulation of the traction as additional parameters to reduce the assistance in situations that could compromise the stability of the convoy.

The aforementioned speeds of rotation can be obtained for example by the EBS system using the differential speed V₂ -V₁at the wheels 8 and by a gyroscope based on technologies of the MEMS or fiberglass type, to obtain the instantaneous speed of rotation ω of the trailer 1.

The lateral acceleration A _lat is measured by the inertial sensor along the lateral axis of trailer 1.

From the relationships given below, it is possible to calculate the radius of gyration R of trailer 1 and the cant angle φ of trailer 1, namely:
R = (L * V _av ) / (V ₂ - V ₁ ) = V _av /ω
A _lat = V _av * R + g * sinφ = R * ω ² + g * sinφ
V _avg is the average speed V ₁ and V _2, g being the acceleration of gravity.

The value of the radius of gyration of the towing vehicle 1c, or a value composed of two values, for example the minimum value between the radius of gyration of the towing vehicle 1c and of the trailer 1, could be used as input data for more than safety and precision. Since the means for determining the curvature of the road are multiple, redundancy can then be easily implemented for greater safety. For example, the EBS system can perform this calculation on the one hand and an ECU system ("Electronic Control Unit" or "Electronic Control Unit") can perform this calculation on the other hand to allow traction to be interrupted. in situations that could compromise the stability of the convoy.

Depending on the radius of gyration R, and the geometric parameters of the trailer 1 and of the tractor vehicle 1c, namely the respective distance A ₁ , A ₂ between the axles and the coupling pin 1b, the angle γ between the trailer 1 and the tractor vehicle 1c, assuming that there is no slippage.

Knowing this angle γ and the maximum tolerance of lateral force F _{max lat} undergone by the tractor vehicle 1c, it is possible to calculate the absolute value of the maximum engine torque ABS(C _mot ) not to be exceeded so that said tractor vehicle 1c does not slip .

We thus obtain:
ABS(C _mot ) / r _wheel ≤ F _{max lat} * cos(γ)
with γ = atan(A ₁ / R) + atan(A ₂ / R)
A ₁ and A ₂ being respectively the distance between a rear axle 1d of the tractor vehicle 1c and the coupling pin 1b, and the distance between the midpoint M along the longitudinal extension of the trailer 1 and the coupling pin 1b , r _wheel being the radius of wheel 8 of trailer 1.

There are different types of models published for the determination of the angle γ. As an example we can cite the link: http://www.autoturn.ch/gyration/f/train_r.html.

FIG. 7 illustrates an advantage resulting from the implementation of the piloting method in accordance with the invention.

According to an example of implementation, the control method makes it possible to reduce the torque setpoint C of the electric motor 9 according to a linear law of a reduction gain as a function of the radius of gyration of the convoy resulting from a non-parallelism between said trailer 1 and the towing vehicle 1c.

The linear reduction gain law is materialized by curve A in figure 7, which shows the percentage of the motor torque setpoint C as a function of the inverse of the radius of gyration 1/R.

Setpoint C is only reduced from a predetermined value R ₀ . The large radii of gyration, corresponding to values of curvature lower than 1/R ₀ , are therefore not affected by a reduction in said setpoint C.

Curve B illustrates this reduction gain controlled by a safety relay, of the on/off type, making it possible to transfer the calculation and the effects of a trigger to another control unit, for example that of the EBS system or by switches of the "limit switch" type, to achieve an additional level of safety in the operational safety reference systems, for example SIL (Safety Integrity Level), ASIL (Automotive Safety Integrity Level), PL (Performance Level).

Advantageously, the kinetic energy of the convoy can be recovered during the braking phases in order to recharge the battery. The control torque of the electric motor 9 can be controlled:
- by data relating to the braking forces detected by the data filtering and merging system 50 presented previously and also called estimator,
- by data relating to the braking system via the data transiting between the trailer 1 and the towing vehicle 1c, for example a braking pressure setpoint,
- by a combination of these two data, where
- in anticipation of the driver braking when the convoy is on a slope and not accelerating, which will necessarily lead to braking,
- when the battery is sufficiently discharged and the internal combustion engine is at an operating point with good efficiency.

A concrete example of implementation of a method in accordance with the invention is given below.

The control method in the traction phase can therefore take place in this way (all the phases of starting up the traction chain which are not of interest to those skilled in the art are deliberately ignored). According to an example of implementation of the control process:
- the convoy is first at a standstill, at zero speed and with the brakes applied. Thanks to information from the braking system: brakes applied and zero or almost zero speed, the ECU (Electronic Control Unit) tells an inverter not to supply torque C,
- the driver decides to release the brakes. Thanks to information from the braking system: brakes released and zero or almost zero speed, the ECU tells the inverter not to supply torque C,
- the driver begins to accelerate the convoy. Thanks to information from the braking system: brakes released and speed above a so-called "virtually zero" threshold speed, the ECU indicates to the inverter that it can supply torque C to the electric motor 9. The estimator takes into input the acceleration of the convoy, the speed of the convoy, the speed of the electric motor 9 and the mass of the convoy and the torque supplied by the motor which is zero at this instant. Reference may be made to information I3. It then estimates a force F1 image of the traction of the engine of the tractor vehicle 1c on the convoy. It tells the inverter to provide a couple of value C1 image of F1,
- the driver accelerates the convoy in the same way. Thanks to information from the braking system: brakes released and speed above a so-called "virtually zero" threshold speed, the ECU indicates to the inverter that it can supply torque C to the electric motor 9. The estimator determines on the base of the information I3 the same force F1 image of the traction of the engine of the tractor vehicle 1c on the convoy despite the fact that the electric motor 9 has added a contribution to the overall acceleration of the convoy. It tells the inverter to provide a pair of values C1 image of F1. If the driver keeps the same acceleration setpoint, C1 and F1 are stable. If the driver finds that the acceleration he obtains is too high, he will reduce his instruction until he is satisfied, in the same way as he would on a classic convoy. This state will also lead to the determination of stable torque C2 and force F2 values,
- the driver decides to maintain his speed without accelerating. Thanks to information from the braking system: brakes released and speed higher than a so-called “near-zero” speed, the ECU indicates to the inverter that it can supply torque to the electric motor 9. The estimator determines on the basis of the information I3 a lower effort F3 image of the traction of the engine of the tractor vehicle 1c. According to the control logic 40, it tells the inverter to provide a pair of values C3 image of F3 and modulated by a control strategy that can be modified according to the type of route to optimize energy gains. It is indeed known by those skilled in the art that heat engines have relatively good efficiency at stabilized speeds and low torque. In this case, we could decide to set the setpoint to 0,
- the driver always maintains the speed of the convoy, but the convoy is on a rise, a slope. Thanks to information from the braking system: brakes released and speed higher than a so-called "near-zero" speed, the ECU indicates to the inverter that it can supply torque C to the electric motor 9. The estimator determines on the basis of information I3 an effort F4 greater than F3 image of the traction of the engine of the tractor vehicle 1c since the tractor vehicle 1c is obliged to provide more effort to maintain its speed. According to the control logic 40, it indicates to the inverter to supply a pair of value C4 image of F4. The control strategy 40 detects that F4 has exceeded a threshold and tells the inverter to control the motor with a torque C4 image of F4 and modulated by the control logic 40,
- the convoy is moving again on flat ground. The driver decides to slow down using the speed bump. Thanks to information from the braking system: brakes released and speed higher than a so-called “near-zero” speed, the ECU tells the inverter that it can provide torque to the electric motor. The estimator determines on the basis of the information I3 a negative force F5 image of the braking due to the retarder. According to the control logic 40, it tells the inverter to supply a negative torque of value C5 image of an effort F5 which allows it to partially recharge the battery,
- the driver decides to slow down more sharply by using the conventional braking system. Thanks to the information from the braking system: brakes controlled at a certain value and speed above a so-called “virtually zero” threshold speed, the ECU indicates to the inverter that it can supply negative torque C to the electric motor 9. According to the control logic 40, it tells the inverter to supply a negative torque of value C6 image of the slowdown desired by the conventional braking system which allows it to partially recharge the battery,
- the driver decelerates until he reaches a so-called “almost zero” threshold speed. According to the control logic 40, the ECU indicates to the inverter to no longer supply torque.

It should also be noted that it is necessary to readjust the alignment of the accelerometer with the vehicle. This can be done at the factory at startup.

Obviously, the invention is not limited to the preferred embodiment described above and shown in the various figures, the person skilled in the art being able to make numerous modifications thereto and imagining other variants without departing either from the scope or of the scope of the invention defined by the claims. Thus, a technical characteristic described or an implementation step described may be replaced by an equivalent technical characteristic, respectively an equivalent implementation step, without departing from the scope and scope defined by the claims.

Claims (18)

Method for power controlling an electric axle (2) of a towed vehicle (1), of the trailer or semi-trailer type, towed by a towing vehicle to form a convoy, said electric axle (2) being associated with at at least one electric motor (9) for providing traction assistance to the convoy during traction by the tractor vehicle (1c), consisting in determining a torque setpoint (C) for the electric motor (9) using a datum effort relating to the tractive effort exerted by the tractor vehicle (1c) on the convoy, characterized in that it comprises the steps:
- using physical parameter sensors placed on the convoy to provide measured data relating to said convoy,
- using an inertial sensor placed on the towed vehicle (1) to provide measured data relating to the acceleration of the convoy,
- performing a fusion of the data from the sensors present on the convoy, said fusion of the data being based on the use of at least one calculation algorithm,
- estimate by calculation and from the result of the data fusion, the traction force to determine the force datum, and
- calculate in real time a torque setpoint (C) for the electric motor (9) to participate in the traction or braking forces of the convoy. Piloting method according to Claim 1, characterized in that the fusion of the data coming from the sensors comprises the use of a Kalman filter, which performs at least the fusion of the data coming from the sensors, in particular the data coming from the inertial sensor, the speed of the electric motor (9), the mass of the convoy and the torque setpoint (C) transmitted to the electric motor (9) to provide estimated physical and dynamic parameter values of the convoy. Steering method according to Claim 2, characterized in that the estimation of the force datum comprises the following steps:
- (e1) from a torque setpoint (C) supplied to the electric motor (9) using the force applied to the wheel (8) of the electric axle (2), estimate the traction force and the reference speed V _R of the convoy corresponding to predicted or estimated values relating to the towed vehicle (1), thus determining a dynamic state of the convoy,
- (e2) measure the acceleration and speed values of the convoy,
- (e3) readjusting the dynamic state according to the difference between the actual measured values and the predicted values and according to the Kalman gain calculated on the basis of the confidences attributed to the measured quantities,
- Repeat steps (e1), (e2) and (e3) continuously. Control method according to Claim 2 or 3, characterized in that the data comprise values measured via an EBS system. Steering method according to Claim 4, characterized in that the mass of the convoy is estimated from the mass of the towed vehicle (1), measured by the EBS system, the mass of the towing vehicle (1c) being substantially constant. Control method according to Claim 4 or 5, characterized in that it consists in reducing the torque setpoint (C) of the electric motor (9) according to a linear law of reduction gain as a function of the radius of gyration of the towed vehicle ( 1) resulting from a non-parallelism between said towed vehicle (1) and the tractor vehicle (1c), using the estimated values of the rotational speed of the towed vehicle (1) in yaw and of the longitudinal speed. Control method according to Claim 6, characterized in that it consists in using values corresponding to the slope of the vehicle (1). Piloting method according to any one of Claims 4 to 7, characterized in that it consists in using an inertial sensor to measure acceleration values along a vertical axis of the towed vehicle (1) so as to take account of vibrations resulting from road irregularities, which are likely to generate erroneous tractive effort values. Steering system for implementing the steering method according to any one of Claims 1 to 8, characterized in that it comprises an electric motor (9) associated with an electric axle (2) and equipped with a sensor of angular position, an inverter, a power supply system (4) of the high voltage battery type, an EBS system, at least one wheel speed sensor (8), a filtration and data fusion system (50 ) to merge sensor data, at least one inertial sensor with at least one axis to perform a longitudinal acceleration measurement, a control system comprising a filtration system, a control logic (40) to manage the traction chain and to provide the torque setpoint (C) of the electric motor (9). Piloting system according to Claim 9, characterized in that it comprises a battery charging system. Piloting system according to Claim 9 or 10, characterized in that the inertial sensor comprises three axes performing respectively a measurement of longitudinal, transverse and vertical acceleration. Piloting system according to any one of Claims 9 to 11, characterized in that it comprises a gyroscope. Piloting system according to any one of Claims 9 to 12, characterized in that it comprises an ABS or EBS system. Steering system according to any one of Claims 9 to 13, characterized in that the control logic (40) integrates a fuel consumption model of the tractor vehicle (1c), used to determine to what extent the steering method must be triggered. Piloting system according to any one of Claims 9 to 14, characterized in that the data filtration and fusion system (50) integrates a model of the friction of the wheel (8) on the ground and/or a model of the air friction on the cabin of the convoy. Steering system according to any one of Claims 9 to 15, characterized in that it equips a trailer. Steering system according to any one of Claims 9 to 15, characterized in that it equips a semi-trailer. Computer program product that can be loaded directly into a memory unit of a computer, a digital tool or a computer system, to control the implementation of the steps of any one of claims 1 to 8, when the instructions of said computer program product are executed on the computer, digital tool or computer system.