Method for detecting a mechanical shutdown state of a three-cylinder four-stroke thermal engine

Abstract

Method for detecting a mechanical stop of a three-cylinder thermal engine implemented by a computing unit, configured to detect a rising edge, respectively falling edge, of a voltage signal of a magnetic crankshaft sensor, the method comprising: a step of triggering a time delay TStopEstim, and a step of estimating a mechanical stop when the time delay TStopEstim is finished.The method further comprises, prior to the triggering step, upon each detection of a rising edge of the voltage signal: a step of determining a direction of rotation of the motor, then when the determined direction of rotation corresponds to a reverse direction of rotation; a step of detecting an inflection of the rotation speed, then; a step of calculating a value Tp from a current value of a measurement of the rotation speed of the motor and a predetermined law of temporal evolution of the decrease of the rotation speed of the motor, the predetermined law of temporal evolution of the decrease of the rotation speed being an affine law of predetermined slope, then the step of triggering the time delay TStopEstim, the value of the time delay TStopEstim being equal to the value Tp, then the step of estimating a mechanical stop when the time delay TStopEstim is finished. Figure for publication: Figure 1.

Description

Title of the invention: Method for detecting a mechanical shutdown state of a three-cylinder four-stroke thermal engine Field of the invention

[0001] The present invention relates to a method for detecting a mechanical shutdown state of a three-cylinder four-stroke thermal engine. Prior art

[0002] Starting an internal combustion engine is conventionally facilitated by a starter, which comprises a shaft provided with a pinion enabling the rotation of the engine to be initiated by gearing with a pinion carried by the latter.

[0003] During a possibly brief stop of the engine, it is necessary to determine a complete stop state in order to be able to restart the engine. Indeed, if the engine is not completely stopped when the starter is operated, the engagement of the gears can damage the engine and the starter.

[0004] The combustion cycle of an internal combustion engine comprises several phases whose occurrence is offset in time for each cylinder, the synchronized control of the valves of the thermal engine being carried out by the camshaft.

[0005] In order for the combustion cycle to proceed normally, it is necessary to have a reliable angular reference on the basis of which each phase of each cylinder is determined.

[0006] The camshaft is rotated by the crankshaft. The crankshaft is a mechanical device which, by means of a connecting rod, allows the transformation of the rectilinear movement of a piston into a continuous rotational movement, and vice versa, thus ensuring the transmission of the combustion energy of the fuel in the cylinders into mechanical energy.

[0007] Thus, knowledge of the angular position of the crankshaft makes it possible to know a reliable angular reference on the basis of which each phase of each cylinder is determined.

[0008] Such a reference is available via a toothed wheel, also called a target, integral in rotation with the crankshaft. The wheel is associated with a dedicated sensor, called a crankshaft sensor, whose role ultimately is to enable the determination of the angular position and the rotational speed of the toothed wheel. The sensor is equipped with a sensitive element. According to one example, the wheel is metallic and the sensitive element is capable of detecting metal, such as a Hall effect sensor. The profile of the wheel typically includes a target which is provided with markers, also called teeth, distributed around its periphery. The function of the crankshaft sensor is to transform the magnetic field measured as an electrical signal. According to the state of the art, some sensors are connected to the control unit by three wires (ground, power supply and signal) and have the ability to determine the direction of rotation of a crankshaft target. The passage of a tooth of the gear associated with the crankshaft generates an electrical pulse on the signal wire. The predetermined duration is representative of the direction of rotation (typically 45 ps for a forward direction of rotation, and 90 ps for a reverse direction of rotation). The crankshaft sensor is typically mounted near the flywheel which serves as a rotating target or supports such a target.

[0009] The rotating target has a signature, also called a long tooth or gap, formed by a singularity in the profile (otherwise regular) usually corresponding to two missing marks, and which makes it possible to fix a reference for the position of the crankshaft. Such a signature generates a signal different from the other marks, which makes it possible to determine when the rotating target has completed a complete rotation.

[0010] A commonly used rotating target includes 60 marks distributed around the periphery of the rotating target, and two consecutive marks removed to create the signature. Such a target is called a 60-2 rotating target. Another known rotating target is the 36-2 rotating target (34 marks plus two missing marks).

[0011] The rotation of the rotating target causes periodic changes in the magnetic flux due to the passage of the markers, which are transformed by the sensor into voltage variations which can subsequently be sent to the engine management computer. The voltage variations comprise rising edges and falling edges forming a periodic signal synchronized with the passage of the markers in front of the sensor.

[0012] From the voltage data produced by the crankshaft sensor, the person skilled in the art knows how to calculate the rotational speed and the angular position of the crankshaft to obtain the basic data necessary for determining the injection point and adjusting the ignition advance point.

[0013] To determine an engine stop state, it is known to use the data acquired by the crankshaft rotation sensor. The engine stop is detected at the end of a time delay, for example 300 ms, started from the last detected tooth. If a new tooth is detected before the time delay expires, the time delay is interrupted and the engine is considered to be moving.

[0014] This method involves systematically waiting for the end of the time delay, i.e. 300 ms, to detect an engine stop, and therefore to authorize the restart of the engine. However, it is desirable to be able to restart the engine as quickly as possible, for example in vehicles equipped with an automatic stopping and restarting device for the engine of a vehicle of the “stop and start” type or analogous, for example in circumstances known as change of mind (for example, arriving at a red light which turns green when stopping).

[0015] Furthermore, the toothed targets mounted on the crankshafts of the engines have a spacing between two consecutive teeth of at least 6°. Consequently, if there remains in particular a movement of the engine which is contained within this angular amplitude of 6°, this movement will not be detected. Thus, this detection method only allows one to conclude with certainty that the engine has stopped after a very long time.

[0016] Document FR3076861 is known, which proposes a method for detecting the physical shutdown of a four-stroke internal combustion engine comprising at least four cylinders.

[0017] The above method does not work for three-cylinder four-stroke engines. In fact, the method is based on the analysis of the oscillations of the engine during stopping. These oscillations are characteristic of 4-stroke combustion engines with 4 or more cylinders (a compression phase of one cylinder is always counterbalanced by a combustion phase of another cylinder).

[0018] The invention aims to overcome the drawbacks of the prior art described above.

[0019] In particular, an aim of the invention is to enable the detection of a mechanical shutdown state of a three-cylinder four-stroke thermal engine within a time of less than 300 ms.

[0020] Another aim of the invention is to enable the engine to be stopped with certainty. Statement of the invention

[0021] To this end, according to a first aspect of the invention, a method for detecting a mechanical stoppage of a three-cylinder thermal engine is proposed, implemented by a computing unit, configured to detect a rising edge, respectively falling edge, of a voltage signal from a magnetic crankshaft angular position sensor, the voltage signal having rising and falling edges corresponding to detections of rising and falling edges of a series of teeth of a toothed wheel mounted integral with the axis of rotation of the crankshaft, the method comprising: • a step for triggering a TStOpEstim timer, and • a step of estimating a mechanical stop when the time delay TStOpEstim is over.

[0022] The step of triggering the timer TStOpEstim consists of triggering a clock carrying out a countdown from an initial time value t=Tinit.

[0023] A TStOpEstim timer is finished when it reaches the value t=0.

[0024] If applicable, a new step of triggering the time delay TStOpEstimest implemented before a previously triggered timer reaches t=0, which postpones an estimation time of a mechanical stop. This is the case, for example, in the event of a new detection of a rising or falling edge before the timer has ended.

[0025] The method further comprises, prior to the step of triggering the time delay, upon each detection of a rising or falling edge of the voltage signal: • / a / a step of determining a direction of rotation of the motor, then when the determined direction of rotation corresponds to a reverse direction of rotation, • / b / a step of detecting an inflection in the rotation speed, then • / c / a step of calculating a Tp value from a current value of a measurement of the rotational speed of the motor and of a predetermined law of temporal evolution of the decrease in the rotational speed of the motor, the predetermined law of temporal evolution of the decrease in the rotational speed being an affine law of predetermined slope, then • / d / the triggering step of the timer TstopEStim, the value of the tem porization TstopEstim being equal to the value Tp, then • ld the step of estimating a mechanical stop when the TstopEStim time delay is over.

[0026] Advantageously, the method may further comprise: • an initialization step prior to the step of determining a direction of rotation of the motor / a / , the initialization step comprising the assignment of a zero value to a variable xA, and • the step of determining a direction of rotation of the motor / a / further comprising the assignment of a unit value to the variable xA when the direction of rotation of the motor determined during the step of determining a direction of rotation of the motor / a / corresponds to a reverse direction of rotation, and • subsequently to the step of determining a direction of rotation of the motor / a / and if the determined direction of rotation of the motor corresponds to a forward direction of rotation, for each detection of a rising or falling edge, • a step of comparing the variable xA and the unit value, then if the variable xA is equal to the unit value, • the step of triggering the TStopEstim timer, the value of the TstopEstim timer being equal to a predetermined timer value called the Tmaigin margin timer.

[0027] The method may comprise, subsequently to the step of determining a direction of rotation of the motor / a / if the determined direction of rotation of the motor corresponds to a forward direction of rotation, or subsequently to the comparison step Er when it exists and that the variable xA is not equal to the unit value, for each detection of rising edge, respectively falling edge, a step Es comprising the assignment to the time delay TstopEstim of a predetermined time delay value called safety time delay Tsafe, then the step of triggering the time delay TStopEstim-

[0028] According to another aspect of the invention, a module is proposed for detecting a mechanical stoppage of a three-cylinder thermal engine, the module implementing a calculation unit configured to detect a rising edge, respectively falling edge, of a voltage signal from a magnetic crankshaft angular position sensor, the voltage signal having rising and falling edges corresponding to detections of rising and falling edges of a series of teeth of a toothed wheel mounted integral with the axis of rotation of the crankshaft and, for each of the detected edges: • trigger a TStopEstim timer, and • estimate a mechanical stop when the time delay TstopEstim is over,

[0029] The calculation unit is further configured to, prior to the step of triggering the time delay: • determine a direction of rotation of the motor, then when the determined direction of rotation corresponds to a reverse direction of rotation, • detect an inflection in the engine rotation speed if the determined direction of rotation of the engine corresponds to a reverse direction of rotation, then • calculate a value Tp from a current value of a measurement of the rotation speed of the motor and a predetermined law of temporal evolution of the decrease in the rotation speed of the motor, the predetermined law of temporal evolution of the decrease in the rotation speed being an affine law of predetermined slope, then • trigger the TStopEstim timer, the value of the TStOpEstim timer being equal to the value Tp, then • estimate the mechanical stop when the TStopEstim time delay is over. Brief description of the figures

[0030] Other characteristics and advantages of the invention will appear during the reading of the detailed description which follows for the understanding of which reference will be made to the appended drawings in which: • [Fig.l] illustrates a characteristic graph of the evolution of the rotation speed of a three-cylinder four-stroke thermal engine before it stops, • [Fig.2] illustrates an embodiment of a method according to the invention, • [Fig.3] illustrates an embodiment of a module according to the invention and its physical environment. Detailed description of the invention

[0031] The embodiments described below being in no way limiting, it will be possible in particular to consider variants of the invention comprising only a selection of characteristics described, subsequently isolated from the other characteristics described, if this selection of characteristics is sufficient to confer a technical advantage or to differentiate the invention compared to the state of the prior art. This selection comprises at least one characteristic, preferably functional without structural details, or with only a part of the structural details if this part alone is sufficient to confer a technical advantage or to differentiate the invention compared to the state of the prior art.

[0032] [Fig.l] represents a characteristic graph of the evolution of the rotation speed of a three-cylinder four-stroke thermal engine (on the ordinate) as a function of time (on the abscissa) when the engine is stopped.

[0033] The curve typically represents 4 parts: • a first part of reduction of the rotational speed of the engine due to friction and the transfer of rotational energy towards the increase of the gas pressure in the cylinder in the compression stage, the engine continuing to rotate in a forward direction of rotation, • a second part A of the start of reversal of the direction of rotation of the engine, initiated by a transition instant T corresponding to the piston reaching the maximum relative high position, the speed of movement of the piston increasing due to the expansion of the gas, • a third part B following part A, during which we observe an inflection in the rotation speed of the engine, the piston being accelerated by the expansion of the previously compressed gas, • a fourth part C following part B, during which we observe a reduction in the speed of the engine due to the reduction in pressure and an increase in friction until it stops at time Ts.

[0034] There is now described, with reference to [Fig.2], an embodiment of a method P for detecting a mechanical stoppage of a three-cylinder thermal engine implemented by a calculation unit Uc, at the same time as a module M implementing a calculation unit Uc.

[0035] The method and the module according to the invention take advantage of the existence of a magnetic device S of crankshaft angular position A.

[0036] The magnetic device S generates a voltage signal representative of the passage of a tooth comprising, for each detected tooth, a rising edge and a falling edge. It is thus possible to determine the rotation speed by analyzing the signal generated by the magnetic device.

[0037] The magnetic device S is for example a bidirectional sensor of the CPDD type, for Crankshaft Position and Direction Determination, capable of generating signals of different widths depending on the direction of rotation of the crankshaft. It is thus possible to determine the direction of rotation by analyzing the signal generated by the magnetic device. For example, with the sensor considered, the falling electrical edge and the rising electrical edge are spaced apart by a duration of 45 ps when the toothed wheel moves in one direction of rotation, and by a duration of 90 ps when the toothed wheel moves in the other direction of rotation.

[0038] The magnetic sensor S is typically associated with a magnetic target C mounted integral with the rotation of the crankshaft A.

[0039] The calculation unit Uc is configured to detect a rising edge, respectively a falling edge, of the voltage signal of the magnetic crankshaft angular position sensor, the voltage signal having rising and falling edges corresponding to detections of rising and falling edges of a series of teeth of a toothed wheel mounted integral with the axis of rotation of the crankshaft.

[0040] The method P comprises: • a step Ed for triggering a TStOpEstim timer, and • a step Ee for estimating a mechanical stop when the time delay T stopEstimate is over.

[0041] According to the invention, the method further comprises, prior to the step of triggering the time delay, upon each detection of a rising or falling edge of the voltage signal: • / a / a step Ea of determining a direction of rotation of the motor, then when the determined direction of rotation corresponds to a reverse direction of rotation, • / b / a step Eb of detection of an inflection of the rotation speed, then • Here a step Em of calculating a value Tp from a current value of a measurement of the rotation speed of the engine and a predetermined law of temporal evolution of the decrease in absolute value of the rotation speed of the engine, then • / d / the trigger step Ed of the time delay TStOpEstimla value of the tem porization TstopEstimating equal to the value Tp, then • Here the step of estimating a mechanical stop when the TStOpEstim time delay is over.

[0042] Step Ea of determining a direction of rotation of the motor / a /

[0043] According to one possibility, the step Ea of determining the direction of rotation of the engine can implement a variable available at the level of an ECU unit for controlling the engine or a software component monitoring the signal from the crankshaft sensor, in English driver. Said variable can have a value depending on the direction of rotation of the motor. The detection of a reverse direction of rotation then consists of receiving an event of change of state of this variable, or of monitoring the change of state of this variable.

[0044] According to another possibility, the step Ea of determining a direction of rotation of the motor can for example implement an acquisition of the signal generated by the device S, when the latter makes it possible to determine the direction of rotation. In this case, the step Ea of determining a direction of rotation of the motor is carried out by processing the acquired signal.

[0045] When the determined direction of rotation of the motor corresponds to a reverse direction of rotation, the method continues with step Eb of detecting an inflection in the rotation speed of the motor / b / . Stage Eb

[0046] According to one possibility, the step Eb of detecting an inflection in the rotation speed of the engine can for example be initiated by a change of state of a variable associated with the detection of an inflection in the rotation speed. This variable can for example be available at the level of the engine control ECU unit.

[0047] According to one possibility, the step Eb of detecting an inflection in the rotation speed of the engine may for example be initiated by a change of state of a variable associated with the detection of an inflection in the rotation speed. This variable may for example be available at the level of the engine control ECU unit.

[0048] According to another possibility, the step Eb of detecting an inflection in the rotation speed of the motor may comprise an acquisition of the rotation speed of the motor.

[0049] The rotational speed of the engine may for example be known to the engine control unit, and the acquisition of the rotational speed of the engine then consists of receiving the rotational speed of the engine from the control unit.

[0050] Alternatively, the acquisition of the rotation speed of the motor can for example implement the processing of an acquired voltage signal generated by the device S.

[0051] When step Eb of detecting an inflection in the rotation speed of the motor / b / comprises the acquisition of the rotation speed, step Eb further comprises a determination of the passage through a maximum of the rotation speed.

[0052] The determination of the passage through a maximum of the rotation speed is for example detected when the absolute value of the gradient of the evolution of the rotation speed is less than a predetermined threshold.

[0053] Noting Tsysn and Tsysn+_i the absolute times of detection of passage of two consecutive teeth in front of the crankshaft sensor, and Tn the time difference between these two instants Tsysn and Tsysn+_i and Sn the rotation speed obtained by the formula Sn=Toothlenght / Tn, where Toothlenght is the angular distance between two teeth (or two consecutive fronts of the same nature) (for example 6° for a 60-2 target or 10° for a 36-2 target), the gradient Grdn of the evolution of the speed can be written: Grdn = (Sn-S n_i) / Tn. The determination of the passage through a maximum of the rotation speed is for example detected when the absolute value of Grdn is lower than a predetermined ThresholdGrd value, with for example ThresholdGrd=50 rpm / s (for the English revolutions per minute per second).

[0054] When an inflection in the rotation speed of the motor is detected, the method continues with step Em of calculating a value Tp. Step Em of calculating a Tp value

[0055] Knowledge of the time law and the current value of the rotation speed makes it possible to update the time delay by assigning it the value of the time remaining before stopping the motor. For example, if the current speed at time t is v(t), and knowing the graph makes it possible to determine a time ts accordingly, from which the speed will be zero. The process can then continue with the triggering of the time delay with the predetermined value ts.

[0056] The predetermined law of temporal evolution of the decrease in the rotation speed can be approximated by an affine law of predetermined slope. In other words, the temporal law of the decrease can be approximated linearly by a predetermined decrease slope, noted slope. For example, slope = 750 rpm / s.

[0057] The process can then continue with the triggering of the time delay with the value Tp = Sn / slope.

[0058] Preferably, the value of the time delay Tp can be increased by a margin time delay Tmaigin, for example Tmargin=50ms.

[0059] According to one possibility, the method may comprise an acquisition of a current temperature. The current temperature may be measured, for example by means of a temperature sensor. The module may alternatively receive the current temperature information from the engine control unit ECU. This is usually the oil or cooling water temperature, which are closest to the sensor value and the crankshaft target. The value of the decay slope may be modified depending on the measured temperature.

[0060] Step Ee of detecting a mechanical stop when the time delay is over

[0061] When the time delay ends, the method detects a mechanical stop when the time delay is over. Optional step Er

[0062] According to a first variant, described only for its differences, the method P may comprise an initialization step Ei prior to the determination step Ea mination of a direction of rotation of the motor / a / , which involves the assignment of a zero value to a variable xA.

[0063] Step Ea of determining a direction of rotation of the motor / a / comprises the assignment of a unit value to the variable xA when the direction of rotation of the motor determined during step Ea of determining a direction of rotation of the motor / a / corresponds to a reverse direction of rotation.

[0064] Subsequent to step Ea of determining a direction of rotation of the motor / a / and if the determined direction of rotation of the motor corresponds to a forward direction of rotation, for each detection of a rising edge, respectively a falling edge, the method continues with a step Er of comparing the variable xA and the unit value, then if the variable xA is equal to the unit value, by the step Ee of triggering the time delay TstopEstim, the value of which is equal to the margin time delay Tmargin.

[0065] When the variable xA is not equal to the unit value, the method continues with step Es if it exists. Optional Step Es

[0066] According to a second variant, possibly combinable with the first variant, the method comprises an optional step Es which begins when the direction of rotation of the motor determined by step Ea is a forward direction of rotation, or subsequently to step Er when it exists and the variable xA is not equal to the unit value, for each detection of a rising edge, respectively a falling edge, preferably when the rotation speed of the motor decreases.

[0067] Step Es comprises the assignment to the time delay TstopEStim of a predetermined time delay value called safety time delay Tsafe.

[0068] The safety time delay value Tsafe is for example 300 ms.

[0069] Step Es continues with the step Ed of triggering the time delay whose value is equal to the predetermined time delay value. More generally

[0070] Prior to implementing the initialization step, the calculation unit may undergo a step of calibrating the decay slope.

[0071] According to one embodiment, the calibration step is carried out prior to the implementation of the method according to the invention, for example on a test vehicle representative of another vehicle equipped with the module M according to the invention. According to a variant, the calibration step can be implemented on a vehicle whose engine is new, for example after the replacement of the engine.

[0072] The module M according to the invention can be implemented in the form of an electronic module comprising a memory in which is stored a computer program product comprising instructions intended to be executed by the unit of UC calculation or by the engine control unit ECU which then replaces the UC calculation unit.

[0073] Finally, the method according to the invention and the corresponding module can be implemented with sensors other than magnetic ones, provided that the sensor is sensitive to the passage of reference elements of the target.

[0074] Of course, the invention is not limited to the examples which have just been described and numerous adjustments can be made to these examples without departing from the scope of the invention. In addition, the various characteristics, forms, variants and embodiments of the invention can be associated with each other in various combinations to the extent that they are not incompatible or exclusive of each other.

Claims

Claims

1. Method (P) for detecting a mechanical stop of a three-cylinder thermal engine implemented by a calculation unit (Uc) configured to detect a rising edge, respectively falling edge, of a voltage signal of a magnetic crankshaft angular position sensor, the voltage signal having rising and falling edges corresponding to detections of rising and falling edges of a series of teeth of a toothed wheel mounted integrally with the axis of rotation of the crankshaft, the method comprising: a step (Ed) of triggering a time delay TStopEstim, and a step (Ee) of estimating a mechanical stop when the time delay TstopEstim is finished, characterized in that it further comprises, prior to the step of triggering the time delay, upon each detection of a rising edge, respectively falling edge, of the voltage signal: / a / a step (Ea) of determining a direction of rotation of the engine,then when the determined direction of rotation corresponds to a reverse direction of rotation, / b / a step (Eb) of detecting an inflection in the rotation speed, then, / c / a step (Em) of calculating a value Tp from a current value of a measurement of the rotation speed of the motor and a predetermined law of temporal evolution of the decrease of the rotation speed of the motor, the predetermined law of temporal evolution of the decrease of the rotation speed being an affine law of predetermined slope, then / d / the step of triggering (Ed) the time delay TstopEStim, the value of the time delay TstopEStim being equal to the value Tp, then ld the step (Ee) of estimating a mechanical stop when the time delay TstopEStim is finished.

2. Method according to claim 1, further comprising: a step (Ei) of initialization prior to the step (Ea) of determining a direction of rotation of the motor / a / , the initialization step comprising the assignment of a zero value to a variable xA, and the step (Ea) of determining a direction of rotation of the motor / a / further comprising the assignment of a unit value to the variable xA when the direction of rotation of the motor determined during the step (Ea)

3.

4. determining a direction of rotation of the motor / a / corresponds to a reverse direction of rotation, and subsequently to the step (Ea) of determining a direction of rotation of the motor / a / and if the determined direction of rotation of the motor corresponds to a forward direction of rotation, for each detection of a rising edge, respectively falling edge, a step (Er) of comparing the variable xA and the unit value, then if the variable xA is equal to the unit value, the step (Ed) of triggering the time delay TStOpEstim, the value of the time delay TStOpEstim being equal to a predetermined time delay value called margin time delay Tmaigin. Method according to claim 1, further comprising, subsequently to step (Ea) of determining a direction of rotation of the engine / a / if the determined direction of rotation of the engine corresponds to a forward direction of rotation, or subsequently to step (Er) when dependent on claim 2 and the variable xA is not equal to the unit value, for each detection of a rising or falling edge, respectively, a step Es comprising the assignment to the time delay TstopEstim of a predetermined time delay value called safety time delay T safe, then the step (Ed) triggering of the time delay TstopEstim-Module (M) for detecting a mechanical stop of a three-cylinder thermal engine, the module implementing a calculation unit (Uc), configured to detect a rising or falling edge, respectively of a voltage signal from a magnetic crankshaft angular position sensor,the voltage signal having rising and falling edges corresponding to detections of rising and falling edges of a series of teeth of a toothed wheel mounted integral with the axis of rotation of the crankshaft and, for each rising edge, respectively falling edge, detected: trigger a time delay TStOpEstim, and estimate a mechanical stop when the time delay TStOpEstim is finished, characterized in that it is further configured to, prior to the step of triggering the time delay: determine a direction of rotation of the engine, then when the determined direction of rotation corresponds to a reverse direction of rotation, detect an inflection of the speed of rotation of the engine if the determined direction of rotation of the engine corresponds to a reverse direction of rotation, Then calculate a value Tp from a current value of a measurement of the rotation speed of the motor and a predetermined law of time evolution of the decrease of the rotation speed of the motor, the predetermined law of time evolution of the decrease of the rotation speed being an affine law of predetermined slope, then trigger the time delay TStopEstim, the value of the time delay T stopEstim being equal to the value Tp, then estimate the mechanical stop when the TStopEstim time delay is over.

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