CN112601695A

CN112601695A - Learning angular position of a three-axis accelerometer integrated into an electronic control unit of a vehicle engine

Info

Publication number: CN112601695A
Application number: CN201980046685.4A
Authority: CN
Inventors: J-L·弗雷莫
Original assignee: Vitesco Technologies GmbH
Current assignee: Vitesco Technologies GmbH
Priority date: 2018-07-13
Filing date: 2019-07-10
Publication date: 2021-04-02
Anticipated expiration: 2039-07-10
Also published as: TW202032127A; CN112601695B; TWI814865B; FR3083758B1; FR3083758A1; WO2020011900A1

Abstract

A method is disclosed for learning the angular position of an accelerometer having three measurement axes, integrated into an electronic control unit of a vehicle engine, relative to a reference axis of the vehicle. The method is based on the fact that: so that the computer of the electronic control unit can deduce this angular position on the basis of the acceleration values measured for each position applied to the vehicle by the user.

Description

Learning angular position of a three-axis accelerometer integrated into an electronic control unit of a vehicle engine

Technical Field

The present invention relates generally to a method for detecting the inclination of a vehicle by means of an on-board accelerometer, and more particularly by means of an accelerometer integrated into the electronic control unit of the vehicle engine.

The invention relates more particularly to a method enabling a three-axis accelerometer intended to measure the inclination of the vehicle in which it is installed to determine its reference orientation, from which all the inclination measurements of the vehicle can then be made. This operation may be referred to as a learning procedure.

The invention finds application in particular in vehicles of the motorcycle type (in short "motorcycles"), for example with two wheels and equipped with a safety system that makes it possible to stop the engine when a fall of the motorcycle is detected.

Background

In order to improve the safety of the driver, many motorized vehicles are nowadays equipped with systems that can directly act on the vehicle operation as soon as a critical situation is detected, without the need for driver intervention. This is the case, for example, for certain motor vehicles, where emergency braking is automatically triggered when the measured distance to a frontal obstacle is drastically reduced. This is also the case for motorcycles, where the engine automatically stops when a limit value of the lateral inclination, i.e. the inclination with respect to the vertical direction (defined here by the direction of gravity), is reached, which is similar to a motorcycle fall.

In the latter case, the triggering of the automatic action aimed at improving the safety of the driver is based on a real-time measurement of the motorcycle's lateral inclination, so as to determine at every moment whether the situation should be considered dangerous or not dangerous for the driver. Usually, such inclination measurements are carried out by means of dedicated autonomous sensors, i.e. independent sensors (in english "standalone(free standing) ") which is fixed to the frame or chassis of a motorcycle. The sensor reacts to the motion of the motorcycle frame. Based on the information generated by the sensor and transmitted to the engine control computerUpon crossing the lateral tilt threshold, the engine control computer can cause the engine and its fuel supply to stop. Typically, the engine is stopped when the motorcycle reaches a lateral inclination greater than 60 ° with respect to the vertical, for example during a certain duration greater than a time threshold. It is in fact considered that exceeding such an angle necessarily means that the motorcycle falls, and in such a case it is better to stop the engine and its fuel supply, in order to reduce the risks associated with the rotation of the driving wheels and their transmission chain, as well as the risks of the machine catching fire. This then improves the safety of the driver and its surroundings. Furthermore, in some countries, regulations dictate this function.

To enable this function, it is common to resort to mechanical type sensors fixed on the chassis of the vehicle, in which a load (for example a ball) moves according to the inclination of the vehicle and closes an electrical contact when a given inclination is reached. The inertia of these loads then determines the sensitivity of the sensor to vehicle inclination, and the accuracy of the angle measurement.

These sensors are widely used in particular for motorcycles equipped only with an ignition device and a carburetor supplied by an oil pump, and motorcycles equipped with an electronic control unit that controls the operation of an engine by means of pressurized fuel injection. In the first case, the sensor is associated with a switching type device arranged in the ignition circuit to cut off the high voltage supply directly to the spark plug and cause the fuel supply to the engine to stop when a limit inclination angle is reached. In the second case, the sensor transmits the measurement information to the electronic control unit, which stops the engine and cuts off the power supply to the fuel pump when the limit inclination angle is reached, so as to eliminate the pressure in the injection circuit.

Whatever the vehicle concerned, the positioning of such sensors at the chassis of the motorized vehicle involves not only fixed constraints to ensure the stability of its orientation over time, but also integrated constraints related to the dimensions of the sensors themselves and to the connections required to connect the sensors to the vehicle elements with which they are fitted. However, this type of restraint can be a serious obstacle, especially for certain light vehicles, such as for example certain motorcycles.

Furthermore, such a freestanding tilt angle sensor is itself a component whose direct cost and the costs associated with its connection are relatively large in the overall cost of the associated safety function.

In order to cope with the above problems, the following facts are known: accelerometers made on silicon in the form of integrated electronic components are used to measure tilt relative to the vertical of the electronic device into which they are incorporated. For which the injection engine is controlled by an electronic control unit (or of english) "Electronic Control Unit", ECU") into which electronic components may be integrated. This solution has the advantage of being compact and lightweight and is particularly suitable for certain motorized vehicles, such as for example motorcycles, scooters or golf carts.

In fact, such accelerometers may have dimensions of the order of only a few millimetres or even less, so that their integration can be done directly on an electronic circuit board (carte electronic) or even in a single-chip computer chip of the ECU, and therefore do not exhibit any noteworthy dimensions nor require specific connections.

Patent application EP 1184233 a1 discloses such a system. The innovation described in this document relates to an accelerometer directly integrated in the ECU of the motorcycle to measure its lateral inclination, so as to be able to detect a possible fall thereof. The use of an integrated accelerometer instead of a mechanical type sensor external to the ECU has the following advantages: provides good measurement accuracy and reduces the size and cost associated with such an inclination sensor. Furthermore, in the case described in this application, the implementation of a speedometer within the ECU also enables the use of measurements made by the accelerometer to detect a possible collision between the vehicle and an obstacle.

However, despite its obvious advantages, there is still one major drawback to placing the accelerometer directly in the ECU controlling the vehicle engine: it requires adherence to very strict constraints of position in the vehicle, and orientation in three-dimensional space of the computer incorporating the accelerometer. In practice, the angle of inclination of the vehicle is measured with respect to the vertical, and therefore the sensor must be arranged (i.e. must be oriented with respect to a reference axis of the vehicle) so as to make one of these measurement axes coincide with the direction of gravity when the vehicle itself is perfectly vertical. This is also the case for accelerometers that measure with respect to either two or three axes (and are then referred to as two-axis or three-axis accelerometers, respectively).

Therefore, a strict angular positioning of the ECU must be ensured during installation, so that the direction of one of the measuring axes of the accelerometer overlaps with the direction of gravity with very little error. This constraint is more costly in that the orientation of the accelerometer relative to the vehicle may vary slightly depending on the type of fixation used for the original installation of the ECU and depending on the need to replace the ECU, or the willingness of the disassembly/reinstallation operations for repair or maintenance of the vehicle. This may then cause all inclination measurements made later to be erroneous as soon as the proper angular positioning of the accelerometer is not or no longer strictly adhered to.

Patent application EP 3031707 is also known, which relates to a method and a control unit enabling the determination of the overturning of a motorcycle. The electronic control unit integrates a processing device which uses the three acceleration values ax, ay and az along the three measuring axes X, Y, Z to determine the possible overturn (tumble) of the motorcycle. By combining the three acceleration values ax, ay, az along the three measurement axes X, Y, Z, the spatial orientation of the acceleration vectors can be known, and thus the spatial orientation of the motorcycle and the acceleration vectors, and the spatial orientation of the three-axis accelerometer sensor 16 relative to the motorcycle can be known. A "unique" calibration step is performed (usually at the end of the motorcycle mounting line) in which the actual measurements of the triaxial accelerometer sensors are learned, so that systematic errors due to structural scatter of the electronic components and mounting inaccuracies can be compensated. In particular, during this "sole" certification step, the motorcycle is arranged in a predetermined certification position, according to which it is normally vertical, so that the values of the longitudinal acceleration ax and of the lateral acceleration ay are equal to zero, and the acceleration az along the vertical axis Z is equal to the gravitational acceleration of the predetermined certification position. The present invention seeks to obviate or at least mitigate all or part of the above-mentioned disadvantages of the prior art, and to propose an improvement to this prior art.

Disclosure of Invention

To this end, a first aspect of the invention proposes a method for learning the angular position of an accelerometer with three measurement axes with respect to a reference axis of a vehicle, the accelerometer being integrated into an electronic control unit of an engine of the vehicle, said electronic control unit comprising a computer adapted, in operation, to continuously retrieve an acceleration vector from the accelerometer, the acceleration vector comprising three acceleration values x, y, z respectively measured along three measurement axes X, Y, Z of the accelerometer, said method comprising:

during the determined first duration, maintaining the vehicle in an angular position such that the reference axis of the vehicle is completely or substantially aligned with the vertical direction, and calculating, by the computer, three average acceleration values, one for each of the three measurement axes of the accelerometer, based on a series of triplets of acceleration values measured by the accelerometer during said first duration; then, the user can use the device to perform the operation,

calculating by the computer an angular correction vector determined on the basis of three angular values corresponding to the angular position of the accelerometer with respect to the reference axis of the vehicle, the three angular values themselves being determined on the basis of the three average acceleration values obtained in the preceding step; and finally, the user can select the desired position,

storing the angular correction vector in a non-volatile memory of the computer to correct for deviations between the angular position of the accelerometer and the vehicle reference axis for subsequent determination of the angular position of the vehicle relative to vertical based on acceleration measurements produced by the accelerometer.

By means of the invention, an ECU controlling the engine of a vehicle can be made to learn or relearn the orientation of an accelerometer integrated into the ECU relative to the vehicle in which it is installed, as many times as desired. This orientation can then be stored and enables a reference to be established for all lateral inclination measurements of the vehicle subsequently made by means of the accelerometer.

According to the invention, during the first duration and when the vehicle is placed on a substantially plane ground, the operator keeps the vehicle in a substantially vertical angular position, and the method further comprises:

during a first duration, compensating for the deviation between two by two of three average acceleration values by adding a determined constant algebraic value, called compensation value, to each of these three average acceleration values, respectively, the three compensation values being such that the three average values compensated by the three compensation values are substantially equal to each other; then, the user can use the device to perform the operation,

during a second duration, the operator tilts the vehicle on a first side of the vehicle by an angle greater than the determined first angular threshold with respect to the vertical, then the operator tips the vehicle on the other side, so as to obtain, after said tipping, a tilt of an angle greater than the determined second angular threshold with respect to the vertical, and the end user puts the vehicle back in a substantially vertical position;

during a second duration, calculating by the computer the difference between the maximum and minimum acceleration values measured and compensated by their respective compensation values, and determining an angular position, referred to as the reference position of the vehicle, defined by the three measured acceleration values that give the minimum value for said difference; and the number of the first and second groups,

calculating, by the computer, an angular correction vector, the angular correction vector being determined on the basis of three angular values corresponding to the angular position of the accelerometer with respect to the reference axis of the vehicle, the three angular values being based on the difference between the acceleration value measured by the accelerometer for the reference position of the vehicle as determined in the previous step on the one hand and the average acceleration value obtained for the substantially vertical position of the vehicle on the other hand.

Embodiments considered individually or in combination also suggest:

suspending the vehicle to be subjected to gravity only during a first duration of time to bring the reference axis of the vehicle into perfect alignment with the vertical;

the determined first duration is greater than or equal to 5 seconds;

the first and second angle thresholds are greater than or equal to 10 degrees;

during a second duration, a verification step is carried out during which, respectively:

-the computer verifying whether a first maximum value of the difference between the maximum acceleration value and the minimum acceleration value measured and compensated by their respective compensation values is reached when the vehicle is tilted to the first side;

-the computer verifying whether a second maximum value of said difference is reached when the vehicle rolls over to the other side;

-the computer verifying whether a minimum of said difference between the first maximum and the second maximum is reached; and the number of the first and second groups,

-the computer verifying whether the average acceleration value calculated during the first duration and the acceleration value obtained at the occurrence of the reference position are comprised between the determined limit values;

-if at least one of said verification steps gives a negative result, the computer aborts the method;

initiating the method in response to an action by an operator comprising pressing a mechanical or tactile button and/or activation of a handle or other physical control member of the vehicle; and/or the presence of a gas in the gas,

the initiation, propulsion and/or interruption of the method is signaled to the user by an audible and/or visual signal.

In a second aspect, the invention also relates to a method of using a computer of an electronic control unit of an engine of a motor vehicle, the method comprising: in the step of the learning method according to any of the method embodiments according to the first aspect in the learning phase, and in the control phase of the engine in operation:

continuously determining the lateral inclination angle of the vehicle corrected by the angular correction vector with respect to the vertical direction by means of an accelerometer integrated in the computer having three measuring axes; and the number of the first and second groups,

stopping the engine when the lateral tilt angle corrected by the angular correction vector reaches a value greater than a determined threshold for a duration greater than the determined threshold.

In a third aspect, the invention is also directed to an electronic control unit of a vehicle engine comprising a computer in the form of an electronic circuit board integrating at least a microprocessor, a non-volatile memory and an accelerometer, the computer being adapted to perform the following operations in any one of the embodiments of the method according to the first aspect: calculating an average value, adding a algebraic value, calculating a difference, determining the occurrence of a maximum or minimum value, calculating an angle, and the non-volatile memory is adapted to store an angle correction vector.

Drawings

Other features and advantages of the present invention will become apparent upon reading the following description. This description is purely illustrative and should be read in conjunction with the accompanying drawings, in which:

figures 1A and 1B are schematic views respectively showing a side view of a motorcycle in which the method can be implemented and a front view of the motorcycle according to three respective inclinations with respect to the vertical;

figures 2A and 2B show a simplified representation of an accelerometer having three measurement axes, and a curve of the acceleration values measured along the three axes of the accelerometer over time, respectively;

figure 3 is a step diagram illustrating an embodiment of the method according to the invention;

figure 4 is a schematic diagram illustrating another embodiment of the method according to the invention;

fig. 5 is a step diagram showing an embodiment of the method according to the invention, according to the schematic description thereof given with reference to fig. 4; and the number of the first and second groups,

figure 6 is a functional diagram of an ECU in which the method according to the invention can be implemented.

Detailed Description

Fig. 1A and 1B are schematic diagrams illustrating by way of example a side view and a front view, respectively, of a motorcycle 101 in which a method according to an embodiment of the invention may be implemented. However, the method may be implemented in any other type of motorized vehicle having two, three or four wheels, such as for example a scooter, a four-wheel motorcycle, a mini-tractor or a golf cart.

The vehicle is equipped with a jet engine. The engine is controlled by an Electronic Control Unit (ECU). The accelerometer is disposed in the ECU. As mentioned in the introduction, the measurement of the inclination of the vehicle provided by the accelerometer enables the ECU to switch off the engine in the event of a fall of the vehicle. In fact, the fact that the engine continues to run when the vehicle falls brings an additional risk to the driver and an additional risk to the vehicle. Thus, stopping the engine in the event of a vehicle fall improves driver safety and reduces vehicle risk.

The inclination referred to here and which is the origin of triggering the engine stop is the lateral inclination of the vehicle with respect to the vertical (on one side or the other, with respect to the direction of movement thereof). "vertical direction" means herein the direction of gravity.

In fig. 1A and 1B, the vertical direction of the chassis of the vehicle 101 is indicated by a thick arrow Z1, and a thick arrow Z1 is oriented in a direction from bottom to top. The longitudinal direction of the vehicle chassis, also corresponding to its direction of linear movement, is indicated by the thick arrow X1, the thick arrow X1 being oriented in the direction from the rear to the front. Finally, the lateral direction of the vehicle chassis is indicated by the thick arrow Y1, the thick arrow Y1 being oriented in the right-to-left direction. When the vehicle 101 is perfectly straight on a flat ground, the vertical reference direction Z1 is parallel to the vertical direction, and the reference directions X1 and Y1 form a plane parallel to the ground plane.

Fig. 1B shows various lateral inclinations of the motorcycle 101 of fig. 1A with respect to the vertical direction. At 101a, the motorcycle is in a vertical position, that is to say the vertical reference axis Z1 of the motorcycle is parallel to the direction of gravity. In

positions

101b and 101c, the motorcycle is tilted along its right and left sides, respectively, by an angle θ in both cases. This angle (called in English "bank angle(inclination angle) ") defines a measure of the inclination of the motorcycle relative to the vertical. The ECU relies on continuous measurement and monitoring of the value of this angle to stop the engine in the event of a lateral fall of the vehicle.

Fig. 2A presents a simplified representation of the accelerometer 102, the accelerometer 102 measuring acceleration along arbitrarily selected three axes X, Y and Z (e.g., three two-by-two orthogonal axes). As will be seen more specifically later, the tri-axial accelerometer allows for the determination of the precise angular orientation of the accelerometer 102 relative to the vehicle.

Fig. 2B gives an example of the evolution over time of the acceleration values measured on the three axes X, Y and Z when the vehicle is kept in a substantially vertical position and the accelerometers are mounted so that their measurement axes X, Y and Z overlap as accurately as possible the reference axes X1, Y1 and Z1 of the vehicle 101 shown with thick arrows in fig. 1A and 1B. In this configuration according to the schematic diagram of fig. 2B, only the measurement axis Z1 of the accelerometer (which therefore overlaps the vertical direction) records a non-zero signal (i.e. a signal with a value of 1g and with a small amount of fluctuation, where g is the unit of acceleration, corresponding approximately to the gravitational acceleration of the earth's surface) during the measurement duration. Further, in such a configuration, the lateral inclination angle θ is obtained by the following relationship:

where x, y, and Z are acceleration values measured along each of the X, Y and Z axes of the accelerometer 102, respectively, "Abs" is an absolute value, and "Arctan" is an Arctan function.

Referring to the step diagram of fig. 3, an embodiment of the method will now be described. From the operator's perspective, this embodiment is static in the sense that it does not involve any intentional tilting of the vehicle in which the accelerometer is disposed. This embodiment is particularly suitable for motorized vehicles having four wheels. Using this method enables an accurate determination of the angle between the measuring axis Z and the direction of gravity (relatively small, due to installation-induced angular positioning errors).

The starting scenario described in step 401 assumes that the engine is at a standstill and initiates a method of determining the orientation of the accelerometer relative to the vehicle. The method may be initiated (but is not limited to) by a user by: activating a control member connected to the ECU, such as pressing a mechanical or tactile button, activating a handle, or any other physical interaction of the user with the vehicle control member.

During step 402, the vehicle is in a strictly vertical position for a certain duration. For example, if the vehicle is a motorcycle, it may be suspended above the ground from the point of the chassis which is located on a straight line with its centre of gravity, so that it is subjected to gravity only, while remaining in a stable vertical position. If the vehicle is a four-wheeled vehicle, such as a four-wheeled motorcycle, the same result can be achieved by placing the vehicle on a perfectly flat surface. In all cases, the computer calculates three mean values < x >, < y > and < Z > based on a series of triplets { x, y, Z } of acceleration values x, y and Z measured by the accelerometer for each of the accelerometer's measurement axes X, Y and Z, respectively. The computer then analyzes the stability over time of the acceleration values measured during this duration, for example by calculating the standard deviation relating to the three mean values respectively.

During step 403, the computer verifies the actual stability of the vehicle during step 402. For example by verifying whether the standard deviation obtained is smaller than a given threshold value, or by ensuring that the magnitude of the variation of the acceleration value in the series of values considered is smaller than a given threshold value. If not, the method is interrupted at step 404. Conversely, if so, the method continues to step 405.

During step 405, the computer calculates an angle characterizing the angular orientation of the accelerometer relative to the vehicle based on the average acceleration value obtained in step 402. These three values define the angular correction vector.

During step 406, the computer stores, for example in non-volatile memory, the reference angle (angular correction vector) characterizing the orientation of the accelerometer relative to the vehicle obtained during "step 405" above.

Finally, in step 407, the ECU ends the method of determining the orientation of the accelerometer and activates the function of measuring the inclination of the vehicle using the accelerometer.

Furthermore, the ECU may control the activation of signals during the steps, said signals being intended to inform the user of the current situation. In particular, in one embodiment, an engine fault indicator light (English is "Malfunction Indicator Light”，MIL) may blink at various given frequencies, or continuously light up, or go out completely, to signal to the user, for example, events in the list, including the method starting, preparing a duration countdown for acquiring the acceleration values provided by the accelerometer, the remaining time to perform this step, the method interrupting after an unverified condition (e.g., during step 403), or confirming the final completion of the method.

Fig. 4 schematically shows another embodiment of the method according to the invention. In contrast to the above described embodiment, this embodiment is dynamic from the operator's point of view in the sense that it involves an intentional tilting of the vehicle in which the accelerometer is placed.

In the upper part of fig. 4, the evolution over time of the acceleration values measured along the three measurement axes X, Y and Z of the accelerometer, according to the lateral inclination of the motorcycle in which the accelerometer is disposed, is shown in three curves, respectively in dotted, solid and dashed lines. The mounting of the ECU on the vehicle chassis may be relatively similar in terms of the angular orientation of the ECU relative to the chassis' reference axes X1, Y1 and Z1.

The change in the angular position of the motorcycle over time (i.e. the change in the inclination of the motorcycle relative to the vertical) is illustrated by the motorcycle representation in front view in the middle of fig. 4, which are the acceleration values measured at the same instant in time for each measurement axis against the accelerometer at the respective instant in time of the embodiment of the method.

Fig. 4 shows five different phases of execution of the method, which are performed by the operator after initiation of the method. These five stages are represented from left to right and are designated in fig. 3 by the numbers 1 to 5 in the boxes, respectively:

a first phase 1 during which the user keeps the motorcycle in a substantially vertical position for a certain duration. This duration is of the order of a few seconds, typically of the order of 5 seconds, so that the computer of the ECU (as described below) can calculate an average value based on a series of acceleration values measured along each of the three measurement axes of the accelerometer;

second stage 2, during which the user tilts the vehicle on one side (i.e. the left side in the example shown, but it could also be the right side) by the angle he or she grasps. A good execution of the method preferably exhibits a significant inclination, in view of the accuracy of the acceleration measurement, so that the value of the angle reaches or exceeds an angle threshold of at least 10 degrees;

the third phase 3, during which the user re-stands the vehicle and tips it to the other side in the vertical direction to obtain the inclination of the vehicle at that other side (thus the right side in the example shown). The other side is precisely the side opposite the first side above with respect to the position in which the vehicle rests vertically stable on a flat ground solely under the influence of gravity. This tipping is preferably continuous, operating without stopping and without backing off (one or more) for reasons related to the processing of measurement data as will be elucidated later;

a fourth phase 4 during which the user tilts the vehicle on said other side up to or beyond an angular threshold of, for example, at least 10 degrees, in the same way as during the second phase; and finally

Fifth stage 5, during which the user resets the vehicle in the vertical position.

All the phases from the second phase to the fifth phase are spread out during a duration framed such that the computer of the ECU, which performs the calculations described below simultaneously with these operations, can process a sufficient amount of data to obtain a good calculation accuracy without this amount of data being excessive to limit the calculation time to a reasonable time.

In fact, after having initiated the method and in parallel with the execution of the above operations, the computer of the ECU performs the following operations shown in the lower part of fig. 4:

during the first phase, the computer calculates three mean values < x >, < y > and < Z > based on a series of triplets { x, y, Z } of acceleration values x, y and Z measured by the accelerometer for each of the accelerometer's measurement axes X, Y and Z, respectively, during the duration of the first phase 1. The computer then compensates for the deviation between the three averages by adding a constant algebraic value to one or more of the averages. That is, for example, it adds the two smallest average acceleration values to the respective constant values adapted to be equal to the third average value (as shown in the lower part of fig. 4) once the addition is performed. The compensation can also be obtained, for example, by adding the corresponding compensation values so that all average values fall around zero.

During the execution of the second, third and fourth phases, the computer calculates at each instant the difference between the maximum and minimum values of the acceleration measured by the accelerometer (in particular as indicated by arrows 201 and 203). Based on this calculation, the computer extracts a first maximum 201 of the difference, a second maximum 203 of the difference, and a minimum 202 of the difference between the two maxima 201 and 203 (graphically corresponding to the intersection of the three curves). As mentioned above, the user preferably tips the vehicle over continuously without stopping or backing up. In particular, so as to enable unambiguous isolation of a unique minimum between two maxima respectively associated with the inclination of the vehicle on both sides.

During a fifth phase, the computer uses the three acceleration values measured by the accelerometer for a reference position of the vehicle, in order to calculate an angle (i.e. an angular correction vector) corresponding to the orientation of the accelerometer with respect to the vehicle based on these three acceleration values and also based on the acceleration values obtained for the vertical position of the vehicle.

Thus, advantageously, at the end of the method, the ECU knows (learns) the angular position of the accelerometer relative to the vehicle. The ECU uses knowledge of these angles, where appropriate, to correct the value of the lateral tilt angle of the vehicle measured in real time (in a manner known per se to the person skilled in the art).

It will be appreciated by those skilled in the art that the method is preferably performed when the vehicle is on a flat and substantially horizontal surface during the various steps of the method. Thus, the accelerometer only measures acceleration values that are only related to the lateral inclination of the motorcycle that the operator dynamically applies, said acceleration values not being related to other inclinations, they being only static errors due to the inclination of the ground.

In fact, the fact that such measurements are made when the vehicle is on an incline, in particular along an incline in the direction of movement thereof, entails the risk of measuring, by the accelerometer, acceleration values in an axis related to the inclination of the ground, which values are, by nature, constant values, which are considered as interfering values with respect to the absolute acceleration measurement. Of course, these constant values will compensate each other, so that certain embodiments of the method implement a dynamic method based on the difference in acceleration values, by which static errors are eliminated by calculation. However, this should preferably be avoided during the execution of the steps of the method.

Likewise, the method can be carried out both in a configuration in which the suspension is recessed (infonc), in particular due to the presence of the user on the motorcycle, and in a configuration in which the suspension is not recessed. However, in the first case, for the same reasons as those described above, the trim of the motorcycle (in other words, the inclination in the direction of movement thereof) should not be changed by the load exerted on the motorcycle during the execution of the steps of the method.

With reference to the step diagram of fig. 5, an embodiment of the method according to the invention as schematically described with reference to fig. 4 will now be described.

In the starting situation in the figure corresponding to step 301, consider for example that the engine is in a stopped state when initiating the method for determining the orientation of the accelerometer relative to the vehicle. The method may be initiated (but is not limited to) by a user by: activating a control member connected to the ECU, such as pressing a mechanical or tactile button, activating a handle, or any other physical interaction of the user with the vehicle control member.

During step 302, the user holds the vehicle in a substantially vertical position for a duration of time (e.g., 5 seconds). A substantially vertical position refers to a position which is a priori very unstable, in which the motorcycle can remain upright, i.e. not to one side or the other, under the action of gravity only and therefore, in particular, without the user exerting any reaction force to prevent the motorcycle from tipping over and falling to the ground. And during this duration the computer calculates three average acceleration values < x >, < y > and < Z > for each of the X, Y and Z measurement axes of the accelerometer, respectively. In addition, the computer generates a compensation value capable of compensating for a deviation between the values by adding a constant value so that the values are equal to each other after the compensation is added.

During step 303, the user tilts the vehicle on a first side (e.g., left side) by an angle of inclination of about 15 ° while the computer calculates the difference between the maximum and minimum values of acceleration measured by the accelerometer at each instant.

During step 304, the computer verifies (e.g., by calculating the derivative of the difference) whether the difference determined in step 303 has indeed reached a maximum value. In other words, the computer verifies whether, after a given duration, the user no longer continues to increase the inclination of the vehicle, but stabilizes it or starts to roll back (i.e. re-erects the motorcycle to its vertical position). If not, the method is interrupted at step 314. Conversely, if so, the method continues to step 305.

During step 305, the user tips the vehicle to the other side (i.e., the right side in this example) and tilts it at an angle of inclination of about 15 °, preferably without stopping and backing up. During the time of this operation, the computer always calculates the difference between the maximum and minimum values of the acceleration measured by the accelerometer.

During step 306, the computer verifies (again by, for example, calculating the derivative of the difference) whether the difference determined during execution of step 305 has indeed reached a minimum value. If not, the method is interrupted at step 314. If so, in turn, the method continues to step 307.

During step 307, the user again holds the vehicle in a substantially vertical position and the computer continues to calculate the difference between the maximum and minimum values of acceleration measured by the accelerometer.

During step 308, the computer verifies whether the maximum of the calculated difference is indeed reached after the minimum value confirmed in step 306. If not, the method is interrupted at step 314. Conversely, if so, the method continues to step 309.

During step 309, the computer compares the average acceleration value obtained during step 302 with the acceleration value obtained when the minimum of the difference between the maximum and minimum of the measured acceleration occurs.

During step 310, the computer verifies whether the value compared at step 309 is likely to be true (vraisablable). In other words, whether these values are included between the true limit values. If not, the method is interrupted at step 314. Conversely, if so, the method continues to step 311.

During step 311, the computer calculates an angle characterizing the angular position of the accelerometer relative to the vehicle based on the difference between the average acceleration value obtained in step 302 and the acceleration value obtained when the minimum of the differences between the maximum and minimum of the measured acceleration occurs.

During step 312, the computer stores the reference angle characterizing the orientation of the accelerometer relative to the vehicle obtained in step 311, for example, in non-volatile memory.

Finally, in the case where the method described in the figure at step 313 ends, the ECU ends the method of determining the orientation of the accelerometer and activates the function of measuring the inclination of the vehicle using the accelerometer.

Thus, as already described with reference to fig. 4, where the angular position of the accelerometer relative to the vehicle is known, the accelerometer can be used to ensure the fidelity of the inclination measurement of the vehicle relative to the vertical, regardless of how the ECU is mounted to the vehicle.

In addition, in the same way as the embodiment of the method described with reference to fig. 3, in order to enable the user to ensure the correct deployment of the method from its triggering, the ECU may control the activation of a signal during the steps, said signal being intended to inform the user of the current situation. In other words, various signals, such as light or sound signals, may be used in order to indicate to it which step is in progress or whether the method is in progress, has been interrupted or has been completed.

For example, in one particular embodiment, an engine fault indicator light (in English:) "Malfunction Indicator Light", MIL) flashes, lights continuously, or goes out completely at various given frequencies to indicate to the user, for example: method start, step in progress, time remaining to perform this step, method interruption after an unverified condition (e.g., during

steps

304, 306, 308, 310), or confirmation of final completion of the method.

Fig. 6 is a schematic representation of an ECU in which the method according to the embodiment of the invention described above may be implemented. Thus, the ECU 501 is integrated with an electronic circuit board 502 (corresponding to a computer), the electronic circuit board 502 comprising, in a non-limiting manner, a microprocessor 503, a memory 504 (for example of the non-volatile type) and an accelerometer 505. Thus, the memory 504 stores an angle value defining the relative angular position of the accelerometer with respect to the vehicle obtained at the end of the method. In this way, all subsequent measurements of the lateral inclination of the vehicle by means of the integrated accelerometer take into account the actual orientation of the accelerometer, which results on the one hand from the mounting of the accelerometer in the ECU and on the other hand from the mounting of the ECU in the vehicle.

The present invention has been described and illustrated in this detailed description and in the various figures of the drawings in possible embodiments. However, the invention is not limited to the presented embodiments. Other variations and embodiments can be made and practiced by those skilled in the art upon a reading of the specification and the drawings.

In the claims, the term "comprising" or "comprises" does not exclude other elements or other steps. The invention may be implemented using a single processor or several other units. Various features that are presented and/or claimed may be advantageously combined. Their presence in the description or in different dependent claims does not exclude this possibility. The reference signs should not be construed as limiting the scope of the invention.

Claims

1. Method for learning the angular position of an accelerometer (102) having three measurement axes with respect to a reference axis (Z1) of a vehicle (101), the accelerometer being integrated into an electronic control unit (501) of a vehicle engine, said electronic control unit comprising a computer (502) adapted to continuously retrieve, in operation, an acceleration vector from the accelerometer, the acceleration vector comprising three acceleration values (x, y, Z) measured respectively along three measurement axes (X, Y, Z) of the accelerometer, the method comprising:

maintaining the vehicle at an angular position during the determined first duration so as to bring the reference axis (Z1) of the vehicle into full or substantial alignment with the vertical direction, and calculating, by the computer, three average acceleration values, one for each of the three measurement axes of the accelerometer, based on a series of triplets of acceleration values measured by the accelerometer during said first duration; then, the user can use the device to perform the operation,

storing an angular correction vector in a non-volatile memory of the computer to correct for a deviation between an angular position of the accelerometer and a reference axis of the vehicle for subsequent determination of an angular position of the vehicle relative to vertical based on acceleration measurements produced by the accelerometer,

wherein during the first duration and while the vehicle is placed on a substantially planar ground surface, the operator maintains the vehicle in a substantially vertical angular position, and the method further comprises:

2. The method of claim 1, wherein during the first duration, suspending the vehicle from gravity only to fully align the reference axis of the vehicle with the vertical direction.

3. The method of any of claims 1 or 2, wherein the determined first duration is greater than or equal to 5 seconds.

4. The method of any of claims 1-3, wherein the first and second angle thresholds are greater than or equal to 10 degrees.

5. The method of any of claims 1 to 4, further comprising: a verification step during a second duration, during which respectively:

the computer verifies whether a first maximum value of the difference between the maximum acceleration value and the minimum acceleration value measured and compensated by their respective compensation values is reached when the vehicle is tilted to the first side;

the computer verifying whether a second maximum value of the difference is reached when the vehicle is tipped to the other side;

the computer verifying whether a minimum of said difference between the first maximum and the second maximum is reached; and the number of the first and second groups,

the computer verifies whether the average acceleration value calculated during the first duration and the acceleration value obtained at the occurrence of the reference position are comprised between the determined limit values;

and wherein the computer interrupts the method if at least one of said verification steps gives a negative result.

6. The method of any one of claims 1 to 5, initiated in response to an action by an operator comprising pressing a mechanical or tactile button and/or activation of a handle or other physical control member of the vehicle.

7. The method according to any one of claims 5 and 6, wherein the initiation, advancement and/or interruption of the method is signaled to the user by an audible and/or visual signal.

8. A method of using a computer of an electronic control unit of an engine of a motor vehicle, the method comprising: in the steps of the learning method according to any one of claims 1 to 7 in the learning phase, and in the control phase of the engine in operation:

9. An electronic control unit of a vehicle engine comprising a computer in the form of an electronic circuit board integrated with at least a microprocessor, a non-volatile memory and an accelerometer, the computer being adapted to perform the following operations according to any one of claims 1 to 7: calculating an average value, adding a algebraic value, calculating a difference, determining the occurrence of a maximum or minimum value, calculating an angle, and the non-volatile memory is adapted to store an angle correction vector.