Calibration method for a tilt sensor on a two-wheeled vehicle

Abstract

The invention relates to a method for calibrating a tilt sensor (111) for a two-wheeled vehicle (1), comprising the steps of: - selecting (E1) a two-wheeled vehicle (1) including said tilt sensor (111) to be calibrated, - tilting (E2) the vehicle (1) to a first predetermined lateral tilt angle, - recording (E3) the value of the projection of Earth's gravity onto the three axes, - tilting (E4) the vehicle (1) to a second predetermined lateral tilt angle, - recording (E5) the value of the projection of Earth's gravity onto the three axes, - calculating (E9) a projection matrix between the intrinsic frame of the tilt sensor (111) and the frame specific to the vehicle (1) from the projection of Earth's gravity onto the three axes of the intrinsic frame and the vehicle's frame (1), - recording (E10) the projection matrix calculated for each vehicle (1). Figure for the abstract: Fig 5

Description

Title of the invention: Method for calibrating a tilt sensor for a two-wheeled vehicle technical field

[0001] The present invention relates to the field of motorized two-wheeled vehicles and more particularly concerns the measurement of the vehicle's lateral inclination. Prior art

[0002] To improve driver safety, many motorized two-wheeled vehicles are now equipped with systems that can act directly on the operation of the vehicle, without the intervention of the driver, as soon as a critical situation is detected.

[0003] As is known, manufacturers of motorized two-wheeled vehicles include tilt sensors in these vehicles that measure, in particular, the lateral tilt of the two-wheeler. These sensors are configured to have a maximum tilt threshold above which the vehicle is considered to be falling, triggering the engine to shut off and thus ensuring the safety of the rider.

[0004] For example, if this threshold is 60° with respect to a vertical direction defined by Earth's gravity, and the effective angle of inclination of the two-wheeler is beyond 60°, the vehicle is considered to be falling and the engine is stopped.

[0005] This device also makes it possible to prevent the engine from starting if the vehicle is inclined beyond this threshold when switched on by the user.

[0006] A first generation of tilt sensors is of the mechanical type, and these tilt sensors are fixed to the vehicle chassis. These sensors contain weights (for example, balls) that move according to the vehicle's tilt and close electrical contacts when a given tilt angle is reached. The inertia of these weights then determines the sensor's sensitivity to the vehicle's tilt and, consequently, the accuracy of the angle measurement.

[0007] However, these sensors are bulky and impose significant mounting constraints on the vehicle chassis. For these reasons, a new generation of sensors is used, consisting of an electronic control unit containing a MEMS (Micro Electro Mechanical System) type accelerometer.

[0008] This sensor can be freely placed in the vehicle according to its design. This freedom, however, requires calibrating the sensor so that, once installed, the position and orientation of the sensor are known relative to a reference point. reference, so that this sensor measures a correct value for the vehicle's tilt angle.

[0009] If the sensor is incorrectly calibrated, its position and orientation relative to the vehicle's reference frame are not correctly taken into account by the electronic control unit. The tilt sensor then generates false tilt measurements, potentially triggering the engine shutdown function even if the vehicle's tilt is below the maximum acceptable threshold.

[0010] One solution to this problem is to calibrate the sensor when it is installed on a vehicle at the factory during the production of a series of vehicles of the same model. This ensures the correct measurement of the vehicle's tilt, but this calibration must be carried out individually for each vehicle, which takes considerable time during production.

[0011] There is therefore a need for a simple and effective solution to remedy at least some of these drawbacks. Description of the invention

[0012] To this end, the invention first relates to a method for calibrating a tilt sensor intended to be mounted on a motorized two-wheeled vehicle, said vehicle comprising an electronic control unit, said electronic control unit comprising said tilt sensor and a memory area, said tilt sensor being configured to determine the projection of Earth's gravity onto three axes of a frame intrinsic to the tilt sensor, the electronic control unit being configured to calculate the tilt angle from the projection of Earth's gravity onto the three axes of a frame specific to the vehicle, said method being partially implemented by a calibration device connected to the vehicle, and comprising the steps of:

[0013] - selection of at least one two-wheeled vehicle including said tilt sensor to calibrate,

[0014] - tilting of at least one selected vehicle to a first angle of inclination lateral determined,

[0015] - recording, by the calibration device, of the value of the projection of the Earth's gravity on the three axes of the tilt sensor's intrinsic frame of reference when at least one vehicle is tilted to the first lateral tilt angle,

[0016] - tilting at least one selected vehicle to a second angle of inclination predetermined lateral

[0017] - recording, by the calibration device, of the value of the projection of the Earth's gravity on the three axes of the tilt sensor's intrinsic frame of reference when at least one vehicle is tilted to the second lateral tilt angle,

[0018] - calculation, by the calibration device, of a projection matrix between the coordinate system intrinsic of the tilt sensor and the vehicle's own reference frame based on the projection of Earth's gravity onto the three axes of the intrinsic reference frame and the vehicle's reference frame,

[0019] - recording of the calculated projection matrix in the unit's memory area electronic control for each vehicle corresponding to the vehicle type including said electronic control unit.

[0020] This method allows for the rapid and efficient calibration of the electronic control unit for calculating the lateral tilt angle from the tilt sensor measurements. The method defines the vehicle's frame of reference by calculating three unit vectors perpendicular to each other from the Earth's gravity vector measured at each of the vehicle's two tilt angles in the tilt sensor's frame of reference. The 3x3 projection matrix, whose columns correspond to the three vectors thus calculated, allows the conversion from the tilt sensor's intrinsic frame of reference to this vehicle frame of reference, one axis of which is parallel to the vehicle's longitudinal direction.Once the projection matrix is ​​determined, it can be stored in the memory area of ​​each electronic control unit mounted on a vehicle corresponding to the selected vehicle, allowing immediate calibration of these vehicles and avoiding individual calibration of each one, which would be lengthy and costly.

[0021] Advantageously, the step of calculating the projection matrix between the intrinsic frame of the tilt sensor and the vehicle's own frame is performed by calculating the cross product of the Earth's gravity vector in the first tilt angle and the Earth's gravity vector in the second tilt angle, normalizing the Earth's gravity vector in the first tilt angle, normalizing the vector calculated by the cross product, calculating a third vector from the cross product of the two normalized vectors, and calculating the projection matrix whose columns are the three vectors thus normalized. Thus, the method makes it possible to calculate the vehicle's own frame and simultaneously define the projection matrix between the tilt sensor's intrinsic frame and this own frame.

[0022] Preferably, the difference between the first and second angles of inclination is greater than 15 degrees. In this way, the angle between the two measured Earth gravity vectors is sufficiently large to avoid approximation errors when calculating the cross product between these two vectors.

[0023] In a preferred embodiment, the method includes a preliminary step of verifying physical parameters necessary for calibration. This step is important to ensure that external parameters do not distort not the calibration and measurement of the tilt angle of vehicles under normal operating conditions.

[0024] In this embodiment, it is advantageous for the preliminary step of verifying physical parameters to include measuring the ground inclination. For example, this step could consist of comparing the ground inclination measurement to a threshold of 2° and issuing an alert if this threshold is exceeded.

[0025] Advantageously, the selection step consists of selecting a plurality of vehicles of the same model, and the vehicle tilting and gravity projection recording steps in the intrinsic frame are performed on each of the vehicles in said plurality of vehicles. Performing calibration on a plurality of vehicles thus prevents problems related to a single selected vehicle, such as an installation error or degradation of the tilt sensor, from distorting the calibration and thus all subsequent tilt angle measurements of the calibrated vehicles.

[0026] Advantageously, the step of calculating a projection matrix includes a substep of calculating the average of the plurality of projections of Earth's gravity onto the three axes of the intrinsic frame of reference for each of the vehicles in said plurality of vehicles. The calculation of the projection matrix is ​​thus performed on average values ​​that take into account slight divergences in the values ​​measured by the different tilt sensors.

[0027] Preferably in this embodiment, the average calculation step is followed by a substep for calculating the standard deviation from the average calculated for each of the selected vehicles, and the projection matrix calculation step is performed using the average of the measured projections corresponding to the vehicles with a standard deviation below a predetermined value. This makes it possible to identify, among the selected vehicles, those whose tilt sensor measurements are outside a confidence interval, thus indicating a problem, and that the vehicle(s) concerned should not be included in the projection matrix calculation to avoid introducing calibration errors.

[0028] According to another aspect, the invention also relates to a computer program product characterized in that it comprises a set of program code instructions which, when executed by one or more processors, configure the processor(s) to implement a process as presented.

[0029] According to another aspect, the invention also relates to a calibration device for calibrating the tilt angle measurement of at least one motorized two-wheeled vehicle, said vehicle comprising an electronic control unit, said electronic control unit comprising a tilt sensor and a memory area, said tilt sensor being configured to determine the gravity projection terrestrial on three axes of a frame intrinsic to the tilt sensor, the electronic control unit being configured to calculate the tilt angle from the projection of terrestrial gravity onto the three axes of a frame specific to the vehicle, said calibration device being configured to:

[0030] - be connected, via an electronic communication link, to the control unit electronic,

[0031] - record the value of the projection of Earth's gravity onto the three axes of a intrinsic reference point of the tilt sensor when the vehicle is tilted to a predetermined lateral tilt angle,

[0032] - calculate a projection matrix between the intrinsic frame of the sensor of inclination and the reference frame specific to the vehicle from the projection of terrestrial gravity onto the three axes of the intrinsic reference frame and the vehicle reference frame.

[0033] The calibration device allows the calculation of the projection matrix which is then recorded in the electronic control units so as to ensure calibration for each vehicle corresponding to the selected vehicle model. Brief description of the drawings

[0034] Other features and advantages of the invention will become apparent from the following description. This description is purely illustrative and should be read in conjunction with the accompanying drawings, in which:

[0035] [Fig-1] Fig. 1 schematically illustrates a motorized two-wheeled vehicle in to which the process according to the invention applies.

[0036] [Fig.2] Fig.2 schematically illustrates the vehicle tilted at both angles of inclination during the process according to the invention.

[0037] [Fig.3] Fig.3 schematically illustrates an electronic control unit of the calibrated vehicle.

[0038] [Fig.4] Fig.4 schematically illustrates the determination of the vehicle's reference frame based on the Earth's gravity vectors measured in the two inclinations of the vehicle.

[0039] [Fig.5] Fig.5 schematically illustrates the process according to the invention. Description of the implementation methods

[0040] The calibration process according to the invention is applied to a motorized two-wheeled vehicle 1 via a calibration device 2.

[0041] Vehicle 1

[0042] As shown in [Fig.1], the vehicle 1 comprises an engine 10, an electronic control unit 11 and a communication link 14.

[0043] During the calibration of vehicle 1, vehicle 1 is held in a predefined inclination by a holding device, which is not shown in the figures for reasons of clarity.

[0044] As shown in [Fig.2], vehicle 1 is tilted to a first inclination 01 and then to a second inclination 02.

[0045] It is necessary to define a reference frame specific to vehicle 1 with respect to which the angle of inclination of vehicle 1 is measured.

[0046] For a plurality of vehicles 1 of the same series, the electronic control unit 11 is identical and positioned in the same place in the vehicle 1, and following the same inclination.

[0047] Motor 10

[0048] The motor 10 makes it possible to produce the torque necessary to drive the wheels of the vehicle 1 when the vehicle 1 is moving.

[0049] The motor 10 is not in operation during the calibration process.

[0050] Electronic control unit 11

[0051] As shown in [Fig.3], the electronic control unit 11 includes a tilt sensor 111 and a memory area 112.

[0052] The tilt sensor 111 is preferably a MEMS type accelerometer, configured to calculate the projection of Earth's gravity onto three axes of a reference frame.

[0053] The tilt sensor reference frame is an intrinsic reference frame, that is to say, it depends solely on the arrangement of the components inside the tilt sensor 111.

[0054] The electronic control unit 11 is configured to calculate the angle of lateral inclination of the vehicle 1 with respect to the terrestrial vertical Z from the three projections measured by the tilt sensor 111.

[0055] Mathematically, to obtain the measurement of the angle, it is necessary to apply to the measurements of the tilt sensor 111, which are linked to the intrinsic frame, a projection matrix to adapt them to the frame of the vehicle 1 and allow the calculation of the tilt angle.

[0056] Memory area 112 is configured to store information. In particular, memory area 112 is configured to store the projection matrix calculated during the process according to the invention.

[0057] The electronic control unit 11 is configured to compare the calculated tilt angle with a tilt threshold.

[0058] The tilt threshold corresponds to the angle from which the electronic control unit 11 considers that the vehicle 1 is falling.

[0059] The electronic control unit 11 is configured to implement a function of stopping the engine 10 of the vehicle 1 if the measured lateral tilt angle is greater than the tilt threshold.

[0060] The electronic control unit 11 is configured to calculate the rotation matrix from the measurements of the tilt sensor 111 during the calibration process and to define an orthonormal frame for measuring the tilt angle of the vehicle 1.

[0061] Communication link 14

[0062] The communication link 14 enables communication between the electronic control unit 11 and the motor 10, and the communication device 2.

[0063] Preferably, the communication link 14 is a wired communication link.

[0064] Calibration device 2

[0065] The calibration device 2 is a computer device that connects to the vehicle 1, preferably in such a way as to be connected to the electronic control unit IL

[0066] Preferably, the calibration device 2 is a computer equipped with software to receive the measurements of the projections of Earth's gravity made by the tilt sensor 111 in the frame of said tilt sensor 111, to process these data by a spreadsheet and to store the data.

[0067] When the method is applied to a plurality of vehicles 1, the calibration device 2 is configured to calculate an average and a standard deviation of the measurements of the Earth's gravity projections of the plurality of vehicles 1.

[0068] Preferably, the calibration device 2 is configured to identify measurements associated with a standard deviation greater than a predetermined threshold, so as not to take them into account in the calculation of an average which is used to determine the projection matrix.

[0069] Example of implementation

[0070] During the calibration process according to the invention, a plurality of vehicles 1 are selected in a first step EL

[0071] Each selected vehicle 1 is installed in a calibration stand which allows the vehicle 1 to be tilted to a controlled tilt.

[0072] In another operating mode, the vehicle 1 is mounted on an adjustable stand that allows the vehicle's tilt angle to be varied when deployed. In this case, it is important to ensure beforehand the uniformity and inclination of the ground to avoid distorting the calibration. Ideally, the inclination of the ground should be less than 2°.

[0073] In a second step E2, each vehicle 1 is tilted to a first predetermined angle of inclination.

[0074] In a step E3, the calibration device 2 connected to the inclined vehicle 1 records the values ​​of the projections of Earth's gravity measured by the tilt sensor 111 in the intrinsic frame of said tilt sensor 111.

[0075] In a step E4, each vehicle 1 is tilted according to the second reference tilt angle.

[0076] In a step E5, the calibration device 2 connected to the vehicle 1, inclined according to the second angle of inclination, records the values ​​of the projections of the Earth's gravity measured by the tilt sensor 111 in the intrinsic frame of said tilt sensor 111.

[0077] In a step E6, the calibration device 2 calculates a mean and a standard deviation on each of the three gravity projections measured by the tilt sensor 111 for the two reference tilt angles.

[0078] In step E7, the calibration device 2 compares the standard deviations for each vehicle 1 with a predetermined threshold. If a standard deviation is greater than the threshold, the calibration device 2 excludes the data from the vehicle 1 concerned.

[0079] An excessively large standard deviation may indicate a fault in the assembly or operation of the electronic control unit 11 on the vehicle 1 in question. Basing the calibration on this vehicle 1 could then distort it and thus cause errors in the calculation of the tilt angle on all vehicles 1 in the corresponding series.

[0080] In a step E8, the calibration device 2 calculates an average value of each projection for the two reference inclination angles taking into account only the values ​​retained in step E7.

[0081] In a step E9, the electronic control unit 11 receives the two vectors corresponding to the average values ​​calculated in step E8 and determines the orthonormal frame of the vehicle 1 and the projection matrix between the intrinsic frame of the tilt sensor 111 and this frame of the vehicle 1.

[0082] As shown in [Fig. 4], this step begins by calculating the cross product between the two vectors gl and g2 corresponding to the Earth's gravity measured in the intrinsic frame of the tilt sensor 111 for the two tilt angles. The resulting vector glAg2 is perpendicular to the first two vectors gl and g2.

[0083] Then a vector e3 is calculated by normalizing the first vector of terrestrial gravity gl, that is to say by dividing it by its length to obtain a unit vector, with a norm equal to one.

[0084] The same operation is performed on the vector glAg2 resulting from the cross product to obtain a unit vector el.

[0085] Finally, a third vector e2 is calculated by the cross product between the vector e3 and the vector el. Due to the mathematical properties of the cross product, this vector itself has a norm equal to one and is perpendicular to the two vectors el and e3.

[0086] The frame formed by the vectors el, e2, e3 is therefore an orthonormal frame, and the projection matrix which allows us to go from the intrinsic frame of the tilt sensor 111 to this frame is the 3x3 square matrix whose columns correspond to the vectors el, e2 and e3.

[0087] Once the projection matrix has been calculated, it can be stored in a later step E10 in the memory area 112 of each electronic control unit 11 mounted on a vehicle 1 of the series corresponding to the selected vehicles 1.

[0088] This projection matrix allows each electronic control unit 11 to quickly and efficiently convert the values ​​measured by the tilt sensor 111 in order to calculate the lateral tilt angle relative to the reference frame of the vehicle 1, without having to calibrate each vehicle 1 individually.

Claims

1. Demands A method for calibrating a tilt sensor (111) intended to be mounted on a motorized two-wheeled vehicle (1), said vehicle (1) comprising an electronic control unit (11), said electronic control unit (11) comprising said tilt sensor (111) and a memory area (112), said tilt sensor (111) being configured to determine the projection of Earth's gravity onto three axes of a frame intrinsic to the tilt sensor (111), the electronic control unit (11) being configured to calculate the tilt angle from the projection of Earth's gravity onto the three axes of a frame specific to the vehicle (1), said method being partially implemented by a calibration device (2) connected to the vehicle (1), and comprising the steps of: - selection (El) of at least one two-wheeled vehicle (1) comprising said tilt sensor (111) to be calibrated, - inclination (E2) of at least one selected vehicle (1) to a first determined lateral inclination angle, - recording (E3), by the calibration device (2), of the value of the projection of Earth's gravity onto the three axes of the intrinsic frame of the tilt sensor (111) when at least one vehicle (1) is tilted to the first lateral tilt angle, - tilting (E4) of at least one selected vehicle (1) to a second predetermined lateral tilt angle, - recording (E5), by the calibration device (2), of the value of the projection of Earth's gravity onto the three axes of the intrinsic frame of the tilt sensor (111) when the tilting of at least one vehicle (1) to the second lateral tilt angle, - calculation (E9), by the electronic control unit (11), of a projection matrix between the intrinsic frame of the tilt sensor (111) and the vehicle's own frame (1) from the projection of Earth's gravity onto the three axes of the intrinsic frame and the vehicle's frame (1), - recording (E10) of the projection matrix calculated in the memory area (112) of the electronic control unit (11) for each vehicle (1) corresponding to the vehicle type (1) including said electronic control unit (11).

2. A method according to claim 1, wherein the step of calculating the projection matrix between the intrinsic frame of the tilt sensor (111) and the frame specific to the vehicle (1) is carried out by calculating the cross product between the Earth's gravity vector in the first tilt (gl) and the Earth's gravity vector in the second tilt (g2), by normalizing the Earth's gravity vector in the first tilt (gl), by normalizing the vector (glAg2) calculated by the cross product and by calculating a third vector (e2) from the cross product of the two normalized vectors (el, e3) and by calculating the projection matrix whose columns are the three vectors (el, e2, e3) thus normalized.

3. A method according to any one of the preceding claims, wherein the difference between the first angle of inclination and the second angle of inclination is greater than 15 degrees.

4. A method according to any one of the preceding claims, comprising a preliminary step of verifying physical parameters necessary for calibration.

5. A method according to the preceding claim, wherein the preliminary step of verifying physical parameters includes measuring the inclination of the ground.

6. A method according to any one of the preceding claims, wherein the selection step (El) consists of selecting a plurality of vehicles (1) of the same model, and the steps of tilting the vehicles (1) and recording the projection of gravity in the intrinsic frame are performed on each of the vehicles (1) of said plurality of vehicles (1).

7. Method according to the preceding claim, wherein the calculation step (E9) of a projection matrix includes a calculation substep (E6) of averaging the plurality of projections of Earth's gravity on the three axes of the intrinsic frame for each of the vehicles (1) of said plurality of vehicles (1).

8. A method according to the preceding claim, wherein the calculation step (E9) of the average is followed by a sub-step of calculating the standard deviation from the average calculated for each of the selected vehicles (1) and the calculation step of the projection matrix is ​​carried out from the average of the measured projections corresponding to the vehicles (1) exhibiting a standard deviation less than a predetermined value.

9. Product computer program characterized in that it comprises a set of program code instructions which, when executed by one or more processors, configure the processor(s) to implement a method according to any one of the preceding claims.

10. Calibration device (2) for calibrating the tilt angle measurement of at least one motorized two-wheeled vehicle (1), said vehicle (1) comprising an electronic control unit (11), said electronic control unit (1) comprising said tilt sensor (111) and a memory area (112), said tilt sensor (111) being configured to determine the projection of Earth's gravity onto three axes of a frame intrinsic to the tilt sensor (111), the electronic control unit (11) being configured to calculate the tilt angle from the projection of Earth's gravity onto the three axes of a frame intrinsic to the vehicle (1), said calibration device (2) being configured to: - be connected, via an electronic communication link, to the electronic control unit (11),- Calculate the projection of Earth's gravity onto the three axes of a vehicle frame (1) when the vehicle (1) is tilted to a lateral tilt angle; - Record the value of the projection of Earth's gravity onto the three axes of an intrinsic frame of the tilt sensor (111) when the vehicle (1) is tilted to a predetermined lateral tilt angle; - Calculate a projection matrix between the intrinsic frame of the tilt sensor (111) and the vehicle's intrinsic frame (1) from the projection of Earth's gravity onto the three axes of the intrinsic frame and the vehicle's frame (1).

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