EP2219931A1

EP2219931A1 - Device for measuring the movement of a self-guiding vehicle

Info

Publication number: EP2219931A1
Application number: EP07871826A
Authority: EP
Inventors: Alain Maire; Said El Fassi
Original assignee: Siemens Transportation Systems GmbH and Co KG; Siemens Transportation Systems SAS
Current assignee: Siemens SAS
Priority date: 2007-12-10
Filing date: 2007-12-10
Publication date: 2010-08-25
Anticipated expiration: 2027-12-10
Also published as: TW200931308A; CA2708580A1; BRPI0722245A2; CN101939203A; KR101157756B1; WO2009074725A1; KR20100103572A; ATE510747T1; PL2219931T3; ES2366148T3; EP2219931B1; US20110029180A1; CN101939203B; BRPI0722245B1; DK2219931T3; US8571741B2

Abstract

A device for measuring the movement of a self-guiding vehicle, that has an enhanced measuring reliability, in particular during an adhesion loss and independently from the travel profile of the vehicle in terms of slope, turn and slant. To this end, the device for measuring the movement of a self-guiding vehicle includes on board thereof two accelerometers coupled to a movement calculator, wherein each accelerometer includes two measurement axes on which are measured projections of a vehicle acceleration resultant. The four measurement axes of the accelerometers are adjusted so that the calculator provides, from the four projection measures, at least one very accurate longitudinal acceleration value of the vehicle at each point of a route including both slopes and turns.

Description

Device for measuring the movement of a self-guided vehicle

The present invention relates to a device for measuring the displacement of a self-guided vehicle according to the preamble of claim 1.

Several methods or devices for measuring the displacement, speed or acceleration of a vehicle are nowadays known, in particular for vehicles intended for public transport such as a wagon unit of a train, a subway, a trolleybus , a tramway, a bus or such as any other vehicle pulled in traction by at least one running track or a rail such as a guide rail. Particularly in the case of a vehicle self-guided by a traffic system (rail signals, autopilot on board and / or remote from the vehicle, etc.) _/ precautions to ensure safe (against a breakdown) and secure autoguiding (for passengers or goods) is essential regardless of the vehicle's driving properties. In this sense, it is essential to know in real time the position, speed (and acceleration) of the vehicle, especially for situations where the vehicle is likely to incur inevitable loss of adhesion such as when slippage (during acceleration of the vehicle) or jamming (during braking of the vehicle) of free measuring axle or engine.

When the guided vehicle has an axle free of any traction or braking force, the movement of the vehicle is directly given by the rotation of the axle (or one of the wheels associated with this axle).

However, this solution reduces the power of traction or braking thus the performance of the vehicle, which is why most systems do not offer free axles. In the absence of free axle and to overcome the consequences related to skidding / clutch loss of adhesion of one of its wheels, several devices exist and use:

- Either totally independent measuring means of the wheels for an optical speed measurement or by means of a Doppler radar. These expensive devices, however, most often use an additional tachometer for low speed operation and stopping of the vehicle, the latter making it possible to extract the angular speed of a wheel or the number of wheel revolutions per minute. unit of time;

- Inertial units combining accelerometers, gyrometers and terrestrial positioning systems such as GPS. These, however, remain very expensive because of their high-level technology, most often for applications to aeronautical systems;

or, as in EP 0 716 001 B1, a single tachometer placed on an axle and means for taking into account a margin of safety to the values measured on one or the wheels in order to attempt to compensate for the effects of a possible skidding / jamming, which degrades the measurement performance of displacement because is still too approximate. It also follows a compensation anti-clutch that can be brutal for a vehicle and its passengers or goods; or, as in US 2005/0137761 A1, an accelerometer embedded in the vehicle and a tachometer on an axle whose measurement signals are connected to a central computer adapted, even if not explicitly described, to take into account errors introduced in the presence of loss of grip and delivering the speed and position of the vehicle on its path. In particular, the accelerometer comprises two measurement axes for respectively determining an acceleration along a direction of trajectory of the vehicle as well as for determining and therefore taking into account in the calculation of displacement a slope of the vehicle with respect to port to a horizontal plane. Measurement signal values of the accelerometer and the tachometer are also compared with speed threshold values which, if a threshold is exceeded, make it possible to indicate a presence of loss of adhesion (packing / jamming) of the vehicle. Although taking into account the effects of slope experienced by the vehicle, other effects related to the trajectory of the vehicle depending on the location of the accelerometer (and the positioning of its two axes of measurement) in the vehicle are inevitable. because a rail transport unit most often has an elongated geometry along which a single accelerometer and a tachometer placed upstream of the vehicle can not provide a measuring means revealing the effects acting on the complete whole of the vehicle, such as, for example, curvature or lateral acceleration effects.

All these devices thus make it possible to calculate the movement of a guided vehicle, having no axles free of any braking and traction force, traveling on any profile track, however with a precision well below that of a "ideal" free axle system, since they can not completely overcome the loss of adhesion (slippage and clutch induced by the traction / braking forces) as well as errors induced by lateral accelerations (curve, superelevation). ) or even vertical (slope).

An object of the present invention is to propose a device for measuring the displacement of a self-guided vehicle having an increased measuring robustness, in particular during a loss of adhesion and whatever the profile of the path of the vehicle in terms of slope, curve and slope.

For this purpose, a device for measuring the movement of a self-guided vehicle comprising on board two accelerometers, each having two measuring axes and whose measurement signals are coupled to a displacement calculator is proposed according to claim 1.

Optionally, at least one tachometer can be mounted on one of the axles of the vehicle and also be coupled with the computer data processing issues and all sensors (accelerometers and tachometer). The measurement signals delivered by the tachometer can be used to improve the accuracy of the device.

The device according to the invention delivers, from the accelerations measured on the measurement axes, velocity data and longitudinal displacement of the vehicle (for example along a railway track). It can be associated with any type of on-board device that may need a precise and continuous measurement of the speed and the displacement of the vehicle, independently of the raill / wheel adhesion conditions and whatever the profile of the path in term slope, curve and slope.

The accelerometers and their measurement axes are arranged in such a way that they make it possible, from the measurements made on the various measurement axes, to calculate a longitudinal acceleration, a lateral acceleration and a slope acceleration of the vehicle. determine by time integration the acceleration values, the speed and the longitudinal displacement of the vehicle.

The device according to the invention also advantageously makes it possible to detect in a safe manner an immobilization of the vehicle on its path and produces for this purpose a zero velocity information from the information delivered by the sensors.

The device comprises a self - calibration and self - test means which makes it possible, when the vehicle is stationary, to check the correct functioning of the sensors and consequently to guarantee with great confidence the data made available by other embedded systems.

A suitable use of the device according to the invention covers the field of guided vehicles whatever their type of guidance (mechanical or intangible that is to say without mechanical link between the ground and the vehicle), including trains, subways, tramway or bus, and whatever the type of bearing (axles, bogies) with wheels iron or tire. It should be noted that for this category of vehicle with a geometry / longitudinal frame, the effects of curvature and slope are not negligible depending on the position (or the offset) of the accelerometers on board the vehicle. The invention then makes it possible to overcome these effects advantageously in order to determine the movement of the vehicle more precisely.

The device according to the invention thus makes it possible to calculate the movement of a guided vehicle, having no axles free of any braking and traction force, traveling on any profile track, maintaining a precision equivalent to that of a free-axle system, while avoiding adhesion losses (slippage and skidding induced by traction / braking forces) and errors induced by lateral (curvature) and vertical (slope) acceleration.

A set of subclaims also has advantages of the invention.

Examples of implementation and application are provided using the figures described:

FIG. 1 a vehicle equipped with a device for measuring the movement of the self-guided vehicle according to the invention, FIG. 2 a diagram of definition of the planes related to the moving vehicle, FIG. 3 a diagram for taking into account the effect of slope on the device,

Figure 4 a diagram for taking into account the curvature effect on the device.

FIG. 1 represents a vehicle VEH equipped with a device for measuring the movement of the self-guided vehicle according to the invention and possibly associated with FIG. 2, clarifying how plans related to the moving vehicle are defined in agreement with the acceleration experienced by the vehicle and measured by two accelerometers 101, 102. Figures 3 and 4 show the arrangement of measurement axes Acc1, Acc2, Acc3, Acc4 accelerometers according to the plans chosen according to the type of acceleration Gx, Glat, Gpes ( longitudinal displacement, curvature effect and / or slope) undergone by the vehicle in an orthonormal reference [X, Y, Z] centered on the accelerometers and whose X axis indicates the direction of longitudinal trajectory of the vehicle.

The displacement measuring device (instantaneous position Dx) of the self-guided vehicle VEH comprises on board:

an accelerometer 101 provided with two measuring axes Accl, Acc2 in a longitudinal plane Py defined by a first longitudinal axis X along a main displacement VEx assumed to be straight of the vehicle and of a second axis Z perpendicular to the floor of the vehicle;

a computer 103 connected to an output signal S1, S2 associated with each measurement axis Accl, Acc2, where each output signal Sl, S2 comprises an orthogonal projection measurement Gac1c, Gacc2 of a resultant of global acceleration of the vehicle on the associated measurement axis Accl, Acc2,

a second accelerometer 102 being provided with at least two measurement axes Acc3, Acc4 in a horizontal plane Pz defined by the first axis X and a third axis Y perpendicular to the first and second axis X, Z,

the computer 103 is connected to an output signal S3, S4 associated with each measurement axis Acc3, Acc4, where each output signal S3, S4 comprises a measurement in projection

Gacc3, Gacc4 of the resultant global acceleration of the vehicle on the associated measurement axis Acc3 _f Acc4,

the set of measurement axes Accl, Acc2; Acc3, Acc4 of the first and second accelerometer 101, 102 have in their respective plane Py, Pz a relative angle A1 + A2, A3 + A4 being adjustable so adjusted, so that the computer 103 delivers from the four measurements of projection Gaccl, Gacc2, Gacc3, Gacc4 at least one instantaneous value of longitudinal acceleration Gx of the vehicle at each point of a path including slope and curve. In other words, the value of longitudinal acceleration Gx is an exact value of acceleration taking into account the effects of slope and curvature. Similarly, a loss of adhesion leading to distorting a measurement of acceleration that would be deduced from the rotation of the axles can here be ideally compensated.

Mainly, the device according to the invention therefore uses two accelerometers 101, 102 bi-axes fixed on the vehicle body and intended to measure a longitudinal acceleration and a lateral acceleration of the vehicle. The vehicle is subjected to three forces producing a longitudinal acceleration Gx (displacement of the vehicle subjected to the traction / braking forces), a lateral acceleration Glat (the curvature of the trajectory induces a centrifugal acceleration) and a vertical acceleration Gpes due to the gravity which is exercised in the presence of a slope (the slope of the trajectory). The first accelerometer 101 whose two axes Accl, Acc2 are located in the vertical plane Py and the second accelerometer 102 whose two axes Acc3, Acc4 are located in the horizontal plane Pz, will make it possible to measure a resultant of the accelerations (longitudinal, lateral, gravity) projected on each of the four measurement axes. The angles between the different axes of measurement of the accelerometers are known and fixed after adjustment. The computer 103 solves a system composed of four equations in order to determine four unknowns at the vehicle position Dx, namely an angle of slope Ave of trajectory, a lateral acceleration angle Ay (resulting from the centripetal force due to the speed of the vehicle. vehicle and dependent on the radius of curvature R of the trajectory as well as the offset of the accelerometer relative to the center of the vehicle), a value of the lateral acceleration Glat and the value of the longitudinal acceleration Gx. By successive integrations over the duration of the journey, the computer 103 determines the longitudinal speed Vx and the longitudinal displacement Dx of the vehicle VEH on its path for any slope and curve CURB.

If necessary, the device according to the invention is completed by a tachometer 108 to improve the previous measurement accuracy of the speed Vx and the distance traveled Dx. The tachometer 108 is fixed on one of the axles RIa, R2a, RIb, R2b of the vehicle VEH and its output signal STb is transmitted to the computer 103. The computer 103 evaluates a displacement DxT and a speed VxT from the signal (s). tachometer measurement. The computer makes a comparison between the measurement results of displacement from the tachometer and those from the accelerometers. When, for these measured values, a measurement deviation is below a threshold, the measured values are adjusted to those from the tem- perometer. In the opposite case (value greater than a threshold), there is no correction of the results coming from measurement of the accelerometers.

As represented in FIG. 1, information of zero speed Op can also be safely delivered by the calibration. culator 103 from information Im from an apparatus of the vehicle (immobilization signal, zero speed indicator, etc. ..) or be determined by the device according to the invention itself. For this determination, calculator 103 processes the information from the tachometer and accelerometers.

When the device determines a zero speed and, thanks to the peculiarities of the proposed assembly of accelerometers, the device also has the advantageous ability to implement a self-test function. This self - test function makes it possible to evaluate the necessary corrections to be made to the accelerometer measurements (after auto - calibration) and to identify operating faults of the accelerometers. The multiplicity of measurement axes provides a very advantageous redundancy of several measurements (due to the two bi-axis accelerometers) and allows periodic verification of the reliability of the accelerometers (for example at each station stop) to guarantee test measurements. (and therefore of subsequent displacement) with a very low probability of error, making them compatible with the safety requirements of a safe system as required in the railway field.

In the remainder of this description, reference is made to both FIGS. 3 and 4.

Considering the measurement axes Acc1, Acc2 of the first accelerometer 101 (see Figure 3 where, for the sake of clarity, the lateral acceleration Glat was deliberately omitted), the components of the projection measurements Gac1c, Gacc2 by addition of projections accelerations Gx, Glat, Gpes on each axis Acc1, Acc2 of the accelerometer 101 are:

- On the Accl axis

Gaccl = projection (Gx) - projection (Gpes) - projection (Glat) (1) Gac1c = Gx cos (Ay) cos (Al) + Gpas sin (Al-Ax) - Glat sin (Ay) cos (Al)

- On the axis Acc2 Gacc2 = projection (Gx) - projection (Gpes) - projection (Glat)

(2) Gacc2 = Gx cos (Ay) cos (A2) - Gp sin (A2 + Ax) - Glat sin (Ay) cos (A2)

Similarly, considering the measurement axes Acc3, Acc4 of the second accelerometer 102 (see Figure 4 where for the sake of clarity, the slope acceleration Gpes was deliberately omitted), the components of the projection measurements Gacc3, Gacc4 by adding projections accelerations Gx, Glat, Gpes on each of the axes Acc3, Acc4 of the accelerometer 102 are:

- On the Acc3 axis

Gacc3 = projection (Gx) - projection (Glat) - projection (Gpes)

(3) Gacc3 = Gx cos (A3 + Ay) - Glat sin (A3 + Ay) - Gp sin (Ax) cos (A3)

- On the Acc4 axis Gacc4 = projection (Gx) - projection (Glat) - projection (Gpes)

(4) Gacc4 = Gx cos (A4-Ay) + Glat sin (A4-Ay) - Gp sin (Ax) cos (A4)

With equations (1) to (4):

the angle Al in the plane Py between the axis X and the axis Accl

the angle A2 in the plane Py between the axis X and the axis Acc2 the angle A3 in the plane Pz between the axis X and the axis Acc3

the angle A4 in the plane Pz between the axis X and the axis Acc4

- the vehicle trajectory angle Ax in the plane Py (ie the angle between the horizontal and the X axis) - the distance Dx between the center of the vehicle and the point of attachment of the accelerometers 101, 102 on the vehicle

the angle Ay linked to the radius of curvature R in the plane Py. The angle Ay is calculated by Arctg (Lx / R), thus at first approximation Lx / R since the value of the radius of curvature R is usually higher than the offset distance Lx.

The resolution of the system formed by the four equations (1) to (4) is based on mathematical techniques which are not described here and whose purpose is to calculate the four variables Gx, Glat, Ax and Ay according to the measurements of acceleration values Gaccl, Gacc2, Gacc3, Gacc4 available to the computer 103.

However, the resolution of the system is advantageously simplified in certain particular hypotheses of arrangement of the accelerometers 101, 102.

Among these assumptions, one can choose relative angles A1 + A2, A3 + A4 each defining an orthogonal angle, that is to say: A1 + A2 = 90 ° and A3 + A4 = 90 °. Thus, the device according to the invention can provide that at least one of the relative angles A1 + A2, A3 + A4 is orthogonal.

The device according to the invention is designed in such a way that each relative angle A1 + A2, A3 + A4 is in fact subdivided (or subdivided) into a first and a second angle A1, A2 and respectively A3, A4 corresponding to angles of projection between the four axes of measurement Acc1, Acc2, Acc3, Acc4 of the first and second accelerometer 101, 102 and the first axis X (longitudinal axis according to a moving principal). supposedly rectilinear of the vehicle).

In this aspect, it is also very advantageous to choose the angles A1, A2, A3, A4 such that A1 = A2 and A3 = A4, and in particular such that A1 = A2 = A3 = A4 = 45 °.

Regarding the choice of the angles A1, A3, it is also possible to assign them adjustable values to best estimate the effects of slope or curvature without affecting the accuracy of the longitudinal acceleration measurement.

For example, if the option is chosen, for which the projection angles A1, A2; A3, A4 of each accelerometer are equal, that is to say A1 = A2 and A3 = A4, the system of previous equations becomes:

(1) Gac1c = Gx cos (Ay) cos (Al) + Gpas sin (Al-Ax) - Glat sin (Ay) cos (Al)

(2) Gacc2 = Gx cos (Ay) cos (Al) - Gpe sin (Al + Ax) - Glat sin (Ay) cos (Al) (3) Gacc3 = Gx cos (A3 + Ay) - Glat sin (A3 + Ay) - Gpes sin (Ax) cos (A3)

(4) Gacc4 = Gx cos (A3-Ay) + Glat sin (A3-Ay) - Gpe sin (Ax) cos (A3)

The resolution of this system makes it possible to easily determine the four unknowns sought and defined by the variables Gx, Glat, Ax, Ay, then by integration over a duration of displacement to deduce the longitudinal velocity Vx and the associated position Dx on the path of the vehicle: Vx = J (Gx dt) Dx = j (Vx dt) The device according to the invention thus allows the computer 103 to deliver a slope angle value Ax, of an angle Ay of lateral acceleration (that is to say representing the rotation of the lateral acceleration at the point of mounting the accelerometer assembly relative to what it would be in the center of the vehicle for the radius of curvature R) at each point of the path including slope and curve.

By extension, the computer 103 delivers a speed Vx and a position Dx at each point of the path including slope and curve by successively integrating the longitudinal acceleration value Gx of the vehicle.

As described above, the device can also include:

a tachometer 104 disposed on at least one axle of the vehicle and delivering a speed tachometer value VxT and position DxT of the vehicle,

the tachometric values VxT, DxT and the speed and position values Vx, Dx obtained and respectively delivered by the computer 103 are supplied to a comparator 106 included in the computer 103,

the comparator 106 determines differences between categories of speed values and position, and if these are below a predefined threshold, a resetting of the speed and position values Vx, Dx delivered by the computer 103 to each point of the path including slope and curve is performed on the tachometric values VxT, DxT. If the deviations are below the threshold, the registration is inhibited.

This ability to reshape exhibits an increase in speed and displacement measurement accuracy based on a simple additional measure of speed and displacement proportional to the radius of the wheel. The device according to the invention may also comprise a zero velocity detection means 107 of the vehicle being included or coupled to the computer 103 and to the tachometer 104. The latter comprises at least one correlator of the speed and position values Vx, Dx delivered by the computer 103 and corresponding tachometric values VxT, DxT.

As a result, a very safe zero velocity detection function is performed either: by taking into account information external to the device made available by one of the vehicle devices (for example by means of an immobilized vehicle internal signal, ...)

by determining a stop of the vehicle by filtering the speed and displacement information Vx, Dx delivered by the computer 103. This determination can thus be correlated with the corresponding tachometer data VxT, Dxt.

- Following these treatments, if the vehicle is really guaranteed to be stopped, the device provides information called zero speed.

A function called autotest can then advantageously uti ^¬ Liser information called zero speed. When in ^¬ formation is properly provided, it means that the vehi- cule is stationary and therefore the longitudinal and lateral accelerations are then zero.

The associated test thus consists in verifying that the measurement values delivered by the accelerometers 101, 102 satisfy the previously given system of equations (1), (2), (3), (4) which then reduces to:

(1) Gaccl = Gpes sin (Al-Ax)

(2) Gacc2 = - Gpe sin (A2 + Ax)

(3) Gacc3 = - Gpe sin (Ax) cos (A3)

(4) Gacc4 = - Gpe sin (Ax) cos (A4) An example of resolution of this system is given here in the particular hypothesis of arrangement of accelerometers, for which the projection angles A1, A2; A3, A4, are equal in pairs in each of the planes Py, Pz, that is to say that A1 = A2 and A3 = A4:

From the last two equations (3) and (4) the following relations (5) and (6) can be deduced:

(5) Gacc3 = Gacc4 (6) Sin (Ax) = - Gacc3 / (Gpes Cos (A3))

By deferring the term Sin (Ax) in the equations (1) and (2), it is then possible to check the measured values of the projected accelerations Gac1c, Gacc2 of the first accelerometer 101 with the calculation results above.

The projected accelerations Gacc3, Gacc4 of the second accelerometer 102, are verified by equation (5). As a first approximation, it is legitimate to consider that the devers has little influence on the measurement, which is generally the case, for example when parking in a garage or station stops.

In order to refine the verification of the projected accelerations Gacc3, Gacc4 of the second accelerometer 102 it is however also possible to read a value of the devers from a database.

By these verifications and by selecting a filtering threshold, it is possible to determine correction factors to be applied to the measurements resulting from the accelerometers. In the case of the second accelerometer 102, it is possible advantageously to take advantage of the slow process of drifting the accelerometers before modifying its correction factors. These correction factors will be applied following a confirmation obtained after several stops. This number of stops is table according to the precision chosen. This makes it possible to self-calibrate the device according to the invention.

A second chosen threshold higher than the first threshold can also be defined to declare the device according to the invention out of operation.

In order to perform the self-test function, the device according to the invention comprises:

a self-calibration means 105 for the accelerometers 101, 102 that can be activated if the zero speed detection means confirms a stopping of the vehicle,

the self-calibration means processing measurements from the accelerometers 101, 102 and given by an accelerations calculation unit 104 (itself receiving the measurements from the accelerometers 101, 102 and being included in the computer 103),

the self-calibration means calibrates the measurements in correspondence with zero values of the longitudinal acceleration Gx and lateral Glat of the vehicle.

The self-calibration means 105 has a first control mode for verifying the equality of the measurement values Gacc3, Gacc4 on the second accelerometer 102 and a means for re-calculating the slope angle Δx from which the values measurement Gaccl, Gacc2 of the first accelerometer 101 are verified by means of a second control mode. Thus, the verification is made very reliable and even more so if the slope angle can be evaluated and confirmed in redundancy by known information external to the device.

For this realization in relation to the autotest function described above, beyond a first error threshold derived from results of the self-calibration means 105, correction factors from the self-calibration means 105 are then forwarded to the computing unit 104 (more generally the displacement calculator 103).

Likewise, beyond a second threshold of error which is less secure than the first threshold derived from results of the auto-calibration means 105, an on-board measurement failure indicator is activated.

A simplified model for evaluating a probability of failure of the so-called self-test function can thus be achieved by considering that, at the end of the vehicle, measurements made on the accl, acc2, acc3, acc4 measurement axes Accelerometers 101, 102 are obtained in redundancy.

Suppose a time interval T between two stops of the vehicle: the probability of failure Pr of the self-test function applied to the two measurement axes Accl, Acc2 in the plane Py is defined by:

Pr = λaccl * λacc2 * T

Where the respective failure rates λac1 and λacc2 of the measuring axes Accl and Acc2 of the two-axis accelerometers are assumed to be equal to a commonly accepted value of 10 ^-5 in the following calculation example:

With T = 60 seconds, Pr = 10 ^{~ 10} * 0.017 = 1.7 * 10 ^{~ 12} With T = 10 minutes, Pr = 10 ^{~ 10} * 0.17 = 17 * 10 ^{~ 12}

It therefore appears that if the vehicle stops periodically and frequently, the device makes it possible to guarantee a level of confidence in the measured data which is required for the safety required in the railway field.

In accordance with this evaluation of a probability of failure of the so-called self-test function, the device according to the invention can then comprise a probability of failure evaluation means activatable between two stops of the vehicle and employing a redundancy measurement on the axes measurements of accelerometers. This evaluation means can be integrated into the self-calibration means 105 previously described.

Finally, the device according to the invention may also optionally comprise a vehicle adhesion loss detector (in case of slipping or skidding) coupled to at least one of the first and second accelerometers 101, 102 bi-axes for which displacement measurements can be associated with external values (slope, curvature of a databank or data of a path marker system, etc.). In case of divergence of these data, a risk of loss of adhesion of the vehicle can be detected and by extension complement the information provided by the zero speed detection system (locked wheel, but moving vehicle).

The vehicle adhesion loss detector may also, where appropriate, be coupled to at least one vehicle axle tachometer 108 in addition to one of the first and second accelerometers 101, 102 so as to compare their measurement data. angular movement and respectively longitudinal displacement. In this way, the zero speed detection function can then be made even safer.

Main abbreviations

X: longitudinal axis (displacement) of the vehicle

Y: axis perpendicular to the X axis and in the floor plan of the vehicle

Z: axis perpendicular to the vehicle floor Px: plane orthogonal to the X axis and determined by the Y, Z Py axes: plane orthogonal to the Y axis and determined by the X, Z Pz axes: plane orthogonal to the axis Z and determined by the X, Y axes Gpes: acceleration of gravity = 9.81 m / s2

Gx: longitudinal acceleration of the vehicle along the X axis

Glat: lateral acceleration of the vehicle at the point of accelerometers in the vehicle

Vx: longitudinal speed along the X axis Dx: position / longitudinal displacement along the X axis VxT: longitudinal speed given by the tachometer DxT: longitudinal displacement given by the tachometer Accl: first axis of measurement of the accelerometer 101 Acc2: second measuring axis of accelerometer 101 Acc3: first axis of measurement of accelerometer 102 Acc4: second axis 2 of measuring of accelerometer 102 Al: angle in plane Py between axis X and axis Accl A2: angle in plane Py between axis X and axis Acc2 A3: angle in plane Pz between axis X and axis Acc3 A4: angle in plane Pz between axis X and axis Acc4

Ax: vehicle trajectory angle in plane Py (ie angle between horizontal and X axis)

Lx: distance of offset between the center of the vehicle and the point of attachment of accelerometers 101, 102 Ay: angle related to the radius of curvature in the plane Py. Ay is cabled by Arctg (Lx / R), so in first approximation Lx / R

Vx: longitudinal speed of the vehicle along the X axis

Claims

claims

1. Device for measuring the movement of a self-guided vehicle (VEH) comprising on board: - an accelerometer (101) provided with two measurement axes

(Accl, Acc2) in a longitudinal plane (Py) defined by a first longitudinal axis (X) along a principal supposedly rectilinear displacement of the vehicle and a second axis (Z) perpendicular to the floor of the vehicle, - a computer (103) connected to an output signal

(Sl, S2) associated with each measurement axis (Accl, Acc2), where each output signal (Sl, S2) comprises a projection measurement (Gac1c, Gacc2) of a resultant global acceleration of the vehicle on the associated measuring axis (Accl, Acc2), characterized in that:

a second accelerometer (102) is provided with at least two measurement axes (Acc3,, Acc4) in a horizontal plane (Pz) defined by the first axis (X) and a third axis (Y) perpendicular to the first and second axis (X, Z),

the computer (103) is connected to an output signal (S3, S4) associated with each measurement axis (Acc3, Acc4), where each output signal (S3, S4) comprises a projection measurement (Gacc3, Gacc4) the resultant global acceleration of the vehicle on the associated measurement axis (Acc3, Acc4),

the measurement axes (Accl, Acc2, Acc3, Acc4) of the first and second accelerometer (101, 102) have in their respective planes (Py, Pz) a relative angle (A1 + A2, A3 + A4) being adjustable, so that the computer (103) delivers from the four projection measurements (Gac1c, Gacc2, Gacc3, Gacc4) at least one longitudinal acceleration value (Gx) of the vehicle at each point of a path comprising a slope and curve.

2. Device according to one of the preceding claims, wherein at least one of the relative angles (A1 + A2, A3 + A4) is orthogonal.

3. Device according to one of the preceding claims, wherein each relative angle (A1 + A2, A3 + A4) is subdivided into a first and a second angle (A1, A2; A3, A4) corresponding to projection angles between the four measurement axes (Accl, Acc2, Acc3, Acc4) of the first and second accelerometer (101, 102) and the first axis (X).

4. Device according to claim 3, wherein the projection angles (A1 = A2, A3 = A4) of each accelerometer are equal.

5. Device according to one of the preceding claims, wherein the computer (103) delivers at each point of the path including slope and curve a lateral acceleration value (Glat), slope angle (Ax), an acceleration angle. Lateral (Ay) resulting from the centrifugal force due to the speed of the vehicle and dependent on a radius of curvature (R) of the trajectory as well as an offset of the accelerometer relative to the center of the vehicle.

6. Device according to one of the preceding claims, for which the computer (103) delivers a speed

(Vx) and a position (Dx) at each point of the path including slope and curve by successively integrating the longitudinal acceleration value (Gx) of the vehicle.

7. Device according to one of the preceding claims, comprising: - a tachometer (104) is arranged on at least one axle of the vehicle and delivers a tachometric speed value (VxT) and position (DxT) of the vehicle,

the tachometric values (VxT, DxT) obtained and the speed and position values (Vx, Dx) delivered by the computer (103) are supplied to a comparator (106),

the comparator (106) determines the differences between categories of speed values and position, and if they are below a predefined threshold, a registration of the speed and position values (Vx, Dx) obtained by the calculator (103) at each point of the path including slope and curve is performed on the tachometric values (VxT, DxT).

8. Device according to claim 7, comprising a zero speed detection means (107) of the vehicle coupled to the computer (103) and the tachometer (104) and comprises at least one correlator of the speed and position values (Vx, Dx) delivered by the computer (103) and tachometric values (VxT, DxT).

9. Device according to claims 5 and 8, comprising:

- a means for auto-calibration (105) accelerometers (101, 102) being activatable if the zero speed detection means confirms a stop of the vehicle,

- The self-calibration means processing measurements from accelerometers 101, 102 and data by an accelerations calculation unit 104 included in the computer 103 - the self-calibration means calibrates measurements in correspondence with zero values longitudinal (Gx) and lateral (Glat) acceleration of the vehicle.

10. Device according to claim 4 and 9, for which the self-calibration means (105) has a first mode of check for checking the equality of the measured values (Gacc3, Gacc4) on the second accelerometer (102) and means for recalculating the slope angle (Ax) from which the measured values (Gac1c, Gacc2) of the first accelerometer (101) are checked by means of a second control mode.

11. Device according to one of claims 9 or 10, for which beyond a first error threshold from results of the self-calibration means, correction factors from the self-calibration means are transmitted to the calculator (103).

12. Device according to claim 11, wherein beyond a second threshold of error less secure than the first threshold from results of the self-calibration means, an on-board measurement failure indicator is activated.

13. Device according to one of claims 7 to 12, comprising a failure probability evaluation means operable between two stops of the vehicle and employing a redundancy measurement on the measurement axes of the accelerometers.

14. Apparatus according to one of the preceding claims comprising a vehicle adhesion loss detector coupled to at least one of the first and second accelerometers.

15. Device according to claim 14, wherein the vehicle adhesion loss detector is coupled to at least one tachometer in addition to one of the first and second accelerometers.