Technical field

The present invention relates, in general, to the field of systems and sensors for monitoring the angular speed of an axle of a railway vehicle; in particular, the invention relates to a system for determining an angular speed of an axle of a railway vehicle and to a correspond- ing method.

Background art

In known systems and methods that are usually used on board trains, to measure angular speed w of an axle, the presence of at least one toothed phonic wheel is usually provided integral with the axle, and the presence of a sensor adapted to detect the passage frequency of the phonic wheel teeth in front of the sensor (speed sensor).

The time interval between the passage of two consecutive teeth in front of the sensor may be referred to as "tooth period" (Ttooth). The number of teeth that make up the phonic wheel may be referred to as nteeth.

By multiplying Ttooth and Nteeth, the period of rotation of the phonic wheel is obtained, that is the period of rotation of the axle and wheels.

Twheel ⁼ Ttooth * nteeth

The angular speed w of the wheel is calculated starting from its rotation period by the fol- lowing relation.

Disadvantageously, such systems require dedicated (ad hoc) components used exclusively for the purpose of detecting the angular speed of the axle. These components provide a phonic wheel, a sensor, electronics and acquisition software, a series of electrical wiring shielded from electromagnetic noise (noise that can distort the sensor's frequency measure- ment). This components are used for the sole purpose of detecting the angular speed of the axle with the consequent drawbacks in terms of costs and installation times.

Moreover, it is prior art to install one or more strain gauges (in various configurations, for example, full Wheatstone bridge, "half bridge" or "quarter bridge") on the axle and/or wheel of a railway vehicle to estimate the contact forces between the wheels and the rail, starting from the deformation of the axle.

Currently, the estimate of the wheel-rail contact forces has as its sole main objective the monitoring of the infrastructure and rolling stock and the relative scheduling of maintenance and/or correction interventions (as illustrated in the block diagram in figure 4).

At present, therefore, known systems and processes that provide for the installation of one or more strain gauges on the axle and/or wheel of a railway vehicle do not provide for the possibility of using the measurements made by means of said one or more strain gauges to determine the angular speed of the axle and, consequently, the translational speed of the vehicle.

Summary of the invention

An object of the present invention is therefore to allow a measurement of the angular speed of an axle and, consequently, the calculation of the translational speed of the vehicle without the use of dedicated additional angular speed sensors.

To obtain this result, a system for determining the angular speed of a railway vehicle axle is proposed.

This system comprises a deformation detection circuit coupled to an axle of the railway ve- hicle. The deformation detection circuit is provided for detecting the trend over time of a value of flexural deformation of the axle due to a value of normal load exerted by the axle on the rail. The system for determining an angular speed value further comprises a control means ar- ranged for estimating the angular speed of the axle as a function of a frequency derived from the time trend of the flexural deformation value of the axle which is detected by the defor- mation detection circuit.

The above and other objects and advantages are achieved, according to an aspect of the in- vention, by a system for determining an angular speed of a railway vehicle axle having the features defined in claim 1 and by a method for determining an angular speed of an axle of a railway vehicle having the features defined in claim 8. Preferred embodiments of the in- vention are defined in the dependent claims.

Brief description of the drawings The functional and structural features of some preferred embodiments of a system and a method for determining the angular speed of an axle of a railway vehicle according to the invention will now be described. Reference will be made to the accompanying drawings, in which:

- figure 1 illustrates an axis of a railway vehicle to which a deformation detection circuit is coupled;

- figure 2 illustrates by way of example the signal generated by the deformation de- tection circuit subjected to a flexural deformation, during the movement of the train;

- figure 3A illustrates by way of example the case in which the deformation detection circuit is located on the lower surface of the axle (lower part) and the load force produces an elongation deformation;

- figure 3B illustrates by way of example the case in which the deformation detection circuit is located on the upper surface of the axle (upper part) and the load force produces a compression deformation; and

- figure 4 illustrates a block diagram illustrating the steps usually performed by the systems implemented according to the prior art.

Detailed description Before explaining a plurality of embodiments of the invention in detail, it should be noted that the invention is not limited in its application to the construction details and to the con- figuration of the components presented in the following description or shown in the draw- ings. The invention can take other embodiments and be implemented or practically carried out in different ways. It should also be understood that the phraseology and terminology are for descriptive purpose and are not to be construed as limiting. The use of "include" and "comprise" and variations thereof are intended as including the elements cited thereafter and their equivalents, as well as additional elements and equivalents thereof.

Furthermore, throughout the present disclosure and in the claims, the terms and expressions indicating positions and orientations, such as "longitudinal", "transverse", "vertical" or "hor- izontal", refer to the travel direction of the train. With reference initially to figure 1, an axle of a railway vehicle is illustrated by way of example to which a deformation detection circuit 10 is coupled, belonging to the system for determining an angular speed of a railway vehicle according to the invention.

In a first embodiment of the invention, the system for determining an angular speed V _® of an axle of a railway vehicle comprises a deformation detection circuit 10 coupled to an axle 1 of the railway vehicle.

The deformation detection circuit 10 is coupled to an axle 1 of the railway vehicle and is provided for detecting the trend over time of a value of flexural deformation of the axle 1 which is due to a value of normal load exerted by the axle on the rail.

The system for determining an angular speed Vro of a railway vehicle further comprises a control means provided for estimating an angular speed value V _w of the axle as a function of a frequency f derived from the trend over time of the value of flexural deformation of the axle 1 detected by the deformation detection circuit 10. Starting from the fact that two wheels having a radius R are coupled to the axle 1 and said control means may be further arranged to convert said value of angular speed V _M of the axle into a value of tangential speed Vtang of the railway vehicle according to the radius of the wheels R.

The formula used to estimate the angular speed n _w of the axle as a function of the frequency f derived from the trend over time of the value of flexural deformation of the axle 1 detected by the deformation detection circuit 10 may for example be the following:

V _« , = 2* p * f

The formula used to convert said angular speed value of the axle V _a> into a tangential velocity value V _tang may be for example the following:

Vtang = n _w * Radius of the wheel

The control means may be arranged, for example, locally in proximity to the or directly in the deformation detection circuit 10. Alternatively, the control means may be arranged re- motely with respect to the deformation detection circuit 10 in other control units on board the vehicle or in remote control stations with respect to the railway vehicle. Therefore, the control means can receive the data from the deformation detection circuit 10 either through a specific wiring or via a wireless connection.

The control means may be, for example, but not necessarily, a control unit, a processor or a microcontroller.

With reference to figure 2, starting from the signal generated by the deformation detection circuit 10 when subjected to a flexural deformation, during the movement of the railway vehicle, the system for determining an angular speed V _m of an axle of a railway vehicle may be able to estimate the tangential speed V _t a _ng of the vehicle.

The deformation detection circuit 10 may comprise at least one strain gauge sensor means and/or at least one piezoelectric sensor means. The strain gauge sensor or the piezoelectric sensor means may be arranged parallel to the axle 1.

The strain gauge sensors and/or the piezoelectric sensor means may also be more than one, so as to increase the accuracy of the measurement.

;

With the vehicle stationary, the flexural deformation of the axle is correlated with the static load of the vehicle on the axle itself.

Referring to figures 3 A and 3B, in the case where the deformation detection circuit 10 is located on the upper surface of the axle 1 (upper part), the load force produces a compression deformation. In the case in which the deformation detection circuit 10 is located on the lower surface of the axle (lower part), the load force produces an elongation deformation.

When the railway vehicle is moving, the rotation of the axle 1 will cause the deformation detection circuit 10, which is permanently associated with said axle 1, to cyclically switch from being on the upper surface of the axle (upper part) on the lower surface of the axle (lower part).

Then, during the travel of the railway vehicle, the output signal from the deformation detec- tion circuit 10 (attributable to a vertical force, F _vert ) will be of a sinusoidal type with mean value equal to zero, frequency f equal to the rotation frequency of the vehicle axle and am- plitude proportional to the flexural stresses to which the axle is subjected ("jolts").

As illustrated in figure 2, T is an example of a period of the output signal from the defor- mation detection circuit 10. The frequency f will correspond to the reciprocal of the period T. This period T varies according to the speed of the railway vehicle.

The frequency f of the output signal from the deformation detection circuit 10, indicative of the time trend of the flexural deformation value of the axle 1 , is the frequency f which can be used to estimate an angular speed value V _fu of the axle. An elaboration of this signal can be used to estimate the angular speed Y _m of the axle and therefore, known the radius of the wheel, of the tangential speed V _t a _ng of the railway vehicle.

In other words, the control means may be arranged to determine the tangential speed Vtang of the railway vehicle according to the frequency f derived from the time trend of the flexural deformation value of the axle 1 detected by the deformation detection circuit 10 and of the wheel radius R.

The present invention also relates to a method for determining an angular speed V _® of an axle of a railway vehicle which comprises the steps of:

- detecting the trend over time of a value of flexural deformation of the axle 1 due to a value of normal load exerted by the axle on the rail;

- estimating a value of angular speed V _rt of the axle as a function of a frequency f derived from the trend over time of the detected value of flexural deformation of the axle 1.

Furthermore, starting from the assumption that on the axle 1 two wheels having a radius R are coupled, the process for determining an angular speed _w of an axle of a railway vehicle may further comprise the step of:

- converting said value of angular speed n _w of the axle into a value of tangential speed Vtang of the railway vehicle as a function of the radius of the wheels R.

Also with regard to the process for determining the angular speed of an axle of a railway vehicle, the formula used to estimate an angular speed value V^ of the axle as a function of a frequency f derived from the trend over time of a value of flexion deformation of the axle 1 detected by the deformation detection circuit 10 and the formula used to convert said an- gular speed value V _fu of the axle into a tangential speed value V _t ang may be for example those described above for the system for the determination of an angular speed of an axle of a railway vehicle.

The advantage achieved is that of allowing, through the use of a deformation detection cir- cuit, an estimate of the angular speed of an axle of a railway vehicle starting from flexural deformations of the axle. Various aspects and embodiments of a system for determining an angular speed V _® of an axle of a railway vehicle, and of a method for determining an angular speed n _w of an axle of a railway vehicle have been described, for a railway vehicle according to the invention. It is understood that each embodiment may be combined with any other embodiment. The inven- tion, moreover, is not limited to the described embodiments, but may be varied within the scope defined by the appended claims.