System for determining an angular speed of at least one wheel of a vehicle and corresponding method

Abstract

System and method for determining an angular speed of at least one wheel of a vehicle and corresponding method A system (200) is described for determining an angular speed of at least one wheel (W) of a vehicle, particularly a railway vehicle, comprising a rotary electric generator (202) arranged to be coupled to an axle (A) of the vehicle to which the at least one wheel (W) is coupled. The rotary electric generator (202) is arranged to generate an alternating electrical signal (Salt) at a frequency which is a function of a rotational speed of the axle. The system (200) further comprises: • - rectifier means (204) arranged to generate a rectified electrical signal (Srect) by rectifying the alternating electrical signal (Salt); • - electronic control means (206) arranged to determine the angular speed of the at least one wheel (W) as a function of a frequency or a period (T') of the rectified electrical signal (Srect).

Description

[0001] System for determining an angular speed of at least one wheel of a vehicle and corresponding method

[0002] Technical field

[0003] The present invention is generally in the field of vehicles, for example railway vehicles; in particular, the invention relates to a system for determining an angular speed of at least one wheel of a vehicle and a corresponding method.

[0004] Prior art

[0005] In the vehicle sector, rotary electric generators are, for example, used for the generation of electrical energy from the rotary motion of a wheel and / or an axle. Also known is the use of a rotary electric generator for determining the angular speed of a wheel of the vehicle.

[0006] In general, a rotary electric generator is a device arranged to be coupled to an axle of at least one vehicle to which at least one wheel is integrally coupled (in this context, the rotary electric generator is also known as an "axle generator"). By way of example, the rotary electric generator may be coupled to the axle, so that the rotation of the axle is transmitted to a rotor of the rotary electric generator.

[0007] For example, in the railway sector, two wheels may be coupled to an axle, i.e., a first wheel at a first end of the axle and a second wheel at a second end of the axle.

[0008] A rotary electric generator may, for example, be a radial flow or axial flow generator.

[0009] By way of example, as may be observed in Fig. la, a rotary electric generator 100 may comprise a conductive wire 102 wound into a coil and coupled to a rotor 104. The rotor is an el em ent / system that may rotate on itself. The coil is arranged in a magnetic field generated by a stator 106. Unlike the rotor 104, the stator 106 is a static / fixed component of the generator. The rotor 104 may be joined to the axle of the vehicle, so that the rotation of the at least one wheel integrally coupled to the axle is transmitted to the rotor of the generator so as to generate a rotation of said rotor 104.

[0010] The rotation of the coil results in a variation of the magnetic field inside the conductive wire. Therefore, an electric current is generated in the conductive wire 102. In particular, because the polarities of the coil rotate continuously, the electric current is an alternating current. The intensity produced by the rotary electric generator is therefore alternating and, for example, may vary according to a sinusoidal pattern.

[0011] In a first case, when the plane of the coil is parallel to force lines of the magnetic field, the magnetic field in the coil is zero. In a second case, when instead the plane of the coil is perpendicular to the force lines of the magnetic field, the magnetic field in the coil will be at a maximum in terms of the negative polarity or the positive polarity.

[0012] As may be seen in Fig. lb, the alternating current Iait generates a corresponding alternating voltage signal Vait.

[0013] On the basis of the period T of the alternating voltage or alternating current signal, it is possible to determine the rotational speed of the at least one wheel and, with the radius of the at least one wheel being known, it is also possible to determine the linear forward speed of the vehicle.

[0014] Disadvantageously, when the vehicle is moving forward at a low linear forward speed, the alternating voltage or alternating current signal will have an extremely long period T, from which it is not possible to determine the angular speed of said at least one wheel of a vehicle accurately (and in real time). Therefore, the estimate of the angular speed of said at least one wheel of a vehicle turns out to be unreliable.

[0015] Consequently, the estimated linear speed of the vehicle will not be reliable either.

[0016] Summary of the invention One object of the present invention is to provide solutions that make it possible to determine a reliable angular speed of at least one wheel of a vehicle, even at vehicle forward speeds that are lower than in the prior art. The aforesaid and other objects and advantages are achieved, according to a second aspect of the invention, by a system for determining the angular speed of at least one wheel of a vehicle having the features defined in claim 1 and, according to a further aspect of the invention, by a method for determining the angular speed of at least one wheel of a vehicle having the features defined in claim 7. Preferred embodiments of the invention are defined in the dependent claims, the content of which is to be understood as an integral part of the present description.

[0017] Brief description of the drawings

[0018] The functional and structural features of some preferred embodiments of a system for determining the angular of at least one wheel of a vehicle and a corresponding method according to the invention will now be described. Reference is made to the accompanying drawings, in which:

[0019] - Fig. la shows an example of a rotary electric generator according to the prior art;

[0020] - Fig. lb shows a current signal and a corresponding voltage signal, generated by a rotary electric generator according to the prior art;

[0021] - Fig. 2 shows an embodiment of a system for determining the angular speed of at least one wheel of a vehicle according to the present invention;

[0022] - Fig. 3 shows an exemplary alternating electrical signal;

[0023] - Fig. 4 shows a rectified electrical signal obtained by rectifying the alternating electrical signal of Fig. 3; and

[0024] - Fig. 5 shows a square wave signal obtained from the rectified electrical signal of Fig. 4.

[0025] Detailed description

[0026] Before explaining in detail a plurality of embodiments of the invention, it should be clarified that the invention is not limited in the application thereof to the design details and configuration of the components presented in the following description or shown in the drawings. The invention may assume other embodiments and be implemented or constructed in practice in different ways. It should also be understood that the phraseology and terminology have a descriptive purpose and should not be construed as limiting. The use of “include” and “comprise” and the variations thereof are intended to cover the elements set out below and the equivalents thereof, as well as additional elements and the equivalents thereof.

[0027] A first embodiment of a system for determining the angular speed of at least one wheel of a vehicle, in particular a railway vehicle, is described below.

[0028] As may be seen in Fig. 2, the system 200 for determining the angular speed of at least one wheel of a vehicle comprises a rotary electric generator 202 arranged to be coupled to an axle A of the vehicle. As may be seen in this figure, the at least one wheel W is coupled to the axle A.

[0029] For example, the rotary electric generator may be of a radial flow or axial flow type.

[0030] As already discussed for the prior art, the rotary electric generator may be coupled to the axle, so that the rotation of the axle is transmitted to a rotor of the rotary electric generator.

[0031] As may be seen in Fig. 3, the rotary electric generator 202 is arranged to generate an alternating electrical signal Sait- The frequency of the alternating electrical signal is a function of a rotational speed of the axle A.

[0032] The system for determining the angular speed of said at least one wheel of the vehicle further comprises rectifier means 204 arranged to generate a rectified electrical signal Srect by rectifying said alternating electrical signal Sait-

[0033] A rectified electrical signal Srect obtained from the alternating electrical signal Sait of Fig. 3 is shown by way of example in Fig. 4.

[0034] For example, "rectification" of a signal may mean transforming an alternating signal into a unidirectional one (always positive or always negative).

[0035] The system for determining the angular speed of said at least one wheel of the vehicle further comprises electronic control means 206 arranged to determine the angular speed of said at least one wheel W as a function of a frequency or a period T of the rectified electrical signal Srect-

[0036] For example, when considering the frequency of the rectified electrical signal, the following formula may be used:

[0037] Vang=7t*f where Vangis the angular speed of said at least one wheel W and f is the frequency of the rectified electrical signal Srect.

[0038] For example, when considering the period, the following formula may be used:

[0039] V ang=7t / T where Vang is the angular speed of said at least one wheel W and T’ is the period of the rectified electrical signal Srect.

[0040] As may be derived from Fig. 4, the period of the rectified signal T’ is half of the period T of the alternating electrical signal shown for example in Fig. lb and Fig. 3. Similarly, the frequency of the rectified electrical signal is twice the alternating electrical signal. Advantageously, the fact that the period of the rectified signal T’ is half of the period T (and that the frequency of the rectified electrical signal is twice the alternating electrical signal) causes the resolution of the angular speed measurement to be substantially doubled. In this way, it is possible to obtain an estimate of the angular speed of the wheel even at lower speeds than the solutions of the prior art. For example, this solution may also be applied to vehicle forward speeds of less than 2 km / h. Preferably, the electronic control means 206 may be or comprise at least one of: a processor, a microprocessor, a controller, a microcontroller, an FPGA, a PLC, or the like.

[0041] Preferably, the electronic control means 206 may also be arranged to determine a linear forward speed of the vehicle as a function of the determined angular speed of said at least one wheel and a radius of said at least one wheel.

[0042] For example, the following formula may be used:

[0043] Vlin=Vang *f where Viin is the linear forward speed, Vangis the angular speed of said at least one wheel and r is the radius of the at least one wheel.

[0044] Preferably, the electronic control means, for determining the angular speed of said at least one wheel, may be arranged to:

[0045] - converting said rectified electrical signal into a corresponding square wave signal Sswi

[0046] - determining said frequency or said period of the rectified electrical signal based on the obtained square wave signal Ssw.

[0047] An exemplary square wave signal Ssw, derived from the rectified electrical signal of Fig. 4, is shown by way of example in Fig. 5.

[0048] Preferably, the electronic control means for converting the rectified electrical signal into the corresponding square wave signal may be arranged to:

[0049] - assign a first value to the square wave signal when the rectified electrical signal has a value that is greater than a predetermined threshold th;

[0050] - assign a second value, different from said first value, to the square wave signal when the rectified electrical signal has a value that is lower than said predetermined threshold th. For example, the predetermined threshold th may have a value corresponding to half of a peak value of the alternating electrical signal.

[0051] Preferably, the rectifier means may comprise at least one of:

[0052] - a Graetz bridge;

[0053] - a double half-wave rectifier.

[0054] Preferably, the alternating electrical signal may be a current signal Iait or a voltage signal Vait. For example, in Fig. 3, 4 and 5 the electrical signals shown are voltage signals. However, when described and shown, it may also apply similarly to cases in which the electrical signals are current signals.

[0055] In a further aspect, the present invention also relates to a method for determining the angular speed of at least one wheel of a vehicle, particularly a railway vehicle.

[0056] The method comprises the steps of: a) coupling a rotary electric generator to an axle of said vehicle to which said at least one wheel is coupled, wherein said rotary electric generator is arranged to generate an alternating electrical signal at a frequency which is a function of a rotational speed of said axle; b) generating a rectified electrical signal by rectifying said alternating electrical signal; c) determining the angular speed of said at least one wheel as a function of a frequency or a period of said rectified electrical signal.

[0057] Preferably, the method may further comprise the step of: d) determining a linear forward speed of the vehicle as a function of the determined angular speed of the at least one wheel and of a radius of the at least one wheel.

[0058] Preferably, step c) may also comprise: c’) converting the rectified electrical signal into a corresponding square wave signal Ssw; c”) determining the frequency or period of the rectified electrical signal on the basis of the obtained square wave signal Ssw.

[0059] Preferably, step c’) may comprise:

[0060] - assigning a first value to the square wave signal Sswwhen the rectified electrical signal has a value that is greater than a predetermined threshold;

[0061] - assigning a second value, different from said first value, to the square wave signal Ssw when the rectified electrical signal has a value that is lower than said predetermined threshold.

[0062] For example, in the present disclosure, the vehicle may be a railway vehicle or a railway convoy comprising a plurality of railway vehicles. For example, a vehicle may be a locomotive or a wagon, and a route / section may comprise rails (rolling surfaces) on which the wheels of the locomotive roll. However, the embodiments described herein are not intended to be limited to vehicles on tracks. For example, the vehicle may be a car, a truck (for example a highway semi-trailer truck, a mining truck, a truck for transporting timber or the like), or the like, and the route may be a road or a trail.

[0063] The advantage achieved is therefore that of having provided solutions that make it possible to determine an angular speed of at least one wheel of a vehicle that is reliable, even at vehicle forward speeds that are lower than in the prior art.

[0064] Various aspects and embodiments of a system for determining the angular speed of at least one wheel of a vehicle and a corresponding method according to the invention have been described. It is understood that each embodiment may be combined with any other embodiment. Moreover, the invention is not limited to the embodiments described, but may be varied within the scope defined by the appended claims.

Claims

CLAIMS1. System (200) for determining an angular speed of at least one wheel (W) of a vehicle, particularly a railway vehicle, comprising a rotary electric generator (202) arranged to be coupled to an axle (A) of said vehicle to which said at least one wheel (W) is coupled; said rotary electric generator (202) being arranged to generate an alternating electrical signal (Sait) at a frequency which is a function of a rotational speed of said axle; said system (200) for determining the angular speed of said at least one wheel of the vehicle further comprising:- rectifier means (204) arranged to generate a rectified electrical signal (Srect) by rectification of said alternating electrical signal (Sait);- electronic control means (206) arranged to determine the angular speed of said at least one wheel (W) as a function of a frequency or period (T1) of said rectified electrical signal (Srect).

2. System (200) according to claim 1, wherein said electronic control means (206) are further arranged to determine a linear vehicle forward speed as a function of said determined angular speed of said at least one wheel and a radius of said at least one wheel.

3. System (200) according to claim 1 or 2, wherein said electronic control means (206), for determining the angular speed of said at least one wheel (W), are arranged to:- convert said rectified electrical signal (Srect) into a corresponding square wave signal (Ssw);- determine said frequency or said period of the rectified electrical signal (Srect) on the basis of the obtained square wave signal (Ssw).

4. System (200) according to claim 3, wherein said electronic control means for converting said rectified electrical signal (Srect) into the corresponding square wave signal (S sw ) are arranged to:- assign a first value to the square wave signal when said rectified electrical signal has a value that is greater than a predetermined threshold (th);- assign a second value, different from said first value, to the square wave signalwhen said rectified electrical signal has a value that is lower than said predetermined threshold (th).

5. System according to any of the preceding claims, wherein said rectifier means (204) comprises at least one of- a Graetz bridge;- a double half-wave rectifier.

6. System according to any of the preceding claims, wherein said alternating electrical signal (Sait) is a current signal or a voltage signal.

7. Method for determining angular speed of at least one wheel of a vehicle, particularly a railway vehicle, comprising the steps of a) coupling a rotary electric generator (202) to an axle (A) of said vehicle to which said at least one wheel (W) is coupled, wherein said rotary electric generator (202) is arranged to generate an alternating electrical signal (Sait) at a frequency which is a function of a rotational speed of said axle; b) generating a rectified electrical signal (Srect) by rectification of said alternating electrical signal (Sait); c) determining the angular speed of said at least one wheel as a function of a frequency or period of said rectified electrical signal.

8. Method according to claim 7, further comprising the step of d) determining a linear vehicle forward speed as a function of said determined angular speed of said at least one wheel and a radius of said at least one wheel.

9. Method according to claim 7 or 8, wherein step c) comprises: c') converting said rectified electrical signal (Srect) into a corresponding square wave signal (Ssw); c") determining said frequency or said period of the rectified electrical signal (Srect) on the basis of the obtained square wave signal (Ssw).

10. Method according to claim 9, wherein step c') comprises:- assigning a first value to the square wave signal when said rectified electrical signal has a value that is greater than a predetermined threshold (th);- assigning a second value, different from said first value, to the square wave signal when said rectified electrical signal presents a value that is lower than said predetermined threshold (th).

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