Signal processing method, sensor and use of sensor for determining rotational speed and / or rotational position of a wheel of a railway vehicle

Abstract

The present invention relates to a method for processing a signal and to a sensor (S), the sensor (S) comprising: a first winding (1) provided on a wheel (W), the first winding (1) being capable of having any angle (θ) relative to a reference position (R); a second winding (2) and a third winding (3), wherein the directions of the second winding (2) and the third winding (3) are not parallel; and a signal generating and processing unit (8) adapted to provide an AC voltage to the first winding (1) and to receive a first induced voltage (Vs) in the second winding (2) and a second induced voltage (Vs) in the third winding (2). Such a system can measure wheel speed / position very accurately.

Description

[Technical Field]

[0001] The present invention relates to a diagnostic system for rail vehicles that provides fast and robust wheel speed and position calculations.

[0002] In particular applications on rail vehicles, wheel speed and wheel position must be determined very accurately.

[0003] From the prior art, EP 3963617 A1 is known.

[0004] The system includes a motor for driving a drive shaft and a feedback system configured to determine at least one new value related to the accuracy of the drive shaft and generate a feedback signal based on the at least one value. A controller is configured to affect operation of the motor based on the feedback signal. The motor can be used in a variety of applications.

[0005] For example, in wheel slip protection systems for trains containing a single vehicle, systems using pole-wheel-based encoders have performed well in accordance with the EN standard. However, such pole-wheel-based encoders have certain limitations.

[0006] First, such systems do not detect the direction of rotation, which can lead to challenges in obtaining directional information for certain applications.

[0007] Furthermore, signal quality may depend on the actual speed of the train. Below 3 km / h, vehicle speed signals may be unreliable or even unavailable. However, such information must be available for precision stopping performed by braking, especially for metro stations with doors on the platforms.

[0008] Furthermore, if the latency of signal processing is too large, rapid interventions (e.g., targeted use of microslip or keeping the slip value at the maximum for adhesion growth) cannot be used. However, shorter latency is desirable, resulting in more precise control and more reproducible braking distances.

[0009] Furthermore, when a train starts from a standstill, torque control can become very difficult due to wheel slip. However, such applications can also benefit from better latency performance.

[0010] In recent developments, electromechanical actuators are becoming more common, for example they do not require an air supply to be operable.

[0011] Furthermore, electromechanical actuators also offer shorter actuation latency. The total latency of the braking system (speed detection, signal processing, control decision, actuation) can be significantly reduced. However, the limiting factor is the speed sensor.

[0012] Also, automatic train operation, which is becoming more common, has very strict requirements regarding stopping positions. Such automatic train operation requires high quality speed signals for slow moving wheels. As an example with numerical parameters of the current design, a deceleration of 0.8 m / s 2 and if the starting speed is 1 m / s, the path length traveled by the train may be 0.62 m (this is a typical specification).

[0013] If stopping is controlled by only one brake unit, a certain distance (until stopping) is traveled by the train in actual blind mode. This is the main drawback of precision stopping by brakes alone. In the current state of the art, one possible implementation of precision stopping is the combined use of the train's traction and braking systems. The brake system can be commanded to use a certain amount of braking force interaction, which is used for precise control in the final position, and the traction force is controlled to achieve the desired stopping position, but in such a case, the wear on the brake system can be significant and a lot of energy can be consumed.

[0014] Therefore, the objective technical problem to be solved by the present invention is to provide a signal processing method and a sensor that can accurately measure the rotational speed and / or rotational position of wheels, in particular wheels of train vehicles.

[0015] The targeted technical problem is solved by a signal processing method according to claim 1, a sensor according to claim 10 and a braking system according to claim 16. Furthermore, a preferred use of the sensor is described in claim 17.

[0016] Further advantageous embodiments of the invention are the subject of the dependent claims.

[0017] In particular, a signal processing method for determining the angular position of a wheel of a railway vehicle, comprising: a) exciting a first winding with an AC voltage, the first winding being provided on the wheel, and the first winding may include any angle with respect to a reference position; b) measuring the first induced voltage in the second winding and providing the induced voltage to a signal generating and processing unit; c) measuring a second induced voltage in the third winding and providing the induced voltage to a signal generating and processing unit; d) determining the rotation angle of the wheels in the signal generation and processing unit; e) calculating the rotational speed and / or rotational position of the wheels.

[0018] The central axes of the second and third windings are not parallel so that two different induced voltages can be measured.

[0019] The second and third windings are positioned next to the wheel.

[0020] Such a system allows for highly accurate wheel positioning, significantly improving train braking performance and enabling real-time online track diagnostics. When the central axes of the second and third windings are orthogonal, the first induced voltage provides a sine signal, and the second induced voltage provides a cosine signal, making it very easy to calculate the wheel's rotational speed and position. The induced voltages in the first and second windings are equal to the reference voltage (induced voltage) multiplied by the sine or cosine of the wheel's angle from a fixed reference point. The sensor provides two voltages, the ratio of which represents the absolute position of the input shaft (sinθ / cosθ=tanθ, where θ is the shaft angle). The advantage of the sine / cosine ratio is that the shaft angle is absolute. Even if the shaft rotates during a power loss, the resolver can report its new position value when power is restored.

[0021] Furthermore, such applications offer low latency, which means that low-latency electromechanical brake actuators are a prerequisite for precision stopping, which is achieved solely by the braking system. The repeatability of braking distances is improved by a low-latency closed-loop control system driven by the absolute vehicle position. Lower performance or lower parameter stability of brake pad and disc materials can be compensated for, allowing cheaper materials to achieve the same braking performance.

[0022] Furthermore, the higher time resolution and short latency of wheel speed / position sensors enable track diagnostics without affecting the vehicle's braking distance. Adhesion curves (coefficient of friction between the wheels and rails as a function of wheel slip) can be measured or derived during operational or test braking. Test braking can be initiated by the driver. The measured adhesion curve can be reported to the operator, who can then determine whether track cleaning is necessary. During operational braking, artificial wheel slip events can be generated to record the wheel rotational speed profile and derive the adhesion curve. The sensor configuration according to the present invention can even be installed as an add-on feature to existing magnetic pole wheel-based encoders.

[0023] The signals generated by the sensor configuration according to the invention can be compared in real time with the signals of the pole wheel sensors, so that new technologies can be validated in real time without retrofitting and affecting vehicle safety. The signals of the sensor configuration according to the invention are advantageously used in a limited number of specific applications, in particular precision stopping and adhesion measurement. Also, speed information below 3 km / h can be made available, which frequently occurs when system braking occurs.

[0024] The sensor is preferably a resolver. Resolvers are a very specialized sensor type and are widely used in a variety of applications, especially when environmental conditions are harsh. Resolvers are very robust sensors and can provide precise angular position with milliradian resolution. Depending on the signal processing algorithm, the sensor output can be rotational speed and / or rotational position. A precise output can be beneficial for precision stopping functions, as an angular resolution of 3.2 MRAD is required for a wheel radius of 0.5 m to achieve a position resolution of 1 cm.

[0025] Preferably, the excitation current is provided by the signal generating and processing unit, filtered by the first filter and supplied to the first winding in step a).

[0026] The filter has the function of high voltage protection of the signal generation and processing unit. The filter block can also implement band-pass filtering to remove any DC offset from the measured or generated signal.

[0027] Therefore, the first induced voltage may also be filtered by a second filter before being supplied to the signal generating and processing unit, and similarly for the second induced voltage, which is filtered by a third filter before being supplied to the signal generating and processing unit.

[0028] Preferably, the excitation of the first winding with an AC voltage is performed at two or more frequencies, which makes the overall sampling more robust.

[0029] More preferably, the excitation of the first winding with AC voltage is performed at two or more frequencies to estimate the axle or wheel speed / position, and at another number of frequencies to explore a less noisy frequency range, which also results in a very robust signal processing.

[0030] Preferably, the sampling frequency of the evaluation of the first and second induced voltages is approximately twice the excitation frequency of the excitation current, thus avoiding the influence of leakage on the FFT algorithm used by the signal generation and processing unit. This allows for precise synchronization of the excitation for sampling.

[0031] Preferably, the evaluation algorithm is a correlation search after Fourier transformation of the first, second and third winding channels, thus allowing the use of the frequency range with the lowest external noise disturbance.

[0032] A degraded mode is also possible, further improving safety: if a section of the wire breaks, the signal processing method can switch to single-component mode. Position and velocity can be sampled using one channel, meaning only the second or third winding. If the excitation wire (first winding) breaks, the coupling between the first and second winding channels can be used to estimate axial position or velocity in a degraded mode with lower performance.

[0033] Preferably, the signal processing method comprises the following two further steps: f) performing wheel braking; g) measuring the overall vehicle speed and calculating wheel slip based on the wheel rotational speed and the overall vehicle speed.

[0034] Here, the slip behavior of the wheels can be determined and adhesion curves (coefficient of friction between the wheels and the track as a function of wheel slip) can be measured or derived during operational braking or testing.

[0035] Preferably, the central axes of the second and third windings are essentially perpendicular, preferably orthogonal. This configuration makes signal generation very robust. Therefore, angle calculations are performed using the projection of a rotating vector. If the components are not perpendicular, the calculation can still be performed, but performance will be predictably poor.

[0036] Preferably, the coil testing unit communicates with the signal generating and processing unit via protected data lines and transfers diagnostic information, which is used to select appropriate signal processing depending on the availability of the first winding, the second winding and / or the third winding.

[0037] If one of the windings breaks, the signal generation and processing unit can perform signal processing by an alternative method that does not require the broken winding.

[0038] Such alternative signal processing may be less accurate, but can avoid complete failure of wheel speed and position detection, which is advantageous with regard to safety issues, especially when used in braking systems.

[0039] More preferably, the signal generation and processing unit provides quality parameter output signals describing the reliability of the position and velocity signals in real time, which is a further advantage with regard to safety issues.

[0040] The sensor according to the present invention comprises: a first winding provided on the wheel, the first winding being capable of having any angle relative to a reference position; a second winding and a third winding, the directions of the second winding and the third winding being non-parallel; and a signal generating and processing unit adapted to provide an AC voltage to the first winding and to receive the first induced voltage in the second winding and the second induced voltage in the third winding.

[0041] Preferably, a rotary transformer is provided between the signal generating and processing unit and the first winding. The rotary transformer is a functional unit for transferring the excitation signal from the stationary part to a rotating excitation coil attached to the sensor axle. This provides greater accuracy compared to, for example, carbon brushes, as it does not have abrasive effects.

[0042] Preferably, a first filter is provided between the signal generating and processing unit and the first winding. More preferably, a second filter is provided between the signal generating and processing unit and the second winding, and / or a third filter is provided between the signal generating and processing unit and the third winding. These filters have the advantage that the signal generating and processing unit can protect against higher overvoltage overloads and can also implement different signal filtering features by passing only frequencies used by the system to excite the sensor. The greatest disturbance to the sensor signal and processing unit is EMC signals from the train or from a higher-voltage power supply of another train passing on a parallel track. The sensor configuration of the present invention performs filtering to ensure that only values ​​related to the observed wheel are used, thereby providing a safety-related function for the brake system.

[0043] Preferably, the first filter, the second filter and / or the third filter are adapted to implement band-pass filtering to remove any DC offset from the measured or generated signal, which makes the measurement more robust.

[0044] Preferably, a wire and coil inspection unit is provided and adapted to inspect whether the wire or winding is broken. If the wire of the second winding and / or the third winding is broken, the signal generating and processing unit can switch to a single secondary winding-based signal processing method. If the first winding is broken, one of the second winding or the third winding is used to provide the excitation signal, and the signal processing unit switches to a different signal processing method to obtain speed and position information.

[0045] A braking system for a railway vehicle according to the present invention comprises the sensor arrangement described above.

[0046] A preferred use of the sensor according to the invention is for determining the rotational speed and / or rotational position of a wheel of a railway vehicle, and also for determining wheel slip of a wheel of a railway vehicle.

[0047] Preferred embodiments of the present invention are illustrated by the accompanying drawings. [Brief explanation of the drawings]

[0048] [Figure 1] 1 shows a schematic diagram of a sensor according to one embodiment of the present invention; [Figure 2] 1 shows a schematic diagram of a sensor according to another embodiment of the present invention;

[0049] 1 shows a basic embodiment of the present invention, in which a first winding 1 is provided on a wheel W (not shown here) of a railway vehicle, and this first winding 1 is connected via a fifth terminal R1 and a sixth terminal R2 to a first filter 5, which is connected to a signal generating and processing unit 8. A rotary transformer 4 is provided between the first winding 1 and the fifth and sixth terminals R1 and R2.

[0050] Furthermore, a second winding 2 is provided on the outside of the wheel, by means of which the sine signal can be measured (Vs=Vr×sinθ), and a third winding 3 is provided for measuring the cosine signal (Vc=Vr×cosθ). The second winding 2 is connected at its first terminal S1 and its third terminal S3 to a third filter S3, which is again connected to the signal generating and processing unit 8. The third winding 3 is also provided with second and fourth terminals S2 and S4 to a second filter 6, which is also connected to the signal generating and processing unit 8.

[0051] Therefore, separate filters 5, 6, 7 are used for each winding 1, 2, 3. The signal generation and processing unit 8 is the main signal processing unit. It has separate outputs for each winding: the first winding 1 is the reference winding, the second winding 2 is the sine winding, and the third winding 3 is the cosine winding.

[0052] A second embodiment is shown in Figure 2, where a wire and coil inspection unit 9 is provided. The wire and coil inspection unit 9 is a completely separate electronic component that inspects the wires of the first winding 1, the second winding 2 and the third winding 3 to ensure they are not broken.

[0053] For this purpose, the wire and coil inspection unit 9 uses a small DC current. A first filter 1, a second filter 2 and a third winding 3 separate the signal generation and processing unit 8 from the wire and coil inspection unit 9.

[0054] However, the wire and coil inspection unit 9 may inform the wire and coil inspection unit 9 which line is broken.

[0055] If one or more of the wires of one winding (first winding 1, second winding 2, and / or third winding 3) breaks, the signal generating and processing unit 8 can still operate in a degraded mode. Some speed and position information can still be extracted by ignoring the signals from the broken wires (first winding 1, second winding 2, and / or third winding 3).

[0056] If the wire of the excitation winding (second winding 2 and / or third winding 3) is cut, the wire and coil inspection unit 9 can switch one of the second winding 2 or third winding 3 to the excitation channel (first winding 1) and switch to a different signal processing method to obtain speed and position information.

[0057] The present invention is not limited to the above embodiment.

[0058] More windings can be used by the sensor, which will make the sensing more robust.

[0059] Also, any angle between the second winding 2 and the third winding 3 can be used, but the central axes of the second winding 2 and the third winding 3 are not parallel. [Explanation of symbols]

[0060] S sensor (resolver) W wheels R reference position 1 First Winding 2 Second Winding 3 Third Winding 4-turn transformer 5. First Filter 6 Second Filter 7. Third Filter 8. Signal Generation and Processing Unit 9 Wire and Coil Inspection Unit S1 First terminal S2 Second terminal S3 Third terminal S4 4th terminal R1 5th terminal R2 6th terminal AC induced voltage Vr First induced voltage Vc Second induced voltage

Claims

1. 1. A signal processing method, in particular for determining the angular position of a wheel of a railway vehicle, comprising: a) exciting a first winding (1) with an AC voltage (Vr), the first winding (1) being provided on a wheel (W), and the first winding (1) can include any angle (θ) relative to a reference position (R); b) measuring a first induced voltage (Vs) in the second winding (2) and supplying said induced voltage (Vs) to a signal generating and processing unit (8); c) measuring a second induced voltage (Vc) in the third winding (3) and supplying said induced voltage (Vc) to said signal generating and processing unit (8), wherein the central axes of said second winding (2) and said third winding (3) are not parallel; d) determining the rotation angle (θ) of the wheels (W) in the signal generation and processing unit (8); e) calculating the rotational speed and / or rotational position of said wheels (W).

2. In step a), an excitation current (Vr) is provided by the signal generating and processing unit (8), filtered by a first filter (5) and supplied to the first winding (1); and / or the first induced voltage (Vs) is filtered by a second filter (6) before being fed to the signal generating and processing unit (8); and / or 2. A signal processing method according to claim 1, wherein the second induced voltage (Vc) is filtered by a third filter (7) before being supplied to the signal generating and processing unit (8).

3. 3. A signal processing method according to claim 1 or 2, wherein the excitation of the first winding (1) by an AC voltage (Vr) is performed at two or more frequencies.

4. 4. A signal processing method according to claim 3, wherein the excitation of the first winding (1) by an AC voltage (Vr) is performed at N frequencies to estimate the axle speed / position and at M frequencies to search a less noisy frequency range.

5. 5. A signal processing method according to claim 1, wherein the sampling frequency of the evaluation of the first induced voltage (Vs) and the second induced voltage (Vc) is approximately twice the excitation frequency of the excitation current (Vr).

6. f) performing braking of said wheels (W); g) measuring the overall vehicle (V) speed and calculating the slip of the wheels (W) based on the rotational speed of the wheels (W) and the overall vehicle (V) speed.

7. 7. A signal processing method according to any one of claims 1 to 6, wherein the wire and coil inspection unit (9) inspects the wire for breakage at predetermined intervals.

8. 8. The signal processing method according to claim 7, wherein the coil inspection unit (9) communicates with the signal generation and processing unit (8) via a protected data line and transfers diagnostic information, which is used to select appropriate signal processing depending on the availability of the first winding (1), the second winding (2) and / or the third winding (3).

9. 9. A signal processing method according to any one of claims 1 to 8, wherein the signal generation and processing unit (8) provides a quality parameter output signal describing the reliability of the position and velocity signals in real time.

10. A sensor (S), a first winding (1) provided on a wheel (W), the first winding (1) being capable of having any angle (θ) with respect to a reference position (R); a second winding (2) and a third winding (3), wherein the directions of the second winding (2) and the third winding (3) are not parallel; a signal generating and processing unit (8) adapted to provide an AC voltage to the first winding (1) and to receive a first induced voltage (Vs) in the second winding (2) and a second induced voltage (Vs) in the third winding (2).

11. a first filter (5) is provided somewhere between the signal generating and processing unit (8) and the first winding (1); and / or a second filter (6) is provided between the signal generating and processing unit (8) and the second winding (2); and / or 11. The sensor (S) according to claim 10, wherein a third filter (7) is provided between the signal generating and processing unit (8) and the third winding (3).

12. 12. The sensor (S) according to claim 10 or 11, wherein the first filter (5) and / or the second filter (6) and / or the third filter (7) are adapted to implement band-pass filtering to remove any DC offset from the measured or generated signal.

13. The sensor (S) according to any one of claims 10 to 12, wherein a wire and coil inspection unit (9) is provided adapted to inspect whether the wire is broken.

14. A braking system (B) for a railway vehicle, comprising at least one sensor (S) according to any one of claims 10 to 13.

15. Use of a sensor (S) according to any one of claims 10 to 13 for determining the rotational speed and / or rotational position of a wheel (W) of a railway vehicle (V) and / or for determining wheel slip of a wheel (W) of a railway vehicle (V).

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