Signal processing method, sensor and use of sensor for determining rotation speed and / or rotation position of wheel of rail vehicle

Abstract

The invention relates to a signal processing method and a sensor (S) comprising: a first winding (1) which is arranged on a wheel (W), the first winding (1) being able to be at any angle (W) to a reference position (R); a second winding (2) and a third winding (3), and the direction of the second winding (2) is not parallel to the direction of the third winding (3); 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) of the second winding (2) and a second induced voltage (Vs) of the third winding (2). With such a system, the wheel speed / position can be measured very accurately.

Description

Technical Field

[0001] The present invention relates to a diagnostic system for a rail vehicle that quickly and reliably calculates wheel speed and position. Background Art

[0002] For certain applications in rail vehicles, wheel speed and wheel position must be determined very accurately.

[0003] From the prior art, document EP 3 963 617 A1 is known.

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

[0005] For example, in a wheel slip protection system for a train consisting of a single vehicle, a system using a pole wheel based encoder according to the EN standard works well. However, such pole wheel based encoders have certain limitations.

[0006] First, this system does not detect the direction of rotation, which can make obtaining directional information challenging for some applications.

[0007] Furthermore, signal quality may depend on the train's actual speed. Below 3 km / h, speed signals may be unreliable or even unavailable. However, for precise braking, especially in subway stations with doors on the platform, such information is essential.

[0008] Furthermore, if the signal processing delay is too great, quick interventions (e.g. targeted use of micro-slip or maintaining the slip value at a maximum value for adhesion growth) cannot be used. However, lower delays are desirable, which lead to more precise control and more reproducible braking distances.

[0009] Furthermore, if the train is moving from a standstill, torque control can be challenging due to slipping wheels. However, such applications can also benefit from better latency performance.

[0010] Among recent developments, electromechanical actuators are becoming increasingly popular. For example, they can operate without the need for an air supply.

[0011] Furthermore, electromechanical actuators offer lower actuation delays. This significantly reduces the overall braking system latency (speed detection, signal processing, control decision making, actuation). However, the limiting factor is the speed sensor.

[0012] Likewise, automatic train operation is becoming increasingly popular, but has very strict requirements for the stopping position. This type of automatic train operation requires high-quality speed signals when the wheels are moving slowly. As an example of numerical parameters for current designs: if the deceleration is 0.8 m / s 2 , the starting speed is 1m / s (which is a typical specification), then the length of the path traversed by the train can be 0.62m.

[0013] If a train is stopped using only one braking unit, it will travel a certain distance in a virtual blind mode until it comes to a standstill. This is a major drawback of achieving precise stopping using braking alone. In the prior art, one possible implementation of precise stopping is to use the train's traction and braking systems in combination. The braking system can be commanded to generate a certain amount of braking force for precise final position control, and the traction force can be controlled to achieve the desired stopping position. However, in this case, wear on the braking system becomes significant, and a large amount of energy is consumed. Summary of the Invention

[0014] Therefore, the objective technical problem to be solved by the present invention is to provide a signal processing method and a sensor, which can accurately measure the rotational speed and / or rotational position of a wheel, especially a wheel of a train vehicle.

[0015] This object is achieved by a signal processing method according to claim 1, a sensor according to claim 10 and a brake system according to claim 16. In addition, preferred uses of the sensor are mentioned in claim 17.

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

[0017] A signal processing method for determining an angular position, in particular the angular position of a wheel of a rail vehicle, comprising the following steps:

[0018] a) exciting a first winding by an AC voltage, wherein the first winding is arranged on the wheel, wherein the first winding can be at any angle with respect to a reference position;

[0019] b) measuring a first induced voltage in the second winding and transmitting the first induced voltage to a signal generating and processing unit;

[0020] c) measuring a second induced voltage in the third winding, and transmitting the second induced voltage to a signal generating and processing unit;

[0021] d) determining the rotation angle of the wheel in a signal generation and processing unit;

[0022] e) calculating the rotational speed and / or rotational position of the wheel.

[0023] In order to be able to measure two different induced voltages, the center axes of the second winding and the third winding are not parallel.

[0024] The second and third windings are positioned beside the wheels.

[0025] Such a system enables highly accurate wheel position determination, significantly improving train braking performance and enabling real-time track diagnostics. The wheel's rotational speed and position can be easily calculated because—assuming the center 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. 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 relative to 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 outage, the resolver reports its new position upon power restoration.

[0026] Furthermore, the low latency offered by this application makes low-latency electromechanical brake actuators a prerequisite for precise braking using only the braking system. Thanks to the low-latency closed-loop control system driven by the vehicle's absolute position, braking distance repeatability is improved. Even with cheaper materials, lower performance or lower parameter stability in the brake lining and disc materials can be compensated to achieve the same braking performance.

[0027] Furthermore, the high temporal resolution and low latency of the wheel speed / position sensors enable track diagnostics without affecting the vehicle's braking distance. Adhesion curves (the coefficient of friction between the wheel and rail as a function of wheel slip) can be measured or even derived during operational braking or test braking. Test braking can be initiated by the driver. The measured adhesion curve can be reported to the operator, who can then decide whether track cleaning is necessary. During operational braking, artificial wheel slip events can be generated to record the wheel speed profile and derive the adhesion curve. The sensor device according to the present invention can even be installed as an add-on feature on existing polewheel-based encoders.

[0028] The signals generated by the sensor device according to the present invention can be compared in real time with the signals from the pole wheel sensor, allowing this new technology to be verified in real time during retrofitting without compromising vehicle safety. The signals generated by the sensor device according to the present invention are advantageous for a limited number of specific applications, particularly precision parking and adhesion measurement. Furthermore, information can be obtained for speeds below 3 km / h, which are often encountered during system braking.

[0029] The sensor is preferably a resolver. A resolver is a very specialized sensor type with widespread use in a variety of applications, particularly in harsh environmental conditions. It is a very reliable sensor capable of providing precise angular position with milliradian resolution. Depending on the signal processing algorithm, the sensor output can be rotational speed and / or rotational position. This precise output is beneficial for precise parking functions. For example, to achieve a position resolution of 1 cm, an angular resolution of 3.2 milliradians is required for a wheel radius of 0.5 m.

[0030] Preferably, the excitation current is provided by the signal generation processing unit, filtered by the first filter, and delivered to the first winding in step a).

[0031] The filter module provides high voltage protection for the signal generation and processing units. The filter module also implements bandpass filtering to remove any DC offset from the measured or generated signal.

[0032] Therefore, similarly, preferably, the first induced voltage may be filtered by the second filter before being passed to the signal generation and processing unit. The same is true for the second induced voltage, which is filtered by the third filter before being passed to the signal generation and processing unit.

[0033] Preferably, the excitation of the first winding by the AC voltage is performed at more than one frequency. This makes the overall sampling more reliable.

[0034] More preferably, the excitation of the first winding by the AC voltage is performed at more than one frequency to estimate the axle or wheel speed / axle or wheel position, and the excitation of the first winding by the AC voltage is performed at another number of frequencies to search for a frequency range with less noise. This also makes the signal processing very reliable.

[0035] Preferably, the sampling frequency for evaluating the first and second induced voltages is approximately twice the excitation frequency of the excitation current. Thus, leakage effects on the FFT algorithm used by the signal generation and processing unit can be avoided. The excitation used for sampling can then be precisely synchronized.

[0036] Preferably, the estimation algorithm is a correlation search after Fourier transformation of the first, second and third winding channels. Thus, a frequency range with minimal external noise interference can be used.

[0037] In addition, a degraded mode is available, which further increases safety – if part of the conductor breaks, the signal processing method can be switched to single-component mode.

[0038] Position and velocity can be sampled using only one channel (meaning only the second or third winding). If the excitation line (first winding) breaks, the coupling of the first and second winding channels can be exploited to estimate the shaft position or velocity in a less-performing, degraded mode.

[0039] Preferably, the signal processing method further includes the following two steps:

[0040] f) braking the wheels;

[0041] g) Measure the vehicle speed and calculate the wheel slip based on the wheel rotation speed and the vehicle speed.

[0042] Here, the slip characteristics of the wheel can be determined and the adhesion curve (the coefficient of friction between wheel and rail as a function of wheel slip) can be measured or derived during operational braking or testing.

[0043] Preferably, the central axes of the second and third windings are substantially orthogonal, preferably perpendicular. This configuration makes signal generation very reliable. Therefore, the angle calculation is performed using the projection of the rotation vector. If the components are not perpendicular, the calculation can still be performed, but performance is expected to be lower.

[0044] Preferably, the coil inspection unit communicates with the signal generation and processing unit via a protected data line and transfers diagnostic information for selecting appropriate signal processing depending on the availability of the first winding, the second winding and / or the third winding.

[0045] If one of the windings is broken, the signal generation and processing unit can perform signal processing by another method that does not require the broken winding.

[0046] This alternative signal processing may be less accurate, but it can avoid complete failure of wheel speed and position detection. This is advantageous for safety reasons, especially when used in braking systems.

[0047] More preferably, the signal generation and processing unit provides a quality parameter output signal describing in real time the reliability of the position and velocity signals. This is even more advantageous with regard to safety issues.

[0048] The sensor according to the present invention comprises:

[0049] a first winding, the first winding being disposed on the wheel, wherein the first winding may form any angle with respect to a reference position;

[0050] a second winding and a third winding, wherein directions of the second winding and the third winding are not parallel;

[0051] A signal generating and processing unit is adapted to provide an AC voltage to the first winding and to receive a first induced voltage of the second winding and a second induced voltage of the third winding.

[0052] A rotary transformer is preferably provided between the signal generation and processing unit and the first winding. A rotary transformer is a functional unit that forwards the excitation signal from the stationary part to the sensor's rotating excitation coil, which is mounted on the wheel axle. This provides higher precision than, for example, carbon brushes, as there is no wear.

[0053] Preferably, a first filter is positioned somewhere between the signal generation and processing unit and the first coil. More preferably, a second filter is positioned between the signal generation and processing unit and the second coil, and / or a third filter is positioned between the signal generation and processing unit and the third coil. These filters offer the advantage of protecting the signal generation and processing from high voltage overloads. Furthermore, by allowing only the frequencies used by the system to excite the sensors to pass, different signal filtering characteristics can be achieved. The greatest interference with the sensor signals and processing unit is electromagnetic compatibility (EMC) signals from the high-voltage power supply for the train or other trains passing on parallel tracks. The sensor device of the present invention contributes to safety-related functions of the braking system because filtering ensures that only values ​​relevant to the wheel being monitored are used.

[0054] Preferably, the first filter, the second filter and / or the third filter are adapted to perform bandpass filtering to remove any DC offset from the measured or generated signal. This makes the measurement more reliable.

[0055] Preferably, a wire and coil inspection unit is provided, adapted to inspect wires or windings for breakage. If a wire of the second winding and / or the third winding is broken, the signal generation and processing unit can switch to a signal processing method based on a single secondary winding. If a first winding is broken, one of the second or 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.

[0056] The braking system for a rail vehicle of the present invention comprises the sensor device as described above.

[0057] A preferred use of the sensor according to the invention is for determining the rotational speed and / or the rotational position, or even for determining the wheel slip, of wheels of a rail vehicle. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] Preferred embodiments of the present invention are described with reference to the accompanying drawings.

[0059] Figure 1 A schematic diagram of a sensor according to an embodiment of the present invention is shown.

[0060] Figure 2 A schematic diagram of a sensor according to another embodiment of the present invention is shown. DETAILED DESCRIPTION

[0061] Figure 1 A basic embodiment of the present invention is shown. Here, a first winding 1 is provided on a wheel W (not shown here) of a rail vehicle. This first winding 1 is connected to a first filter 5 via a fifth terminal R1 and a sixth terminal R2. The first filter is connected to a signal generation and processing unit 8. A resolver 4 is provided between the first winding 1 and the fifth and sixth terminals R1, R2.

[0062] Furthermore, a second winding 2 is provided outside the wheel, via which a sine signal (Vs = Vr x sinθ) can be measured. Furthermore, a third winding 3 is provided, which measures a cosine signal (Vc = Vr x cosθ). The second winding 2 is connected to a third filter S3 via respective first and third terminals S1, S3, which in turn is connected to a signal generation and processing unit 8. Furthermore, the third winding 3 is also provided with a second terminal S2 and a fourth terminal S4 for a second filter 6, which is also connected to the signal generation and processing unit 8.

[0063] Therefore, a separate filter 5, 6, 7 is used for each winding 1, 2, 3. The signal generation and processing unit 8 is the main signal processing unit. It has a separate output for each winding, i.e. 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.

[0064] exist Figure 2 , a second embodiment is shown. Here, a wire and coil inspection unit 9 is provided. The wire and coil inspection unit 9 is a completely independent electronic component that inspects whether the wires of the first winding 1, the second winding 2 and the third winding 3 are broken.

[0065] For this purpose, the wire and coil checking unit 9 uses a small DC current. The first filter 1 , the second filter 2 and the third winding 3 separate the signal generating and processing unit 8 from the wire and coil checking unit 9 .

[0066] However, the wire and coil inspection unit 9 may report to the wire and coil inspection unit 9 which wire is broken.

[0067] If one or more of the wires of one winding (first winding 1, second winding 2, and / or third winding 3) are broken, the signal generation and processing unit 8 can still operate in a degraded mode. By ignoring the signals from the winding (first winding 1, second winding 2, and / or third winding 3) with the broken wire, some speed and position information can still be extracted.

[0068] If the wire of the excitation winding (second winding 2 and / or third winding 3) is broken, the wire and coil inspection unit 9 can switch one of the second winding 2 or the third winding 3 to the excitation channel (first winding 1) and switch to a different signal processing method to obtain speed and position information.

[0069] The present invention is not limited to the above-described embodiments.

[0070] The sensor can use even more windings, which will make the sensing more reliable.

[0071] Furthermore, various angles between the second winding 2 and the third winding 3 can be used—however, the central axes of the second winding 2 and the third winding 3 cannot be parallel.

[0072] Reference Signs List

[0073] S sensor (resolver)

[0074] W wheel

[0075] R Reference position

[0076] 1. First winding

[0077] 2 Second winding

[0078] 3. Third winding

[0079] 4. Resolver

[0080] 5 First filter

[0081] 6 Second filter

[0082] 7 Third filter

[0083] 8 Signal generation and processing unit

[0084] 9 Wire and coil inspection unit

[0085] S1 first terminal

[0086] S2 second terminal

[0087] S3 third terminal

[0088] S4 fourth terminal

[0089] R1 fifth terminal

[0090] R2 sixth terminal

[0091] AC induced voltage

[0092] Vr first induced voltage

[0093] Vc Second induced voltage

Claims

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

2. The signal processing method according to claim 1, wherein: The excitation current (Vr) is provided by the signal generation and processing unit (8), filtered by the first filter (5), and delivered to the first winding (1) in step a), and / or The first induced voltage (Vs) is filtered by a second filter (6) before being passed to the signal generating and processing unit (8), and / or The second induced voltage (Vc) is filtered by a third filter (7) before being passed to the signal generating and processing unit (8).

3. The signal processing method according to claim 1 , wherein The excitation of the first winding (1) by an AC voltage (Vr) is performed at more than one frequency. The 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 wheel axle speed / position and at M frequencies to search for a frequency range with less noise.

5. Signal processing method according to one of the preceding claims, wherein The sampling frequency for evaluating the first induced voltage (Vs) and the second induced voltage (Vc) is approximately twice the excitation frequency of the excitation current (Vr).

6. The signal processing method according to claim 1 , further comprising the steps of: f) braking the wheel (W); g) measuring the vehicle speed (V), and calculating the slip of the wheel (W) based on the rotation speed of the wheel (W) and the vehicle speed (V).

7. Signal processing method according to one of the preceding claims, wherein The wire and coil inspection unit (9) inspects the wire for breakage at predetermined intervals. 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 transmits 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. The signal processing method according to claim 1, 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), comprising: a first winding (W), the first winding (1) being arranged on a wheel (W), wherein the first winding (1) can form 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) is adapted to provide an AC voltage to the first winding (1) and to receive a first induced voltage (Vs) of the second winding (2) and a second induced voltage (Vs) of the third winding (3).

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

12. Sensor (S) according to one of claims 10 or 11, wherein The first filter (5) and / or the second filter (6) and / or the third filter (7) are adapted to perform bandpass filtering to remove any DC offset from the measured or generated signal.

13. Sensor (S) according to one of the preceding claims 10 to 12, wherein A wire and coil inspection unit (9) is provided, which is suitable for inspecting whether the wire is broken.

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

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

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