FIELD OF THE DISCLOSURE

The present disclosure relates to a railway bogie comprising a sensor arrangement for a railway vehicle, to a railway vehicle comprising such a railway bogie and to a method for steering a railway bogie of a railway vehicle.

BACKGROUND OF THE DISCLOSURE

Railway vehicles, which are track bound such as trains, trams (streetcars, tramway) or other vehicles often exhibit wheels that are not optimally aligned to the tracks leading to higher friction between the railway track and treads of the wheels. Especially in curves with a small radius, this contact leads to an increased profile wear and noise pollution. In case of low-floor vehicles, this effect is even more pronounced: The low-floor vehicles feature smaller and less wheels per vehicle in order to increase the passenger comfort and inner space of the vehicle by having a continuous low-floor structure. However, this further leads to enhanced loads per wheel and a more pronounced fatigue of the wheel’s material causing smaller rifts or even larger material fractures.

In addition, reducing the number of wheels per vehicle and I or per bogie of the vehicle reduces the suspension comfort of the vehicle and I or of the vehicle comprising the bogie for passengers. In particular, with low floor vehicle this leads to a conflict between inner space requirements and suspension comfort require- merits. Further, creating a desired suspension comfort for the passengers requires conventionally a sophisticated suspension concept arranged above the bogie and between the bogie and the vehicle, which consumes a lot of construction space and further reduces the available inner space for the passengers.

Several attempts are known to reduce the track and wheel wear. In the 1990’s, systems have been developed that were able to steer the wheels in curves. However, it turned out that these solutions often suffered from undesired side effects in straight track sections such that the wheels adhered one-sided with the tread on the track, leading to an enhanced wear and noise in straight track sections. Hence, after a few years, most of these concepts were discarded and conventional concepts combined with wheel-noise absorbers and advanced industrial lubricants were again pursued. A particular challenge was and still is to measure accurately and reliably during operation of the bogie the position of the bogie with respect to the railway track.

One example of a railway bogie, which addresses these disadvantages in a successful manner is the WO2018015290 published 2018 in the name of the same applicant. The disclosed vehicle comprises a wheel assembly interconnected to a chassis as well as a method for steering said vehicle. The wheel assembly comprises a cross-member having a first end to which a first hub is interconnected by a first steering joint and a second end to which a second hub is interconnected by a second steering joint. A first wheel is attached to the first hub rotatable around a first rotation axis and a second wheel is attached to the second hub rotatable around a second rotation axis. SUMMARY OF THE DISCLOSURE

The object of the present disclosure is to provide a railway bogie for a railway vehicle, a railway vehicle comprising the railway bogie and a method for steering a railway bogie of a railway vehicle. In particular, it is an object of the present disclosure to provide a railway bogie comprising a sensor arrangement for a railway vehicle, a railway vehicle comprising the railway bogie with the sensor arrangement and / or a method for steering a railway bogie of a railway vehicle using measurements of a sensor arrangement, which do not have at least some of the disadvantages of the prior art.

According to the present disclosure, a railway bogie comprising a sensor arrangement is specified. The sensor arrangement is configured for determining a lateral position of a wheel of the railway bogie with respect to a rail of a railway track on which the railway bogie is positioned. The sensor arrangement usually comprises a sensor unit, which is configured, during operation of the railway bogie along the railway track, to provide a first sensor signal corresponding to a lateral position of the sensor unit with respect to an essentially vertical flange of the rail, and to provide a second sensor signal corresponding to a vertical position of the sensor unit with respect to an essentially horizontal surface of the rail. Preferably, the first sensor signal and the second sensor signal are in combination configured to be used to determine the lateral position of the wheel with respect to the rail. In other words, the sensor unit is configured to provide signal(s) from which the lateral positon of the sensor unit with respect to one of the essentially vertical flanges of the rail can be determined in an accurate manner. Further, the sensor unit can be configured to provide a signal, which allows to determine the vertical position of the sensor unit with respect to one of the essentially horizontal surfaces of the rail. The sensor unit, may only provide one single sensor signal, which may comprises the first sensor signal and the second sensor signal. The one single sensor signal may be received from a respective single sensor of the sensor unit, capable of providing the single sensor signal comprising the first sensor signal (lateral data) and the second sensor signal (vertical data). A respective processing unit may be configured to determine from the received one single sensor signal the first sensor signal (lateral data) and the second sensor signal (vertical data).

During movement along the rail, the railway bogie moves between boundaries, for example defined by guiding edges of the rail. Every time the flanges of the wheels of the railway bogie hit a guiding edge, the railway bogie is brought back to a central position, especially in curves. This conventional passive system produces lots of noise every time the wheel flanges hit the rail. Knowing the exact lateral position of the wheel with respect to the rail is in particular important for noise and wear reduction. The railway bogie according to the present disclosure comprising the sensor arrangement enables to determine the lateral position of the wheel, and therefore of the bogie, with respect to the respective rail in an advantageous precise and robust manner. According to the present disclosure, the provided lateral position of the sensor unit and the provided vertical position of the sensor unit are in combination used for determining of the lateral position of the wheel. During operation, the vertical position of the sensor unit, which might be arranged rigidly with respect to a wheel rotation axis changed due to curves, wear over time, contamination of the rails etc. This change in vertical position is important for the measurement of the lateral position of the sensor unit. Without measuring the vertical position, the accuracy of the determination of the lateral position of the wheel would not be possible with the required accuracy for a precise and reliable determination of the lateral position of the wheel with respect to the rail. Only the usage of the lateral position in combination with the vertical position of the sensor unit with respect to the corresponding surface of the rail enables to determine the lateral position of the wheel with respect to the rail with the required accuracy and robustness during operation of the railway bogie. The sensor arrangement may comprise as a sensor unit one single sensor, which is configured to provide the first sensor signal and the second sensor signal.

In a variation of the disclosure, the sensor unit comprises a first sensor, configured to provide the first sensor signal, and a second sensor, configured to provide the second sensor signal. Having one sensor for each of the required sensor signals increases the robustness and accuracy and additionally provides a certain redundancy for the measurement of the first and second sensor signal. In addition, it is possible to combine the first sensor signal and the second sensor signal advantageously simple and reliable for the determination of the lateral position of the sensor unit with respect to the rail.

Advantageous accurate measurement results are achievable when the distance, vertical distance, between the sensor unit and the essentially horizontal surface of the rail is in a range from 25 mm to 5 mm. The accuracy I performance of the sensor signal depends on the distance of the sensor unit to the rail. The preferred distance depends on the sensor type and / or sensor requirements. In a variation of the present disclosure, the sensor arrangement comprises a sensor array comprises the first sensor and the second sensor and preferably additional sensors, which provide the first sensor signal and the second sensor signal. The sensor array may comprise one or several sensor units and I or one or several sensors. The sensor array may further be used synonymously with the sensor unit. In a further variation, the sensor array may comprise only one single sensor, which provides the first and the second sensor signals, for example in one or in two sensor signals. In a further variation, the sensor array may comprise the first sensor providing the first sensor signal and the second sensor providing the second sensor signal. It is also conceivable that the sensor array comprises additional third or fourth or even more sensors, configured to provide additional sensor signals, which are additionally used for determining the position and orientation of the railway bogie on the respective railway track during operation of the railway bogie.

Advantageous positioning of the first sensor with respect to the second sensor is achievable when the first sensor and the second sensor are in lateral direction spaced apart with respect to each other. This positioning reflects additionally the orientation of the essential vertical flange of the rail and the essential horizontal surface of the rail and is therefore advantageous for an accurate measurement. It is further preferred, that the first sensor and the second sensor are alternatively or additionally in running direction and I or in vertical direction spaced apart from each other. It is preferred that the first and second sensors are spaced apart from each other. The distance between the different sensors may be determined by the sensor type. For example, the first sensor is arranged in front of the respective wheel and the second sensor is arranged behind the respective wheel. The distance between the first sensor and the second sensor helps advantageously to avoid signal disturbance / signal interference.

Improvement of the sensor signal quality and therefore the accuracy of the measurements of the sensor unit is achievable when the first sensor is configured to be positioned during operation substantially above the essentially vertical flange of the rail, preferably above a guiding flange of the rail, and wherein the second sensor is configured to be positioned during operation substantially above the essentially horizontal surface of the rail, preferably above a running surface of the rail. The guiding flange of the rail is the vertical flange of the rail, which is configured to be in contact with an essentially vertical flange of the wheel for guiding of the wheel on the rail. The running surface of the rail is the surface, which is configured to be in contact with a running surface of the wheel, or a tread of the wheel. Positioning of the first sensor and the second sensor according to this embodiment improves therefore the signal quality, in particular because these surfaces of the rail are configured to be in contact with the wheel and have advantageous smooth surface properties.

In a variation of the disclosure, the sensor arrangement comprises a housing, which is configured to at least partially contain I comprise the sensor unit. In other words, the housing is configured to hold the sensor unit, or the first and second sensors. In an embodiment, the housing is just a plate onto which the sensor unit I sensors are attached. In another embodiment, the housing comprises a cavity in which the sensor unit / sensors are at least partially, preferably entirely, ar- ranged, for example rigidly. The housing is at least one part of the sensor arrangement, which is configured to position the sensor unit, which respect to the respective wheel. The housing provides therefore an advantageous reliable solution for positioning and protecting of the sensor unit. In a further embodiment, the housing is a portion of a different part of the railway bogie like an electromagnetic rail brake.

Protection improvement is advantageously achievable when the housing comprises a protective layer, which is arranged between the sensor unit and a lower outer surface of the housing. The lower outer surface of the housing is the surface, which faces during operation of the railway bogie towards the rail. The protective layer is arranged between the sensor unit and the rail for protecting the sensor unit from potential mechanical damage. The protective layer is configured to be at least partially transparent for the sensor unit. In other words, the measurement of the sensor unit is at least partially not affected by the protective layer. The protective layer may cover partially or entirely the lower surface of the sensor unit I the sensors for protecting the sensors from mechanical damage.

It is preferred that the protective layer and the housing are at least partially integrally formed, in particular integrally molded. Integrally formed means that the housing comprises the protective layer and I or that the housing and the protective layer are formed out of one piece, for example, the housing and the protective layer are milled out of one piece. In another variation, the housing and the protective layer are integrally molded, for example integrally casted or 3d-printed. In a variation of the present disclosure, the protective layer and I or the housing comprise a non-conductive material, preferably an epoxy-based resin. Epoxy resins, also known as polyepoxides, are a class of reactive prepolymers and polymers, which contain epoxide groups. The epoxide functional group is also collectively called epoxy. Epoxy-based resins are non-conductive, relatively simple to form and provide the required transparency in combination with the required protection from mechanical damage.

Additional protection of the sensor unit is achievable when the sensor arrangement further comprises a protective shield, arranged in front of and I or behind the sensor unit with respect to the running direction and configured to protect the sensor unit from mechanical damage during operation of the railway bogie. The protective shield is for example a part or a portion of the housing or is a separate part.

An advantageous determination of the lateral position of the wheel is achievable when the sensor arrangement further comprises a front sensor unit configured to be arranged in front of the respective wheel of the railway bogie with respect to the running direction, and a back sensor unit configured to be arranged behind the respective wheel of the railway bogie with respect to the running direction. According to this embodiment, the sensor arrangement of one of the wheels of the railway bogie comprises the front sensor unit arranged in front of the wheel and the back sensor unit arranged behind the respective wheel with respect to the running direction. The sensor arrangement according to this embodiment measures lateral and vertical position of the front sensor unit and the back sensor unit. The first sensor signal and the second sensor signal of the front sensor unit and the back sensor unit are used to determine the lateral position of the wheel with respect to the rail and in addition a tangential position of the wheel with respect to the rail. The tangential position determines the orientation of the running direction of the wheel, in particular the running direction of the wheel tread and wheel flange, with respect to the rail. With the front sensor and the back sensor, it is advantageously possible to determine additionally the tangential position of the wheel(s) with respect to the rail. This highly increases the precision of the determination of the overall position of the wheel with respect to the rail, in particular because front measurements and back measurements are considered. Further, this embodiment increases the redundancy within the sensor arrangement.

In a further advantageous embodiment, a plurality of the wheels of the railway bogie, preferably each wheel comprises the front sensor unit and I or the back sensor unit. In other words, two of the wheels of the railway bogie, which are for example arranged lateral next to each other, comprise a front sensor unit and a back sensor unit. The sensor arrangement of this railway bogie comprises four sensor units, which measure four lateral positions and four vertical positions. This arrangement advantageously increases the measurement accuracy of the position of the railway bogie with respect to the rails and the redundancy of the sensor arrangement within the railway bogie.

In a preferred embodiment, the sensor arrangement comprises a sensor bracket configured to position the at least one sensor unit in front of or behind the respective wheel of the railway bogie with respect to the running direction of the wheel, wherein the sensor bracket is configured to be arranged pivotable with respect to the respective wheel, in particular with respect to a swing arm, about a leveling axis. The wheel is for example mounted by the swing arm to the frame, wherein the swing arm is pivotable with respect to the frame around a pivot axis against the force of a swing arm spring. In other words, the swing arm provides a damped connection between the wheel and the frame of the railway bogie. The wheel moves during operation of the railway bogie around the pivot axis. This movement is limited and decelerated by the swing arm spring. The swing arm in combination with the swing arm spring provides a suspension for the wheel with respect to the frame, especially for high frequency vibrations coming from the railway track. The pivotable arrangement of the sensor bracket with respect to the swing arm enables and advantageous simple and reliable system for leveling I balancing of the sensor unit arranged on the tip of the sensor bracket due to deflection of the swing arm during operation of the railway bogie. Movement of the sensor bracket around the leveling axis compensates the deflection of the swing arm in an advantageous simple and reliable manner.

In a further preferred embodiment, the sensor arrangement further comprises at least one leveling actuator configured to be coupled to a frame of the railway bogie, preferably to a base frame, and to the sensor bracket for leveling the orientation of the sensor bracket with respect to the rail during operation of the railway bogie or to the sensor unit for leveling the vertical position of the sensor unit with respect to the rail during operation of the railway bogie. The sensor unit is for example arranged on the leveling actuator and is arranged vertically displaceable with respect to the frame by movement of the leveling actuator. For example, the sensor unit measures its vertical position with respect to the rail and send an adjustment signal to the leveling actuator in case the measured vertical position does not correspond to a desired vertical position, for example due to suspension movement of the frame. The signal may also be sent by a control unit. The leveling actuator can then adjust the vertical position. A control loop may be implemented for adjusting of the vertical position of the sensor unit during operation.

It is preferred that the leveling actuator is coupled to the sensor bracket and is configured to swivel the sensor bracket around the leveling axis for adjusting the vertical position of the sensor unit with respect to the rail during operation of the railway bogie. According to this embodiment, linear movement of the leveling actuator causes rotation of the sensor bracket around the leveling axis, which enables to adjust I level the vertical position of the sensor unit in front or behind the respective wheel. This embodiment enables advantageously to use a leveraging solution for the leveling actuator.

It is further preferred that the railway bogie comprises two leveling actuators, wherein a first leveling actuator is arranged in front of the wheel and a second leveling actuator is arranged behind the wheel with respect to the running direction, and wherein the two leveling actuators are interconnected for adjusting of the vertical position of the sensor unit. According to this embodiment, the two leveling actuators are connected to the sensor bracket and enable movement of the sensor bracket, which creates an advantageous redundancy. It is further important that both leveling actuators are synchronized with respect to each other for a smooth rotation of the sensor bracket around the leveling axis.

In an embodiment, the sensor leveling system comprises a cross linkage unit interconnecting the first leveling actuator and the second leveling actuator, wherein the cross linkage unit is configured to transfer movement of one of the leveling actuators to movement of the other one of the leveling actuators such that both leveling actuators move simultaneously. The cross linkage unit is for example a control unit, which is configured to harmonize and I or synchronize the movement of the leveling actuators.

A preferred mounting of the sensor unit(s) on the railway bogie is achievable when the railway bogie comprises at least one shim, preferably a plurality of shims I spacers, arranged between the sensor unit I sensor housing and the sensor bracket and configured for adjusting the vertical position of the sensor unit with respect to the rail. The shims are, for example, spacers, which are stacked and which are placed between the sensor unit and the sensor bracket. It is possible to adjust the vertical position of the sensor unit by removing or adding one or more shim(s). Wear of the wheels may cause a change in wheel diameter, which causes a change in the vertical position of the respective sensor unit. Removing at least one shim enables to adjust the vertical position back to the original value in a reliably and simple manner.

In a further advantageous variation of the present disclosure, the railway bogie comprises a control unit configured to receive the first sensor signal and the second sensor signal from the sensor unit. The first sensor signal and the second sensor signal are for example voltage values, which are transmitted from the sensor unit, for example, by wire or wireless, to the control unit. The control unit is further configured to determine the lateral position of the wheel with respect to the rail using the received first sensor signal and the received second sensor signal. The control unit may be configured to determine from a plurality of first sensor signals and second sensor signals from a plurality of sensor units the lateral position of the wheel(s) with respect to the corresponding rail. The control unit is further configured to determine a steering angel for steering of the railway bogie on the railway track based on the determined lateral position of the wheel of the railway bogie. It is therefore possible to align the railway bogie tangentially with respect to the rail during operation, which is highly advantageous for noise and wear reduction, in particular in curves. Conventional railway bogies have in the lateral direction a rigid connection between the different wheels. Determining the lateral position of one of the wheels is therefore sufficient for steering of the railway bogie. Nevertheless, it is advantageous to determine the lateral position of two or more wheel of the railway bogie with respect to the rail, for an advantageous increased accuracy of steering. In particular in narrow curves, for example for tram vehicles. Further, the lateral distance between the two rails is not always exactly the same throughout a railway track. Measuring the lateral position of more than one wheel with respect to the corresponding rail increases therefore the steering performance, which advantageously reduces the wear of the wheels and noise pollution during operation of the railway bogie.

It is preferred that the control unit is configured to clean, filter and average the received first sensor signal and I or the second sensor signal, which helps to improve the received signal quality. It is further preferred that the control unit is configured to bilinear interpolate the received first sensor signal and the received second sensor signal for determining the lateral position of the wheel with respect to the rail. The bilinear interpolation is an advantageous simple and reliable solution for combining the first sensor signal with the second sensor signal for determining the lateral positon of the wheel with respect to the rail. In an aspect of the present disclosure, a railway vehicle is specified, which comprises a railway bogie as described above and hereinafter.

In a further aspect of the present disclosure, a method for steering a railway bogie of a railway vehicle is specified. The method comprises the steps of: providing a railway vehicle comprising the railway bogie as described above and hereinafter; providing, by the sensor unit, the first sensor signal and the second sensor signal; determining, by a control unit, the lateral position of the wheel with respect to the railway track, using the received first sensor signal and the received second sensor signal; determining, by the control unit, a steering angel, using the determined lateral position of the wheel; swiveling, by a steering system, the railway bogie around a steering axis about the determined steering angle, for steering of the bogie. The steering system may comprise a steering actuator and I or at least one electrical engine and I or at least one brake, which is I are configured to steer the railway bogie around the steering axis about the steering angle. The steering angle is determined to achieve the desired lateral and tangentially alignment of the wheel(s) with respect to the rails. It is preferred that the received first sensor signal(s) and the received second sensor signal(s) are bilinear interpolated, by the control unit for determining the lateral position of the wheel(s) with respect to the rail and I or the steering angle. The bilinear interpolation is an advantageous simple and reliable solution for combining the first sensor signal with the second sensor signal for determining the lateral positon of the wheel with respect to the rail. In a further embodiment, the control unit determines a correction factor to re-establish an optimal running position of the respective wheel with respect to the rail. The correction factor is then transformed in a corresponding steering angle. It is preferred that the position of the wheel(s) is controlled throughout the operation of the railway vehicle permanently or at predefined timestamps, for example every 10 milliseconds, for example using a control loop.

In a preferred variation of the disclosure, the sensor unit, in particular the first sensor and I or the second sensor, are an inductive sensor, a laser sensor, a capacitive sensor, an ultrasonic sensor, an optical sensor, a radar sensor or a combination thereof. Inductive sensors usually achieve good results, even if the railway track is contaminated and/or below snow.

In a further aspect, a sensor arrangement for a railway bogie for determining a lateral position of a wheel of the railway bogie with respect to a rail of a railway track on which the railway bogie is positioned is specific, the sensor arrangement comprising a sensor unit configured, during operation of the railway bogie along the railway track, to provide a first sensor signal corresponding to a lateral position of the sensor unit with respect to an essentially vertical flange of the rail, and to provide a second sensor signal corresponding to a vertical position of the sensor unit with respect to an essentially horizontal surface of the rail. The first sensor signal and the second sensor signal are configured to be used to determine the lateral position of the wheel with respect to the rail. The embodiments and advantages mentioned and described in detail above and hereinafter with respect to the railway bogie and its various embodiments comprising the sensor arrangement also apply to the aspect of the sensor arrangement and its various embodiments respectively.

It is preferred that the sensor unit comprises a first sensor, configured to provide the first sensor signal, and a second sensor, configured to provide the second sensor signal. It is advantageous if the first sensor and the second sensor are in lateral direction spaced apart with respect to each other. In another embodiment, the sensor unit comprises only one sensor, which measures and provides for example the first sensor signal and the second sensor signal, for example as two sensor signals or as one sensor signal. In another embodiment, the sensor unit or sensor array comprises a plurality of sensors, which provide for example in combination the sensor signals.

It is preferred that the first sensor is configured to be positioned during operation substantially above the essentially vertical flange of the rail, preferably above a guiding flange of the rail, and wherein the second sensor is configured to be positioned during operation substantially above the essentially horizontal surface of the rail, preferably above a running surface of the rail. An advantageous protection of the sensor unit is achievable when the sensor arrangement comprises a housing configured to at least partially contain the sensor unit. In a variation, a protective layer is arranged between the sensor unit and a lower outer surface of the housing, wherein the protective layer is configured to be at least partially transparent for measurements of the sensor unit during operation and to protect the sensor unit from mechanical damage/impacts during operation of the railway bogie. Further, the protective layer and the housing may be at least partially integrally formed, in particular integrally molded. In addition, the protective layer and I or the housing may comprise or may be made of a non- conductive material, preferably an epoxy-based resin.

In a preferred variation, the sensor arrangement comprises a front sensor unit configured to be arranged in front of the respective wheel of the railway bogie with respect to the running direction, and a back sensor unit configured to be arranged behind the respective wheel of the railway bogie with respect to the running direction. The first sensor signal and the second sensor signal of the front sensor unit and the back sensor unit are configured to be used to determine the lateral position of the wheel with respect to the rail and a tangential position of the wheel with respect to the rail.

An advantageous positioning is realizable when the sensor arrangement comprises a sensor bracket configured to position the at least one sensor unit in front of or behind the respective wheel of the railway bogie with respect to the running direction of the wheel, wherein the sensor bracket is configured to be arranged pivotable with respect to the respective wheel about a leveling axis. The sensor arrangement may further comprise a leveling actuator configured to be coupled to a frame of the railway bogie and to the sensor bracket for leveling the vertical position of the at least one sensor unit with respect to the rail during operation of the railway bogie.

The sensor arrangement may further comprise at least one shim arranged between the sensor housing and the sensor bracket and configured for adjusting the vertical position of the sensor unit with respect to the rail.

In a further aspect, a method for determining a lateral position of a wheel of a railway bogie with respect to a railway track, the method comprising the steps of providing a sensor arrangement as described above and hereinafter, providing, by the sensor unit, the first sensor signal and the second sensor signal, and determining, by a control unit of the sensor arrangement, the lateral position of the wheel with respect to the railway track, using the received first sensor signal and the received second sensor signal.

The step of determining, by the control unit, the lateral position of the wheel may further comprise cleaning, filtering and averaging, by the control unit, of the received first sensor signal and the received second sensor signal and I or bilinear interpolating, by the control unit, of the received first sensor signal and the received second sensor signal.

It is to be understood that both the foregoing general description and the following detailed description present embodiments, and are intended to provide an overview or framework for understanding the nature and character of the disclosure. The accompanying drawings are included to provide a further understanding, and are incorporated into and constitute a part of this specification. The drawings illustrate various embodiments, and together with the description serve to explain the principles and operation of the concepts disclosed. BRIEF DESCRIPTION OF THE DRAWINGS

The herein described disclosure will be more fully understood from the detailed description given herein below and the accompanying drawings, which should not be considered limiting to the disclosure described in the appended claims.

The drawings are showing: Fig. 1 a perspective view of a first variation of the railway bogie according to the disclosure;

Fig. 2 a first perspective view of a second variation of the railway bogie according to the disclosure;

Fig. 3 a second perspective view of the second variation of Fig. 2; Fig. 4 a detailed view of Fig. 3;

Fig. 5 a section view through the railway bogie according to the second variation;

Fig. 6 a detailed view of Fig. 5; Fig. 7 a detailed view of a further variation of the sensor arrangement;

Fig. 8 a profile of a tram rail according to an exemplary variation;

Fig. 9 a geometrical comparison of train rails and tram rails and a comparison of sensor units;

Fig. 10 maps of first and second sensor signals;

Fig. 11 a map of a combination of first and second sensor signals.

DESCRIPTION OF THE EMBODIMENTS

Reference will now be made in detail to certain embodiments, examples of which are illustrated in the accompanying drawings, in which some, but not all features are shown. Indeed, embodiments disclosed herein may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will satisfy applicable legal requirements. Whenever possible, like reference numbers will be used to refer to like components or parts.

Figure 1 shows a perspective view of a first variation of the railway bogie according to the disclosure. Figure 2 shows a first perspective view of a second variation of the railway bogie according to the disclosure. Figure 3 a second perspective view of the second variation of Figure 2. Figure 4 shows a detailed view of Figure 3. Figure 5 shows a section view through the railway bogie according to the second variation. Figure 6 shows a detailed view of Figure 5. Figure 7 shows a detailed view of a further variation of the sensor arrangement. Figure 8 shows a profile of a tram rail according to an exemplary variation. Figure 9 shows geometrical comparison of train rails and tram rails and a comparison of sensor units. Figure 10 shows maps of first and second sensor signals. Figure 11 shows a map of a combination of first and second sensor signals.

As e.g. visible in Figures 1, 2, 3 and 5, a railway bogie 1 comprises a base 2, which is configured to be attached to a chassis of a railway vehicle. The base 2 may be connected to a connecting part 9, which is configured to be connected to the chassis of the railway vehicle during operation of the bogie 1 . The bogie 1 further comprises a frame 3 arranged rotatable with respect to the base 2 around a vertical steering axis 4. The bogie 1 further comprises two wheels 5, which comprise a tread 6. The tread 6 or tread profile is the radially external portion of the wheel 5. The tread 6 comprises a contact surface or a rolling surface, which is, during operation, in contact with a rail 32 of a railway track 31 . The wheels 5 are arranged rotatable with respect to the frame 3 around a respective wheel rotation axis 7. The wheel rotation axis 7 of the wheels 5 are arranged essentially coaxially to each other and the steering axis 4 is arranged in a lateral direction Y between the two wheels 5. In another variation, the wheel rotation axis 7 may be arranged at a specific angle with respect to the lateral direction Y. In this case, the wheel rotation axis 7 are inclined with respect to the lateral direction Y. Figure 1 further shows covers 30 arranged on the frame 3 for protection of the bogie 1 during operation.

The Figures further show that the frame 3 comprises a base frame 23 and a wheel frame 24. The base frame 23 is arranged mainly above the wheel frame 24. The base frame 23 is interconnected to the wheel frame 24 via a spring damping system 12 and vice versa. The spring damping system 12 comprises a damper 25 and a spring assembly 26 with a first spring 27 and a second spring 28. A strut 29 is arranged between the base frame 23 and the wheel frame 24.

The bogie 1 further comprises a sensor arrangement 11 , best visible in Figures 3, 4 and 5, which is configured to determine during operation the lateral position of at least one of the wheels 5 with respect to the rail 32 of the railway track 31 . The sensor arrangement 11 enables to determine the position of the wheels 5 on the railway track 31 during operation, which is crucial to control the position of the treads 6 of the wheels 5 with respect to the railway track 31 for noise and wear control/reduction and to steer the railway bogie 1 during operation for an advantageous noise and wear control I reduction.

Figure 1 further shows a steering actuator 16, which is connected to the frame 3 and to the connecting part 9. Movement of the steering actuator 16 cause a rotation of the frame 3 around the steering axis 4 by a steering angle with respect to the base 2 and with respect to the connecting part 9 and also with respect to the chassis of the railway vehicle.

Figures 3, 4 and 7 further show the sensor arrangement 11 in detail. The sensor arrangement 11 comprises a front sensor unit 13 arranged in front of the respective tread 6 of the wheel 5 with respect to a running direction X of the bogie 1 . The sensor arrangement 11 further comprises a back sensor unit 14 arranged behind the respective tread 6 of the wheel 5 with respect to the running direction X of the bogie 1 . A synonym for the sensor units 13, 14 may be sensor array. As best visible in Figure 3, both wheels 5 of the railway bogie 1 comprise the front sensor unit 13 and the back sensor unit 14. The front sensor unit 13 and the back sensor unit 14 are arranged on a sensor bracket 15, which is mounted pivotable with respect to the wheel 5. The sensor bracket 15 extends along the wheel 5 and holds the respective sensor units 13, 14 at a predefined position during operation of the railway bogie 1. The sensor bracket 15 is arranged pivotable with respect to the wheel around a leveling axis 10, best visible in Figure 4. The leveling axis 10 is arranged parallel with respect to the respective wheel rotation axis 4 and on the same vertical virtual plane as the wheel rotation axis 4.

The bogie 1 further comprises leveling actuators 8, best visible in Figures 5 and 6, which are connected to the frame 3 and to the respective sensor bracket 15. Linear movement of the leveling actuators 8 adjusts during operation of the bogie 1 the vertical position 41 of the front sensor unit 13 and I or of the back sensor unit 14 with respect to rail 32. Movement of the frame 3, in particular movement of a swing arm 20 of the frame 3, which might affect the vertical position 41 of at least one of the sensor units 13, 14, can be compensated by movement of the leveling actuators 8. In the variation of the disclosure as shown in the Figures, the linear movement of the leveling actuators 8 causes pivoting of the connected sensor bracket 15 around the leveling axis 10. The pivoting around the leveling axis 10 compensates a possible deflection of the swing arm 20 against a swing arm spring 22 around a pivot axis 21 during operation of the railway bogie 1 , such that the vertical position 41 of the respective sensor units 13, 14 may stay as static as possible during operation of the railway bogie 1 . The Figures 1 to 5 further show that each wheel 5 comprises an electrical engine 18 and a brake 19. The electrical engine 18 is configured to drive, if required, during operation the respective wheel 5, and the brake 19 is configured to decelerate, if required, during operation of the railway bogie 1 the respective wheel 5. The brake 19 is a disk brake and the disk of the disk brake is arranged on the same shaft as the respective wheel 5 and the respective electrical engine 18. The wheel 5, the electrical engine 18 and the disk are partially surrounded and held by the swing arm 20, best visible in Figure 3. A brake caliper of the brake 19 is arranged on the swing arm 20.

The Figures further indicate schematically a control unit 17. The control unit 17 is, for example arranged within the railway bogie 1 or at a different position of the railway vehicle. The control unit 17 is configured to receive, during operation of the bogie 1 , a first sensor signal 38 from the sensor unit 35 and the second sensor signal 39 from the sensor unit 35. The sensor arrangement 11 may comprise the control unit 17.

The Figures further show that the railway bogie 1 further comprises a plurality of shims 44 arranged between the sensor unit 31 I sensor housing 42 and the sensor bracket 15 and configured for adjusting the vertical position 41 of the sensor unit with respect to the rail. The shims 44 are, for example, spacers I distance elements, which are stacked and which are placed between the sensor unit 35 and the sensor bracket 15.

The control unit 17 is further configured to determine the lateral position of the wheel 5 with respect to the rail 32 using the received first sensor signal 38 and the received second sensor signal 39. The control unit 17 may be configured to determine from a plurality of first sensor signals 38 and second sensor signals 39 from a plurality of front sensor units 13 and I or back sensor unit 14 the lateral position of the wheel(s) 5 with respect to the corresponding rail 32. The control unit 17 is further configured to determine a steering angel for steering of the railway bogie 1 on the railway track 31 based on the determined lateral position of the wheel 5 of the railway bogie 1 . Conventional railway bogies 1 have in the lateral direction a rigid connection between the different wheels 5 via for example the frame 3. Determining the lateral position of one of the wheels 5 is therefore sufficient for steering of the railway bogie 1 . Nevertheless, it is advantageous to determine the lateral position of two or more wheels 5 of the railway bogie 1 with respect to the corresponding rail 32, for an advantageous increased accuracy of steering. In particular in narrow curves, for example for tram vehicles. Further, the lateral distance between the two rails 32 of a railway track 31 is not always exactly constant throughout the railway track 31 . Measuring the lateral position of more than one wheel 5 with respect to the corresponding rail 32 increases therefore the steering performance, which advantageously reduces the wear of the wheels 5 and noise pollution during operation of the railway bogie 1 .

It is preferred that the control unit 17 is configured to clean and average the received first sensor signal 38 and I or the second sensor signal 39, which helps to improve the received signal quality. It is further preferred that the control unit 17 is configured to bilinear interpolate the received first sensor signal(s) 38 and the received second sensor signal(s) 39 for determining the lateral position of the wheel 5 with respect to the rail 32. The control unit 17 is further configured to determine the steering angle based on the determined lateral position of the wheel 5. The control unit 17 is further configured to control the steering actuator 16 and I or to control the electrical engines 18 and the brakes 19 based on the determined steering angle for swiveling the frame 3 around the steering axis 4 with respect to the base 2.

As best visible in the Figures 5, 6 and 7, the railway track 31 comprises two rails 32, which comprise at least one essentially vertical flange 33 and at least one essentially horizontal surface 34. Essentially vertical means that one extension direction of this flange extends along the vertical direction Z. Essentially horizontally means that one extension direction of this surface extends along the lateral direction Y. Rails 32 of the railway track 31 are not flat but correspond to the shape of the tread 6 of the respective wheel 5 and vice versa. In other words, the vertical flange 33 extends in the vertical direction Z and is, for example, used as a guiding surface for the tread 6 of the wheel 5. The horizontal surface 34 extends in the lateral direction Y and is for example used as a running surface for the tread 6 of the wheel 5.

The Figures 6 and 7 show a lateral position 40 and a vertical position 41 of the sensor unit 35 during operation of the railway bogie 1 . The vertical distance between the running surface of the rail 32 and the outer lower surface of the sensor unit 35 is for example 10 mm. These Figures also show that the first sensor 36 is arranged above the vertical flange 33 and that the second sensor 37 is arranged above the horizontal surface 34 of the rail 32. This increases the measurement performance of the sensor unit 35. Figure 7 further shows the sensor unit 35 comprising the first sensor 36 and the second sensor 37 with the housing 42. The housing 42 comprises the protective layer 43, which is arranged below the sensors 36, 38 for protection of the sensors 36, 37. The housing 42 comprising the protective layer 43 is, according to this embodiment, molded around the sensors 36, 37. The material of the housing 42 is a non-conductive material, for example an epoxy-based resin, and is therefore at least partially transparent for the sensor measurements.

Figure 8 shows a profile of a tram rail 32 with the different dimensions. Figure 8 further shows a coordinate system pointing in the vertical direction Z and in the lateral direction Y. The first sensor 36 and the second sensor 37 of the sensor unit 35 function together as a pair, in order to establish the coordinate system that is oriented relative to the inside edge of a train or tram rail 32.

As the sensor unit 35 moves during operation of the railway bogie 1 laterally and vertically relative to the rail 32, in particular to the inside rail edge, the position of the sensor unit 35 can be uniquely determined by using both measured values (first sensor signal 38 and second sensor signal 39) from the sensor unit 35. The first sensor 36 determines the lateral position 40 of the sensor unit 35 with respect to the rail 32 and the second sensor 37 determines any change in the vertical position 41 .

In principle, the lateral position 40 is more important and relevant, and the vertical position 41 of the sensor unit 35 is used mainly as a comparison check. According to this embodiment, the sensor unit 35 is placed above the inner rail edge and the coordinate system for the lateral position 40 of the sensor unit 35 points outwards, as shown in Figure 8. The value of H (vertical distance from point B to the flat rail surface, horizontal surface 35) is 13mm.

Figure 9 provides a geometrical comparison of train and tram track profiles and its consequences on the measurement of the sensors 36, 37, which are for example conductive sensors.

Figure 9 further shows differences between train and tram track edge detection geometrical comparison of train and tram track profiles (left) and an interpretation of the effect on the sensors 36, 37 between train and tram track profiles (right). BB stands for the first sensor 36.

According to this comparison between train and tram track geometries, the main difference is the steepness of the drop of the rail head. Given the same measured voltage (for example 4V as shown in Figure 9), the actual lateral distance of the sensor unit 35 differs between rail profiles (2 mm vs. 4 mm). This difference in signals between train and tram rails 32 can be accounted for when designing a corresponding railway bogie 1 with the sensor arrangement 11 comprising the control unit 17 and the corresponding active steering solution for the rail 32.

In addition, Figure 10 provides an illustration of the sensor unit 35 responses and signals 38, 39 strengths relative to the inside vertical edge 33 of a rail 32. Figure 10 shows the measured sensor voltages (y-axis) on a tram track for different heights (vertical position 41 ) in grey scale, wherein darker lines relate to lower distances (heights) and brighter lines relate to higher distances (heights), and lateral positions 40 (on the x-axis). The measurement of a train track would look similarly. The upper plot in Figure 10 shows the measurements of the lateral first sensor 36 (Big Boy BB) and the lower plot of Figure 10 shows the measurements of the vertical second sensor 37 (Little Guy LG). Some measurement errors in the plots are attributed to the manual calibration of the industrial robot that was used to position these sensors throughout a known range spacial steps when performing the measurements shown in Figure 10.

The plots of Figure 10 show the measurements of two different sensors 36, 37 and the changes to signals 38, 39 through a range of lateral positions, passing over the inside edge of the rail 32 (different grey scale lines for different heights).

Before operation of the railway bogie 1 , comprising the sensor arrangement 11 , the sensor unit 35 would have be calibrated against a tram track profile, to establish the XYZ origin of the sensor-mapping field. This calibration operation is automatically implemented whenever the railway bogie 1 is powered-up for operation.

Figure 11 shows a combination of sensor signals 38, 39 relative to lateral positioning 40 of the sensor unit 35 over the horizontal surface 34 of a rail 32, in particular a data preparation and interpolation grid.

The sensor unit 35 has been proven in operation on an industrial multi-use robot in order to generate the calibration data to create the interpolation grid. The measured data is loaded into Matlab, cleaned, filtered and averaged. A 2d-interpolation function is then created using the Matlab scatteredlnterpolant function: creates a function that returns the lateral position 40 of the wheel 5 with respect to the rail 32 given both sensor voltages 38, 39 by interpolating over the given data. This function could be used directly in Simulink but since the model are to be exported to ST-code for the PLC using the Simulink PLC coder, additional simplifications could be used.

Figure 11 further shows the total average data measured (brighter grey dots), and the cleaned (un-saturated) and averaged data (darker grey dots). Using the scatteredlnterpolant function, a new interpolation grid is generated over the cleaned data (dark grey surface). This interpolation grid can easily be exported to ST-code. However, in order to detect and prohibit extrapolation beyond the available grid data, the points outside of the grid are set to an invalid value (currently 9999999999 is used). This final interpolation grid is specific and saved. The shape of this signal contour map is directly inputted into the control unit 17, and is used to determine the correction factor needed by the steering actuator 16, to re-establish the optimal running position of the railway bogie 1 running between the two rails 32.

The final Simulink block leverages the Simulink 2d interpolation using pre-look- up, since it allows to check beforehand if any the of the interpolation points on the grid contains the invalid value defined before, in which case the sensor pair is returned as being saturated.

This enables the control unit 17 to eliminate any outlying or faulty sensor signals that may disturb or disrupt the movement of the steering actuator 16. Rather, the words used in the specification are words of description rather than limitation, and it is understood that various changes may be made without departing from the Spirit and scope of the disclosure.

LIST OF DESIGNATIONS

1 Railway bogie 25 Damper

2 Base 26 Spring assembly

3 Frame 27 First spring

4 Steering axis 28 Second Spring

5 Wheel 29 Strut

6 T read 30 Cover

7 Wheel rotation axis 31 Railway track

8 Leveling actuator 32 Rail

9 Connecting part 33 Vertical flange

10 Leveling axis 34 Horizontal surface

11 Sensor arrangement 35 Sensor unit

12 Spring damping system 36 First sensor

13 Front sensor unit 37 Second sensor

14 Back sensor unit 38 First sensor signal

15 Sensor bracket 39 Second sensor signal

16 Steering actuator 40 Lateral position

17 Control unit 41 Vertical position

18 Electrical engine 42 Housing

19 Brake 43 Protective layer

20 Swing arm 44 Shim

21 pivot axis X running direction

22 Swing arm spring Y lateral direction

23 Base frame Z vertical direction

24 Wheel Frame