FIELD OF THE DISCLOSURE

The present disclosure relates to a railway bogie for damping movement around a vertical steering axis of the railway bogie, to a railway vehicle comprising such a railway bogie and to a method for damping movement around a vertical steering axis of a railway bogie.

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 requirements. 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 intercon- nected 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.

In addition, it is of high importance to provide adequate safety measures such that all safety scenarios are accounted to avoid derailment of a railway vehicle in operation, in particular for a steered railway vehicle. In any event, for example a faulty rail track position sensor, a faulty onboard controller or loss of electrical power, adequate safety measures are required to avoid any accident, like a derailment. Conventional unsteered railway bogies comprise different kinds of safety measures, which avoid derailment of the railway bogie. These conventional safety measures are at least partially not applicable for steered railway bogies. Steerable railway bogies do therefore currently not comprise any adequate safety measures to avoid derailment in all possible safety scenarios.

SUMMARY OF THE DISCLOSURE

The object of the present disclosure is to provide a railway bogie for damping movement around a vertical steering axis, a railway vehicle comprising the railway bogie and a method for damping movement around a vertical steering axis of the railway bogie. In particular, it is an object of the present disclosure to provide a railway bogie for a railway vehicle, a railway vehicle comprising the bogie and a method for damping movement around a vertical steering axis of the railway bogie, which do not have at least some of the disadvantages of the prior art. According to the present disclosure, a railway bogie configured for damping movement around a vertical steering axis of the railway bogie is specified. The railway bogie typically comprising a base configured to be attached to a chassis of a railway vehicle and a frame arranged rotatable with respect to the base around the vertical steering axis. The railway bogie typically further comprises at least two wheels each comprising a tread arranged rotatable with respect to the frame around a respective wheel rotation axis, wherein the two wheels are in a lateral direction arranged spaced apart from each other and at least one sensor assembly is provided and configured to determine during operation the lateral position of the tread of at least one of the two wheels with respect to the railway track. The railway bogie further comprises at least one yaw damper coupled to the frame and configured to dampen movement of the frame around the vertical steering axis in a damping operation mode, and configured to enable essentially undamped movement of the frame around the vertical steering axis in an undamped operation mode.

The yaw damper is for example coupled to the base of the railway bogie, to a non-rotating (with respect to the railway bogie) connecting part of the railway bogie or directly to the chassis of a railway vehicle, which comprises the railway bogie. In other words, the yaw damper is at one longitudinal end connected to a part which does not rotate simultaneously with respect to the railway bogie, such that a relative rotation around the vertical steering axis between this part (base, connecting part, chassis) is realized. The yaw damper is therefore configured to dampen movement of the railway bogie with respect to the base and I or chassis of the railway vehicle around the vertical steering axis. The railway bogie is rotat- able around the vertical steering axis. With the yaw damper, it is possible to control the damping of the movement of the railway bogie around the vertical steering axis. In the undamped operation mode, the yaw damper enables an essential undamped movement of the frame, comprising further components of the railway bogie like the wheels, engines etc., around the vertical steering axis. This undamped operation mode is the normal operation mode during which the railway bogie is working normal and fault free. In this operation mode, it is not required to dampen movement of the frame around the vertical steering axis.

In the damped operation mode, the yaw damper dampens the rotational movement of the frame around the vertical steering axis. This damped operation mode is the safety operation mode, during which safety measures should be initiated such that an accident like a derailment of the railway bogie is inhibited. In the damped operation mode, the damping of the movement around the vertical steering axis is stronger compared to the undamped operation mode. Damping of the rotational movement around the vertical steering axis avoids or at least inhibits derailment of the railway bogie due to an uncontrolled I undamped rotational movement of the frame around the vertical steering axis. The yaw damper according to the present discloser provides therefore a reliable and simple safety measure to avoid derailment of the railway bogie at different safety scenarios. For example, in the event of a power loss of the railway bogie, it is important that the movement around the vertical steering axis of the frame is controlled I damped. By switching the yaw damper in its damped operation mode, it is possible to dampen movement of the frame around the vertical steering axis as required to avoid accidents like the derailment of the railway bogie. An advantageous simple and reliable solution is achievable when the yaw damper comprises a fluidic cylinder comprising a first chamber and a second chamber separated by a moveable piston, wherein the two chambers are fluidi- cally connected via a fluid line with each other. It is preferred that the fluidic cylinder is a pneumatic cylinder or a hydraulic cylinder. In case of the pneumatic cylinder the yaw damper uses compressed gas, for example, CO2, NOx or air, as fluid and in case of the hydraulic cylinder the yaw damper uses compressed hydraulic oil as fluid. It is also conceivable that the yaw damper comprises a plurality of fluidic cylinders, each connected to the frame and the base or the chassis of the railway vehicle. It is further preferred that the fluidic cylinder is a synchronized cylinder, in which the volume of fluid flowing in and out of the different chambers during operation is constant. Synchronized cylinders comprise, for example, a specific piston rod, which extends throughout the whole cylinder during all operational positions of the piston. Such a specific cylinder may comprise one piston rod or two rods, which are arranged on both sides of the piston and extend through the first and the second chamber. Another designation for such a synchronized cylinder is thru-rod cylinder, double action or double rodded cylinder, because the rod extends through both chambers of the cylinder. According to this embodiment, the cylinder is a double rod synchronized cylinder. In other words, the volume of fluid flowing in and out of the first and second chamber of the synchronized cylinder is always the same and the piston and the piston rod move in both direction at the same speed. Synchronized cylinders can also be realized with a piston rod arranged only on one side of the piston. In this case, a special shape of the piston rod with internal bores ensures that the surface ratios are the same. The fluidic line connects the first chamber and the second chamber of the fluidic cylinder and provides therefore a reliable solution for movement of the fluid from the first chamber to the second chamber and vice versa. During operation of the railway bogie, the piston rod of the yaw damper moves linearly due to rotational movement of the railway bogie around the vertical steering axis. This linear movement causes fluid to flow out of the first chamber and into the second chamber and vice versa. The different components of the fluidic line control the friction of the fluid and therefore the damping of the yaw damper during operation of the railway vehicle. By controlling the fluid flow within the fluidic line or the plurality of the fluidic lines, it is therefore possible to control the damping of the yaw damper during its different operation modes.

Controlling the damping of the yaw damper is advantageously achievable when the yaw damper comprises a yaw damper control valve arranged between the first chamber and the second chamber. The yaw damper control valve forms thereby part of the fluidic line. The yaw damper control valve further comprises a valve actuator, which is configured to control the fluid flow from the first chamber to the second chamber for controlling the operation modes of the yaw damper. The fluidic line, in particular the yaw damper control valve, comprises for example a throttle, which is configured to be controlled by the valve actuator. By switching the valve actuator it is for example possible to change the throttle diameter or the throttle flow surface in the fluidic line, which changes the power, which is required to move fluid through the throttle. It is therefore possible to switch the yaw damper between the damped operation mode and the undamped operation mode by controlling the throttle arranged in the fluidic line via the valve actuator. The throttle or fluid throttle is a local narrowing of the fluidic line. In other words, the throttle is or comprises an orifice to reduce the available flow surface for the fluid. It is possible to control the flow surface of the throttle by, for example, adjusting the position of the throttle within the fluidic line. This is an advantageous reliable and simple solution to switch the yaw damper between the damped operation mode and the undamped operation mode.

In a preferred embodiment, the yaw damper control valve comprises a first fluidic valve line comprising a flow throttle and a second fluidic valve line forming a bypass of the flow throttle, wherein the valve actuator is configured to control the fluid flow in the damping operation mode along the first fluidic valve line and in the undamped operation mode along the second fluidic valve line. In other words, the valve actuator is configured to switch the fluid flow between the first fluidic line in the damped operation mode and the second fluidic line in the undamped operation mode. In the undamped operation mode, the fluid flows along the second fluidic valve line thereby bypassing the flow throttle. In this operation mode, the fluid is not throttled by the flow throttle, which provides the desired undamped movement of the frame around the vertical steering axis. In the damped operation mode, the fluid flows along the first fluidic valve line through the flow throttle. In this operation mode, the fluid is throttled by the flow throttle, which provides the desired damped movement of the frame around the vertical steering axis. According to this embodiment, the flow throttle itself is not switchable by the valve actuator, instead the passage surface or flow surface of the flow throttle is constant and the valve actuator controls along which of the fluidic valve lines the fluid flows. The yaw damper control valve comprising the two fluidic lines and the valve actuator create an advantageous reliable and simple solution to enable the yaw damper to dampen as desired in the damping operation mode and to enable undamped movement in the undamped operation mode.

An advantageous accurate and reliable control of the yaw actuator is achievable, when the railway bogie further comprises a control unit, which is configured to control the valve actuator. The control unit is, for example, a control unit specific for controlling the valve actuator or a control unit within the railway bogie, which additionally controls the valve actuator. The control unit is for example configured to control the valve actuator based on measurements of sensors of the railway bogie. For example, in case a specific sensor measurement reaches or surpasses a predefined threshold, which is for example determined by the control unit, the valve actuator is controlled by the control unit to switch from the undamped operation mode to the damped operation mode.

It is preferred that the control unit is further configured to (dynamically) control the valve actuator in dependence on at least one parameter of the railway bogie. In other words, in sensitivity of the yaw damper may be controlled I adapted in dependence on the at least one parameter of the railway bogie. For example, the yaw damper control valve is controlled by the valve actuator in dependence on the at least one parameter of the railway bogie. Further, the switching between the first fluidic valve line and the second fluidic valve line may be controlled in dependence on the at least one parameter of the railway bogie. In other words, the switching from the undamped operation mode into the damped operation mode is performed for example at different thresholds depending on the current parameters of the railway bogie. This provides an optimal system stability in dependence on at least one or a plurality of parameters of the railway bogie. The parameters, which may influence the controlling of the yaw damper may comprise load on the railway bogie, load distribution on the railway bogie, current velocity of the railway bogie, current orientation of the railway bogie with respect to the railway track, and I or current acceleration/deceleration of the railway bogie. Further parameters are also conceivable or a combination of parameters is also conceivable. The railway bogie may comprise specific sensors (e.g. load sensors, velocity sensors, acceleration sensors etc.), which provide the required parameter data. The current orientation is for example provided by the sensor assembly. The provided parameter data is e.g. processed, preferably by the control unit, and used to adapt e.g. thresholds in order to dynamically control the damping.

It is preferred that the control unit is configured to monitor the operation of the railway bogie. Monitoring the operation of the railway bogie may comprise monitoring via different sensors different functionalities of the railway bogie, like power supply, track alignment, rolling resistance, brake status etc. The control unit is according to this embodiment configured to control the valve actuator such that the fluid flows, within the yaw damper control valve along the second fluidic valve line in case a fault free operation of the railway bogie is monitored. The fault free operation is determined for example by comparing the sensor measurements with thresholds. In the fault free I normal operation of the railway bogie, the yaw damper is in its undamped operation mode, for example, the fluid of the yaw damper flows along the second fluidic valve line. The control unit is according to this embodiment further configure to switch the valve actuator such that the fluid flows within the yaw damper control valve along the first fluidic valve line in case a fault of the railway bogie is monitored. A fault is for example, a loss of power, a sensor failure, a detection of an emergency braking, a detection of an obstacle on the railway track, a break failure etc. In case a fault of the railway bogie or the railway vehicle is detected, which requires to dampen rotational movement of the railway bogie around the vertical steering axis, the control unit switches the valve actuator such that the fluid flows along the first fluidic valve line through the throttle, which causes the required damping of the railway bogie by the yaw damper.

In a preferred embodiment, the yaw damper comprises at least one pressure sensor, which is configured to provide a pressure signal, which is characteristic for the fluid pressure inside the yaw damper control valve, wherein the pressure signal is used to monitor the yaw damper during operation of the railway bogie. The pressure sensor is for example integrated in the fluidic line or in the yaw damper control valve. In another embodiment, the pressure sensor is integrated in the valve actuator. The pressure signal provided by the pressure sensor is, according to this embodiment, used to monitor the fluidic pressure inside the yaw damper. In case the fluidic pressure leaves a predefined threshold, by reaching or surpassing an upper boundary or by falling below a lower boundary, it is possible to detect a failure of the yaw damper itself. The pressure sensor provides therefore an advantageous reliable and simple solution to monitor the yaw damper.

In a further embodiment, the yaw damper comprises at least two pressure sensors, wherein one is arranged such that it provides a first pressure signal, which is characteristic for a pressure inside the first fluidic valve line, and wherein another pressure sensor is arranged such that it provides a second pressures signal, which is characteristic for a pressure inside the second fluidic valve line. According to this embodiment, it is possible to monitor the different fluidic valve lines of the yaw damper control valve, in particular with respect to pressure surveillance.

It is preferred that the railway bogie comprises a steering actuator connected to the frame and configured to swivel the frame during operation about the steering axis by a steering angle with respect to the base, wherein the steering angle is determined using the determined lateral position of the tread. The steering actuator is for example determined by a control unit. The steering actuator is, for example, connected to the base, to the connecting part or to the chassis of the railway vehicle. The steering actuator enables the railway bogie to steer around comers of the railway track using the determined lateral position of the tread. With the steering actuator, it is possible to keep the railway bogie always aligned with the railway track to avoid I reduce noise pollution and to reduce wear of the wheels. The steering actuator provides therefore an active steering system for the railway bogie, wherein the active steering system determines the steering angle based on the lateral position of the tread of at least one wheel and steers the railway bogie via the steering actuator using the determined steering angle.

During normal operation of the railway bogie, the steering actuator controls the rotational movement of the frame around the vertical steering axis and the yaw damper is in its undamped operation mode enabling the steering actuator to perform the desired reliable and precise steering. In case a fault is detected, for example by the control unit, the steering actuator is, for example, deactivated and the yaw damper is switched in the damped operation mode. In this scenario, the active steering system is transformed into a passive steering system, by the deactivation of the steering actuator and by switching of the yaw damper into its damped operation mode. In this safe operational mode, the railway bogie is advantageously protected from derailment and is brought into a safe operational mode. This safe operational mode is for example maintained until the fault is located and fixed. The yaw damper according to this embodiment provides advantageously the desired safety system for a steered railway bogie.

It is with respect to geometrical considerations and construction space requirements preferred, when the steering actuator and the yaw damper are connected to the frame on opposing sides of the railway bogie with respect to a running direction of the railway bogie. In this embodiment, the steering actuator and the yaw damper do not have any construction space conflict with each other. The steering actuator is, for example, arranged in front of the frame with respect to the running direction and the yaw damper is, for example, arranged behind the frame with respect to the running direction. In other embodiments, the yaw damper is arranged laterally next to the frame or within the frame of the railway bogie.

In a further embodiment, the steering actuator and the yaw damper are combined in one single steering-damping component of the railway bogie, wherein the steering-damping component is configured to function as the steering actuator during normal operation of the railway bogie, and to function as the yaw damper in the damped operation mode in case a fault of the railway bogie is detected. According to this embodiment, the yaw damper and the steering actuator are one assembly I one part, combined in the steering-damping component. During normal operation of the railway bogie, the steering-damping component steers the railway bogie based on the determined steering angle. In this case, the steering- damping component functions as steering actuator for active steering of the railway bogie. In case a fault is detected within the railway bogie or the railway vehicle, the steering via the steering-damping component is deactivated and the required damping of the movement around the vertical axis by the steering-damping component is activated. In this case, the steering-damping component functions as yaw damper for passive damping I steering of the railway bogie. The steering-damping component may comprise at least some of the above and hereinafter mentioned features to enable the desired damping. In particular, the steering-damping component may comprise a synchronized fluidic cylinder, and a fluidic engine, which is controlled for steering during normal operation mode. The synchronized fluidic cylinder may further comprise the valve actuator, which positions the flow throttle such that the desired damping is enabled. In the damped operation mode, the fluidic engine is stopped to enable the desired damping. This embodiment advantageously reduces the required installation space and further reduces the number of different parts, by combining functionalities.

In an embodiment, the valve actuator comprises a fail-safe mechanism, which is configured to switch the yaw damper automatically into its damping operation mode in case a fault of the railway bogie is detected. The fail-safe mechanism or safety valve comprises, for example, a magnetic valve or a spring valve, which switches automatically when a power connection to the valve actuator is interrupted or when no power is supplied to the valve actuator. Other fail-safe mechanisms are also conceivable. According to this embodiment, the valve actuator always switches into the dampen operation mode, even when a total breakdown of the railway bogie happens. According to this embodiment, the required safety mechanisms are activated in all possible scenarios. In a further aspect of the present disclosure, a railway vehicle is specified, which comprises the railway bogie as described above and hereinafter.

In a further aspect of the present disclosure, a method for damping movement around a vertical steering axis of a railway bogie is specified. The method typically comprises the steps of: providing a railway bogie as described above or hereinafter; monitoring the railway bogie for at least one fault during operation of the railway bogie; keeping the yaw damper in its undamped operation mode in case the railway bogie is fault free, and switching the yaw damper from the undamped operation mode into its damping operation mode in case a fault is detected for damping movement around the vertical steering axis.

According to this method, it is possible to switch the active steering system into a passive damped steering system in case of an emergency or in case a fault of the railway bogie or the railway vehicle is detected. Monitoring of the railway bogie may comprise to receive a heartbeat signal from different components of the railway bogie. In case the heartbeat signal is not received as expected, a fault may be detected. Another word for a periodically received signal (heartbeat signal) is for example a status signal or an active status signal. Monitoring of the railway bogie may comprise to compare a measured signal from a sensor to a threshold value or threshold function.

It is preferred that the steps of monitoring the railway bogie, keeping the yaw damper in its undamped operation mode and I or switching the yaw damper into its damping operation mode is performed by the control unit or by the fail-safe mechanism of the yaw damper control valve respectively.

It is further preferred that the step of switching the yaw damper into its damping operation mode and I or to control the yaw damper in its damping operation mode is performed in dependence on at least one parameter of the railway bogie. In other words, in sensitivity of the yaw damper may be controlled I adapted in dependence on the at least one parameter of the railway bogie. For example, the yaw damper control valve is controlled by the valve actuator in dependence on the at least one parameter of the railway bogie. Further, the switching between the first fluidic valve line and the second fluidic valve line may be controlled in dependence on the at least one parameter of the railway bogie. The parameters of the railway bogie may comprise: load on the railway bogie, load distribution on the railway bogie, current velocity of the railway bogie, current orientation of the railway bogie with respect to the railway track, and I or current acceleration/de- celeration of the railway bogie. The threshold for switching into the damped operation mode is for example adapted in dependence on the vehicle load and I or vehicle speed.

It is preferred that monitoring of a fault of the railway bogie comprises monitoring a loss of power of the railway bogie, monitoring a loss of power of the steering actuator, and I or monitoring a fault of the sensor assembly. In case the railway bogie or parts of the railway bogie loses power during operation I driving it is important that the railway bogie is decelerated and stopped safely, which is achievable by switching the yaw damper into the damped operation mode. Further, it is important that in case the sensor assembly does not work properly, the railway bogie is switched from the active steering into a passive steering, such that no wrong steering control signals are applied to the steering actuator, which could lead to a derailment of the railway bogie.

In order to stop the railway bogie in an emergency situation it is preferred that the method further comprises the steps of: deactivating, by the control unit, the steering actuator in case a fault is monitored, and I or activating a brake of the railway bogie in case a fault is monitored. In order to decelerate and to stop the railway bogie during operation it is additionally important to deactivate the steering actuator, such that the railway bogie is passively steered by the railway track. Further, it is important to activate the brake or the brakes of the railway bogie to decelerate and to stop the faulty railway bogie.

In a further embodiment, the method comprises the step of releasing or deactivating the brake after the railway bogie has come to a stop. The releasing of the brake is for example triggered manually. The brake is, for example, released to drag the railway bogie safely home in case of a total loss of power or railway bogie / railway vehicle malfunction.

In an embodiment, the railway bogie may comprise a maintenance mode, installation mode or emergency mode, in which the active steering system is switched into passive steering, by switching the yaw damper is in the damped operation mode and by releasing the brake, such that the railway bogie can be dragged safely towards a desired destination. The brake, which has previously been activated to stop the railway bogie when a fault was detected, is released I deactivated such that the vehicle can be dragged away in case the fault cannot be repaired on site. In this scenario, the yaw damper remains in the damped operation mode to provide the required passive steering. It is also conceivable that the brake is released I deactivated such that the railway bogie can continue its normal operation in case the fault has been resolved on site. In this scenario is the yaw damper switched back to the undamped operation mode and the steering actuator is activated such that the railway bogie can be actively steered again.

In a further aspect, a yaw damper for damping movement around a vertical steering axis of a railway bogie is specified. The yaw damper is configured to be coupled to a frame of the railway bogie, and to dampen movement of the frame around a vertical steering axis in a damped operation mode, and to enable essentially undamped movement of the frame around the vertical steering axis in an undamped operation mode. The yaw damper may comprise a control unit, configured to control the yaw damper, in particular to control the switching between the damped operation mode and the undamped operation mode. The yaw damper may comprise the features as described above and hereinafter with respect to the other aspects and embodiments of the present disclosure.

It is to be understood that both the foregoing general description and the following detailed description of present embodiments 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 bogie according to the disclosure;

Fig. 2 a first perspective view of a second variation of the 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 top view of the first variation of Fig. 1 ;

Fig. 6 a detail perspective view of the first variation of Fig. 1 ;

Fig. 7 a front view of a yaw damper according to a first embodiment; Fig. 8 a top view of the yaw damper according to the first embodiment;

Fig. 9 a perspective view of the yaw damper according to the first embodiment;

Fig. 10 a first detail perspective view of the yaw damper according to the first embodiment;

Fig. 11 a second detail perspective view of the yaw damper according to the first embodiment;

Fig. 12 shows a block diagram of the method according to the present disclosure; Fig. 13 shows a detail of one step of the block diagram of the method of Figure 12.

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 top view of the first variation of Figure 1. Figure 6 shows a detail perspective view of the first variation of Figure 1. Figure 7 shows a front view of a yaw damper according to a first embodiment Figure 8 shows a top view of the yaw damper according to the first embodiment. Figure 9 shows a perspective view of the yaw damper according to the first embodiment. Figure 10 shows a first detail perspective view of the yaw damper according to the first embodiment. Figure 11 shows a second detail perspective view of the yaw damper according to the first embodiment. Figure 12 shows a block diagram of the method according to the present disclosure. Figure 13 shows a detail of one step of the block diagram of the method of Figure 12.

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 of a railway track. 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 with respect 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 railway bogie 1 as shown in Figure 2 does not comprise, among other things, the connecting part 9.

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. Struts 29 are arranged between the base frame 23 and the wheel frame 24.

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

Figures 1 and 5 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. The Figures 1 and 5 further show a fluidic engine 44, which is configured to drive the steering actuator 16. The fluidic engine 44 is for example an electrical engine, which propels a hydraulic pump for controlling the steering actuator 16.

Figures 3 and 4 further show the sensor assembly 11 in detail. The sensor assembly 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 assembly 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 . 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, 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 of the front sensor unit 13 and I or of the back sensor unit 14 with respect to the rail. Movement of the frame 3, in particular movement of a swing arm 20 of the frame 3, which might affect the vertical position 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 of the respective sensor units 13, 14 may stay as static as possible during operation of the railway bogie 1 .

Figure 1 further show that each wheel 5 comprises an electrical engine 18 and a brake 19. The electrical engine 18 is configured to drive I accelerate, 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 , at least one sensor signal from the sensor assembly 12. The control unit 17 is further configured to determine the lateral position of the wheel 5 with respect to the rail using the received sensor signals. The control unit 17 may be configured to determine 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. The control unit 17 is further configured to determine a steering angle for steering of the railway bogie 1 on the railway track 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, 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 of a railway track is not always exactly constant throughout the railway track. Measuring the lateral position of more than one wheel 5 with respect to the corresponding rail increases therefore the steering performance, which advantageously reduces the wear of the wheels 5 and noise pollution during operation of the railway bogie 1 .

The Figures 1 and 2 further show four struts 29, which connect the base frame 23 with the wheel frame 24. The longitudinal axis of the struts 29 is arranged parallel to each other and is further arranged parallel with the running direction X in a resting state of the bogie 1 . The struts 29 are connected such with the base frame 23 and the wheel frame 24 that vertical movement between these two parts is, within certain limits, enabled (damped by the spring damping assembly 12) and that movement in the running direction X is inhibited. Movement of the steering actuator 16 results therefore in the desired direct and precise steering of the wheels 5, which is in particular advantageous in narrow curves.

The Figures further shows stops 31 , best visible in Figure 2, arranged on the base frame 23, wherein some of the stops 31 limit the movement of the base frame 23 with respect to the wheel frame 24. The other stops 31 limit the maximal rotation of the frame 3 around the vertical steering axis 4.

The Figures, in particular the Figures 5 and 6, further show a yaw damper 34 arranged on the railway bogie 1 . The yaw damper 34 is according to the embodiment as shown in the Figures arranged on the frame 3 and on the connecting part 9 of the base 2. The yaw damper 34 is arranged for damping rotational movement of the frame 3, comprising all the other parts of the railway bogie 1 , around the vertical steering axis 4. As best visible in Figure 5, the yaw damper 34 is arranged on the opposite side of the frame 3 with respect to the steering actuator 16. Figure 5 further shows that the connecting part 9 is formed symmetrically and extends beyond the frame 3 on both sides with respect to the running direction X until a connecting portion, which is configured to be connected to the steering actuator 16 and the yaw damper 34. The steering actuator 16 and the yaw damper 34 are, according to this embodiment, arranged symmetrically on the railway bogie 1. The Figures 5 and 6 further show that the steering actuator 16 and the yaw damper 34 are arranged rotatable on the connecting part 9. The Figures 7, 8, 9, 10 and 11 further show the yaw damper 34 and its components in detail. The yaw damper 34 comprises, according to this embodiment, a fluidic cylinder, for example a hydraulic or pneumatic cylinder. The fluidic cylinder is a synchronized cylinder having a piston rod extending throughout the cylinder. In other words, the fluidic cylinder is a thru-rod cylinder. The fluidic cylinder comprises a first chamber 35 and a second chamber 36. The fluid, for example compressed air or compressed hydraulic fluid, is configured to flow between the first and the second chamber 35, 36 using a fluid line 37. The fluid line 37 connects the first chamber 35 with the second chamber 36. The yaw damper 34 further comprises a yaw damper control valve 38, which is arranged in the fluid flow between the first chamber 35 and the second chamber 36. The yaw damper control valve 38 forms therefore part of the fluid line 37. The yaw damper control valve 38 is configured to control the fluid flow from the first chamber 35 to the second chamber 36 and vice versa. The yaw damper control valve 38 therefore controls, if the yaw damper 34 operates in the damped operation mode or in the undamped operation mode. As shown in the Figures, the yaw damper control valve 38 comprises a valve actuator 39, which is configured to control the fluid flow along a first fluidic valve line 40 and a second fluidic valve line 41 . The first fluidic valve line 40 and the second fluidic valve line 41 are two different fluid lines, implemented in the yaw damper control valve 38, for example via different boreholes, which, for example, have the same starting and ending point. The valve actuator 39 controls along which line the fluid flows during operation of the yaw actuator 34. The yaw damper control valve 38 further comprises in the first fluidic valve line 40 a flow throttle 42. The flow throttle 42 is a narrow passage within the first fluidic valve line 40, which reduces the passages surface of the first fluidic valve line 40. The fluid, which flows through the first fluidic valve line 40 requires more energy to pass through. In other words, when the fluid flows through the first fluidic valve line 40, the yaw damper 34 highly dampens the movement of the frame 3 around the vertical steering axis 4. When the fluid flows through the second fluidic valve line 41 , which bypasses the flow throttle 42, the yaw damper 34 does not dampen, or dampens only marginally, the movement of the frame 3 around the vertical steering axis 4 during operation of the railway bogie 1 . The flow actuator 39 controls when the fluid flows along the first fluidic valve line 40 or the second fluidic valve line 41 and controls thereby if the yaw damper 34 is in its damping operation mode or in its undamped operation mode. The damping power is among other things determined by the passage surface of the flow throttle 42. In an embodiment, the damping power is in a range from 2000 Nms/rad to 4000 Nms/rad, preferably in a range from 2500 Nms/rad to 3500 Nms/rad, more preferably at 3200 Nms/rad (^5000Ns/m at 0,8 m). The passive damping via the yaw damper 34 stabilizes the railway bogie 1 in critical I dangerous situation, in which for example, a power supply to the railway bogie 1 is interrupted.

In particular, the Figures 10 and 11 show the yaw damper control valve 38 in a half transparent manner. Therein, the different fluidic lines 40, 41 comprising the flow throttle 42 are visible. The Figures further show two pressure sensors 43, which are configured to provide a pressure signal, which is characteristic for the pressure inside the first fluidic valve line 40 and the pressure inside the second fluidic valve line 41. The Figures further show additional openings in the yaw damper control valve 38, which are, for example, used for maintenance purposes or which are used to set up the flow throttle 42 and / or the yaw damper control valve 38. In another embodiment, (not shown in the figures) the valve actuator 39 directly controls a moveable throttle. In this case, the operation modes of the yaw damper 34 can be controlled by changing the passage surface of the moveable throttle. In this embodiment, the valve actuator 39 and the moveable throttle form the yaw damper control valve 38.

The Figures further show the control unit 17, which is according to this embodiment also configured to control the valve actuator 39 for controlling the yaw damper 34. The control unit 17 is configured to monitor the railway bogie 1 and is configured to switch the yaw damper 34 into its damping operation mode in case a fault of the railway bogie 1 is detected.

Figure 12 further shows a block diagram, which illustrates a method for damping movement of the railway bogie 1 comprising the yaw damper 34.

In step SO, the railway bogie 1 is provided. In other words, the railway bogie 1 comprising the yaw damper 34 as disclosed above and I or hereinafter is used to guide a railway vehicle, like a tram, along a tram track.

In step S1 , the railway bogie 1 is monitored, for example by the control unit 17. In another embodiment, other control units or a plurality of control units is configured to monitor the railway bogie. Monitoring of the railway bogie 1 may comprise to compare sensor signals to thresholds or to control if an expected heartbeat signal is received. The yaw damper 34 is controlled based on the result of the monitoring. In step S2a, the yaw damper 34 is kept in the undamped operation mode, in case no fault is detected. In this case, the operation of the railway bogie 1 works normal.

In step S2b, the yaw damper 34 is switched in the damped operation mode, in case a fault is detected. In case a fault is detected, the railway bogie 1 is for example in a dangerous situation and it is required that adequate safety measures are initiated. It is preferred that switching of the yaw damper 34 in the damped operation mode or controlling of the valve actuator 34 is performed in dependence of a received parameter of the railway bogie, which for example determines a switching threshold. For example, the received parameter moves the threshold for the fault detection up or down due to load differences acting on the railway bogie 1 .

In step S3, the steering actuator 16 is deactivated in case a fault is detected. This step may be performed simultaneously to the step S2b. By deactivating the steering actuator 16, the railway bogie 1 becomes a passive steered railway bogie 1 , such that the railway bogie 1 is steered by the railway track.

In step S4, the brake 19 or the brakes 19 is / are activated in case a fault is detected. This step may also be performed simultaneously to the steps S2b and I or to the steps S3.

The steps S2a, S2b, S3 and S4 are performed by the control unit 17, which receives different sensor measurements for monitoring of the railway bogie 1. Based on the received sensor measurements the control unit 17 determines if the railway bogie 1 runs normally or if a fault of the railway bogie 1 is detected.

Figure 13 shows a detail of the block diagram of Figure 12. Figure 13 shows the step S1 and exemplary possible features of the railway bogie 1 , which could be monitored by the control unit.

In step S1a, monitoring the railway bogie 1 comprises to monitor a loss of power of the entire railway bogie 1 . In this case, it is important that the yaw damper 34 is switched in the damped operation mode such that the railway bogie 1 I the railway vehicle is kept safe.

In step S1 b, monitoring the railway bogie 1 comprises to monitor a loss of power of the steering actuator 16. In case the steering actuator 16 does not work as expected, it is important to switch the yaw damper 34 in the damped operation mode, to brake the railway bogie 1 and to deactivate the steering actuator 16.

In step S1 c, monitoring the railway bogie 1 comprises to monitor a fault of the sensor assembly 11 . In case the sensor assembly 11 does not work properly, it is impossible to steer the railway bogie 1 as desired along the railway track. In case a fault of the sensor assembly 11 is detected, it is important to switch the yaw damper 34 in the damped operation mode, to brake the railway bogie 1 and to deactivate the steering actuator 16.

Further parts or functionalities of the railway bogie 1 or the railway vehicle, which comprises the railway bogie 1 , may additionally or alternatively be monitored, for example by the control unit 17. 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

Bogie 25 Damper

Base 26 Spring assembly

Frame 27 First spring

Steering axis 28 Second Spring

Wheel 29 Strut

T read 30 Cover

Wheel rotation axis 31 Stop

Leveling actuator 34 Yaw damper

Connecting part 35 First chamber

Leveling axis 36 Second chamber

Sensor assembly 37 Fluid line

Spring damping system 38 Yaw damper control valve

Front sensor 39 Valve actuator

Back sensor 40 First fluidic valve line

Sensor bracket 41 Second fluidic valve line

Steering actuator 42 Flow throttle

Control unit 43 Pressure sensor

Electrical engine 44 Fluidic engine

Brake 45 Yaw piston rod

Swing arm X running direction pivot axis Y lateral direction

Swing arm spring Z vertical direction

Base frame

24 Wheel Frame