Method and device for determining changes in the longitudinal dynamic behavior of a rail vehicle

Abstract

Method for determining changes in the longitudinal dynamic behavior of a running gear of a rail vehicle for identifying a current driving state of the rail vehicle, wherein, by means of a control-technical observer (1), non-measurable variables characterizing the longitudinal dynamic behavior are reconstructed and evaluated from a known or metrologically determined input signal (u) and at least one measurement signal (y) of the observed rail vehicle as the observed real reference system (10) by a system model (20) of the rail vehicle, wherein the at least one measurement signal (y) of the observed rail vehicle and a corresponding reconstructed measurement signal (ŷ) of the system model (20) are compared, and the deviation determined by comparison is recursively tracked by a controller so that the determined deviation is minimized, characterized in thatthat the evaluation of the variables characterising the longitudinal dynamic behaviour includes a comparison of the variables of successive running gears or car bodies or wheelsets.

Description

[0001] The invention describes a method and a device for determining changes in the longitudinal dynamic behavior, in particular of a running gear, of a rail vehicle to identify a current driving state of the rail vehicle. Furthermore, the invention relates to a computer program product.

[0002] Changes in the longitudinal dynamic behavior of bogies in rail vehicles are due to varying wear conditions, relative movements between individual bogie components and changing environmental conditions, such as the ambient temperature, the temperature of individual bogie components, humidity, contamination. The effects mentioned predominantly result in two aspects relevant to longitudinal dynamics. Firstly, these are fluctuations in the coefficient of friction between a brake disc and a brake pad assigned to the brake disc or between a wheel and a brake block assigned to the wheel. Secondly, these are fluctuations in the adhesion between a wheel or wheelset and the rail on which the rail vehicle moves. The fluctuations in longitudinal dynamics can occur both during the acceleration and braking phases of the rail vehicle.

[0003] For this purpose, modern rail vehicles are known to incorporate a large number of sensors to record the forces or torques exerted during braking or acceleration. Knowledge of the acceleration or braking forces or acceleration or braking torques can be used to control or regulate braking or acceleration, in particular to prevent wheel skidding or locking and to effectively utilize the greatest possible adhesion between the wheel and the rail for braking or acceleration. However, installing a large number of sensors on a rail vehicle is expensive and requires considerable maintenance work, as they are exposed to a wide variety of environmental influences.

[0004] The determination of potential braking performance for rail vehicles is usually based on parameters that represent the worst-case expected condition of the vehicle in order to always guarantee sufficient safety reserves. This has the disadvantage that the calculated braking performance may, under certain circumstances, result in braking restrictions that complicate the economical operation of the rail vehicle. For example, an underestimated braking performance may lead to unnecessary speed restrictions on certain track sections.

[0005] DE 10 2011 113 093 A1 discloses a control device for a braking system of a rail vehicle, the braking system of which comprises a friction-dependent friction brake device. The control device is designed to determine a braking effect exerted during braking based on a brake pressure and at least one further parameter. This eliminates the need for brake force sensors or brake torque sensors to determine the braking effect. A further parameter, in particular a deceleration, a vehicle speed, or at least one wheel speed, is detected in order to determine the vehicle speed or, in the case of changes in the wheel speed, an acceleration or deceleration of the associated wheel.

[0006] WO 2015 / 128 147 A1 discloses a method that enables a practical determination of braking performance. This is achieved by determining a condition measurement value and using this condition measurement value and at least one additional measurement value to calculate the braking performance. This can be, for example, the wheel diameter, the vehicle mass, or the air pressure in the air suspension. The additional measurement value indicates the condition of the vehicle or a vehicle component.

[0007] Existing adhesion control methods are based on certain assumptions regarding operating conditions, such as rail contamination, climatic conditions, and the like, and optimize the adhesion between wheel and rail under these assumptions. While this can prevent high slip values, sanding is typically used to improve adhesion between wheel and rail. This, in turn, leads to increased wear on the wheels and rails.

[0008] WO 2015 / 136 117 A1 discloses a method in which traction is optimized in one mode and slip is reduced in another mode. In the latter mode, wear on the contact surface between the wheel and the guide rail is reduced.

[0009] These state-of-the-art methods therefore rely on knowledge of certain parameters. Depending on the chassis and chassis design, these methods may not be suitable for use. Due to sometimes rapidly changing friction conditions, manual, experience-based control of braking and drive force is also necessary to maintain braking distances and minimize wear on the wheelsets and rails, as well as on the drive and braking components.

[0010] DE 10 2008 038 753 A1 discloses a method for controlling a hybrid drive in a rail vehicle, in which an electronic route timetable is specified as route-section-related speeds via a train control unit. Before the start of the journey, the route-section-related drive types of the rail vehicle are predictively determined using the electronic route timetable. If, during operation, a position deviation of the actual position from a target position of the rail vehicle determined from the electronic route timetable is determined, a time reserve is calculated based on the position deviation, and the current drive type is maintained or changed depending on the time reserve. The route timetable, actual system variables, such asThe actual engine speed, actual engine power, actual fuel consumption, the status of an energy storage device, the actual position of the rail vehicle, as well as the oil, energy storage, cooling water, and converter temperatures, and the current altitude of the rail vehicle are input variables to a model designed as a predictive observer. The current state of the overall system is determined based on a model output.

[0011] DE 10 2008 028 264 B3 discloses a method for determining changes in the longitudinal dynamic behavior of a rail vehicle to identify the current driving state of the rail vehicle. In this method, measurement signals from a real system and a system model are compared. In the event of deviations, the system model is adapted to match the real behavior and minimize the deviations.

[0012] DE 10 2012 217 721 A1 discloses a device for a rail vehicle with a diagnostic system comprising an electronic diagnostic device and acceleration sensors arranged on a bogie of the rail vehicle for chassis diagnostics. The acceleration sensors for chassis diagnostics output acceleration signals to the electronic diagnostic device. The electronic diagnostic device is arranged on the bogie of the rail vehicle in order to connect a large number of acceleration sensors for chassis diagnostics to the electronic diagnostic device with minimal wiring effort and then evaluate their acceleration signals during chassis diagnostics.

[0013] It is an object of the invention to provide a method and a device with which changes in the longitudinal dynamic behavior of a rail vehicle, in particular of a chassis, can be determined in a simpler manner and independently of the chassis structure.

[0014] This object is achieved by a method according to the features of patent claim 1, a computer program product according to the features of patent claim 10 and a device according to the features of patent claim 11. Advantageous embodiments emerge from the dependent patent claims.

[0015] A method is proposed for determining changes in the longitudinal dynamic behavior of a running gear of a rail vehicle to identify a current driving state of the rail vehicle. Using a control-based observer from a known or measured input signal and at least one further measured signal of the observed rail vehicle as an observed real reference system, non-measurable variables characterizing the longitudinal dynamic behavior are reconstructed and evaluated by a system model of the rail vehicle. The at least one measured signal of the observed rail vehicle and a corresponding reconstructed measured signal of the system model are compared, and the deviation determined by comparison is recursively adjusted using a controller so that the determined deviation is minimized.The method is characterized by the fact that the evaluation of the variables characterizing the longitudinal dynamic behavior includes a comparison of the variables of successive bogies or car bodies or wheelsets.

[0016] By using a control-engineered observer, the proposed method requires only a few measurement signals. In particular, measurement signals already used in a conventional brake or drive control system can be used. The method allows characterization of the chassis dynamics in all drive and braking scenarios, such as emergency braking, service braking, and, with sufficient resolution of at least one measurement signal, even wheel slide protection intervention during friction-dependent braking.

[0017] The ability to utilize various sensor-determined measurement signals allows, depending on the chassis design, an easily accessible, thus low-maintenance, and cost-effective solution for determining changes in longitudinal dynamic behavior. The small number of sensors required to provide at least one measurement signal and the ability to position them flexibly minimize the effort required for sensors and the installation of connecting cables.

[0018] The method can be used to measure fluctuations in the longitudinal dynamics of rail vehicles, especially their bogies (e.g., bogies) and passenger trains. Application in freight car bogies is also possible, provided a power supply is ensured for the sensor units required to provide at least one measurement signal.

[0019] For example, information from leading bogies, car bodies, or wheelsets in the direction of travel of the rail vehicle, such as changes in wheel-rail contact conditions, can be processed as a prediction for subsequent bogies, car bodies, or wheelsets. By comparing the results of consecutive bogies, car bodies, or wheelsets, it is possible to determine whether changes in longitudinal dynamic behavior are track-related or have vehicle-related causes. Changes in longitudinal dynamic behavior that occur at different times on multiple bogies, car bodies, or wheelsets indicate track-related influences. These include, for example, weather-related changes in the friction coefficient at the wheel-rail contact.Changes in the longitudinal dynamic behavior, which, in contrast, only occur in individual running gears, car bodies or wheel sets, indicate vehicle-side influences of the respective running gear, car body or wheel set.

[0020] The method thus allows for continuous monitoring of wheel or brake unit wear, as changes in longitudinal dynamic behavior can be continuously detected and recorded.

[0021] A rail vehicle is generally understood to be a track-bound vehicle, such as a locomotive, a multiple unit, a railcar, a tram, a subway vehicle, a wagon, such as a passenger or passenger train and / or freight car.

[0022] A brake used to decelerate a rail vehicle can act on a brake disc of a wheel or wheelset, or on the running surface of a wheel (block brake). The brake can be operatively connected to a wheel, a wheelset, or a plurality of wheels. The brake can be constructed from a plurality of components or elements; in particular, the brake can comprise a brake disc, at least one brake pad acting with the brake disc, a brake caliper operatively connected to the brake pad, and a force generator. The brake caliper can be pivotally connected to a bracket by means of two bearing points, wherein the two bearing points are arranged at a bearing distance from each other. The brake disc has an axis of rotation that is at a distance from the (nearer) first of the two bearing points; this distance can be referred to as the installation dimension.The installation dimension can be understood as a horizontal distance relative to the installation. The bracket can be firmly connected to the chassis of the rail vehicle.

[0023] The brake can be applied in response to a brake signal. The brake signal can be a brake request signal or a brake request signal. When the brake is applied, a friction element of the brake, such as the brake pad or brake block, can counteract a force acting in the circumferential or wheel movement direction of the wheel or wheelset of the rail vehicle during wheel rotation. In this way, a braking torque can be generated from the brake pad to the brake disc and thus to the wheel, or from the brake block to the wheel.

[0024] The brake can be part of a pneumatic, in particular an electropneumatic, braking system or a hydraulic, in particular an electrohydraulic, braking system. Such a brake can comprise several brakes as described above. The brake can also be an electrically actuated brake, in which an electric braking current is converted into a braking force for actuating friction elements.

[0025] It is advisable to feed the input signal not only to the observed real reference system but also to the system model so that the system model, which simulates the observed real reference system, can reconstruct the measurement signal of the system model.

[0026] In a practical embodiment, the input signal and / or the at least one measurement signal are detected at one or more of the following components of the rail vehicle: at a car body; at a running gear of the rail vehicle; (at least one bogie of the rail vehicle;) at least one wheelset of the rail vehicle. The detection of the at least one measurement signal with a respective measuring sensor can thus take place at various locations on the rail vehicle, e.g., locations that, depending on the design of the rail vehicle or running gear, are particularly easily accessible and / or protected from environmental influences. This allows the device to be implemented in a particularly maintenance-friendly and cost-effective manner.

[0027] It is advantageous to simultaneously record at least one measurement signal on opposite sides of the bogie, car body, or wheelset. The combination of two sensor units at opposite locations on the bogie, car body, or wheelset allows the influences of cornering to be clearly separated from the longitudinal dynamic effects of braking or acceleration of the rail vehicle.

[0028] The input signal can be a brake pressure from a brake actuator or a brake current to generate a braking force that slows the rail vehicle. The braking force can then be determined as a function of a normal force generated by the pressure of a brake pad or brake block moved by the brake actuator against a brake disc or wheel, and of a friction coefficient. This makes it possible to determine changes in the longitudinal dynamic behavior during a braking process.

[0029] If a drive force or a motor current is processed as the input signal to generate a force accelerating the rail vehicle, a drive scenario in which the rail vehicle is accelerated can be evaluated.

[0030] As at least one measurement signal, a multitude of different measurement variables can be recorded using one or more measurement sensors. A combination of the same or different measurement signals is also possible.

[0031] The at least one measurement signal can be, for example, a speed or speed change of at least one wheel set. The metrological detection of a speed or speed change enables a highly precise determination of the variables characterizing the longitudinal dynamic behavior, since the speed or speed change is directly mechanically related to the variables characterizing the longitudinal dynamic behavior.

[0032] Alternatively or additionally, the at least one measurement signal can be processed as a strain of a component transmitting a longitudinal force, in particular a tension / compression rod, a pivot pin, a lemniscate link, or a wheel set guide. Strains can be detected, for example, by a measuring strip and other known sensor units.

[0033] Alternatively or additionally, a spring deflection in one or more suspension stages can be processed as the at least one measurement signal. Spring deflection can be measured, for example, using optical sensor units, a cable tension measurement, or inductively operating plunger sensors.

[0034] The method is particularly suitable for rail vehicles where quasi-static environmental conditions exist or the qualitative, temporal progression of the changes is known. Although it is particularly suitable for the bogies and wheelsets of passenger trains, it can also be used in freight car bogies, provided that a power supply to the device for determining changes in longitudinal dynamic behavior, in particular to the control unit and the at least one sensor unit, is ensured.

[0035] The method further provides a computer program product that can be loaded directly into the internal memory of a digital control unit and comprises software code sections that execute the steps of the method described herein when the product is running on the control unit. The computer program product can be embodied in the form of a CD-ROM, a DVD, a USB stick, or other storage media. The computer program product can also be in the form of a signal that can be loaded via a (wireless or wired) network.

[0036] The invention further provides a device for determining changes in the longitudinal dynamic behavior, in particular of a chassis, of a rail vehicle to identify a current driving state of the rail vehicle. The device comprises a control unit and at least one sensor unit for providing a respective measurement signal. The control unit is designed to reconstruct and evaluate non-measurable variables characterizing the longitudinal dynamic behavior using a system model of the rail vehicle, based on a known or metrologically determined input signal and the at least one measurement signal of the observed rail vehicle as the observed real reference system.The control unit is further designed to compare the at least one measurement signal of the observed rail vehicle and a corresponding reconstructed measurement signal of the system model and to recursively track the deviation determined by means of the comparison with a controller so that the determined deviation is minimized.

[0037] The device according to the invention has the same advantages as those described above in connection with the method according to the invention.

[0038] In summary, the present invention provides for the combination of various sensor signals in a control-engineered observer. Using the control-engineered observer, it is possible to unambiguously identify the current driving state of the rail vehicle by synthesizing a known or measured input signal and at least one measurement signal, as well as a model-based estimate of the dynamics of the rail vehicle. The dynamics of the rail vehicle's running gear determined using the model-based approach are recursively adjusted by comparing them with the measured signals, so that the calculated dynamics correlate with the actual dynamics of the rail vehicle. The method allows characterization of the running gear dynamics in all drive and braking scenarios, such as emergency braking, service braking, and wheel slide protection intervention during friction-dependent braking.

[0039] The invention is explained in more detail below using an exemplary embodiment. The figures show: Fig. 1 shows a schematic representation of a block diagram of a control observer as used in the method according to the invention; Fig. 2 is a graphical representation showing a comparison of an actual friction coefficient and a coefficient of friction determined by means of the method according to the invention as a function of time; and Fig. 3 a graph showing a time-dependent, translational longitudinal speed of the rail vehicle as a function of the Fig. 2 shows the friction coefficient curve.

[0040] The method described below for determining changes in longitudinal dynamic behavior is used in a rail vehicle not shown in detail in the figures. Such a rail vehicle has one or more links that are movably connected to one another. A coupling device is provided for connecting the vehicle links. Depending on the design of the rail vehicle, each vehicle link can have two bogies, each with at least one wheelset. Alternatively, a rail vehicle with two vehicle links can also have three bogies, each with at least one wheelset. Typically, a bogie comprises two wheelsets. The wheelsets of the bogies each have wheels that run on a rail.

[0041] A plurality of sensor units (in short: sensors) can be provided on the rail vehicle. The rail vehicle can, for example, have one or more sensors for determining the vehicle speed and / or an acceleration or deceleration of the rail vehicle in the vehicle's longitudinal direction. The acceleration can be a positive acceleration as a result of a force accelerating the rail vehicle or a negative acceleration as a result of a braking force decelerating the rail vehicle. The (positive or negative) acceleration can be an overall acceleration of the rail vehicle. If an acceleration sensor is attached to a respective vehicle section, the acceleration can also be the respective (positive or negative) acceleration of the respective vehicle section. The acceleration can, for example, be a deceleration occurring on a running gear or on a car body of the rail vehicle.Acceleration can be determined based on speed data. Deceleration can be inferred from a temporal progression and / or a change in vehicle speed. The deceleration can be determined by observing the speed progression in time intervals shorter than the duration of a (positive or negative) acceleration. Thus, at least one acceleration sensor can be assigned to each vehicle limb and / or each chassis. Such sensors are often provided for monitoring driving conditions, so existing sensors can be used to determine the (positive or negative) acceleration.

[0042] To determine the vehicle speed, for example, a radar system, an optical sensor device and / or a communication device for receiving satellite data can be provided, to which a control device of the rail vehicle can be or is connected.

[0043] In addition, sensors can be provided to determine the rotational speeds and speed changes of at least one wheelset. Determining the wheel speed can be used, for example, to determine braking effect and is already installed in many rail vehicles. It is also conceivable that the vehicle speed is determined based on wheel speed data. In this case, a speed associated with the assigned wheel or wheel axle, for example, a rotational speed or wheel speed, can be determined from wheel speed data assigned to individual wheels or wheel sets. In addition to wheel speed data, the radius of the wheel can be taken into account.

[0044] From a wheel speed change of at least one wheelset, for example, it can be concluded that there is a (positive or negative) acceleration in an associated wheelset or an associated wheel axle.

[0045] Such a rail vehicle can be equipped with sensor units for detecting pitching movements of individual components around the vehicle's transverse axis. Such sensor units are preferably assigned to a respective transverse axis of the vehicle. For example, acceleration sensors can be used for this purpose, which detect acceleration around the vehicle's transverse axis.

[0046] The rail vehicle can also be equipped with at least one sensor unit that detects the spring travel in each suspension stage of a vehicle component of the rail vehicle. Such sensors can be implemented optically, by means of cable tension measurement, or by inductive plunger sensors.

[0047] Longitudinal force sensors, such as strain gauges, can be used to measure the strain of longitudinal force-transmitting components. Such a sensor unit can be assigned to a respective push / pull rod, a respective pivot pin or lemniscate link, or a respective wheel set guide.

[0048] Furthermore, brake pressure sensors or brake current sensors and / or brake effect sensors such as brake force or brake torque sensors can be provided for the bogies or the friction brake devices of a friction-dependent friction brake device arranged on the bogies. In general, a brake pressure sensor or brake current sensor can be considered to be associated with a friction brake device if it is capable of detecting a brake pressure or brake current that individually actuates the friction brake device. A brake force sensor or a brake torque sensor can be considered to be associated with a friction brake device or a wheelset to be braked by the friction brake device if it is capable of detecting a brake force exerted by the friction brake device or a corresponding brake torque.

[0049] Using the control-engineering observer described below, it is possible to model the frequently different bogie structures in a rail vehicle train using a uniform model-based algorithm. A clear estimation of the bogie dynamics of the rail vehicle can be ensured by combining a number of measurement signals.

[0050] Fig. 1 shows a block diagram of the basic structure of a control-engineering observer 1, with the aid of which the method for determining changes in the longitudinal dynamic behavior of the rail vehicle is carried out. In a manner known to those skilled in the art, the control-engineering observer 1 consists of a system model 20 of the rail vehicle and a unit 26 for weighting the comparison result of the system model 20 and an observed real reference system 10. The dynamics of the observed real reference system 10, i.e. the observed rail vehicle, are influenced by an input signal u, which is fed to the observed real reference system 10 at a first input 11. The input signal u is a measurable signal. In the case of braking of the rail vehicle with friction brakes, the input signal u can correspond to a brake pressure of the braking system / device.If braking is performed using an electric brake, the input signal can be a braking current to generate a braking force that slows the rail vehicle. If, on the other hand, a change in longitudinal dynamic behavior due to acceleration is to be detected, the input signal u can be a drive force or a motor current to generate the force that accelerates the rail vehicle.

[0051] The dynamics of the observed real reference system 10 are described by states x. x can be a vector with a multitude of different states. Since the observed real reference system 10 is equipped with at least one sensor unit as described above, at least one measurement signal y is provided at an output 13. y can be a vector whose number of vector entries corresponds to the number of (real) measurement signals. The measurement signals acquired can originate from sensor units of the same and / or a different type.

[0052] The observed real reference system 10, i.e. the rail vehicle, can also be excited by non-measurable disturbances z. These non-measurable disturbances z are fed to the reference system 10 at a second input 12. Disturbance z is understood to mean all those influences that affect the coefficient of friction between wheel and rail and / or between brake pad and brake disc and / or brake block and wheel. This also includes those influences that affect the friction radius, i.e. the point of application of a brake pad on the brake disc. Furthermore, a changing total weight due to a changing loading condition of the reference system 10, i.e. the rail vehicle, can occur as a disturbance z.

[0053] The system model 20 represents a model of the dynamic behavior of the reference system 10, i.e., the rail vehicle. The system model 20 can be formed, for example, by software. The system model 20, like the reference system 10, is controlled by the input signal u. The input signal u is fed to the system model 20 at a first input 21. The system model 20 determines values ​​for the at least one reconstructed measurement signal ŷ, which is made available, e.g., likewise as a vector, at a first output 22. Each reconstructed vector entry of the measurement signal ŷ is assigned to a metrologically determined vector entry of the measurement signal y of the reference system 10.

[0054] Since the system model 20 generally cannot represent the entire dynamics of the reference system 10 and, in addition, the reference system 10 is influenced by the non-measurable disturbance variables z, the dynamic behavior of the system model 20 deviates a priori from the actual behavior of the reference system 10. For this reason, a comparison is made of the at least one reconstructed measurement signal ŷ (i.e., its vector entries) with the at least one metrologically determined measurement signal y (i.e., the associated vector entries), which is made available at the output 13 of the reference system 10. These two measurement signals are fed to a comparator 25, which calculates the difference. The deviation (y-ŷ) is fed to a unit 26 for weighting the comparison result. The feedback of the deviation (y-ŷ), weighted with L, is made available to the system model 20 at a second input 24.The weighting by unit 26 is performed such that the behavior of the reconstructed measurement signal ŷ calculated by the system model 20 agrees with the actually measured at least one measurement signal y after a certain time, i.e., the deviation becomes zero after a certain time. This process is automated and performed recursively.

[0055] The desired dynamic variables x̂, which represent the longitudinal dynamic behavior of the rail vehicle, can then be read out at a second output 23 of the system model 20. These are, for example, non-measurable variables such as speeds and friction coefficients between wheel and rail and between brake pad and brake disc, braking forces and braking torques, and the like. Furthermore, the disturbance variables ẑ can be read out at a third output 27 of the system model 20.

[0056] The Fig. 2 and Fig. 3 shows the result of the procedure based on simulation results for a braking process. Fig. Figure 2 shows the friction coefficient µ(t) between brake pad and brake disc as a function of time t. Fig. Figure 3 shows the change in longitudinal velocity v(t) over the same period of time. The period shown is from t = 30s to t = 80s. It is assumed that a rail vehicle wheelset is braked with a constant brake pressure during the period from t = 35s to t = 80s. Fig. 2 and Fig. 3 curves shown with solid lines z µ , x v show the temporal progression of the route model, while the broken lines show calculated values zμ^,xv^ of the system model 20. In this example, it is assumed that in addition to the wheelset speed ω, the translational longitudinal speed v of a wheelset is measured, ie is available as measurement signals y at the output 13 of the reference system 10.

[0057] Fig. Figure 2 shows the temporal progression of the coefficient of friction µ between the brake pad and the brake disc, as it results from fluctuating influences during braking with constant brake pressure. The depicted fluctuation of the actual coefficient of friction (solid line) is represented by the above-described feedback of the deviation (y-ŷ) and the selected design of unit 26 for weighting the comparison result from the system model (by numerical simulation, tests, or calculation). The longitudinal velocity v as one of the states x of the reference system 10 and as one of the variables x̂ characterizing the longitudinal dynamic behavior of the system model 20 is shown in Fig.3. The feedback of the deviation (y-ŷ) of the measured signal y available at output 13 and the reconstructed measurement signal ŷ at the first output 22 of the system model results in the movement calculated by the system model 20 correlating with the actual system behavior.

[0058] The effect of the reduced coefficient of friction µ between t = 40s and t = 70s leads to the longitudinal speed v decreasing less rapidly in the mentioned time range, which leads to an extended braking distance and can therefore pose a safety risk.

[0059] In the example shown, the application of the method allows the required braking pressure to be determined based on the calculated friction coefficient µ between the brake pad and the brake disc, which is necessary to maintain a prescribed braking distance. This determination is performed in a control unit, the design and method of which are not the subject of the present invention.

[0060] Furthermore, knowledge of the friction coefficient µ allows conclusions to be drawn about the wear condition of the brake pad, which enables condition-based maintenance.

[0061] The information thus obtained from leading wheelsets, bogies, or car bodies can be made available in a suitable manner as a prediction for subsequent wheelsets, bogies, or car bodies. This evaluation also takes place in a control unit and is not the subject of this discussion. By comparing the results from successive wheelsets, bogies, or car bodies, it becomes clear whether the changes are due to track-related influences or vehicle-related effects. Changes detected at multiple sensor units with a time delay indicate track-related influences. Fluctuations that only occur in individual sensor units, on the other hand, indicate vehicle-related influences. List of reference symbols 1 control engineering observer 10 observed real reference system 11 first input for input signal u 12 second input for interference signal z 13 Output for measuring signal y 20 System model 21 first input for input signal u 22 first output for reconstructed measurement signal ŷ 23 second output for observed quantity(s) x̂ 24 second entrance 25 comparators 26 Unit for weighting the comparison result 27 third output for reconstructed disturbance(s) ẑ u Input signal y measurement signal x state variable ŷ reconstructed measurement signal x̂ reconstructed state variable z disturbance variable ẑ reconstructed disturbance

Claims

[1] Method for determining changes in the longitudinal dynamic behavior of a running gear of a rail vehicle for identifying a current driving state of the rail vehicle, wherein, by means of a control-technical observer (1), non-measurable variables characterizing the longitudinal dynamic behavior are reconstructed and evaluated from a known or metrologically determined input signal (u) and at least one measurement signal (y) of the observed rail vehicle as the observed real reference system (10) by a system model (20) of the rail vehicle, wherein the at least one measurement signal (y) of the observed rail vehicle and a corresponding reconstructed measurement signal (ŷ) of the system model (20) are compared and the deviation determined by comparison is recursively adjusted by a controller so that the determined deviation is minimized, characterized bythat the evaluation of the variables characterising the longitudinal dynamic behaviour includes a comparison of the variables of successive running gears or car bodies or wheel sets. [2] Method according to claim 1, characterized by that the input signal (u) is additionally fed to the system model (20). [3] Method according to one of the preceding claims, characterized by that the input signal (u) and / or the at least one measurement signal (y) are detected at one or more of the following components: - a car body; - a running gear of the rail vehicle; - at least one bogie of the rail vehicle; - at least one wheelset of the rail vehicle. [4] Method according to claim 3, characterized by that at least one measuring signal (y) is recorded simultaneously on opposite sides of the running gear or the bogie or the wheelset. [5] Method according to one of the preceding claims, characterized by that a brake pressure of a brake actuator or a brake current is processed as the input signal (u) to generate a braking force that slows down the rail vehicle. [6] Method according to one of the preceding claims, characterized by that a driving force or a motor current is processed as the input signal (u) to generate a force accelerating the rail vehicle. [7] Method according to one of the preceding claims, characterized by that a speed or speed change of at least one wheel set is processed as the at least one measuring signal (y). [8] Method according to one of the preceding claims, characterized by that an extension of a component transmitting a longitudinal force, in particular a tension / compression rod or a pivot pin or a lemniscate link or a wheelset guide, is processed as the at least one measuring signal (y). [9] Method according to one of the preceding claims, characterized by that a spring travel in one or more suspension stages is processed as the at least one measurement signal (y). [10] A computer program product which can be loaded directly into the internal memory of a digital control unit and which comprises software code sections which carry out the steps according to any one of the preceding claims when the product is run on the control unit. [11] Device for determining changes in the longitudinal dynamic behavior of a running gear of a rail vehicle for identifying a current driving state of the rail vehicle, comprising a control unit and at least one sensor unit for providing a respective measurement signal (y), wherein the control unit is designed to reconstruct and evaluate non-measurable variables characterizing the longitudinal dynamic behavior by means of a control-technical observer (1) from a known or metrologically determined input signal (u) and the at least one measurement signal (y) of the observed rail vehicle as an observed real reference system (10) by a system model (20) of the rail vehicle, wherein the control unit is further designed toto compare the at least one measurement signal (y) of the observed rail vehicle and a corresponding reconstructed measurement signal (ŷ) of the system model (20) and to recursively track the deviation determined by means of the comparison with a controller so that the determined deviation is minimized, , characterized by that the control unit for evaluating the variables characterising the longitudinal dynamic behaviour is further designed to compare the variables of successive running gears or car bodies or wheel sets.

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