Marcusson, Lage (Gimlegatan 11, V�ster�s, S-723 55, SE)
Lundmark, Jan-erik (Sj�liden 30, Vreta Kloster, S-590 77, SE)
Marcusson, Lage (Gimlegatan 11, V�ster�s, S-723 55, SE)
|1.||A method for steering at least one wheel axle/bogie (7) associated with a vehicle in a trackbound train when the train passes over a track section, wherein the respective vehicle in the train comprises bogies and a car body resting thereon, means (6) for mechanically rotating the wheel axle/bogie (7) in relation to the car body, members (12,14, 15) for indicating the geometry of the track and a control system (21,4,5) for steering the rotation of the wheel axle/bogie in dependence on the geometry of the track, characterized in that the position of the train along a track route is determined pointbypoint by the train being equipped with means (13) for detecting said position, by registering the curve geometry of the track when the train is running over a track section from the determined position (n) by means of members (12,14,15) for determining the curve geometry and storing it in real time as a sequence of measured values describing the curve geometry of said track section in an electronic memory (M), and by using at least the latest sequence of curvegeometry measured values for the track section, stored in the memory (M), for controlling the rotation of the wheel axle/bogie (7) during a subsequent passage of the train, in the same direction, along the same track section.|
|2.||A method according to claim 1, characterized in that consecutive sequences of measured values registering curve geometry data from the consecutive running of the train in the same direction over one and the same track section are stored in the memory (M), whereby a mean value of the curve geometry data of the track section from at least two last stored consecutive sequences of measured values is used for controlling the rotation of the wheel axle/bogie (7) during passage through the track section.|
|3.||A method according to any of the preceding claims, characterized in that the position of the train along the route is determined pointbypoint by the train being equipped with devices (13) which read position transducers placed along the route.|
|4.||A method according to any of claim 1 or 2, characterized in that the position of the train is determined by the train being equipped with devices (13) for determining the posi tion, wherein the position of the train is read by utilizing satellite navigation (GPS).|
|5.||A method according to claim 1, characterized in that the wheel axle/bogie is adapted to be steered to substantially coincide with the radius of the track at that position of the track which the wheel axle/bogie instantaneously traverses.|
|6.||A method according to claim 1, characterized in that there is read into the memory (M) information about track sections where the steering of the wheel axle/bogie (7) is to be inactive.|
|7.||A method according to claim 1, characterized in that there is read into the memory (M) information about track sections where the wheel axle/bogie is steered to assume a position perpendicular to the track.|
|8.||A device for carrying out the method according to claim 1 for steering at least one wheel axle/bogie (7) associated with a vehicle in a trackbound train when the train passes through a track section, wherein the respective vehicle in the train comprises bogies and a car body resting thereon, means (6) for mechanically rotating the wheel axle/bogie (7) in relation to the car body, members (12,14,15) for indicating a track curve, and a control system (21,4,5) for controlling the rotation of the wheel axle/bogie in geometry of the track, characterized in that the train is equipped with devices (13) for determining pointbypoint the position (n) of the train along a route, that the train is equipped with members (12,14,15,16,17,18) for deter mining the curve geometry of a track section from the deter mined position by detecting a sequence of sampled measured values in real time of curvegeometry data for the track section when the train is running over said track section, an electronic memory (M) which stores said sampled sequence of measured values of the curve geometry of the track sec tion, and a second referencevalue calculator (21) which, while using at least the latest sequence of the curve geometry measured values of the track section stored in the memory (M), calculates a reference value for the angular adjustment of the wheel axle/bogie for controlling the rotation of the wheel axle (7) during a subsequent passage of the train, in the same direction, along the same track section.|
|9.||A device according to claim 8, characterized in that the determination of the curve geometry of a track section is carried out by means of devices (14,16) for detecting the curvature of a track curve, and by means of devices (15,17) for detecting the rail superelevation angle of the track curve.|
|10.||A device according to claim 9, characterized in that the curvature of a track curve is detected by means of a gyro (14).|
|11.||A device according to claim 9, characterized in that the rail superelevation angle of a track curve is detected by means of a gyro (15).|
|12.||A device according to claim 8, characterized in that the position of the train is detected by a position sensor (13) on the train reading a position transducer located along the route.|
|13.||A device according to claim 8, characterized in that the position (n) of the train is detected pointbypoint by providing the train with a position sensor (13) which con sists of a receiver for satellite navigation, whereby the position of the train is, for example, read at predetermined points or at certain predetermined intervals.|
|14.||A device according to claim 8, characterized in that the device (6) for mechanically rotating the wheel axle/bogie (7) comprises hydraulic or electric devices.|
BACKGROUND ART In the field of train technology it has long been desirable to steer the wheel axles of a railway vehicle to align radially to the track both in track curves and along straight tracks. The reason for this is that the running characteristics of such a vehicle may be considerably improved if steering is executed. It is especially important to be able to steer the wheel axles if the speed of the vehicle increases, for example when using high-speed trains equipped with or without tilting technology.
When a railway vehicle is run along a track, the necessary conicity on the running surfaces of the wheels causes wheel undercarriages with non-steered wheel axles when running along straight tracks to describe a winding or wave-like movement. When negotiating curves, incorrectly aligned wheel axles cause the angle of application of the wheels with the rails to become greater than desirable. These conditions lead to drawbacks which increase the wear on the wheels of the vehicle and the rail because of unnecessarily great lateral forces between wheels and rail. The rail may get into contact with the wheel flanges and a risk of derailment may arise. The train comfort is also reduced when the roll
properties deteriorate. The disturbances also give rise to disturbing noise from wheels and rail. The wear on wheels and rail is caused, inter alia, by the creep which arises due to the lateral forces, which create frictional movements between the wheels and the rail when the wheel axle in in- correctly aligned in relation to the track.
Various ways of solving the problems described above have been presented over the years. The existing solutions are based on various principles which may primarily be divided into systems with passive steering and systems with active steering, respectively. Passive steering is obtained, for example, in those cases where the running surfaces of the wheels are conically shaped, whereby a wheel axle with such wheels strive to assume a position along the radius of the track. This is also usually called self-steering and occurs both in single-axle bogies and in multi-axle bogies in a number of different variants. As an example of self-steering in a single-axle bogie, reference is made to the patent document WO 94/07728. One problem which may be difficult to solve in case of self-steering is to obtain a damping of the self-steering which is adapted to the movement of the vehicle along both straight tracks and curves.
Another commonly used principle for wheel steering which may be counted among the passive systems consists of those methods in which an angular adjustment between two car bodies with the aid of mechanisms forces wheels axles to adjust themselves radially to the track. An example of such a device is presented in the patent document of EP 295462 B.
A principle for active steering of wheels in a railway vehicle is described in the patent document EP 0 374 290.
This publication describes a device which creates a steering signal when the longitudinal axis of the vehicle starts deviating from the course of the track. The steering signal in its turn influences individual wheels to be steered, with
an adapted time delay, to align themselves radially to the track.
A disadvantage with all of the methods described above is that they do not solve the most important problem, that is, to steer the first axle or axles of the train to align them- selves radially to the track. This is particularly noticable when a train operates a track route at a high speed. The known passive and active methods suffer from a time lag during steering of the wheel axles, which implies that the leading wheel axles cannot be steered in the desirable way.
At the same time, certain of the known solutions for wheel steering involve complicated mechanical devices for transmission of steering forces to bogies.
The present invention discloses a device by which the diffi- culties described are avoided.
SUMMARY OF THE INVENTION One aspect of the present invention is the formation of a second reference value signal which is the basis of and is used in a control system which monitors the steering of at least one wheel axle in a vehicle which is comprised in a train when the train travels along a track route. To achieve this in a wheel axle belonging to a vehicle in a trackbound train when the train passes along the route, where the res- pective vehicle in the train comprises bogies equipped with one or more wheel axles and a car body resting on the bogies, further devices for mechanical rotation of at least one wheel axle in relation to the car body, devices for indication of track curves and a control system for steering at least one wheel axle radially to the track in dependence on the geometry of the track curves, the position of the train along the route is determined point-by-point in that the train is equipped with devices for detecting this position, that the curve geometry of the track when the
train travels over a track section from the determined position is registered and stored on-line as a sequence of measured values describing the curve geometry of the mentioned track section in an electronic memory, and in that curve-geometry data about the track section, stored in the memory, from at least one journey previously made by the train along the track section in the same direction are used for steering at least one wheel axle to be aligned radially to the track within the track section.
Data about the geometry of each curve track along a route are stored in the train computer in a database in the form of sampled values for the track curvature and the rail superelevation angle for each track curve. These data have been formed by measurement and have initially dynamic disturbances caused by the irregularities of the track. The disturbances are eliminated or reduced by filtering, whereby data are given a certain, approximately known, delay in relation to the actual track geometry. In connection with storage and updating, track-geometry data for the approxi- mately known time delay are compensated. Stored data about the track curve, here called reference-value profile for the track curve (i. e. sampled values of the curvature and rail superelevation of the curve) are updated for each time the train passes through the same track curve.
By using stored data on the geometry of the track for the formation of a second reference-value signal which substan- tially without delay controls the steering of at least one of the wheel axles in the vehicles in the train, the steer- ing of also the first and second leading wheel axles in the train may be initiated without delay upon a change of the direction of driving of the train in dependence on the data about the geometry of the track curve which are stored in the database in the train computer from the preceding passage of the train, or data from several preceding passa- ges through the same track curve. This eliminates the incon-
venience as described above if the vehicles are driven with non-steered wheel axles.
Another object of the invention is that the method elimi- nates the need of storing ideal data, known in advance, about the track geometry for each track section of the route, since track-geometry data for a route according to the invention are continuously registered and stored, where- by changes in the track geometry are noted by the train com- puter for use for subsequent travel by the train along the route. This eliminates a train's need of constant access to data sequences with track-geometry data available in some form of replaceable memory modules which have been provided with the latest track-geometry data about a route.
Further, the train may be provided with transducers for forming a first reference-value signal for instantaneous steering of wheel axles in a vehicle in the form of an accelerometer for sensing the lateral acceleration and transducers (gyros or position transducers sensing the track cross-level) for detecting the rail superelevation ramp of the curve. This first type of reference-value forma- tion is chosen if there are no stored track-geometry data in the database of the train (e. g. the first time a train runs along a certain route). It may also be chosen by the train personnel, during all of or parts of the route, for example if it is known that the track geometry has undergone major changes since last time the train run over and stored track- geometry data about all of or parts of the route in question.
The train is equipped with a position sensor, whereby the position of the train point-by-point may be determined by reading position transducers located along the route. The position transducer transmits to the train computer informa- tion about the track section into which the train enters.
The current position of the train within the track section
is then calculated as a function of the train speed from the read position on the line.
Position transducers along the route may consist of special signal transducers, or be integrated with existing signal transducers, so-called balises, along the track. The posi- tion indications may include information about the route on which the train is running as well as information as to where along the line the train is located. Alternatively, the train driver may indicate the route manually.
Another way of determining the position of the train along a route is given by the possibility of utilizing satellite navigation, Global Positioning System (GPS). By connecting a GPS receiver to the train computer, the position of the train may be read continuously. In this way, a track section along the track may be identified, for example, by the posi- tion for the starting-point of the track section being stored in the train computer, whereby the reference-value profile for the corresponding track section may be read from the computer memory, and be written into the computer memo- ry, respectively, when the GPS receiver detects a train position which coincides with the starting-point of the track section.
The first time a train passes over a certain route, the current curve geometry is measured, processed and stored in a memory in a train computer which is part of the control system of the train. At the same time, this information about the curve geometry in real time is used for steering the wheel axles instantaneously.
The geometry of a curve is determined by measuring two variables, namely, the course of the curvature of the curve and the course of the rail superelevation.
The curvature (p (s) = 1/R (s)) of the curve, that is, the inverse of the curve radius R (s), as a function of the longitudinal position (s) from the starting-point (s=0) of a track section or the starting-point (s=0) of a curve is determined by measuring the angular velocity (dT/dt) around a vertical axis and dividing this angular velocity by the instantaneous overall travel speed (v) The rail superelevation angle ( (s)) of the curve as a function of the longitudinal position (s) is determined by the time integral of the angular velocity (d (p/dt), measured around a longitudinal axis, that is, The two angular velocities may be measured by gyros, suitably located in the first bogie of the train. The disturbances on the signals must be filtered off, which provides signals with approximately known delays.
Sampled values of the curvature pand the rail superele- vation angle (p, respectively, are stored online in the database of the train computer as an updated reference- value profile for each track section of the covered route with the given starting position of the track section as starting-point, whereby the reference-value profile will contain the latest curve-geometry data of each track section. Before being stored, sampled values are compen- sated for the approximately known time delay which is obtained during the filtering.
The wheel axle steering may, for example, be controlled to be proportional to the lateral acceleration (ay). The
lateral acceleration is determined approximately by the following expressions, where g is the gravitational accule ration The second time, and subsequent times, that the train runs over a certain route, the previously measured and stored curve geometry for curves within a certain track section is used to calculate in advance, in a special calculating unit, correct reference values for steering of the wheel axles within the track section. This calculation is made as a function of the position of the train, and of its various cars, along the track within the track section. The concept curves also comprises straight tracks, where the steering of axles is to have the effect of aligning the wheels on one axle parallel to the track. Alternatively, the absence of curves, that is, that the train computer does not con- tain any information about an approaching curve, may be used for resetting the wheel steering, that is, setting the wheels parallel to the track Since the delay in the stored signals is approximately known, this can be taken into consideration in the calcula- tion, and the steering of the respective axle may take place at the correct time for all vehicles of the train.
The system receives a self-correcting function for changes in curve-geometry data, as from the running which takes place immediately after the changed track-geometry data were measured and stored. To reduce the dependence on acci- dental occurrences during an individual running, the mean value of the two or three immediately preceding stored reference-value profiles may alternatively be used.
The concept wheel axle in this specification means a con- struction which comprises an axle with a wheel set and a
primary suspension system which may be of a self-steering type. The wheel axle may be steered by rotating a frame, in which the wheel axle is fixed. This may also take place by rotating a wheel bogie which comprises the wheel axle. When steering by rotating a whole bogie, more than one wheel axle may be rotated simultaneously by means of the same mechanical device.
If a fault should occur in the control system for the wheel axle steering, the option is to reset the active members which execute the actual mechanical rotation of the respec- tive wheel axle, whereby the wheel axles of the vehicle will behave in a conventional manner, that is, without active steering.
BRIEF DESCRIPTION OF THE DRAWING The accompanying figure schematically illustrates a diagram of a system which, according to the invention, executes steering of wheel axles in a train set.
DESCRIPTION OF THE PREFERRED EMBODIMENTS A number of embodiments of the invention will be described with reference to the figure.
When driving through a track curve, the lateral acceleration in the leading vehicle of the train is measured, usually at its front bogie by means of at least one accelerometer 1.
The signal is processed in a first signal processing unit 2, whereafter, from the measured acceleration value, the angle through which the wheel axle of a vehicle is to be rotated when the vehicle passes through the curve is calculated in a first reference-value calculator 3. The calculated angular value is multiplied in the same unit by a compensation fac- tor which possibly may vary with the speed of the train through the curve, whereby a first reference-value signal is
obtained. The train speed v is given by the speed transducer 12, the signal of which is passed to the first reference- value calculator 3. The reference-value signal is forwarded to the computers of the subsequent vehicles together with information about a suitable delay for the wheel axles of the respective vehicle before rotation of the wheel axles of the respective vehicle is to be executed. The delay for the respective wheel axle is calculated in a calculator 4. The signal from the calculator 4 is passed to a regulator 5 which is provided in the respective vehicle and which, by means of a control signal, controls devices 6, which may be in the form of hydraulic or mechanical means, which execute the rotation of the wheel axle 7 in accordance with the control signal.
Because of the increased height of the outer rail in rela- tion to the inner rail when entering a track curve, a rail superelevation may be indicated by measuring the difference between the tilt angles of the bogies in one and the same vehicle. According to the figure, measured angles from angle-measuring devices 8,9 for the tilting of the respective bogie and the speed of the train are passed to a second calculator 10 which generates a signal with a super- elevation contribution. This signal with the superelevation contribution may be used for accelerating the formation of a reference value for the steering of the wheel axles 7 and constitutes an additional option shown as dashed connections to the angle-measuring devices 8,9. By adding this signal, the superelevation contribution, to a summator 11, the reference value calculation may be accelerated. As an alternative, a gyro may be used for the same purpose, which gyro measures the angular velocity in the rail supereleva- tion ramp.
The embodiment of the signal formation which has been described so far is part of the prior art. When using reference-value calculation according to this method, a
first reference-value signal is obtained with a delayT which is different from zero, which is marked in the figure.
The devices for forming the first reference-value signal are not necessary for application of the invention, but may be utilized for steering of wheel axles on occasions when memorized track data do not exist.
According to the invention, the steering system of the wheel axles is supplemented by a second reference-value calculator 21. The second reference-value calculator 21 may be integra- ted with the train computer C, which comprises a memory M. A position sensor 13 registers the position n of the train at predetermined points along the route over which the train is running. The predetermined points constitute starting points for mutually unique track sections of the route. When the train is running along a given route, detection of a new starting-point for a new track section initiates storage into the memory M of a reference-value profile for the new track section in a database, in which are stored reference- value profiles for all track sections along the route. The reference-value profile consists of sampled values of a signal which is dependent on the curvature p of curves occurring within a track section, and of a signal which is dependent on the rail superelevation angle (p of these curves.
The curvature of a curve is measured with a first gyro 14 (rate gyro yaw). The angular velocity (dT/dt) is measured around a vertical axis. After signal processing in a second signal processing unit 16, information about the angular velocity (d/dt) for the movement around the vertical axis is passed to a calculating unit 18 in the computer C. In a corresponding way, the rail superelevation angle ç is measured with a second gyro 15 (rate gyro roll) which detects rotation by measurement of the angular velocity (d@/dt) around a longitudinal axis (the longitudinal axis for the bogie where the gyro is located). Also this angular
velocity for the movement around the longitudinal axis is passed to the calculating unit 18, to which calculating unit 18 also the signals indicating the train speed v and the detected train position n are fed. With the aid of the current train speed v, the starting-point n of a train section, a clock pulse signal in the computer C and the angular velocities d/dt and d@/dt, there are calculated in the calculating unit 18 sampled values in real time for curvature and rail superelevation angle according to functions (1) and (2) above for a track section through which the train is currently running. Each such sampled value is stored in a measurement memory 19, which will contain the latest version of curve-geometry data, that is, reference-value profiles, for all the track sections along the current route, when the train has covered the entire route. In connection therewith, compensation is made for the approximately known time delay. When the reference-value profiles of a whole route, here referred to as the route contour, have been stored into the measurement memory 19, these data may be dumped to a database 20 in the memory M, which stores at least the latest dumped route contour and preferably a series of the latest stored route contours.
The reference-value profile of each track section consists of a sequence of discrete measured values. For calculation in the second reference-value calculator 21 of a lateral acceleration, based on the course of the curvature of the curve and the course of the rail superelevation from reference-value profiles in the database 20 and by means of the train speed v, which is fed to the second reference- value calculator 21, formula (3) above is utilized.
In the second reference-value calculator 21 there may also be read, from the memory M (database 20), reference-value profiles from the immediately preceding (consecutive) route contours with curve-geometry data for the track section currently operated by the train. In this connection, either
data from the latest route contour or the mean value of data from the latest consecutive route contours from the database 20 are used to form a reference value without delay (l=0), which reference value is sent to an OR circuit 22 placed in the train computer C before the calculator 4 for calculating the delay of the steering of the wheel axles in the various vehicles of the train, which makes it possible to select, in the system for steering of wheel axles, determination of the wheel steering either with a reference value without delay (l=0) or with delay (lu0), since also the instantaneous, that is, the first, reference-value signal measured in conventional manner may be passed via the OR circuit 22 to the regulator 5 of the steering system.
The first reference-value signal may be selected by the OR circuit 22, for example if no track-geometry data for the current route are stored in the train database, or if the train personnel for some other reason have chosen to use the first reference-value formation. As a further alternative, it may be chosen not to utilize the wheel axle steering at all, that is, the train is run in a conventional manner. The first reference-value calculator may be excluded entirely, as may the associated devices 1,2,3,10,11.
As mentioned previously, the position sensor 13 receives information about the train position either via position transducers which are disposed along the route and which are read by equipment on board the train, or via at least one receiver installed in the train for, for example, satellite navigation according to the so-called GPS system.
The starting-point of a curve may also be stored with a known position according to the GPS system into the train computer, whereby the train computer, via the GPS receiver, continuously seeks the starting position of the next track section. When the expected position is attained, the train computer initiates storage and reading of the reference-
value profile of the attained (identified) track section. In this connection may be mentioned that the reliability (accuracy) of such a positioning system increases with the use of increasingly more satellites and to a still higher extent when the navigation signals are supplemented by transmission from ground-based FM radio stations.
The hardware for calculating reference-value profiles con- sists of conventional electronic units.
The members 6 executing the steering of the wheel axles comprise conventional technique. If hydraulic devices are utilized, the regulator 5 controls hydraulic working cylin- ders, which are adapted, when a steering signal occurs, to rotate the wheel axle to an angle indicated by the steering signal. When no signal occurs or when there is a fault in the hydraulic system, the wheel axle resumes a neutral position, whereby the wheels behave non-controlled in a conventional manner. The system may also be designed such that the active steering mechanism is disconnected by the control system when running through railway stations or tracks where abrupt S-curves occur. Information about such a track section to the train computer may be obtained from the balises or transponders along the route.
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