Tilt control

Abstract

 An arrangement for adjusting a tilt of a wagon having a tilting body (2), the arrangement comprising a digital hydraulic valve assembly, which may be arranged to control the movement of at least one tilting actuator (5) of the wagon having a tilting body, and a control unit (7b) comprising at least a regulator (8) for controlling the valve states in question, and means for receiving input and feedback data (9) for determining a tilting need and means for producing control signals (10) for valve control power stages in accordance with commands issued by the regulator.

Description

Background of the invention

[0001] The invention relates to a tilt control of wagons having tilting bodies and, in particular, to an arrangement and method for adjusting the tilt of such a wagon.

[0002] Trains are often provided with wagons having tilting bodies to allow higher driving speeds on winding track portions in particular. The tilt angle of the body is adjusted in an attempt to compensate for the effects of a centrifugal effect the passengers are subjected to in curves by tilting the body to the side of the inside curve along the longitudinal axis of the wagon. It is thus possible to drive on curves at higher speeds, without the travel comfort being impaired and without a need to make changes to the track structures.

[0003] The wagon may be tilted hydraulically by placing a typically single-acting hydraulic cylinder in each corner of the wagon. In prior art solutions, tilting is adjusted by adjusting the movement of these cylinders with servo valves. Servo valves allow an extremely good adjustment precision to be achieved, but a problem with these solutions is that servo valves are too expensive components to obtain and service. Moreover, servo valves are extremely fault-prone and, in addition, on a train it is not always possible to guarantee that a level of oil cleanliness can be maintained that would be sufficient for servo valves that easily become dirty. When the tilt arrangement is out of order, the driving speed of the train has to be reduced accordingly, which causes problems in keeping the schedule, for example. This is why, in practice, servo valves are typically doubled, and thus an additional servo valve may be taken in use if the primary servo valve fails. However, doubling is an expensive solution and does not remove the problems of costs and failures associated with servo valves.

Brief description of the invention

[0004] It is thus an object of the invention to provide a method and an apparatus implementing the method so as to enable the above-mentioned problems to be solved. The object of the invention is achieved by a method and an arrangement characterized by what is stated in the independent claims. Preferred embodiments of the invention are disclosed in the dependent claims.

[0005] The idea of the invention is to replace conventional tilt adjustment based on complex hydraulic components, such as proportional or servo valves, by simple hydraulic components and intelligent control.

[0006] An advantage of the method and arrangement of the invention is that the adjustment of the tilting of the body may be implemented by a simple, inexpensive, precise and highly fault-tolerant solution.

Brief description of the figures

[0007] The invention is now described in closer detail in connection with preferred embodiments and with reference to the accompanying drawings, in which

Figure 1 is a schematic view of a tilting of a body 2 of a wagon 1;

Figure 2 is a schematic view of components associated with the tilting of a wagon with a tilting body and the control thereof;

Figure 3 is a schematic view of a tilt adjustment arrangement employing digital hydraulics for adjusting the tilting of a wagon having a tilting body;

Figure 4 is a schematic view of an example of a virtual valve stem; and

Figure 5 is a schematic view of a method for adjusting the tilting of a wagon having a tilting body.

Detailed description of the invention

[0008] Figure 1 is a schematic rear view of a tilting of a body 2 of a wagon 1. The body 2 of the wagon is arranged to tilt in relation to a bogie 3. In curves, for example, the track 4 may be inclined in relation to the ground plane and in wagons having tilting bodies, the body 2 may also be tilted in relation to the track. A total tilt angle A comprises both a body tilt B and a track inclination C. The body may be tilted in relation to the track by tilting actuators 5, such as hydraulic cylinders. A typical tilt speed of a passenger car may be 8 degrees per second, for example, and the distances from a tilt adjustment arrangement to the tilting actuators are typically relatively long, for example 11 meters.

[0009] Figure 2 is a schematic view of components associated with the tilting of a wagon having a tilting body and with the control thereof. A wagon having a tilting body typically comprises tilting actuators 5, typically four hydraulic cylinders, which are usually arranged to the corners of the wagon 1 or in the vicinity thereof. The tilt adjustment arrangement typically comprises means 6 for producing a pressure and a volume flow, such as a motor pump unit, and means 7 for controlling the tilting actuators, for example at least one servo valve unit. In addition, a system of this type typically comprises a plural number of other components, e.g., a tank, pressure accumulators and valves. In these solutions servo valves, which are expensive with regard to their purchase price and servicing costs in particular, cause various problems and error in the tilt control and even in the direction of the tilt. It is possible that the control tends to tilt the wagon to some direction even when there is no real need for control and no control signal issued.

[0010] Figure 3 is a schematic view of a tilt adjustment arrangement employing digital hydraulics for adjusting the tilting of a wagon having a tilting body, means for controlling the tilting actuators being shown in particular. In that case the tilt adjustment arrangement comprises at least a digital hydraulic valve assembly 7a and a control unit 7b. The digital hydraulic valve assembly in question comprises a number of valves and is adjustable to control the movement of at least one tilting actuator 5 of the wagon 1 having a tilting body. The tilt adjustment arrangement may naturally also comprise a plurality of other components, such as means for producing a pressure and a volume flow, a tank, pressure accumulators and other components necessary for the operation.

[0011] Digital hydraulics applied to tilt control allows simple hydraulic components, which are advantageous in many ways, to be used when the versatile features of the arrangement are implemented by an intelligent regulator of the control unit. Examples of basic components of the digital hydraulic valve assembly 7a that may be used in this type of arrangement are, for example, simple on/off valves, whose flows may be freely determined by throttles and whose opening and closing may be controlled by a regulator. By changing the control codes of the regulator, the same hydraulic components allow different, and also more complex, valve assemblies acting like valves to be implemented. The valves to be used may be selected to have a sufficiently fast response time, sufficient throughput and to be substantially leakage-free.

[0012] The control edges of the digital hydraulic valve assembly 7a may be implemented independently from one another, which enables energy efficiency and good performance to be provided. By optimizing the control edges it is also possible to optimize the number of the valves to be used to enable sufficient throughput and precision of adjustment. The optimizing allows a good precision of adjustment and operational reliability to be achieved with the digital hydraulic valve assembly 7a in question and, at the same time, a reasonable price to be maintained. For further improvement of operational reliability, some of the largest valves may be doubled, which enhances performance in fault situations. On the one hand, reliability may also be improved, and precision of adjustment at the same time, by adding more valves, but, on the other hand, this increases the size of the arrangement and purchase price of the valves and the control unit.

[0013] The control unit 7b comprises at least a regulator 8, which comprises control codes for controlling the states of the valves in the digital hydraulic valve assembly 7a and means for receiving 9 input and feedback data for determining a tilting need and for generating 10 control signals for the power stages of the valve controls in accordance with the commands issued by the regulator. These operations may be implemented by micro controllers, for example. In addition, the control unit 7b may comprise other parts and components, such as means for monitoring the operation of the tilt adjustment arrangement, or its parts may be arranged to implement such tasks.

[0014] In digital hydraulics, for example hydromechanic operations conventionally carried put using proportional and servo valves may be arranged to be implemented by control codes in the regulator by employing different algorithms. With the above-disclosed digital hydraulic valve assembly and the regulator in question, it is possible to implement the "virtual valve stem" 11 of Figure 4, the like of which would not be feasible by conventional technology and, moreover, which enables extremely rapid state changes.

[0015] In other words, use of the digital hydraulic valve assembly 7a allows many and various prior art valves, for example, to be replaced by a limited number of extremely simple hydraulic components by changing the control code of the regulator. When necessary, the parameters of the control code may be changed even during operation, which allows the features of the system to be changed whenever necessary. This, in turn, allows an excellent fault tolerance of the system, for example, because in case of a malfunction of a simple component, which generally is reliable already as such, the operation of the component may be compensated for by means of a program or fully automatically even.

[0016] Figure 5 is a schematic view of a method for adjusting the tilting of a wagon having a tilting body. The method comprises at least the following steps. Controlling 51 at least one tilting actuator of the wagon having a tilting body by a digital hydraulic valve assembly comprising a plurality of valves. Receiving 52 necessary input and feedback data for determining a tilting need. Controlling 53 valve states of the digital hydraulic valve assembly by means of control codes of a regulator provided in a control unit. Generating 54 control signals for controlling valve control power stages for the valves in the digital hydraulic valve assembly in accordance with commands issued by the regulator.

[0017] According to an embodiment, the regulator may be implemented by an AD conversion, which allows 128 states to be achieved by controlling 7 valves, for example. An advantage of this adjustment is that it does not require high computational capacity and it is simple to implement in a reliable manner. Since the valves in the digital hydraulic valve assembly may be controlled fully independently from one another and since the reinforcements of the different control edges may be selected to be equal or not equal, the control may be determined to be symmetric or asymmetric. An asymmetric control may be advantageous for example in cylinder uses when the surface areas of the chambers differ from one another or, in the case of single-acting cylinders, when the sizes of the volume flows are unequal between the active and the passive side.

[0018] According to an embodiment, the regulation method used is a PNM method (Pulse Number Modulation). This method allows a sufficiently good precision of adjustment to be achieved in the control of a body tilt. The adjustment code required by the PNM method is extremely simple, the system is not sensitive to changing circumstances, such as oil temperature and viscosity or pressure difference, it has good fault tolerance, and calibration of the system is typically not needed before it is taken in use. In addition, the oil cleanliness class required in a PNM-controlled digital hydraulic tilt adjustment arrangement is lower than in a conventional servo-valve-controlled arrangement, for example. According to another embodiment, the regulation method used is a PCM method (Pulse Code Modulation), which allows an adjustment of a still higher precision to be obtained but, on the other hand, because of the extremely high precision, requires filtering of interferences from the signals and/or temperature compensation and/or calibration for unnecessary tilt movements to be avoided.

[0019] According to an embodiment, the regulator may be arranged to take into account pressure measurement data received from the hydraulic system, in which case the regulator may try to keep the valve throughput by a specific control operation at a specific, substantially constant value irrespective of pressure differences. This kind of program-based pressure compensation allows a travel speed independent of load to be achieved also in an open-loop system.

[0020] According to an embodiment, also other valves adaptable to digital hydraulics may be used instead of or in addition to on/off valves, for example valves that may be controlled by a ballistic control mode (BaM) in addition to an on/off control.

[0021] According to an embodiment, a train unit may comprise a plural number of different tilt adjustment arrangements, for example different wagons may be provided with different tilt adjustment arrangements. In this context a train unit refers to an entity comprising at least one or more wagons coupled to one another and having tilting bodies, the tilt adjustment arrangements comprised by the entity forming a substantially uniform whole. Hence one or more tilt adjustment arrangements may be arranged to process detection data, such as a signal obtained from acceleration sensors or speedometers, to be used in tilt control and to determine on the basis of these detection signals at least one tilt control signal for at least one wagon provided with the tilt adjustment arrangement. Further, the tilt adjustment arrangement may be arranged to determine a corresponding tilt control signal for at least one other wagon or, particularly preferably, for all wagons in one and the same train unit, and to transmit the tilt control signal to the wagon or wagons in question. Likewise, one or more tilt adjustment arrangements may be arranged, for example, to receive a tilt control signal from another tilt adjustment arrangement and to control the movement of the tilting actuators on the basis of this signal and/or to guide the tilt control signal or other signals further to a next tilt adjustment arrangement.

[0022] According to an embodiment, the digital hydraulic valve assembly and the control unit of the tilt adjustment arrangement as well as other necessary components, such as input and output connections, may be arranged into one and the same module so that at least one original tilt adjustment arrangement of the train unit and/or a wagon based on conventional hydraulic control, such as proportional or servo valves, is replaceable by the digital hydraulic tilt adjustment arrangement disclosed here, without other essential changes being made to the wagon or the train unit. In that case, for example the current control signals of the train unit or the wagon may be modified to suit the digital hydraulic tilt adjustment arrangement without having to change the sensor arrangements or measuring devices, for example.

[0023] It will be apparent to a person skilled in the art that as technology advances, the basic idea of the invention may be implemented in many different ways. The invention and its embodiments are thus not restricted to the examples described above but may vary within the scope of the claims.

Claims

1. An arrangement for adjusting a tilt of a wagon having a tilting body, characterized in that the arrangement comprises:

a digital hydraulic valve assembly comprising a plurality of valves and adaptable to control a movement of at least one tilting actuator of a wagon having a tilting body; and

a control unit comprising at least a regulator, which in turn comprises control codes for controlling valve states of the digital hydraulic valve assembly, and means for receiving input and feedback data to determine a tilting need and means for generating control signals for valve control power stages in accordance with commands issued by the regulator.

2. An arrangement as claimed in claim 1, characterized in that at least some of the valves are on/off hydraulic valves the opening and closing of which are controlled by the regulator.

3. An arrangement as claimed in claim 1 or 2, characterized in that at least some of the valves are hydraulic valves controllable by a ballistic control mode.

4. An arrangement as claimed in any one of the preceding claims, characterized in that the regulator is implemented by an AD conversion.

5. An arrangement as claimed in any one of the preceding claims, characterized in that the regulation method used in the valve control is PNM.

6. An arrangement as claimed in any one of claims 1 to 4, characterized in that the regulation method used in the valve control is PCM.

7. A train unit comprising at least one wagon having a tilting body, characterized in that the train unit comprises an arrangement according to any one of claims 1 to 6.

8. A train unit as claimed in claim 7, characterized in that the train unit comprises at least two wagons having tilting bodies;
that each wagon comprises at least one tilt adjustment arrangement as claimed in any one of claims 1 to 6;
that at least one of these tilt adjustment arrangements is configured to handle detection data used in the tilt control and to determine and transmit a tilt control signal on the basis of these detection signals to the tilting actuators of the at least two wagons; and
that at least one of these tilt adjustment arrangements is configured to receive the tilt control signal from another one of these adjustment apparatuses and to control the movement of the tilting actuators on the basis of this signal.

9. A method for adjusting a tilt of a wagon having a tilting body, characterized in that the method comprises at least the following steps of
controlling at least one tilting actuator of a wagon having a tilting body by a digital hydraulic valve assembly comprising a plurality of valves;
collecting necessary input data for determining a tilting need; controlling valve states of the digital hydraulic valve assembly by means of control codes of a regulator provided in a control unit; and
generating control signals for controlling valve control power stages for the valves in the digital hydraulic valve assembly in accordance with commands issued by the regulator.

10. A method as claimed in claim 9, characterized by implementing the regulator by an AD conversion.

11. A method as claimed in claim 9 or 10, characterized by regulating the valve control by PNM.

Drawing