Improved status monitoring device for monitoring the status of an actuator

Abstract

Improved status monitoring device for monitoring the status of an actuator The status monitoring device comprises a vital controller (40) and a switch assembly (10). The switch assembly has: positive and negative terminals (12, 14) connected to the vital controller; a Double Pole Double Throw - DPDT (21), comprising first and second breakers (16, 18), jointly moved between a first state and a second state, the DPDT having two input contacts connected to the positive and negative terminals respectively, and four output contacts; a circuit (22), connected to the output contacts of the DPDT and defining a first circuit between the positive and negative terminals when the DPDT is in the first state and a second circuit when the DPDT is in the second state, the first and the second circuit altering differently a code signal applied by the vital controller between the positive and negative terminals, so that it is able to detect the state of the switch assembly.

Description

[0001] Improved status monitoring device for monitoring the status of an actuator

[0002] The present invention relates to the technical field of monitoring the status of field elements (also sometimes called wayside objects) such as point machines, derailing devices, safety relays, or the like.

[0003] In the railway sector, the safety integrity of signaling systems are based on the safe status of the field element.

[0004] Monitoring of field elements is widely used to detect the state of field elements, such as the position of a point machine for actuating a switch (or turnout).

[0005] In the following, the example of a point machine is more particularly used for illustrating the invention, but it can be applied to other field elements.

[0006] A point machine is a type of field elements, controlled to change the train route at a turnout. It is important to monitor whether the point machine has positioned the turnout in the correct position, such as left or right. The detection of the current status of the turnout needs to be performed with a certain level of safety to be sure about the integrity of a train route in a railway system. The current status (or state) of the turnout, the current status of the point machine operating that turnout, and the current state of an actuator provided in the point machine to operate the turnout are identical (and are used indifferently in the following), since the status of the point machine corresponds to the position of a mobile part of an actuator of the point machine that is mechanically connected to the turnout to operate this latter.

[0007] For the sake of clarity of the presentation, a turnout including only one point machines is here considered. However a turnout generally includes several point machines and its state is then the result of the aggregation of the states of each all point machines.

[0008] As illustrated by Fig. 1 , monitoring of a point machine according to the state of the art comprises a first switch S1 and a second switch S2, each connected to a respective pair of physical inputs of a vital controller.

[0009] The first and second switches S1 and S2 are mechanically coupled (dash line in Fig. 1 ) to the turnout whose position is monitored, for example to a mobile component of the point machine effecting the change of the state of the turnout.

[0010] The first and second switches S1 and S2 are mechanically coupled so that, when the turnout is in its first position, let say right, the first switch S1 is open and the second switch S2 is closed, and when the turnout is in its second position, let say left, the first switch S1 is closed and the second switch S2 is open. Such a switch assembly 110 is also called antivalent Double Pole Single Throw (“antivalent DPST”). Other variants are well-known, such as “equivalent DPST” and Double Pole Double Throw - DPDT, but not limited to these examples. By applying a suitable constant voltage V1 between the pair of physical inputs to which the first switch S1 is connected, the vital controller 140 is able to determine the individual state, open or closed, of the first switch S1 . By applying a suitable constant voltage V2 between the pair of physical inputs to which the second switch S2 is connected, the vital controller 140 is able to determine the individual state, open or closed, of the second switch S2.

[0011] By logically combining the individual states of the first and second switches, S1 and S2, the vital controller 140 is able to determine the states S of the pair of switches and thus the position of the turnout.

[0012] As shown in Fig. 1 , when the vital controller detects that the first switch is open and the second switch is closed, state “A” is validly detected (and the field element can be said to be in its first position); when the vital controller detects that the first switch is closed and the second switch is open, state “B” is validly detected (and the field element can be said to be in its second position); when the vital controller detects that the first switch is open and the second switch is also open, state “C” is validly detected (state “C” is equivalent to open circuits on both the pairs of physical inputs); and when the first switch is closed and the second switch is closed, state “D“ is validly detected (state “D” is equivalent to closed circuits on both pairs of physical inputs of the vital controller).

[0013] State “C” and “D” violate the definition of an antivalent DPST, but can be used to reveal a failure or an irregularity. State “C” and State “D” may be seen as equivalent states.

[0014] Incidentally, all other situations lead to an invalid detection of the state of the switch assembly 110. For example, a disturbed measure on one or both pairs of physical inputs is classified as an invalid detection. These situations may be the outcome of crosstalk between wires, hardware failure or other internal / external interferences, that could be detected by hardware and / or software.

[0015] The state S as determined by the vital controller 140 is then transmitted, on a logical output of the vital controller, for example to the interlocking system of the signaling system.

[0016] Thus, according to this conventional architecture, two independent physical channels are used. A voltage signal is sent into each switch of the switch assembly and the corresponding position of the turnout is confirmed using a 2oo2 process (“two out of two” process).

[0017] This conventional architecture uses four wires between the vital controller and the switch assembly.

[0018] Since the vital controller is located at a distance from the switch assembly (which is near the turnout, preferably inside the corresponding point machine), the probability of crosstalk is important, leading to an improper detection of the status of the turnout.

[0019] In addition, there are risks that the wires are improperly connected to the vital controller by a technician. The invention therefore aims at providing a simpler status monitoring device to overcome these problems.

[0020] To this end, the object of the invention is a status monitoring device and a method according to the appended claims.

[0021] The invention and its advantages will be better understood upon reading the following, provided solely by way of example, with reference to the accompanying drawings, in which:

[0022] - Figure 1 is a schematic representation of a status monitoring device according to the state of the art, in the four states this status monitoring device can validly detect;

[0023] - Figure 2 is a schematic representation of a status monitoring device according to the invention;

[0024] - Figure 3 is a graph of a code signal applied by the vital controller of the status monitoring device of Fig. 2;

[0025] - Figure 4 is a schematic representation of the status monitoring device of Fig 2., in the four states this status monitoring device can validly detect; and,

[0026] - Figure 5 is a schematic representation of the vital controller of the status monitoring device of Figure 2.

[0027] A preferred embodiment of the status monitoring device according to the invention will now be described by reference to Figure 2.

[0028] The status monitoring device 1 is dedicated to the detection of the status of a field element, for example the position of a turnout 2 operated by a point machine provided with an actuator 20.

[0029] The status monitoring device 1 comprises a switch assembly 10 and a vital controller 40.

[0030] This switch assembly 10 is normally part of and located inside the point machine itself.

[0031] The switch assembly 10 is a Double Pole Double Throw - DPDT 21 assembly coupled to a diode circuit 22.

[0032] The switch assembly 10 comprises:

[0033] - a positive terminal 12 and a negative terminal 14;

[0034] - the DPDT 21 , comprising a first breaker 16, an input contact 13 (which is electrically connected to the positive terminal 12), a second breaker 18, an input contact 15 (which is electrically connected to the negative terminal 14), and four output contacts, respectively a first positive contact 24, a second positive contact 25, a first negative contact 26, and a second negative contact 28; and,

[0035] - the diode circuit 22, comprising a common node C, and:

[0036] - a first electrical mesh 34, that connects the first positive contact 24 to node C; - a second electrical mesh 36, that comprises a diode 32, arranged so that the anode A of the diode 32 is connected to the second positive contact 25 and the first negative contact 26, and its cathode is connected to node C; and,

[0037] - a third electrical mesh 38, that connects the second negative contact 28 to node C.

[0038] Preferably, a resistor is combined in series with the diode 32 to increase the reliability of the solution, by making it less sensible to high induced voltages or other voltage transients / surges that are not generated by the vital controller 40.

[0039] The first breaker 16 and the second breaker 18 are mechanically connected to a mobile part of the actuator 20 to be jointly moved between a first state (corresponding a first position of the turnout) and a second state (corresponding to a second position of the turnout):

[0040] - in the first state, the first breaker 16 is electrically connected to the first positive contact 24 and the second breaker 18 is electrically connected to the first negative contact 26, so as to form a first unidirectional loop L1 from terminal 14 to terminal 12; and

[0041] - in the second state, the first breaker 16 is electrically connected to the second positive contact 25 and the second breaker 18 is electrically connected to the second negative contact 28, so as to form a second unidirectional loop L2 from terminal 12 to terminal 14.

[0042] The switches 16 and 18 are said to be congruently operated.

[0043] The vital controller 40 is provided with a single pair of physical terminals, a positive terminal 42, intended to be connected to the positive terminal 12 of the switch assembly 10, and a negative terminal 44, intended to be connected to the negative terminal 14 of the switch assembly 10.

[0044] The vital controller 40 is able to apply a voltage code signal between its physical terminals 42 and 44 to which the switch assembly is connected. This latter, acting like a load, defines the current which is to be seen as the response signal from the switch assembly 10. The vital controller 40 senses this response signal.

[0045] The controller 40 is able to analyze the response signal in order to determine the state of the switch assembly 10 and consequently the position of the turnout 2.

[0046] One possible code signal generated by the vital controller 40 is shown in Fig. 3. This figure represents a graph that gives the time evolution of a voltage pulse, this pulse being periodically repeated to form the code signal.

[0047] One pulse is, for example, a square-wave voltage comprising successively an initial positive square-wave P1 , a middle negative square-wave P2 and a final positive squarewave P3.

[0048] Other shapes of the code signal can be encompassed, providing that it comprises at least one positive part and one negative part. The response signal received back from the switch assembly 10 allows the vital controller 40 to determine the current state of the switch assembly 10 among a set of four possible states.

[0049] These four possible states are illustrated in Fig. 4.

[0050] When the vital controller 40 detects that current is flowing between terminals 42 and 44 and the voltage only comprises the middle negative square-wave P2 of the pulses of the code signal, it means that the diode 32 (considering an ideal behavior) has blocked the positive part of the pulses of the code signal. This is only possible when the first circuit L1 is established between the terminals 12 and 14. State “A” is then validly detected (and the actuator 20 can be said to be in its first position).

[0051] When the vital controller 40 detects that current is flowing between terminals 42 and 44 and the voltage only comprises the initial and final positive square-waves P1 and P3 of the pulses of the code signal, it means that the diode 32 has blocked the negative part of the pulses. This is only possible when the second circuit L2 is established between the terminals 12 and 14. State “B” is then validly detected (and the actuator 20 can be said to be in its second position).

[0052] When the vital controller 40 detects that there is no current floating between terminals 42 and 44 and the voltage, its means that there is an open circuit between the negative and positive terminals 12 and 14 of the switch assembly 10. State “C” is validly detected.

[0053] When the vital controller 40 detects that current is flowing between terminals 42 and 44 and that the voltage of the response signal follows both positive and negative pulses of the code signal (i.e. that current is floating bidirectionally between the terminals), its means that there is a short circuit between the negative and positive terminals 12 and 14 of the switch assembly, state “D“ is validly detected.

[0054] State “C” and “D” may be seen as equivalent and corresponding to a general faulty state of the status monitoring device 1 .

[0055] It is to be noted that states “C” and “D” can also be used to indicate an intermediate state of the field element, such as that the turnout is actually switching (i.e. moving) or is in the middle position (i.e. not in any of the end positions).

[0056] In addition, time multiplexing of same codes between different vital controllers can be used to detect crosstalk. When the vital controller 40 detects current and voltage pulses while it does not apply any code signal on its terminals, a crosstalk between the pair of wires connecting the vital controller 40 to the switch assembly 10 with another pair of wires connecting another vital controller to another switch assembly can be identified and the corresponding state reported.

[0057] Similarly, crosstalk may be identified by each vital controller using a unique code. Furthermore, if the code has deteriorated it can also reveal other issues in the status monitoring device.

[0058] The analysis of the received signal by the controller 40 leads to the output of a logical signal S, indicative of the state validly detected.

[0059] The possible set of values of logical signal S is application dependent.

[0060] For example, the possible set of values of logical signal S is : state “A”, state “B”, state “C”, and state ”D”; or state “A”, state “B”, state “faulty”, and state “undefined”. Alternatively, a state “crosstalk” is added to the set.

[0061] Preferably, the values of logical signal S are identical to those outputted by the status monitoring device according to the state of the art to allow the interlocking system to deal with them without further modifications.

[0062] Fig. 5 is a functional representation of a preferred embodiment of the vital controller 40.

[0063] Vital controller 40 comprises: a code signal generating module 50, four diode like modules 53, 54, 55 and 56, first and second checking modules 57 and 58, and a voting unit 49.

[0064] The code signal generating module 50, comprises: a signal generator 51 , able to generate a succession of pulses, each pulse being generated according to a predefined code and the pulses being properly time spaced; and a galvanic insulation module 52, comprising for example a transformer, to separate the generator 51 from the switch assembly 10.

[0065] The terminals of the primary of the transformer being connected to the generator 51 and the terminals of the secondary of the transformer being connected to the terminals 42 and 44 through the diode like modules.

[0066] The code signal generating module 50 informs directly the first and second checking modules, 57 and 58, of the code signal currently applied.

[0067] The four diode like modules, respectively 53, 54, 55 and 56, are adapted to sense the current and voltage between the terminals 42 end 44 of the vital controller to which the switch assembly 10 is connected, and transmit the corresponding sensing signal to the first and second checking modules 57 and 58.

[0068] Each diode like module is for example an optocoupler.

[0069] The first and second checking modules 57 and 58 check, independently one from the other, the coherence between the code signal output by module 50 and the sensing signals received from the diode like modules (the pair of diode like modules 53 and 54 for the first module 57 and the pair of diode like modules module 55 and 56 for the second module 58 respectively).

[0070] Each checking module is able to determine a value of the state of switch assembly 10. The voting module 59 is able to compare the first and second values of the state of the switch assembly respectively output by the first and second checking modules 57 and 58, to determine the current state S of the switch assembly 10 in safety.

[0071] For example, when switch assembly 10 is in state C, no current is circulating between terminals 42 and 44 when the code signal is generated by module 50. Since no current is flowing through the diode like modules, they do not transmit any sensing signal to the checking modules 57 and 58. Consequently, they both determine that switch assembly 10 is in state C.

[0072] When switch assembly 10 is in state A, current is circulating between terminals 42 and 44 only when a negative pulse is applied. In this case, the diode like module 55 senses the current and transmit a sensing signal to checking module 58, diode like module 56 is blocked, diode like module 54 senses the current and transmits a sensing signal to checking module 57 and diode like module 53 is blocked. From this pattern of sensing signal versus code signal, the checking modules 57 and 58 both determine that the switch assembly 10 is in state A.

[0073] When switch assembly 10 is in state B, current is circulating between terminals 42 and 44 only when a positive pulse is applied. In this case, the diode like module 53 senses the current and transmits a sensing signal to checking module 57 and the diode like module 54 is blocked. The diode like module 56 senses the current and transmits a sensing signal to checking module 58 and the diode like module 55 is blocked. From this pattern of sensing signal versus code signal, the checking modules 57 and 58 both determine that the switch assembly 10 is in state B.

[0074] When switch assembly 10 is in state D, current is circulating between terminals 42 and 44 only when a positive pulse is applied but also when a negative pulse is applied. In this case, each diode like modules senses the current and transmits a sensing signal to the associated checking module. From this pattern of sensing signal versus code signal, the checking modules 57 and 58 both determine that the switch assembly 10 is in state D.

[0075] When the switch assembly 10 is subject to crosstalk, no code signal is generated by module 50, but one or both pairs of diode like modules are sensing the current circulating along the pair of wires connected the switch assembly 10 with the controller 40. However, the checking modules 57 and 58 being unable to correlate the received sensing signal with a code signal, they both determine that the switch assembly 10 is in the state “crosstalk”.

[0076] The person skilled in the art will appreciate that the vital controller 40, by mean of his 2oo2 voting mechanism, is able to determine the status of the field element in safety, for example according with the Level 4 of the Safety integrity level - SIL standard.

[0077] Alternatively, several switch assemblies are electrically connected to as many pairs of physical inputs of one or several vital controller(s) 40. A common code signal may be used for the detection of the state of each switch assembly, however it is preferable to use a specific code signal for each switch assembly.

[0078] When the same code is shared between several switch assemblies, the vital controller can filter crosstalk disturbances with time multiplexing.

[0079] When the code is unique for each switch assembly, the vital controller can filter crosstalk disturbances on the code itself.

[0080] The ability to detect crosstalk increases the safety level with which the status of the field element is detected.

[0081] In the preferred embodiment described above, the function of the diode 32 is to filter the code signal differently when the positive and negative terminals are connected through the first circuit L1 or the second circuit L2. The person skilled in the art could alter circuit 22 to provide it with other type of component(s) able to realize such a filtering. For example, a first diode could be placed on mesh 34 and a second diode could be placed on mesh 38, these first and second diode being properly oriented to achieve the required filtering of the code signal so that the response signal is indicative of the position of the Double Pole Double Throw - DPDT 21 .

[0082] However, the preferred embodiment where one diode is positioned on the mesh of the circuit that is shared between the first circuit and the second circuit presents the benefit that, in case of a mal-function of the diode, the first and second circuit are similarly affected. In this particular arrangement, a closed circuit is established between the positive and negative terminals, with no filtering of the code signal.

[0083] The invention presents the following advantages:

[0084] The status monitoring device according to the invention requires only two wires to establish the link between the switch assembly and the vital controller. This is contrary to the state of the art, where two pairs of wires are required to connect the switch assembly to the vital controller.

[0085] The vital controller needs to have only one pair of physical inputs per controlled field element.

[0086] Lower cost interlocking object controller for applications up to Safety Integrity Level 4 is obtained.

[0087] Compare to the prior art solution, this means less material (copper for the wires) used and a reduced energy consumption, since the vital controller has to apply an electrical signal between only one pair of physical terminals.

[0088] The invention renders the deployment in site very easy, the technician having only a pair of wires to connect at each end.

[0089] Reducing the number of wires also reduces the risk of crosstalk. Examples of field element that can be monitored with the invention are physical switches, push buttons, front / back-contacts in safety relay and point position contacts inside a point machine, etc.

[0090] Classical railway applications are related to the detection of the position of switch, to collect the status of adjacent relay interlocking systems or monitoring of push buttons in a local control panel used to switch points, set train routes in depot areas, activation of derailing devices, etc.

[0091] Outside the rail sector, there are unlimited applications for the monitoring relay according to the invention.

Claims

CLAIMS1 . A status monitoring device (1) for monitoring the status of an actuator (20) of a field element of a railway network, comprising a vital controller (40) and a switch assembly (10), characterized in that the switch assembly (10) comprises:- a positive terminal (12) and a negative terminal (14), connected to a pair of physical inputs of the vital controller;- a Double Pole Double Throw - DPDT (21 ), the DPDT comprising a first breaker (16) and the second breaker (18) operably connected to the actuator (20) to be jointly moved between a first state and a second state, the DPDT having two input contacts and four output contacts, the two input contacts being electrically connected to the positive terminal (12) and the negative terminal (14) respectively;- a circuit (22), connected to the output contacts of the DPDT (21 ), the circuit defining a first circuit between the positive and negative terminals when the DPDT is in the first state and a second circuit between the positive and negative terminals when the DPDT is in the second state, the first and the second circuit altering differently a code signal applied by the vital controller between the positive and negative terminals, so that the vital controller is able to detect, from the response signal received back from the switch assembly, a state of the switch assembly and, consequently, the status of the actuator.

2. The status monitoring device (1 ) according to claim 1 , wherein the vital controller (40) generates a code signal comprising a succession of pulses, each pulse comprising at least one positive voltage part and one negative voltage part, the first circuit (L1) being able to filter out the positive part of each pulse so that the response signal corresponds to the negative part of each pulse, and the second circuit (L2) being able to filter out the negative part of each pulse so that the response signal corresponds to the positive part of each pulse.

3. The status monitoring device (1 ) according to claim 1 or claim 2, wherein, the four output contacts of the DPDT (22) being a first positive contact (24) and a second positive contact (25) associated with the first breaker (16) and a first negative contact (26) and a second negative contact (28) associated with the second breaker (18), the circuit (22) comprises:- a first electrical mesh (34) connecting the first positive contact (24) to a common node (C);- a second electrical mesh (36), connecting the second positive contact (25) and the first negative contact (26) to the common node (C) ; and,- a third electrical mesh (38) connecting the second negative contact (28) to the common node (C).

4. The status monitoring device (1 ) according to claim 3, wherein the second electrical mesh (36) is provided with a diode (32).

5. The status monitoring device (1 ) according to any one of claims 1 to 4, wherein the vital controller is provided with means for detecting the state of the switch assembly (10) in safety, preferably according to SIL 4.

6. The status monitoring device (1 ) according to any one of claims 1 to 5, wherein, when the response signal corresponds to a short circuit between the positive and negative terminals of the switch assembly, the vital controller is able to detect a faulty state or an intermediate state.

7. The status monitoring device (1 ) according to any one of claims 1 to 6, wherein, when the response signal corresponds to an open circuit between the positive and negative terminals of the switch assembly, the vital computer is able to detect a faulty state or an intermediate state.

8. The status monitoring device (1 ) according to any one of claims 1 to 7, wherein the switch assembly and the vital controller are connected by only one pair of wires.

9. The status monitoring device (1 ) according to any one of claims 1 to 8, wherein the code signal presents a succession of pulses comprising at least one positive voltage pulse and at least one negative pulse so as to form a code.

10. The status monitoring device (1 ) according to claim 9, wherein, the switch assembly being a first switch assembly, the status monitoring device comprises a second switch assembly, the first and second switch assemblies being similar and connected to the vital controller, the code embedded in the pulses of the code signal applied to each switch assembly being specific to said switch assembly.11 . The status monitoring device (1 ) according to any one of claims 1 to 10, wherein the vital controller comprises :- a code signal generating module (50), adapted to output the code signal;- a first pair of diode like modules (53, 54), located between the code signal generating module (50) and the pair of physical inputs of the vital controller, and adapted to sense whether a current is flowing between the inputs of the pair of physical inputs of the vital controller and a sign of the voltage of the current, and to generate first sensing signal accordingly;- a first checking module, for determining the status of the actuator based on the code signal and the first sensing signal received from the first pair of diode like modules.

12. The status monitoring device (1 ) according to claim 1 1 , wherein, the first checking module determining a first value of the status of the actuator, the vital controller further comprises :- a second pair of diode like modules (53, 54), located between the code signal generating module (50) and the pair of physical inputs of the vital controller, and adapted to sense whether a current is flowing between the inputs of the pair of physical inputs of the vital controller and a sign of the voltage of the current, and generating second sensing signal accordingly;- a second checking module, for determining a second value of the status of the actuator based on the code signal applied by the code signal generating module and the second sensing signal received from the second pair of diode like modules; and,- a voting module (59) able to compare the first and second values to determine the status of the actuator in safety.

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