CN1262747A - Method and device for testing double sensor system - Google Patents

Abstract

With a double sensor system used for positioning purposes in safety applications, an operating failure, including an inadmissible increase in the sensitivity of one of the sensors (S1, S2), is made known because reference marks (RM1, RM2) each having a response section (AA1, AA2) and a test section (PA11, PA21) are provided for. If operations are proceeding correctly the sensor emits a first output signal (AS1) in the area of the response section and a second output signal (AS1) in the area of the test section. In contrast, when a maximum sensitivity threshold (P) is exceeded the sensor also produces the first output signal (AS1) in the area of the test section. If there is a known change in the signal of the other sensor this is used to test the change in the output signal of the first sensor.

Description

A method and device for testing a dual sensor system

The invention relates to the technical field of positioning, in particular to the technical field of safe absolute positioning of a transportation system that follows a track. The invention relates to a method and device for testing a dual sensor system.

In trajectory-dependent transport systems, especially passenger transport systems, high safety requirements must be met with respect to precise positioning and the like. For example, the safety of passengers getting on and off within the range of the stop is required, or the precise positioning of the locomotive in the upper and lower gates is required, so as to accurately determine the position of the getting on and off range (door) within the stop range. Prerequisites for this are a safe sensor technology (redundant backup system or functional safety system) and high accuracy requirements.

Sensors suitable for automatic positioning are, for example, inductive transmitters which react to fixed metal sheets. A dual-sensor system is used here, whose dual-channel hardware performs a signal-safe evaluation and processing of the sensor signals, so that the relevant safety standards (eg DIN VDE 0801, DIN 19250, Mü8004) can be met. Generally, sensors have a sensing range called an active sensor lobe, over which the sensor responds to a reference mark. For example, an inductive sensor that responds to metal reports its position with a defined output signal when a metal piece is within its sensing range. The sensing range of the sensor and the minimum sensitivity guaranteed by the manufacturer can usually be obtained from the accompanying data sheet or quality verification data.

In safety technology applications, both the analyzed components - such as computers or relay circuits ("safety connections") - and the sensor functions must be safe and reliable. Therefore, a failure disclosure mechanism is also required for the sensor itself. The complete failure of the sensor can be confirmed, if necessary, by means of dual-channel capability within the allowable reveal time. Here, a single error must not be harmful to the entire system, and the error must be revealed within a certain period of time. The longest permissible exposure time is determined here as a function of the failure rate of the entire sensor system. In a dual sensor system (so-called 2 in 2 system (2 von 2System)), according to the railway standard Mu 8004, this time is MTBF/1000 (MTBF is the abbreviation of English mean time between failure, referring to the average time to failure).

However, a special problem arises when a two-sensor system is used for positioning in safety technology applications, namely that the sensitivity of one of the two sensors increases significantly during operation. Such an increase in sensitivity can be due, for example, to aging effects emanating from, for example, the analysis line, the sensor signal conditioning device or the sensor itself. Within the framework of the present invention, sensor includes, in addition to the actual main sensor element, the connected devices for sensor signal analysis and processing as well as the interface of the two-channel signal transmission line of the two-sensor system. In the conventional application of sensors, it is important to pay attention to ensuring that the sensor has a minimum sensitivity and maintaining this minimum sensitivity, and the increase of the sensitivity is often not critical. Therefore, in a dual sensor system used in the field of safety technology, the increase of the sensitivity of a sensor will cause the sensor not only to recognize those positioning marks that are set to be detected under fault-free operating conditions, but also for example to be in this position. Objects around the marker are incorrectly detected as markers. When an inductive sensor is used, for example metal components along the path may lead to false positioning information.

It is therefore an object of the present invention to provide a method and a device for testing a two-sensor system which can still be positioned in the field of safety technology if one of the sensors has an inadmissible increase in sensitivity.

The object of the invention is achieved by a method for testing a dual sensor system having two sensors and used on a locomotive, the method for testing whether one of the sensors has an impermissible increase in sensitivity . In this method, the two sensors each pass a fixed reference marker with a response segment and at least one test segment in one direction of movement; Its sensor detects whether an output signal change occurs when another sensor passes by its reference mark and that sensor moves from the range of its test segment into the range of the response segment or vice versa. In this case, each fixed reference mark corresponds to each sensor; taking into account the sensitivity field of the sensor, the sensor and the associated reference mark are selected and matched to each other so that the sensor operating within a permissible sensitivity tolerance The sensor gives the first output signal within the response zone and another, the second output signal, within the test zone; however, a sensor whose sensitivity exceeds an allowable sensitivity threshold is Also gives the first output signal.

Claim 6 presents an arrangement for achieving the above object.

A major advantage of the invention is that the failure of a sensor due to its impermissibly increased sensitivity can also be revealed using simple means. For this reason, according to the invention, only the reference marks and the sensors are matched to each other, so that for sensors that work within a predetermined sensitivity tolerance, they only respond in the range of the response section, but not in the test section. (which has a predetermined relative position with respect to the response zone) the sensors do not respond. Since it can be reliably inferred from the output signal of a correctly functioning sensor that the other sensor or its sensing (sensitivity) field has or is expected to transition from the test zone to the response zone when the dual sensor system continues to move, or vice versa From the response phase to the test phase, a reliable and safety-compliant sensor test can thus be carried out automatically and preferably periodically. The frequency of testing is preferably determined based on sensor reliability data and operating conditions.

In terms of signal processing technology, such a test is preferably carried out after the exact departure from the reference mark.

Considering that there may be positional tolerances between the sensors or between the reference marks, and that the sensing fields of the sensors may have different spatial dimensions, according to a preferred design of the present invention, it is tested whether a change in the output signal of the two sensors occurs Within a transition time or within an exact line segment. In addition to monitoring the output signal change over time, a track-section-dependent test is provided in particular in track-dependent transport systems, since track-dependent transport systems usually have, for example, incremental road test devices.

According to an advantageous refinement of the method according to the invention, the number of segment changes of the test-related reference marker is increased, ie a test segment is arranged before the response segment and a test segment is arranged after it.

Basically, a known spacer can be arranged between the test section and the response section. By having the test line section directly adjoining the response section, the output signal change can be analyzed particularly advantageously in terms of signal processing technology.

The method of the present invention is described in further detail below with the help of a accompanying drawing, in the accompanying drawing:

Fig. 1 shows the application of the inventive method aspect railway technology;

Figure 2 shows the sensitivity field of a sensor;

Figure 3 shows the sensor output signal.

As shown in Fig. 1, a passenger locomotive F traveling in the direction of motion B contains a two-channel safety connection connecting the output signals of two inductive sensors S1, S2. In this case, a safety computer R is arranged in the safety-related conventional system, which makes a safety connection (in the simplest case an "and" connection) of the output signal on the sensor side, from which the final A positioning signal OS is generated which determines the position of the locomotive F relative to a section, in particular a railway station BHF. The locating signal OS or locating criterion is used, for example, for the safe opening of the doors, so that passengers get on and off the train at a predetermined boarding and disembarking area on the platform of the railway station. Only when the positioning standard OS appears, the corresponding door facing the railway station platform is opened.

Each sensor S1, S2 has a fixed reference mark RM1, RM2 arranged at the railway station BHF. When using an inductive sensor, the reference mark can be designed as a simple metal plate. However, various other combinations of sensors and associated reference marks are possible, for example devices based on the optical scanning principle. Each reference mark RM1, RM2 comprises a response section (metal sheet) AA1, AA2, the length of which is L. Seen from the direction of movement B, the two sides of the response sections AA1 and AA2 respectively follow the test sections PA11 , PA12 or PA21 , PA22 one after the other.

FIG. 2 schematically shows a sensor corresponding to sensors S1 and S2, which emits a three-dimensional lobe, the so-called active lobe, referred to below as sensitivity field EF. The height H of the sensitivity field EF is preferably greater than its width B here.

Referring again to FIG. 1, it can be seen that, taking into account the sensitivity field EF (FIG. 2) of the respective sensors S1, S2, the dimensioning, positioning and mutual arrangement of the respective sensors S1, S2 and the associated reference marks RM1 or RM2 are such that the sensors S1 , S2 deliver a first output signal AS1 , AS2 within the range of response sections AA1 , AA2 . Accordingly, each sensor S1, S2 has a sensitivity tolerance range TB which is of a size such that a correctly functioning sensor is reliably disconnected above a response threshold spacing S when leaving a detectable reference mark zone, i.e. , send out the second sensor signal AS1, AS2. This signal AS1 , AS2 differs from the first sensor signal AS1 , AS2 in that it is emitted as soon as the correctly functioning sensor and its sensitivity field are no longer in the respective response range AA1 or AA2 . Furthermore, the configuration of the sensor and the reference marker is chosen such that the reference marker and its response section are arranged at a working distance from the sensor, so that the sensitivity field of the sensor touches the response section at the position shown and the sensor thus produces a sensor signal AS1 or AS2. For a correctly functioning (non-failed) sensor, the response threshold distance S lies between the working distance A and a test threshold distance P. As long as the sensors operate within said tolerance range TB, each sensor emits a further output signal AS1 or AS2 when the metal part is located at a distance greater than the response threshold distance S.

However, for the further explanation of the inventive method it should be assumed that sensor S1 has failed beyond a predetermined maximum sensitivity threshold (response threshold distance S) such that it can also detect metal parts within the test threshold distance P. In this case, sensor S1 also produces an output signal AS1 when, for example, it faces the upstream test section PA11 . Therefore, although sensor S1 does not actually detect response segment AA1 , it falsely signals that the position to be located (for example the parking range of the vehicle door) has been reached due to its impermissibly high sensitivity. In this case, due to the safety connection via the computer R, the sensor S2 is missing (it actually also does not reach the response segment AA2, but works correctly and therefore does not likewise emit an output signal AS2 due to the high sensitivity) The output signal AS2 of the door is blocked from opening.

Using the method of the invention, a failure of this ultrahigh sensitivity of sensor S1 can be revealed in the manner described in detail below. For this purpose, the output signal behavior of sensor S1 is tested when the reference mark RM2 associated with sensor S2 is driven over and the other sensor S1 moves through the response range AA1 of reference mark RM1 associated therewith. In this hypothetical example it can be determined that sensor S1 does not produce a signal change (from output signal AS1 to output signal AS1). It can also be confirmed that the output signal of the sensor S1 will not change when the locomotive continues to move from the position shown in FIG. 1 to the moment when the sensor S2 leaves the response section AA2. Because sensor S1 still emits output signal AS1 in the area of test section PA12 due to its impermissibly high sensitivity. In contrast, a correctly functioning sensor would change the signal from output signal AS1 to output signal AS1 in this case.

To illustrate the process described above, Fig. 3 details the sensors S1, S2 in different positions relative to their corresponding reference marks RM1, RM2. Row ( 1 ) in FIG. 3 shows a situation where the sensors S1 , S2 are still in the test sections PA11 , PA21 before the respective response sections AA1 , AA2 . Correctly functioning sensors S1 , S2 do not emit a response signal, but a second signal AS1 or AS2 (see column under S1 and S2 in FIG. 3 ). Row (2) in FIG. 3 shows exactly a transition phase, when the sensor is in the transition zone between the test segment and the response segment. Due to structural internal tolerances and/or positional tolerances, sensor S2 has not yet changed its output signal, while sensor S1 has responded. However, sensor S2 also changes its output signal after a predetermined transition time and/or a distance has elapsed, which is indicated in the table by transition time Δt. When both sensors are within the response section AA1, AA2, they maintain their output signals AS1, AS2 (see third sensor position, row (3) of FIG. 3). The sensor locations shown in row (4) and row (5) in FIG. 3 show the sensor leaving the response section and the signal transitions associated therewith. Here too, there is a permissible transition time interval Δt, during which sensor S1 , which is the first sensor in the exemplary embodiment, changes its signal from the first output signal AS1 to the second output signal AS1 .

The last column in Fig. 3 is S1', in which the situation described above is shown in addition: the sensitivity of the sensor S1 is higher than the test threshold distance P (Fig. 1), so the sensor S1' has already sent The first outputs signal AS1. This output signal is present even when the sensor S1 reaches the response segment AA1 of the associated reference mark RM1 . According to the method of the present invention, the test period of the sensor S1 can be determined from the change of the output signal of the sensor S2, and at the same time, it is confirmed that the output signal of the sensor S1 does not change. (Stages related to testing are indicated by horizontal arrows in the table).

Claims (6)

1. A method of testing a dual sensor system of a locomotive (F) comprising two sensors (S1, S2), one of which has an inadmissible increase in sensitivity, wherein, - the two sensors ( S1 , S2 ) are driven in a direction of movement (B) past reference markers ( RM1, RM2), and when it is informed that an associated reference mark (RM2) is passed, it is detected by the sensor (S2) passing it that another sensor (S1) passes by its own reference mark (RM1) , and whether the sensor (S1) produces an output signal change when it moves from the range of its test section (PA11) into the range of the response section (AA1) or vice versa, wherein, - each fixed reference mark and each sensor (S1, S2) correspond to each other, taking into account the sensitivity field (EF) of the sensor, the sensor and the associated reference mark are selected and matched to each other, so that in a Sensors (S1, S2) operating within the permissible sensitivity tolerance (TB) give the first output signal (AS1, AS2) within the range of the response section (AA1, AA2), in the test section (PA12, PA21 ) gives a second output signal (AS1, AS2), while a sensor (S1) with a sensitivity exceeding an admissible sensitivity threshold (P) gives the Describe the first output signal (AS1). 2. The method of claim 1, - wherein said test is performed after exactly leaving said reference mark (RM1). 3. The method according to claim 1 or 2, - Therein, a test is carried out, namely whether the output signals of the two sensors ( S1 , S2 ) change within a transition time (Δt) or within an exact line section. 4. A method according to any one of the preceding claims, - wherein the response section (AA1) is preceded by a test section (PA11) and followed by a test section (PA12). 5. A method according to any preceding claim, - wherein the test section (PA11) directly adjoins the response section (AA1). 6. A device having a dual sensor system comprising two sensors (S1, S2) mounted on a locomotive (F) and two positionally fixed reference marks, which has an inadmissible The dual sensor system was tested at increased sensitivity where, - each sensor and each position-fixed reference marker (RM1, RM2) with a response section (AA1, AA2) and at least one test section (PA11, PA21) corresponds to each other, taking into account the sensor's sensitivity field ( EF), select the sensor and the associated reference mark and match them to each other so that the sensor (S1, S2) working within an allowable sensitivity tolerance (TB) is within the range of the response section (AA1, AA2) The first output signal (AS1, AS2) is given within the range of the test section (PA12, PA21), and the second output signal (AS1, AS2) is given within the range of the test section (PA12, PA21), while a sensor whose sensitivity exceeds an allowable sensitivity threshold ( S1) Gives said first output signal (AS1) even within said test section (PA11), additionally, - in the case of a dual sensor system, a computer connected to the sensor is provided which, when the sensor passes a reference mark in one direction of movement (B) and when it is informed that an associated reference mark (RM2) has been passed, is activated by Passing its one sensor (S2) to detect when another sensor (S1) passes by the reference mark (RM1) belonging to it, and this sensor (S1) enters the response from the range of said test section (PA11) Whether or not an output signal change is generated when the range of the section (AA1) is in motion or vice versa.

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