EP1378923A2 - Method for evaluating switching signals and apparatus therefor - Google Patents

Abstract

The signal in the first path has a switched-on state (S1) and a switched-off state (S1'). The signal in the second path (S2,S2') is an inverse of the first signal. Switching on and off occur at given times (t1-4). When the first signal is switched off, the second signal is switched on during a short switching period (ts). Switching off of the second signal may trigger switching on of the first signal during the switching period. The output signal (S3,S3') is derived by switching on when the first signal switches off and off when the second signal is switched off.

Description

The invention relates to a method for evaluation of switching signals one between an idle state and one Actuator status of switchable signal transmitter. Such a thing Procedure takes place in particular for monitoring one for the Generation of safety-related signals provided by the signal generator Use. It is used in particular for detection control signals incorrectly generated by the signal generator. The invention further relates to one, in particular Device for producing according to the above method and evaluation of switching signals.

The conception and development of industrial machines and systems is characterized by an increasing use of security technology. In this case, in particular with a simple peripheral device, e.g. one as a push button executed signal generator, a malfunction excluded be or, to initiate safety-maintaining steps, be recognized. In a conventional push button switch with mechanical Contacts is a complete detection of errors particularly complicated by the fact that jamming of the Touch mechanism is barely recognizable electronically. This is problematic, especially since mechanical pushbuttons at almost all industrial machines and systems on operator panels or control consoles are used and therefore also in terms of safety are important. Areas of application are for example in power plant engineering, traffic engineering, Chemical plants, generally in mechanical engineering for tool and Production machines, passenger lifts, crane systems, air and Space technology etc. Affected application functions are among others general start and stop functions, traverse keys of drives, the control of valves as well general approval and monitoring functions, such as so-called "dead man's buttons".

To safely process signals generated using mechanical buttons Being able to do so will often result in redundant signal generation required. A safe, but technically there is a complex method for redundant data generation therein, several separate and for triggering a control process to provide signaling devices to be operated simultaneously, so that in the event of failure of a signal generator or the signal generator containing signal paths further signal paths to Transmission of the security-relevant information available stand. Such a system is generally only two-handed to use and thus from a work economy perspective disadvantageous. Alternatively, it is common for a simplified Handling multiple signal transmitters in one push button switch to combine, so that for redundant signal generation can be operated together in a single operation. The realization of such a button, as for example is known from DE 199 46 471 A1, but is technical complex and therefore costly.

From the area of so far mainly for input purposes, e.g. in a keyboard, short-stroke switches or Membrane switches are now known in which a mechanical malfunction, especially jamming the switching mechanism, excluded by constructive measures is. For example, one is known from US Pat. No. 5,990,772 Button switch known, in which the reset of the Switch contact in the idle state under the action of a Magnetic force takes place. To such a mechanically fail-safe Signal generator for the generation of safety-related To be able to use switching signals, one is required the signal generator cooperating process, which to effective detection of possible fault conditions is.

The invention has for its object a method for Evaluation of switching signals indicate that in particular simple way to identify faulty operating conditions one between an idle state and an actuation state switchable signal generator is suitable. In particular, that should Be suitable for monitoring a signal transmitter, in which a mechanical malfunction is excluded is. Furthermore, the object of the invention based, a particularly simple, for generation and evaluation to indicate suitable devices for safety-related signals.

With regard to the method, the task is solved by the Features of claim 1. Then the signal state in two signal paths connected by the signal generator are time-resolved determined and analyzed, one of the analysis result dependent output signal to control a technical Plant is generated. Analysis of the signal state of the two Signal paths follow the following rules. If both signal paths correspond to the idle state Have signal state, a first, indicating the idle state Output signal generated. This signal configuration is referred to below as the first operating state. In a second operating condition is provided that both signal paths correspond to the operating state Have signal state to display the actuation state generates a second output signal. A regular one Change between the first and the second operating state is only allowed if within a given Target switching time a change in the signal state in both Signal paths are done. Otherwise, i.e. if outside of one regular change of the operating state neither of the two operating states there is a faulty operating state recognized and an error message issued.

With regard to the device, the object is achieved according to the invention solved by the features of claim 6. After that is a between an idle state and an actuation state switchable signal generator is provided, which on the output side two signal paths is connected to an evaluation unit to analyze the signal state of the two signal paths above rules, and to generate a corresponding output signal Is provided.

Under time-resolved determination of a signal state understood that in addition to the current signal state information about at least one past signal state of the same signal path is available, so that based on their Comparison of a change in the signal state is recognizable. The Alternatively, the signal state is determined continuously or discontinuously, two consecutive Determination times maximum at the target switching time are spaced.

With the method according to the invention and the associated device is advantageously a safe generation of Switching signals and efficient detection of faulty Switching operations of the signal generator achieved. When using the Procedure can be followed while respecting security requirements a conventional, two-pole push button switch as a signal generator can be used, provided a mechanical Failure is constructively excluded. The invention Device can therefore be compared to the conventional Standard considerably simplified with the same security be trained.

The target switching time is preferably approximately 20 milliseconds. This target switching time is thus a default time, which is expedient short of human response time and is therefore short compared to typical switching periods. On the other hand, this target switching time is sufficiently long compared to the actual switching time of a conventional one Signal generator that is on the order of a millisecond lies. To be fast and reproducible, and to produce switching behavior that can be easily checked, has the signal transmitter expediently a snap switching behavior on. In other words, the Signal generator regardless of the course of the actuation force over time forcibly within a structurally determined Switching time.

In an advantageous embodiment of the invention, the two are Signal paths in both operating states with regard to their Signal state connected to each other inversely. So is from Apart from the moment of switching, the first signal path, for example leading the signal, so the second signal path Zero signal on, and vice versa. So in every regular Operating state of one of the signal paths carrying the signal. On this way is a line break or some other errors leading to signal loss even during stationary Operating phases immediately recognizable. Such an inverse Wiring the two signal paths is particularly easy Wise with a changeover switch Signal generator possible.

To quickly locate the source of the error in the event of an error can, a differentiated error message is expedient output, which indicates the type of error that occurred. Preferably, the error message continues to be sent simultaneously generates an emergency stop signal as an output signal, which the controlled technical system in a safe state transferred.

In view of its low susceptibility to errors comes preferred a short-stroke key switch is used as a signal generator. A short-stroke key switch is still more compact because of this Size particularly advantageous in an operating device or to integrate a control panel of a technical system.

FIG 1

schematisch eine Vorrichtung zum Erzeugen und Auswerten von Schaltsignalen mit einem, in seinem Ruhezustand befindlichen Signalgeber und einer dem Signalgeber nachgeschalteten Auswerteeinheit,

FIG 2

die Vorrichtung gemäß FIG 1 im Betätigungszustand des Signalgebers,

FIG 3

in einem zeitlichen Diagramm Eingangs- und Ausgangssignale der Auswerteeinheit im Normalbetrieb und

FIG 4

in einer Darstellung gemäß FIG 3 Eingangs- und Ausgangssignale der Auswerteeinheit in beispielhaft ausgewählten Fehlerfällen.

Exemplary embodiments of the invention are explained in more detail below with reference to a drawing. In it show:

FIG 1

schematically a device for generating and evaluating switching signals with a signal transmitter which is in its idle state and an evaluation unit connected downstream of the signal transmitter,

FIG 2

1 in the actuation state of the signal transmitter,

FIG 3

in a time diagram input and output signals of the evaluation unit in normal operation and

FIG 4

in a representation according to FIG 3 input and output signals of the evaluation unit in selected error cases.

Corresponding parts and sizes are in the figures marked with the same reference numerals.

The device 1 shown in FIG 1 for generating and Evaluation of switching signals includes one as a push button trained signal generator 2, the type of a changeover switch optionally a signal input 3 with one of two Signal outputs 4 and 5 connects. The signal generator 2 is preferred executed in a short stroke technology. such Short-stroke key switch, as is usually the case in a keyboard, especially membrane keyboard, are used due to extremely compact size and extremely low susceptibility to errors out. A suitable short stroke technology, in which one Malfunction due to jamming of the switching mechanism is excluded by structural measures, for example known from US 5,990,772.

1 shows the signal generator 2 in its idle state. there the signal input 3 is conductive via a switch contact 6 connected to signal output 5 while the connection interrupted between signal input 3 and signal output 4 is. The signal input 3 of the signal generator 2 is connected on the input side to an input line 7, via which the signal input 3 an input signal S0 in the form of a constant electrical low voltage supplied becomes.

The signal output 5, at which in accordance with the in FIG Switch position of the signal generator 2 voltage shown is present, is via a first signal path 8 with an evaluation unit 9 connected. The voltage output 4, at which at rest no voltage is across a second signal path 10 also connected to the evaluation unit 9. in the In the idle state, the first signal path 8 thus has an active, i.e. Live, signal state S1 while on the second signal path 10 in a passive, i.e. energized, Signal state S2 is.

The signal state S1, S2 is both in the evaluation unit 9 Signal paths 8 and 10 recorded time-resolved and as required rules described in more detail below. The evaluation unit 9 generates a corresponding one based on the analysis result Output signal S3 and transmits this via a Output line 11 to a component, not shown a technical system. For example, it is this component is about the drive of a movable Part of a machine tool.

An ensemble of signal states S1 and S2 and an associated one Output signal S3 at a given time hereinafter referred to as the operating state of the device 1. The with the proper functioning of the device 1, the idle state the operating state assigned to the signal generator 2 referred to as the first operating state. Appropriate sizes S1-S3 are shown uncoated. The one in the actuation state in contrast, the assigned operating state is as designated second operating state and by dashed Sizes S1'-S3 'marked. Analog mark two-line Signal states S1 ", S2" an incorrect operating state and the output signal S3 "if necessary in the event of an error issued emergency stop signal.

If the evaluation unit detects a faulty ensemble of signal states S1 ", S2", so it gives a signal line 12 an error message F to an error indicator 13. The error message F preferably contains specific information about the type of error detected. The error indicator 13 makes, e.g. by a suitable sound or light signal, on the one hand, be aware that an error has occurred. On the other hand, he identifies on the basis of the error message F information contained the type of error and thus facilitates fault finding.

A first state corresponds to the idle state shown in FIG Operating state in which the signal state S1 in the signal path 8 "active", and signal state S2 in signal path 10 is "passive". As belonging to the first operating state there the evaluation unit 9 a zero signal as the first output signal S3 off, which for example as a stop command for one machine drive, not shown, can be used can.

The activation of the signal generator 2 is carried out according to FIG 2 by Applying manual pressure K to an actuator 14 of the signal generator 2. As a result, a only indicated switching mechanism 15 of the switching contact 6 in switched its operating state. In this operating state the signal input 3 is connected to the signal output 4, while the connection between signal input 3 and the signal output 5 is interrupted. In the second operating state is thus the signal state S1 of the signal path 8 "passive" while the signal state S2 'of the signal path 10 is "active". As belonging to this second operating state The evaluation unit 9 generates a constant, positive output signal S3 ', which in turn e.g. as a start command Machine drive, not shown, can be fed.

The evaluation unit 9 allows a change between the first and the second operating state, in particular one Change between the first and second output signal S3 or S3 'only when there is a corresponding change in the signal state S1, S1 ', S2, S2' in both signal paths 8 and 10 within a predetermined target switching time ts.

Proper switching processes between the idle state and the operating state, and corresponding to the first and second Operating state, are shown in FIG 3 in a time diagram shown. Here is the time course of the signal states S1, S1 'and S2, S2' shown above the time axis t. The time course of the output signal S3, S3 'is shown below the time axis t. With that, the diagram 3 underlying switching cycle is at the time t1 the signal generator 2 is actuated. This is the active one Signal state S1 in the passive signal state S1 ' and the passive signal state S2 into the active signal state S2 '. The signal generator 2 has a snap switching behavior. This means that regardless of the time course of the actuation pressure K the switching process with proper function of the signal generator 2 always within a predetermined Period of time. In particular, at time t1 Signal loss in signal path 8 due to the mechanical inertia of the signal generator 2 in time before the signal build-up in the signal path 10. However, both processes take place within the the target switching time ts following the time t1. Because at the time t1 the change of state in time in both signal paths 8 and 10 takes place, the evaluation unit 9 switches from the first Output signal S3 to the second output signal S3 '.

At time t2, the actuator 14 is released. The switch contact 6 jumps within the switching time ts back to the idle state. Because of the mechanical inertia of signal generator 2, the signal is lost in signal path 10 again before the signal build-up in signal path 8. Da the signal change at time t2 again within the If the desired switching time ts takes place, the evaluation unit 9 in turn leaves the change to the first operating state. Another, operation phase analogous to the switching cycle described above takes place between times t3 and t4.

While in FIG 3 a proper switching of the device 1 is shown, FIG. 4 shows faulty switching processes shown as an example. Through an oblique, parallel Line pair 16 is an interruption of each Time axis t and the respective state curves marked. An incorrect operating state occurs, for example then when when the signal transmitter 2 is not in two signal paths 8 and 10 within the target switching time ts a change of state takes place. Such a mistake as he made, for example from a defective switching mechanism 15 or one oxidized switch contact 6 can be generated occurs according to 4 at time t5. This is where the Signal state S2 'delayed by more than the target switching time ts compared to the decay of the signal state S1. After lapse the target switching time ts are both signal states S1 "and S2" "passive". The evaluation unit 9 recognizes this as irregular operating state and triggers a corresponding error message F out. Even if, as in FIG. 4, the signal state S2 "becomes" active "at a later time, leaves the Control unit 9 changes to the second operating state does not admit and continues to output the safe zero signal.

The inverse error case, namely a late return of the Signal generator 2 in the idle state, occurs according to FIG Time t6. After waiting for the target switching time ts after The evaluation unit generates deactivation of the signal state S2 ' again an error message F. At the same time it switches on the output side back to a zero signal and thus generates the safe output signal, also known as an emergency stop signal S3 ".

In a further error case occurring at time t7 the signal path 10 switches to an active signal state S2 " without a signal loss in signal path 8 taking place beforehand is. Such an error can occur, for example a short circuit in the lines 7,8,10 or in the signal transmitter 2 may be caused. The active signal state S1 ", S2" of both Signal paths 8 and 10 in turn is considered an irregular operating state recognized and a corresponding error message F issued.

Activated in the reverse case of error occurring at time t8 the signal path 8 without the signal state S2 would have become passive beforehand. Simultaneously with the generation The error unit F is based on the evaluation unit 9 by generating the output signal S3 "in the safe emergency stop state back.

When using a two-way switch as signal generator 2 is a temporary signal loss in the course of the switching process normal in both signal paths 8 and 10. An operating state during which both signal paths 8 and 10 are active however implausible regardless of its duration. In the event of the error occurring at times t7 and t8 reacts the evaluation unit 9 therefore without delay.

There are various alternative embodiments of the invention Process and the associated device conceivable. In particular, the output signals S3, S3 'and S3 " in the form of signal pulses instead of constant in time Signals are generated. The output line 11 can be multi-channel for the separate output of the output signals S3, S3 'and S3 ". The signal paths 8 and 10 can optionally be be redundant. Instead of a changeover switch a pushbutton switch can also be used as signal transmitter 2, in which the signal paths 8 and 10 by parallel switching contacts, in particular an opener-closer pair become.

Claims (9)

Method for evaluating switching signals of a signal transmitter (2) which can be switched between an idle state and an actuation state, in which the signal state (S1, S1 ') in a first signal path (8) and the signal state (S2, S2') in a second signal path (10 ) are determined and analyzed in a time-resolved manner, and in which an output signal (S3, S3 ') dependent on the analysis result is generated, wherein (a) a first output signal (S3) is generated in a first operating state if the first signal path (8) and the second signal path (10) have a signal state (S1, S2) corresponding to the idle state, (b) a second output signal (S3 ') is generated in a second operating state if the first signal path (8) and the second signal path (10) have a signal state (S1', S2 ') corresponding to the actuation state, (c) a change between the first and the second operating state is only permitted if a change in the signal state (S1, S2, S1 ', S2') in both signal paths (8,10) within a predetermined target switching time (ts) takes place, and (d) otherwise an error message (F) is output. A method according to claim 1, characterized in that the target switching time (ts) is approximately 20 ms. Method according to Claim 1 or 2, characterized in that the first signal path (8) and the second signal path (10) have an inverse signal state (S1, S2; S1 ', S2') to one another both in the first and in the second operating state. Method according to one of claims 1 to 3,
characterized in that the error message (F) contains an error type specification. Method according to one of claims 1 to 4,
characterized in that an emergency stop signal (S3 ") is generated as an output signal at the same time as the error message (F). Device (1) for generating and evaluating switching signals with a signal transmitter (2) which can be switched between an idle state and an actuation state and which is connected on the output side to an evaluation unit (9) via a first signal path (8) and a second signal path (10) the evaluation unit (9) is designed such that it (a) generates a first output signal (S3) in a first operating state if the first signal path (8) and the second signal path (10) have a signal state (S1, S2) corresponding to the idle state, (b) generates a second output signal (S3 ') in a second operating state if the first signal path (8) and the second signal path (10) have a signal state (S1', S2 ') corresponding to the actuation state, (c) a change between the first and the second operating state only takes place if a change in the signal state (S1, S1 '; S2, S2') in both signal paths (8, 10) takes place within a predetermined target switching time (ts) , and (d) otherwise outputs an error message (F). Apparatus according to claim 6, characterized in that the signal transmitter (2) has a snap switching behavior. Apparatus according to claim 6 or 7, characterized in that the signal transmitter (2) switches in the manner of a two-way switch between the first signal path (8) and the second signal path (10). Device according to one of claims 6 to 8, characterized in that the signal transmitter (2) is designed as a short-stroke key switch.

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