RU2434326C1 - Device for generating and transmitting safe control signals - Google Patents

Abstract

FIELD: information technology. ^ SUBSTANCE: device has a transmitting side which is in form of a paraphase signal generator, and a receiving side having a band-pass filter, a detector, a DC low-pass filter, and a threshold unit. The transmitting and receiving sides can be connected by a transmission line in form of a twisted pair in a shield. ^ EFFECT: high reliability and noise immunity. ^ 3 dwg

Description

The invention relates to automation, pulse technology and can be used to generate a control signal for the actuator in cases where the maximum achievable degree of reliability of the transmission of such a signal is required. The control system may contain one or more channels for generating and transmitting a safe control signal.

All modern control systems are characterized by high complexity: they include a large number of blocks - from processing signals coming from sensors to directly implementing control algorithms and ensuring the functioning of actuators. Such complexity and the presence of a large number of connections, in turn, lead to an increase in the likelihood of failures and failures, some of which can have fatal consequences. Built-in diagnostic systems improve the situation somewhat. But for large systems, they are also complex and, reducing the probability of critical situations by several orders of magnitude, have their own failures, which, in turn, must be controlled, etc. In such a situation, to increase the level of safety, it is optimal to use simple circuits and signals whose sole purpose of existence is to ensure safety, i.e. preventing the occurrence of so-called "dangerous failures" in the system. The practical implementation of this approach is discussed below.

Safe control signals (hereinafter referred to as safety signals) are used in devices of responsible use: in transport, for example, to permit train travel; in energy systems - to enable / disable the inclusion of motors, control valves, etc. In all cases, the presence of safety signals assumes the normal functioning of the system, and their disappearance (as a result of the correct operation of the safety unit or due to a malfunction in the transmitting or executive circuits) immediately transfers the system to a safe state (for a train, usually braking, for a reactor, plunging rods, etc.).

Thus, it is possible to formulate requirements for these signals at different stages: when they are generated, this is the maximum reliability; during transmission (and circuit integrity) - maximum noise immunity, when the circuit breaks - the impossibility of replacing these signals due to the effects of strong interference, shorting the line to the supply bus, etc.

A device for transmitting a paraphase control signal containing the first and second triggers and the first and second synchronized delay elements, the information inputs of which are connected respectively to the inverse inputs of the triggers, the installation inputs of which are connected to the inverse outputs of the second and first delay elements, the synchronization inputs of which are combined, the installation input “1” of the first and the installation input to “0” of the second delay elements are also combined (see RF patent 2085027, Н03К 5/135, 20-07-1997). When the paraphase input signals are mismatched, the output signal of the known device changes from “1” to “0” until a repeated installation signal arrives.

The disadvantages of this device include low noise immunity due to the small amplitude of the logical signals used to transmit information. The logic circuits used in the known device include a plurality of semiconductor elements (transistors) and radio elements (resistors and capacitors), so that their resulting reliability is also not high. And finally, the known circuit is not protected from the ingress of high voltage (supply voltage) to the output.

Closest to the proposed device is a device for generating and transmitting via a radio link control signals containing on the transmitting side a signal generator of main messages, a power splitter, first and second amplitude modulators, a paraphase amplifier and a transmitting system (RF patent 2163053, Н04В 7/22, 2001-02-10). In order to reduce the influence of concentrated and impulse noise, a frequency synthesizer, a decoder, a reference generator, a bandwidth generator, a synchronizer and an adder are introduced into the known device. On the receiving side, this device contains an antenna, an adder, a subtracting device, a synchronous detector, an amplitude limiter, a demodulator, a narrow-band filter and a polarization rotation block, a reference generator, a pulse shaper, a frequency synthesizer, a divider, a shift register, a code converter, a synchronizer, n keys, n bandpass filters, adder, frequency mixer, processing unit and lowpass filter.

However, in the known device does not solve the problem of ensuring safety when the circuit is broken or shorted to the supply bus. In addition, it is so complex that it itself has insufficient reliability.

The technical result expected from the use of the invention is to increase the reliability and noise immunity of a safe control signal transmission device by increasing the signal-to-noise ratio, creating a circuit with a minimum number of elements, but protected from open circuits or potential getting from them from power buses.

The system used to increase the level of security should have a low level of complexity of the elements and circuits included in it, which implies a high hardware level of reliability. At the same time, the reliability of the signals themselves is not subject to high requirements due to the fact that their disappearance unambiguously puts the system in a safe state.

This result is achieved by the fact that in the device for generating and transmitting safe control signals comprising transmitting and receiving sides, the last of which contains a series-pass bandpass filter and a detector, the transmitting side is made in the form of a paraphase signal shaper, and the receiving side is additionally equipped with low-frequency connected in series a constant voltage filter and a threshold block, while the output of the detector is connected to the input of a low-frequency filter of constant conjugation.

Figure 1 shows the signal arriving at the transmitting side, figure 2 shows a block diagram of the proposed device, figure 3 is an example implementation.

The device uses a paraphase signal generated by two outputs of the processor safety block sinusoidal or another, for example, in the form of a meander (Fig. 1), the maximum possible (in order to achieve high noise immunity) amplitudes for this system. When generating a signal, each of the outputs of the safety unit (not shown in Fig. 2) is independently controlled by its own program fragment, so any desynchronization should cause a mutual phase shift of the signals along the two outputs (i.e., they cease to be out of phase and a shift Δt )

The frequency of the signals is selected based on the lowest level of interference in the system in this region of the spectrum and should not coincide with the main or derivative frequencies of the generators, pulse converters, data buses, power electronics (thyristor converters, for example), electric motors, harmonics of the mains etc., and may be, for example, in the range of 10-50 kHz, if this satisfies the conditions listed.

In the example shown in figure 2, the transmitting side of the device is formed by two galvanically isolated outputs of the safety processor (conventionally shown as transformers 1, 2), voltage limiter 3 (diodes D1, D2 and zener diodes D3, D4 of the corresponding power) and high resistance to earth bus (resistors R1, R2).

As the transmission line can be used twisted pair 5 in the screen. The receiving side (figure 2) is a serial circuit of separation capacitors 6 (C1) and 7 (C2), a low-pass filter 8 of low quality (including an RFI suppression filter) of a common or individual low-frequency detector 9 for each input (with impossibility of parasitic detecting high-frequency interference - for example, due to junction capacitors or external capacitors), a low-frequency DC filter 10 that determines the time constant τ of the device and the threshold block (PU) 11 level determination rectified signal. The resulting constant voltage (current) is supplied to an actuator, for example an optocoupler switch 12 or other blocking / triggering elements of terminal devices.

Thus, the disappearance or change in the amplitude of any of the signals or a phase shift between them above a certain level reduces the rectified signal at the input of the threshold block 11, it becomes lower than the set threshold value, and the optocoupler 12, for example, is closed. The presence of a voltage limiter 3 (diodes D1, D2 and zener diodes D3, D4) protects the device in the event of a high-voltage alternating voltage entering any of the lines. In this case, a break in any of the lines and a short circuit with any supply voltage does not lead to a false response of the circuit to “resolution”.

An example of the practical implementation of the receiving part of such a circuit is shown in Fig. 3, while the diodes D6, D7 of the output transistor optocouplers 12 are used as a threshold block 11 (due to the sufficient slope of the current characteristic in the initial region), the receiving side is powered by a paraphase signal, coming through twisted pair 5, and the presence of additional capacities 13 (C5), 14 (C6), 15 (C7) and 16 (C8) parallel to the diodes D1-D4 of detector 9 along with the galvanic separation of the earth prevents the detection of high frequencies ny interference. Tanks 17, 18 (C3 and C4 in FIG. 3) form a band-pass filter 8, and the low-pass filter 10 is based on the tank 19 (C9).

Such a device is simple and yet quite effective. Using it, systems can be created with extremely high safety, where the probability of a dangerous failure is 10 ^-13 or less.

Bibliography

1. Clayton R. Paul Introduction to Electromagnetic Comparibility: John Wiley & Sons, Inc., 1992. - p. 765.

2. Analog Circuit Design: Art, Science, and Personalities. - Edited by Jim Williams: Butterworth-Heinemann, 1991 .-- p. 389.

3. Thompson, J.M.T. Instabilities and disasters in science and technology: Transl. From English. - M .: MIR, 1985 .-- 254 p.

4. GOST R ISO 13849-1-2003.

Claims (1)

A device for generating and transmitting a safe control signal, comprising a transmitting and receiving side, the last of which contains a series-pass bandpass filter and a detector, characterized in that the transmitting side is made in the form of a paraphase signal shaper, and the receiving side is additionally equipped with a low-frequency constant voltage filter connected in series and a threshold unit, wherein the output of the detector is connected to an input of a low-pass filter of constant voltage.

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