#Perimeter detection tools
Perimeter detection tools:
specifics of quality assurance
Technical detection tools (TDS) are devices designed to detect the intrusion of a person or other unregulated object into a protected area.
For these products, the environment with all the variety of its parameters and influencing factors is an integral part of their information channel, in which the «detection process» is implemented.
Therefore, the quality of perimeter detection equipment is largely determined by the extent to which the algorithms they implement and their electrical circuits are able to take into account external factors or adapt to them during operation.
Another feature of perimeter devices is that there is no way to experimentally test their basic performance characteristics (probability of detection, false alarm rate, operating temperature ranges, etc.), as a result of which the consumer is forced to rely entirely on the values of these characteristics declared by the manufacturer.
Under these conditions, the issue of the degree of reliability of the values of the basic characteristics of products of this type, presented in their operating documentation, in advertising and information leaflets and other technical documentation, is of particular importance.
Modeling Methods
Determining reliable values of technical characteristics of perimeter equipment is a complex, lengthy and labor-intensive process.
The lack of strict analytical approaches to predicting the characteristics of these products requires a mandatory cycle of research, during which the actual operating conditions of the product must be taken into account with maximum approximation.
Research into the influence of environmental factors on signal generation processes can be carried out in natural conditions, as well as using mathematical and physical modeling methods.
Mathematical modeling, despite the availability of high-performance computing technology, allows only preliminary estimates of the main parameters of perimeter equipment.
This is due to the lack of sufficiently correct theoretical methods for solving problems for near, reactive zones of physical fields located along the non-uniform earth's surface.
Physical modeling is used in cases where correct scaling of the parameters of transformation processes can be performed, for example, when studying television, infrared TSO, etc.
Neither mathematical nor physical modeling is able to fully reproduce real operating conditions that reflect the specifics of the use of perimeter equipment.
This explains the rather long development cycle of devices of this class and the inevitability of performing a large volume of research in natural conditions at the development stages, when the main technical solutions are laid down and the operating algorithms are determined.
Factors Affecting Perimeter TSO
Technical detection equipment used indoors is exposed to a small number of external factors (temperature, humidity, electromagnetic fields, etc.), the values of which change in fairly narrow ranges.
The circuit solutions of such perimeter devices are not particularly complex, and their operating conditions can be reproduced without much effort both at the development stage and during production, when monitoring parameters.
Determining reliable estimates of their main operational characteristics, such as sensitivity, noise immunity (probability of detection, false alarm rate) and others, does not require significant time expenditures or the creation of complex testing complexes.
The development and especially the production of such products are within the capabilities of even small firms, including those that do not have a serious scientific, production and testing base.
For this reason, there is a significant number of perimeter detection devices for indoor use on the market, manufactured by both domestic and foreign companies.
Standardized values for the conditions of use of such products depend little on the country in which they are manufactured, so foreign products have every right to compete with domestic ones on the Russian market, winning in design, organization of an advertising campaign and losing in cost.
Perimeter TSOs are much more complex products, since they must not only ensure reliable and effective functioning in the open air, but also be resistant to the impact of a large number of external influencing factors during operation, the values of which vary over wide ranges.
The table illustrates the potential susceptibility of the main types of perimeter TSOs to certain types of external factors.
The data in the table once again show that the creation of modern effective perimeter TSOs is impossible without conducting comprehensive studies of the influence of various external factors on their parameters.
The difficulty lies in the fact that external factors are random non-stationary processes distributed in time and space.
A significant part of them are seasonal natural phenomena, the extreme values of which change significantly and in some years do not reach the maximum values regulated for domestic perimeter TSOs.
For this reason, full-scale tests of products of this type can stretch over several years.
Tests of perimeter TSOs
In practice, only large enterprises that have at their disposal a test site, a set of wide-range standardized measuring and recording equipment, computer technology and methodological materials establishing the procedure for performing tests and measurements of the characteristics of these products can afford to carry out a full scope of research in the development of perimeter TSOs (due to their duration, labor intensity and complexity).
Most often, enterprises working in the field of perimeter detection equipment, but not having a long tradition of developing them, do not have a test site at their disposal, since its creation requires a lot of time and large material costs.
A typical testing ground for perimeter TSOs has an area of about 10-20 hectares, and measures have been taken on its territory to prevent unauthorized visits by outsiders. Natural conditions are created on the testing ground, as close as possible to the real conditions of use of these devices.
There must be certified test routes with standardized parameters, including relatively flat sections and sections of rough terrain with different types of surfaces — earth, rock, asphalt, concrete, etc., with various types of vegetation — grass, bushes (of standardized height), free-standing trees.
The test site is equipped with certified barrier structures of various types made of reinforced concrete, brick, wood, metal gratings and nets.
The standardized lengths of test routes and barriers — up to 500 m.
Perimeter TSOs on the test route and mesh fence of a typical test site are shown in the figures below
Meteorological conditions during testing should be measured and recorded to assess the correlation between the research results and environmental parameters.
The personnel of the test site, special measuring and computing equipment are located in the immediate vicinity of the test sites in an insulated room.
The high labor intensity of full-scale tests entails an increase in the cost of perimeter TSOs created by enterprises that carry them out in full.
Small companies in the process of developing perimeter TSOs conduct a limited set of full-scale tests, therefore the prices for their products are lower, however, the regulated values of the parameters and characteristics of the products often have insufficient reliability.
Under modern conditions, the manufacturer of perimeter TSOs must ensure their high quality and relatively low cost.
Therefore, the tests of perimeter TSOs performed during their serial production are subject to the requirement of high quality (reliability) of the tests while minimizing the cost and duration of acceptance tests.
The contradictory nature of the requirements is obvious, as is the need to implement them to ensure the competitiveness of products.
To resolve this contradiction, it is necessary to reduce the labor intensity and duration of inspections of perimeter TSOs while maintaining or improving their quality.
Physical Models
The most promising way to reduce the volume and labor intensity of full-scale tests when checking the main parameters that determine the quality of products is to use methods for modeling the parameters and conditions of interaction of perimeter TSO with the information environment.
The expediency of using physical models when determining the probabilities of detection and false alarms of perimeter TSO is embedded in the very specificity of such products.
Since the informative parameters used for detection in various «targets» have a significant random component, the reliability of the results of determining the sensitivity and noise immunity of perimeter TCUs using real «targets» whose parameters are not subject to any restrictions is low.
Regulating the requirements for the parameters of the «target» used in full-scale tests allows us to obtain a so-called «standard target», which is usually a person whose weight, size, and clothing parameters correspond to the standardized ones.
In addition, physical models of humans, animals and birds can be used in full-scale testing of perimeter TSOs, which are structural elements that provide standardized values of the informative parameter for the tested TSO.
Each of them is characterized by similarity to the modeled object only in the main informative parameter, therefore it is applicable only for testing TSOs based on one physical principle.
Thus, models of this type allow to some extent to regulate the parameters of the «target» used in assessing the parameters of the TSO, i.e. they ensure an increase in the reliability and reproducibility of test results.
However, they do not allow to significantly reduce the labor intensity of performing full-scale studies.
From the point of view of reducing the costs of acceptance tests, it seems promising to create scaled physical models for checking TSO.
In particular, for radio-beam two-position TSOs it is possible to create devices that perform scaled modeling of: attenuation in the atmosphere corresponding to the boundary climatic conditions, «target», imitation of animals and birds (for example, by introducing additional normalized attenuation between the receiver and the transmitter).
For radio wave TSOs, it is possible to scale the modeling of: the linear part of the TSO (taking into account the boundary values of the main influencing factors, such as temperature, «leakage» due to high humidity, etc.), «target», animals and birds (for example, by introducing normalized heterogeneity or attenuation into the linear part model).
Such models allow most TSO tests to be carried out in the quality control department of the manufacturer, but their use does not provide sufficiently reliable estimates of the sensitivity and noise immunity of the tested perimeter TSOs.
Modeling of electrical signals
One of the promising areas of development of modeling methods is the use of modeling electrical signals in testing of TSOs, based on the principle of strict separate standardization and verification of the parameters of the main components of the TSO, the receiver, transmitter and linear part (for radio wave TSOs), the electronic unit and seismic line (for vibration and vibroseismic TSOs).
In general, these modeling methods are based on the use of a library of electrical signals formed during full-scale testing, or artificially synthesized electrical signals.
In both cases, the parameters of the used (simulating) electrical signals must correspond to the actual signals present on the controlled components of the TSO under the worst of the actually possible combinations of operating conditions (in terms of environmental parameters and interference factors).
Obviously, the greater the number of external influencing factors taken into account when synthesizing the simulating electrical signals, the higher the reliability of the values of the assessed characteristics of the TSO obtained with their help.
This approach, successfully used in finding estimates of sensitivity and noise immunity of TSOs intended for indoor use, does not currently allow obtaining sufficiently reliable estimates of the main characteristics — the probability of detection and the operating time to false alarm for perimeter TSOs.
The reason for this is the difficulty of correctly taking into account, when synthesizing modeling test electrical signals, the maximum deviations of a wide range of external factors and possible maximum deviations of real parameters of the “target”. and «interference».
Thus, the specificity of perimeter TSOs does not allow for full-scale testing to be completely excluded from the manufacturing process of even proven serial products.
Therefore, the production of modern perimeter TSOs of the proper quality can only be carried out by enterprises that have at their disposal a test center with a technically equipped testing ground for full-scale testing and regulatory materials regulating the methods of measuring and testing the parameters of these products.
If a company producing perimeter TSOs does not have a testing ground and appropriate methodological materials, then the technical characteristics of the products presented in their operational documentation most often do not have the required reliability.
And in this case, the consumer is exposed to an unreasonable risk of receiving products of inadequate quality.