Fundamentals of the functional-ecological approach to system analysis and design
The functional-ecological approach provides not only a quantitative, but also a qualitative description of the technical system included in nature, thus allowing to connect the two areas of theoretical knowledge - mathematical and conceptual. Thus, new efficient solutions are found taking into account the performance of the functions of preservation of the environment, which have the minimum cost, required by society.
A function implemented by a technical system, or a technical function, reflects and describes its purpose. The description of the technical function should answer the questions:
1. What is the effect of the technical system?
2. On which object (subject of labor) is this action directed?
3. What is the result of the action?
4. Under what special conditions and limitations is this action performed?
Based on these requirements, in general, the technical function Φ can be described by the following formula:
where D is a description of the action produced by the technical system and leading to the desired result, i.e. to satisfaction (realization) of a certain need; G - the description of the object (subject of work), to which the action is directed; R - the result of the action; H is a description of the special conditions and restrictions (if any) for which the action is performed.
The above equation expresses the essence of the law of the structure of technology, consisting in the fact that in the material structure of a properly designed and normally operating technical system, each element (block, node, detail) and its constructive feature have a very definite function to ensure the operation of the technical system. And if you deprive the technical system of any element or constructive feature, it either ceases to function (perform its function) or worsen the performance of its work. In this regard, properly designed technical systems usually do not have unnecessary details .
In addition, in a technical system in which a sufficiently complete correspondence between functions and structure is achieved, an optimal parity of parameters that characterize the structure of the technical system and its elements and provide competitive values of efficiency criteria with the current limitations on the characteristics of the functions performed and external factors. In this case, the deviation from the optimal parameters leads either to noncompetitive values of efficiency criteria, or the technical system becomes inoperable - does not perform one or more of its functions.
The regularity of the functional structure for technical systems consists in the fact that man-machine technical complexes consist of four subsystems S1, , S 3, S4. These subsystems implement, respectively, four fundamental functions:
F1 - technological function, ensuring the transformation of the initial state of the object of labor A 0 into the final product of A ^,
F2 - is the energy function that converts the matter or the energy W0 obtained from the outside into a finite form of energy Wκ necessary for the realization of the function F1;
F3 - control function that performs the control actions U 1 , U 2 on subsystems S1, S 2 in accordance with the given program Q and the information received U 01 , U 02 on the quantity and quality of the final products produced A k and the final energy Wk;
F4 - planning function, collecting (receiving) information about the produced products A k and determining the necessary qualitative characteristics.
Machines, devices, apparatuses and other complex technical systems consist of functional elements in the form of blocks, nodes that perform qualitative and quantitative transformation of properties of flows of matter, energy or information signals. Each element has inputs, outputs, realizes a certain conversion function and is separated constructively.
In technical systems, among all subsystems (elements), as a rule, it is possible to single out the main subsystem, the work of which directly ensures the performance of the technical system function, and the remaining subsystems (elements) ensure the operation of the main subsystem.
In this case, the functions of the main subsystem and the entire technical system often coincide. The main subsystem is usually the core around which the remaining subsystems are grouped.
Subsystems usually have a certain relative position (rigid connections), are connected to each other through the transmission channels of matter, energy or signals (usually flexible connections) and have the necessary protection against unfavorable factors, which ultimately guarantees the integrity and performance of all subsystems. To provide these links between subsystems and their protection, additional costs are required, since they directly depend on the layout (relative positioning) of the subsystems. In this regard, environmental damage from the technical system is conditionally composed of two parts: the first - the total damage from individual subsystems, the second - the layout damage.
Practice shows that the most sophisticated, functionally organized systems in implementation require compliance with four basic principles.
1. The principle of compatibility of functions. The joint functioning of the elements of the system as a whole is possible only when they have the property of compatibility for the most significant types of connections and relationships. Accounting for the principle of compatibility is necessary when combining elements. Incompatibility by any type of communication should be compensated for by the introduction of intermediary links, which perform the functions of coordinating these elements. The cost of compatibility should be minimal. The degree of satisfaction of the principle of compatibility is characterized by the coefficients of the structural K c and the functional compatibility K :
where N with , F c - the number of elements (intermediaries) and functions respectively, performing only the coordination function (compensation); N o - the total number of useful (harmful) functions; F n is the total number of material elements (function carriers) in the system.
Another kind of compatibility indicator is the coefficient of contact K k.c between the elements of the system:
where - the number of contact links of the elements; - the total number of links (contact, correlation) between the elements of the system.
The more , the greater the complexity of manufacturing the system and the likelihood of its failure during operation. By analogy, the coefficients for correlation links are determined.
2. The principle of actualization of functions. In an ideal system, all functions should be useful. However, in real systems there are not only unnecessary and useless functions, but also harmful for the system, for the environment and for humans. When designing systems, the principle of actualization acts as a condition for the progressivity of the devices and technologies being created by using all the properties of elements in accordance with their functional character and preventing harmful, unnecessary and useless for the system functions and elements. Accounting for this principle contributes to improving the environmental friendliness of systems and saving resources in their manufacture and operation. The degree of satisfaction of systems by the principle of actualization of functions is determined by the coefficients of the useful functions and harmful coefficients of the img src="images/image193. jpg "> and harmful links:
where - the number of useful and harmful functions of the system (its components), respectively; - the number of useful and harmful links in the system, respectively; - the total number of functions (useful, harmful, useless) and links in the system, respectively.
3. The principle of concentration of functions. This principle involves concentrating the efforts of individual functions and elements on the implementation of the basic functions of the system. The degree of satisfaction of this principle is determined by the coefficient of functional realization
where - the number of basic useful and auxiliary (providing the performance of basic functions) of the system functions, respectively.
4. The principle of flexibility ( control ) functions. This principle determines the degree of satisfaction of the specified functions, which is provided by control devices (for example, automatic) or system self-tuning . The coefficient of the functional latitude is an indicator reflecting the degree of satisfaction with the principle of flexibility of functions:
where are potentially useful, adjustable and unregulated functions, respectively.
Thus, the main methodological core of functional-ecological design (FEP) of technical systems can serve a functional-structural approach that takes into account:
- the relationship of functions and the structure of the technical system with the defining role of the function in relation to the structure;
- a holistic approach to the analysis and synthesis of multilevel systems;
- material, energy and information links between the elements of the system;
- the relationship between the technical system and the external environment;
- consideration of the system in development;
- the use of general laws of the material world and the patterns of development of systems of a certain class.
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