1.1. Formulating Functions

The function of a technical object can be regarded, on the one hand, as its purpose and, on the other hand, as a certain action that it performs, which determines its usefulness and its consumer properties.

For example, the function of a knife – is to cut hard material. It can perform this function if it has certain properties, for example, if it is sharp and its dimensions correspond to the object being processed.

The functioning of technical objects very often consists in performing certain operations to convert substances and fields in order to detect, measure or change some other objects.

For example: an electric motor – converts electrical energy into mechanical motion; a bracket – transfers the load from some component to the load-bearing part of the structure; lubricant reduces the friction force in a moving joint of parts; a strain gauge – converts the deformation of a structure into an electrical signal.

As already noted, when formulating functions, two goals can be set, depending on the task to be solved.

1. To formulate a specification for creating a new TO.

This is a preparatory stage for determining possible physical operations (see Error: Reference source not found) and synthesizing possible variants of the physical operating principles (PhOP) of the TO being designed.

2. To carry out a functional analysis of an already developed TO in order to identify its shortcomings and improve it.

In both cases, in order to determine the function of a technical object, it is necessary to answer the question “What operation does it perform or should it perform?”.

Therefore, the formulation of a function must specify the action performed, the object toward which this action is directed, and the circumstances under which this action takes place (or must be performed).

< Action > <Function object > < Circumstances>

< Action > – a verb in the infinitive form, denoting a direct action;

< Function object > – the item toward which the action is directed;

<Circumstances> – the spatio-temporal and substance-field characteristic of the conditions under which the action must be performed.

For example, to measure the temperature of a solid body in the range from –50 to + 500 C. To protect a radio-electronic unit from vibration in the frequency range from 20 to 1000 Hz and from an overload varying according to a linear law from 5 to 20g.

The formulation of a function – is a specification for developing the object. Therefore, it is important that this specification, on the one hand, be specific enough for it to be clear in which direction to look for a solution and what means (resources) can be brought to bear. On the other hand, it is important that this formulation not narrow the search area or give rise to psychological inertia. Therefore, the formulation of a function should not contain even a hint of a possible operating principle of the device being created, still less of a possible technical or design-and-technological solution.

The action can be formulated in two ways: either by using a verb, or by using a verbal noun (Table 9 .1).

When using the verbal form, the action must be expressed by a verb of direct action that specifies the task precisely. Verbs of indirect action, for example, improve, eliminate, achieve, ensure, prevent, etc., generally do not give clarity to the formulation of the task. Therefore, their use is not recommended.

Table 9.1 Two forms of describing the function of a technical device

The form using a verbal noun describes the purpose of the object, and in a number of cases turns out to be more natural.

The object of a function can be expressed either by a concrete concept denoting a material object, for example, some substance that needs to be changed or detected: shape a part, stir a solution, fix a mechanism in a given position (a latch), detect the presence of carbon monoxide in a given medium, etc. Or by an abstract concept denoting certain simple properties of a substance, field, or process in which something needs to be detected, measured, changed, or transformed.

For example, measure the temperature of a medium, shut off the flow of a liquid, regulate the flow rate of a gas etc.

The process of checking tightness – determine the locations (field characteristic) and the amount of leakage of the medium (parameter).

The property must be simple and characterized by a single parameter.

In the formulation of a function, one must not use the names of properties that are characterized by several simple ones, for example, increase reliability, cost-effectiveness, quality. Reliability – is a complex indicator, characterized by particular indicators: durability, failure-free operation, maintainability, and storability.

Therefore, in the formulation: increase reliability… it is unclear what is meant.

The concept of cost-effectiveness is very broad; it needs to be specified, for example, economic efficiency, fuel efficiency.

Quite often an object must perform not one but several functions. And if it fails to perform even one of them, the usefulness of this object is lost.

Several functions can be related or stand in a relation of subordination.

In the formulation of the main useful function, all necessary related functions must be indicated. For example, a Check valve – pass the working medium in one direction and not pass it in the other. A Lifting crane – lift and move a load. A Jig bushing – determine the position of the tool (drill) relative to the locating datums of the fixture and guide its movement during machining.

If a TO must perform several functions, it is necessary to check whether they stand in a relation of subordination. A subordinate function reflects an additional requirement. This does not mean that it is less important. Without performing this function, the consumer properties of the TO may be lost. It is simply that the subordinate function can be performed only after the subordinating one has been performed.

For example, the frame of a bicycle – hold parts and assembly units in a given mutual position (F1), and maintain this position under the action of loads on it, i.e. ensure the rigidity of the structure (F2). Function F2 is subordinate to F1. F2 – is an additional requirement.

In the case of function subordination, only the formulation of the subordinating function needs to be given. The subordinate function will belong to an auxiliary function.

Machine tool fixture: determines the position of the workpiece on the machine tool (F1), holds the workpiece in a given position (F2) and absorbs the cutting forces (F3). These are related functions. And the requirement to have high rigidity, i.e., not to deform during machining (this leads to the appearance of an additional error), – is a subordinate function. It can be performed if the first three functions are performed.

Experience shows that even people who have skills in conducting functional analysis do not always immediately manage to clearly formulate the functions of the objects under study.

Therefore, it is recommended to first formulate the function in the form in which it naturally arises from the conditions of the problem being solved. Then select synonyms and choose the most capacious term, i.e., generalize the concepts involved in the formulation, both with respect to the action and with respect to the object.

For example, a Meat grinder – cut meat.

Such a specific formulation orients one toward using precisely this principle of action – to cut. A more general formulation: grind the product encourages the search for other principles of action.

And the formulation process the product is so general that it is already unclear what action is being referred to. This could be: clean, mix, remove etc.

The formulation of functions – is a model of the problem, and like any model, it must be pragmatic and possess heuristic power. Therefore, one must find formulations that facilitate progress in solving the problem.

If a prototype exists or a rough sketch of the technical object has been designed, then carrying out a functional analysis to improve it has certain features.

The first stage of this task is the identification of functional components, for which the functions they perform are formulated.

For the identified functional components, typical errors in the formulation of a function are either narrowing of the function or its broadening.

To make sure that the formulated function is correct, it is necessary to.

1. Identify the working element (WE) of the TS. It is precisely this that directly participates in performing the MUF. All other functional components participate in performing the MUF indirectly, – through the WE. For this, it is necessary to look at which component of the TS the energy and control signal are supplied to.

If a TO performs several functions, it can have several working elements. For example, a cargo truck – move a load, presupposes the presence of two functions: placement of the load (the body) and movement (the propulsion unit).

2. Check whether the TO itself can perform the formulated function.

3. Check whether several of the identified functions stand in a relation of subordination. For this, it is necessary to analyze whether the TO under consideration performs any other functions. And if it does, – then, whether all the functions it performs are independent or are related to one another.

4. Check whether a narrowing of the function or its broadening has occurred.

For this, it is advisable to describe why (for what purpose) this function is performed. And to check whether the function corresponds to the requirements imposed on it.

Here it must be noted that the object of a function is always some component of the nearest SS or a property characterizing the supersystem.

For example. An electric lamp: emit light, WE – the filament.

A light fixture: illuminate objects, TO – the light fixture, CE – the filament, WE – the reflector, the diffuser.

The function of the lamp is to emit light. One could say: convert electrical energy into light energy. But this second formulation already orients one toward the use of electrical energy. That is, this formulation excludes from consideration other physical operating principles for obtaining light.

For example, in the formulation of the function of the jig bushing: determine the position of the tool relative to the workpiece, a broadening of its function has occurred. This function is performed by the fixture as a whole.

The MUF of a technical object as a whole or of its component – is the fulfillment of the requirements of the first higher-level system. Therefore, it is advisable to carry out the formulation of the functions of the TO and its components simultaneously with the analysis of the connections between the functions performed by its components.