Text 7 . Systems – Open and Feedback

Systems can be classified as "open" systems or "feedback" systems.

An open system is one characterized by outputs that respond to inputs but where the outputs are isolated from and have no influence on the inputs. An open system is not aware of its own performance. In an open system, past action does not control future action. An open system does not observe and react to its own performance. For example, a watch, taken by itself, does not observe its own inaccuracy and adjust itself – it is an open system.

A feedback system, which is sometimes called a "closed" system, is influenced by its own past behaviour. A feedback system has a closed loop structure that brings results from past action of the system back to control future action. One class of feedback system – negative feedback – seeks a goal and responds as a consequence of failing to achieve the goal. A second class of feedback system – positive feedback – generates growth processes wherein action builds a result that generates still greater action.

A feedback system controls actions based on the results of previous actions. A watch and its owner form a negative feedback system when the watch is compared with the correct time as a goal and is adjusted to eliminate errors. Bacteria multiply to produce more bacteria which increase the rate at which new bacteria are generated. In this positive feedback system the generation rate of new bacteria depends on the bacteria accumulated from past growth of bacteria.

Whether a system should be classified as an open system or a feedback system is not intrinsic to the particular assembly of parts but depends on the observer's viewpoint in defining the purpose of the system.

The way in which the purpose of the system determines whether it is an open or a feedback system can be illustrated by considering a gasoline engine in terms of a series of viewpoints.

1. The engine, operating without a governor, has no goal for speed, it is an open system in terms of speed regulation. Changing the throttle will change the speed but the speed has no effect on the throttle. Furthermore, changes in load will change the speed without causing a throttle adjustment.

2. Adding a governor produces a feedback system in terms of a constant-speed goal. Changes in load cause changes in speed which produce a compensating change in throttle setting as the governor tries to hold the speed for which it has been set.

3. But suppose the engine is part of a lawn mower and we change the goal from constant-speed operation to a goal of mowing the lawn. Now, from the broader purpose of cutting grass, the lawn mower is an open system because it has no awareness of what grass has been cut or where to cut next.

4. By adding the person operating the lawn mower, we again see a feedback system in terms of the goal of cutting a particular lawn. The operator and mower form a feedback system (that is, a goal seeking system) rather than an open system (that is, one not striving for an objective) because the guidance of the mower is in accordance with the pattern of grass already cut.

5. But if the viewpoint is broadened again to that of the owner of a lawn-care enterprise with a goal of meeting his customer’s demands, the operator and his lawn mower are properly considered a component of a larger manage­ment system. As such, the operator and his equipment represent an open system that is undirected in its sequence of separate tasks.

6. By adding the management function, instructions arising from customer’s requirements are introduced as a guide. In terms of the goal of properly scheduled work, the operator, equipment, and owner must be taken together to form a feedback system for the purpose of serving customer’s lawn-care needs.

A broad purpose may imply a feedback system having many components. But each component can itself be a feedback system in terms of some subordinate purpose. One must then recognize a hierarchy of feedback structures where the broadest purpose of interest determines the scope of the pertinent system.

 

Exercise 55. Answer the questions on text 7.

1.  How can systems be classified? 2. What is an open system? Give your own example of an open system. 3. What is a feedback system? Provide your own examples.

 

Exercise 56. Translate the sentences paying attention to the meaning of indefinite pronoun “one”.

1. One must recognize a hierarchy. 2. One must do one’s best. 3. One has to show one’s pass at the door. 4. One must examine the equipment before the use. 5. One has to consider the viewpoints properly.

 

Exercise 57. Translate the sentences paying attention to different meanings of the word “term”.

1. Under the terms of the contract, the debt would be repaid over 20 years (condition). 2. We were soon on first-name terms (relationship). 3. The exams are at the end of the summer term (university). 4. The agreement reaches its term next year (end). 5. In the long term, alcohol causes high blood pressure (period of time). 6. It would be wrong to describe society purely in economic terms (a particular way). 7. Many legal terms have more than one meaning.  8. These developments are loosely termed advanced manufacturing techniques (terminology).

 

Exercise 58. Fill in the blanks with appropriate conjunctions, adverbs or prepositions.

(As a result, in terms of, compared to, in accordance with, owing to, furthermore, in consequence).

1. All flights have had to be cancelled … of the pilots strike.    2. Feminity is still defined … beauty. 3. … our small flat, his house looked like a palace. 4. Use this product only … the manufacturer’s instruction. 5. … bad weather, this morning flight will be delayed.   6. He is old and unpopular. … , he has at best only two years of political life ahead of him. 7. She was over the age limit and, … , her application was rejected.

 

Exercise 59. Give plural forms of the following nouns: bacterium, analysis, datum, erratum, phenomenon, basis, crisis, memorandum, aircraft, customs-house, hotel-keeper, diagnosis.

 

Exercise 60. Put 5 questions of different types to the sentence:

A feedback system controls action based on the results from previous action.

Exercise 61. Translate the sentences paying attention to the meanings of –ing forms.

1. The engine operating without a governor has no goal for speed. 2. Adding a governor produces a feedback system. 3. The heating system represents a negative feedback system seeking the goal of proper temperature. 4. The observer’s viewpoint in defining the purpose of the system is complex.

 

Exercise 62. Translate into English using –ing forms.

1. Розмножуючись, бактерії продукують ще більшу кількість бактерій. 2. Підстригання трави є невід’ємною складовою догляду за газоном. 3. Вугілля, дизельне паливо, газ, дрова та електрику використовують для опалення будинків. 4. Досягнувши мети, люди відчувають задоволення.

Exercise 63. Compose a dialogue on “Open and Feedback Systems”.

 

Exercise 64 . Learn the following words and word combinations.

the latter	– останній (з перелічених)
in sequence	– один за одним; послідовно
erroneous	– помилковий
apparent	– явний, видимий
distortion	– викривлення
cause-and-effect	– причина та наслідок
inventory	– облік товарів
continuous operation	– безперервна дія/режим
correspond	– відповідати чомусь
present instant	– даний момент
cease	– зупиняти дію
digest	– класифікувати, систематизувати
discrepancy	– невідповідність
as a practical matter	– практично

 

Exercise 65. Read, translate and give the gist of text 8.

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