Text 4. Regulators and Servomechanisms

The block diagram of a typical feedback control system is shown in Figure 3.

 

Figure 3. General feedback configuration

 

Here we are considering linear time invariant systems which can be represented, after Laplace transformation, in terms of the complex variable s. In Figure 3 the vectors u and у represent (the Laplace transforms of) the plant inputs and outputs respectively, d represents disturbance signals reflected to the plant output, n represents measurement noise and r represents the reference signals to be tracked. The plant and the feedback controller are represented by the rational proper transfer matrices G(s), and C(s) respectively, while F(s) represents a feedforward controller or prefilter. The usual problem considered in control theory assumes that G(s) is given while C(s) and F(s) are to be designed. Although every control system has a unique structure and corresponding signal flow representation the standard system represented above is general enough that it captures the essential features of most feedback control systems.

(from S.P.Bhattacharyya, H. Chapellat, L.H.Keel. Robust Control. The Parametric Approach)

14. Give derivatives of the following words from Text 5 and translate them into Russian:

 

Instability, performance, uncontrollably, excessive, acceptable, excessive, linear, invariant, simplification, validity, reliably.

 

15. Read Text 5 and try to give the Russian equivalents of the following terms. When necessary, look them up in a dictionary:

 

Stability, performance, external excitation, to decay to zero, open loop plant, to track the reference input, robust stability, to reject disturbances, nominal mathematical model, time invariant.

 

16. Supply synonyms for the following words:

problem, demand, limit, finally, task, to make smb/smth do smth, accurate, different, usual, that is why, suggested, to operate

 

17. Analyse the grammatical structure of the following sentences and translate them:

 

1. Absence of stability causes signals to grow without bound.

2. This is what happens when a satellite spins out of control

3. The job of feedback control is to stabilize the system

4. It makes the system track the reference input.

5. It causes the potential for instability to be everpresent and very real.

6. It is of fundamental importance that control systems be designed so that stability is preserved in the face of various classes of uncertainties.

7. The model is assumed to be linear and time invariant.

8. It is necessary to give the precise description of the external signals to be tracked or rejected.

 

18. Read and translate Text 5: