Page 42 - Modern Control Systems

Chapter 1 Introduction to Control Systems

Private business
investment

Desired + Business National
national K^_/" Government production
income Government
spending
Consumer
spending
Measurement Consumers

FIGURE 1.15 Tax
A feedback control collections
system model of
the national income.

government spending. Of course, many other loops not shown also exist, since, theo-
retically, government spending cannot exceed the tax collected without generating a
deficit, which is itself a control loop containing the Internal Revenue Service and the
Congress. In a socialist country, the loop due to consumers is de-emphasized and gov-
ernment control is emphasized. In that case, the measurement block must be accu-
rate and must respond rapidly; both are very difficult characteristics to realize from
a bureaucratic system. This type of political or social feedback model, while usually
nonrigorous, does impart information and understanding.
The ongoing area of research and development of unmanned aerial vehicles
(UAVs) is full of potential for the application of control systems. An example of a
UAV is shown in Figure 1.16. UAVs are unmanned but are usually controlled by
ground operators. Typically they do not operate autonomously and their inability to
provide the level of safety of a manned plane keeps them from flying freely in the
commercial airspace. One significant challenge is to develop control systems that
will avoid in-air collisions. Ultimately, the goal is to employ the UAV autonomously
in such applications as aerial photography to assist in disaster mitigation, survey

FIGURE 1.16
An unmanned aerial
vehicle. (Used with
permission. Credit:
DARPA.)