Page 41 - Modern Control Systems

Section 1.3 Examples of Control Systems 15
There has been considerable interest recently in applying the feedback control
concepts to automatic warehousing and inventory control. Furthermore, automatic
control of agricultural systems (farms) is receiving increased interest. Automatically
controlled silos and tractors have been developed and tested. Automatic control of
wind turbine generators, solar heating and cooling, and automobile engine perfor-
mance are important modern examples [20,21].
Also, there have been many applications of control system theory to biomedical
experimentation, diagnosis, prosthetics, and biological control systems [22, 23, 48].
The control systems under consideration range from the cellular level to the central
nervous system and include temperature regulation and neurological, respiratory,
and cardiovascular control. Most physiological control systems are closed-loop sys-
tems. However, we find not one controller but rather control loop within control
loop, forming a hierarchy of systems. The modeling of the structure of biological
processes confronts the analyst with a high-order model and a complex structure.
Prosthetic devices that aid the 46 million handicapped individuals in the United
States are designed to provide automatically controlled aids to the disabled [22,27,39].
The robotic hand shown in Figure 1.14 belongs to Obrero, a humanoid robot devel-
oped at MIT that is capable of sensitive manipulation. The Obrero robot is respon-
sive to the properties of the object it holds and does not rely on vision as the main
sensor. The hand has position and force control of the fingers employing very sensi-
tive tactile sensors and series elastic actuators in its joints.
Finally, it has become interesting and valuable to attempt to model the feedback
processes prevalent in the social, economic, and political spheres. This approach is
undeveloped at present but appears to have a reasonable future. Society, of course,
is composed of many feedback systems and regulatory bodies, such as the Federal
Reserve Board, which are controllers exerting the forces on society necessary to main-
tain a desired output. A simple lumped model of the national income feedback con-
trol system is shown in Figure 1.15. This type of model helps the analyst to understand
the effects of government control—granted its existence—and the dynamic effects of

(a) Computer-aided drawing (Courtesy of Eduaido Torres-Jara). (b) The Obrero robotic hand (Photo by Iuliu Vasilescu).

FIGURE 1.14 The Obrero robot is responsive to the properties of the object it holds and does not
rely on vision as the main sensor but as a complement. Obrero is part of the Humanoid Robotics
Group at the MIT Computer Science and Artificial Intelligence Laboratory.