Biomedical Engineering Reference
In-Depth Information
1.2.6 Feedback Elements
In a closed-loop control application, any stimulus or excitation signal is conditioned by
the processed outputs of one or a number of sensors monitoring the physiological process.
The link that connects the sensing output back to the stimulus includes further processing
through control elements. This feedback can be used to close an external loop or one that
operates through the human being. An example of the latter is a vibrotactile stimulus that is
triggered in response to some changes in the direction of the earth's magnetic field to help
a blind person navigate. The chapter on classical control investigates the use of feedback
elements in terms of their effect on loop performance.
1.3
PHYSIOLOGICAL SYSTEMS
To interact effectively with the human part of the structure shown in Figure 1-2, it is
essential to have some understanding of the subject on which the measurements are being
made or to which the stimulus is applied. The major functional systems of the body include
the cardiovascular, respiratory, and musculoskeletal systems along with those that interpret
of taste, sight, hearing, and touch. These are illustrated in Figure 1-3.
Most of the second half of this topic considers the application of biomechatronic
systems to these physiological components.
1.3.1 Biochemical System
The human body is controlled and powered by a complex system of chemical processes.
Biochemical processes convert the food we eat into amino acids that are used for building
and repair; they break down sugars and fats and store them for later use as sources of
energy. In addition, our blood and tissues are awash with hormones and other organic
molecules that control, signal, and regulate the amazingly interconnected functions that
keep the system alive and healthy. Later sections of this topic examine some of the sensors
and actuators that interact with these biochemical processes for monitoring and control
purposes.
FIGURE 1-3
Major physiological
components that
can be incorporated
into biomechatronic
systems. [Adapted
from Cromwell,
Weibell, et al.
(1973).]
