Biomedical Engineering Reference
In-Depth Information
is the diversity and complexity of human physiology. Unlike the usual engineering systems,
the behavior of which can be more or less predicted, each human being is unique and ever
changing. This is not a topic on human physiology, but to give the reader some essential
background its various aspects are considered in more detail in later sections of this topic
when a specific type of biomechatronic system is introduced.
1.2.2 Stimulus or Actuation
The process of stimulation can be introduced as a feedback element, as shown in
Figure 1-2, or as a naturally occurring input. Sources of stimuli can encompass any
modality that has an effect on the human element. This can include electrical stimuli,
an audio tone, control of air or blood flow, a source of light, a tactile stimulus, or even
the physical actuation of a limb. This topic includes an entire chapter on actuators, their
implementation and analysis in general terms, and their consideration as part of a number
of individual biomechatronic systems.
1.2.3 Transducers and Sensors
Transducers and sensors are the devices that convert physiological outputs into signals
that can be used. In most cases, these are sensors that amplify electrical signals or convert
them from chemical concentration, temperature, pressure, or flow into electrical signals
that can be further processed. Interfacing to the human body is not a trivial task, as
embedded sensors must be biocompatible, flexible, and extremely robust to survive in the
aggressive internal environment, while surface sensors, particularly electrodes, must be
able to form a compatible and relatively stable conductive interface across the skin. As
with actuators, sensors and sensing of physiological processes are sufficiently important
to devote a full chapter to the physical mechanisms that underpin their operation.
1.2.4 Signal Processing Elements
Signal processing involves modification of the electrical signal to some form that is more
useful. This generally involves amplification and filtering to extract salient features. How-
ever, it often involves the conversion of the analog signal to a digital equivalent that allows
for the application of complex algorithms to obtain subtler characteristics. This topic in-
cludes a chapter that concentrates on the classical aspects of signal processing, before
introducing the reader to modern machine learning algorithms. The latter are becoming
essential tools in the quest to better understand complex physiological processes.
1.2.5 Recording and Display
In many cases, the biomechatronic device functions to monitor a physiological process or
response. In these cases it may be important to display the information in a form that is easy
to interpret, or to store it for later analysis. Common examples of such devices are the now
ubiquitous 12-lead electrocardiograph, pneumotachographs and sphygmomanometers. In
the past many of these devices were mechanical and outputs were recorded onto paper tape
or photographic film, but with the advent of modern electronics, most have been replaced by
their electronic equivalents—random access memory (RAM) and liquid crystal displays.
