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402 Biomimetics: Biologically Inspired Technologies

engineering, will lead to a deeper understanding of ourselves and will be significant for constructing
the next generation of advanced artificial systems such as human friendly robots.
The following sections of this chapter will introduce the recent biomimetic system control
researches. From the point of view of the system’s self-organization, we will describe in Section
16.2 the nonlinear and redundant sensory-motor learning problem. We will introduce the problem
of optimal motion formation under environmental constrains in Section 16.3. In Section 16.4, we
will study the system’s mechanical interaction and environmental adaptation, and show a novel
biologically inspired two degree of freedom adaptive control theory with its application to a robot’s
force tracking control. The conclusion will be given in Section 16.5.

16.2 SENSORY-MOTOR ORGANIZATION

Animals survive in complex natural environment using their sensory-motor behavior. The organ-
ization and development of brain nervous system’s motor control functions largely depend on the
physical interaction with the external environment. Self-organization of the environmental adaptive
motor function is one of the most interesting characteristics that we should learn in biomimetic
control research.
Charles T. Snowdon, who was a President of the Animal Behavior Society, described animal’s
behavior as follows: ‘‘Animal behavior is the bridge between the molecular and physiological
aspects of biology and the ecological. Behavior is the link between organisms and environment, and
between the nervous system and the ecosystem. Behavior is one of the most important properties
of animal life. Behavior plays a critical role in biological adaptations. Behavior is how we humans
define our own lives. Behavior is that part of an organism by which it interacts with its environment.
Behavior is as much a part of an organisms as its coat, wings, etc. The beauty of an animal includes
its behavioral attributes’’ (Snowdon).
Historically, there are two broad approaches to studying animal behaviors: (1) ethological
approach and (2) experimental physiological approach (http://salmon.psy.plym.ac.uk/). Ethologists
mainly concern with the problems of how to identify and describe species-specific behaviors.
They try to understand the evolutionary pathway through which the genetic basis for the
behavior came about. They use field experiments and make observations of animal behavior
under natural conditions. On the other hand, behaviorists and comparative psychologists concen-
trate on how we learn new behaviors by using statistical methods and carefully controlled
experimental variables for a restricted number of species, principally rats and pigeons, under
laboratory conditions.
The famous Russian physiologist Pavlov, who is recognized as the founder of behaviorism,
trained a dog by ringing a bell before mealtime. Through the course of time, he discovered that
simply by ringing the bell, the dog would salivate. It is now known as the concept of conditioned
reflex (Pavlov, 1923). A similar conceptual approach was also developed by him to study human
behavior. Sherrington, on the other hand, studied spinal reflexes and gave out his theory of the
reciprocal innervation of agonist and antagonist skeletal muscle innervation, which is known as
Sherrington’s Law (Sherrington, 1906). Bernstein, another Russian scientist, further pointed out
different important problems in motor learning and organization. Dealing with the redundancy
problem in motor behavior, he proposed the concept of synergy in muscles’ coordinative actions so
as to constraint the motion D.O.F. with respect to the required tasks. He suggested that it is such a
synergy that results in the reflex motions between each D.O.F. Moreover, this synergy changes with
respect to the environmental variations, which is beyond the philosophy of Pavlov’s conditioned
reflex (Bernstein, 1967).
Today, with the development of information science, robotics, and control engineering, it
becomes easier to study the motor behaviors and the principal control mechanisms of the brain
nervous system more quantitatively and systematically.