Page 32 - Handbook of Biomechatronics

Introduction 25

effect aim at optimization and manipulation of the total impedance inherent
in the system which is a consequence of devised functional connectedness.
Optimization of the system impedance is therefore the objective function
from which a set of generalized constraints can be abstracted. Optimization
of impedance could mean minimization of structures associated with
energy dissipation and inertial optimization could be addressed through
minimum connectedness. The connectedness optimization, on the other
hand, is directly pointing at minimum number of elements and optimum
configuration.
Following a minimalistic approach, the first design criterion could thus
be stated as: the energy consumption of a proposed system for performing a
given task must be optimized. Within the structure of such criterion, con-
cepts like energy density in a system, the effectiveness of the power sources,
or transforming modules may be investigated. In thermodynamic terms,
entropy generation must be minimized or unnecessary irreversibilities must
be eliminated. The attention could thus be directed at advanced modes of
decision-making using switching mechanism to avoid classical energy con-
sumption problems. The next stage is the identification of the modulating
elements through which the performance of the system is manipulated, reg-
ulated, and controlled.
Conventionally, the controllers are considered only after the nature
of functional connectivity has to a great degree been established. In a mul-
tidisciplinary approach to design, however, the controlling system is all
part of the complete functional connectivity and is developed simulta-
neously. The recognition of modulatory constituents at the outset of
design will contribute toward a minimalistic criterion function. Here
the root characteristics of the controlling mechanism is readily provided
by the bond graph model of the synthesized system. Engaging in control-
ler design during the synthesis of biomechatronic systems induces a har-
mony with dissipation minimization approach. The preliminary criterion
function can thus be based on flow of energy, materials, and signals. The
constraints imposed on the ICD could therefore be stated as minimum
energy consumption, minimum functional connectivity, and minimum
restriction to energy flow.
The designer, however, must leave the sphere of conceptuality and
advance toward physical realization. The results of the synthesis and the
natural expansion of the initial model will lead to physically realizable sys-
tems as bond graph technology is inherently adept in catering for physical
realization. Once disciplinary elements are substituted for ICD constituents