Efficient locomotion depends on the distribution of the weight and the
muscle strength in an animal's body. For example, fish with heavy
heads or tails will swim less efficiently and less gracefully than
fish with relatively light heads and tails, while fish with either too
weak or too stiff muscles will also suffer some degree of motor
incompetence. The weight and the muscle strength distributions of the
physics-based artificial fish are characterized by the 
and the
of the model, respectively. We set these physical parameters
of the model such that the corresponding distributions along the fish
body are biologically plausible. For example, the nodes that form the
head and the tail of the fish have less mass than those that form the
middle part of the body.
The values of parameters used in our simulation are listed in Table
and Table .
| Node i | Attributes |
i=0,  |  |
 ,  |  |
 |  |
| i=21, 22 |  |
[The mass distribution of the artificial fish.]
The mass distribution of the artificial fish. Refer to
Fig. .
Viscoelastic unit  | Attributes |
Cross units, e.g.  |  |
Muscle units:  |  |
Remaining units, e.g.  |  |
| All units |  |
[The elasticity and viscosity constants of the artificial
fish.] The elasticity and viscosity constants of the artificial
fish. Refer to Fig. .
Note that the elasticity constants are made large enough to provide
the fish's body with the structural integrity that it requires for
effective swimming.
However, this results
in a rather stiff dynamic system that needs a stable numerical solver
to simulate its dynamics.
| Xiaoyuan Tu | January 1996 |