Motor Controllers

 

We have described the structure, mechanics, hydrodynamics and the numerical simulation of the physics-based fish model. In this section, we proceed to describe how we implement the repertoire of biomechanics-based motor skills of the artificial fish.

A critical first step towards higher level, behavioral modeling is to abstract, as a set of motor controllers, the detailed muscle actions, and pectoral fin motions required for locomotion. These motor controllers serve as the behavioral building blocks. They are implemented as parameterized procedures, hence allowing the easy expression of behaviors. In particular, behaviors, as elaborate as the mating behavior, emerge from the invocation of a sequence of motor controllers with appropriate parameters in a meaningful order.

Currently the repertoire of motor skills of the artificial fish is implemented by nine motor controllers:

1. swim-MC
2. left-turn-MC
3. right-turn-MC
4. glide-MC
5. ascend-MC
6. descend-MC
7. balance-MC
8. brake-MC
9. balance-MC

Each motor controller carries out a specific motor function. Four of the motor controllers prescribe the muscle contractions of the biomechanical fish model: swim-MC produces forward caudal locomotion, left-turn-MC and right-turn-MC execute turns, while glide-MC allows gliding and smooth transitions from forward swimming to turning and vise versa. The other five motor controllers control the fish's pectoral fins that enable it to navigate freely in its 3D virtual world: ascend-MC produces lift, descend-MC controls diving, balance-MC enables the fish to maintain its balance, brake-MC slows the forward velocity, and backward-MC allows the fish to retreat.

In the following sections, we explain the implementation of the muscle motor controllers followed by the pectoral fin motor controllers.

Xiaoyuan Tu

January 1996