Page 180 - Designing Sociable Robots

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Facial Animation and Expression 161

Facial Functions: each subsystem makes a prioritized request of the face motor primitives
Face left left right right left left right right right left jaw top top lower lower
ear ear ear ear brow brow brow brow eye eye lid left right left right
System arc lift arc
lift rotate lift rotate lift lid lip lip lip lip
facial x x x x x x x x x x x x x x x
expression
priority
facial q q q q v v v v v v u u u u u
display
priority
lip sync y y y y z z z z z z w w w w w
priority

Motor Server: process request for motor primitives; arbitrate based on prioritized scheme
x x x x x v v v v v w w w w w

Motor Primitives: convert position and velocity requests of ears, brows, lids, jaw & lips to underlying actuator command
pos, pos, pos, pos, pos, pos, pos, pos, pos, pos, pos, pos, pos, pos, pos,
vel vel vel vel vel vel vel vel vel vel vel vel vel vel vel

left left right right left left right right top top lower lower
ear ear ear ear brow brow brow brow left right jaw left right left right
lid
lid
D2 D1 D1 D2 lift arc lift arc lip lip lip lip
Actuators
Figure 10.2
Face arbitration is handled through a dynamic priority scheme. In the figure, q, u,v,w, x, y, z are hand-coded
priorities. These are updated whenever a new request is made to a face motor subsystem. The actuators belonging
to each type of facial feature are given the same priority so that they serve the same function. At the motor server
level, the largest priorities get control of those motors. In this example, the ears shall serve the expression function,
the eyebrows shall serve the display function, and the lips shall serve the lip synchronization function.

The facial emphasis component of lip synchronization modulates the facial features about
the established baseline. In this way, the rest of the face blends with the underlying facial
expression. This is critical for having face, voice, and body all convey a similar emotional
state.
The Facial Function Layer

The highest level of the face control hierarchy consists of three subsystems: emotive facial
expression, communicative facial display and behavior, and lip synchronization and facial