Concluding Remarks - Human Motion Simulation: Predictive Dynamics - page 236

These surfaces were then modeled using various strategies for implementation
into the code. It was shown that the PD optimization-based formulation uses these
torque surfaces as constraints in guiding the human model to accomplish a task.
The ideas of modeling by using joints, limiting their strengths, and numerically
optimizing them to drive natural motion fits together well and provides for a com-
plete methodology.
10.1.8 The PD validation process is effective
A cornerstone of any simulation formulation is its ability to be validated and veri-
fied. It has been shown that validation can be accomplished on all PD tasks, albeit
with varying levels of accuracy, using a number of methods. The keys to the vali-
dation strategy are the determinants of motion that were defined earlier. We do
believe, however, that technologies for motion capture and analysis will continue
to evolve very rapidly and that more effective validation methods can be
employed. Nevertheless, validation is only successful when the validation data
feed back into the model and improve its fidelity. Predictive dynamics allows for
both validation and feedback into the model.
10.2 Applications
There are many applications for the use of digital human models in general, spe-
cifically the use of PD as a method for predicting human motion and understand-
ing cause and effect.
10.2.1 Ergonomics
Consider an operator in a manufacturing plant who has to maneuver a large and
heavy object into a machine. Similarly, consider another operator who works on
an assembly line inserting a fitting with a certain force into the machine's assem-
bly. Both operators will most likely acquire musculoskeletal injuries after some
time. These injuries are typically not due to static loads but rather to dynamic
loads and repetitive tasks. Predictive dynamics has provided a systemic method
for simulating and analyzing these tasks before the task is designed to assess its
feasibility.
10.2.2 Simulating an injury or a disability
Changing lower or upper joint limit constraints in conjunction with strength con-
straints at a single joint can simulate a disability and will cause the model to
respond differently.
Exoskeletons and wearable devices to enhance human power or simply to aid
in a disability are expected to make a significant impact on our society. Whether