Modeling the Coordinated Movements of the Head and Hand Using Differential Inverse Kinematics
K. Han Kim, R. Brent Gillespie and Bernard J. Martin
SAE 2004 Transactions, Journal of Aerospace, July 2005
Abstract—Hand reach movements for manual work, vehicle
operation, and manipulation of controls are planned and
guided by visual images actively captured through eye
and head movements. It is hypothesized that reach
movements are based on the coordination of multiple
subsystems that pursue the individual goals of visual
gaze and manual reach. In the present study, shared
control coordination was simulated in reach movements
modeled using differential inverse kinematics. An 8-DOF
model represented the torso-neck-head link (visual
subsystem), and a 9-DOF model represented the torso-upper
limb link (manual subsystem), respectively. Joint
angles were predicted in the velocity domain via a
pseudo-inverse Jacobian that weighted each link for its
contribution to the movement. A secondary objective
function was introduced to enable both subsystems to
achieve the corresponding movement goals in a
coordinated manner by manipulating redundant degrees
of freedom. Simulated motions were compared to motion
recordings from ten subjects performing right-hand
reaches in a seated posture. Joint angles were predicted
with and without the contribution of the coordination
function, and model accuracy was determined using the
RMS error and differences in end posture angles. The
results indicated that prediction accuracy was generally
better when the coordination function was included. This
improvement was more pronounced for low and
eccentric targets, as they required greater contribution of
the joints shared by both visual and manual subsystems.