a. To avoid joint limits within the Prioritized Inverse Kinematics (PIK) framework a mechanism called clamping has been exploited which strictly guarantees joint limit avoidance by adding dynamic constraints with the highest priority level. Such a strict enforcement may lead to undesired discontinuity in the postural control. In addition we have observed that this technique may also converge to non-optimal final states in singular contexts. For these reason we introduce the concept of progressive clamping which smoothly enforces a damping towards the joint limits and searches for an optimal task achievement within the remaining joint variation sub-space so that the proposed method helps to avoid the solution to converge to non-optimal final-states in singular contexts. The video is divided into three parts. The first part presents the interactive control of a kinematic chain with progressive clamping integrated in our Prioritized Inverse Kinematics (PIK) solver. The strength of the red color indicates the value of the damping force which is within [0,1]. Green means that there is no damping acting on the corresponding joint. Full red indicates that a joint has reached its limit (value of the damping force is equal to 1). Between [0, 1] for the damping force we do a simple color interpolation between green and red. The next experiment compares the behavior of clamping and progressive clamping on two kinematic chains. A red colored joint of the clamped chain means that the corresponding has passed or reached its limits and is know clamped back on the limits. For the progressive clamped chain we do exactly the same as before: we interpolate the color between green and red of the joints according to the damping force. The last part compares two virtual mannequins. They have to achieve a balanced posture requiring a high suppleness. Although both approaches will reach similar final postures the convergence of the progressive clamping approach is faster due to its kinematic singularity avoidance.
b. QuickTime Player, QuickTime 7.1.3
c. daniel.raunhardt@epfl.ch, ronan.boulic@epfl.ch, http://vrlab.epfl.ch





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