Ensuring kinetostatic consistency in observation of human manipulation

The aim of this paper is to present a method to guarantee the kinetostatic consistency in observation of human manipulation, i.e. the consistency between the observed hand posture and the tactile information on the contact between the fingertips and the objects. The core idea of the proposed algorithm is to compare the fingertip contact information, obtained by tactile sensors, with the contact information computed in a virtual environment, that reproduces the real environment where the observation is carried out. In case the estimation of the joint angles and the relative pose between the hand and the object are not consistent, a correction of the hand posture is computed. For some tasks, collisions might occur between parts of the hand (e.g. palm) and the grasped object. To handle this problem, the corrected hand posture is computed by adopting a closed loop inverse kinematic (CLIK) approach that exploits the redundant Degrees of Freedom (DoFs) of the hand. The algorithm has been designed to work on-line. This feature is particularly important for Programming by Demonstration (PbD) applications, since it allows the trainer to actively adapt the demonstration to measurement noise and model errors. The effectiveness of the proposed method has been tested in five different tasks: grasping a cup, unscrewing a bottle, grasping a plate, grasping a ketchup bottle, and grasping a measuring cup.

► New method to guarantee kinetostatic consistency in observation of human manipulation.
► Measurements from tactile sensors are adopted to check the kinetostatic consistency.
► The algorithm exploits a virtual environment reproducing the real one.
► In case of inconsistency, a correction is computed on-line based on inverse kinematics.
► The corrected hand posture is both kinetostatically consistent and collision-free.