Kinematic Analysis of a Two-Link Object for Whole Arm Manipulation

This paper presents kinematic analysis of free-ended two-rigid-links object manipulated by two arms as an initial step simplification towards the analysis of holding and manipulating a human body by a humanoid robot. Rolling as well as sliding at the points of contact of the two-links object constrained by the holding two-arms is explained. Position, velocity and acceleration analysis of the manipulated object, position, velocity and acceleration constraints as well as expressions for sliding displacement, sliding velocity and sliding acceleration are presented. Simulation results for links sliding acceleration, the object joint acceleration and object configurations for different input rolling accelerations are presented. The presented position, velocity and acceleration analysis proves that: 1- through manipulating two-links object by two-arms, rolling about one arm or both arms at the points of contact is associated with sliding at both points of contact. There is no rolling without sliding and there is no sliding without rolling. 2- It is possible to define the object links velocities or accelerations as well as sliding accelerations from the contact rolling velocities and accelerations estimations or measurements. 3- It is possible to define the configuration of the object from contact points and hence contact angle measurements, applying tactile sensors.