Human-like behavior of robot arms: general considerations and the handwriting task—Part I: mathematical description of human-like motion: distributed positioning and virtual fatigue

This two-part paper is concerned with the analysis and achievement of human-like behavior by robot arms (manipulators). The analysis involves three issues: (i) the resolution of the inverse kinematics problem of redundant robots, (ii) the separation of the end-effector's motion into two components, i.e. the smooth (low accelerated) component and the fast (accelerated) component, and (iii) the fatigue of the motors (actuators) of the robot joints. In the absence of the fatigue, the human-like performance is achieved by using the partitioning of the robot joints into “smooth” and “accelerated” ones (called distributed positioning—DP). The actuator fatigue is represented by the so-called “virtual fatigue” (VF) concept. When fatigue starts, the human-like performance is achieved by engaging more the joints (motors) that are less fatigued, as does the human arm. Part I of the paper provides the theoretical issues of the above approach, while Part II applies it to the handwriting task and provides extensive simulation results that support the theoretical expectations.