Integrated vision/force robotic servoing in the task frame formalism

In this paper we show how to use the task frame to easily model, implement and execute three-dimensional (3D) robotic tasks, which integrate force control and visual servoing, in an uncalibrated workspace. In contrast to most hybrid vision/force research, this work uses eye-in-hand vision and,force control. Mounting both sensors on the same end-effector gives rise to new constraints, control issues and advantages. which are discussed in this paper. On the one hand, in this paper we emphasize shared control in which both vision and force simultaneously control a given task frame direction. Our work shows the usefulness and feasibility of a range of tasks which use shared control. Moreover, it offers a framework based on the task frame formalism (TFF) to distinguish between different basic forms of shared control. Each basic form is illustrated by a robotic task with shared control in only one direction. In addition, an extension to classify multi-dimensional shared control tasks is presented. On the other hand. a new classification is presented which distinguishes between four meaningful tool/camera configurations, being parallel or non-parallel endpoint closed-loop and fixed or variable endpoint open-loop. Corresponding control strategies are discussed, resulting in either collocated or non-collocated vision/force control. Several task examples (in 3D space), specified in the TFF illustrate the use of these four configurations. As shown by. the presented experimental results, the tasks at hand benefit from the integrated control approach.