Forcefree control with independent compensation for inertia friction and gravity of industrial articulated robot arm

Forcefree control can realize the flexible motion of industrial articulated robot arms without any change of the built-in controller. In this paper, the forcefree control was extended to realize flexible motion emulating operational circumstance free of inertia, friction and gravity through the independent compensation of inertia, friction and gravity. The property of the forcefree control with independent compensation was also investigated by experimental study of an actual industrial articulated robot arm, where the external force was measured with a force sensor which was attached to the tip of the robot arm.

I. INTRODUCTION

A lot of industrial robot arms are worked in industry. Some works of industrial robot arms, such as pulling-out of products made by die casting, require flexible motion according to external force. A number of methods for flexible motion realization of the robot arms such as impedance control[1], [2], [3] and compliance control [4], [5] are proposed. However, these methods are difficult to be used in industrial robot arms because of the complexity of algorithms and the necessity to change the built-in controller of the industrial robot arms. On the other hand. servo float method can realize the flexible motion of the industrial robot arms and it has already used in industry[6]. The servo float method, however, requires mode change of the controller for the realization of the flexible motion and the change is not convenient for applications.