A Mechatronic Design for Robotic Deburring

摘要

This paper deals with the implementation of a mechatronic methodology for the robotic deburring of planar workpieces with an unknown shape performed by an industrial manipulator. The approach is based on the use of a hybrid force/velocity control law and on a correlated suitable design of the adopted deburring tool. Experimental results, obtained with a two degrees-of-freedom SCARA industrial robot manipulator, show the effectiveness of the method. I. INTRODUCTION Robots that are able to autonomously adapt themselves to semi-unstructured tasks are nowadays a key issue in several industrial applications, such as grinding, debur- ring, chamfering and polishing, where the capability to cope with a workpiece of an unknown shape would significantly reduce the task programming phase, espe- cially when frequent changes in the production occur. Various methods to perform effectively a deburring task have been proposed in the literature. They are based for example on impedance control (1), on hybrid control with an internal position loop (2) (note that in this case the geometry of the workpiece is known), and on the so-called triangular control (3). Soft-computing techniques can be also adopted (see e.g. (4), (5)). The idea to design the deburring tool in conjunction with the control algorithm has been pursued in (6), (7). In particular, in (6), under the framework of impedance control, a roller bearing mounted on the force sensor is employed for the purpose of tracking. In this case however two force sensors are needed. Differently, in (7) an end-effector mounted jig and a proper design of the compliance of the manipulator are used to achieve accurate force guidance. An admittance control law is proposed but no results are given to prove the effectiveness of the method. In any case, when dealing with an unknown object, the robot has to perform a con- tour tracking task effectively, by imposing an appropriate normal force and an appropriate tangential velocity to the robot end-effector. In this context, the use of hybrid force/velocity control (8) is addressed in this paper. It will be shown that it can be effectively adopted for this task in conjunction with a suitable design of the milling tool. Indeed, by suitably adopting the measured torque along the vertical axis, it is possible to detect the contact angle in order to achieve an accurate tracking (9). Further the presence of burrs can be detected and consequently the reference tangential velocity can be suitably modified to improve the quality of the deburring.