Force Control With Friction Compensation In A Pneumatic Gripper

Abstract

Robots can grasp, even manipulate, objects with different shape, weight and size thanks to the their end-effectors. These are mostly constituted by two fingers, and are known as grippers. However, despite being quite simple for human beings, manipulation is not so straightforward to carry out on robotic systems. One of the main obstacles is the lack of reliable control methods: this is especially true for pneumatic grippers. Such devices are often mounted on industrial robots, though their behavior does not go beyond basic fully-open or fully-closed operations. This happens also as a consequence of the incapability of taking into account frictional effects limiting the pneumatic gripper performance. In this article, a new control strategy is delivered to solve this issue. The proposed strategy allows controlling the grasping force of a pneumatic gripper, without performance degradation due to friction. A pneumatic gripper was built and instrumented with several sensors to experimentally validate the proposed control strategy. The gripper was mechanically connected to a robotic arm and tested with different desired force profiles upon a wide range of force.