Design of a robot end effector with measurement system for precise pick- and-place of square objects

摘要

Future manufacturing requires increasing participation of the robots for pick-and-place task. One of the main error sources that reduce the final accuracy of the task is the pose deviation between the end effector (EF) of the robot and its manipulated target object (TO). In this paper, to improve the accuracy, an end effector and its affiliated measurement system, which can measure the relative pose deviation between the TO and the EF, was designed for the precise pick-and-place of the square TOs. In the design, an additional measurement frame ("Frame" for short) with CCD laser displacement sensors was established as a media to transform the pose of the TO to the expression in the coordinate system (CS) of the EF by both describing the pose of the EF and of the TO in the Frame's CS separately. The geometric model of the entire design, in which the pose deviation of the TO was expressed as a function of the readings of the 16 CCD displacement sensors, was also established. To verify the effectiveness of the design and of the accuracy of the geometric model, an experiment was performed on an ABB irb4600 robot to compensate the error between the EF and its grasped TO in a pick-and-place task. Results show that the average errors can be reduced by around 85%.