An Automated Grid-Based Robotic Alignment System for Pick and Place Applications

Abstract

This paper proposes an automated grid-based alignment system utilizing lasers and an array of light-detecting photodiodes. The intent is to create an inexpensive and scalable alignment system for pick-and-place of industrial objects (titer plates) using a SCARA robot manipulator. The system utilizes the robot trajectory, the transformation matrix, and geometric and trigonometric principles to determine the movements to align the robot with a grid-based array of photodiodes. The alignment system consists of a sending unit utilizing lasers, a receiving module consisting of photodiodes, a data acquisition unit, a computer-based control system, and the robot manipulator. The control system computes the robot movements needed to position the lasers based on laser positions detected by the photodiodes. With a spacing of 10mm between sensors, the system shows a resolution of 0.5mm along both the X and Y-axes, with a maximum single-point X-position detection error of 2.9mm and a maximum single-point Y-position detection error of 2.0mm. After the alignment, the maximum positional errors for both X and Y-position is 1.4mm. With a grid spacing of 10mm from center-to-center between each photodiode, the system still shows a high relative resolution. The results, along with system improvements, show potential for the system being a viable and relatively simple solution for 2D alignment.