HIGHSPEED DELTA ROBOT SORTING SYSTEM WITH INTEGRATED  COMPUTER VISION: DESIGN AND EXPERIMENTAL STUDY

Nguyễn Thị Vân; Đào Bình Dương; Đỗ Thành Hiếu

Nguyễn Thị Vân Trường cao đẳng cơ giới xây dựng
Đào Bình Dương Công ty trách nhiệm hữu hạn Z–TEC Việt Nam
Đỗ Thành Hiếu Trường Đại học Sư phạm Kỹ thuật Hưng Yên

Keywords: Delta robot, Computer vision, S71200 PLC, HSV color space, Affine transformation, Handshaking communication

Abstract

The paper presents the design and implementation of a Delta robot system integrated with computer vision for color-based sorting of multi-colored products on a moving conveyor. To optimize cost and enhance localization, the study embeds the 3-DOF translational inverse kinematics algorithm directly into a standard S7-1200 PLC controller instead of using expensive dedicated motion controllers. The computer vision system is developed in Python and utilizes the HSV color space for real-time object recognition, environmental noise suppression, and object centroid detection. To eliminate geometric discrepancies between the camera and the mechanical coordinate system, an automatic calibration algorithm based
on a 2D affine transformation matrix combined with a second-order polynomial interpolation function is implemented, effectively compensating for conveyor tilt and Z-axis height errors with an average error of ±0.45 mm. Communication between the image-processing computer and the PLC is optimized via a handshaking mechanism over TCP/IP (Snap7 library), achieving a communication delay of only 4.2 ms and a total closed-loop response time of 38.5 ms. Experimental results demonstrate that the system operates stably with a PLC scan cycle from 1.8 ms to 2.2 ms, accurately tracking workpieces at a maximum conveyor speed of 350 mm/s, and achieving an actual sorting throughput of 60 products per minute.

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