Coordinate Measuring Robotic Arm

Abstract

This thesis presents the design, development, and experimental validation of a coordinate measuring arm intended for educational and small-scale engineering applications. Conventional coordinate measuring machines (CMMs) are expensive and unsuitable for resource-limited environments; therefore, this work proposes an accessible alternative based on three-joint articulated arm mechanics, absolute rotary encoders, and RS485 Modbus RTU communication. The mechanical structure was designed using Autodesk Inventor and fabricated through fused deposition modelling (FDM) 3D printing. A Python-based software application was developed to acquire encoder data, compute end-effector coordinates using planar forward kinematics, and reconstruct basic geometric shapes including lines, triangles, and circles. A graphical user interface provides real-time visualization of the arm configuration and measurement results. Calibration methods including offset correction and global scaling were implemented to reduce systematic errors. Experimental validation demonstrated that the system achieves line measurement accuracy within ±2%, circle measurement error below 3.3%, and reasonable geometric fidelity for triangular shapes. These results confirm the feasibility of developing functional coordinate measurement capability using low-cost, readily available components.