Development of a 6-axis robotic arm controller implemented on a low-cost microcontroller

Abstract

This paper presents a case study of development of a 6-axis robotic arm controller. The robot is powered by a hydraulic pump. The position of each axis can be derived from its potentiometer voltage. At each and every axis, a servo-valve is employed to control a servo motor. Its relative velocity is related to the servo-valve input. With 2 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">nd</sup> order PID controller, a micro-controller commands movements of all axes. The PID inputs are the six voltages from potentiometers and its outputs are the six DC voltages, which command the six servo-valves. A trajectory file is generated by solving the inverse kinematics problem with some (angular to digital value) conversions. A special case; closedform calculation is developed to solve kinematics problem. With some constraints it only yields one solution. Experiments show that robot follow the given trajectory with acceptable errors.