Mathematical Modeling with Friction of a SCARA Robot Driven by Pneumatic Semi-rotary Actuators

Abstract

This article approaches the problem of the modeling of a SCARA manipulator designed by two semi-rotating pneumatic servo-actuators in the presence of friction in view of the precise control for a future application of a non-linear controller. Even though pneumatic systems are widely used in industry, it is found that the robustness of pneumatic servo-positioning solutions is limited by the positioning accuracy of the system controllers, that is, these controllers require complete knowledge of the system because they depend on sophisticated algorithms which should contemplate the highly non-linear nature of the operation of the pneumatic system. The present study is the continuation of a modeling performed for an isolated semi-rotary pneumatic actuator, in which the dynamics of the pressures in the chamber of this semi-rotary pneumatic actuator was realized, the experimental identification of the curves of mass flow and tension of control of the servo valve and the friction was determined through the LuGre model. Therefore, the present article uses the modeling of the same semi-rotary pneumatic actuator to consolidate a mathematical model of a SCARA manipulator consisting of two semi-rotary pneumatic actuators and a linear pneumatic actuator that will support the future development of a non-linear controller. Open loop validation was performed through comparisons between experimental and simulation results.