Dynamic model and integrated optimal controller of hybrid arms robot for laser contour machining

Abstract

The hybrid arms robot (HAR) is a new modified robot which consists of a rigid link (RL) and a flexible link (FL), and it carries a laser head at the end-effector for laser contour machining (CM). The HAR is inspired from a rigid-flexible links manipulator (RFLM) and the aim is to bring the advantages of flexible link manipulators (FLMs) to industrial robots. The HAR gains the advantages of lightweight robots and FLMs such as fast response, less power consumption due to using small actuators, low cost, and safe to surrounding operators. However, the HAR has the drawback of a tip vibration caused by the flexibility of the second FL and leads to a position error at the end-effector position. Furthermore, the HAR has more parameters to be incorporated in a dynamic model such as the tip vibration, the laser head weight, and a force generated by the assist gas pressure. This research aims to obtain the dynamic model of the HAR using the finite element method (FEM) in conjunction with the Lagrangian equation and to propose an integrated optimal controller (IOC) which is an integration of a linear quadratic regulator (LQR) and a fuzzy logic controller (FLC). The derived dynamic model of the HAR is efficient due to the close match response with the SimMechanics model response of the HAR. The proposed IOC is tested for point-to-point (PTP) position control of the HAR and demonstrates improved response and better capability for the tip vibration suppression. The proposed IOC also reveals enhanced triangular CM trajectory, rhombic CM trajectory, and circular CM trajectory of the HAR laser head compared to the LQR performance in a proper cutting speed to ensure the machining quality.