Dynamic Characterization and Incremental Dynamics Calibration of the Heavy-Duty Industrial Robot: A Focus on Hydraulic Equilibrium Dynamics

Abstract In recent decades, industrial robots have emerged as pivotal contributors to the global manufacturing landscape, revolutionizing various sectors through increased automation and efficiency. Simultaneously, the application of heavy-duty robots in heavy industries is gradually increasing. In this study, a self-developed heavy-duty robot is utilized for automated fiber placement (AFP), with the layup equipment integrated at the robot's end effector, weighing over one ton. To ensure the precision and efficiency of AFP, particular attention is given to the dynamic performance of the robot. The heavy-duty robot is equipped with a hydraulic equilibrium system to alleviate the gravitational load on the joint motors of both the robot body and the end effector. The hydraulic equilibrium system consists of a bladder accumulator and a hydraulic cylinder, introducing complexity to the robot dynamics. Therefore, establishing a dynamic model of the robot system and obtaining accurate dynamic parameters serve as the foundation for precise control of the robot, enabling the full utilization of its dynamic capabilities. In this paper, dynamics modeling of the hydraulic equilibrium system is performed based on the Maxwell model, and its dynamic parameters are identified using the CARAM model. Subsequently, the multi-body dynamic model of the robot is established, and an incremental identification algorithm for dynamic parameters is devised based on the characteristics of the robot structure. Additionally, to accurately identify dynamic parameters, an analysis of the robot drive mechanism is conducted to obtain the equivalent reduction ratio of the joints and the lever arm of the hydraulic equilibrium system. Furthermore, an equivalent friction model for the robot joints and screws is established.