The Influence of Counterbalance System on the Dynamic Characterization of Heavy Industrial Robots

The precision of industrial robots is often limited by the relatively low stiffness of their joints, leading to positioning errors influenced by factors such as the mass and inertia of robotic links, external forces, and the counterbalance system (CBS). Counterbalance systems, typically consisting of hydropneumatic cylinders, are designed to reduce motor torque and assist in supporting heavier links. Traditionally, positioning errors in industrial robots have been corrected statically by determining pose-dependent stiffness values. However, recent numerical models incorporate inertial effects to improve positioning error correction, making accurate inertial parameter identification essential. These parameters are typically unknown and must be determined experimentally. While methodologies for inertial parameter estimation have been extensively studied, none have accounted for the effect of the counterbalance system in this process. To address this gap, a methodology for estimating inertial parameters was applied to a heavy industrial robot, considering the influence of the counterbalance system. A comparative analysis with and without the counterbalance system showed that its inclusion improved joint torque calculation accuracy, showing the necessity of considering it in dynamic parameter characterization methodologies.