Residual Vibration Characterization and Input Shaping for Collaborative Robots Under Single-joint Motion

Residual vibration in collaborative robots degrades positioning accuracy and increases settling time after motion. This study investigates residual vibration characteristics under varying single-joint operating conditions and evaluates the applicability of parameter-based input shaping. Residual vibrations were experimentally measured under six conditions: end-effector-to-base distance, end-effector mass, end-effector altitude, joint configuration, rotation direction, and motion duration. Using inertial measurement unit angular-velocity data, the natural frequency and damping ratio were estimated by curve fitting with a second-order damped-vibration model. The results show clear and repeatable trends under distance and mass conditions. In addition, the motion-duration condition shows an increasing tendency in natural frequency, but no consistent tendency is observed in damping ratio or in posture-related conditions, such as end-effector altitude, joint configuration, and rotation direction. ZV input shapers designed from the estimated parameters reduced the average settling time by 35.4% and 48.5% under the distance and mass conditions, respectively. When the input-shaping delay was excluded from the settling time, the reductions increased to 49.8% and 62.1%, respectively. These results confirm that experimentally identified vibration parameters can be effectively used for input-shaping-based vibration suppression in collaborative robots. The findings further suggest that residual vibration characteristics arise from complex interactions among operating conditions, motivating condition-dependent parameter identification and enabling the development of more robust input-shaping strategies for improved settling performance in collaborative robotic applications.