Analysis of Oscillations in Nonlinear Human-Operated Robotic System

The development of automation is characterized by the increasing complexity of control tasks associated with various technical objects. However, this does not exclude the human element from the control process. Manual control has certain drawbacks that negatively impact the quality of management, primarily arising from the interaction between the operator and the nonlinear dynamics of the robot. This study examines a manual control system for a robotic manipulator, taking into account nonlinear constraints that may manifest as limitations on the power of the actuating mechanism or as part of a local regulator. The parameters of the operator's control actions exhibit a certain range due to individual characteristics of the human operator or the control technique employed. Additionally, signal transmission delays may be present in the control loop. Considering these system characteristics provides a more comprehensive understanding of control quality and allows for the establishment of acceptable control techniques for the human operator. Depending on the frequency of input disturbances, this work analyzes the closed-loop system comprising the operator and manipulator using methods based on harmonic linearization of nonlinearity and harmonic balance equations: locus of a perturbed relay system and harmonic stabilization. The results of calculations and simulations using these methods indicate that there exists a parameter space within which oscillations may arise. Thus, when designing manual control systems for robotic manipulators, it is essential to pay attention to the control techniques employed by the human operator and to overall delays in order to avoid undesirable operational modes of the system.