The Influence of Structural Dynamics on Cascaded Joint Position Control of a Flexible Beam with a Compliant Gear

摘要

The structural dynamics of a robot manipulator can have a large influence on its overall dynamic behavior. They can cause unwanted resonances, limit the control bandwidth and lead to instability. For this reason, a significant amount of research has focused on the development of advanced control methods which consider the structural dynamics of a robot. These techniques are, however, still rarely employed in practice due to their complex nature and reliance on accurate models. A popular decentralized control scheme for robot joints is cascaded position, velocity and current control of the motor. The goal of this paper is to visualize the influence of the structural dynamics of a flexible beam and flexible harmonic drive gear on this type of joint controller. The derived effects are explained by mainly relying on simulated and measured transfer functions, without the use of the typical equations. The difference between closing the control loop with position feedback from the motor side or on the joint side after the flexible gear is also investigated. The results are first generated using a flexible multibody simulation and later verified on a robot joint test rig.