Effect of a Self-Locking Drive Mechanism on the Performance of a Flexible Robot Arm

In addressing the control problem of flexible robot arms, the dynamics of drive mechanisms are often neglected. This leads to inaccurate prediction of the actual behavior of the robotic manipulator through digital simulations, and to a deterioration in the performance of the controller when applied to the physical system. The focus of this study is to demonstrate the effects induced by drive mechanisms. This is done by in incorporating the dynamics of a self-locking leadscrew drive mechanism into the dynamic model of a flexible, spherical robotic manipulator. The self-locking condition and Coulomb friction, inherent in this particular type of drive mechanism, are ignored in the design of the arm controller. The rationale is to isolate the impact of drive mechanisms on the performance of the arm controller. The theoretical and experimental results exhibit qualitatively similar behavior and demonstrate the deterioration in the response of the manipulator due to friction in the drive mechanisms. In addition, the effect of the self-locking condition on the coupling between the various degrees of freedom of the robotic manipulator is discussed.