Vibration analysis of SCARA type direct drive robot with double link mechanism.

摘要

This paper describes a vibration analysis of a SCARA type Direct Drive Robot (DDR). The arm natural frequency varies depending on the arm configuration, and the bandwidth of the servomechanism for the joint control is restricted by the lowest natural frequency to keep a stable control. Especially in the DDR with one set of parallelogram arm mechanism (single link), the change of the arm natural frequency is remarkably large. In this paper, a mathematical model of the arm mechanism is presented to estimate the arm natural frequency which varies depending on the arm configuration. By the analysis with the model, it is cleared that by using two sets of parallelogram arm mechanism (double link), the lowest natural frequency becomes large and also the change of the natural frequency by the arm configuration can be decreased. It is also shown that there exists an optimum design parameter in which the arm natural frequency becomes almost independent of the change of the arm configuration. Moreover the optimum design parameter is obtained analytically. The analytical results are confirmed by experiments using a developed SCARA type DDR with the double link mechanism.