Gain tuning technique of a 6-axis articulated manipulator using notch filter-based LabVIEW® programming

Unlike Cartesian Robot and SCARA (Selective Compliance Assembly Robot Arm) which have wide application in assembling electronic parts, the dynamic performance of a 6-axis articulated industrial robot is greatly changed according to the position and orientation of the robot. Usually PID (Proportional-Integral-Derivative) gain tuning of the robot´s servo controllers should be tuned considering the dynamic characteristics of robot mechanism. But the gain tuning cannot inherently prevent “residual vibration” caused by the (inevitable) flexibility (or elasticity) of robot link. In this paper, for accurate gain tuning of RS2 with less noise, a program routine of DSA (Dynamic Signal Analyzer) for frequency response method will be programmed using LabVIEW^®. Then robot transfer functions can be obtained experimentally using frequency response method with DSA program. Data resulted from the robot transfer functions are transformed into Bode plots, based on which an optimal gain tuning will be executed. Of course, gain tuning can enhance the response quality of output signal for a given input signal during the real-time control of robot. But the gain tuning cannot inherently prevent “residual vibration”. To cope with this problem of gain tuning, we will incorporate notch filter tuning into our proposed experimental gain tuning using LabVIEW^®. This will be confirmed by comparing with the velocity response of gain tuning with without notch filter tuning. Basically the research performed in this paper is a preliminary step for the gain scheduling in which the parameters related to notch filter tuning should be changed for various robot motion.