Research and development of milking robot system for stanchion barns - (Part 2): control system for tracking teat movement and manipulability of robot manipulator

摘要

This paper deals with designing a positional feedback controller for a manipulator with 3 rotational joints on a X-Y plane that follows the teat movement. The frequency response of 1st, 2nd, and 3rd joint of the manipulator indicated that the natural frequency of the axes were 3.5Hz, 4.5Hz and 4.5 Hz, respectively. Although the gain rate was set to five to stabilize the control system, it can fully follow the motions up to 0.7-0.9 Hz. Positional commands are sent to the servo drivers at intervals 20 ms via the positioning pulse distributor so that the deviation is less than the set value. We assume the manipulator, based on of the frequency of teat motion obtained from our preliminary study, will not encounter teat movement during practical use. The manipulator with a 3-D.O.F. is essentially the same as one with a 2-D.O.F., but with a restricted manipulator range in the 3rd joint when parallel to the cow's body axis. This allows the inverse kinematics of the 3-D.O.F. system to be expressed more simply. Furthermore, we showed that the manipulator worked most efficiently when the manipulator's manipulability measure was over 80% in the operational space. This means that the manipulator will know the contours and movements of the cow's body so that it can quickly and easily attach teat-cups to the udder.