Distance Control for Pick-up Device System of Pilot Mining Robot

A self-propelled pilot mining robot was developed by KRISO (Korea Research Institute of Ships and Ocean Engineering) in 2012. The purpose of the pilot mining robot is to gather manganese nodules that spread on the seabed and to transfer them into buffer. The pilot mining robot consists of two independent unit modules where each unit module has two tracks, two pick-up devices, and one delivery pump. The manganese nodules are gathered by a pick-up device while the robot is driving. The pick-up device has to keep an appropriate distance from the seabed for efficient gathering. Then an actuator of the pick-up device is operated by hydraulic system. This paper discusses the distance control of the pick-up device. The distance control is implemented by a PI controller from gain tuning formulas based on the model identification. First, the input-output function of the hydraulic pick-up actuator is calculated. Second, the transfer function of the pick-up device is identified by a closed-loop response of a second order under-damped system. Next, PI gains are tuned by tuning formulas based on the identified system parameters. Finally, the tuned PI gains are compared, and one of them is selected as a distance controller.