Vision-Based Assisted Tele-Operation of a Dual-Arm Hydraulically Actuated Robot for Pipe Cutting and Grasping in Nuclear Environments

Abstract

This article investigates visual servoing for a hydraulically actuated dual-arm robot, in which the user selects the object of interest from an on-screen image, whilst the computer control system implements via feedback control the required position and orientation of the manipulators.To improve on the current joystick direct tele-operation commonly used as standard in the nuclear industry, which is slow and requires extensive operator training, the proposed assisted tele-operation makes use of a single camera mounted on the robot. Focusing on pipe cutting as an example, the new system ensures that one manipulator automatically grasps the user-selected pipe, and appropriately positions the second for a cutting operation. Initial laboratory testing (using a plastic pipe) shows the efficacy of the approach for positioning the manipulators, and suggests that for both experienced and inexperienced users, the task is completed significantly faster than via tele-operation.

Control of hydraulically–actuated manipulators with dead–band and time–delay uncertainties*

“…The laboratory demonstrator used in this article consists of two HYDROLEK HLK-7W manipulators, each a 6-degreesof-freedom articulated arm, with a seventh actuator for the gripper. Whilst the original set-up is described by reference [6], a ball valve, pressure gauge and new pressure pump were added in 2019. Fig.…”

“…A monitor, mouse and keyboard are externally connected such that an operator can control or program the robot from outside the safety cell (to some degree, representing the situation on a nuclear site where the robot will be remote from the operator). Since the present article focuses on the low-level joint control problem, inverse kinematics and the human-machine interface are not described here: see [6] for a recent reference.…”

“…Furthermore, cognitive workload is reduced by tailoring the information shown to the operator. The research focuses on pipe cutting as an illustration of the generic approach, since this is a common repetitive task [6].…”

“…The parameters of SDP models are functionally dependent on measured variables, such as joint angles and velocities, normally defined in discrete-time terms [5]. However, in contrast to other recent research into SDP systems for the same machine [6], the present work utilises a new continuous-time SDP model that is not dependent on the sampling interval, and uses this to investigate uncertainties (including time-variations) in the system time-delay and deadband (section III).…”

Eigenvalue Analysis and Case Study Examples of Fractional Order Generalised Predictive Control

“…The movements of the manipulator joints are controlled through hardware and software integration using Labview R and associated National Instruments tools. Such dual-arm mobile robots offer a powerful option for nuclear decommissioning applications [17]- [19].…”