Erik Kyrkjebø

Ship replenishment using synchronization control

Abstract In this paper synchronization techniques are used to develop a control law for rendezvous control of ships. In particular, recent results on external synchronization in robotics are applied to the problem of rendezvous control of ships. No assumptions on the availability of a dynamic model for the replenished ship are made, and only position/attitude measurements are available for both ships. The synchronization closed loop error dynamicsis found to be bounded by the acceleration and velocity of the replenished ship, and the synchronization controller yields semi-global exponential convergence of the closed-loop errors for position keeping, and semi-global uniform ultimate boundedness of the closed-loop error during trajectory tracking.

Output synchronization control of Euler-Lagrange systems with nonlinear damping terms

A coordinated synchronization control scheme to synchronize two or more Euler-Lagrange systems with nonlinear damping in a leader-follower configuration is presented. The scheme is based on position measurements only, and no mathematical model of the leader is required. Observers are designed to estimate the velocity and acceleration of the systems, and the scheme yields semi-global ultimately bounded closed-loop errors for the output synchronization problem. The control scheme is valid for systems with nonlinear damping.

Adaptive Snake Robot Locomotion: A Benchmarking Facility for Experiments

A benchmarking facility for snake robot locomotion is presented, including the design of a snake-like robot extended with a sensor setup combining three-dimensional vision and an array of force sensors to register friction and impulse forces. A surrounding, modular environment consisting of a reconfigurable obstacle course and a ceiling mounted camera system is also presented. This enables research into adaptive obstacle-based and non-obstacle-based movement patterns for robotic snakes. Experimental results show possibilities for detailed data analysis of snake robot locomotion. Thus, the facility may be a common reference on which to experiment and evaluate future ideas.

A Virtual Vehicle Approach to Underway Replenishment

The problem of coordinated control of a leader-follower system is solved using a virtual vehicle approach to alleviate information requirements on the leader. The virtual vehicle stabilizes to a shifted reference position/heading defined by the leader, and provides a reference velocity for the synchronization control law of the follower. Only position/heading measurements are available from the leader, and the closed-loop errors are shown to be uniformly globally practically asymptotically stable.

A robotic concept for remote maintenance operations: A robust 3D object detection and pose estimation method and a novel robot tool

Future normally-unmanned oil platforms offer potentially significantly lower commissioning and operation costs than their current manned counterparts. The ability to initiate and perform remote inspection and maintenance (I&M) operations is crucial for maintaining such platforms. This paper presents a system solution, including key components such as a 3D robot vision system, a robot tool and a control architecture for remote I&M operations on processes similar to those on topside oil platforms. In particular, a case study on how to automatically replace a battery in a wireless process sensor is investigated. A novel robot tool for removing and re-attaching the sensor lid has been designed. Moreover, a robot control architecture for remote control of industrial-type robot manipulators is presented. A 3D robot vision system for localizing the sensor lid and the battery has been developed. The system utilizes structured light, using an off-the-shelf projector and a standard machine vision camera. A novel, robust and fast vision algorithm called 3D-MaMa has been adapted to work for object localization and pose estimation in complex scenes, in our case the process equipment in our lab facility. Experimental results from our lab facility are presented which describe a series of battery replacement operations for various unknown positions of the wireless sensor, and we report on accuracies and success ratios. The experiments demonstrate that the described vision system is able to recover the full pose and orientation of an object, and that the results are directly applicable for controlling advanced robot contact operations. Moreover, the custom-built lid operation tool demonstrates successful results.

Leader-Follower output reference state feedback synchronization control of Euler-Lagrange systems

A coordinated synchronization control scheme to synchronize two or more Euler-Lagrange systems in a leader-follower configuration is presented where the only information requirements of the leader are that of position and orientation only, i.e. the mathematical model with its parameters and the velocity and acceleration of the leader are considered unknown and unmeasured. An model-based nonlinear observer is designed to indirectly estimate the velocity and acceleration of the leader through the synchronization errors, and the observer-controller scheme is shown to give global uniformly ultimately bounded closed-loop errors.

Active camera control with obstacle avoidance for remote operations with industrial manipulators: Implementation and experimental results

Remote controlled robots on offshore oil and gas platforms can potentially reduce costs and improve environment, health and safety issues. A key to successful remote control is to provide onshore operators with a sufficient overview of the processes offshore. To this end, robot manipulators constitute flexible camera platforms, compared to e.g. simple pan-tilt units, for monitoring offshore operations. In this paper, we present a system solution and experimental results for real-time active camera control with obstacle avoidance for industrial manipulators based on weighted pseudoinverse redundancy resolution method. We extend the pseudoinverse solution for joint limit avoidance in combination with obstacle avoidance such that joint limits are gracefully avoided. A novel choice of stereographic projection provides robustness with respect to global stability and singularities. Implementation issues are addressed and the monitoring approach is experimentally validated on two Kuka KR-16 robot manipulators. Experimental results show that a follower robot with a camera is able to monitor and track a leader robot while simultaneously avoiding collisions. In addition, a robot control system architecture which ensures efficient and safe testing of new Matlab-implemented robot controllers is presented.

A Learning Camera Platform for Remote Operations with Industrial Manipulators

Abstract Robot manipulators may be used as flexible camera platforms by mounting cameras on the wrist of the robot. In this paper we present a new way of interaction between an operator and the camera platform, where the operator wants to get a visual overview of a remote operation. The goal is to relieve the operator from controlling both the operation and the camera platform simultaneously, and allow the operator to focus only on the operation while the camera plaform is automatically controlled based on learned operator preferences. We describe an architecture for learning from operator inputs, and use an active camera control algorithm as a base for learning. An M-RAN sequential function approximator is used as memory function. Experimental results on a demonstration case indicate that the camera platform responds to and remembers differences in operator preference.

Stereographic projection for industrial manipulator tasks: Theory and experiments

In this paper, we present a solution and experimental results for real-time control of manipulation tasks considering the alignment of a robots end effector relative to some reference. The developed controller is applicable to industrial manipulators and is based on the pseudoinverse redundancy resolution method. The application considered is the employment of two industrial robots in an offshore remote inspection and maintenance system. A leader robot is controlled freely from onshore, and a follower robot uses an attached camera to provide the onshore operator with live video feed of the ongoing operation. Robot manipulators constitute flexible camera platforms, compared to e.g. simple pan/tilt units, for monitoring offshore operations. We develop a controller for the follower robot such that automatic camera tracking is achieved using pseudoinverse redundancy resolution control. A minimal task space parametrization relying on stereographic projection is constructed which achieves relative end effector alignment tracking without introducing representational or algorithmic singularities. It is shown that singular configurations will only in special cases affect the closed loop behavior. The controller is applicable to tasks such as spray painting or polishing on curved surfaces. The control approach is experimentally validated on two Kuka KR-16 industrial robot manipulators.

MVT: A marine visualization toolbox for Matlab

Abstract This paper introduces a new toolbox for use with Matlab® and the Virtual Reality Toolbox 3.0. The toolbox is intended to assist in the performance analysis of multivariable systems and to help presenting the experimental results. The toolbox displays up to 6 DOF data from simulations, experiments or measurements of marine control systems as 3D animations. The animations may be viewed on-line or saved to file.