This paper addresses the problem of training of operators for telemanipulation tasks. In particular, it describes the development of a physics based virtual environment that allows a user to train in the control of an innovative robotic tool designed for the retrieval of spent nuclear fuels.

This paper presents a new robotic device whose main objective is to increase the flexibility of current systems used to carry out inspection and manipulation of spent nuclear fuel inside dry storage unit cells. Instead of using a rigid kinematic chain, the proposed device is based on the idea of a capsule that can be deployed inside a cell with the appropriate tool by means of a conventional crane and cable. The device is equipped with extendable actuators that immobilize the whole system inside the cell by pushing against the walls. This provides a stable platform for those tools that have to execute precision tasks. The system also comprises an industrial tool changer that allows the deployment of the required tool for each specific task. A first prototype of the device and a tool to retrieve spent nuclear fuel were built, and the results of the initial experiments are reported at the end of this paper.

A wavelet network (WN) friction model has been developed for robots where the friction is coupled, such that it is a function of the velocity of multiple joints. Wavelets have the ability to estimate random friction maps without any prior modeling while preserving linearity in the model parameters. The WN friction model was compared against the Coulomb+viscous (CV) model through experiments with the PHANTOM Omni haptic device (SensAble Technologies, MA, USA); however, the theory is valid for any serial-chain robotic manipulator. Ability to estimate applied motor torques was used as the performance metric, quantified using relative RMS values. During training of the WN model it outperformed the CV model in all cases, with an improvement in relative RMS ranging from 0.4 to 7.5 percentage points, illustrating the potential of the WN friction model. However, during testing of the WN model on an independent data set results were mixed, highlighting the challenge of achieving sufficient training.

A hybrid model/learning-based dynamic equation has been developed for robots in order to take advantage of the attractive features of both techniques. The regular dynamic equation is used to model the ideal behavior, while wavelets are used to learn the joint friction. The friction may be coupled, such that it is a function of the velocity of multiple joints. Furthermore, a system identification method has been designed to improve contact force estimation, using manual hand excitation in addition to motor excitation. The hybrid dynamic equation was implemented for the PHANTOM Omni haptic device (SensAble Technologies, MA, USA), and experiments were performed to compare using manual excitation with using motor excitation only. The results showed that manual excitation improved contact force estimation performance, with improvements in the relative RMS values ranging from 21% to 35%.

This paper presents a new approach to obtain three-finger robust grasps of 2D irregular objects. Given a discrete description of the object boundary, a partial representation of the force-closure space considering the position of two contact points is obtained. The computational cost of this representation is low and it still includes enough information to obtain suitable grasps as well as independent regions on the object boundary, such that a finger in each region ensures a force-closure grasp independently of the exact position of the contact points. The procedure has been implemented and several examples of the proposed methodology are included in the paper

Force-closure independent regions are parts of the object edges such that a grasp with a finger in each region ensures a force-closure grasp. These regions are useful to provide some robustness to the grasp in the presence of uncertainty as well as in grasp planning. Most of the approaches to the computation of these regions for N fingers work on the contact space, implying a N-dimensional problem. This paper presents a new approach to determine independent regions on polygonal objects considering N friction or frictionless contacts. The approach works on the object space, implying that it is always a two-dimensional problem and, since it is not necessary to compute all the force-closure space, it becomes a very fast approach. Besides, the approach is also flexible since constraints on the fingers placement can be easily introduced. Some graphical examples are included in the paper showing the simplicity of the methodology.

The paper deals with the determination of optimal force-closure grasps for 2D polygonal objects. The problem is analyzed and some intrinsic properties of grasps are determined. The approach is applied to the determination of the position of a fourth finger given the positions of three other fingers. Moreover, the range of solutions that allow the force-closure property as well as the optimal value are analytically determined, checking only four points in the worst case. The algorithm has been implemented and numerical examples are included in the paper.