Co ordinate Transformations and Programming For Small Revolute Coordinate Robots

Inorder for a robot and effector to make contact at any orientation with a workpiece in general 3-D space, the robot must be provided with six degrees of freedom

Direct Digital Control of the Electric Arc Furnace

The paper explains the various aspects of control required in electric arc furnace operations and sunmmarises the present status of research in these areas. The requirements for direct digital control are considered and suitable hardware and software schemes for digital control implementation are presented

Quantum-mechanical tunnelling and the renormalization group

We explore the applicability of the exact renormalization group to the study of tunnelling phenomena. We investigate quantum-mechanical systems whose energy eigenstates are affected significantly by tunnelling through a barrier in the potential. Within the approximation of the derivative expansion, we find that the exact renormalization group predicts the correct qualitative behaviour for the lowest energy eigenvalues. However, quantitative accuracy is achieved only for potentials with small barriers. For large barriers, the use of alternative methods, such as saddle-point expansions, can provide quantitative accuracy.Comment: 9 pages, 5 figures, to appear in Phys. Lett.

On the Complexity Analysis of the Coriolis and Centripetal Effects of a 6 DOF Robot Manipulator

The equations used in calculating the different forces and torques which control the movement of a robot manipulator involve a considerable amount of differential and non-linear terms which possess high computational complexity. Centripetal and Coriolis effects are of great importance when the manipulator is moving at high speeds. The previous effects, based on the Lagrangian formulation, have been simplified and a lower order form produced which has reduced computational complexity. Simulation results for a robot arm have been obtained to check for the validity of the derivation

Robot Inverse Dynamics Computation Via VLSI Distributed Architects

The computation of the highly coupled dynamic equations has always posed a bottleneck in real-time dynamic control of robot manipulators. Recent advances in VLSI technology make it possible to implement new algorithms that complete these equations and meet real-time constraints. Parallel processing techniques can now be used to reduce the computation time for models of a highly mathematical nature such as the dynamical modelling of robot manipulators. In this work a semi-customised symbolic form of the Lagrange-Euler is divided into subtasks and distributed on a parallel processing system. The development system used consists of an INMOS TRANSPUTER (a VLSI single chip computer) running the OCCAM concurrent programming language. Further, this network is used to introduce parallelism by using different task allocation strategies which flow naturally from the Lagrange-Euler formulation

Inclusion of Shear Deformation Term to Improve Accuracy in Flexible-Link Robot Modelling

The paper is addressed at the problem of developing a static and dynamic model of a single flexible manipulator link which is of sufficient accuracy for use in a multi-flexible-link system. Although flexible link modelling has received much attention in the past, none of the models developed have adequate accuracy for application in a multi-link system. Very high modelling accuracy is necessary because there is significant inter-link coupling in a flexible manipulator and any modelling errors are therefore cumulative.Previous work based on an assumed mode model has made some progress towards improving accuracy by including a correction factor derived from finite element analysis and the work work reported here extends this by including a shear deformation term in the equations. The significant improvements in modelling accuracy thereby achieved are demonstrated by simulations of link motion

Quadratic Optimal Control of a Two Flexible-Link Robot Manipulator

This paper is addressed at the problem of controlling a two-flexible-link manipulator system. Manipulators with some flexible links are attractive if high speed motion is required in manufacturing operations because they avoid the severe control problems associated with the large inertia forces generated when the large mass, rigid links in conventional robot manipulators move at high speed. In fact, only two of the links within a typical six degrees of freedom revolute-geometry industrial robot cause significant inertia forces and so only these two links need to be flexible. The development of a two-flexible-link system controller is therefore very relevant to larger manipulators because it can be readily expanded by adding simple controllers for the other rigid links. Two-alternative controllers are developed in this paper, a computed-torque controller and a quadratic optimal controller. Simulations confirm the superior performance of the latter

Static and Dynamic Modelling of a Two-Flexible-Link Robot Manipulator

This paper is addressed at the difficulty of accurately modelling a two-flexible-link manipulator system, which is a necessary prerequisite for future work developing a high performance controller for such manipulators. Recent work concerned with the development of an accurate single-flexible-link model is first reviewed and then the expansion of a single-link model into a two-flexible-link system in a way which properly takes into account the coupling and interactions between the two links is discussed. The method of approach taken is to calculate the elastic and rigid motions of the links separately and then to combine these according to the principle of superposition. This application of the model developed is demonstrated in a simulated two-flexible-link system

Identification of Robot Dynamics: A Parallel Processing Approach

Knowledge of the exact characteristics of robot manipulators is one of the most significant factors in designing motion control systems, since the control performance is directly dependant upon the accuracy of the dynamic model. Dynamic models normally have complicated behaviour, including varying inertia depending upon the arm configuration, uncertain load effects, non-linear effects such as the Coriolis and Centripetal forces and interactions among joints. Unless these characteristics are included in the manipulator dynamics exactly, the performance of the controller is not expected to meet the given requirements. This necessitates the development of an efficient method to identify the dynamic parameters of robot arms. This paper will describe the on-line estimation of the link inertial parameters using a semi-customised symbolic representation of the dynamic equations based on the Lagrangian formulation.......

Multi-Mode Modelling of a Flexible Link Robot Mnaipulator

This paper is addressed towards the problem of developing an accurate static and dynamic model for a two-flexible-link manipulator. The inadequacy of existing techniques for flexible link modelling is explained and a new formulation, based on an assumed mode modelling technique with a correction factor derived from finite element analysis, is derived. This takes account of second and third modes in the dynamics and is shown to provide an improvement in model accuracy compared with most modelling algorithms which neglect these higher models