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

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

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

The Dynamic Performance of Robot Manipulators Under Different Operating Conditions

The dynamical performance of robot manipulators is greatly affected by the different payloads handled by the end effector (hand). Hence, it is very important, especially for industrial applications, to study the different interconnected relationships between the manipulator joints, speeds, loads and actuation forces. In this paper, a simplified symbolic Lagrangian representation of the different terms presented, with emphasis on the coriolis and centripetal effects. The accuracy and computational efficiency of this new formulation is demonstrated by simulation of a Stanford and PUMA 560 manipulator. Useful quantitative measurements and error analysis are also included on the significance of coriolis and centripetal terms under different load and speed conditions

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

Fast Forward Dynamics Algorithm for Robot Arms Using Multi-Processing

The computation of the direct dynamics problem (forward dynamics) plays a major role in the real-time computer modelling and simulation of robot manipulators. The efficient and computationally inexpensive solution of this problem facilitates the design of real-time robot simulators. In addition, it allows for a better understanding of the key elements affecting robot operations. This work proposes to solve this problem by employing parallel and distributed processing techniques. First, a parallel implementation of a simplified Lagrange-Euler formulation is used to solve for the dynamics. Second, a resulting system of linear equations is solved using Gaussian-Elimination with simple row interchange. Both algorithms are distributed over a multiple-instruction, multiple-data stream (MIMD)computer architecture

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