This paper studies the static rigidity behaviour of a parallel manipulator with legs modelled as elastic members under axial loading. Structurally, a parallel module is more rigid compared to a serial module and is expected to take heavier payloads. Therefore, a guidance for design of such parallel manipulators is needed which leads to maximum rigidity over the workspace. In the present work, the authors propose the concept of the flexibility ellipsoid for a parallel system. Various scalar measures of rigidity are formulated on the basis of the proposed ellipsoid. An algorithm, involving multiple objective nonlinear programming technique, is implemented to decide upon some important design parameters of a generalised six degrees of freedom Stewart platform type parallel manipulator. It is observed that irrespective of the other parameters, parallel manipulators with the legs pairwise joined at the top platform possess the highest rigidity. Moreover, there exists certain kinematic dimensions for which the designed parallel system is completely free from all sorts of singularity.

An iterative procedure for obtaining dynamic model of manipulator has been proposed in this paper. The high efficiency of the procedure is reached on the basis of iterative relations of dynamic parameters. For general six revolute joint manipulator, the complete dynamic model i.e. matrices H(q), C(q), G(q) and vector of joint torques 13. requires 992 multiplications and 776 additions. When the complete dynamic model is given by 13. the number of operations reduces to 863 multiplications and 773 additions.

The problem associated with planning a collision-free path for a wheeled mobile robot (WMR) moving among obstacles in the workspace is investigated in this paper. A kinematic model, including the general nonholonomic constraint equation, is developed first, followed by the analysis of some general maneuvering characteristics of the WMR. The analytic solutions to the typical path curves, such as circle and straight line, which are important in the path planning problem, are also derived. From the analysis of the established kinematic model, some factors which affect the path planning problem for a WMR and therefore must be taken into account are revealed and the general description of the path planning problem for a WMR is formuated. In conclusion, a possible architecture of the algorithm for a practical WMR is presented.

The author makes the point that progress is slow, though inexorable, and one can discern an upward drift of unemployment, even in good times. After analysing the various views concerning this phenomenon, the author points to two major problems, viz. the transitional one of the redundant heavy manual worker and the long-term one of employment for the unskilled. He then considers these problems from the point of view of automation and robotics with particular reference to the reaction of the human society to the qualitative changes in the manufacturing industries.

Lately, there have been numerous applications of computer algebra to special functions used in the various field of science and engineering. In this paper, we consider an efficient algorithm which generates velocity Jacobians for any class of general serial link manipulators in a compact form throughout the effective use of frame transformations. Compared with conventional techniques, a marked improvement of that capability is found in computer algebra applications to one class of a seven-joint manipulator. Together with finding of explicit solutions for joint rates, closed form arm solutions for the desired position of the hand are presented by relating the rotational motion of the elbow to a geometry problem.

In the authors' previous paper,10 an input shaping method was presented to reduce motion-induced vibrations effectively for various classes of flexible systems. In this paper, the effectiveness of the shaping method is experimentally demonstrated with a two-link flexible manipulator system

The manipulator for experiments includes two revolute joints and two flexible links, and moves on a vertical plane under gravity. An analytic model is developed considering the flexibility of the system and its joint stiffness in order to derive an appropriate estimation of dynamic modal properties. The input shaping method used in this work utilizes time-varying modal properties obtained from the model instead of the conventional input shaping method which employs time-invariant modal properties. A point-to-point motion is tested in order to show the effectivess of the proposed shaping method in vibration reduction during and after a given motion. The given reference trajectories are shaped to suppress the motion induced vibration. The test results demonstrate that the link vibration can be greatly suppressed during and after a motion, and the residual vibration reduction was observed more than 90% by employing this time-varying impulse shaping technique.