Interactive linkage synthesis on a small computer

Abstract

An interactive computer program for the kinematic synthesis of motion or function generating linkages is described. The system has been implemented on an 8K IBM 1130 with a storage tube display and a custom-built “globe” graphical input device. The desired performance of the mechanism at four or five prescribed finitely separated positions is specified to the computer, as is the geometry of the fixed and moving bodies. Graphical input devices, or a keyboard, or cards can be used for this purpose. Interactive graphics capability allows input, modification, and display of a complex moving body and fixed frame. Burmester circlepoint-centerpoint curves or Burmester point pairs are displayed for the specified motion, together with a number of other options such as relative poles of rotation. A dynamic cursor which traverses the circlepoint-centerpoint curves allows selection of input and output links of either a four-bar linkage, a slider-crank mechanism, or a turning-block mechanism capable of satisfying the prescribed input criteria. A flashing display aids in selection of circlepoint-centerpoint pairs by indicating the type of linkage that would result from choice of the link being displayed at that instant Grashof's criteria are used to determine whether such a choice would result in a drag link, double rocker, or crank rocker mechanism. Similar criteria have been developed for the slider and turning block equivalents of these mechanisms. The selected linkage can then be animated on the display screen. Continous display of its transmission angle is optional. Examples are given of the practical use of the program.