3.FrameDesign.docVIP

FRAME DESIGN The frame of this robot has two main functions. It firstly contains all the parts of the robot that control its movement (the motors, batteries, speed controllers etc). Secondly, it facilitates easy climbing of the stairs by nature of its geometry. In order to accomplish both these aims, the frame must be of a sufficient size to hold all components and provide stability on the stairs. It must also be rigid enough to allow proper force application to the stairs, and hence stair climbing. The various parts of design will be examined in the coming section, looking at the materials used, the structure of corners and joints and the schematic design of component placement. Frame materials The frame was primarily constructed of aluminium angle bar, measuring 1 ? inch, by 1 ? inch by ? inch thick. This material was chosen for its combination of light weight (Aluminium having a low density) and rigidity. The rigidity is both a function of the geometry of the bars and the material they are made from. Figure 3.1, showing both profile and side views of the Aluminium bars used. The geometry of the bars is advantageous as it allows them to resist torsion in both the x-y directions along its length. As there is always a large depth of aluminium presented perpendicular to any bending force, the aluminium bar can be significantly lighter compared to a solid bar of the same strength. The flat shapes also allowed the elements to be easily assembled and offer each other support along the edges and faces of the bars. The floor on the base of the robot was constructed of ? inch plywood. The floor is not designed to carry structural load, but to instead offer a component mounting space. Being made of plywood means the floor is lightweight, and components can be easily screwed into it. Design The overall shape and size of the frame were determined by mathematical and geometrical concerns related to stair climbing and mounting (discussed previously in this report). The design