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This paper presents performance charts that map the design space of a bio-inspired robotic condylar hinge joint. The joint mimics the design of the human knee joint by copying the condylar surfaces of the femur and tibia and by copying the four-bar motion of the cruciate ligaments. Four aspects of performance are modeled: peak mechanical advantage, RMS (root mean square) mechanical advantage, RMS sliding ratio, and range of movement. The performance of the joint is dependent on the shape of the condylar surfaces and the geometry of the four-bar mechanism. The design space for the condylar hinge joint is large because the four-bar mechanism has a very large number of possible configurations. Also, it is not intuitive what values of design parameters give the best design. Performance graphs are presented that cover over 12,000 different geometries of the four-bar mechanism. The maps are presented on three-dimensional graphs that help designers visualize the limits of performance of the joint and visualize tradeoffs between individual aspects of performance. The maps show that each aspect of performance of the joint is very sensitive to the geometry of the four-bar mechanism. The trends in performance can be understood by analyzing the kinematics of the four-bar mechanism and the shape of the condylar surfaces. [ABSTRACT FROM AUTHOR]

This paper presents a backwards design method for mechanical conceptual design. The method involves starting with a very idealistic semiworking solution and then systematically solving the unworkable parts of the solution until a complete solution is found. The method can work in conjunction with other methods such as Theory of Inventive Problem Solving (TRIZ) or brainstorming. The method tries to exploit the principle that it is easier to critique and modify a design than it is to create a fully working solution in one go. The visual nature of the method means that it is suited to design problems where geometry is important such as mechanism design and machine design. Three case studies of conceptual design are presented. The case studies involve a novel clutch, a novel rotary damping mechanism and a novel worm gearbox. Each of these designs won at least one national design competition in the UK. A simple design experiment has been carried out which indicated that the backwards design method was at least as effective as the morphological chart method for a simple machine design exercise. [ABSTRACT FROM AUTHOR]