Effect of Redundant Constraints on Stress Distribution in Complicated Mechanisms

Large mechanisms, such as hydraulically operated portable stages, represent structures that are “frozen” in one position. Selection of the type of joints in these mechanisms can influence the stress distribution. There are different types of joints which engineers can use. The structures looking almost identical may have different types of joints. These structures, though functionally equivalent, have different numbers of the redundant constrains and different stress distribution. To find a combination of joints which minimizes the stress in the structure, one has to perform a search in the realm of integer numbers – the joint allows for the integer number of degrees of freedom only. Two methods of search are presented in the paper - one is based on the Fibonacci search. The other, called the pseudo gradient method, is similar to the steepest descent method for the functions of continuous variables. With the existing “smart materials” it is possible to design an “intelligent mechanism” fitted with “smart joints”, which, controlled by sensors and a computer, would ensure the optimum stress for any load situation.