OPTIMAL TENSION DISTRIBUTION AND STIFFNESS CONTROL OF A SPATIAL UNDER-CONSTRAINED CABLE SUSPENDED ROBOT

摘要

In under-constrained spatial cable suspended robots, maximum number of cables are equivalent to the number of degree of freedom, therefore the equations of kinetostatic have unique solutions and invention of positive cable tensile forces in these robots must come into being by redundant cables, springs or by Moving Platform (MP) weight. In this research, MP weight is considered to create tension in cables so both increasing workspace volume and decreasing possibility of cable encounter with together can be created because of using less cables. The range of MP weight to generate tension in cables is calculated by using Interval method, optimum weight is selected and then optimal tension distribution of cables is done according to the minimum norm of cable tensile forces so it is possible to use cables with different sizes and characteristics. By controlling the antagonistic stiffness different ways of increasing and decreasing of stiffness of robot is presented. Results can be used for applied targets of these robots such as heavy load handling applications in large workspace volume, welding and parts assembly which need stiffness control.