An optimal tolerance allocation problem is formulated for open linkage systems and the optimum is obtained by the recursive quadratic programming method. Tolerances on the link parameters and clearances in the joints are treated as random variables. Revolute and prismatic joints with clearances are modeled probabilistically and tolerances are assumed to be distributed normally. The mechanical error of the linkage path is calculated at several points and represented as random variables in 3σ band of confidence level. Minimization of manufacturing cost is performed under the constraints of component reliabilities and system reliability which are related to the mechanical errors.
Tolerances and clearances of several industrial robots are optimally allocated by the proposed method.
