This paper proposes a novel tolerance design method for robot manipulators to select the optimal tolerances of kinematic parameters. A tolerance optimization model is presented to minimize the failure probability of positioning accuracy with the constraint of manufacturing cost. First, the performance function of positioning accuracy is constructed by performing the differential kinematics and eigen-decomposition concepts, which further combines the chi-square approximation and numerical integration methodologies to calculate the positioning accuracy reliability. An improved genetic algorithm is then presented based on the diversity crossover and differential mutation strategies to optimally and efficiently solve the tolerance design model. The applicability and performance of the proposed method are validated by the tolerance design of a 6-degree-of-freedom robot manipulator. The comparison with the existing techniques illustrates that the proposed method (i) processes better accuracy and efficiency in positioning accuracy reliability analysis; (ii) obtains a tolerance combination of kinematic parameters with a higher positioning accuracy reliability. The proposed method contributes to the optimal tolerance range selection and design of robot manipulators and other moving parts of machinery.
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