Abstract: A 7-DOF cooperative manipulator was designed and manufactured based on the joint driven by dual motor servo. The geometric error model of the end-effector of the manipulator was established， and the parameter errors were analyzed and synthesized based on the principle of independent action of the original parameter errors. Based on the law of large numbers of mathematical statistics and Monte Carlo method， the sensitivity of influencing factors of the geometric position errors was analyzed by numerical simulation， and the parameter errors which have relatively greater influence on the geometric position errors of the manipulator were found. Through the calculation and analysis of the geometric position errors of the end-effector of the manipulator， it was found that the errors obey the Rayleigh distribution in the workspace of the manipulator. The experimental measurement showed that the repeated positioning error of the manipulator is less than 0.0591mm， and the absolute positioning error obeys Rayleigh distribution significantly. It proved that the double motor servo-driven joint has the characteristics of small return errors and high transmission accuracy， and the error analysis is correct， which provides a theoretical basis for the precision design and application of the manipulator.

Key words: 7-DOF manipulator; structural design; error model; sensitivity analysis; error analysis