Abstract: Dynamic connection hybrid mechanism derived from the auto-tilt device equivalent institutions of helicopter and can be widely used in the ball and socket bearing fatigue testing machine. Nested dynamic connection hybrid mechanism which transforms the upside and under hybrid mechanism of the helicopter automatic tilt to the inner and outer ring nested hybrid mechanism is proposed. Due to ball joints link between inner ring and outer ring, it has small size, low power consumption and high stability in the high-speed rotation. Based on screw theory, equivalent DOF approach is used in the DOF calculation of the hybrid mechanism. Numerical methods are used to solve positive displacement solution. According to the positive displacement solution, the workspace of the hybrid mechanism is analyzed. The results provide a reference for ball hinge bearing fatigue testing machine.

Key words: Equivalent DOF, Hybrid mechanism, Positive displacement solution, Reduced DOF, Workspace