Ball hinge-based three degree of freedom under-actuated robot wrist device

The invention relates to a ball hinge-based three degree of freedom under-actuated robot wrist device, which comprises a case with an input end and an output end, an output end of a ball hinge with three degrees of freedom and a power source input end, wherein the power source input end is a single power source composed of a rope III; the output end is inserted into the case through an end connection rod of the ball hinge; an under-actuation system consisting of a rope, a guide ring, a spring and the like is arranged in the case; the rope III is connected with the end connection rod through the under-actuation system; and the linear movement of the rope III at the input end drives the end connection rod to do the three-degree-of-freedom movement through the under-actuation system. The device can drive the output end to do the three-degree-of-freedom movement by a power source, has advantages of simple structure, low cost, light weight, small size, easy processing and maintenance, and can be used as a robot wr