Differential-velocity driving device and mechanical arm to which the differential-velocity driving device is applied

A mechanical arm, comprising:

• a base platform;
• at least one differential-velocity driving device, including:
• a first rotary driving element;
• a first transmission gear connected to and rotationally driven by the first rotary driving element;
• a second rotary driving element;
• a second transmission gear connected to and rotationally driven by the second rotary driving element, the second transmission gear having the same number of teeth as the first transmission gear;
• a fixing member connected to the first rotary driving element and the second rotary driving element such that the first rotary driving element does not move or rotate with respect to the second rotary driving element, the fixing member fixing the differential-velocity driving device to the base platform;
• a power output gear engaged with the first transmission gear and the second transmission gear;
• an output shaft passing through an axle center of the power output gear and being coaxial with the axle center;
• a limiter provided on the output shaft and connected to at least two points of the output shaft, the at least two points being located on an inner side and an outer side of the power output gear, respectively, the limiter being preventing the power output gear from being detached from the first transmission gear and the second transmission gear and preventing the output shaft from being detached from the power output gear;
• a swing arm with one end connected to the limiter;
• and
• a rod with one end pivotally connected to the other end of the swing arm;
• and
• a moving platform pivotally connected to the other end of the rod of the differential-velocity driving device.