A kind of traction underactuated pull in manipulator based on planetary gear mechanism is designed. The fingers of the manipulator are distributed circumferentially, which is suitable for grasping rigid and flexible objects. The most obvious advantages of the manipulator are as follows:
(1) By using the planetary gear mechanism, the output of two mutually exclusive motions is realized. According to this feature, a resistance torque adjusting mechanism is designed to adjust the clamping force without sensors and force feedback.
(2) With the traction of the belt, the manipulator has not only the function of clamping, but also the function of pulling in, providing a new form of grasping. At the same time, the manipulator can grasp both rigid objects and flexible objects.
(3) The control system of the whole machine is simple, and the infinite rotation of the synchronous pulley will prevent the motor from stalling.
Through the clamping force test, it is concluded that the clamping force adjustment range of the resistance torque adjustment mechanism is about 1~20 N, which verifies the effectiveness of the resistance torque adjustment mechanism. Grasping experiments show that the under actuated manipulator designed in this paper can completely achieve the clamping and pulling operation of rigid and flexible target objects under the expected design goals, which reflects the adaptability and flexibility of the manipulator for different target objects.