PISA finger: A novel parallel and self-adaptive underactuated finger with a single chain transmission mechanism

The traditional underactuated robot hand has only one grasping mode. Underactuated robot hand with combination grasping mode mostly adopts double chain transmission mechanism, which are corresponding to two kinds of grasping mode respectively. The double chain transmission mechanism has the disadvantages of complex system and large internal friction. This paper presents a novel design of a parallel and self-adaptive underactuated robot finger with a single chain transmission mechanism, called PISA finger. The method uses two link rod, a slider, a limit, a block and a spring to achieve using a single motor to drive a multiple finger phalanges. The PISA finger can realized the pinching grasp or enveloping grasp. The composition and movement process of the PISA finger are introduced in detail, and its internal structure is theoretically analyzed. The PISA finger has the receiver on the proximal phalanges, the object pushes the receiver to drive the distal phalange to envelop the object. The PISA finger parameter model is established to analyze the force condition of the receiver. Simulation and experimental results show that the PISA finger can automatically switch the grasping mode according to the different positions and shapes of the object so as to achieve stable grasping. The PISA hand is suitable for both industry and home application.