# Multi-Mode Compound Grasping Robot Finger Driven by Linkage
###### Abstract  
The current underactuated robot hands use a single actuator to drive multiple degrees of freedom, enabling them to perform grasping functions. This paper design a multi-mode compound grasping robot finger driven by linkage, called MCG hand. The MCG hand includes a base, two motors, three phalanx, multiple shafts, two motors, two driving wheels, four linkages, three springs, and two limit blocks. This unique design allows the MCG finger to perform various grasping modes, such as parallel, coupling, middle, and distal phalanx self-adaptive, proximal, and distal gesture-changeable modes, as well as their combinations. The device can independently control the rotation of the proximal phalanx and the distal joint and realize the parallel pinching action of the distal phalanx. It can also realize the coupling function of the proximal and distal phalanx. It has automatic adaptability to objects of different shapes and sizes. Furthermore, the MCG finger provides enveloping grasping with multiple contact points, resulting in a more stable grip. The easy switching between modes through simple control, along with its wide application range and low manufacturing and maintenance costs, make the MCG hand a versatile solution for various applications. robot hand; multi grasping modes; coupling grasping; self-adaptive grasping; gesture-changeable grasping; underactuated finger +
Footnote †: journal: Applied  
focus on improving the efficiency and reliability of robotic grasping through pick-point evaluation for a 2-F robotic gripper [13]. Underactuated fingers, including parallel (PA), coupling (CO), and self-adaptive (SA) grasping fingers, have been developed to address the limitations of dexterous hands. The distal phalanx of the parallel grasping finger always keeps the original posture relative to the base when it moves, which is suitable for grabbing objects placed on a plane. When the coupling grasping finger is leaning towards the object, all phalanxes rotate simultaneously, and the speed ratio of the second phalanx to the first phalanx is a scalar greater than 1. The coupling grasping finger is suitable for holding objects with the distal phalanx on the desktop. Self-adaptive grasping mechanisms allow robots to grasp objects of various shapes and sizes with minimal input from the control system. When actuating the self-adaptive finger, the proximal phalanx rotates, and the distal phalanx does not constantly rotate to the proximal phalanx. When the proximal phalanx contacts the object and is blocked, the distal phalanx continues to rotate automatically, which adapts to the different shapes and sizes of the object and achieves the envelope grasping effect [14; 15]. The self-adaptive grasping mode benefits from synchronized finger and wrist movements, which can improve the grasp success rates and mitigate object slippage during hand closure [16]. This can also be achieved by using soft materials [17] and pneumatic or hydraulic actuation [18]. The soft-rigid tendon-driven grippers investigated in [19] allow robots to grasp objects of various shapes and sizes with minimal input from the control system. These adaptive mechanisms have shown promise for improving grasp stability and versatility [20]. However, only the proximal phalanx is driven before grasping, and the distal phalanx does not have a grasping motion. The limited range of motion of the distal phalanx in self-adaptive fingers constrains their overall grasping capabilities. To overcome these drawbacks, researchers have focused on developing compound grasping modes that combine the strengths of parallel, coupling, and self-adaptive fingers. The integration of coupling and self-adaptive grasping mechanisms leads to the development of the coupling adaptive composite grasping mode (COSA mode) [12]. [PERSON] et al.