Design of adjustable constant-force forceps for robot-assisted surgical manipulation

Force regulation is a challenging task of forceps used for robot-assisted surgical manipulation. To avoid excessive force applied on soft tissues, sophisticated sensors with computerized precise control are often required. Without using additional electronic elements, this paper presents a passive mechanism to maintain a constant contact force between forceps jaw tips and tissues given a pre-specified force magnitude. The mechanism consists of symmetric flexible structures specifically designed to generate a constant torque regardless of input rotation. The constant torque is converted to a constant force through an adjustable lever arm. When the force is further transmitted to jaw tips, it keeps a nearly constant contact force regardless of tissue stiffness and size. After a formulation to find the optimal mechanism configuration, the design is verified by comparing experiment and simulation results. A prototype of the adjustable constant-force forceps is finally illustrated and discussed. The novel forceps is expected to serve as a reliable alternative for robot-assisted surgeries.