Abstract
PurposeCompliant mechanisms are commonly used in the design of manipulator and surgical robotic tools for minimally invasive surgery (MIS) thanks to their compactness, ability of miniaturization and lower part count. However, conventional compliant joint has higher internal stiffness, which limits the bending radius. To overcome this problem, a novel tendon-driven manipulator structure based on monolithic compliant rolling-contact joint (CRCJ) is proposed.MethodsThe proposed rolling-contact mechanism is used to prevent cable slack during actuation, which occurs in conventional compliant joint design. By means of selective laser sintering (SLS) technique, the CRCJ can be fabricated in a monolithic structure, thus granting the CRCJ both the advantages of compliant joints and rolling-contact mechanism. Simulations with nonlinear finite element analysis (FEA) and experiments were conducted to evaluate and compare the mechanical properties of the proposed CRCJ with conventional leaf-type compliant joint including the bending and compliant motion.ResultsExperimental results showed that the CRCJ has lower bending stiffness, higher maximum bending angle (over 180^{circ }) and a higher compliance compared to conventional compliant hinges, which allows a larger workspace and reduces the possibility of tissue injury. Agreement was also found between the nonlinear FEA and experiments regarding the relation between actuation force and bending angle. A primary prototype of a 3-DOF handheld laparoscopic manipulator with a diameter of 7 mm was further developed.ConclusionA dexterous tendon-driven monolithic manipulator structure based on CRCJ for MIS is proposed. A preliminary prototype of a handheld laparoscopic manipulator demonstrates the capability of the CRCJ for steerable medical devices. However, design improvements based on FEA and application-orientated prototypes considering anatomical requirements still show room for improvements.
Highlights
Since the first laparoscopic cholecystectomy back in 1985 by the German surgeon Prof
We introduce a monolithic compliant rollingcontact joint (CRCJ) based on the concept in [16], in which a rolling-contact joint and its crossways arranged flexible bands are in one single part
The design of a novel monolithic tendon-driven manipulator structure using compliant rolling-contact joint (CRCJ) is proposed, which combines the advantages of both compliant mechanism and rolling-contact mechanism
Summary
Since the first laparoscopic cholecystectomy back in 1985 by the German surgeon Prof. In contrast to discrete joints, compliant joints are the second category, which can be fabricated monolithically Due to their monolithic structure and intrinsic elasticity, compliant joints are able to bend continuously, can be denoted as continuum joints. While this kind of joints can be fabricated using conventional reductive manufacturing techniques such as laser cutting and computer numerical control (CNC) milling, the development of additive manufacturing techniques has promoted the research on compliant joints in medical fields. Feng et al developed a spring-like flexible joint which was manufactured using selective laser melting (SLM) technology [11]
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