A Stiffness-Adjustable Hyperredundant Manipulator Using a Variable Neutral-Line Mechanism for Minimally Invasive Surgery

Abstract

Abstract-In robotic single port surgery, it is desirable for a manipulator to exhibit the property of variable stiffness. Small port incisions may require both high flexibility of the manipulator for safety purposes, and high structural stiffness for operational precision and high payload capability. This paper presents a new hyper-redundant tubular manipulator with a variable neutral-line mechanisms and adjustable stiffness.A unique asymmetric arrangement of the tendons and the links realizes both articulation of the manipulator and continuous stiffness modulation. This asymmetric motion of the manipulator is compensated by a novel actuation mechanism without affecting its structural stiffness.The paper describes the basic mechanics of the variable neutral-line manipulator, and its stiffness characteristics. Simulation and experimental results verify the performance of the proposed mechanism.Index Terms -Variable neutral-line mechanism, snake-like manipulator, adjustable stiffness, medical robot.

Design and analysis of a wire-driven flexible manipulator for bronchoscopic interventions

“…3(c) illustrates the manipulator in a bending position. A common drawback with the wire-driven mechanism like the proposed design, whose length invariant neutral line is located in the middle, is that the manipulator can have various configurations with the same wire length changes [10]. In fact, according to our preliminary experiments in which non-elastic fishing lines were used to drive the robot, the tubular arm would hardly keep straight when the motors pulled it back from a bending position.…”

“…The basic principle in the design of wire-driven robot requires a flexible vertebra to support the continuum body, and antagonistic tendons running outside at equal separation to control the body configurations. Amounts of relevant studies have been done [5]- [10], and two categories can be found from these designs.…”

“…Li et al proposed to use spherical joints to connect rigid links and built a multi-section snake-like robot [5]. Kim et al proposed the neutral-line mechanism that strings disks with cylindrical surfaces, which is capable of changing its own stiffness by adjusting the tension of wires [10]. Its simple geometry also facilitates miniaturization.…”

Regularization of the Spatial Inverse Positioning Problem of Revolute Joint Manipulators

“…redundant manipulators [4], the differential inverse kinematics algorithm should be used that calculates the required joint velocities for the desired end effector velocities using the inverse of the analytical Jacobian of the manipulator's forward kinematics map. However, the inverse kinematics problem is burdened with singular configurations, in which the Jacobian matrix becomes singular.…”

Mechanical stiffness augmentation of a 3D printed soft prosthetic finger

“…Variable or tunable stiffness within a mechanism and/or machine has always been a desirable property. Early stiffness enhancing efforts for hyper-redundant and/or continuum manipulators are based on controlling the tension in the tendon-cables, if the manipulator is tendon-driven [27] or controlling the pressure in the air-muscles (e.g. McKibben), if the manipulator is pneumatically actuated; hence provide sufficiently low stiffness regulation [28].…”