Compliant joints composed of slit tubes or springs are commonly utilized for steerable endoscopes and catheters. Because this type of joint is actuated by means of its elasticity, it is difficult to bend it with a small radius of curvature. In order to overcome this problem, a hyper-redundant Pulleyless Rolling joint with Elastic Fixtures (PREF joint) is proposed. To enable miniaturization, the PREF joint does not have a pulley, and the rolling contact motion aids the actuation cables to maintain the tension. The elastic fixtures guarantee a stable rolling motion at the center of the rolling surfaces. In this paper, the fundamental characteristics for the unit and the hyper-redundant PREF joints are presented. Moreover, design considerations are proposed for the PREF joint including the rolling tooth shape, structure of the elastic fixtures, and cable actuation method. The validity of the design is verified using finite-element analysis and a 10 mm diameter prototype composed of 12 units of PREF joints for a 1 degree-of-freedom motion. As a result, the 55 mm long joint can be bent up to ±180° with low actuation tension. The presented guidelines will assist in the development of various steerable instruments for medical applications.

This paper proposes a surgical manipulator with workspace-conversion ability for both minimally invasive surgery (MIS) and open surgery. The focus of the proposed surgical manipulator is on its potential use in places such as battlefields, army camps, and rural areas rather than in civilian hospitals. The proposed surgical manipulator has a workspace for MIS with a virtual remote center of motion and has a workspace for open surgery like that of an articulated manipulator. The mechanism of the surgical manipulator is proposed and implemented in this paper. A new distal rolling joint with two spiral wire ropes is also implemented. Several experiments to validate the feasibility of the surgical manipulator were carried out. Two fundamentals of laparoscopic surgery tasks were performed to compare the performance of the surgical manipulator with other MIS systems. The workspace conversion from MIS to open surgery was implemented. The workspace-conversion ability enables the surgical manipulator to attach or detach the surgical tool unit without human assistance or an assistant robot.

Various slim robots, such as surgical robots or humanoid robot fingers, are remotely actuated using transmission cables. If pull–pull drive is applied to actuate them using circular driving spools regardless of the shape of the joints, the tension of the driving cable becomes difficult to be maintained properly. Fortunately, it is possible to solve such a cable slack problem by providing an appropriate cable actuation length to the joint structure of the robot from the cable driving unit. Therefore, we propose a harmonious nonlinear cable actuation mechanism suitable for driving noncircular shaped joints. The proposed cable driver can mechanically provide the required cable actuation length to suit the angle change of the target joint using a pair of noncircular pulleys without increasing the number of actuators. In this paper, a design methodology of a noncircular pulley that can be applied to pulleyless rolling joints (PR joints) as well as pulleyless hinge joints is shown. Moreover, a practical cable driver is designed for actuating a hyper-redundant discrete bending joint composed of PR joints, and its effectiveness is verified through experiments. This novel cable actuation mechanism using noncircular pulleys or gears is expected to be applicable to various miniature robots such as surgical robots and animal robots of continuum structure in the future.

This paper deals with the design, modelling, fabrication, and experiments of a novel continuum robot that can be used for cardiovascular interventions. In this paper, a new design of bending joints of the continuum robot and its kinematical modelling are proposed. The bending joints of the proposed robot are designed to be easy to miniaturize and have a wide motion range. The continuum robot consists of an inner guide and an outer guide, each having two degrees of freedom (DOF). The 2DOF bending joints are driven by antagonistic actuation and the actuation part of the continuum robot is implemented to control the stiffness of the bending joints. When the pretensions of the cables of the bending joints are adjusted, the structural stiffness of the bending joints can be controlled. In this paper, the entire system of the continuum robot has been implemented and the basic performance of the proposed continuum robot has been verified. The proposed robot was confirmed to be bent actively in the S-shape curve.