Yosuke Nishitani

Robotic Forceps Manipulator With a Novel Bending Mechanism

This paper proposes a new bending technique with a screwdrive mechanism that allows for omnidirectional bending motion by rotating two linkages, each consisting of a right-handed screw, a universal joint, and a left-handed screw. The new screwdrive mechanism, termed double-screw-drive (DSD) mechanism, is utilized in a robotic forceps manipulator for laparoscopic surgery. A robotic forceps manipulator incorporating the DSD mechanism (DSD forceps) can bend without using wires. Without wires, it has high rigidity, and can bend at 90° in any arbitrary direction. In addition, the gripper of the DSD forceps can perform rotational motion, which is achieved by rotating a third linkage in the DSD mechanism. Opening and closing motions of the gripper are attained by wire actuation. Fundamental experiments examining the bending force and the accuracy of the DSD forceps were conducted, and an analysis of the accuracy was performed. Control of the DSD forceps through a teleoperation system was achieved via a joystick-type manipulator. A servo system was constructed for each linkage and the wire actuation mechanism, and tracking control experiments as well as a suturing experiment were conducted. The results of the experiments showed that the required design specifications were fulfilled. Thus, the validity of the DSD forceps was demonstrated.

Influence of silane coupling agents on the rheological behavior of hemp fiber filled polyamide 1010 biomass composites in molten state

In order to develop the new engineering materials such as structural materials and tribomaterials based on all plants-derived materials, the influence of silane coupling agent on the rheological properties of hemp fiber (HF) filled polyamide 1010 (PA1010) biomass composites in molten state was investigated for one step of the fabrication of these materials. PA1010 was made from sebacic acid and decamethylenediamine, which are obtained from plant-derived castor oil. Hemp fibers were surface-treated by two types of surface treatment: a) alkali treatment by NaOH solution and b) surface treatment by silane coupling agents with different concentrations. Three types of silane coupling agents: aminosilane, epoxysilane and ureidosilane were used for surface treatment. HF/PA1010 composites were extruded by a twin screw extruder and compression-molded. Rheological behavior in molten state were evaluated by oscillatory flow testing using a parallel plate type rheometer. It was found that the silane coupling agents r...

Effect of addition of plants-derived polyamide 11 elastomer on the mechanical and tribological properties of hemp fiber reinforced polyamide 1010 composites

For the purpose of developing the new engineering materials such as structural materials and tribomaterials based on all plants-derived materials, the effect of the addition of plant-derived polyamide 11 Elastomer (PA11E) on the mechanical and tribological properties of hemp fiber(HF) reinforced polyamide 1010 (HF/PA1010) composites was investigated. PA1010 and PA11E (except the polyether groups used as soft segment) were made from plant-derived castor oil. Hemp fiber was surface-treated by two types of treatment: alkali treatment by NaOH solution and surface treatment by ureido silane coupling agent. HF/PA1010/PA11E ternary composites were extruded by a twin screw extruder and injection-molded. Their mechanical properties such as tensile, bending, Izod impact and tribological properties by ring-on-plate type sliding wear testing were evaluated. The effect of the addition of PA11E on the mechanical and tribological properties of HF/PA1010 composite differed for each property. Izod impact strength and spec...

Robotic hand with a new bending mechanism

Recently, the development of a versatile robotic hand aiming at the application to an artificial arm or a humanoid robot is in demand. In this paper, omni-directional bending mechanism called “double-screw-drive mechanism” was applied to a robotic hand. The robotic hand with three fingers was built, and experiment was carried out, in which each fingertip was controlled so as to track the elliptical orbit. Then, the DSD robotic hand succeeded in rotating the cap of the PET bottle and removing the cap from the bottle.

Dynamic viscoelastic properties of long organic fibre reinforced polypropylene in molten state

This paper deals with the dynamic viscoelastic properties of long organic fibre (aramid fibre (KF), polyvinyl alcohol fibre (VF) and polyamide fibre (PA6)) reinforced polypropylene in the molten state. Long organic fibres mixed with polypropylene fibres by an apparatus called a “fibre separating and flying machine″ were compression moulded into 3mm thick composites. Dynamic viscoelastic properties of these composites were measured in the molten state using a rotational parallel plate rheometer. It was found that the dependence of angular frequency on storage modulus, G′, for long organic fibre reinforced polypropylene is different from that of volume fraction of fibre, Vf and the relationships depend on the characteristics of the reinforcing organic fibres. The slope of the dynamic viscosity, η′ vs. angular frequency, ω curves increases gradually up to 45 degrees with increasing Vf. Influence of fibre content on dynamic viscoelastic properties depends on the organic fibre used. For low fibre content, G′ increases with increasing Vf in the same way as η′. However, the opposite trend is observed for high fibre content composites. It can be deduced that there is an apparent yield from the relations between complex viscosity, η* and complex modulus, G*. The yield value, G*y increases gradually with increasing fibre content and approaches a fixed value. All of the long organic fibre reinforced polypropylenes studied here are more sensitive to temperature than inorganic fibre reinforced composites.

Influence of types of alkali treatment on the mechanical properties of hemp fiber reinforced polyamide 1010 composites

In order to develop the new engineering materials such as structural materials and tribomaterials based on all plants-derived materials, the purpose of this study is to investigate the influence of types of alkali treatment on the mechanical and tribological properties of hemp fiber (HF) reinforced plants-derived polyamide 1010 (HF/PA1010) biomass composites. HF were surface-treated by four types of surface treatments: (a) alkali treatment by sodium hydroxide (NaOH) solution, (b) alkali treatment by sodium chlorite (NaClO2) solution, (c) alkali treatment by NaOH solution and surface treatment by ureido silane coupling agent, and (d) alkali treatment by NaClO2 solution and surface treatment by ureido silane. The volume fraction of hemp fiber in the composites was fixed with 20vol.%. HF/PA1010 composites were extruded by a twin screw extruder and injection-molded. Mechanical properties such as tensile, bending and tribological properties by ring-on-plate type sliding wear testing were evaluated. It was foun...

Effect of processing sequence on the dynamic viscoelastic properties of ternary biomass composites (Hemp fiber/PA1010/PA11E) in the molten state

For developing the new engineering materials such as structural materials and tribomaterials based on all plants-derived materials, we investigated the effect of processing sequence on the dynamic viscoelastic properties of the ternary biomass composites: 5mm cut hemp fiber (HF) filled polymer blend of plants-derived polyamide 1010 (PA1010) and polyamide 11 elastomer (PA11E) composites in the molten state. PA1010 and PA11E, which contain the polyether groups as soft segment, were made from plant-derived castor oil. The composition of the polymer blend of PA1010 and PA11E was fixed with 60/40 weight fraction. HF was surface-treated by two types of treatment: alkali treatment by NaOH solution and surface treatment by ureido silane coupling agent. The volume fraction of HF in the composites was fixed with 20vol.%. Five different processing sequences: (1) HF, PA1010 and PA11E were mixed simultaneously (Process A), (2) Re-mixing (second compounding) of the materials prepared by Process A (Process AR), (3) PA11...

Thermal properties of hemp fiber filled polyamide 1010 biomass composites and the blend of these composites and polyamide 11 elastomer

The aim of this study is to improve the performance of all inedible plants-derived materials for new engineering materials such as structural materials and tribomaterials. Thermal properties of hemp fiber filled polyamide 1010 biomass composites and the blend of these composites and plants-derived TPE were investigated experimentally. These biomass composites were extruded by a twin screw extruder and compression or injection molded. Thermal properties such as dynamic mechanical analysis (DMA), thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) of these biomass composites were evaluated. It was found that the addition of HF and the blend of bio-TPE with PA1010 have strong influence on the thermal properties such as DMA, TGA and DSC. In particular, HF has a good effect for the improvement of the thermal and mechanical properties. These properties of HF/PA1010/PA11E biomass composites are better than those of HF/PA1010/TPU ones.

Lyapunov-based bilateral teleoperation for surgical robotic forceps system with time varying delay

This paper addresses a new approach of bilateral control for a class of teleoperation systems with time-varying delay and its applications to bilateral teleoperation of robotic surgical device for minimally invasive surgery (MIS). A Lyapunov function-based bilateral control law for one-DOF teleoperation system that is capable of motion scaling in both position and force tracking is proposed so as to guarantee stability of the teleoperation system in the presence of time-varying delay. The proposed bilateral control law is adopted in vertical direction and horizontal direction for bending direction of the multi-DOF robotic forceps, respectively. Then, together with change of coordinates, the proposed bilateral control scheme is extended so that it may become applicable to bilateral control of omnidirectional bending of the multi-DOF robotic forceps manipulator incorporating a new screw-drive mechanism termed double-screw-drive mechanism. Thus, a scalable surgical device for MIS that can provide force feedback to surgeon is presented in this paper. In order to verify the effectiveness of the proposed bilateral control scheme, experimental works were carried out for the developed robotic forceps teleoperation test-bed for MIS.

Lyapunov function based bilateral control for teleoperation system with time varying delay

Recently, robotic surgical support systems are in clinical use for minimally invasive surgery. In order to improve the operability of the robotic surgical systems, development of haptic forceps teleoperation systems is required to help surgeons dexterity. In addition, the motion scaling, which can adequately reduce or enlarge the movements and tactile senses of the operator and the robot, is necessary to assure safety of the surgery. On the other hand, communication time delay is inevitable in teleoperation systems, which may cause instability of the teleoperation systems. Therefore, stability of the system must be guaranteed in the presence of the communication time delay between master device and slave device. We have developed a multi-DOF robotic forceps manipulator using a novel omnidirectional bending mechanism, and for the developed robotic forceps manipulator, we proposed a passivity based bilateral control that enables motion scaling in both position tracking and force tracking, and guarantees the stability of the teleoperation system in the presence of constant time delay, so far. In this paper, the passivity based bilateral control is extended so as to guarantee the stability of the teleoperation system not only in the presence of the constant time delay but also in the presence of the time varying delay.