To realize an extremely safe robot, an exoskeleton inflatable robotic arm with thin McKibben muscles and simple driving systems installed inside the arm, except for air-supply devices, was designed and manufactured using soft materials. McKibben muscles, which are considerably thin, lightweight, flexible, and can be mass produced, are suitable for this soft robotic mechanism. The arm is safe and useful for human-friendly robots owing to its softness, low weight, and compliance. The exoskeleton inflatable robotic arm was modeled, theoretical equations were derived for the joint angle and torque, and theoretical and experimental results obtained at various structural stiffness were compared. In the experiments, the developed arm could bend at 90° and 91° on each side. Furthermore, it was proposed that experimental values can be estimated using theoretical expressions with correction factors.
Flexible/stretchable sensors comprising soft structures that do not interfere with the softness of the bodies of soft robots are essential for achieving soft robots with superior operational performance. These sensors are expected to be applicable as sensing skin for humanoid robots and as interfaces for human-robot interactions. Herein, we refer to flexible/stretchable sensors investigated for soft robotics applications as “soft sensors” and review recent research trends. Specifically, we discuss optical, resistive, capacitive, and inductive soft sensors with emphasis on their materials and structures.
A flexible microactuator with 3 degrees of freedom has been developed for Micromanipulators. It is made of fiber reinforced rubber and its deformation is controlled by an electrohydraulic or - pneumatic system. This report deals with its static characteristics. First, theoretical characteristic equations are derived based on the infinitesimal deformation theory. They are useful for practical design applications due to their simple forms. Secondly, the FEM is applied to the nonlinear analysis of large deformation. The calculated results are compared to the experimental data of the prototype (outerdiameter: 12 mm, length: 50 mm). As a result, while the theoretical characteristic equations are effective for predicting small deformation, the numerical method is for both small and large deformations.
Hydraulic artificial muscles are so flexible and light in weight for robots and generate very high force by oil hydraulic pressure. In addition, these muscles can be placed and twisted freely. In this paper, we propose 3 DoF wrist mechanism that is compact, frexible and light in weight by hydraulic artifical muscles.
One of the most important missions for robots is to operate in severe environments, and these situations require robots to have 'toughness' which can overcome large shocks, degraded communication quality, unexpected condition, and other critical accidents. Although there are many kinds of approaches to realize tough robotic systems, developing a tough actuators is one of the key technologies for them. We focus on hydraulic actuators and attempt to develop a tough robotic actuator with greater toughness than the electromagnetic actuators used in conventional robotic systems. In general, hydraulic actuators have enough toughness for severe environments, but their controllability and lightness are insufficient for robot systems. Herein, we propose novel hydraulic actuators that realizes lightweight with a multidirectional-forging magnesium alloy and have high controllability by low friction pistons. Prototypes were developed to examine the fundamental characteristics of the actuators and compare the two approaches for the low-friction pistons: one is based on a packing mechanism using an elastic restoring pressure, and the other utilizes a fluid-bearing technology. After basic experiments, the prototype was applied to a robotic leg to verify their potential in actual robotic systems. The robotic leg successfully jumped 260 mm in height with 21 MPa.
The vehicle using omnidirectional wheels has ability to move in all directions without changing the body direction unlike a normal four-wheel-drive vehicle, so it can go in narrow space and realize speedup of the work because it can move laterally. But the Mecanum Wheel as an example of omnidirectional wheel is unsuitable for rough terrain now. In this paper, we designed the new Mecanum Wheel which has spiral structure. Rollers are attached to wheel's circumference helically. When the vehicle with this spiral Mecanum Wheel moves laterally, the tip of the parts forming the spiral is rotated as to cover from above the step. We have performed the experiment using the prototype of spiral Mecanum Wheel and verified its performance.
Recently, micro reactors have been developed in chemical engineering. The goal of this research is to develop devices to promote chemical reactions physically by shaking catalytic particles in liquid. While catalytic particles were driven in gas by electrostatic force in previous research, they can't be driven in liquid. To increase driving force and to drive catalytic particles in liquid, driving method was changed from electrostatic drive to electromagnetic drive. Magnetic field condition was analyzed by FEM and the device was designed based on it. Using the prototype device makes catalytic particles driven both in gas and liquid. The effectiveness in liquid chemistry of the device was shown with the experiments of stirring marbling solutions in water.
Ionic polymer-metal composites (IPMC) actuators are popular because they can be driven at a low voltage, possess excellent responsiveness, and can perform soft motions similar to that of living creatures. Conventional IPMC soft robots are manufactured by cutting and assembling IPMC sheets. However, using this conventional process to stably manufacture three-dimensional (3D)-shaped soft robots is difficult. To mitigate this problem, we propose a new method for fabricating 3D IPMC actuators in which several surface electrodes are separately fabricated from a single ion-exchange membrane. We refer to our proposal as the simultaneous 3D forming and patterning (SFP) method. Unlike the conventional IPMC fabrication process, the SFP method requires only one step to fix the ion-exchange membrane to contact masks. First, we briefly describe IPMC actuators, before introducing the proposed SFP method in detail. Next, we describe our investigations of the patterning resolution for the surface electrode using the proposed method. We fabricated two soft robot prototypes using the proposed method. The first robot is a starfish-type soft robot. Its surface electrode can be patterned in a plane using the proposed method, and independent driving is possible by applying voltage individually to the divided electrodes. The second prototype is a sea anemone-type soft robot, wherein surface electrodes can be patterned on a 3D curved surface to form a 3D shape.
Currently, synthetic fiber ropes which have high strength while being lightweight, are applied to tendon-driven robots. In our previous works, it is clarified that a rope using UHMWPE has higher strength and repetitive bending durability than not only stainless steel wire rope but also other synthetic fiber ropes. However, there are also some types of UHMWPE fiber, and some rope are heat-set and others are not. In this paper, we focus on repetitive bending durability of heat-set ropes. As a result, a heat-set or densely rope of UHMWPE has high strength. Moreover, the higher strength a rope has, the lower bending durability the rope has.
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