Search

This paper presents a motion sensor-based haptic master controller capable of static and dynamic force presentation by the newly invented Finger Band Soft Actuator (FBSA). The master controller operates a surgical assist robot using the $ 6 $ 6 degrees of freedom position and posture data tracked by an optical motion capture. The haptic force presentation can be realized by the pneumatic pressure of FBSA, which can be highly integrated into the controller mechanism to maintain precise manipulability. The FBSA can present a pressing force of 3.7 N for a small-sized finger and 5.1 N for a large-sized finger at an internal pressure of 60 kPa, and there is a monotonically increasing and decreasing relationship between the air pressure and the pressing force. The effectiveness of haptic force presentation by the FBSA was experimentally evaluated in the master-follower operation of a surgical assist robot. Ten subjects performed the task of pulling a suture thread and controlled the manipulation to achieve the directed tension. The experimental result shows that with the four levels of force presentation scheme by the FBSA, the error between suture tension and target operating force is significantly smaller than without force presentation. [ABSTRACT FROM AUTHOR]

Soft actuators have attracted a lot of attention because of their impressive performance and wide range of applications. Liquid crystalline networks (LCNs) are a combination of liquid crystals and polymers, and they are considered to be the most promising materials for creating soft actuators. MXene has a high photothermal conversion efficiency, and it can be a heat-source under near-infrared light. In this paper, we fabricated a MXene/LCN composite film by coating a solution of Ti3C2Tx MXene onto an LCN film with orientation direction and then followed by drying. We observed different types of deformations when we cut the composite film in different directions. We also measured the influence of the near-infrared light intensity on the bending angle, response time, and recovery time of the composite films with different deformations. Finally, we used this composite film to fabricate various biomimetic devices such as biomimetic flowers, artificial irises, mechanical fixtures, and crawling robots. These results demonstrate the great potential of this composite film in soft actuator applications. [ABSTRACT FROM AUTHOR]

A gecko foot-inspired, mushroom-shaped artificial dry adhesive exploiting intermolecular forces between microstructure and surface has drawn research attention for its strong adhesive force. However, the high pull-off strength corresponding to the adhesive force matters when detaching fragile substrates. In this study, we report a vacuum-powered soft actuator having oblique air chambers and a dry adhesive. The soft actuator performs coupled contraction and twisting by applying negative pneumatic pressure inward and exhibits not only high pull-off strength but also easy detachment. This effective detachment can be achieved thanks to the twisting motion of the soft actuator. The detachment performances of the actuator models are assessed using a 6-degrees-of-freedom robot arm. Results show that the soft actuators exhibit remarkable pull-off strength decrement from ~20 N cm−2 to ~2 N cm−2 due to the twisting. Finally, to verify a feasible application of this study, we utilize the inherent compliance of the actuators and introduce a glass transfer system for which a glass substrate on a slope is gripped by the flexibility of the soft actuators and delivered to the destination without any fracture. Vacuum-powered soft actuator with oblique air chambers for easy detachment of artificial dry adhesive by coupled contraction and twisting In this work, we report a vacuum-powered soft actuator with artificial dry adhesive. We used a vacuum for the easy detachment of the dry adhesive and verified a feasibility for the real-industrial fields. The highlights and novelty of this work are as follows: • Vacuum-powered soft actuator with Gecko inspired dry adhesive • High adhesion with an easy detachment by twisting motion • Mechanical analysis of the easy detachment • Novel glass transfer system with the 6-DOF robot arm based on the soft actuator [ABSTRACT FROM AUTHOR]

Abstract Soft actuators with embedded fluidic channels are promising for soft robotics, but their continuous nature presents challenges in accurate and efficient modeling. Existing studies on dynamic behavior have shown that both approximate and exact methods have limitations in accurately predicting the deflection of soft actuators. Additionally, conventional methods require experimental parameter extraction for each individual actuator. To address these challenges, we propose a modified analytical method and use finite element analysis as the defined correction functions to improve accuracy and computational efficiency, providing a promising tool for the design and control of soft robotic systems. In this work, we propose a solution methodology for simulating the dynamic behavior of fluidic soft actuators, which are widely used in soft robotics applications. Our approach takes into account the cross-sectional geometry and the number of channels in the actuator’s configuration. By scrutinizing various fluidic actuation designs, we can deduce the most suitable cross-sectional configuration for optimal performance. Compared to existing analytical methods, our approach is more accurate and does not require additional calculation time. As the method is adaptable with experimental models, it can be used to design and optimize soft actuators while can be refined and improved through experimental model updating. [ABSTRACT FROM AUTHOR]

Pneumatic artificial muscles have some advantages. Especially, the flexibility of artificial muscles contributes to compose novel mechanisms. Authors succeeded in manufacturing novel soft mechanisms that are composed of only woven artificial muscles and strings. We called this mechanism active textile. The structure is uniformed with woven artificial muscles; nevertheless, the forms and movements of mechanisms are diverse. We aim to establish a design method for these active textiles. We reported that deformations of active textiles are changed by woven structures. In addition to that, wefts' characteristics such as cross-sectional shape, bending stiffness and elasticity determine the characteristic of a textile. Deformations of active textiles are caused by the contraction and the expansion of thin McKibben muscles. In this paper, authors focus on the contraction and curvature deformation of the active textile due to the drive of the artificial muscles.We fabricated active textiles with different wefts and different weave structures.Contraction and bending deformations of active textiles in the warp and weft directions are assumed geometrically. In addition, we verified the validity by experiments. [ABSTRACT FROM AUTHOR]

Actuators with clutch mechanisms have advantages in safety, backdriveability, and controllability for human-coexistence robots. This paper presents a large force actuator using electro-adhesive gels, which are functional materials controlled by the magnitude of an electric field. The developed actuator can generate and continuously control a force over 560 N and resist with a small force when de-energized. The number of electro-adhesive gel disks is drastically increased to increase the generative force. This paper reports the structural plan for the new actuator and experiments to investigate its basic characteristics. Based on the experimental results, an actuator model is identified for the future design of its control system. This paper contributes to the development of a clutch-type linear actuator with a large generative force, maintaining safety and a high force-to-weight ratio. It also addresses the problem of high-voltage power supply costs for electro-rheological and electro-adhesive materials. [ABSTRACT FROM AUTHOR]

In this manuscript, we describe a photo-responsive dual-layer polysiloxane-based liquid crystal elastomer (LCE) soft actuator with switchable handedness of helical curling motions. Benefited from the embedded organic near-infrared (NIR) absorbing dye, the LCE ribbon can perform an impressive one-handed helical curling deformation under NIR light irradiation, meanwhile execute another-handed helical curling deformation under ultraviolet (UV) light irradiation due to the trans-cis isomerisation effect of azobenzene. This work demonstrates that the handedness of helical curling motions of LCE soft actuators can be reversibly altered by modulating the wavelength band of light stimuli (UV vs. NIR), which might have potential applications in control devices. [ABSTRACT FROM AUTHOR]

Composite systems of liquid crystals (LCs) and polymers have been extensively studied in various forms such as polymer-dispersed LCs and polymer-stabilised LCs. Blending LCs and polymers is an effective approach to design functional materials with stimuli responsiveness and durability. Here, we show the development of a novel composite material with crosslinked azobenzene LC polymer (PAzo) and poly (dimethylsiloxane) (PDMS) aiming at the improvement of photomobile polymer materials in mechanical properties. The composite films were prepared by photopolymerisation of azobenzene monomers in PDMS elastomers. By forming phase separated structure, in which PAzo chains were dispersed in PDMS matrix, fracture strain of photomobile polymer materials was significantly enhanced. The composite film showed macroscopic bending upon irradiation with UV light. This result implies that PAzo domains in polymer matrix can work as microactuators to afford macroscopic deformation of the whole film. The further improvement of this system in photomechanical properties would be feasible through adequate control of composition and the alignment of mesogens. [ABSTRACT FROM AUTHOR]

Many soft actuators have been studied for use in robots that come into contact with humans, including communication, entertainment, and medical/health care robots. One reason for this is that soft robots are expected to exhibit intrinsic safety in case an accident occurs. This paper proposes a plastic-film pneumatic actuator with a pleated structure that do not undergo the elastic deformation typical of rubber materials. By utilizing thin plastic films, the mass of an actuator can be significantly reduced, even if the actuators are the same size as a human arm. If the mass of the actuator is reduced, the kinetic energy when contacts with humans mechanically can be reduced considerably without reducing the working speed. More specifically, we propose a pleated structure made of plastic to achieve structural deformation generated from a two-dimensional pleated film. The pleated structure easily generates various bending motions. In this paper, a design method for determining the shape parameters of the pleated actuator structure using approximate models with considering measurement results of generating force is presented. We evaluated the adequacy of our approach in experiments using sample actuators. Furthermore, we show the constraints required to determine the necessary parameters. Thus, this paper provides an easy method for designing a lightweight and flexible plastic-film actuator. [ABSTRACT FROM AUTHOR]

Polypyrrole (PPy) actuators, which expand and contract by doping and dedoping ions in an electrolyte solution, have been reported to have a large strain under a large stress. However, many of these actuators exhibited notable electrochemical creep (swelling) after repeated electrochemical actuations. Here, actuator films were prepared by electrochemical polymerization of pyrrole and diethyl 3,4-pyrroledicarboxylate with different mol ratios. The actuating strain of the film actuators prepared from a solution of pyrrole and diethyl 3,4-pyrroledicarboxylate with 97:3 mol ratio showed significant reduction of the electrochemical creep with minimal reduction of the actuating strain. [ABSTRACT FROM PUBLISHER]

An electro-conjugate fluid (ECF) is a kind of functional fluid, which produces a jet flow (ECF jet) when subjected to high DC voltage. It is known that a strong ECF jet is generated under a non-uniform electric field (e.g., a field with a pair of needle and ring electrodes (a needle–ring electrode pair)). This study introduces the ECF jet to develop a novel flexible robot finger. First, we propose a concept for a novel robot finger. The robot finger mainly consists of a bending actuator, an ECF tank and ECF jet generators, which could be a micro fluid pressure source of the robot finger. Second, we characterize each component of the robot finger (i.e., the bending actuator and the ECF jet generator). We investigate the influences of electrode parameters on ECF jet generator performance in order to design the finger prototype. Finally we clarify the characteristics of the robot finger. The length, the diameter and the mass of the robot finger are 34.2 mm, 12 mm and 3.8 g, respectively. The robot finger can generate a force of 0.28 N and bend approximately 70°. [ABSTRACT FROM PUBLISHER]

Soft actuators driven by pneumatic pressure are promising actuators for mechanical systems in medical, biological, agriculture, welfare fields and so on, because they can ensure high safety for fragile objects from their low mechanical impedance. In this study, a new rubber pneumatic actuator made from silicone rubber was developed. Composed of one chamber and one air-supply tube, it can generate curling motion in two directions by using positive and negative pneumatic pressure. The rubber actuator, for generating bidirectional motion, was designed to achieve an efficient shape by nonlinear finite element method analysis, and was fabricated by a molding and rubber bonding process using excimer light. The fabricated actuator was able to generate curling motion in two directions successfully. The displacement and force characteristics of the actuator were measured by using a motion capture system and a load cell. As an example application of the actuator, a robotic soft hand with three actuators was constructed and its effectiveness was confirmed by experiments. [ABSTRACT FROM AUTHOR]

In recent years, Japanese society has been aging, creating a shortage of young workers. Robots are expected to be useful to perform tasks such as rehabilitation therapy, nursing elderly people and day-to-day work support for elderly people. In particular, robots that are designed for use in the fields of medical care and welfare must be safe for the human environment because they often come into contact with humans. Furthermore, robots must have dexterity that is similar to that of humans. Under these circumstances, tendon-driven systems of two types using flexible silicone rubber materials have been developed. They are lightweight and have characteristics resembling those of human muscle. This paper describes the basic features and mechanisms of two tendon-driven systems that we have developed as a soft actuator. Furthermore, basic properties of the system are evaluated and compared with those of human muscles. [ABSTRACT FROM AUTHOR]

It has been previously reported that dynamic behaviours of polypyrrole (PPy) soft actuators were improved when they were driven in aqueous solutions of an electrolyte, lithium bis(trifluoromethanesulphonyl)imide (LiTFSI) containing an optimised amount of 2-propanol. In this work, the influences of the potential sweep rate on electrochemical and creep strains of PPy actuators in aqueous LiTFSI electrolyte solutions with 2-propanol concentrations of 0 and 20% were investigated under the load stress of 0.3 MPa. The electrochemical strain rates in the 0% and 20% 2-propanol solution were found to be approximately 0.1% s-1 and 0.25% s-1, respectively, and they are nearly independent of the sweep rate between 10 and 25 mV s-1. These results suggest that TFSI anion penetration into the PPy films might be limited by the interactions between the PPy surface and the TFSI anions. The creep rate was more rapidly increased as time elapsed in the electrolyte solution containing 2-propanol than that in the electrolyte solution without 2-propanol, which was due to the swelling of PPy film in the electrolyte. [ABSTRACT FROM AUTHOR]

An electro-conjugate fluid (ECF) is a type of dielectric and functional fluid that generates a powerful jet flow when subjected to high DC voltage. Although a high voltage is needed to generate the jet flow, the current is quite low at several microamperes, resulting in a total power consumption of several milliwatts. Using this smart fluid, we can develop micro fluid-driven mechanical components without any bulky pumps. Also, it is clarified that the power density of the ECF jet is higher when the electrode pair is miniaturized; therefore, it is suitable for micro actuators. Here, we propose and fabricate three types of soft actuators with an antagonistic configuration: (i) micro artificial muscle cells, (ii) a McKibben-type micro artificial muscle actuator using the ECF effect and (iii) a micro finger actuator with two chambers to bend. The actuators basically consist of a silicone rubber tube covered with a fiber sleeve and a micro pressure source using the ECF effect. Next, we apply and integrate these actuators into a micro robot hand, driven with ECF jets. The driving characteristics of the micro artificial muscle actuator and the integrated micro ECF hand with ECF fingers were fabricated and experimentally investigated. The experimental results show that this ECF jet actuation is effective for driving soft micro hands. [ABSTRACT FROM AUTHOR]

Robots manipulated by humans are being aggressively researched and developed. Such robots have requirements such as a large generative force, high-speed response, good controllability, high safety, low friction and backdriveability. We focused on backdriveability and created a prototype for a novel linear actuator with a new structure that includes an electrorheological (ER) gel, which is a recently designed functional material. The device is an all-purpose actuator that satisfies the demands for application in a human-coexistence welfare robot, such as power-assist systems. This paper presents the original plan for the linear actuator, shows the actuator as currently manufactured and presents the basic characteristics of the actuator as investigated experimentally. We obtained larger force from the linear actuator than the initial target. Additionally, the linear actuator shows possibilities of further improvement of the force-weight ratio by an increase of the ER gel structures. With regard to stabilizing the response of the linear actuator, spring elements contributed to its improvement. However, further stabilization remains as a future issue for practical use in human-coexistence robots. [ABSTRACT FROM AUTHOR]

A bucky gel actuator is a novel electro-active polymer (EAP), which is a low-voltage-driven dry soft actuator. In addition, the bucky gel device generates electromotive force when bending and then it can also be used as a sensor. Its device has a bimorph structure with polymer-supported bucky gel electrodes and a polymer-supported ionic gel electrolyte. It can be fabricated by layer-by-layer casting to easily form any shape. In this paper, we demonstrate an automatic fabrication method of bucky gel devices based on a printing method. By using a dispensing machine, we construct the printing system and the manual forming process is replaced with automatic printing. We investigate the printing of complicated shapes and three-dimensional electrode patterns through experiments. [ABSTRACT FROM AUTHOR]

Poly(N-isopropylacrylamide) (PNIPA) gel containing polymer surfactant poly(2-(methacryloyloxyl)decylphosphate) (PMDP) was synthesized and was found to show rapid volume phase transition above its transition temperature. Interestingly, the phase transition temperature of the PNIPA–PMDP gel was equal to that of the PNIPA gels alone. The concentration gradient of PMDP within the PNIPA gel can be obtained by applying an electric field on the gel, similar to the gel electrophoretic technique. The PMDP-gradient PNIPA gel clearly demonstrated the prevention of skin formation and the acceleration of the phase transition rate of the PNIPA gel by PMDP. The rapid volume phase transition allows potential applications of the PNPA–PMDP gel to soft actuators and drug delivery systems. Recently we also succeeded in synthesizing cylindrical microgels (0.8 μm in diameter, 5 μm in length) by a novel strategy where template-guiding synthesis and photochemical polymerization are combined. The obtained microgels can be characterized in individual level by a laser-trapping/Raman spectroscopy. In this article we also briefly described a famous gel system containing ionic surfactant capable of electrically driven actuators although it is not PNIPA gel. [ABSTRACT FROM AUTHOR]

Actuators are one of important electromechanical components in order to establish functional mechatronics systems. Particularly, in micro systems like pipe traveling micro machines, it is required to develop powerful micro actuators for realizing practical applications. Fluid power system has a potential to develop active and functional components in the field of micro machines. From the view point of the powerful micro actuators for advanced micro fluid control systems, we have developed advanced fluid control elements like micro valves, micro motors and micro pumps are developed by using functional fluids like ERF, MRF and ECF in our laboratory. These functional components developed in our laboratory, particularly ECF applications, are briefly reported. An electro-conjugate fluid (ECF) is a kind of dielectric fluid, which works as a functional fluid. The fluid generates a powerful jet flow, which we call an ECF jet, when applied to high DC voltage with a highly nonuniform electric field. In other words, the ECF-jet utilizes as a fluid power source for mechanical components without any sizable pumps. [ABSTRACT FROM AUTHOR]

We are studying the robotic application of ionic polymer–metal composite (IPMC). The characteristics of IPMC greatly depend on the type of counterions, and it is considered that the performance of the actuators can be improved by combining the actuators with several types of counterions and applying an integrated control. IPMC also has a sensor function, as the IPMC film generates an electromotive force when it is deformed. It has the possibility to be integrated into an IPMC actuator with soft actuation. In this paper, we consider an integrated design of an IPMC actuator/sensor, and investigate control of the combined IPMC actuators using H∞ control and the construction of an IPMC sensor system. [ABSTRACT FROM AUTHOR]

We are developing an artificial muscle linear actuator using ionic polymer-metal composites (IPMC)—electro-active polymers that bend in response to electric stimuli—and the goal of our study is applying the actuator to robotic applications, especially to a biped walking robot. In this paper, we will describe the structure of the actuator and an empirical model of the actuator which has two inputs and one output, and whose parameters are identified from input-output data. Based on the empirical model, basic experiments and position control of the linear actuator are demonstrated. Then, we consider walking control of a small-sized biped walking robot. In the application we assume that the developed actuators are connected both in series and in parallel to a joint of the walking robot so that the actuators supply enough torque to the robot, and that they are stretched and compressed enough. It is shown throughout simulations that the biped walking robot with the actuators can walk on level ground with a period synchronized with the period of the input signal. [ABSTRACT FROM AUTHOR]