Soft Actuators

In this systematic survey, an overview of non-conventional and soft-actuators is presented. The review is performed by using well-defined performance criteria with a direction to identify the exemplary applications in robotics. In addition to this, initial guidelines to measure the performance and applicability of soft actuators are provided. The meta-analysis is restricted to four main types of soft actuators: shape memory alloys (SMA), fluidic elastomer actuators (FEA), dielectric electro-activated polymers (DEAP) and shape morphing polymers (SMP). In exploring and comparing the capabilities of these actuators, the focus was on seven different aspects: compliance, topology, scalability-complexity, energy efficiency, operation range, performance and technological readiness level. The overview presented here provides a state-of-the-art summary of the advancements and can help researchers to select the most convenient soft actuators using the comprehensive comparison of the performan...

2020

In these previous years, it has been reported that machinery has caused injuries and deaths in the industries. Machineries consist of moving mechanical parts that are mostly actuated by hard conventional actuators. Using conventional actuators could result in injuries, leading to complications during human robot interaction. Due to their hard physical features, it is difficult to implement conventional actuators in various environments except in industry. Due to such difficulties, these issues are mitigated by introducing soft actuators. Soft actuators are built out of soft materials similar to silicon and are actuated when air pressure is introduced as well as on inflating the internal fluidic channel. This results in the soft actuator to create a bending motion. Such types of actuators include a broad range of application; however, the issue here would be to control the bending motion pertaining to the soft actuator, and thus this warrants an analysis for such types of actuators. ...

Smart Materials and Structures, 2021

Soft actuators can be classified into five categories: tendon-driven actuators, electroactive polymers, shape-memory materials, soft fluidic actuators (SFAs), and hybrid actuators. The characteristics and potential challenges of each class are explained at the beginning of this review. Furthermore, recent advances especially focusing on SFAs are illustrated. There are already some impressive SFA designs to be found in the literature, constituting a fundamental basis for design and inspiration. The goal of this review is to address the latest innovative designs for SFAs and their challenges and improvements with respect to previous generations, and to help researchers to select appropriate materials for their application. We suggest seven influential designs: pneumatic artificial muscle, PneuNet, continuum arm, universal granular gripper, origami soft structure, vacuum-actuated muscle-inspired pneumatic, and hydraulically amplified self-healing electrostatic. The hybrid design of SFA...

Engineer: Journal of the Institution of Engineers, Sri Lanka, 2020

Communication delay between robotic control systems and the robotic actuator is a major issue since the soft robotic motion requires controls to be precise and have quick responses. This is also essential for real time control of robots where the user should be able to send and receive signals with minimum delay to emulate a real time control. Specifically, in soft robotics , the communication delay could become a bigger issue due to the fact that soft robots require mode of pressure exerted into the actuator to make any kind of motion. A delay in such instances could cause the whole system to malfunction and even could cause the actuator to explode in the case of rapid and subtle changes in internally applied pressure. In this research, available IoT (Internet of Things) related systems and models have been studied and suitable IoT system was designed. The main focus of this research was to study the communication delay in IoT embedded hand gesture controlled soft robot finger (actuator). Two separate data processing units have been introduced in the master side and in the slave side to rapid capturing and sending data. By using this approach , processing delay is expected to be minimized. Transmission delay, propagation delay and queuing delay are found to be handled through external factors. These factors could be changed by using various kinds of servers and service providers. Soft elastomer actuator was designed and developed using standard rapid prototyping and soft lithography techniques generally used in soft robotics. Testing, data collecting and analyzing the system are carried out at various locations in Sri lanka and finally the Round Trip Delay Time (RTD) for each case was compared.

2017 IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS), 2017

The constantly increasing amount of machines operating in the vicinity of humans makes it necessary to rethink the design approach for such machines to ensure that they are safe when interacting with humans. Traditional mechanisms are rigid and heavy and as such considered unsuitable, even dangerous when a controlled physical contact with humans is desired. A huge improvement in terms of safe human-robot interaction has been achieved by a radically new approach to robotics-soft material robotics. These new robots are made of compliant materials that render them safe when compared to the conventional rigid-link robots. This undeniable advantage of compliance and softness is paired with a number of drawbacks. One of them is that a complex and sophisticated controller is required to move a soft robot into the desired positions or along a desired trajectory, especially with external forces being present. In this paper we propose an improved soft fluidic rotary actuator composed of silicone rubber and fiber-based reinforcement. The actuator is cheap and easily manufactured providing near linear actuation properties when compared to pneumatic actuators presented elsewhere. The paper presents the actuator design, manufacturing process and a mathematical model of the actuator behavior as well as an experimental validation of the model. Four different actuator types are compared including a square-shaped and three differently reinforced cylindrical actuators.

Advanced materials and technologies, 2018

In addition, large mechanical power output, good tensile actuation, and dynamic response are essential requirements for this application. Twisted and coiled polymer (TCP) muscle from fishing line emerged as a promising actuator as shown in Haines et al.; [6] it can deliver a large strain of 49%, lift loads over 100 times heavier than those lifted by a human muscle of the same length and weight, generate 5.3 kW of mechanical work per kilogram of muscle weight, and undergo over 1 million life cycles. The fundamental mechanism in twisted and coiled actuator is the thermally induced fiber untwist in the coiled structure, which allows for both torsional and tensile actuation. [7,8] TCP muscle from fishing line can be actuated via hydrothermal actuation, but Joule heating is a convenient method because it eliminates a complicated actuator system like hot water reservoir and fluid pump needed for hydro

Advanced Intelligent Systems, 2020

Soft robotics has experienced an exponential growth in publications in the last two decades. [1] Unlike rigid conventional manipulators, [2,3] soft robots based on hydrogels, [4,5] electroactive polymers, [6,7] and elastomers [7-9] are physically resilient and can adapt to delicate objects and environments due to their conformal deformation. [10,11] They also show increased safety and dexterity can be lightweight and used within constrained environments with restricted access. [12,13] Many soft robots have a biologically inspired design coming from snakes, [14-17] worms, [18-20] fishes, [21-24] manta rays, [25,26] and tentacles. [27-29] The scope of applications includes minimally invasive surgery, [30,31] rehabilitation, [32,33] elderly assistance, [34] safe human-robot interaction, [35,36] and handling of fragile materials. [37,38] Important features of soft robotics design, fabrication, modeling, and control are covered in the soft robotics toolkit. [39,40] The building blocks of soft robots are the soft actuators. The most popular category of soft actuator is the soft fluidic actuator (SFA), where actuation is achieved using hydraulics or pneumatics. [8,41] These actuators are usually fabricated with silicone rubbers following a 3D molding process, [42] although directly 3D printing the soft actuators is also possible. [43,44] Silicone rubber is a highly flexible/extensible elastomer with high-temperature resistance, lowtemperature flexibility, and good biocompatibility. [45] Elastomers can withstand very large strains over 500% with no permanent deformation or fracture. [46] For relatively small strains, simple linear stress-strain relationships can be used, and two of the following parameters can be used to describe the elastic properties: bulk compressibility, shear modulus, tensile modulus (Young's modulus of elasticity), or Poisson's ratio. [45] For large deformations, nonlinear solid mechanic models using hyperelasticity should be considered. [8,32,47-50] Due to the strong nonlinearities in SFAs and their complex geometries, analytical modeling is challenging. [51] A brief review of the analytical methods for modeling of soft robotic structures is provided in the following. 1.1. Analytical Modeling of Soft Actuators The majority of soft/continuum robots with bending motion can be approximated as a series of mutually tangent constant curvature sections, i.e., piecewise constant curvature. [52] This is a result of the fact that the internal potential energy is uniformly distributed along each section for pressure-driven robots. [53] This approach has also been validated using Hamilton's principle by Gravagne et al. [54] As discussed by Webster and Jones, [52] the kinematics of continuum robots can be separated into robotspecific and robot-independent components in this approach. The robot specific mapping transforms the input pressures P or actuator space q to the configuration space κ, ϕ, l, and the robot-independent mapping goes from the configuration space to the task space x. The actuator space contains the length of tubes or bellows. The configuration space consists of the curvature κ, the angle of the plane containing the arc ϕ (also called

A proposed adaptive soft orthotic device performs motion sensing and production of assistive forces with a modular, pneumatically-driven, hyper-elastic composite. Wrapping the material around a joint will allow simultaneous motion sensing and active force response through shape and rigidity control. This monolithic elastomer sheet contains a series of miniaturized pneumatically-powered McKibben-type actuators that exert tension and enable adaptive rigidity control. The elastomer is embedded with conductive liquid channels that detect strain and bending deformations induced by the pneumatic actuators. In addition, the proposed system is modular and can be configured for a diverse range of motor tasks, joints, and human subjects. This modular functionality is accomplished with a decentralized network of self-configuring nodes that manage the collection of sensory data and the delivery of actuator feedback commands. This paper mainly describes the design of the soft orthotic device as well as actuator and sensor components. The characterization of the individual sensors, actuators, and the integrated device is also presented.

Actuators

This article presents the development of a self-bending contraction actuator (SBCA) through the analysis of its structure, kinematics, and torque formulas, and then explores its applications. The proposed actuator has been fabricated by two methods to prove the efficiency of the human body inspiration, which represents the covering of human bones by soft tissues to protect the bone and give the soft texture. The SBCA provides bending behaviour along with a high force-to-weight ratio. As with the simple pneumatic muscle actuator (PMA), the SBCA is soft and easy to implement. Both the kinematics and the torque formula presented for the SBCA are scalable and can be used with different actuator sizes. The bending actuator has been tested under an air pressure of up to 500 kPa, and the behaviour of its bending angle, parameters, dimensions, and the bending torques have been illustrated. On the other hand, the experiments showed the efficient performances of the actuator and validate the ...

INTERVIEWS IN APPLIED LINGUISTICS Autobiographical Reflections on Research Processes, 2024

The introduction aims to set up this book as an autobiographical reflection on research interviews. First, it outlines chapter content and situates this book with regard to previous publications on research interviews. Second, it deals with additional matters such as the book’s status as a type of narrative – autobiography – and what this entails; how the book is not just about research interviews and includes discussions of the theoretical and practical background to individual research projects; the multiple styles in which the book is written; the transcription conventions used for interview excerpts presented and finally, some terminological issues.