Review of soft fluidic actuators: classification and materials modeling analysis (original) (raw)
Related papers
HFAM: Soft Hydraulic Filament Artificial Muscles for Flexible Robotic Applications
IEEE Access, 2020
The use of soft artificial muscles (SAMs) is rapidly increasing in various domains such as haptics, robotics, and medicine. There is a huge need for a SAM that is highly compliant and facile to fabricate with performance characteristics similar to human muscles. This paper introduces bio-inspired soft hydraulic filament artificial muscles (HFAMs) that can be extended and contracted under fluid pressures. The HFAMs, which have a high aspect ratio of at least 5000, use a simple and low-cost fabrication method of insertion, enabling scalability and mass-production while increasing its generated force via a stiff constrained helical layer and an adjustable stretch ratio of their inner silicone microtube. The developed muscles can produce a high elongation of 246.8% and a high energy efficiency of 62.7%. In addition, the HFAMs can generate a higher contraction force compared to existing state-of-the-art devices via their constrained hollow layer and the adjustable stretch ratio of the inner microtube, enabling a tunable force capability. Experiments are carried out to validate the HFAM performance including durability, lifting, frequency response and energy efficiency tests. The HFAM capabilities are demonstrated via various experiments, offering a potential substitute for the conventional tendon-driven mechanisms with less friction loss and stable energy efficiency while working against long and tortuous paths. A HFAMs-driven soft exoskeleton glove that could assist in grasping multiple objects is developed and evaluated. The new muscles open great opportunities for research and commercial sectors including emerging applications such as soft wearable devices and flexible surgical robots. INDEX TERMS Fluid-driven artificial muscles, soft actuators, soft exoskeletons, soft robotics, tendon-driven mechanisms, wearable devices.
A Systematic Overview of Soft Actuators for Robotics
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...
An Overview of Novel Actuators for Soft Robotics
Actuators
In this systematic survey, an overview of non-conventional actuators particularly used in soft-robotics is presented. The review is performed by using well-defined performance criteria with a direction to identify the exemplary and potential applications. In addition to this, initial guidelines to compare the performance and applicability of these novel actuators are provided. The meta-analysis is restricted to five main types of actuators: shape memory alloys (SMAs), fluidic elastomer actuators (FEAs), shape morphing polymers (SMPs), dielectric electro-activated polymers (DEAPs), and magnetic/electro-magnetic actuators (E/MAs). In exploring and comparing the capabilities of these actuators, the focus was on eight different aspects: compliance, topology-geometry, scalability-complexity, energy efficiency, operation range, modality, controllability, and technological readiness level (TRL). The overview presented here provides a state-of-the-art summary of the advancements and can hel...
Bioinspired design and fabrication principles of reliable fluidic soft actuation modules
2015 IEEE International Conference on Robotics and Biomimetics (ROBIO), 2015
A large percentage of the field of robotics is devoted to catching up to what nature can already do. Taking inspiration from the snake and the jumping spider, we describe advances towards standardized modular multi-material composite soft pneumatic actuator design and fabrication. Previous pneumatic bi-directional bending actuators used in our soft robotic snake suffered from repeatability challenges and were prone to bursting in the seams. Here, we present a standardized fabrication method of soft pneumatic actuators to reduce the seams and incorporate a more reliable port for the input pressure. In addition, we explore the integration of our flexible curvature sensor, allowing for less invasive proprioceptive sensing of the actuator state. Finally, taking inspiration from jumping spider legs we also propose a plastic exoskeleton system, which can guide soft actuators to form complex shapes when pressurized. We show that all of these actuators were consistent and reliable over numerous trials. The next step is to combine these individual actuators into their respective bioinspired robotic systems: a soft modular snake and a soft jumping spider.
IEEE Access
Soft robotics is a rapidly evolving field where robots are fabricated using highly deformable materials and usually follow a bioinspired design. Their high dexterity and safety make them ideal for applications such as gripping, locomotion, and biomedical devices, where the environment is highly dynamic and sensitive to physical interaction. Pneumatic actuation remains the dominant technology in soft robotics due to its low cost and mass, fast response time, and easy implementation. Given the significant number of publications in soft robotics over recent years, newcomers and even established researchers may have difficulty assessing the state of the art. To address this issue, this article summarizes the development of soft pneumatic actuators and robots up until the The scope of this article includes the design, modeling, fabrication, actuation, characterization, sensing, control, and applications of soft robotic devices. In addition to a historical overview, there is a special emphasis on recent advances such as novel designs, differential simulators, analytical and numerical modeling methods, topology optimization, data-driven modeling and control methods, hardware control boards, and nonlinear estimation and control techniques. Finally, the capabilities and limitations of soft pneumatic actuators and robots are discussed and directions for future research are identified. INDEX TERMS Soft robotics, soft pneumatic actuator, design, modeling, sensing, control. MATHEUS S. XAVIER (Graduate Student Member, IEEE) received the B.S. degree in science and technology and the B.Eng. degree in control and automation engineering from the Federal
Bioinspired Soft Actuation System Using Shape Memory Alloys
Soft robotics requires technologies that are capable of generating forces even though the bodies are composed of very light, flexible and soft elements. A soft actuation mechanism was developed in this work, taking inspiration from the arm of the Octopus vulgaris, specifically from the muscular hydrostat which represents its constitutive muscular structure. On the basis of the authors' previous works on shape memory alloy (SMA) springs used as soft actuators, a specific arrangement of such SMA springs is presented, which is combined with a flexible braided sleeve featuring a conical shape and a motor-driven cable. This robot arm is able to perform tasks in water such as grasping, multi-bending gestures, shortening and elongation along its longitudinal axis. The whole structure of the arm is described in detail and experimental results on workspace, bending and grasping capabilities and generated forces are presented. Moreover, this paper demonstrates that it is possible to realize a self-contained octopus-like robotic arm with no rigid parts, highly adaptable and suitable to be mounted on underwater vehicles. Its softness allows interaction with all types of objects with very low risks of damage and limited safety issues, while at the same time producing relatively high forces when necessary.
Tendon-based stiffening for a pneumatically actuated soft manipulator
— There is an emerging trend towards soft robotics due to its extended manipulation capabilities compared to traditionally rigid robot links, showing promise for an extended applicability to new areas. However, as a result of the inherent property of soft robotics being less rigid, the ability to control/obtain higher overall stiffness when required is yet to be further explored. In this paper, an innovative design is introduced which allows varying the stiffness of a continuum silicon-based manipulator and proves to have potential for applications in Minimally Invasive Surgery. Inspired by muscular structures occurring in animals such as the octopus, we propose a hybrid and inherently antagonstic actuation scheme. In particular, the octopus makes use of this principle activating two sets of muscles-longitudinal and transverse muscles-thus, being capable of controlling the stiffness of parts of its arm in an antagonistic fashion. Our designed manipulator is pneumatically actuated employing chambers embedded within the robot's silicone structure. Tendons incorporated in the structure complement the pneumatic actuation placed inside the manipulator's wall to allow variation of overall stiffness. Experiments are carried out by applying an external force in different configurations while changing the stiffness by means of the two actuation mechanisms. Our test results show that dual, antagonistic actuation increases the load bearing capabilities for soft continuum manipulators and thus their range of applications.
Long Shape Memory Alloy Tendon-based Soft Robotic Actuators and Implementation as a Soft Gripper
Shape memory alloy (SMA) wire-based soft actuators have had their performance limited by the small stroke of the SMA wire embedded within the polymeric matrix. this intrinsically links the bending angle and bending force in a way that made SMA-based soft grippers have relatively poor performance versus other types of soft actuators. in this work, the use of free-sliding SMA wires as tendons for soft actuation is presented that enables large increases in the bending angle and bending force of the actuator by decoupling the length of the matrix and the length of the SMA wires while also allowing for the compact packaging of the driving SMA wires. Bending angles of 400° and tip forces of 0.89 N were achieved by the actuators in this work using a tendon length up to 350 mm. The tendons were integrated as a compact module using bearings that enables the actuator to easily be implemented in various soft gripper configurations. Three fingers were used either in an antagonistic configuration or in a triangular configuration and the gripper was shown to be capable of gripping a wide range of objects weighing up to 1.5 kg and was easily installed on a robotic arm. The maximum pulling force of the gripper was measured to be 30 N.
Advanced Engineering Materials, 2017
The emerging field of soft robotics makes use of many classes of materials including metals, low glass transition temperature (Tg) plastics, and high Tg elastomers. Dependent on the specific design, all of these materials may result in extrinsically soft robots. Organic elastomers, however, have elastic moduli ranging from tens of megapascals down to kilopascals; robots composed of such materials are intrinsically soft − they are always compliant independent of their shape. This class of soft machines has been used to reduce control complexity and manufacturing cost of robots, while enabling sophisticated and novel functionalities often in direct contact with humans. This review focuses on a particular type of intrinsically soft, elastomeric robot − those powered via fluidic pressurization.
Highly Dynamic Shape Memory Alloy Actuator for Fast Moving Soft Robots
Advanced Materials Technologies, 2019
However, soft robot locomotion tends to be relatively slow and typically relies on external hardware for power and control. This is largely due to current limitations with the "artificial muscle" actuators that are used to place the battery-powered electrical motors (e.g., DC motors, servos) that have been traditionally used in robotics. For example, untethered soft robots that use fluidic or dielectric elastomer actuators require bulky on-board hardware for power and control that result in a high payload and slow locomotion speed. [3,8,9] While ionic polymer-metal composites require low voltage and can be controlled using miniaturized electronics, they have not been shown to generate the forces required for a cm-scale robot to walk in dry conditions. [10,11] By contrast, soft robot actuators composed of elastomers embedded with wires or springs of thermally activated smart materials such as shape memory alloy (SMA) can generate large forces in an adequately short time interval and be directly powered and controlled with portable, lightweight electronics. [12] Moreover, they can reversibly transition from being mechanically compliant in their natural (unactuated) state to being stiff and load-bearing when actuated. [12] Although promising, SMAs have only been used as actuators for untethered soft robot in a limited number of cases. [13,14] A key challenge has been the limited frequency with which SMA-based actuators can be activated. This is due to the long duration of time required for the alloy to cool down and return to its natural shape and compliance following electrical activation. As a result, soft robots powered with SMA actuators either have sudden but infrequent bursts of motion, [14] slow steady-state locomotion gait cycles with long recovery times, [15] tethered hardware [15] or take advantage of marine environments for active cooling. [13,16] In this work, we address this challenge by examining how materials selection, actuator design, and operating conditions can be used to improve the frequency bandwidth of an SMA actuator. In particular, we find that encasing SMA wire in thermally conductive rubber can allow for more rapid heat transfer and enable soft robots to exhibit robust dynamical motion over extended operating times (Figure 1a). The SMA actuator is capable of a rapid transition