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In recent years, soft modular robots have become popular among researchers with the development of soft robotics. However, the absence of a visual 3D simulation platform for soft modular robots hold back the development of the field. The three-dimensional simulation platform plays an important role in the field of multi-body robots. It can shorten...
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... manipulation, locomotion, or human assistance/rehabilitation) in different environments (e.g. complex terrain, ferromagnetic walls, or underwater) [13,[16][17][18][19][20][21][22][23][24][25]. Advantages of shape-changing capabilities have been very recently demonstrated through a shape-changing robot that outperformed the non-morphing counterpart in its abilities to traverse flat and inclined terrains [26]. ...
Soft robots have revolutionized machine interactions with humans and the environment to enable safe operations. The fixed morphology of these soft robots dictates their mechanical performance, including strength and stiffness, which limits their task range and applications. Proposed here are modular, reconfigurable soft robots with the capabilities of changing their morphology and adjusting their stiffness to perform versatile object handling and planar or spatial operational tasks. The reconfiguration and tunable interconnectivity between the elemental soft, pneumatically driven actuation units is made possible through integrated permanent magnets with coils (PMC). The proposed concept of attaching/detaching actuators enables these robots to be easily rearranged in various configurations to change the morphology of the system. While the potential for these actuators allows for arbitrary reconfiguration through parallel or serial connection on their four sides, we demonstrate here a configuration called ManusBot. ManusBot is a hand-like structure with digits and palm capable of individual actuation. The capabilities of this system are demonstrated through specific examples of stiffness modulation, variable payload capacity, and structure forming for enhanced and versatile object manipulation and operations. The proposed modular, soft robotic system with interconnecting capabilities significantly expands the versatility of operational tasks as well as the adaptability of handling objects of various shapes, sizes, and weights using a single system.
... Interestingly, in all the three cases, the VSRs were equipped with an RNN operating at f c = 60 Hz: indeed, due to their nature, in which hidden neurons are fed with their activation value at the previous step, RNNs are particularly prone to generate this kind of behavior. However, while in our experiments vibration is effective for locomotion, real VSRs (maybe fabricated with the techniques described in [67,68]) might be unable to perform an effective locomotion just by vibrating. From this point of view, RNNs appear to be more prone to the reality gap problem [69,70] than SNNs and MLPs, when operating at f c = 60 Hz. ...
... In fact, there have been various attempts at building VSRs, starting from that of Hiller and Lipson [4], which initially proposed this type of robots. After this germinal work, several other groups have pursued physical implementations of modular soft robots, as [71,67,68], the most ambitious of them even relying on living matter [72]. However, to this date, none of the existing physical VSRs can be finely controlled with closedloop controllers as in this study, making it still unfeasible to bring this experimentation to the real-world. ...
... By pouring liquid raw materials into specific molds corresponding to the shape of parts and obtaining the part or blank after solidification, casting [80,81] is widely used in the fabrication of various soft robots. The precision of molds, which are often produced by 3D printing, determines the fabrication resolution of the profile since the materials mirror the shape of the molds. ...
... (h) The fabrication process of modular reconfigurable robots. Reproduced with permission[80]. Copyright@2019, The Authors ...
Continuously increasing applications of robot technologies in unstructured environments put higher requirements on the robotic grippers’ performance, such as interaction capability, output force range, and controllability. However, currently, it is hard for either rigid or soft grippers to meet these requirements, as single soft or rigid structures alone are difficult to effectively overcome/alleviate their inherent defects, e.g., low compliance of rigid structures and low output force of soft structures. To deal with these difficulties, soft-rigid coupling grippers, or hybrid grippers are proposed. Technically, the soft-rigid coupling is a promising design that combines soft and rigid structures, in order to exploit their respective advantages, such as the strength of rigid structures and compliance of soft structures, in the same set of the gripper system. For the first time, herein, this paper systematically discusses the collaboration strategies of the existing hybrid robotic grippers, by classifying them as Rigid-Active-Soft-Passive, Rigid-Passive-Soft-Active, and Rigid-Active-Soft-Active. At the same time, we introduce the integrated fabrication methods of hybrid grippers, through which the soft and rigid structures with great stiffness and property differences can be coupled together to construct a stable system. Also, possible performance improvements on soft-rigid coupling design for gripper systems are discussed.
... Nevertheless, the results concerning vibrating individuals call for some further remarks. If we attempted to physically realize those vibrating VSRs, maybe using the approaches of [35,37,73], they would likely not be as fast as in simulation-i.e., there would likely be a reality gap problem [49]. We think that the vibrating behavior evolves frequently for two reasons. ...
In many natural environments, different forms of living organisms successfully accomplish the same task while being diverse in shape and behavior. This biodiversity is what made life capable of adapting to disrupting changes. Being able to reproduce biodiversity in artificial agents, while still optimizing them for a particular task, might increase their applicability to scenarios where human response to unexpected changes is not possible. In this work, we focus on Voxel-based Soft Robots (VSRs), a form of robots that grants great freedom in the design of both morphology and controller and is hence promising in terms of biodiversity. We use evolutionary computation for optimizing, at the same time, morphology and controller of VSRs for the task of locomotion. We investigate experimentally whether three key factors—representation, Evolutionary Algorithm (EA), and environment—impact the emergence of biodiversity and if this occurs at the expense of effectiveness. We devise an automatic machine learning pipeline for systematically characterizing the morphology and behavior of robots resulting from the optimization process. We classify the robots into species and then measure biodiversity in populations of robots evolved in a multitude of conditions resulting from the combination of different morphology representations, controller representations, EAs, and environments. The experimental results suggest that, in general, EA and environment matter more than representation. We also propose a novel EA based on a speciation mechanism that operates on morphology and behavior descriptors and we show that it allows to jointly evolve morphology and controller of effective and diverse VSRs.
... In 2D stacking, actuators are connected to each other in planar structures [17][18][19][20][21][22] . In 3D stacking, actuators are stacked into 3D structures such as brick-piling 23 25 and tensegrity 26 ones. Different stacking mechanisms can also be combined together to create robotic structures with more functions such as '1D+0D' 27,28 , '2D+0D' 29 , '2D+1D' 3,30,31 . ...
Soft robots equipped with multi-functionalities have been increasingly needed for secure, adaptive, and autonomous functioning in unknown and unpredictable environments. Robotic stacking is a promising solution to increase the functional diversity of soft robots which are required for safe human-machine interactions and adapting in unstructured environments. However, most existing multifunctional soft robots have a limited number of functions or have not fully shown the superiority of the robotic stacking method. Here we present a novel robotic stacking strategy, Netting-Rolling-Splicing (NRS) stacking, based on a dimensional raising method via 2D-to-3D rolling-and-splicing of netted stackable pneumatic artificial muscles to quickly and efficiently fabricate multifunctional soft robots based on the same, simple, and cost-effective elements. To demonstrate it, we developed a TriUnit robot that can crawl 0.46 ± 0.022 body length per second and climb 0.11 body length per second, and can carry a 3 kg payload whilst climbing. Also, the TriUnit can be used to achieve novel omni-directional pipe climbing including rotating climbing, and conduct bionic swallowing-and-regurgitating, multi-DOF manipulation based on their multimodal combinations. Apart from these, steady rolling, with a speed of 0.19 body length per second, can be achieved by using a pentagon unit. Furthermore, we applied the TriUnit pipe climbing robot in panoramic shooting and cargo transferring to demonstrate the robot’s adaptability for different tasks. The NRS stacking driven soft robot here has demonstrated the best overall performance amongst existing stackable soft robots, representing a new and effective way for building multifunctional and multimodal soft robots in a cost-effective and efficient way.
... Caterpillar locomotion was a source of inspiration for Zou et al., who developed a reconfigurable modular soft robot with omnidirectional locomotion composed of nine independent pneumatically actuated modules that was controlled via solenoid valves and pressure sensors that set the robot in motion according to the desired configuration [29]. Sui et al. simulated the behavior of a modular robot in VoxCAD software to validate the model and reduce design time, as shown in Figure 3 (b) [30]. Caterpillar locomotion also inspired Li et al., who developed a soft unconnected robot with a dielectric elastomer-based drive that moves at a speed of 100 mm/s [31]. ...
... Mixing polymer material Locomotion [40] FilaFlex -thermoplastic elastomer High elasticity, abrasion resistance, low modulus of elasticity [30] Robot mode Experimental, numerical --- [85] Actuator Analytical, experimental --- [60] Actuator mode Experimental, numerical Diameter 80 mm, length 345 mm -- [89] Actuator Experimental, numerical Length 66.2 mm -- [90] Actuator Experimental, numerical --- [91] Actuator Experimental, numerical Length 100 mm -- [105] Actuator Experimental, numerical Length 940 mm, width 35 mm -- [22] EGaIn Resistance variation by changing the geometry of the microchannels with the elongation of the material Elastomer, eutectic, gallium, indium ...
... (a) Finger actuator structure; reproduced with permission from[28]; published by ELSE-VIER, 2019; (b) modular robot simulated in VoxCAD software[30]. ...
In recent years, soft robotics has developed considerably, especially since the year 2018 when it became a hot field among current research topics. The attention that this field receives from researchers and the public is marked by the substantial increase in both the quantity and the quality of scientific publications. In this review, in order to create a relevant and comprehensive picture of this field both quantitatively and qualitatively, the paper approaches two directions. The first direction is centered on a bibliometric analysis focused on the period 2008–2022 with the exact expression that best characterizes this field, which is “Soft Robotics”, and the data were taken from a series of multidisciplinary databases and a specialized journal. The second direction focuses on the analysis of bibliographic references that were rigorously selected following a clear methodology based on a series of inclusion and exclusion criteria. After the selection of bibliographic sources, 111 papers were part of the final analysis, which have been analyzed in detail considering three different perspectives: one related to the design principle (biologically inspired soft robotics), one related to functionality (closed/open-loop control), and one from a biomedical applications perspective.
... Finally, it is hard to define a design space which takes into account fabrication possibilities, with the risk of optimizing for designs that are not physically plausible. Due to these challenges, successful translation of the computational designs to reality has been limited to few notable cases (Bächer et al., 2021;Bern et al., 2017;Blackiston et al., 2021;Sui et al., 2019). ...
Novel technologies, fabrication methods, controllers and computational methods are rapidly advancing the capabilities of soft robotics. This is creating the need for design techniques and methodologies that are suited for the multi-disciplinary nature of soft robotics. These are needed to provide a formalized and scientific approach to design. In this paper, we formalize the scientific questions driving soft robotic design; what motivates the design of soft robots, and what are the fundamental challenges when designing soft robots? We review current methods and approaches to soft robot design including bio-inspired design, computational design and human-driven design, and highlight the implications that each design methods has on the resulting soft robotic systems. To conclude, we provide an analysis of emerging methods which could assist robot design, and we present a review some of the necessary technologies that may enable these approaches.
... However, the magnets prevent proper expansion of the voxel faces. Sui et al. [17] tackled this limitation by placing the magnets on the edges of the voxels. Magnetically assembled VSRs can be easily reconfigured, however, the complexity of their manufacturing prevents their miniaturization, leading to bulky prototypes [17], [18]. ...
... Sui et al. [17] tackled this limitation by placing the magnets on the edges of the voxels. Magnetically assembled VSRs can be easily reconfigured, however, the complexity of their manufacturing prevents their miniaturization, leading to bulky prototypes [17], [18]. On a more general note, as far as the authors are aware of, all the VSRs prototypes reported in the literature are made of one single material. ...
Voxel-based robots are aggregations of soft and simple building blocks that have been extensively evolved and simulated to perform various tasks, like walking, jumping or swimming. However, real-life voxel-based robots are rather scarce because of their challenging design and assembly. With the current materials and assembling methods, the interfaces between the soft multi-material voxels are prone to failure. This work proposes to make voxels out of reversible Diels-Alder polymers, which are available in a broad range of mechanical properties. By doing so, the covalent bonds at the multi-material interface ensure strong chemical connections, while allowing for reconfiguration. A first voxel-based gripper is thus robustly assembled, then disassembled, using its pieces (voxels) for reassembling another robot, i.e. a voxel-based walking robot. This reconfigurable property allows iterative validation of the simulated voxel-based robots and fine-tuning of the simulations parameters in a sustainable and economical way. Both physical voxel-based robots show similar behaviors as their simulations with root-mean-square errors down to 10.4%.
... Under these premises, there has been a growing body of literature devoted to the topic of modular robotics. Starting from the early theoretical formulations (Neumann & Burks, 1966), the last decades saw many physical realizations being proposed (Howison et al., 2021), including soft ones (Sui et al., 2020). Platforms for the automatic design and manufacture of robots from modular components have also been recently explored (Faiña et al., 2015;Moreno et al., 2018). ...
Modularity is a desirable property for embodied agents, as it could foster their suitability to different domains by disassembling them into transferable modules that can be reassembled differently. We focus on a class of embodied agents known as voxel-based soft robots (VSRs). They are aggregations of elastic blocks of soft material; as such, their morphologies are intrinsically modular. Nevertheless, controllers used until now for VSRs act as abstract, disembodied processing units: Disassembling such controllers for the purpose of module transferability is a challenging problem. Thus, the full potential of modularity for VSRs still remains untapped. In this work, we propose a novel self-organizing, embodied neural controller for VSRs. We optimize it for a given task and morphology by means of evolutionary computation: While evolving, the controller spreads across the VSR morphology in a way that permits emergence of modularity. We experimentally investigate whether such a controller (i) is effective and (ii) allows tuning of its degree of modularity, and with what kind of impact. To this end, we consider the task of locomotion on rugged terrains and evolve controllers for two morphologies. Our experiments confirm that our self-organizing, embodied controller is indeed effective. Moreover, by mimicking the structural modularity observed in biological neural networks, different levels of modularity can be achieved. Our findings suggest that the self-organization of modularity could be the basis for an automatic pipeline for assembling, disassembling, and reassembling embodied agents.
... Modularity in robotic systems takes the form of fabricating physical parts that are interchangeable for a single robot, or designing independent robots that participate in a common task adaptively [18]. Due to the flexibility, versatility, and robustness to changing environmental conditions [72], we are witnessing an increasing number of works on modular robots [29], including soft ones [64]. For example, Kamimura et al. [34] proposed a method to automatically generate locomotion patterns for an arbitrary configuration, and Groß et al. [23] tackled object manipulation and transportation tasks using self-reconfigurable swarm-bots. ...
