A soft and dexterous motor (original) (raw)
A Novel Soft Actuator for the Musculoskeletal System
Advanced Materials Technologies, 2018
The musculoskeletal system (MS) is essential for the movements of biological systems. Inspired by this natural structure, several attempts are made to create a synthetic MS. However, one of the challenges in developing an artificial MS for biomimetic robots is the lack of a high‐performance, low‐cost, light‐weight, and compact artificial muscle. In this Communication, a novel twisted and coiled artificial muscle is demonstrated, which is a promising actuator for the development of the artificial MS. The new muscle is made by twisting a nylon 6 fishing line precursor fiber and wrapping with a very thin (80 µm diameter) resistance wire. The resistance wire is not twisted during twist insertion of the polymer, which is very important for the performance of the muscle. The new muscle termed is integrated in a 3D printed ball‐and‐socket‐based artificial MS. Characterization results show a remarkable tensile actuation (53% strain provided at 1.69 MPa for an input current of 0.22 A). Furth...
Elastic Energy Storage Enables Rapid and Programmable Actuation in Soft Machines
Advanced Functional Materials, 2019
Storage of elastic energy is key to increasing the efficiency, speed, and power output of many biological systems. This paper describes a simple design strategy for the rapid fabrication of prestressed soft actuators (PSAs), exploiting elastic energy storage to enhance the capabilities of soft robots. The elastic energy that PSAs store in their prestressed elastomeric layer enables the fabrication of grippers capable of zero-power holding up to 100 times their weight and perching upside down from angles of up to 116°. The direction and magnitude of the force used to prestress the elastomeric layer can be controlled not only to define the final shape of the PSA but also to program its actuation sequence. Additionally, the release of the elastic energy stored by PSAs causes their high-speed recovery (≈50 ms), which significantly improves the actuation rates of soft pneumatic actuators, especially after motions requiring large deformations. Moreover, judicious prestressing of PSAs can also create bistable soft robotic systems, which use their stored elastic energy as a source of power amplification for rapid movements. These strategies serve as a basis for a new class of entirely soft robots capable of recreating bioinspired high-powered and high-speed motions using stored elastic energy.
ArXiv, 2019
Traditional robots have rigid links and structures that limit their ability to interact with the dynamics of their immediate environment. For example, conventional robot manipulators with rigid links can only manipulate objects using specific end effectors. These robots often encounter difficulties operating in unstructured and highly congested environments. A variety of biological organisms exhibit complex movement with soft structures devoid of rigid components. Inspired by biology, researchers have been able to design and build soft robots. With a soft structure and redundant degrees of freedom, these robots can be used for delicate tasks in unstructured environments. This review discusses the motivation for soft robots, their design processes as well as their applications and limitations. Soft robots have the ability to operate in unstructured environment due to their inherent potential to exploit morphological computation to adapt to, and interact with, the world in a way that ...
A Survey on Actuators, Sensors and Control Mechanism Used in Soft Robotics
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.
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.
Toward motor-unit-recruitment actuators for soft robotics
5th IEEE RAS/EMBS International Conference on Biomedical Robotics and Biomechatronics, 2014
Among the many features of muscles, their softness, (the ability to deform to accommodate uncertainty in the environment), and their ability to continue functioning despite disturbances, even partial damage, are qualities one would desire to see in robotic actuators. These properties are intimately related to the manner in which muscles work since they arise from the progressive recruitment of many motor units. This differs greatly from current robotic actuator technologies. We present an actuation platform prototype that can support experimental validation of algorithms for muscle fiber recruitment-inspired control, and where further ways to exploit discretization and redundancy in muscle-like control can be discovered. This platform, like muscles, is composed of discretely activated motor units with an integrated compliant coupling. The modular, cellular structure endows the actuator with good resilience in response to damage. It can also be repaired or modified to accommodate changing requirements in situ rather than replaced. Several performance metrics particular to muscle-like actuators are introduced and calculated for one of these units. The prototype has a blocked force of 2.51 N, a strain rate of 21.1 %, and has an input density of 5.46 ×10 3 motor units per square meter. It consumes 18 W of electrical power during a full isometric contraction. The actuator unit is 41.0 mm 3 in size. The force during isometric contractions as it varies with activation is evaluated experimentally for two configurations of modules.
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.
IEEE Robotics & Automation Magazine, 2000
A fter decades of intensive research, it seems that we are getting closer to the time when robots will finally leave the cages of industrial robotic workcells and start working in the vicinity of and together with humans. This opinion is not only shared by many robotics researchers but also by the leading automotive and IT companies and, of course, by some clear-sighted industrial robot manufacturers. Several technologies required for this new kind of robots reached the necessary level of performance, e.g., computing power, communication technologies, sensors, and electronics integration. However, it is clear that these human-friendly robots will look very different than today's industrial robots. Rich sensory information, lightweight design, and soft-robotic features are required to reach the expected performance and safety during interaction with humans or in unknown environments. In this article, we will present and compare two approaches for reaching the aforementioned soft-robotic features. The first one is the mature technology of torque-controlled lightweight robots (LWRs) developed during the past decade at the German Aerospace Center (DLR) (arms, hands, a humanoid upper body, and a crawler). Several products resulted from this research and are currently being commercialized through cooperations with different industrial partners (DLR-KUKA LWR, DLR-HIT-Schunk hand, DLR-Brainlab medical robot). The second technology, still a topic of worldwide ongoing research, is variable compliance actuation that implements the soft-robotic features mainly in hardware.
Advanced Materials Technologies, 2021
Compared with traditional rigid robotic manipulators, [8] these soft counterparts are more compliant, more adaptable, and easier to control, thereby more suitable for safe machine-human and machine-environment interactions, such as grasping fragile objects, picking apples, and assisting elderly people and children. Moreover, soft manipulators are unique for physical and distributed computations through their compliance feature, reducing the needs for sophisticated algorithms and mechanisms in planning and control for real-world applications. The inherent compliant feature of the soft robots, on the other hand, poses critical challenges for achieving high structural stability and high loading capacity for specific applications, such as manipulation of heavy objects [9] and surgical operations. [10] To overcome this, one potential solution is to tune the stiffness of soft robots so that they can sustain external loads (including self-weight) or exert large forces for robust interactions when needed. A variety of methodologies and materials have been proposed to adjust the stiffness of soft materials and structures, including electrorheological (ER) and magnetorheological (MR) fluids, [11] particle jamming, [12] thermoplastics, [13] shape memory polymers (SMPs), [14] and low melting point alloys (LMPAs). [15] However, ER/MR fluids generally have limitations of requiring proper leakproof packaging. Although particle jamming is a fast-responsive method for stiffness change, it requires a bulky setup for pumping and vacuum operations. The application of SMP is somewhat difficult for soft robots due to its high modulus in the martensite phase. Thermoplastic materials are based on localized heating to change stiffness, which is difficult for large area/volume materials as they would need many heating elements and complicated control designs. Compared to SMPs and thermoplastics, LMPAs can provide a large stiffness difference between solid and liquid states via Joule heating. Furthermore, self-healing can be intrinsically realized by the recrystallization of alloys. [15] Therefore, LMPA is a promising candidate for achieving stiffness variation for soft robotics applications. For many applications involving hazardous or dangerous environments (e.g., factory workspace or deep ocean), remote control of robots (including soft manipulators [16]) is desired. Human-machine interface (HMI) can achieve two-way information transmission between human and machines and has Soft robots have attracted great attention in the past decades owing to their unique flexibility and adaptability for accomplishing tasks via simple control strategies, as well as their inherent safety for interactions with humans and environments. Here, a soft robotic manipulation system capable of stiffness variation and dexterous operations through a remotely controlled manner is reported. The smart manipulation system consists of a soft omnidirectional arm, a dexterous multimaterial gripper, and a self-powered human-machine interface (HMI) for teleoperation. The cable-driven soft arm is made of soft elastomers and embedded with low melting point alloy as a stiffness-tuning mechanism. The self-powered HMI patches are designed based on the triboelectric nanogenerator that utilizes a sliding mode of tribo-layers made of copper and polytetrafluoroethylene. The novel soft manipulation system has great potential for soft and remote manipulation and human machine interactions in a variety of applications from elderly care to surgical operation to agriculture harvesting.