Actuation of untethered pneumatic artificial muscles and soft robots using magnetically induced liquid-to-gas phase transitions

2020 ◽  
Vol 5 (41) ◽  
pp. eaaz4239 ◽  
Author(s):  
Seyed M. Mirvakili ◽  
Douglas Sim ◽  
Ian W. Hunter ◽  
Robert Langer
Keyword(s):  
Phase Transition ◽  
Gas Phase ◽  
High Performance ◽  
Artificial Muscle ◽  
Artificial Muscles ◽  
Peak Strain ◽  
Soft Robots ◽  
Robotic Arms ◽  
Actuation Mechanism ◽  
Pneumatic Artificial Muscles

Pneumatic artificial muscles have been widely used in industry because of their simple and relatively high-performance design. The emerging field of soft robotics has also been using pneumatic actuation mechanisms since its formation. However, these actuators/soft robots often require bulky peripheral components to operate. Here, we report a simple mechanism and design for actuating pneumatic artificial muscles and soft robotic grippers without the use of compressors, valves, or pressurized gas tanks. The actuation mechanism involves a magnetically induced liquid-to-gas phase transition of a liquid that assists the formation of pressure inside the artificial muscle. The volumetric expansion in the liquid-to-gas phase transition develops sufficient pressure inside the muscle for mechanical operations. We integrated this actuation mechanism into a McKibben-type artificial muscle and soft robotic arms. The untethered McKibben artificial muscle generated actuation strains of up to 20% (in 10 seconds) with associated work density of 40 kilojoules/meter3, which favorably compares with the peak strain and peak energy density of skeletal muscle. The untethered soft robotic arms demonstrated lifting objects with an input energy supply from only two Li-ion batteries.

scholarly journals A Multistate Friction Model for the Compensation of the Asymmetric Hysteresis in the Mechanical Response of Pneumatic Artificial Muscles

Actuators ◽  
2019 ◽  
Vol 8 (2) ◽  
pp. 49 ◽  
Author(s):  
Alessia Capace ◽  
Carlo Cosentino ◽  
Francesco Amato ◽  
Alessio Merola
Keyword(s):  
Tracking Control ◽  
Mechanical Response ◽  
Control Strategies ◽  
Friction Model ◽  
Assistive Robotics ◽  
Surgical Instruments ◽  
Artificial Muscles ◽  
Soft Robots ◽  
Pneumatic Artificial Muscles ◽  
Compliant Actuators

These days, biomimetic and compliant actuators have been made available to the main applications of rehabilitation and assistive robotics. In this context, the interaction control of soft robots, mechatronic surgical instruments and robotic prostheses can be improved through the adoption of pneumatic artificial muscles (PAMs), a class of compliant actuators that exhibit some similarities with the structure and function of biological muscles. Together with the advantage of implementing adaptive compliance control laws, the nonlinear and hysteretic force/length characteristics of PAMs pose some challenges in the design and implementation of tracking control strategies. This paper presents a parsimonious and accurate model of the asymmetric hysteresis observed in the force response of PAMs. The model has been validated through the experimental identification of the mechanical response of a small-sized PAM where the asymmetric effects of hysteresis are more evident. Both the experimental results and a comparison with other dynamic friction models show that the proposed model could be useful to implement efficient compensation strategies for the tracking control of soft robots.

scholarly journals Design and Control of a 1-DOF Robotic Lower-Limb System Driven by Novel Single Pneumatic Artificial Muscle

2019 ◽  
Vol 10 (1) ◽  
pp. 43 ◽  
Author(s):  
Tsung-Chin Tsai ◽  
Mao-Hsiung Chiang
Keyword(s):  
Lower Limb ◽  
Artificial Muscle ◽  
Robotic System ◽  
Artificial Muscles ◽  
Prototype System ◽  
Pneumatic Artificial Muscle ◽  
Torsion Spring ◽  
Pneumatic Artificial Muscles ◽  
Control Response ◽  
Spring Mechanism

This study determines the practicality and feasibility of the application of pneumatic artificial muscles (PAMs) in a pneumatic therapy robotic system. The novel mechanism consists of a single actuated pneumatic artificial muscle (single-PAM) robotic lower limb that is driven by only one PAM combined with a torsion spring. Unlike most of previous studies, which used dual-actuated pneumatic artificial muscles (dual-PAMs) to drive joints, this design aims to develop a novel single-PAM for a one degree-of-freedom (1-DOF) robotic lower-limb system with the advantage of a mechanism for developing a multi-axial therapy robotic system. The lower limb robotic assisting system uses the stretching/contraction characteristics of a single-PAM and the torsion spring designed by the mechanism to realize joint position control. The joint is driven by a single-PAM controlled by a proportional pressure valve, a designed 1-DOF lower-limb robotic system, and an experimental prototype system similar to human lower limbs are established. However, the non-linear behavior, high hysteresis, low damping and time-variant characteristics for a PAM with a torsion spring still limits its controllability. In order to control the system, a fuzzy sliding mode controller (FSMC) is used to control the path tracking for the PAM for the first time. This control method prevents approximation errors, disturbances, un-modeled dynamics and ensures positioning performance for the whole system. Consequently, from the various experimental results, the control response designed by the joint torsion spring mechanism can also obtain the control response like the design of the double-PAMs mechanism, which proves that the innovative single-PAM with torsion spring mechanism design in this study can reduce the size of the overall aid mechanism and reduce the manufacturing cost, can also improve the portability and convenience required for the wearable accessory, and is more suitable for the portable rehabilitation aid system architecture.

Contractile Pneumatic Artificial Muscle Configured to Generate Extension

2014 ◽  
Vol 136 (3) ◽  
Author(s):  
Benjamin K. S. Woods ◽  
Shane M. Boyer ◽  
Erica G. Hocking ◽  
Norman M. Wereley ◽  
Curt S. Kothera
Keyword(s):  
Compressive Loading ◽  
Compressive Force ◽  
Artificial Muscle ◽  
Specific Power ◽  
Artificial Muscles ◽  
Specific Work ◽  
Operational Characteristics ◽  
Pneumatic Artificial Muscles ◽  
High Specific Power ◽  
Internal Mechanism

Pneumatic artificial muscles (PAMs) are comprised of an elastomeric bladder surrounded by a braided mesh sleeve. When the bladder is inflated, the actuator may either contract or extend axially, with the direction of motion dependent on the orientation of the fibers in the braided sleeve. Contractile PAMs have excellent actuation characteristics, including high specific power, specific work, and power density. Unfortunately, extensile PAMs exhibit much reduced blocked force, and are prone to buckling under axial compressive loading. For applications in which extensile motion and compressive force are desired, the push-PAM actuator introduced here exploits the operational characteristics of a contractile PAM, but changes the direction of motion and force by employing a simple internal mechanism using no gears or pulleys. Quasi-static behavior of the push-PAM was compared to a contractile PAM for a range of operating pressures. Based on these data, the push-PAM actuator can achieve force and stroke comparable to a contractile PAM tested under the same conditions.

scholarly journals Modeling and Simulation of Robotic Finger Powered by Nylon Artificial Muscles

2019 ◽  
Vol 12 (1) ◽  
Author(s):  
Lokesh Saharan ◽  
Lianjun Wu ◽  
Yonas Tadesse
Keyword(s):  
High Performance ◽  
Electrical Power ◽  
Simulated Data ◽  
Artificial Muscle ◽  
Power Input ◽  
Artificial Muscles ◽  
Robotic Hand ◽  
Finger Motion ◽  
Angular Displacements ◽  
Measured Input

Abstract A robotic finger actuated by novel artificial muscles known as twisted and coiled polymer (TCP) muscles has been proposed as an inexpensive, yet high-performance component of a robotic hand in recent years. In this paper, the Euler–Lagrangian method coupled with an electro-thermo-mechanical model-based transfer function was used for the analysis of finger joints in the hand. Experiments were performed at three power magnitudes provided to the TCP muscles, and the output angular displacements of the index finger subtended corresponding to the power levels were measured. The measured input and output parameters were used for system identification. To elucidate how the new artificial muscle influences the finger motion, two types of numerical simulations were performed: force input simulation (FIS) using measured force as an input and power input simulation (PIS) using measured electrical power as an input. Results were quantified statistically, and the simulated data were compared with the experimental results. Sensitivity analysis was also presented to understand the effect of the mechanical properties on the system. This model will help in understanding the effect of the TCP muscles and other similar smart actuators on the dynamics of the robotic finger.

The Effects of Nylon Polymer Threads on Strain-Loading Hysteresis Behavior of Supercoiled Polymer (SCP) Artificial Muscles

2019 ◽  
Author(s):  
Revanth Konda ◽  
Jun Zhang
Keyword(s):  
Thermal Activation ◽  
Experimental Validation ◽  
Linear Models ◽  
Artificial Muscle ◽  
Power Input ◽  
Artificial Muscles ◽  
Helical Spring ◽  
Spring Model ◽  
Actuation Mechanism ◽  
Proposed Model

Abstract Supercoiled polymers (SCP) actuator, as a recently discovered artificial muscle, has attracted a lot of attention as a compliant and compact actuation mechanism. SCP actuators can be fabricated from nylon polymer threads, and generates up to 20% strain under thermal activation. A common challenge, however, is to accurately and efficiently estimate the performance of SCP actuators considering their significant hysteresis among loading, strain, and power input. Previous studies adopted either linear models that failed to capture the hysteresis or phenomenological models that required tedious procedures for identification and implementation. In this paper, a physics-inspired model is presented to efficiently capture and estimate SCP actuators’ strain – loading hysteresis by analyzing the properties of nylon threads from which they are fabricated. The strains of SCP actuators are found to be linear to that of the nylon threads under the same loading conditions. An efficient approach is proposed to characterize and estimate the strain – loading hysteresis of SCP actuators fabricated with different numbers of nylon threads. A helical spring model is adopted to obtain the stiffness of SCP actuators with different configurations. Experimental validation involving two-ply, four-ply, and six-ply nylon threads and SCP actuators are provided to confirm the effectiveness of the proposed model.

Modeling, Analysis, and Function Extension of the McKibben Hydraulic Artificial Muscles

2020 ◽  
Author(s):  
Siqing Chen ◽  
He Xu
Keyword(s):  
High Pressure ◽  
Theoretical Analysis ◽  
Artificial Muscle ◽  
Design Parameters ◽  
Artificial Muscles ◽  
Soft Robots ◽  
The Law ◽  
Soft Actuators ◽  
The Impact ◽  
The Relationship

Abstract Compared with rigid robots, flexible robots have soft and extensible bodies enforcing their abilities to absorb shock and vibration, hence reducing the impact of probable collisions. Due to their high adaptability and minimally invasive features, soft robots are used in various fields. The McKibben hydraulic artificial muscles are the most popular soft actuator because of the controllability of hydraulic actuator and high force to weight ratio. When its deformation reaches a certain level, the actuators can be stopped automatically without any other braking mechanism. The research of McKibben hydraulic artificial muscles is beneficial to the theoretical analysis of soft actuators in the mechanical system. The design of soft actuators with different deformations promotes the development of soft robots. In this paper, a static modeling of the McKibben hydraulic artificial muscles is established, and its correctness is verified by theoretical analysis and experiment. In this model, the deformation mechanism of the artificial muscle and the law of output force is put forward. The relationship between muscle pressure, load, deformation, and muscle design parameters is presented through the mechanical analysis of the braid, elastic tube, and sealed-end. The law of the muscle deformation with high pressure is predicted. The reason for the muscle’s tiny elongation with extremely high pressure is found through the analysis of the relationship between the angle of the braid, the length of single braided thread, and the pressure. With the increase of pressure, the angle of the braid tends to a fixed value. As the stress of braided thread increases, so does its length. The length changes obviously when the stress is extremely enormous. The angle of the braid and the length of the braided thread control the deformation of artificial muscles, resulting in a slight lengthening with extreme high pressure. Under normal pressure, the length of the braided wire is negligible, so that the entire muscle becomes shorter. According to the modeling and theoretical analysis, a new McKibben hydraulic artificial muscle that can elongate under normal rising pressure is designed. This artificial muscle can grow longer with pressure increases, eventually reaching its maximum length. During this time, its diameter barely changes. Its access pressure is higher than that of conventional elongated artificial muscles. Through experiments, the relationship between the muscle deformation, pressure, and load still conform to this theoretical model. This model can be used for the control of soft actuators and the design of new soft robots. This extensional McKibben hydraulic artificial muscles and the conventional McKibben hydraulic artificial muscles can be used in the bilateral control of soft robots.

Development of a new system for reducing the temperature increase during the positioning of spoilers using pneumatic artificial muscle (PAM)

2020 ◽  
Vol 92 (8) ◽  
pp. 1257-1261
Author(s):  
Mustafa Soylak ◽  
Mustafa Bakır
Keyword(s):  
Temperature Increase ◽  
Low Cost ◽  
Artificial Muscle ◽  
Artificial Muscles ◽  
Content Type ◽  
Air Inlet ◽  
Thermal Changes ◽  
Pneumatic Artificial Muscles ◽  
Regional Temperature ◽  
Control Surfaces

Purpose The usage of pneumatic artificial muscles (PAMs) is becoming increasingly widespread across a variety of industries because of its advantages such as its lightness and its ability to generate a huge amount of force using the fewest components. The purpose of this paper is to develop a piece of hardware to minimize and equally distribute the thermal changes on the surface of a PAM when positioning using PAMs. A classic PAM and a PAM that contains the hardware suggested for tasks, such as the positioning of spoilers decelerating control surfaces for aircrafts, were compared experimentally. Design/methodology/approach Rapid thermal changes were detected in the classic PAM, especially at the tip of the PAM. These thermal changes decrease the positioning sensitivity and reliability, thus shortening life span of the PAMs. A component was developed that could create a circulation of air around the tip of the PAM, preventing the temperature increase caused by still air. It is installed inside the PAM and makes it possible to control the pressurized air volume in crucial areas. Shaped as a perforated metal pipe, the component was embedded inside the PAM and effects of this component were investigated. Findings The experiment results have shown that, thanks to the system that was developed, cool air that comes from outside is able to reach the tip of the PAM every time, thus keeping regional temperature increase to a minimum. The temperature increase in the pressurized air inlet was minimized by creating a circulation of air in the area. Originality/value With this study, the distribution of heat in different areas on PAM was homogenized at a low cost using the component that was developed.

Flexible Sensor for McKibben Pneumatic Artificial Muscle Actuator

2009 ◽  
Vol 3 (6) ◽  
pp. 731-740 ◽  
Author(s):  
Shinji Kuriyama ◽  
◽  
Ming Ding ◽  
Yuichi Kurita ◽  
Jun Ueda ◽  
...  
Keyword(s):  
Artificial Muscle ◽  
The Elderly ◽  
Axial Displacement ◽  
Artificial Muscles ◽  
Pneumatic Artificial Muscle ◽  
Flexible Sensor ◽  
Pneumatic Artificial Muscles ◽  
Circumferential Displacement ◽  
Mckibben Actuators ◽  
Power Assistance

The demand for flexible, lightweight McKibben pneumatic artificial muscles (McKibben actuators) has been increasing for power assistance equipment used for assisting and rehabilitating the elderly. To accurately control this equipment, the length of the actuator should be measured. However, the equipment becomes heavier and less flexible when a rigid sensor, such as a potentiometer or an encoder, is used. The sensor should be flexible in order to take advantage of the favorable properties of the McKibben actuator. The aim of this study is to measure the length of the actuator without loss of its advantages. We propose a method of estimating the length from the circumferential displacement, which can be measured by a sensor made of electroconductive, flexible rubber. Higher accuracy is obtained by measuring the circumferential displacement than by measuring the axial displacement using this sensor. The sensor’s flexibility enables us to accurately control the actuator without any loss of flexibility or increase in weight. Furthermore, the sensor does not require the attachment of any rigid fixtures. The accuracy of the estimate is successfully evaluated and the usefulness of the proposed method is verified through its application to a multi-link arm driven by the McKibben actuator.

Development of Semi-Crouching Assistive Device Using Pneumatic Artificial Muscle

2020 ◽  
Vol 32 (5) ◽  
pp. 885-893
Author(s):  
Naoki Saito ◽  
Daisuke Furukawa ◽  
Toshiyuki Satoh ◽  
Norihiko Saga ◽  
◽  
...  
Keyword(s):  
Weight Ratio ◽  
Artificial Muscle ◽  
Assistive Device ◽  
Artificial Muscles ◽  
Pneumatic Artificial Muscle ◽  
Contraction Force ◽  
Lower Back ◽  
Pneumatic Artificial Muscles ◽  
Compressive Pressure ◽  
Analytical Result

This paper describes a semi-crouching assistive device using pneumatic artificial muscles. The goal of this device is to reduce the load on the lower back when performing work in the semi-crouching position. The load on the lower back is reduced by decreasing the compressive pressure on the lumbar disk of the lower back. This compressive pressure increases as the contraction force of the erector spine increases. Therefore, it is important to reduce the muscle activity of the erector spine. Based on the analytical result of a worker’s position model, the proposed device adopts a scheme to push the chest of the user as an appropriate assistive method. Additionally, the analytical result shows that a reduction in weight of the device is also important for decreasing the load on the lower back. Based on these results, we prototyped a lightweight semi-crouching assistive device that can generate sufficient assistive force via a pneumatic artificial muscle, which has high power to weight ratio. This device was experimentally evaluated via electromyogram of the erector spine when the user maintains a semi-crouching position. The experimental results confirmed the usefulness of this device.

Operating Modes of Pneumatic Artificial Muscle Actuator

2013 ◽  
Vol 308 ◽  
pp. 39-44 ◽  
Author(s):  
Mária Tóthová ◽  
Ján Piteľ ◽  
Jana Boržíková
Keyword(s):  
Position Control ◽  
Artificial Muscle ◽  
Pneumatic Actuator ◽  
Variable Pressure ◽  
Artificial Muscles ◽  
Pneumatic Artificial Muscle ◽  
Operating Modes ◽  
Main Requirement ◽  
Pneumatic Artificial Muscles ◽  
Operation Characteristics

The paper describes operating modes of the PAM based actuator consisting of two pneumatic artificial muscles (PAMs) in antagonistic connection. The artificial muscles are acting against themselves and resultant position of the actuator is given by equilibrium of their forces according to different pressures in muscles. The main requirement for operation of such pneumatic actuator is uniform movement and accurate arm position control according to input desired variable. There are described in paper operation characteristics of the pneumatic artificial muscle in variable pressure and then operation characteristics of the pneumatic artificial muscle actuator consisting of two muscles in antagonistic connection.

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