Micromanipulation tool replaceable soft actuator with gripping force enhancing and output motion converting mechanisms

Compared with the rigid hand rehabilitation robot, the soft hand rehabilitation robot has the advantages of good flexibility, which is of great significance to its research. In order to make the soft hand rehabilitation robot have the advantages of high stiffness and simple manufacturing process, a nested structure is proposed for finger soft actuator in this paper. The nested structure consists of outer restraint structure and inner core structure. The inner core structure can realize deformation under the action of air pressure. The outer restraint structure can improve bending efficiency by restraining deformation in non-functional direction of inner core structure. On this basis, the processing technology of nested structure is designed, and the effect of structural parameters on performance is analyzed. In order to illustrate the advantages of nested structure, the performance of nested structure and fiber-constrained structure is compared by simulation, which includes bending angle, gripping force and expansion amount (by measuring the deformation of the cross section). The simulation results show the advantages of the nested structure. A prototype of the soft hand rehabilitation robot is developed with nested structure as finger soft actuator, and the experimental results prove the feasibility of design. The results of this study provide a reference for the structure design of soft hand rehabilitation robot.

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Modeling of a Soft-Rigid Gripper Actuated by a Linear-Extension Soft Pneumatic Actuator

Sensors ◽

10.3390/s21020493 ◽

2021 ◽

Vol 21 (2) ◽

pp. 493

Author(s):

Peilin Cheng ◽

Jiangming Jia ◽

Yuze Ye ◽

Chuanyu Wu

Keyword(s):

Relative Error ◽

Linear Extension ◽

Pneumatic Actuator ◽

Soft Robot ◽

Soft Actuator ◽

Soft Objects ◽

Contact Sensing ◽

Gripping Force ◽

The Relationship ◽

Extension Length

Soft robot has been one significant study in recent decades and soft gripper is one of the popular research directions of soft robot. In a static gripping system, excessive gripping force and large deformation are the main reasons for damage of the object during the gripping process. For achieving low-damage gripping to the object in static gripping system, we proposed a soft-rigid gripper actuated by a linear-extension soft pneumatic actuator in this study. The characteristic of the gripper under a no loading state was measured. When the pressure was >70 kPa, there was an approximately linear relation between the pressure and extension length of the soft actuator. To achieve gripping force and fingertip displacement control of the gripper without sensors integrated on the finger, we presented a non-contact sensing method for gripping state estimation. To analyze the gripping force and fingertip displacement, the relationship between the pressure and extension length of the soft actuator in loading state was compared with the relationship under a no-loading state. The experimental results showed that the relative error between the analytical gripping force and the measured gripping force of the gripper was ≤2.1%. The relative error between analytical fingertip displacement and theoretical fingertip displacement of the gripper was ≤7.4%. Furthermore, the low damage gripping to fragile and soft objects in static and dynamic gripping tests showed good performance of the gripper. Overall, the results indicated the potential application of the gripper in pick-and-place operations.

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Design and Fabrication of Pneumatic Soft Gripper

Volume 3: Biomedical and Biotechnology Engineering ◽

10.1115/imece2018-86648 ◽

2018 ◽

Author(s):

Zhonghua Guo ◽

Zhongsheng Sun ◽

Xiaoning Li

Keyword(s):

Compressed Air ◽

Work Piece ◽

Soft Body ◽

Object Shape ◽

Soft Actuator ◽

3D Printed ◽

Experimental Approaches ◽

Different Shapes ◽

The Stability ◽

Gripping Force

In this paper, a pneumatic soft gripper is proposed with inspiration from sea anemone. The gripper is composed of an actuator and several silicone tentacles. With the power of compressed air, the soft actuator expands and folds the tentacles. The gripper wraps tentacles around the object and highly compliant tentacles conforms to the shapes of an object, enveloping and holding it. The physical model is fabricated with 3D printed PLA mold and silicone gel. The gripping mechanics are analyzed according to the experimental gripping operations. On basis of the experimental and analysis result, the compliant gripping is realized while the stability is to be increased. So the tentacle structure is then improved by multi-chamber soft body and vacuum jamming bag. The jamming bag is combined to the end of each tentacle, where the bag is filled with particles to conform to the object shape. Therefore, a reliable constraint is realized between the gripper and the object under vacuum conditions. The bending motion and shaping effect are verified through theoretical and experimental approaches. The important parameters in the vacuum jamming process are also obtained. With such device, soft adaptive bodies enlarges the contact area to adapt to the work-piece where vacuum jamming bags increase the gripping force and stability. It is convenient for universal gripping operation for objects with different shapes.

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Performance study of RTV-2 Silicone Rubber Material For Soft Actuator by Experimental and Numerical methods: The Effect of Inflation Pressure and Wall Thickness

International Journal of Automotive and Mechanical Engineering ◽

10.15282/ijame.17.1.2020.01.0556 ◽

2020 ◽

Vol 17 (1) ◽

pp. 7524-7532 ◽

Cited By ~ 1

Author(s):

Deepak D. ◽

Nitesh Kumar ◽

Shreyas P. Shetty ◽

Saurabh Jain ◽

Manoj Bhat

Keyword(s):

Numerical Methods ◽

Wall Thickness ◽

Silicone Rubber ◽

Inflation Pressure ◽

Performance Study ◽

Rubber Material ◽

Soft Actuator ◽

Alternative Materials ◽

Load Carrying ◽

Influential Parameters

The expensive nature of currently used materials in the soft robotic industry demands the consideration of alternative materials for fabrication. This work investigates the performance of RTV-2 grade silicone rubber for fabrication of a soft actuator. Initially, a cylindrical actuator is fabricated using this material and its performance is experimentally assessed for different pressures. Further, parametric variations of the effect of wall thickness and inflation pressure are studied by numerical methods. Results show that, both wall thickness and inflation pressure are influential parameters which affect the elongation behaviour of the actuator. Thin (1.5 mm) sectioned actuators produced 76.97% more elongation compared to thick sectioned, but the stress induced is 89.61 % higher. Whereas, the thick sectioned actuator (6 mm) showed a higher load transmitting capability. With change in wall thickness from 1.5 mm to 6 mm, the elongation is reduced by 76.97 %, 38.35 %, 21.05 % and 11.43 % at pressure 100 kPa, 75 kPa, 50 kPa and 25 kPa respectively. The induced stress is also found reduced by 89.61 %, 86.66 %, 84.46 % and 68.68 % at these pressures. The average load carrying capacity of the actuator is found to be directly proportional to its wall thickness and inflation pressure.

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Actuation and dynamic mechanical characteristics of a core free flat dielectric electro-active polymer soft actuator

JOURNAL OF MECHANICAL ENGINEERING AND SCIENCES ◽

10.15282/jmes.14.4.2020.08.0582 ◽

2020 ◽

Vol 14 (4) ◽

pp. 7396-7404

Author(s):

Abdul Malek Abdul Wahab ◽

Emiliano Rustighi ◽

Zainudin A.

Keyword(s):

Theoretical Model ◽

Resonance Frequency ◽

Dynamic Testing ◽

Experimental Results ◽

Percentage Error ◽

Initial Tension ◽

Average Percentage ◽

Soft Actuator ◽

Average Percentage Error ◽

Mechanical Dynamics

Various complex shapes of dielectric electro-active polymer (DEAP) actuator have been promoted for several types of applications. In this study, the actuation and mechanical dynamics characteristics of a new core free flat DEAP soft actuator were investigated. This actuator was developed by Danfoss PolyPower. DC voltage of up to 2000 V was supplied for identifying the actuation characteristics of the actuator and compare with the existing formula. The operational frequency of the actuator was determined by dynamic testing. Then, the soft actuator has been modelled as a uniform bar rigidly fixed at one end and attached to mass at another end. Results from the theoretical model were compared with the experimental results. It was found that the deformation of the current actuator was quadratic proportional to the voltage supplied. It was found that experimental results and theory were not in good agreement for low and high voltage with average percentage error are 104% and 20.7%, respectively. The resonance frequency of the actuator was near 14 Hz. Mass of load added, inhomogeneity and initial tension significantly affected the resonance frequency of the soft actuator. The experimental results were consistent with the theoretical model at zero load. However, due to inhomogeneity, the frequency response function’s plot underlines a poor prediction where the theoretical calculation was far from experimental results as values of load increasing with the average percentage error 15.7%. Hence, it shows the proposed analytical procedure not suitable to provide accurate natural frequency for the DEAP soft actuator.

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High-cycle-life and high-loading copolymer network with potential application as a soft actuator

Materials & Design ◽

10.1016/j.matdes.2019.108010 ◽

2019 ◽

Vol 182 ◽

pp. 108010 ◽

Cited By ~ 6

Author(s):

Hafeez Ur Rehman ◽

Yujie Chen ◽

Mikael S. Hedenqvist ◽

Radan Pathan ◽

Hezhou Liu ◽

...

Keyword(s):

Potential Application ◽

Cycle Life ◽

High Loading ◽

Soft Actuator ◽

Copolymer Network

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Sensuator: A Hybrid Sensor–Actuator Approach to Soft Robotic Proprioception Using Recurrent Neural Networks

Actuators ◽

10.3390/act10020030 ◽

2021 ◽

Vol 10 (2) ◽

pp. 30

Author(s):

Pornthep Preechayasomboon ◽

Eric Rombokas

Keyword(s):

Neural Networks ◽

Recurrent Neural Networks ◽

Linear Models ◽

Open Loop ◽

Proof Of Concept ◽

State Estimator ◽

Loop Control ◽

Practical Applications ◽

Soft Actuator ◽

The Cost

Soft robotic actuators are now being used in practical applications; however, they are often limited to open-loop control that relies on the inherent compliance of the actuator. Achieving human-like manipulation and grasping with soft robotic actuators requires at least some form of sensing, which often comes at the cost of complex fabrication and purposefully built sensor structures. In this paper, we utilize the actuating fluid itself as a sensing medium to achieve high-fidelity proprioception in a soft actuator. As our sensors are somewhat unstructured, their readings are difficult to interpret using linear models. We therefore present a proof of concept of a method for deriving the pose of the soft actuator using recurrent neural networks. We present the experimental setup and our learned state estimator to show that our method is viable for achieving proprioception and is also robust to common sensor failures.

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