A Novel Variable Stiffness Compliant Robotic Gripper Based on Layer Jamming

2019 ◽  
Author(s):  
Yuan Gao ◽  
Xiguang Huang ◽  
Ishan Singh Mann ◽  
Hai-Jun Su
Keyword(s):  
Load Capacity ◽  
Variable Stiffness ◽  
Fold Increase ◽  
Structural Stiffness ◽  
Working Process ◽  
Shape Morphing ◽  
Individual Finger ◽  
Low Load ◽  
3D Printed ◽  
Stiffness Variation

Abstract In this paper, we present a novel compliant robotic gripper with three variable stiffness fingers. While the shape morphing of the grippers is cable-driven, the stiffness variation is enabled by layer jamming. The inherent flexibility makes compliant grippers suitable for tasks such as grasping soft and irregular objects. However, their relatively low load capacity due to low structural stiffness limits their applications. Variable stiffness robotic grippers have the potential to address this challenge as their stiffness can be tuned on demand based on the needs of tasks. Layer jamming is an emerging method for variable stiffness due to its advantages of light weight, simple and quick actuation. In our design, the compliant backbone of the fingers is made of 3d printed PLA material. Four thin film materials are attached to each side of the skeleton. The working process of the robotic gripper follows two basic steps. First, the compliant skeleton is bent to a desired shape by actuating a tension cable via a servo motor. Second, upon application of a negative pressure by a vacuum pump, the finger is stiffened up owing to the increasing of the friction between contact surfaces of layers preventing their relative movement. Since the structural stiffness of the fingers is increased, their load capacity will be increased proportionally. When the air pressure is sufficiently large, the morphed shape can even be locked (no slipping). Test for stiffness of individual finger and load capacity of the robotic gripper are conducted to validate capability of the design. The results showed a 69-fold increase in stiffness of individual finger and a 30-fold increase in gripper’s load capacity.

A Novel Variable Stiffness Compliant Robotic Gripper Based on Layer Jamming

2020 ◽  
Vol 12 (5) ◽  
Author(s):  
Yuan Gao ◽  
Xiguang Huang ◽  
Ishan Singh Mann ◽  
Hai-Jun Su
Keyword(s):  
Load Capacity ◽  
Variable Stiffness ◽  
Fold Increase ◽  
Servo Motor ◽  
Shape Morphing ◽  
On Demand ◽  
Individual Finger ◽  
Low Load ◽  
3D Printed ◽  
Stiffness Variation

Abstract In this paper, we present a novel compliant robotic gripper with three variable stiffness fingers. While the shape morphing of the fingers is cable-driven, the stiffness variation is enabled by layer jamming. The inherent flexibility makes compliant gripper suitable for tasks such as grasping soft and irregular objects. However, their relatively low load capacity due to intrinsic compliance limits their applications. Variable stiffness robotic grippers have the potential to address this challenge as their stiffness can be tuned on demand of tasks. In our design, the compliant backbone of finger is made of 3D-printed PLA materials sandwiched between thin film materials. The workflow of the robotic gripper follows two basic steps. First, the compliant skeleton is driven by a servo motor via a tension cable and bend to a desired shape. Second, upon application of a negative pressure, the finger is stiffened up because friction between contact surfaces of layers that prevents their relative movement increases. As a result, their load capacity will be increased proportionally. Tests for stiffness of individual finger and load capacity of the robotic gripper are conducted to validate capability of the design. The results showed a 180-fold increase in stiffness of individual finger and a 30-fold increase in gripper’s load capacity.

Design, Modeling, and Manufacturing of a Variable Lateral Stiffness Arm via Shape Morphing Mechanisms

2021 ◽  
pp. 1-15
Author(s):  
Yu She ◽  
Zhaoyuan Gu ◽  
Siyang Song ◽  
Hai-Jun Su ◽  
Junmin Wang
Keyword(s):  
Variable Stiffness ◽  
Robotic Arm ◽  
Lateral Stiffness ◽  
Robot Arm ◽  
Safety Issues ◽  
Shape Morphing ◽  
Compliant Joints ◽  
Mechanical Compliance ◽  
3D Printed ◽  
Tunable Stiffness

Abstract In this paper, we present a continuously tunable stiffness arm for safe physical human-robot interactions. Compliant joints and compliant links are two typical solutions to address safety issues for physical human-robot interactions via introducing mechanical compliance to robotic systems. While extensive studies explore variable stiffness joints/actuators, variable stiffness links for safe physical human-robot interactions are much less studied. This paper details the design and modeling of a compliant robotic arm whose stiffness can be continuously tuned via cable-driven mechanisms actuated by a single servo motor. Specifically, a 3D printed compliant robotic arm is prototyped and tested by static experiments, and an analytical model of the variable stiffness arm is derived and validated by testing. The results show that the lateral stiffness of the robot arm can achieve a variety of 221.26 % given a morphing angle of 90°. The variable stiffness arm design developed in this study could be a promising approach to address safety concerns for safe physical human-robot interactions.

scholarly journals Fully-Printable Soft Actuator with Variable Stiffness by Phase Transition and Hydraulic Regulations

Actuators ◽  
2021 ◽  
Vol 10 (10) ◽  
pp. 269
Author(s):  
Tingchen Liao ◽  
Manivannan Sivaperuman Kalairaj ◽  
Catherine Jiayi Cai ◽  
Zion Tsz Ho Tse ◽  
Hongliang Ren
Keyword(s):  
Transition Period ◽  
Shape Memory Polymer ◽  
Variable Stiffness ◽  
Pressure Variation ◽  
Soft Actuator ◽  
Output Force ◽  
Load Carrying ◽  
Force Variation ◽  
Stiffness Variation ◽  
Short Transition

Actuators with variable stiffness have vast potential in the field of compliant robotics. Morphological shape changes in the actuators are possible, while they retain their structural strength. They can shift between a rigid load-carrying state and a soft flexible state in a short transition period. This work presents a hydraulically actuated soft actuator fabricated by a fully 3D printing of shape memory polymer (SMP). The actuator shows a stiffness of 519 mN/mm at 20 ∘C and 45 mN/mm at 50 ∘C at the same pressure (0.2 MPa). This actuator demonstrates a high stiffness variation of 474 mN/mm (10 times the baseline stiffness) for a temperature change of 30 ∘C and a large variation (≈1150%) in average stiffness. A combined variation of both temperature (20–50 ∘C) and pressure (0–0.2 MPa) displays a stiffness variation of 501 mN/mm. The pressure variation (0–0.2 MPa) in the actuator also shows a large variation in the output force (1.46 N) at 50 ∘C compared to the output force variation (0.16 N) at 20 ∘C. The pressure variation is further utilized for bending the actuator. Varying the pressure (0–0.2 MPa) at 20 ∘C displayed no bending in the actuator. In contrast, the same variation of pressure at 50 ∘C displayed a bending angle of 80∘. A combined variation of both temperature (20–50 ∘C) and pressure (0–0.2 MPa) shows the ability to bend 80∘. At the same time, an additional weight (300 g) suspended to the actuator could increase its bending capability to 160∘. We demonstrated a soft robotic gripper varying its stiffness to carry objects (≈100 g) using two individual actuators.

Design guidelines for bump-type compliant conical foil bearing

2021 ◽  
pp. 095440622110127
Author(s):  
Hongyang Hu ◽  
Ming Feng
Keyword(s):  
Load Capacity ◽  
Design Guidelines ◽  
Foil Thickness ◽  
Axial Stiffness ◽  
Structural Stiffness ◽  
Foil Bearing ◽  
Stiffness Model ◽  
Opposite Position ◽  
Stiffness Distribution ◽  
Half Length

The integral bump foil strip cannot optimize the performance for the compliant conical foil bearing (CFB) as the uneven distribution of structural stiffness. To maximize the bearing characteristics, this paper proposed different bump foil schemes. Firstly, the anisotropy of CFB was studied based on the nonlinear bump stiffness model, and the circumferentially separated foil structure was proposed. Moreover, an axially separated bump foil structure with the variable bump length was introduced to make the axial stiffness distribution more compliant with the gas pressure. In addition, the effect of foil thickness was also discussed. The results show that CFB with integral bump foil exhibits obvious anisotropy, and the suggested installation angle for largest load capacity and best dynamic stability are in the opposite position. Fortunately, a circumferential separated bump foil can improve this defect. The characteristics of CFB with axial separated foil structure can be improved significantly, especially for that with more strips and the variable bump half-length design. The suitable bump and top foil thickness should be set considering the improved supporting performance and proper flexibility. The results can give some guidelines for the design of CFB.

scholarly journals A Stiffness Variable Passive Compliance Device with Reconfigurable Elastic Inner Skeleton and Origami Shell

2020 ◽  
Vol 33 (1) ◽  
Author(s):  
Zhuang Zhang ◽  
Genliang Chen ◽  
Weicheng Fan ◽  
Wei Yan ◽  
Lingyu Kong ◽  
...  
Keyword(s):  
Variable Stiffness ◽  
Rehabilitation Robotics ◽  
Human Robot Interaction ◽  
Main Concept ◽  
Robot Interaction ◽  
Switching Speed ◽  
Leaf Springs ◽  
Stiffness Variation ◽  
Low Stiffness ◽  
Large Deflection Problem

Abstract Devices with variable stiffness are drawing more and more attention with the growing interests of human-robot interaction, wearable robotics, rehabilitation robotics, etc. In this paper, the authors report on the design, analysis and experiments of a stiffness variable passive compliant device whose structure is a combination of a reconfigurable elastic inner skeleton and an origami shell. The main concept of the reconfigurable skeleton is to have two elastic trapezoid four-bar linkages arranged in orthogonal. The stiffness variation generates from the passive deflection of the elastic limbs and is realized by actively switching the arrangement of the leaf springs and the passive joints in a fast, simple and straightforward manner. The kinetostatics and the compliance of the device are analyzed based on an efficient approach to the large deflection problem of the elastic links. A prototype is fabricated to conduct experiments for the assessment of the proposed concept. The results show that the prototype possesses relatively low stiffness under the compliant status and high stiffness under the stiff status with a status switching speed around 80 ms.

Tracheal Smooth Muscle Response to Vibrations

2004 ◽  
Author(s):  
Y. Du ◽  
A. M. Al-Jumaily
Keyword(s):  
Finite Element ◽  
Smooth Muscle ◽  
Smooth Muscles ◽  
Variable Stiffness ◽  
Tracheal Smooth Muscle ◽  
Element Formulation ◽  
The Finite Element Method ◽  
External Excitation ◽  
Stiffness Variation ◽  
Smooth Muscle Contractions

An experimental and theoretical investigation is conducted to study the dynamic response of a tracheal smooth muscle under isometric conditions. The stiffness variation due to external vibration is investigated experimentally using trachea smooth muscles from excised pigs. The finite element method is used to model the muscle as a 2-D strip with variable stiffness and subjected to an external excitation. The Cauchy’s first law is invoked to describe the motion and Galerkin’s method is used to develop the finite element formulation. Different boundary conditions are considered to simulate the vibration characteristics and to get realistic compatibility with actual muscle conditions. The model predicts the stiffness variation due to vibration that is observed experimentally. The main outcome from this investigation is the fact that smooth muscle contractions could be relaxed by tuning the excitation within predetermined frequencies.

Experiments and predictions on the performance of double-bump foil bearings: Effects of bearing loads and height difference between bumps

2017 ◽  
Vol 231 (11) ◽  
pp. 1474-1485 ◽  
Author(s):  
Kai Feng ◽  
Tao Zhang ◽  
Xueyuan Zhao
Keyword(s):  
Load Capacity ◽  
Load Test ◽  
Underlying Structure ◽  
Viscous Damping ◽  
Structural Stiffness ◽  
Static Load Test ◽  
Height Difference ◽  
Equivalent Viscous Damping ◽  
Foil Bearings ◽  
Foil Bearing

The concept of multilayer bump foils was introduced in the design of bump foil bearings to produce a double-bump foil bearing, which can provide increased load capacity and damping by adding another bump foil in the underlying structure. The height difference between the upper and lower bumps is a crucial parameter in the design and application of such structure. In this study, two double-bump foil bearings with various height differences between bumps are designed and fabricated to compare with an ordinary bump foil bearing. Three bearings are examined via static and dynamic load tests to estimate the structural stiffness and equivalent viscous damping. Test results indicate that lower bumps can enhance both the structural stiffness and equivalent viscous damping. A theoretical link-spring model, which exhibits good agreement with the data obtained from the static load test, is adopted to analyze the effect of height difference between bumps on gas film thickness and gas pressure of double-bump foil bearings. Results show that lower bumps of the double-bump foil bearing with a smaller height difference become active more easily and are more likely to form a stable double-bump supporting structure.

PECULIARITIES OF THE DEVELOPMENT AND MANUFACTURING OF THE PROTOTYPE OF GAPLESS PLANETARY ROLLER SCREW MECHANISM

2019 ◽  
pp. 3-12
Author(s):  
D. S. Blinov ◽  
D. K. Dragun ◽  
A. S. Nosov
Keyword(s):  
Load Capacity ◽  
New Technology ◽  
Experimental Studies ◽  
Radial Deformation ◽  
Short Life ◽  
Low Load ◽  
Roller Screw ◽  
Metrological Control ◽  
Screw Mechanism ◽  
Theoretical Results

Known designs of gapless planetary roller screw mechanisms (PRSM) are highly accurate and rigid, but have low load capacity and short life. To eliminate these shortcomings, a new design of a gapless PRSM was developed and patented using a one-piece thin-walled nut. Due to radial deformation of the nut, the gaps between the threaded parts of the mechanism are chosen. The previous works have described the design of a new gapless PRSM and theoretically proved the possibility of a significant increase in load capacity and life using this mechanism. To confirm the theoretical results and conclusions, it is necessary to conduct experimental studies for which a prototype of the new gapless PRSM was made. The work presented describes a new technology for manufacturing threaded parts of this mechanism. In contrast to the traditional technology of grinding screw surfaces of the PRSM parts, which require special expensive equipment, it is proposed to grind and bore the screw surfaces of the parts with special plates on CNC turning machines. The metrological control has established that the dimensions of all parts of the prototype, including the threaded parts, did not go beyond the fields of the calculated or assigned tolerances.

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