Variable Stiffness Mechanism for Tremor Suppression in Human-Robot Interaction

2018 ◽  
Author(s):  
Sri Sadhan Jujjavarapu ◽  
M. Amin Karami ◽  
Ehsan T. Esfahani
Keyword(s):  
Permanent Magnets ◽  
Involuntary Movement ◽  
Cutoff Frequency ◽  
Variable Stiffness ◽  
Rehabilitation Robotics ◽  
Human Robot Interaction ◽  
Limb Stiffness ◽  
Wide Range ◽  
Nonlinear Force ◽  
Human Limb

Variable stiffness mechanisms have a wide range of applications in the field of human-robot interactions such as rehabilitation robotics, prosthesis and industrial robotics due to their ability to comply with the human limb stiffness in an unstructured environment. This paper presents the analysis of a single degree of freedom variable stiffness actuator based on nonlinear force interactions between permanent magnets and its effect on the natural frequency of the system. In the proposed mechanism, variable stiffness is achieved by modifying the separation between magnets. The main goal here is to achieve a desired cutoff frequency by varying the stiffness of the system to filter out the involuntary movement of upper limb during physical human-robot interactions. Moreover, due to the spring-like non-contact force interactions between magnets, this mechanism can prevent the exchange of high impact forces between the robot and human.

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.

Design of a Compliant Mechanism to Generate an Arbitrary Nonlinear Force-Deflection Profile

2018 ◽  
Author(s):  
Kyle Buschkoetter ◽  
Ashok Midha
Keyword(s):  
Resistance Exercise ◽  
Case Studies ◽  
Compliant Mechanism ◽  
Synthesis Method ◽  
Variable Stiffness ◽  
Variable Resistance ◽  
Wide Range ◽  
Nonlinear Force ◽  
Exercise Equipment ◽  
Variable Stiffness Actuators

This paper presents a compliant mechanism that can generate a wide range of force-deflection profiles. This partially compliant mechanism is comprised of a wedge cam with a compliant follower. The designer specifies the material and geometric properties of the compliant segment, as well as a desired force-deflection profile. A cam surface is then synthesized that helps generate this profile. The synthesis method is validated experimentally with the help of two case studies. Some possible areas of application include robotics, variable stiffness actuators, electrical connectors, design for automotive crashworthiness, and variable resistance exercise equipment.

Analysis and Study of Variable Stiffness Joints Based on Bi-Material Nested Elastomers

2020 ◽  
Author(s):  
Wei Sun ◽  
Jingjun Yu ◽  
Yueri Cai
Keyword(s):  
Magnetic Field ◽  
Cantilever Beam ◽  
Stress Function ◽  
Compliant Mechanisms ◽  
Tangential Force ◽  
Variable Stiffness ◽  
Human Robot Interaction ◽  
Wide Range ◽  
Magneto Rheological ◽  
Short Time

Abstract Variable stiffness joints are a kind of compliant mechanisms which can improve the safety of physical human-robot interaction which has attracted much attention in recent years. Elastic elements are used in the internal kinematic structures of variable stiffness joints. In this paper, Elastomers with magneto-rheological fluids (MRFs) properties have great potential application for variable stiffness joints (VSJs) and implantable bioelectronics devices by allowing actuators to rapidly and reversibly changed from a “fluid” to a “solid-like” state and precisely controlled within a very short time and over a wide range under a magnetic field. A new adjustable stiffness composites (ASCs) that combine an outside liner (PDMS) with a chamber (MRFs) is introduced. When improving the magnetic field intensity, the MRFs hardens and the stiffness increases by as much as 4–5 orders of magnitude. In order to solve the bi-material nested cantilever beam subjected to a concentrated tangential force at the free end of the beam, a theoretical approach is proposed by means of the Airy stress function method together with the stress function test solution. By comparing the results obtained from the theoretical and experimental measurements, a very good agreement is found, showing the accuracy and feasibility of the theoretical results. This solution will be useful in analyzing cantilever beam with arbitrary variations of bi-material nested and it can serve as a basis for establishing stiffness and stress theories. Due to the highly deformable of the ASCs, it has great potentially for our future soft robot design and manufacture work.

Design and Implementation of a Novel Variable Stiffness Actuator with Cam-Based Relocation Mechanism

2020 ◽  
pp. 1-22
Author(s):  
Yinghao Ning ◽  
Hailin Huang ◽  
Wenfu Xu ◽  
Weimin Zhang ◽  
Bing Li
Keyword(s):  
Variable Stiffness ◽  
Human Robot Interaction ◽  
Tracking Accuracy ◽  
Robot Interaction ◽  
Wide Range ◽  
Lever Mechanism ◽  
Point Control ◽  
Point To Point ◽  
Safe Performance ◽  
Variable Stiffness Actuators

Abstract Variable stiffness actuators (VSAs) are widely explored as they could improve the safe performance for human-robot interaction and make the system torque controllable based on the internal compliance. This paper presents a novel VSA based on the cam-based relocation mechanism (CRM-VSA), which is utilized to change the locations of pivot and spring of a lever mechanism simultaneously. Consequently, such structure makes the actuator compacted and the stiffness regulation designable which could help engineers to pursue different demands of stiffness regulation. The simultaneous relocations of the pivot and spring also permit a wide range of adjustable stiffness. By introducing linear guide pairs, the internal friction of the relocations of pivot and spring could be greatly reduced, thus enhancing the energy efficiency. To evaluate the performance of the proposed CRM-VSA, the point-to-point control strategy is developed which contributes to a higher tracking accuracy and oscillation attenuation at both the start and end points of the trajectory. Additionally, the performance of torque controllability is also verified through experiments. These excellent capabilities enable the proposed CRM-VSA to be qualified for constructing a robotic arm towards service applications.

A Geometric Parametric Analysis of a Magnetorheological Engine Mount

2010 ◽  
Author(s):  
Walter Anderson ◽  
Constantine Ciocanel ◽  
Mohammad Elahinia
Keyword(s):  
High Frequency ◽  
New Technology ◽  
Low Frequency ◽  
Variable Stiffness ◽  
Small Displacement ◽  
Element Analysis ◽  
Mr Fluid ◽  
Wide Range ◽  
Engine Mount ◽  
Vehicle Technology

Engine vibration has caused a great deal of research for isolation to be performed. Traditionally, isolation was achieved through the use of pure elastomeric (rubber) mounts. However, with advances in vehicle technology, these types of mounts have become inadequate. The inadequacy stems from the vibration profile associated with the engine, i.e. high displacement at low frequency and small displacement at high frequency. Ideal isolation would be achieved through a stiff mount for low frequency and a soft mount for high frequency. This is contradictory to the performance of the elastomeric mounts. Hydraulic mounts were then developed to address this problem. A hydraulic mount has variable stiffness and damping due to the use of a decoupler and an inertia track. However, further advances in vehicle technology have rendered these mounts inadequate as well. Examples of these advances are hybridization (electric and hydraulic) and cylinder on demand (VCM, MDS & ACC). With these technologies, the vibration excitation has a significantly different profile, occurs over a wide range of frequencies, and calls for a new technology that can address this need. Magnetorheological (MR) fluid is a smart material that is able to change viscosity in the presence of a magnetic field. With the use of MR fluid, variable damping and stiffness can be achieved. An MR mount has been developed and tested. The performance of the mount depends on the geometry of the rubber part as well as the behavior of the MR fluid. The rubber top of the mount is the topic of this study due to its major impact on the isolation characteristics of the MR mount. To develop a design methodology to address the isolation needs of different hybrid vehicles, a geometric parametric finite element analysis has been completed and presented in this paper.

Strain-engineering in AlGaN/GaN HEMTs: impact of silicon nitride passivation layer on electrical performance

2021 ◽  
Author(s):  
Sanghamitra Das ◽  
Taraprasanna Dash ◽  
Devika Jena ◽  
Eleena Mohapatra ◽  
C K Maiti
Keyword(s):  
Experimental Data ◽  
Compressive Strain ◽  
Cutoff Frequency ◽  
Strain Engineering ◽  
Electrical Performance ◽  
Current Gain ◽  
Great Promise ◽  
High Electron ◽  
Wide Range ◽  
Gan Hemts

Abstract In this work, we present a physics-based analysis of two-dimensional electron gas (2DEG) sheet carrier density and other microwave characteristics such as transconductance and cutoff frequency of AlxGa1-xN/GaN high electron mobility transistors (HEMT). An accurate polarization-dependent charge control-based analysis is performed for microwave performance assessment in terms of current, transconductance, gate capacitances, and cutoff frequency of lattice-mismatched AlGaN/GaN HEMTs. The influence of stress on spontaneous and piezoelectric polarization is included in the simulation of an AlGaN/GaN HEMT. We have shown the change in threshold voltage (Vt) due to tensile and compressive strain with different gate lengths. Also, the influence of stress due to the change in nitride thickness is presented. Our simulation results for drain current, transconductance, and current-gain cutoff frequency for various gate length devices are calibrated and verified with experimental data over a wide range of gate and drain applied voltages, which are expected to be useful for microwave circuit design. The predicted transconductance, drain conductance, and operation frequency are quite close to the experimental data. The AlGaN/GaN heterostructure HEMTs with nitride passivation layers show great promise as a candidate in future high speed and high power applications.

scholarly journals Robot Modeling for Physical Rehabilitation

Robotics ◽  
2013 ◽  
pp. 1212-1232 ◽  
Author(s):  
Rogério Sales Gonçalves ◽  
João Carlos Mendes Carvalho
Keyword(s):  
Mathematical Models ◽  
Three Dimensional ◽  
Mechanical Systems ◽  
Industrial Robots ◽  
Limb Movements ◽  
Rehabilitation Robots ◽  
Wide Range ◽  
Movable Platform ◽  
Human Limb ◽  
Robot Modeling

The science of rehabilitation shows that repeated movements of human limbs can help the patient regain function in the injured limb. There are three types of mechanical systems used for movement rehabilitation: robots, cable-based manipulators, and exoskeletons. Industrial robots can be used because they provide a three-dimensional workspace with a wide range of flexibility to execute different trajectories, which are useful for motion rehabilitation. The cable-based manipulators consist of a movable platform and a base, which are connected by multiple cables that can extend or retract. The exoskeleton is fixed around the patient's limb to provide the physiotherapy movements. This chapter presents a summary of the principal human limb movements, a review of several mechanical systems used for rehabilitation, as well as common mathematical models of such systems.

scholarly journals Application of Synchronous Brushless Motors in Electric Hand Tools

2012 ◽  
Vol 49 (1) ◽  
pp. 29-34
Author(s):  
J. Dirba ◽  
L. Lavrinovicha ◽  
N. Levin ◽  
V. Pugachev
Keyword(s):  
Permanent Magnets ◽  
Synchronous Motor ◽  
Hand Tools ◽  
Brushless Motors ◽  
Outer Rotor ◽  
Wide Range

Application of Synchronous Brushless Motors in Electric Hand Tools In the paper, the possibilities to apply synchronous brushless motors in the electric hand tools are considered. The potential of such motors is estimated in a wide range of characteristics. In particular, estimation is made for the electric hand plane with a synchronous motor having outer rotor and excitation from permanent magnets.

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