A Reconfigurable Variable-Stiffness Parallel Beam for Compliant Robotic Mechanisms Towards Safe Human Interaction

2021 ◽  
Author(s):  
Jiaming Fu ◽  
Dongming Gan
Keyword(s):  
Variable Stiffness ◽  
Human Robot Interaction ◽  
Human Interaction ◽  
Design Parameters ◽  
Parallel Beam ◽  
Element Analysis ◽  
Cross Sectional ◽  
Hollow Beam ◽  
Robotic Joints ◽  
Variable Compliance

Abstract To co-work with humans, robotic mechanisms need to have variable stiffness with high rigidity for performance and low compliance for safe interactions. This paper introduces a reconfigurable variable-stiffness parallel beam (VSPB) which can be used in both robotic joints and links for variable compliance. The VSPB is a compliant cantilever mechanism with hollow parallel beams in the middle and solid connections at both ends. Stiffness adjusting can be realized by changing the cross-sectional area property of the hollow beam segment discretely through a bistable mechanism block or continuously by the block sliding. Detailed stiffness models of the two VSPB stiffness modes with the block on and off are derived using the approach of serially connected beam modeling and superposition combination. The developed model not only works for thin-walled flexure beams but also general thick beam models. The stiffness change relationship with various design parameters is investigated using the developed model and validated by finite element analysis (FEA) results. The correlation between parameters and errors between FEA and theoretical values is observed and analyzed to optimize the model. These methods and results provide a new concept and theoretical basis for developing new variable stiffness robotic mechanisms towards safe human-robot interaction applications.

Design of composite helicopter rotor blades to meet given cross-sectional properties

2005 ◽  
Vol 109 (1100) ◽  
pp. 471-475 ◽  
Author(s):  
S. L. Lemanski ◽  
P. M. Weaver ◽  
G. F. J. Hill
Keyword(s):  
Finite Element ◽  
Objective Function ◽  
Helicopter Rotor ◽  
Design Parameters ◽  
Stochastic Methods ◽  
Element Analysis ◽  
Cross Sectional ◽  
Design Variables ◽  
Non Linear ◽  
Optimisation Methods

Abstract This paper examines the design of a composite helicopter rotor blade to meet given cross-sectional properties. As with many real-world problems, the choice of objective and design variables can lead to a problem with a non-linear and/or non-convex objective function, which would require the use of stochastic optimisation methods to find an optimum. Since the objective function is evaluated from the results of a finite element analysis of the cross section, the computational expense of using stochastic methods would be prohibitive. It is shown that by choosing appropriate simplified design variables, the problem becomes convex with respect to those design variables. This allows deterministic optimisation methods to be used, which is considerably more computationally efficient than stochastic methods. It is also shown that the design variables can be chosen such that the response of each individual cross-sectional property can be closely modelled by a linear approximation, even though the response of a single objective function to many design parameters is non-linear. The design problem may therefore be reformulated into a number of simultaneous linear equations that are easily solved by matrix methods, thus allowing an optimum to be located with the minimum number of computationally expensive finite element analyses.

A Comparative Study on the Effect of Mechanical Compliance for a Safe Physical Human–Robot Interaction

2020 ◽  
Vol 142 (6) ◽  
Author(s):  
Yu She ◽  
Siyang Song ◽  
Hai-Jun Su ◽  
Junmin Wang
Keyword(s):  
Impact Force ◽  
Variable Stiffness ◽  
Human Robot Interaction ◽  
Design Parameters ◽  
Robot Dynamics ◽  
Robot Interaction ◽  
Promising Alternative ◽  
Mechanical Compliance ◽  
Maximum Impact Force ◽  
The Impact

Abstract In this paper, we study the effects of mechanical compliance on safety in physical human–robot interaction (pHRI). More specifically, we compare the effect of joint compliance and link compliance on the impact force assuming a contact occurred between a robot and a human head. We first establish pHRI system models that are composed of robot dynamics, an impact contact model, and head dynamics. These models are validated by Simscape simulation. By comparing impact results with a robotic arm made of a compliant link (CL) and compliant joint (CJ), we conclude that the CL design produces a smaller maximum impact force given the same lateral stiffness as well as other physical and geometric parameters. Furthermore, we compare the variable stiffness joint (VSJ) with the variable stiffness link (VSL) for various actuation parameters and design parameters. While decreasing stiffness of CJs cannot effectively reduce the maximum impact force, CL design is more effective in reducing impact force by varying the link stiffness. We conclude that the CL design potentially outperforms the CJ design in addressing safety in pHRI and can be used as a promising alternative solution to address the safety constraints in pHRI.

The effect of the percentage of steered plies on the bending-induced buckling performance of a variable stiffness composite cylinder

2015 ◽  
Vol 22 (2) ◽  
pp. 149-156 ◽  
Author(s):  
Mohammad Rouhi ◽  
Hossein Ghayoor ◽  
Suong V. Hoa ◽  
Mehdi Hojjati
Keyword(s):  
Performance Improvement ◽  
Design Procedure ◽  
Laminated Composite ◽  
Variable Stiffness ◽  
Design Parameters ◽  
Composite Cylinder ◽  
Element Analysis ◽  
Fiber Placement ◽  
Structural Improvement ◽  
Automated Fiber Placement

AbstractThe fiber steering capability of automated fiber placement machines offers the designers more room to fully exploit the directional properties of composite materials. Circumferential stiffness tailoring by fiber steering can considerably increase the bending-induced buckling performance of laminated composite cylinders. The potential structural improvement resulting from fiber steering depends on different design parameters such as the number of plies considered for fiber steering in a laminate. In this study, the buckling performance improvement of a variable stiffness (VS) composite cylinder is investigated for different percentages of plies considered for fiber steering in a multilayered composite laminate. A surrogate-based modeling along with a multi-step optimization is used in the design procedure of this study. The improvements in the buckling performance are shown and verified using finite element analysis in ABAQUS software. The mechanisms leading to buckling performance improvement of VS composites are also investigated and presented for different percentages of fiber-steered plies.

scholarly journals Structural optimization of a new type of lever-assisted gear reducer based on a genetic algorithm

2021 ◽  
Vol 12 (1) ◽  
pp. 333-343
Author(s):  
Lei Guo ◽  
Zeyu Wang ◽  
Yuan Song ◽  
Xianjie Shan ◽  
Dongming Gan
Keyword(s):  
Genetic Algorithm ◽  
Gear Train ◽  
Design Parameters ◽  
Element Analysis ◽  
Heavy Load ◽  
Low Speed ◽  
Drive Mechanism ◽  
Input Shaft ◽  
Physical Prototype ◽  
Robotic Joints

Abstract. Gear reducers are critical for speed and torque transmissions between motors and manipulators. With the development of robotic research, many new requirements, such as low speed and heavy load, have been proposed for the design of gear reducers used in the joints. To meet these challenges, here, we present the design of a new gear reducer based on a spherical motion sub-lever drive mechanism. Our lever-based gear reducer can transmit the speed and torque from the input shaft to the output shaft through a fixed-axis gear train transmission, lever transmission, and internal translational gear transmission. Compared with traditional gear reducers, our lever-based reducer has stronger load capacities and is suitable for low-speed and heavy-load scenarios. The design parameters of the lever drive mechanism were optimized via finite element analysis and a genetic algorithm, and the assembly of the lever drive mechanism was further simplified. We found the dimensions of the lever are critical for improving the overall performance of this reducer. In addition, the transmission ability of this reducer was demonstrated by a physical prototype. This reducer will find many applications in robotic joints, cranes, and mine hoists.

The role and relationship of mindreading and social attunement in HRI – position statements of interdisciplinary researchers. Workshop HRI'20

2020 ◽  
Author(s):  
Agnieszka Wykowska ◽  
Jairo Pérez-Osorio ◽  
Stefan Kopp
Keyword(s):  
Mental States ◽  
Human Robot Interaction ◽  
Human Interaction ◽  
Artificial Agents ◽  
The Novel ◽  
Robot Interaction ◽  
Novel Coronavirus ◽  
Relationship Of ◽  
The Relationship

This booklet is a collection of the position statements accepted for the HRI’20 conference workshop “Social Cognition for HRI: Exploring the relationship between mindreading and social attunement in human-robot interaction” (Wykowska, Perez-Osorio & Kopp, 2020). Unfortunately, due to the rapid unfolding of the novel coronavirus at the beginning of the present year, the conference and consequently our workshop, were canceled. On the light of these events, we decided to put together the positions statements accepted for the workshop. The contributions collected in these pages highlight the role of attribution of mental states to artificial agents in human-robot interaction, and precisely the quality and presence of social attunement mechanisms that are known to make human interaction smooth, efficient, and robust. These papers also accentuate the importance of the multidisciplinary approach to advance the understanding of the factors and the consequences of social interactions with artificial agents.

A Simplified Design Model for Modular Steel Buildings Subject to Vapor Cloud Explosions (VCEs)

2020 ◽  
Vol 14 ◽  
Author(s):  
Osama Bedair
Keyword(s):  
Dynamic Response ◽  
Minimum Cost ◽  
Design Parameters ◽  
Front Wall ◽  
Steel Buildings ◽  
Element Analysis ◽  
Analysis And Design ◽  
Vapor Cloud ◽  
Building Components ◽  
Analytical Expressions

Background: Modular steel buildings (MSB) are extensively used in petrochemical plants and refineries. Limited guidelines are available in the industry for analysis and design of (MSB) subject to accidental vapor cloud explosions (VCEs). Objectives: The paper presents simplified engineering model for modular steel buildings (MSB) subject to accidental vapor cloud explosions (VCEs) that are extensively used in petrochemical plants and refineries. Method: A Single degree of freedom (SDOF) dynamic model is utilized to simulate the dynamic response of primary building components. Analytical expressions are then provided to compute the dynamic load factors (DLF) for critical building elements. Recommended foundation systems are also proposed to install the modular building with minimum cost. Results: Numerical results are presented to illustrate the dynamic response of (MSB) subject to blast loading. It is shown that (DLF)=1.6 is attained at (td/t)=0.4 for front wall (W1) with (td/T)=1.25. For side walls (DLF)=1.41 and is attained at (td/t)=0.6. Conclusions: The paper presented simplified tools for analysis and design of (MSB) subject accidental vapor cloud blast explosions (VCEs). The analytical expressions can be utilized by practitioners to compute the (MSB) response and identify the design parameters. They are simple to use compared to Finite Element Analysis.

Evaluation of web reinforcements in prestressed concrete box girders through shear-transverse bending domains

2020 ◽  
pp. 136943322098170
Author(s):  
Michele Fabio Granata ◽  
Antonino Recupero
Keyword(s):  
Analytical Model ◽  
Prestressed Concrete ◽  
3D Analysis ◽  
Box Girders ◽  
Element Analysis ◽  
Cross Sectional ◽  
Interaction Domains ◽  
Global And Local ◽  
Resultant Forces

In concrete box girders, the amount and distribution of reinforcements in the webs have to be estimated considering the local effects due to eccentric external loads and cross-sectional distortion and not only the global effect due to the resultant forces of a longitudinal analysis: shear, torsion and bending. This work presents an analytical model that allows designers to take into account the interaction of all these effects, global and local, for the determination of the reinforcements. The model is based on the theory of stress fields and it has been compared to a 3D finite element analysis, in order to validate the interaction domains. The results show how the proposed analytical model allows an easy and reliable reinforcement evaluation, in agreement with a more refined 3D analysis but with a reduced computational burden.

scholarly journals In Response to COVID-19: Current Trends in Orthopaedic Surgery Sports Medicine Fellowships

2021 ◽  
Vol 9 (2) ◽  
pp. 232596712098700
Author(s):  
Jordan L. Liles ◽  
Richard Danilkowicz ◽  
Jeffrey R. Dugas ◽  
Marc Safran ◽  
Dean Taylor ◽  
...  
Keyword(s):  
Sports Medicine ◽  
Skills Training ◽  
Cross Sectional Study ◽  
Surgical Skills ◽  
Human Interaction ◽  
Third Party ◽  
Service Needs ◽  
Case Volume ◽  
Cross Sectional ◽  
Sports Coverage

Background: The COVID-19 (SARS-COV-2) pandemic has brought unprecedented challenges to the health care system and education models. The reduction in case volume, transition to remote learning, lack of sports coverage opportunities, and decreased clinical interactions have had an immediate effect on orthopaedic sports medicine fellowship programs. Purpose/Hypothesis: Our purpose was to gauge the response to the pandemic from a sports medicine fellowship education perspective. We hypothesized that (1) the COVID-19 pandemic has caused a significant change in training programs, (2) in-person surgical skills training and didactic learning would be substituted with virtual learning, and (3) hands-on surgical training and case numbers would decrease and the percentage of fellows graduating with skill levels commensurate with graduation would decrease. Study Design: Cross-sectional study. Methods: In May 2020, a survey was sent to the fellowship directors of all 90 orthopaedic sports medicine fellowships accredited by the Accreditation Council for Graduate Medical Education; it included questions on program characteristics, educational lectures, and surgical skills. A total of 37 completed surveys (41%) were returned, all of which were deidentified. Responses were compiled and saved on a closed, protected institutional server. Results: In a majority of responding programs (89%), fellows continued to participate in the operating room. Fellows continued with in-person clinical visits in 65% of programs, while 51% had their fellows participate in telehealth visits. Fellows were “redeployed” to help triage and assist with off-service needs in 21% of programs compared with 65% of resident programs having residents rotate off service. Regarding virtual education, 78% of programs have used or are planning to use platforms offered by medical societies, and 49% have used or are planning to use third-party independent education platforms. Of the 37 programs, 30 reported no in-person lectures or meetings, and there was a sharp decline in the number of programs participating in cadaver laboratories (n = 10; 27%) and industry courses (n = 6; 16%). Conclusion: Virtual didactic and surgical education and training as well as telehealth will play a larger role in the coming year than in the past. There are effects to fellows’ exposure to sports coverage and employment opportunities. The biggest challenge will be how to maintain the element of human interaction and connect with patients and trainees at a time when social distancing is needed to curb the spread of COVID-19.

scholarly journals Research on the Computed Tomography Pebble Flow Detecting System for HTR-PM

2017 ◽  
Vol 2017 ◽  
pp. 1-13
Author(s):  
Xin Wan ◽  
Ximing Liu ◽  
Jichen Miao ◽  
Peng Cong ◽  
Yuai Zhang ◽  
...  
Keyword(s):  
Computed Tomography ◽  
Three Dimensional ◽  
Helical Ct ◽  
Design Parameters ◽  
Three Dimensional Model ◽  
Safe Operation ◽  
Cross Sectional ◽  
Ct System ◽  
Near Future ◽  
Pebble Flow

Pebble dynamics is important for the safe operation of pebble-bed high temperature gas-cooled reactors and is a complicated problem of great concern. To investigate it more authentically, a computed tomography pebble flow detecting (CT-PFD) system has been constructed, in which a three-dimensional model is simulated according to the ratio of 1 : 5 with the core of HTR-PM. A multislice helical CT is utilized to acquire the reconstructed cross-sectional images of simulated pebbles, among which special tracer pebbles are designed to indicate pebble flow. Tracer pebbles can be recognized from many other background pebbles because of their heavy kernels that can be resolved in CT images. The detecting principle and design parameters of the system were demonstrated by a verification experiment on an existing CT system in this paper. Algorithms to automatically locate the three-dimensional coordinates of tracer pebbles and to rebuild the trajectory of each tracer pebble were presented and verified. The proposed pebble-detecting and tracking technique described in this paper will be implemented in the near future.

scholarly journals Design of an Ultra-Wideband Microstrip-to-Slotline Transition on Low-Permittivity Substrate

Electronics ◽  
2020 ◽  
Vol 9 (8) ◽  
pp. 1329
Author(s):  
Jung Seok Lee ◽  
Gwan Hui Lee ◽  
Wahab Mohyuddin ◽  
Hyun Chul Choi ◽  
Kang Wook Kim
Keyword(s):  
Microstrip Line ◽  
Return Loss ◽  
Analytical Formula ◽  
Parameter Tuning ◽  
Ultra Wideband ◽  
Design Parameters ◽  
Analytical Line ◽  
Cross Sectional ◽  
Analysis And Design ◽  
Low Permittivity

Analysis and design of an ultra-wideband microstrip-to-slotline transition on a low permittivity substrate is presented. Cross-sectional structures along the proposed transition are analyzed using conformal mapping assuming quasi-TEM modes, attaining one analytical line impedance formula with varying design parameters. Although the slotline is a non-TEM transmission line, the transitional structures are configured to have quasi-TEM modes before forming into the slotline. The line impedance is optimally tapered using the Klopfenstein taper, and the electric field shapes are smoothly transformed from microstrip line to slotline. The analytical formula is accurate within 5% difference, and the final transition configuration can be designed without parameter tuning. The implemented microstrip-to-slotline transition possesses insertion loss of less than 1.5 dB per transition and return loss of more than 10 dB from 4.4 to over 40 GHz.

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