Design and Modeling of a Continuously Tunable Stiffness Arm for Safe Physical Human–Robot Interaction

2019 ◽  
Vol 12 (1) ◽  
Author(s):  
Yu She ◽  
Hai-Jun Su ◽  
Deshan Meng ◽  
Cheng Lai
Keyword(s):  
Human Robot Interaction ◽  
Robotic Arm ◽  
Injury Criteria ◽  
Alternative Approach ◽  
Stiffness Model ◽  
Rigid Body Model ◽  
Physical Prototype ◽  
Head Injury Criteria ◽  
Impact Injury ◽  
Tunable Stiffness

Abstract To reduce injury in physical human–robot interactions (pHRIs), a common practice is to introduce compliance to joints or arm of a robotic manipulator. In this paper, we present a robotic arm made of parallel guided beams whose stiffness can be continuously tuned by morphing the shape of the cross section through two four-bar linkages actuated by servo motors. An analytical lateral stiffness model is derived based on the pseudo-rigid-body model and validated by experiments. A physical prototype of a three-armed manipulator is built. Extensive stiffness and impact tests are conducted, and the results show that the stiffness of the robotic arm can be changed up to 3.6 times at a morphing angle of 37 deg. At an impact velocity of 2.2 m/s, the peak acceleration has a decrease of 19.4% and a 28.57% reduction of head injury criteria (HIC) when the arm is tuned from the high stiffness mode to the low stiffness mode. These preliminary results demonstrate the feasibility to reduce impact injury by introducing compliance into the robotic link and that the compliant link solution could be an alternative approach for addressing safety concerns of physical human–robot interactions.

Design and Prototype of a Tunable Stiffness Arm for Safe Human-Robot Interaction

2016 ◽  
Author(s):  
Yu She ◽  
Hai-Jun Su ◽  
Cheng Lai ◽  
Deshan Meng
Keyword(s):  
Impact Velocity ◽  
Robot Manipulator ◽  
Variable Stiffness ◽  
Human Robot Interaction ◽  
Robot Interaction ◽  
Injury Criteria ◽  
Straight Beam ◽  
Head Injury Criteria ◽  
The Impact ◽  
Tunable Stiffness

In this paper, we present a tunable stiffness robot link for safe human-robot interaction. Stiffness of a manipulator determines the injury levels of a human from an impact between robots and operators, given a specific impact velocity. Compliance of a robot manipulator includes joint compliance and link compliance. Variable stiffness design from the viewpoint of actuators have been widely studied, while adjustable stiffness robotic link in the application of human robot interaction is rare in literatures. This paper details the design of a tunable stiffness robotic manipulator via four bar linkages which are actuated by servo motors. A 3D model of the morphing beam is constructed, and a robot which is made up of 3 morphing arms is designed. Prototypes using 3D printer are fabricated. Numerous tests have been done, and the results show that the stiffness is able to change 3.6 times given a morphing angle of π/4. Given an impact velocity of 2.2 m/s, the impact tests show that the acceleration has a 19.4% decrease comparing the curved beam and straight beam, and the head injury criteria (HIC) significantly decreases from 210.3 m5/2s−4 to 150.3 m5/2s−4, which is much safer to the operators. This paper explores the research of tunable stiffness on robotic links in the application of human robot interaction, expanding the research arena with regarding to human safe robot design.

scholarly journals Cable Tension Analysis Oriented the Enhanced Stiffness of a 3-DOF Joint Module of a Modular Cable-Driven Human-Like Robotic Arm

2020 ◽  
Vol 10 (24) ◽  
pp. 8871
Author(s):  
Kaisheng Yang ◽  
Guilin Yang ◽  
Chi Zhang ◽  
Chinyin Chen ◽  
Tianjiang Zheng ◽  
...  
Keyword(s):  
Objective Function ◽  
Optimization Model ◽  
Human Robot Interaction ◽  
Robotic Arm ◽  
Robot Interaction ◽  
Cable Tension ◽  
Tension Distribution ◽  
Stiffness Model ◽  
Redundantly Actuated ◽  
Objective Function Values

Inspired by the structure of human arms, a modular cable-driven human-like robotic arm (CHRA) is developed for safe human–robot interaction. Due to the unilateral driving properties of the cables, the CHRA is redundantly actuated and its stiffness can be adjusted by regulating the cable tensions. Since the trajectory of the 3-DOF joint module (3DJM) of the CHRA is a curve on Lie group SO(3), an enhanced stiffness model of the 3DJM is established by the covariant derivative of the load to the displacement on SO(3). In this paper, we focus on analyzing the how cable tension distribution problem oriented the enhanced stiffness of the 3DJM of the CHRA for stiffness adjustment. Due to the complexity of the enhanced stiffness model, it is difficult to solve the cable tensions from the desired stiffness analytically. The problem of stiffness-oriented cable tension distribution (SCTD) is formulated as a nonlinear optimization model. The optimization model is simplified using the symmetry of the enhanced stiffness model, the rank of the Jacobian matrix and the equilibrium equation of the 3DJM. Since the objective function is too complicated to compute the gradient, a method based on the genetic algorithm is proposed for solving this optimization problem, which only utilizes the objective function values. A comprehensive simulation is carried out to validate the effectiveness of the proposed method.

A Continuously Tunable Stiffness Arm With Cable-Driven Mechanisms for Safe Physical Human-Robot Interaction

2020 ◽  
Author(s):  
Yu She ◽  
Zhaoyuan Gu ◽  
Siyang Song ◽  
Hai-Jun Su ◽  
Junmin Wang
Keyword(s):  
Variable Stiffness ◽  
Human Robot Interaction ◽  
Robotic Arm ◽  
Robot Arm ◽  
Robot Interaction ◽  
Safety Issues ◽  
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 interaction 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 study demonstrates that the compliant link design could be a promising approach to address safety concerns for safe physical human-robot interactions.

scholarly journals Evaluation of Head Injury Criteria for Injury Prediction Effectiveness: Computational Reconstruction of Real-World Vulnerable Road User Impact Accidents

2021 ◽  
Vol 9 ◽  
Author(s):  
Fang Wang ◽  
Zhen Wang ◽  
Lin Hu ◽  
Hongzhen Xu ◽  
Chao Yu ◽  
...  
Keyword(s):  
Head Injury ◽  
Real World ◽  
Head Injuries ◽  
Axonal Injury ◽  
Diffuse Axonal Injury ◽  
Road User ◽  
Injury Criteria ◽  
Brain Deformation ◽  
Vulnerable Road User ◽  
Head Injury Criteria

This study evaluates the effectiveness of various widely used head injury criteria (HICs) in predicting vulnerable road user (VRU) head injuries due to road traffic accidents. Thirty-one real-world car-to-VRU impact accident cases with detailed head injury records were collected and replicated through the computational biomechanics method; head injuries observed in the analyzed accidents were reconstructed by using a finite element (FE)-multibody (MB) coupled pedestrian model [including the Total Human Model for Safety (THUMS) head–neck FE model and the remaining body segments of TNO MB pedestrian model], which was developed and validated in our previous study. Various typical HICs were used to predict head injuries in all accident cases. Pearson’s correlation coefficient analysis method was adopted to investigate the correlation between head kinematics-based injury criteria and the actual head injury of VRU; the effectiveness of brain deformation-based injury criteria in predicting typical brain injuries [such as diffuse axonal injury diffuse axonal injury (DAI) and contusion] was assessed by using head injury risk curves reported in the literature. Results showed that for head kinematics-based injury criteria, the most widely used HICs and head impact power (HIP) can accurately and effectively predict head injury, whereas for brain deformation-based injury criteria, the maximum principal strain (MPS) behaves better than cumulative strain damage measure (CSDM0.15 and CSDM0.25) in predicting the possibility of DAI. In comparison with the dilatation damage measure (DDM), MPS seems to better predict the risk of brain contusion.

scholarly journals Numerical Simulation of Airbag and Study on the Effect of Airbag Parameters on Head Injury Criteria

2021 ◽  
Vol 9 (9) ◽  
pp. 1654-1666
Author(s):  
Aakash R
Keyword(s):  
Finite Element ◽  
Head Injury ◽  
Traffic Safety ◽  
Critical Role ◽  
Highway Traffic ◽  
Element Analysis ◽  
National Highway Traffic Safety ◽  
Occupant Safety ◽  
Injury Criteria ◽  
Head Injury Criteria

Abstract: In the case of an accident, inflatable restraints system plays a critical role in ensuring the safety of vehicle occupants. Frontal airbags have saved 44,869 lives, according to research conducted by the National Highway Traffic Safety Administration (NHTSA).Finite element analysis is extremely important in the research and development of airbags in order to ensure optimum protection for occupant. In this work, we simulate a head impact test with a deploying airbag and investigate the airbag's parameters. The airbag's performance is directly influenced by the parameters of the cushion such as vent area and fabric elasticity. The FEM model is analysed to investigate the influence of airbag parameter, and the findings are utilised to determine an optimal value that may be employed in the construction of better occupant safety systems. Keywords: airbag, finite element method, occupant safety, frontal airbag, vent size, fabric elasticity, head injury criteria

Performance of Hood System and Head Injury Criteria Subjected to Frontal Impacts

2012 ◽  
Vol 165 ◽  
pp. 270-274 ◽  
Author(s):  
J. Mai Nursherida ◽  
Sahari B. Barkawi ◽  
A.A. Nuraini ◽  
Aidy Ali ◽  
A.A. Faieza ◽  
...  
Keyword(s):  
Head Injury ◽  
Mild Steel ◽  
Epoxy Composite ◽  
Important Variable ◽  
Plane Failure ◽  
Head Injury Criterion ◽  
Frontal Impacts ◽  
Injury Criteria ◽  
Head Injury Criteria ◽  
Protective Performance

The aim of this study is to analyze the effect of steel and composite material on pedestrian head injury criteria of hood system. The hood is made of mild steel and aluminum, e-glass/epoxy composite and carbon epoxy composite are studied and characterized by impact modeling using LS-DYNA V971 in accordance with United States New Car Assessment Program (US-NCAP) frontal impact velocity and based on European Enhanced Vehicle-safety Committee. The most important variable of this structure are mass, material, internal energy, and Head Injury Criterion (HIC). The results are compared with hood made of mild steel. Three types of materials are used which consists of mild steel as reference materials, Aluminum AA5182, E-glass/epoxy composite and carbon fiber/epoxy composite with four different fiber configurations. The in-plane failure behaviors of the composites were evaluated by using Tsai Wu failure criterion. The results for the composite materials are compared to that of steel to find the best material with lowest HIC values. In order to evaluate the protective performance of the baseline hood, the Finite Element models of 50th percentile an adult pedestrian dummy is used in parallel to impact the hood. It was found that aluminum AA5182 hood can reduce the Head Injury Criterion (HIC) by comparing with the baseline hood. For pedestrian crash, it is observed that Aluminum AA5182 hood gave the lowest HIC value with 549.70 for HIC15 and 883.00 for HIC36 followed by steel hood with 657.40 for HIC15 and 980.90 for HIC36, e-glass/epoxy composite hood with 639.60 for HIC15 and 921.70 for HIC36 and carbon/epoxy composite hood with 1197.00 for HIC15 and 1424.00 for HIC36.

FOCUS Headform Testing Used to Evaluate Head Injury Risk for Ejected Riders of Personal Watercraft

2017 ◽  
Author(s):  
Chimba Mkandawire ◽  
Eric S. Winkel ◽  
Nicholas A. White ◽  
Edward Schatz
Keyword(s):  
Brain Injury ◽  
Head Injury ◽  
Injury Risk ◽  
Skull Fractures ◽  
Facial Fractures ◽  
Injury Criteria ◽  
Facial Skull ◽  
Personal Watercraft ◽  
Wide Variability ◽  
Head Injury Criteria

Operators of personal watercraft (PWC) can perform maneuvers that may result in riders separating from the moving watercraft; the tested hypothesis was whether substantial brain injury concurrent with substantial facial and skull fractures can occur from contact with the PWC during a fall. The present study reports the potential for AIS2+ facial/skull fractures and AIS2+ traumatic brain injury (TBI) during a generic fall from the PWC in the absence of wave-jumping or other aggressive maneuvers. While it is well known that PWC can be used for wave-jumping which can result in more severe impacts, such impacts are beyond the scope of the present study because of the wide variability in occupant and PWC kinematics and possible impact velocities and orientations. Passenger separation and fall kinematics from both seated and standing positions were analyzed to estimate head impact velocities and possible impact locations on the PWC. A special purpose headform, known as the Facial and Ocular CountermeasUre Safety (FOCUS) device was used to evaluate the potential for facial fractures, skull fractures and TBI. Impacts between the FOCUS headform and the PWC were performed at velocities of 8, 10, and 12 miles per hour at 5 locations near the stern of a PWC. This study reports impact forces for various facial areas, linear and angular head accelerations, and Head Injury Criteria (HIC). The risk for facial fracture and TBI are reported herein. The results of this study indicate that concurrent AIS2 facial fractures, AIS2+ skull fractures, and AIS2+ TBI do not occur during a simple fall from a PWC.

Design and Validation of a Component Head Injury Criteria Tester for Aerospace Applications

2005 ◽  
Author(s):  
Hamid M. Lankarani ◽  
C. S. Koshy ◽  
C. K. Thorbole
Keyword(s):  
Head Injury ◽  
Seat Belt ◽  
Impact Angle ◽  
Head Impact ◽  
Aircraft Cabins ◽  
Aerospace Applications ◽  
Injury Criteria ◽  
Test Conditions ◽  
Head Injury Criteria ◽  
Impact Events

The compliance with Head Injury Criteria (HIC) specified in 14 CFR 23.562 [1] and CFR 25.562 [2] poses a significant problem for many segments of the aerospace industry. The airlines and the manufacturers of jet transports have made claims of high costs and significant schedule overruns during the development and certification of 16G seats because of the difficulties encountered in meeting this requirement. The current practice is to conduct Full Scale Sled Tests (FSST) on impact sleds. This approach can be expensive, since a new seat may be needed for each test. Moreover, some consider the HIC sensitive to changes in the test conditions, such as sled pulse, seat belt elongation, etc., resulting in HIC results from FSSTs showing poor repeatability. These difficulties make it desirable to devise a cheaper, faster, and more repeatable alternative to FSSTs. This paper describes an attempt to address these issues by designing a device, the National Institute for Aviation Research (NIAR) HIC Component Tester (NHCT) using various multibody tools. This device was then fabricated and its performance evaluated against FSSTs conducted under similar test conditions for some typical impact events that occur in an aircraft cabins e.g. impact with bulkheads. The factors compared for this evaluation are the head impact angle, head impact velocity, HIC, HIC window, peak head C.G. resultant acceleration, average head C.G. resultant acceleration, and head C.G. resultant acceleration profiles. The results of these evaluations show that the NHCT already produces test results that correlate significantly with FSST results for impact targets such as bulkheads and its target envelope is expected eventually to include objects such as seat backs.

Determination of Variable Stiffness of a Human Elbow for Human-Robot Interaction

2014 ◽  
Author(s):  
Michael Boyarsky ◽  
Megan Heenan ◽  
Scott Beardsley ◽  
Philip Voglewede
Keyword(s):  
Experimental Data ◽  
Disturbance Rejection ◽  
Variable Stiffness ◽  
Important Variable ◽  
Human Motion ◽  
Human Robot Interaction ◽  
Robot Interaction ◽  
Constant Stiffness ◽  
Stiffness Model ◽  
Motor Model

This paper aims to emulate human motion with a robot for the purpose of improving human-robot interaction (HRI). In order to engineer a robot that demonstrates functionally similar motion to humans, aspects of human motion such as variable stiffness must be captured. This paper successfully determined the variable stiffness humans use in the context of a 1 DOF disturbance rejection task by optimizing a time-varying stiffness parameter to experimental data in the context of a neuro-motor Simulink model. The significant improved agreement between the model and the experimental data in the disturbance rejection task after the addition of variable stiffness demonstrates how important variable stiffness is to creating a model of human motion. To enable a robot to emulate this motion, a predictive stiffness model was developed that attempts to reproduce the stiffness that a human would use in a given situation. The predictive stiffness model successfully decreases the error between the neuro-motor model and the experimental data when compared to the neuro-motor model with a constant stiffness value.

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