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.

A Parametric Study of Compliant Link Design for Safe Physical Human–Robot Interaction

Robotica ◽  
2021 ◽  
pp. 1-21
Author(s):  
Yu She ◽  
Siyang Song ◽  
Hai-jun Su ◽  
Junmin Wang
Keyword(s):  
Theoretical Model ◽  
Parametric Study ◽  
Impact Force ◽  
Safety Issue ◽  
Design Guidelines ◽  
Human Robot Interaction ◽  
Robot Dynamics ◽  
Mechanical Compliance ◽  
Safety Constraints ◽  
The Impact

SUMMARY Robots of next-generation physically interact with the world rather than be caged in a controlled area, and they need to make contact with the open-ended environment to perform their task. Compliant robot links offer intrinsic mechanical compliance for addressing the safety issue for physical human–robot interactions (pHRI). However, many important research questions are yet to be answered. For instance, how do system parameters, for example, mechanical compliance, motor torque, impact velocities, and so on, affect the impact force? how to formulate system impact dynamics of compliant robots, and how to size their geometric dimensions to maximize impact force reduction. In this paper, we present a parametric study of compliant link (CL) design for safe pHRI. We first present a theoretical model of the pHRI system that is comprised of robot dynamics, an impact contact model, and dummy head dynamics. After experimentally validating the theoretical model, we then systematically study the effects of CL parameters on the impact force in more detail. Specifically, we explore how the design and actuation parameters affect the impact force of pHRI system. Based on the parametric studies of the CL design, we propose a step-by-step process and a list of concrete guidelines for designing CL with safety constraints in pHRI. We further conduct a simulation case study to validate this design process and design guidelines.

scholarly journals V2SOM: A Novel Safety Mechanism Dedicated to a Cobot’s Rotary Joints

Robotics ◽  
2019 ◽  
Vol 8 (1) ◽  
pp. 18 ◽  
Author(s):  
Younsse Ayoubi ◽  
Med Laribi ◽  
Said Zeghloul ◽  
Marc Arsicault
Keyword(s):  
Good Control ◽  
Variable Stiffness ◽  
Human Robot Interaction ◽  
Industrial Robots ◽  
Necessary Condition ◽  
Physical Interaction ◽  
Robot Interaction ◽  
Internal Damage ◽  
Low Stiffness ◽  
The Impact

Unlike “classical” industrial robots, collaborative robots, known as cobots, implement a compliant behavior. Cobots ensure a safe force control in a physical interaction scenario within unknown environments. In this paper, we propose to make serial robots intrinsically compliant to guarantee safe physical human–robot interaction (pHRI), via our novel designed device called V2SOM, which stands for Variable Stiffness Safety-Oriented Mechanism. As its name indicates, V2SOM aims at making physical human–robot interaction safe, thanks to its two basic functioning modes—high stiffness mode and low stiffness mode. The first mode is employed for normal operational routines. In contrast, the low stiffness mode is suitable for the safe absorption of any potential blunt shock with a human. The transition between the two modes is continuous to maintain a good control of the V2SOM-based cobot in the case of a fast collision. V2SOM presents a high inertia decoupling capacity which is a necessary condition for safe pHRI without compromising the robot’s dynamic performances. Two safety criteria of pHRI were considered for performance evaluations, namely, the impact force (ImpF) criterion and the head injury criterion (HIC) for, respectively, the external and internal damage evaluation during blunt shocks.

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 Toward Tradeoff Between Impact Force Reduction and Maximum Safe Speed: Dynamic Parameter Optimization of Variable Stiffness Robots

2020 ◽  
Vol 12 (5) ◽  
Author(s):  
Siyang Song ◽  
Yu She ◽  
Junmin Wang ◽  
Hai-Jun Su
Keyword(s):  
Performance Measures ◽  
Impact Force ◽  
Variable Stiffness ◽  
Dynamic Parameter ◽  
Human Robot Interaction ◽  
Maximum Speed ◽  
Performance Indices ◽  
Global Performance ◽  
Force Reduction ◽  
The Impact

Abstract Variable stiffness robots may provide an effective way of trading-off between safety and speed during physical human–robot interaction. In such a compromise, the impact force reduction capability and maximum safe speed are two key performance measures. To quantitatively study how dynamic parameters such as mass, inertia, and stiffness affect these two performance measures, performance indices for impact force reduction capability and maximum speed of variable stiffness robots are proposed based on the impact ellipsoid in this paper. The proposed performance indices consider different impact directions and kinematic configurations in the large. Combining the two performance indices, the global performance of variable stiffness robots is defined. A two-step optimization method is designed to achieve this global performance. A two-link variable stiffness link robot example is provided to show the efficacy 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 Experimental Study of the Debris Flow Slurry Impact and Distribution

2018 ◽  
Vol 2018 ◽  
pp. 1-15 ◽  
Author(s):  
Haixin Zhao ◽  
Lingkan Yao ◽  
Yong You ◽  
Baoliang Wang ◽  
Cong Zhang
Keyword(s):  
Debris Flow ◽  
Debris Flows ◽  
Impact Force ◽  
Influence Factors ◽  
Flume Experiment ◽  
Middle Point ◽  
Laboratory Flume ◽  
Critical Issues ◽  
Maximum Impact Force ◽  
The Impact

In this study, we present a new method to calculate debris flow slurry impact and its distribution, which are critical issues for designing countermeasures against debris flows. There is no unified formula at present, and we usually design preventive engineering according to the uniform distribution of the maximum impact force. For conducting a laboratory flume experiment, we arrange sensors at different positions on a dam and analyze the differences on debris flow slurry impact against various densities, channel slopes, and dam front angles. Results show that the force of debris flow on the dam distributes unevenly, and that the impact force is large in the middle and decreases gradually to the both sides. We systematically analyze the influence factors for the calculation of the maximum impact force in the middle point and give the quantitative law of decay from the middle to the sides. We propose a method to calculate the distribution of the debris flow impact force on the whole section and provide a case to illustrate this method.

scholarly journals Numerical research on impact performance of bridge columns with aluminum foam protection devices

2020 ◽  
Vol 16 (11) ◽  
pp. 155014772097453
Author(s):  
Yuye Zhang ◽  
Ruiyang Pan ◽  
Feng Xiao
Keyword(s):  
Aluminum Foam ◽  
Maximum Stress ◽  
Impact Force ◽  
Bridge Columns ◽  
Design Parameters ◽  
Protection Device ◽  
Impact Performance ◽  
Positive Effects ◽  
Protection Capability ◽  
The Impact

This article presents a new protection device using aluminum foam to enhance the impact resistance of bridge columns. First, the protection device is designed according to the characteristics of aluminum foam material. The geometric configuration and structure of the device are described. Second, the impact performance of bridge column is analyzed, including impact force analysis, damage analysis, and the influence of axial load. Third, three-dimensional solid element models of columns with and without the protection device are developed in order to verify the effect of the protection device. By comparing dynamic responses of vehicle impact on columns with and without the protection device, it is considered that the protection device has certain protection effect: after installing the protective device, the peak value of impact force reduces by 37.5%, the maximum displacement of column top reduces by 23.7%, the maximum stress at column bottom reduces by 51.6%, the maximum stress at column bottom reduces by 51.6%, the maximum acceleration of the vehicle reduces by 40.6%, and 86.84% of the impact energy is absorbed by the protection device. Finally, the devices with different foam thicknesses and porosities are comparatively analyzed to investigate the influence of these design parameters on impact performance. The results show that the increase in the thickness of aluminum foam has positive effects on the protection capability. The protection capability improves with aluminum foam porosity increasing when the porosity is less than 60%.

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.

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