Design and implementation of a variable stiffness actuator based on flexible gear rack mechanism

Wang, Wei; Fu, Xiaoyue; Li, Yangmin; Chen, Yun

doi:10.1017/s0263574717000492

Cited by 16 publications

(8 citation statements)

References 37 publications

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“…It uses multiple linear guides in combination with a moving pivot and linear springs to achieve this functionality. Another example of VSA can be found in [20], in which the authors focused on the compactness of the system and obtained a stiffness inversely proportional to the gear displacement. A variable stiffness robotic arm has also been designed [21]: in this case a 7-degrees-of-freedom manipulator takes advantage of VSA to perform different tasks in the SHERPA mission.…”

Section: Introductionmentioning

confidence: 99%

Variable Stiffness Mechanism for the Reduction of Cutting Forces in Robotic Deburring

2021

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One of the main issues related to robotic deburring is that the tool can get damaged or stopped when the burr thickness exceeds a certain threshold. The aim of this work is to devise a mechanism that can reduce cutting forces automatically, in the event that the burr is too high, and is able to return to the baseline configuration when the burr thickness is acceptable again. On the one hand, in normal cutting conditions, the mechanism should have high stiffness to ensure high cutting precision. On the other hand, when the burr is too high the mechanism should exploit its compliance to reduce the cutting forces and, as a consequence, a second cutting cycle will be necessary to completely remove the burr. After the conceptual design of the mechanism and the specification of the desired stiffness curve, the main design parameters of the system are derived thanks to an optimization method. The effectiveness of the proposed mechanism is verified by means of dynamic simulations using selected test cases. A reduction up to 60% of the cutting forces is obtained, considering a steel burr up to 6 mm high.

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Section: Introductionmentioning

confidence: 99%

Variable Stiffness Mechanism for the Reduction of Cutting Forces in Robotic Deburring

2021

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“…7 Inherent mechanical compliance is another major category for addressing the safety issue in pHRI, which can be briefly classified as joint compliance and link compliance. While extensive research has been conducted on the joint compliance, [14][15][16][17][18][19][20][21][22][23][24][25][26][27] relatively less research has been investigated for the link compliance.…”

Section: Introductionmentioning

confidence: 99%

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

She

Song

et al. 2021

Robotica

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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.

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“…In general, VSA with a passive element can be implemented through different actuation methods, namely, antagonistic motor and independent motor setup, as described in [5]. In combination with the actuation method, different stiffness variation method, such as, changing the pretension of the passive element, changing transmission between load and spring (CompAct-VSA [6], AwAS [7], AwAS II [8], vsaUT II [9]), and changing physical properties of the elastic elements (like flexible elements [10], [11] and McKibben [12], [13]) have been employed in the prior art. Some of the notable designs, such as antagonistic springs with antagonistic motors (VSA-II [14], BAVS [15]), antagonistic springs with independent motors (AMASC [16], [17] and [18]), and independent motor for changing the stiffness and equilibrium position (Maccepa [19], Maccepa 2.0 [20], DLR FSJ [21], SVSA [22]) can also be found in the literature.…”

Section: Introductionmentioning

confidence: 99%

Design of a Variable Stiffness Joint Module to Quickly Change the Stiffness and to Reduce the Power Consumption

2020

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Variable stiffness actuators (VSA) are finding wide applications in robotics to enhance safety during interactions with stiff environments. Researchers have proposed various design architectures like antagonistic actuation, which requires both the motors to be powered simultaneously for varying the stiffness or equilibrium position. In this paper, the design of a novel joint module, named as variable stiffness joint module (VSJM), is proposed, which consists of a lead-screw arrangement for varying the stiffness range and a cam based mechanism to change the stiffness within the set range quickly. The cam profile has been synthesized to maximize the stiffness variation as well as to maintain the cam and cam follower in static equilibrium when the output link is in the equilibrium position. This was achieved by properly positioning and orienting the friction cones at the contact points. By mechanically compensating the moment due to unbalanced forces at the contact points, the continuous usage of stiffness motor has been eliminated, leading to reduced power consumption. Details of the proposed mechanism are presented along with the mathematical model for cam profile synthesis and static analysis. A simplified prototype of the proposed design has been fabricated to perform the experiments. A hammering-a-nail experiment has been conducted to show the capability of the mechanism, and the results are presented.

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Design and implementation of a variable stiffness actuator based on flexible gear rack mechanism

Cited by 16 publications

References 37 publications

Variable Stiffness Mechanism for the Reduction of Cutting Forces in Robotic Deburring

Variable Stiffness Mechanism for the Reduction of Cutting Forces in Robotic Deburring

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

Design of a Variable Stiffness Joint Module to Quickly Change the Stiffness and to Reduce the Power Consumption

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