Design of a Quadratic, Antagonistic, Cable-Driven, Variable Stiffness Actuator

Abstract Antagonistically actuated Variable Stiffness Actuators (VSAs) take inspiration from biological muscle structures to control both the stiffness and positioning of a joint. This paper presents the design of an elastic mechanism that utilizes a cable running through a set of three pulleys to displace a linear spring, yielding quadratic spring behavior in each actuator. A joint antagonistically actuated by two such mechanisms yields a linear relationship between force and deflection from a selectable equilibrium position. A quasi-static model is used to optimize the mechanism. Testing of the fabricated prototype yielded a good match to the desired elastic behavior.

Design of a Quadratic, Antagonistic, Cable-Driven, Variable Stiffness Actuator

Volume 10: 44th Mechanisms and Robotics Conference (MR) ◽

10.1115/detc2020-22192 ◽

2020 ◽

Author(s):

Ryan Moore ◽

Joseph M. Schimmels

Keyword(s):

Variable Stiffness ◽

Static Model ◽

Elastic Behavior ◽

Good Match ◽

Linear Spring ◽

Displacement Behavior ◽

Force Displacement ◽

Abstract Antagonistically actuated Variable Stiffness Actuators (VSAs) take inspiration from biological muscle structures to control both the stiffness and positioning of a joint. The design presented utilizes a cable running through a set of three pulleys, to displace a linear spring, yielding quadratic spring behavior. A quasi-static model of the mechanism is used to assess and optimize the force-displacement behavior. The mechanism prototype yielded a good match to the desired elastic behavior.

On a Two-DoF Parallel and Orthogonal Variable-Stiffness Actuator: An Innovative Kinematic Architecture

Robotics ◽

10.3390/robotics8020039 ◽

2019 ◽

Vol 8 (2) ◽

pp. 39 ◽

Cited By ~ 1

Author(s):

Matteo Malosio ◽

Francesco Corbetta ◽

Francisco Ramìrez Reyes ◽

Hermes Giberti ◽

Giovanni Legnani ◽

...

Keyword(s):

Variable Stiffness ◽

Degree Of Freedom ◽

Variable-Stiffness Actuators are continuously increasing in importance due to their characteristics that can be beneficial in various applications. It is undisputed that several one-degree-of-freedom (DoF) solutions have been developed thus far. The aim of this work is to introduce an original two-DoF planar variable-stiffness mechanism, characterized by an orthogonal arrangement of the actuation units to favor the isotropy. This device combines the concepts forming the basis of a one-DoF agonist-antagonist variable-stiffness mechanism and the rigid planar parallel and orthogonal kinematic one. In this paper, the kinematics and the operation principles are set out in detail, together with the analysis of the mechanism stiffness.

Design of a Variable Stiffness Actuator Based on Flexures

Journal of Mechanisms and Robotics ◽

10.1115/1.4004228 ◽

2011 ◽

Vol 3 (3) ◽

Cited By ~ 32

Author(s):

Gianluca Palli ◽

Giovanni Berselli ◽

Claudio Melchiorri ◽

Gabriele Vassura

Keyword(s):

Compliant Mechanism ◽

Variable Stiffness ◽

Human Robot Interaction ◽

Experimental Characterization ◽

Robot Interaction ◽

Trade Off ◽

Robotic Devices ◽

Stiffness Profile ◽

Variable stiffness actuators can be used in order to achieve a suitable trade-off between performance and safety in robotic devices for physical human–robot interaction. With the aim of improving the compactness and the flexibility of existing mechanical solutions, a variable stiffness actuator based on the use of flexures is investigated. The proposed concept allows the implementation of a desired stiffness profile and range. In particular, this paper reports a procedure for the synthesis of a fully compliant mechanism used as a nonlinear transmission element, together with its experimental characterization. Finally, a preliminary prototype of the overall joint is depicted.

Mechanical Simplification of Variable-Stiffness Actuators Using Dielectric Elastomer Transducers

Actuators ◽

10.3390/act8020044 ◽

2019 ◽

Vol 8 (2) ◽

pp. 44 ◽

Cited By ~ 1

Author(s):

David P. Allen ◽

Edgar Bolívar ◽

Sophie Farmer ◽

Walter Voit ◽

Robert D. Gregg

Keyword(s):

Equilibrium Position ◽

Variable Stiffness ◽

Dielectric Elastomer ◽

Design Approach ◽

Electrostatic Forces ◽

Mechanical Stiffness ◽

Variable Stiffness Actuation ◽

And Performance ◽

Variable Stiffness Actuators ◽

Adjustable Compliance

Legged and gait-assistance robots can walk more efficiently if their actuators are compliant. The adjustable compliance of variable-stiffness actuators (VSAs) can enhance this benefit. However, this functionality requires additional mechanical components making VSAs impractical for some uses due to increased weight, volume, and cost. VSAs would be more practical if they could modulate the stiffness of their springs without additional components, which usually include moving parts and an additional motor. Therefore, we designed a VSA that uses dielectric elastomer transducers (DETs) for springs. It does not need mechanical stiffness-adjusting components because DETs soften due to electrostatic forces. This paper presents details and performance of our design. Our DET VSA demonstrated independent modulation of its equilibrium position and stiffness. Our design approach could make it practical to obtain the benefits of variable-stiffness actuation with less weight, volume, and cost than normally accompanies them, once weaknesses of DET technology are addressed.

Proceedings of the 2019 2nd International Conference on Control and Robot Technology ◽

Convex Optimization-based Motion Planner for Linear Variable Stiffness Actuators

10.1145/3387304.3387328 ◽

2019 ◽

Author(s):

Sergei Savin ◽

Svyatoslav Golousov ◽

Alexandr Klimchik

Keyword(s):

Convex Optimization ◽

Variable Stiffness ◽

Feedback Linearization and Disturbance Observer Based Control with Anti-Windup for a Class of Variable Stiffness Actuators Based on Lever Mechanisms

2018 IEEE International Conference on Information and Automation (ICIA) ◽

10.1109/icinfa.2018.8812522 ◽

2018 ◽

Author(s):

Jishu Guo ◽

Guohui Tian ◽

Shaopeng Liu

Keyword(s):

Feedback Linearization ◽

Disturbance Observer ◽

Variable Stiffness ◽

Analysis and synthesis of LinWWC-VSA, a Variable Stiffness Actuator for linear motion

Mechanism and Machine Theory ◽

10.1016/j.mechmachtheory.2016.11.002 ◽

2017 ◽

Vol 110 ◽

pp. 85-99 ◽

Cited By ~ 6

Author(s):

G. Spagnuolo ◽

M. Malosio ◽

T. Dinon ◽

L. Molinari Tosatti ◽

G. Legnani

Keyword(s):

Variable Stiffness ◽

Linear Motion ◽

Analysis And Synthesis ◽

Variable Stiffness Actuator

Dynamic performance analysis of the variable stiffness actuator considering gap and friction characteristics based on two-inertia-system

Mechanism and Machine Theory ◽

10.1016/j.mechmachtheory.2021.104584 ◽

2022 ◽

Vol 168 ◽

pp. 104584

Author(s):

Zemin Yang ◽

Xiaopeng Li ◽

Renzhen Chen ◽

Dongyang Shang ◽

Jinchi Xu ◽

...

Keyword(s):

Performance Analysis ◽

Dynamic Performance ◽

Variable Stiffness ◽

Friction Characteristics ◽

Dynamic Performance Analysis

Realization of an Arbitrary Elastic Behavior With an Elastic Mechanism Having Concurrent Axes

10.1115/imece2000-2393 ◽

2000 ◽

Author(s):

Shuguang Huang ◽

Joseph M. Schimmels

Keyword(s):

Stiffness Matrix ◽

Parallel Mechanism ◽

Elastic Behavior ◽

Unique Point ◽

Compliance Matrix ◽

Elastic Mechanism ◽

Serial Mechanism

Abstract In this paper, synthesis of an arbitrary elastic behavior with an elastic mechanism is addressed. The mechanisms considered are parallel and serial mechanisms with concurrent axes. We show that any stiffness matrix can be realized through a parallel mechanism with all spring axes intersecting at a unique point. This point is shown to be the center of stiffness. We also show that any compliance matrix can be realized through a serial mechanism with all joint axes intersecting at a unique point. This point is shown to be the center of compliance. Synthesis procedures for mechanisms with these properties are provided.

Simultaneous position and stiffness control of a revolute joint using a biphasic media variable stiffness actuator

International Journal of Robotic Computing ◽

10.35708/rc1868-126252 ◽

2019 ◽

Vol 1 (2) ◽

pp. 80-97

Author(s):

Jesus H Lugo

Keyword(s):

Control Method ◽

Variable Stiffness ◽

Industrial Processes ◽

Revolute Joint ◽

Additional Information ◽

Physical Prototype ◽

Stiffness Control ◽

Control Fluid ◽

And Control

Safe interactions between humans and robots are needed in several industrial processes and service tasks. Compliance design and control of mechanisms is a way to increase safety. This article presents a compliant revolute joint mechanism using a biphasic media variable stiffness actuator. The actuator has a member configured to transmit motion that is connected to a fluidic circuit, into which a biphasic control fluid circulates. Stiffness is controlled by changing pressure of control fluid into distribution lines. A mathematical model of the actuator is presented, a model-based control method is implemented to track the desired position and stiffness, and equations relating to the dynamics of the mechanism are provided. Results from force loaded and unloaded simulations and experiments with a physical prototype are discussed. The additional information covers a detailed description of the system and its physical implementation.