scholarly journals Design of a New Nonlinear Stiffness Compliant Actuator and Its Error Compensation Method

2016 ◽  
Vol 2016 ◽  
pp. 1-8 ◽  
Author(s):  
Shaobin Lan ◽  
Zhibin Song
Keyword(s):  
Error Compensation ◽  
Position Control ◽  
Design Method ◽  
Variable Stiffness ◽  
Compensation Method ◽  
Human Interaction ◽  
Nonlinear Stiffness ◽  
Compliant Actuators ◽  
Compliant Actuator ◽  
Variable Stiffness Actuators

Compliant actuators are more advantageous than stiff actuators in some circumstances, for example, unstructured environment robots and rehabilitation robots. Compliant actuators are more adaptive and safe. Constant stiffness compliant actuators have some limitations in impedance and bandwidth. Variable stiffness actuators improve their performance owing to introducing an extra motor to tune the stiffness of the actuators. However, they also have some limitations such as the bulky structure and heavy weight. It was also found that there are some waste functions existing in the current variable stiffness actuators and that the fully decoupled position control and stiffness tune are not necessary, because there exist some regular phenomena during most circumstances of human interaction with the robots which are “low load, low stiffness and high load, high stiffness”. In this paper, a design method for nonlinear stiffness compliant actuator was proposed which performed the predefined deflection-torque trajectory of the regular phenomenon. A roller and a cantilever which has special curve profile constitute the basic mechanical structure of the nonlinear stiffness compliant actuators. An error compensation method was also proposed to analyze the stiffness of elastic structure. The simulation results proved that the proposed method was effective in designing a predefined nonlinear stiffness compliant actuator.

scholarly journals Dynamic Modeling and Control of Antagonistic Variable Stiffness Joint Actuator

Actuators ◽  
2021 ◽  
Vol 10 (6) ◽  
pp. 116
Author(s):  
Ming Zhang ◽  
Pengfei Ma ◽  
Feng Sun ◽  
Xingwei Sun ◽  
Fangchao Xu ◽  
...  
Keyword(s):  
Dynamic Modeling ◽  
Position Control ◽  
Jacobian Matrix ◽  
Control Method ◽  
Variable Stiffness ◽  
Compliance Control ◽  
Decoupling Method ◽  
Modeling And Control ◽  
And Control ◽  
Variable Stiffness Actuators

This study aims to develop a novel decoupling method for the independent control of the position and stiffness of a variable stiffness joint actuator (VSJA), which has been proven to be able to vary its stiffness in a larger range than other variable stiffness actuators. Using static analysis and the Jacobian matrix, we obtained the model of the stiffness of the robot joint actuator and dynamics. Based on the hybrid dynamic model of position and stiffness, it is possible to compensate for the torque of the variable stiffness joint actuator (VSJA) to enhance position control. Finally, after describing the actuator prototype, the established compliance control method is verified using simulation and experimental analysis.

Design of a Beam-Based Variable Stiffness Actuator via Shape Optimization in a CAD/CAE Environment

2018 ◽  
Author(s):  
Pietro Bilancia ◽  
Giovanni Berselli ◽  
Umberto Scarcia ◽  
Gianluca Palli
Keyword(s):  
Shape Optimization ◽  
Position Control ◽  
Compliant Mechanisms ◽  
Compliant Mechanism ◽  
Design Method ◽  
Variable Stiffness ◽  
Industrial Robots ◽  
Physical Interaction ◽  
Precise Position ◽  
Trivial Shape

Industrial robots are commonly designed to be very fast and stiff in order to achieve extremely precise position control capabilities. Nonetheless, high speeds and power do not allow for a safe physical interaction between robots and humans. With the exception of the latest generation lightweight arms, purposely design for human-robot collaborative tasks, safety devices shall be employed when workers enter the robots workspace, in order to reduce the chances of injuries. In this context, Variable Stiffness Actuators (VSA) potentially represent an effective solution for increasing robot safety. In light of this consideration, the present paper describes the design optimization of a VSA architecture previously proposed by the authors. In this novel embodiment, the VSA can achieve stiffness modulation via the use of a pair of compliant mechanisms with distributed compliance, which act as nonlinear springs with proper torque-deflection characteristic. Such elastic elements are composed of slender beams whose neutral axis is described by a spline curve with non-trivial shape. The beam geometry is determined by leveraging on a CAD/CAE framework allowing for the shape optimization of complex flexures. The design method makes use of the modeling and simulation capabilities of a parametric CAD software seamlessly connected to a FEM tool (i.e. Ansys Workbench). For validation purposes, proof-concept 3D printed prototypes of both non-linear elastic element and overall VSA are finally produced and tested. Experimental results fully confirm that the compliant mechanism behaves as expected.

scholarly journals Design of a Variable-Stiffness Compliant Skin for a Morphing Leading Edge

2021 ◽  
Vol 11 (7) ◽  
pp. 3165
Author(s):  
Zhigang Wang ◽  
Yu Yang
Keyword(s):  
Composite Laminate ◽  
Large Scale ◽  
Design Method ◽  
Leading Edge ◽  
Variable Stiffness ◽  
Manufacturing Constraints ◽  
Aircraft Wing ◽  
Noise Abatement ◽  
Civil Aircraft ◽  
Final Profile

A seamless and smooth morphing leading edge has remarkable potential for noise abatement and drag reduction of civil aircraft. Variable-stiffness compliant skin based on tailored composite laminate is a concept with great potential for morphing leading edge, but the currently proposed methods have difficulty in taking the manufacturing constraints or layup sequence into account during the optimization process. This paper proposes an innovative two-step design method for a variable-stiffness compliant skin of a morphing leading edge, which includes layup optimization and layup adjustment. The combination of these two steps can not only improve the deformation accuracy of the final profile of the compliant skin but also easily and effectively determine the layup sequence of the composite layup. With the design framework, an optimization model is created for a variable-stiffness compliant skin, and an adjustment method for its layups is presented. Finally, the deformed profiles between the directly optimized layups and the adjusted ones are compared to verify its morphing ability and accuracy. The final results demonstrate that the obtained deforming ability and accuracy are suitable for a large-scale aircraft wing.

Control of Vibration Using Compliant Actuators

2017 ◽  
Vol 139 (5) ◽  
Author(s):  
Sannia Mareta ◽  
Dunant Halim ◽  
Atanas A. Popov
Keyword(s):  
Vibration Control ◽  
Active Control ◽  
Passive Control ◽  
Performance Comparison ◽  
Control Performance ◽  
Frequency Bandwidth ◽  
Series Configuration ◽  
Compliant Actuators ◽  
Stiffness And Damping ◽  
Compliant Actuator

This work proposes a method for controlling vibration using compliant-based actuators. The compliant actuator combines a conventional actuator with elastic elements in a series configuration. The benefits of compliant actuators for vibration control applications, demonstrated in this work, are twofold: (i) vibration reduction over a wide frequency bandwidth by passive control means and (ii) improvement of vibration control performance when active control is applied using the compliant actuator. The vibration control performance is compared with the control performance achieved using the well-known vibration absorber and conventional rigid actuator systems. The performance comparison showed that the compliant actuator provided a better flexibility in achieving vibration control over a certain frequency bandwidth. The passive and active control characteristics of the compliant actuator are investigated, which shows that the control performance is highly dependent on the compliant stiffness parameter. The active control characteristics are analyzed by using the proportional-derivative (PD) control strategy which demonstrated the capability of effectively changing the respective effective stiffness and damping of the system. These attractive dual passive–active control characteristics are therefore advantageous for achieving an effective vibration control system, particularly for controlling the vibration over a specific wide frequency bandwidth.

A Maxwell-Slip Based Hysteresis Model for Nonlinear Stiffness Compliant Actuators

2021 ◽  
pp. 1-1
Author(s):  
Weihai Chen ◽  
Libo Zhou ◽  
Jianhua Wang ◽  
Zheng Zhao ◽  
Wenjie Chen ◽  
...  
Keyword(s):  
Nonlinear Stiffness ◽  
Hysteresis Model ◽  
Compliant Actuators
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