scholarly journals Classification of Variable Stiffness Actuators - part 2

2017 ◽  
Vol 21 (2) ◽  
pp. 15-23
Author(s):  
Bartłomiej Kozakiewicz ◽  
Tomasz Winiarski
Keyword(s):  
Variable Stiffness ◽  
Variable Stiffness Actuators

scholarly journals Classification of Variable Stiffness Actuators - part 1

2017 ◽  
Vol 21 (1) ◽  
pp. 41-50
Author(s):  
Bartłomiej Kozakiewicz ◽  
Tomasz Winiarski
Keyword(s):  
Variable Stiffness ◽  
Variable Stiffness Actuators

scholarly journals Robust tracking control for two classes of variable stiffness actuators based on linear extended state observer with estimation error compensation

2020 ◽  
Vol 17 (2) ◽  
pp. 172988142091177
Author(s):  
Jishu Guo ◽  
Junmei Guo ◽  
Zhongjun Xiao
Keyword(s):  
Linear System ◽  
Tracking Control ◽  
Estimation Error ◽  
Input Saturation ◽  
Variable Stiffness ◽  
State Observer ◽  
Extended State Observer ◽  
Extended State ◽  
Linear Extended State Observer ◽  
Variable Stiffness Actuators

In this article, a novel robust tracking control scheme based on linear extended state observer with estimation error compensation is proposed for the tracking control of the antagonistic variable stiffness actuator based on equivalent nonlinear torsion spring and the serial variable stiffness actuator based on lever mechanism. For the dynamic models of these two classes of variable stiffness actuators, considering the parametric uncertainties, the unknown friction torques acting on the driving units, the unknown external disturbances acting on the output links and the input saturation constraints, an integral chain pseudo-linear system with input saturation constraints and matched lumped disturbances is established by coordinate transformation. Subsequently, the matched lumped disturbances in the pseudo-linear system are extended to the new system states, and we obtain an extended integral chain pseudo-linear system. Then, we design the linear extended state observer to estimate the unknown states of the extended pseudo-linear system. Considering the input saturation constraints in the extended pseudo-linear system and the estimation errors of the linear extended state observer with fixed preset observation gains, the adaptive input saturation compensation laws and the novel estimation error compensators are designed. Finally, a robust tracking controller based on linear extended state observer, sliding mode control, adaptive input saturation compensation laws, and estimating error compensators is designed to achieve simultaneous position and stiffness tracking control of these two classes of variable stiffness actuators. Under the action of the designed controller, the semi-global uniformly ultimately bounded stability of the closed-loop system is proved by the stability analysis of the candidate Lyapunov function. The simulation results show the effectiveness, robustness, and adaptability of the designed controller in the tracking control of these two classes of variable stiffness actuators. Furthermore, the simulation comparisons show the effectiveness of the proposed estimation error compensation measures in reducing the tracking errors and improving the disturbance rejection performance of the controller.

scholarly journals Soft Robotics with Variable Stiffness Actuators: Tough Robots for Soft Human Robot Interaction

Soft Robotics ◽  
2015 ◽  
pp. 231-254 ◽  
Author(s):  
Sebastian Wolf ◽  
Thomas Bahls ◽  
Maxime Chalon ◽  
Werner Friedl ◽  
Markus Grebenstein ◽  
...  
Keyword(s):  
Variable Stiffness ◽  
Human Robot Interaction ◽  
Soft Robotics ◽  
Robot Interaction ◽  
Variable Stiffness Actuators
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