Active stiffness control of a synergistically operated variable stiffness compliant actuator

2021 ◽  
Vol 43 (2) ◽  
Author(s):  
D. Nalini ◽  
K. Dhanalakshmi
Keyword(s):  
Variable Stiffness ◽  
Stiffness Control ◽  
Compliant Actuator

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

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 ◽  
Variable Stiffness Actuator ◽  
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.

Variable stiffness control of series elastic actuated biped locomotion

2018 ◽  
Vol 11 (3) ◽  
pp. 225-235 ◽  
Author(s):  
Jianwen Luo ◽  
Shuguo Wang ◽  
Ye Zhao ◽  
Yili Fu
Keyword(s):  
Variable Stiffness ◽  
Biped Locomotion ◽  
Stiffness Control ◽  
Series Elastic

Variable stiffness control for SEAs in rehabilitation training

2019 ◽  
Vol 33 (7-8) ◽  
pp. 424-438 ◽  
Author(s):  
Siqi Li ◽  
Jian Li ◽  
Guihua Tian ◽  
Hongcai Shang
Keyword(s):  
Variable Stiffness ◽  
Rehabilitation Training ◽  
Stiffness Control

Smart variable stiffness control systems

2001 ◽  
Author(s):  
Satish Nagarajaiah ◽  
Nadathur Varadarajan
Keyword(s):  
Control Systems ◽  
Variable Stiffness ◽  
Stiffness Control

A Novel Compliant Actuator With Load-Dependent Variable Stiffness: Design Concept and Control

2016 ◽  
Author(s):  
Lu Lu ◽  
Jiawei Li ◽  
Cong Wang ◽  
Dan Strassberg
Keyword(s):  
Motion Control ◽  
External Load ◽  
Load Condition ◽  
Variable Stiffness ◽  
Design Concept ◽  
Inertia Force ◽  
Precision Motion Control ◽  
Precision Motion ◽  
And Control ◽  
Compliant Actuator

To develop the next generation of high-performance robots capable of working in human environments, it is required that the joint actuators have variable stiffness to achieve both precision motion control and ability of reaction under unexpectedly huge impact caused by collision with obstacles or human. Variable stiffness actuators (VSA) partially realize such objectives by employing an auxiliary input to change the joint stiffness. However, it requires prior information of external load condition. Load sensors or online load estimation techniques need to be implemented to detect sudden unexpected load for stiffness adjustment, adding complexity to the system with bandwidth issues. In this paper, we propose a new design of compliant actuator in which the stiffness automatically varies depending on the unexpected external load. A novel doubly-clamped box structure is used to connect the load inertia to the motor inertia. Specifically, the load inertia is confined inside a box clamped by two stoppers on two opposite sides with two pre-compressed springs. A secondary motor connects to the load inertia through another spring, compensating for known unbalanced forces such as gravity, Coriolis force and inertia force. It is shown that if the unexpected external load force is below the pre-compression force of the springs, the load inertia will be confined exactly within the box and the system behaves like a rigid actuator, otherwise one of the springs will be further compressed and the system behaves like a compliant actuator. Such a mechanical structure has the ability of achieving both precision motion control and automatic reaction under unexpectedly huge external impact, without the need of additional load sensing/estimation. Control algorithms for accurate position tracking under potentially huge unexpected load is developed for this new type of actuator. Simulations are conducted to verify the effectiveness of the design concept and control.

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