Force and motion control of a tendon-driven hand exoskeleton actuated by shape memory alloys

2018 ◽  
Vol 45 (5) ◽  
pp. 623-633 ◽  
Author(s):  
Saber Kazeminasab ◽  
Alireza Hadi ◽  
Khalil Alipour ◽  
Mohammad Elahinia
Keyword(s):  
Shape Memory ◽  
Object Manipulation ◽  
Control Algorithms ◽  
Content Type ◽  
Hand Motion ◽  
Sma Actuators ◽  
Force And Motion ◽  
Grasping Force ◽  
Hand Exoskeleton ◽  
Gripping Force

Purpose Many people suffer from injuries related to their hand. This research aims to focus on the improvement of the previously developed smart glove by using position and force control algorithms. The new smart glove may be used for both physiotherapy and assistance. Design/methodology/approach The proposed robot uses shape memory alloy (SMA) actuators coupled to an under-actuated tendon-driven mechanism. The proposed device, which is presented as a wearable glove attached to an actuation module, is capable of exerting extremely high forces to grasp objects in various hand configurations. The device’s performance is studied in physiotherapy and object manipulation tasks. In the physiotherapy mode, hand motion frequency is controlled, whereas the grasping force is controlled in the object manipulation mode. To simulate the proposed system behavior, the kinematic and dynamic equations of the proposed system have been derived. Findings The achieved results verify that the system is suitable to be used as part of a rehabilitation device in which it can flex and extend fingers with accurate trajectories and grasp objects efficiently. Specifically, it will be shown that using six SMA wires with the diameter of 0.25 mm, the proposed robot can provide 45 N gripping force for the patients. Originality/value The proposed robot uses SMA actuators and an under-actuated tendon-driven mechanism. The resulted robotic system, which is presented as a wearable glove attached to an actuation module, is capable of exerting extremely high force levels to grasp objects in various hand configurations. It is shown that the motion and exerted force of the robot may be controlled effectively in practice.

Which impedance strategy is the most effective for cooperative object manipulation?

2017 ◽  
Vol 44 (2) ◽  
pp. 198-209 ◽  
Author(s):  
Payam Zarafshan ◽  
Reza Larimi ◽  
S. Ali A. Moosavian ◽  
Bruno Siciliano
Keyword(s):  
Conceptual Model ◽  
Degrees Of Freedom ◽  
Impedance Control ◽  
Object Manipulation ◽  
Robotic System ◽  
Control Algorithms ◽  
Practical Implementation ◽  
Content Type ◽  
Manipulation Task ◽  
Cooperative Object Manipulation

Purpose The purpose of this paper is to present a comparison study of cooperative object manipulation control algorithms. To this end, a full comprehensive survey of the existing control algorithms in this field is presented. Design/methodology/approach Cooperative manipulation occurs when manipulators are mechanically coupled to the object being manipulated, and the manipulators may not be treated as an isolated system. The most important and basic impedance control (IC) strategies for an assumed cooperative object manipulation task are the Augmented Object Model (AOM) control and the multiple impedance control (MIC) which are found based on the IC, where the former is designed based on the object movement, and the latter is designed based on the whole robot movement. Thus, the basis of these two algorithms are fully studied. Findings The results are fully analyzed, and it is practically verified that the MIC algorithm has the better performance. In fact, the results reveal that the MIC system could successfully perform the object manipulation task, as opposed to the AOM controller: for the same controller gains, the MIC strategy showed better performance than the AOM strategy. This means that because there is no control on the robot base with the AOM algorithm, the object manipulation task cannot be satisfactorily performed whenever the desired path is not within the robot work space. On the other hand, with the MIC algorithm, satisfactory object manipulation is achieved for a mobile robotic system in which the robot base, the manipulator endpoints and the manipulated object shall be moved. Practical implications A simple conceptual model for cooperative object manipulation is considered, and a suitable setup is designed for practical implementation of the two ICs. Originality/value The basis of these two aspects or these two algorithms is fully studied and compared which is the foundation of this paper. For this purpose, a case study is considered, in which a space free-flying robotic system, which contains two 2-degrees of freedom planar cooperative manipulators, is simulated to manipulate an object using the above control strategies. The system also includes a rotating antenna and camera as its third and fourth arm. Finally, a simple conceptual model for cooperative object manipulation is considered, and a suitable setup is designed for practical implementation of the two ICs.

Nonlinear Adaptive Control of Dynamic Systems Driven by Shape Memory Alloy (SMA) Actuators

2008 ◽  
Author(s):  
Shuo Chen ◽  
William J. Craft ◽  
David Y. Song
Keyword(s):  
Shape Memory Alloy ◽  
Shape Memory ◽  
Composite Structures ◽  
Lyapunov Stability Theory ◽  
Linear Displacement ◽  
Control Algorithms ◽  
Sma Actuators ◽  
Composite Systems ◽  
Set Up ◽  
And Control

This work describes the development and analysis of nonlinear adaptive based control algorithms for composite structures/systems operated with Shape Memory Alloy (SMA) actuators. A mathematical model charactering the motion of the composite systems is established, and by using Lyapunov stability theory, algorithms for linear displacement tracking control are derived. Actuation and control is achieved by adjusting the supply current to the SMA actuators. It is shown that with the proposed strategy for both linear displacement and velocity requires that the desired trajectory is tracked precisely. The novelty of the proposed approach also lies in the fact that it is fairly easy to set up and the computation involved as compared with other strategies. An example is used to verify the validity of the proposed approach. Simulation results using Matlab are presented.

Design and Prototyping of a Wearable Assistive Tool for Hand Rehabilitation Using Shape Memory Alloys

2016 ◽  
Author(s):  
A. Hadi ◽  
K. Alipour ◽  
S. Kazeminasab ◽  
A. Amerinatanzi ◽  
M. Elahinia
Keyword(s):  
Shape Memory ◽  
Degrees Of Freedom ◽  
Weight Ratio ◽  
System Optimization ◽  
Human Hand ◽  
Hand Rehabilitation ◽  
Sma Actuators ◽  
Wearable Robots ◽  
Gripping Force ◽  
Opening And Closing

Disability to move hands perfectly is one of the most severe human physical disabilities, and it is mostly common among adults or those who have experienced serious accidents. It is desired to find a methodology to restore the motion of the hand. To this aim, we proposed and evaluated the use of wearable robots (i.e., a smart glove) for clinical therapy that is equipped with shape memory alloy (SMA) actuators. The developed robotic tool, which is a smart glove, uses the structure of human hand as a base mechanism. This glove compensates the weakness of the hand muscles utilizing the forces produced by SMA actuators. The attractive property of high force to weight ratio in SMAs makes this glove a good candidate to be used as a wearable system. The glove actuation mechanism is tendon driven. For every finger, two active Degrees Of Freedom (DOFs) are supported in design. Consequently, four tendons are considered for activating each DOF in order to complete opening and closing phases of the fingers. Totally, twenty tendons are used for rehabilitation of a hand through the glove. Using kinematic relations between tendon length and finger movement, the required deflection of each tendon is extracted. Since a short length of SMA wires cannot provide an enough displacement of tendons in the glove, therefore, an extra mechanism was embedded to the developed glove to support the required length of SMA wires. The SMA actuators were selected and mounted on the system to support the tendons of the mechanism effectively. Moreover, the gripping force provided by the developed glove was also studied. To this end, an analysis was accomplished to extract the relationship between tendon actuation and gripping force of the glove. The obtained results offered a proper model for such a tendon driven glove. Coupling the model of the SMA actuators to that of the tendon driven glove, a composite model of smart glove was extracted. The aforementioned model was simulated numerically. Furthermore, the results were compared with those of the real-world prototype. The obtained results revealed the accuracy of the developed model which will be then employed for both system optimization and model-based control design.

Modeling size-dependent thermal-mechanical behaviors of shape memory polymer Timoshenko micro-beam

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Fei Zhao ◽  
Xueyao Zheng ◽  
Shichen Zhou ◽  
Bo Zhou ◽  
Shifeng Xue
Keyword(s):  
Size Effect ◽  
Shape Memory ◽  
Couple Stress Theory ◽  
Shape Memory Polymer ◽  
Modified Couple Stress Theory ◽  
Mechanical Behaviors ◽  
Equilibrium Equations ◽  
Content Type ◽  
Size Dependent ◽  
Beam Height

PurposeIn this paper, a three-dimensional size-dependent constitutive model of SMP Timoshenko micro-beam is developed to describe the micromechanical properties.Design/methodology/approachAccording to the Hamilton's principle, the equilibrium equations and boundary conditions of the model are established and according to the modified couple stress theory, the model is available to capturing the size effect because of the material length scale parameter. Based on the model, the simply supported beam was taken for example to be solved and simulated.FindingsResults show that the size effect of SMP micro-beam is more obvious when the dimensionless beam height is similar or the larger of the value of loading time. The rigidity and strength of the SMP beam decrease with the increasing of the dimensionless beam height or the loading time. The viscous property of SMP micro-beam plays a more important role with the larger dimensionless beam height. And the smaller the dimensionless beam height is, the more obvious the shape memory effect of the SMP micro-beam is.Originality/valueThis work implies prediction of size-dependent thermo-mechanical behaviors of the SMP micro-beam and will provide a theoretical basis for design SMP microstructures in the field of micro/nanomechanics.

Structural fatigue and fracture of shape memory alloy actuators: Current status and perspectives

2021 ◽  
pp. 1045389X2110572
Author(s):  
Md Mehedi Hasan ◽  
Theocharis Baxevanis
Keyword(s):  
Shape Memory Alloy ◽  
Shape Memory ◽  
Current Status ◽  
Structural Fatigue ◽  
Sma Actuators ◽  
Empirical Relations ◽  
Fatigue And Fracture ◽  
And Performance ◽  
Commercial Applications ◽  
Crack Growth Rates

Shape Memory Alloy (SMA)-actuators are efficient, simple, and robust alternatives to conventional actuators when a small volume and/or large force and stroke are required. The analysis of their failure response is critical for their design in order to achieve optimum functionality and performance. Here, (i) the existing knowledge base on the fatigue and overload fracture response of SMAs under actuation loading is reviewed regarding the failure micromechanisms, empirical relations for actuation fatigue life prediction, experimental measurements of fracture toughness and fatigue crack growth rates, and numerical investigations of toughness properties and (ii) future developments required to expand the acquired knowledge, enhance the current understanding, and ultimately enable commercial applications of SMA-actuators are discussed.

A Multi-Purpose Method for SMA Actuator Development

2013 ◽  
Author(s):  
Sven Langbein ◽  
Alexander Czechowicz
Keyword(s):  
Standardized Testing ◽  
Shape Memory ◽  
Smart Materials ◽  
Research Work ◽  
Simulation Tools ◽  
Sma Actuators ◽  
Shape Memory Actuators ◽  
Computer Aided ◽  
Sma Actuator ◽  
Actual Shape

Shape memory alloys (SMA) are thermally activated smart materials. Due to their ability to change into a previously imprinted actual shape through the means of thermal activation, they are suitable as actuators for mechatronical systems. Despite of the advantages shape memory alloy actuators provide, these elements are only seldom integrated by engineers into mechatronical systems. Reasons are the complex characteristics, especially at different boundary conditions and the missing simulation- and design tools. Also the lack of knowledge and empirical data are a reason why development projects with shape memory actuators often lead to failures. Therefore, a need of developing methods, standardized testing of empirical properties and computer aided simulation tools is motivated. While computer-aided approaches have been discussed in further papers, as well as standardization potentials of SMA actuators, this paper focuses on a developing method for SMA actuators. The main part of the publication presents the logical steps which have to be passed, in order to develop an SMA actuator, considering several options like mechanical, thermal, and electrical options. As a result of the research work, the paper proves this method by one example in the field of SMA-valve technology.

Development of a Shape Memory Alloy (SMA) Based Assistive Hand

2015 ◽  
Vol 1115 ◽  
pp. 454-457 ◽  
Author(s):  
Alala M. Ba Hamid ◽  
Mohatashem R. Makhdoomi ◽  
Tanveer Saleh ◽  
Moinul Bhuiyan
Keyword(s):  
Shape Memory Alloy ◽  
Shape Memory ◽  
Sensory System ◽  
Open Loop ◽  
Rehabilitation Robotics ◽  
Robotic Hand ◽  
After Effect ◽  
Conventional Structure ◽  
Force Mechanism ◽  
Gripping Force

In Malaysia, every year approximately 40000 people suffer from stroke and many of them become immobilized as an after effect. Rehabilitation robotics to assist disabled people has drawn significant attention by the researchers recently. This project also aims to contribute to this field. This paper presents a Shape Memory Alloy (SMA) actuated wearable assistive robotic hand for grasping. The proposed design is compact and sufficiently light to be used as an assistive hand. It is a joint less structure, has the potential because the human skeleton and joint replace the robot’s conventional structure. This design has been implemented on index and thumb fingers to enable grasping. Shape memory alloy springs and bias force mechanism are used for purpose of hand’s flexion and extension. This paper describes the mechatronic design of the wearable hand, experimental study of actuation unit and sensory system. Open loop experiments are conducted to understand the hand characterization and grip force provided by index finger. Current, temperature, extension and contraction of shape memory alloy springs are reported. This mechanism requires approximately 2A current for the SMA to actuate which provides maximum of 1.6N of gripping force. Conducted experiments show promising results that encourage further developments.

Coerced training of the nondominant hand resulting in cortical reorganization: a high-field functional magnetic resonance imaging study

2004 ◽  
Vol 101 (2) ◽  
pp. 310-313 ◽  
Author(s):  
Tsutomu Nakada ◽  
Yukihiko Fujii ◽  
Ingrid L. Kwee
Keyword(s):  
Magnetic Resonance Imaging ◽  
High Field ◽  
Cortical Reorganization ◽  
Functional Magnetic Resonance ◽  
Resonance Imaging ◽  
Content Type ◽  
Hand Motion ◽  
Left Handed ◽  
The Right ◽  
Fine Print

Object. The authors investigated brain strategies associated with hand use in an attempt to clarify genetic and nongenetic factors influencing handedness by using high-field functional magnetic resonance imaging. Methods. Three groups of patients were studied. The first two groups comprised individuals in whom handedness developed spontaneously (right-handed and left-handed groups). The third group comprised individuals who were coercively trained to use the right hand and developed mixed handedness, referred to here as trained ambidexterity. All trained ambidextrous volunteers were certain that they were innately left-handed, but due to social pressure had modified their preferred hand use for certain tasks common to the right hand. Although right-handed and left-handed volunteers displayed virtually identical cortical activation, involving homologous cortex primarily located contralateral to the hand motion, trained ambidextrous volunteers exhibited a clearly unique activation pattern. During right-handed motion, motor areas in both hemispheres were activated in these volunteers. During left-handed motion, the right supplemental motor area and the right intermediate zone of the anterior cerebellar lobe were activated significantly more frequently than observed in naturally right-handed or left-handed volunteers. Conclusions. The results provide strong evidence that cortical organization of spontaneously developed right- and left-handedness involves homologous cortex primarily located contralateral to the hand motion, and this organization is likely to be prenatally determined. By contrast, coerced training of the nondominant hand during the early stages of an individual's development results in mixed handedness (trained ambidexterity), indicating cortical reorganization.

Optimal H∞ Control of Structural Vibrations Using Shape Memory Alloy Actuators

1999 ◽  
Author(s):  
Jian Sun ◽  
Ali R. Shahin
Keyword(s):  
Mathematical Model ◽  
Shape Memory Alloy ◽  
Shape Memory ◽  
Model Uncertainty ◽  
High Frequency ◽  
Structural Vibrations ◽  
Design Procedures ◽  
Sma Actuators ◽  
Temperature Dynamics ◽  
The Mathematical Model

Abstract This paper investigates robust control problem of structural vibrations using shape memory alloy (SMA) wires as actuators. The mathematical model for these SMA actuators is derived with emphasis in model uncertainty. The linearization of the relation between stress and temperature dynamics of SMA actuators is analyzed for active control. To handle the uncertainties caused by the linearization and the neglected high frequency dynamics, optimal H∞ control was employed to design a controller. An example is used to demonstrate the design procedures and the control system is tested in a nonlinear environment.

Shape Memory Alloys in Automotive Applications

2014 ◽  
Vol 663 ◽  
pp. 248-253 ◽  
Author(s):  
Jaronie Mohd Jani ◽  
Martin Leary ◽  
Aleksandar Subic
Keyword(s):  
Shape Memory Alloy ◽  
Shape Memory Alloys ◽  
Shape Memory ◽  
External Force ◽  
Active Element ◽  
Mechanical Design ◽  
Competitive Market ◽  
Automotive Applications ◽  
Market Prices ◽  
Sma Actuators

Shape memory alloy (SMA) actuators have drawn much attention and interest due to their unique and superior properties, and are expected to be equipped in many modern vehicles at competitive market prices. The key advantage is that SMA actuators do not require bulky and complicated mechanical design to function, where the active element (e.g. SMA wire or spring) can be deformed by applying minimal external force and will retain to their previous form when subjected to certain stimuli such as thermomechanical or magnetic changes. This paper describes the SMA attributes that make them ideally suited as actuators in automotive applications and to address their limitations, feasibilities and prospects.

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