Characterization of coiled SMA actuators for humanoid robot

2017 ◽  
Author(s):  
Akshay Potnuru ◽  
Yonas Tadesse
Keyword(s):  
Humanoid Robot ◽  
Sma Actuators

Self-Sensing Control of Antagonistic SMA Actuators Based on Resistance-Displacement Hysteresis Compensation

2020 ◽  
Author(s):  
Johannes Prechtl ◽  
Stefan Seelecke ◽  
Paul Motzki ◽  
Gianluca Rizzello
Keyword(s):  
Smart Materials ◽  
Electrical Resistance ◽  
Pi Controller ◽  
Compensation Scheme ◽  
Position Information ◽  
Remarkable Feature ◽  
Sma Actuators ◽  
Hysteresis Compensation ◽  
Displacement Behavior

Abstract Shape memory alloys (SMAs) are a well-known class of smart materials which allow the design of compact and silent actuation mechanisms. A remarkable feature of SMAs is self-sensing, namely the possibility to reconstruct the actuator position information from electrical resistance measurements. In case of simple SMA actuators, such as spring-loaded wires, the relation between resistance and displacement is usually linear and thus simple to exploit for self-sensing. For more advanced actuator types, such as protagonist-antagonist SMA configurations, the resistance-displacement characteristic is often hysteretic and thus more difficult to invert in real-time. To deal with this issue, this work proposes a novel self-sensing method for protagonist-antagonist SMA actuators having a highly hysteretic resistance-displacement behavior. An online hysteresis compensation scheme, based on the modified Prandtl-Ishlinskii model, is implemented and used to linearize the resistance-displacement characteristic. A lab setup which allows characterization of antagonistic SMA system as well as implementation of self-sensing control architectures is also developed. Experimental results show how, when combined with a PI controller, the developed scheme permits to noticeably reduce the error in comparison to compensator-free self-sensing architectures.

Thermomechanical characterization of high temperature SMA actuators

2006 ◽  
Author(s):  
Parikshith K. Kumar ◽  
Dimitris C. Lagoudas ◽  
Kevin J. Zanca ◽  
Magdalini Z. Lagoudas
Keyword(s):  
High Temperature ◽  
Sma Actuators ◽  
Thermomechanical Characterization

Material Characterization of SMA Actuators Under Nonproportional Thermomechanical Loading

1999 ◽  
Vol 121 (1) ◽  
pp. 75-85 ◽  
Author(s):  
Zhonghe Bo ◽  
Dimitris C. Lagoudas ◽  
David Miller
Keyword(s):  
Phase Transformation ◽  
Active Materials ◽  
Nonproportional Loading ◽  
Thermally Induced ◽  
Sma Actuators ◽  
Niti Sma ◽  
Model Predictions ◽  
Linear Spring ◽  
Constitutive Response

The application of SMA actuators in smart structures usually involves thermally induced phase transformation with a variable applied stress in SMA actuators, resulting in thermomechanical nonproportional loading of SMAs in stress-temperature space. To investigate the constitutive response of SMAs under thermomechanical nonproportional loading, experiments for thermally induced phase transformation of binary NiTi SMA wires loaded by an elastic linear spring are performed in the Active Materials Laboratory at Texas A&M University. A constitutive model developed by Bo and Lagoudas (1998a, b, c) and Lagoudas and Bo (1998) is used as the basis for the theoretical prediction of the response of SMA line actuators loaded by springs with different elastic constants. Model predictions are compared with experimental results.

Humanoid Robot Hand With SMA Actuators and Servo Motors

2014 ◽  
Author(s):  
Lianjun Wu ◽  
Yonas Tadesse
Keyword(s):  
Mathematical Model ◽  
Humanoid Robot ◽  
Flexible Structure ◽  
Human Hand ◽  
Robot Hand ◽  
Real Time Control ◽  
Sma Actuators ◽  
Time Control ◽  
Distal Interphalangeal ◽  
Printing Techniques

This paper describes the design of a child humanoid robot hand with SMA actuators and servo motors. Human hands can grasp and manipulate complicated objects relying on its flexible structure and real-time control. However, it is difficult to replicate an exact human hand using rigid structures because of intricate biomechanical structure. In human hand, one metacarpal and three phalanges make up each finger, except for the thumb which only has two phalanges. Each finger except the thumb is composed of 3 joints: the metacarpophalangeal (MCP), the proximal interphalangeal (PIP) and distal interphalangeal joints (DIP). The DIP and PIP joints are always moving simultaneously, while the MCP joint can move independently. The child-sized robot hand is developed which replicates a seven year-old child’s hand in its fundamental structure. The robot hand has five fingers and all the fingers consist of 3 links. Servo motors and shape memory alloy actuators were used as a drive mechanism for the fingers and mathematical model of the SMA actuators are described to study the finger dynamics. A prototype humanoid robot hand was fabricated using 3D printing techniques and experimental results are presented.

Morphological Characterization of Mycobacteriophage R1

1974 ◽  
Vol 32 ◽  
pp. 254-255
Author(s):  
B. L. Soloff ◽  
T. A. Rado
Keyword(s):  
Carbon Source ◽  
Stationary Phase ◽  
Growth Phase ◽  
Minimal Medium ◽  
Morphological Characterization ◽  
Logarithmic Growth Phase ◽  
Complete Lysis ◽  
Lysogenic Culture ◽  
Logarithmic Growth

Mycobacteriophage R1 was originally isolated from a lysogenic culture of M. butyricum. The virus was propagated on a leucine-requiring derivative of M. smegmatis, 607 leu−, isolated by nitrosoguanidine mutagenesis of typestrain ATCC 607. Growth was accomplished in a minimal medium containing glycerol and glucose as carbon source and enriched by the addition of 80 μg/ ml L-leucine. Bacteria in early logarithmic growth phase were infected with virus at a multiplicity of 5, and incubated with aeration for 8 hours. The partially lysed suspension was diluted 1:10 in growth medium and incubated for a further 8 hours. This permitted stationary phase cells to re-enter logarithmic growth and resulted in complete lysis of the culture.

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