1 Mavroidis-1 DESIGN AND DYNAMICS OF A SHAPE MEMORY ALLOY WIRE BUNDLE ACTUATOR Michael J. Mosley 1 , Constantinos Mavroidis 2 and Charles Pfeiffer 3 Department of Mechanical and Aerospace Engineering, Rutgers University, The State University of New Jersey 98 Brett Rd., Piscataway, NJ 08854-8058 [email protected], [email protected] , [email protected] Tel: 732 - 445 – 0732, Fax: 732 - 445 - 3124 ABSTRACT In this paper, the design and dynamics of a new Shape Memory Alloy (SMA) actuator that possesses impressive payload lifting capabilities are presented. This actuator consists of 48 SMA wires mechanically bundled in parallel forming one powerful muscle. The new actuator can lift up to 100 lbs., which is approximately 300 times its weight. This actuator was tested in open loop experiments with different weights and different inputs, such as step, ramp, sinusoid, and half sinusoid, and its dynamic characteristics were evaluated. Of special importance is the observed unpredictability of the actuator's response when low voltages are applied. This characteristic suggests possible chaotic behavior of the actuator, potentially causing control difficulties in fine and high accuracy tasks. 1. Introduction Robotic systems have been proposed to perform important tasks in the nuclear industry such as hazardous waste removal and decommissioning of nuclear sites [1, 2]. Since these tasks occur in a highly radioactive environment, robotic and other automated systems are required to reduce worker exposure to radiation. Robots operating in these remote and hazardous conditions must have a high weight lifting capability and be able to cover a large workspace. At the same time, they must be lightweight for easy transportation and dexterous enough to move in a cluttered environment. However, existing robotic systems for macro manipulation are characterized by poor payload to weight ratio and are cumbersome and voluminous. The objective of this research is to develop a new generation of large-scale robotic manipulators that are strong, lightweight, compact, and dexterous. The key methodology in drastically reducing the weight of the manipulator is the use of Shape Memory Alloy (SMA) wires as actuators of the manipulator joints. In this paper, the design of a new SMA actuator is presented that possesses impressive payload capabilities. Shape memory alloy wires, such as Nickel-Titanium (Ni-Ti) wires, have the property of shortening when heated and thus are able to apply forces. This phenomenon, called the "shape memory effect,” occurs when the material is heated above a certain transition temperature changing its phase from martensite to austenite. Heating, and thus actuation, of an SMA wire is easily accomplished by 1 Graduate Student 2 Assistant Professor, Author for Correspondence 3 Research Engineer
DESIGN AND DYNAMICS OF A SHAPE MEMORY ALLOY WIRE BUNDLE ACTUATOR
Jun 24, 2023
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