SHAPE MEMORY ALLOY BASED MICRO-MESO SCALE MANIPULATOR

Kostyantyn Malukhin

doi:https://doi.org/10.21985/N20F1C

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SHAPE MEMORY ALLOY BASED MICRO-MESO SCALE MANIPULATOR

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The need for low-cost robust meso-scale "smart" robots (manipulators) that have no discrete parts (monolithic), no sensors ("self-sensing") and can be used in space-constrained systems, e.g., in microfactories, biomedical applications, etc., was the motivation for the current research. This study describes the design, fabrication and analysis of such a smart robot - a monolithic Micro/Meso Scale Manipulator (mMM), fabricated from Shape Memory Alloy powders (NiTi) by means of the laser-based Direct Metal Deposition (DMD) process. A first prototype, a functional part of the mMM - a SMA accordion spring type actuator was manufactured by DMD. The actuator provides a linear movement for the mMM due to the Shape Memory Effect (SME) property of SMAs. The One-Way SME was imposed on the spring actuator by a series of thermomechanical treatments. The SME drives the spring's movements due to the property of the SMAs to change their crystallographic structure and, therefore, shape, during heating or cooling. The characterization of the DMD manufactured material was done. SMAs change their crystallographic structure and/or shape (SME) when the phase transformation takes place in the material during its temperature and/or stress state change. A new mathematical model describing the phase transformation kinetics and a new analytical phase transformation function was developed. The phase transformation in SMAs causes electrical resistance change in the material. The motion, caused by the SME, can be controlled using the electrical resistance change as a feedback signal with no need for separate motion sensors. In the current work this "self-sensing" concept was explored and evaluated in an SMA wire based actuator and applied to the SMA spring based actuator. The dynamics of the sub-millimeter and millimeter scale motion of the SMA actuators was identified using physical models of the SMA wire based actuators. A new mathematical model of the motion of the SMA wire- and spring-based actuators was developed. It is planned to use the model of motion in the corresponding model of motion control of the actuators. An advanced prototype of the previously described SMA spring actuator was manufactured from a commercially available SMA (NiTi) ingot to experimentally verify the models of motion.

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