Electro-Thermo-Mechano-Magneto Characteristics of Shape Memory Spring Actuator/Sensor in Assistive Devices
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In recent years, shape memory alloys (SMAs) have been used widely as actuators in modern systems but it can also be used as sensor since it offers unique self-sensing property. Shape memory alloys exhibit parameter variations that include electrical properties such as resistance in case of SMA wire and impedance in case of SMA spring, as a nonlinear hysteretic behavior within a transformation cycle. The actuation and sensing characteristics of SMA can be obtained from the material’s electromechanical impedance. This work presents about the electro-thermo-mechano-magneto effects exhibited in commercially available NiTiNOL spring with 90 °C phase transition temperature during phase transformation. The phase-dependent electrical resistance, inductance, impedance, and magnetic field of the SMA spring is measured using impedance analyzer and milli gauss meter respectively. The results opens the door to a new dimension of application of SMA spring, i.e., the investigation explores a possibility for the design of electro-thermo-mechano-magneto characteristics based assistive systems and in robotics.
KeywordsNiTi spring Joule heating Temperature Displacement Force Magnetic field Electrical resistance Series inductance Duty cycle
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