Jangid, P and Botre, BA and Singh, S and Bhargav, HN and Akbar, SA
(2019)
Development of Controlled Current Heating Module and
Measurement System for Shape Memory Alloy.
In: 4th International Conference on Emerging Technologies: Micro to Nano (ETMN-2019), December 16-17, 2019, Pune, India.
Abstract
Shape Memory Alloys (SMAs) are a unique class of materials that have the ability to recover their shape when the temperature is increased. It has significant potential in many areas such as aerospace, biomedical, automobile, vibration-dampers, etc. In these applications, light weight SMA element can be used in place of bulky motor driven systems for making linear as well as angular movements. SMA can he electrically activated to produce joule heating which triggers a phase transformation in the SMA wire causing it to expand and contract, Right configuration of these wires can be utilized to form an alternative to the motors and solenoids to provide an actuation signal. It provides potentially simple, silent and smooth operation and auto sensing ability thereby providing a controlled displacement that can be utilised to generate mechanical work. To attain repetitive and desired displacement, the SMA element needs to be properly biased at the end of each heating-cooling cycle. For such phase transformation of these SMAs, the appropriate healing module is required for the precise movement of the wire. Due to phase transformation in SMA wires, the resistance of SMA wires changes significantly. For the usage of data driven control and self-sensing SMA devices, precise measurement of different data parameters, like, voltage (VSMA), current (ISMA), ambient temperature (Ta), wire temperature (TSMA), displacement (D), and resistance (RSMA) are required. These parameters can be used further to derive the relationship between difference resistance. (dR) and displacement. dR is the difference between resistances of two SMA wires.
The present work details current controlled heating module (CCHM) and measurement system for SMA wire. CCHM consists of PWM generation using PC, low pass filter (LPF), operational amplifier with appropriate feedback for the controlling the current. This CCHM provides the appropriate current needed to operate the SMA movement. The measurement system incorporates the precise measurement of voltage. current and ambient temperature and displacement. Thermocouple sensors are used to measure the temperature of the SMAs. Filtering and signal processing needed for these parameters are studied and discussed in the present article. Performance analysis of heating module & measurement system is carried out and their results are reported.
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