• Transactions of the Korean Society of Mechanical Engineers B
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• v.35 no.12
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• pp.1301-1307
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• 2011

Electrosurgical knee wand (EKW) is a high-frequency thermocautery instrument and is often used for coagulation, ablation, excision, and extirpation of knee ligaments and tissues. In order to maximize the success rate, ease, and safety of knee surgery using EKW and radiofrequency ablation, it is necessary to ensure that the EKW selectively approaches the lesion with utmost accuracy and safety. The key feature of this instrument is its excellent maneuverability. Hence, the authors constructed a tensile spring model based on a shape memory alloy (SMA), which exhibits the shape memory effect. This model can be used in knee surgery as it is considered the most biocompatible femorotibial surgical actuator. The changes in external temperature with current and the thermoelectric characteristics of the SMA were investigated. The relationship between the restoring force and the typical stroke (TS) in response to the conditions in the SMA tensile spring design were evaluated. In conclusion, as the diameter of the SMA tensile spring decreased, the maximum temperature increased. The strain in the actuator caused a stable and proportional increase in the force and induced current for up to 15s, but this increase became very unstable after 30s. Moreover, the relationship between the current and the TS was more stable than that between the current and the restoring force.

• Proceedings of the KSME Conference
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• 2000.04a
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• pp.556-561
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• 2000

This paper deals with the control of an active bending actuator fur a catheter. The bending actuator with 40mm in length utilizes three zigzag SMA (shape memory alloy) springs which are equally located in the circumference between inner $({\phi}2.5 mm)$ and outer $({\phi}3.0mm)$ tube. It is purposed on realization of desired bending angle $(90^{\circ})$ and direction $(360^{\circ})$. It is also installed in front of the catheter and used to guide a path at extremely bent or branched blood vessel. The performance-analysis of the bending actuator are investigated fur the purpose of optimizing the control of the bending actuator. The analog joy stick is used to command a bending angle and direction for the fast and accurate response. According to the commands of the joy stick, tensile force of each SMA spring is computed and obtained by controlling the temperature of each SMA spring using PWM (pulse width modulation) of supplied electric power.

• Composites Research
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• v.22 no.2
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• pp.37-42
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• 2009

This paper presents an experimental approach to design a bending-type actuator by using a shape memory alloy wire (SMA), composite strip, and spring. The SMA wire is attached to two edges of the bent strip to apply pre-stress to the SMA wire. The spring is used to provide recovery force right after actuation of the SMA wire. To investigate thermo-mechanical characteristics of the SMA wire, a series of DSC tests have been conducted and tensile tests under various levels of pre-stress and input power have been performed. Based on the measured properties of the SMA wire, bending-type actuators are designed and tested for different combination of strip, number of springs, and input power. It has been found that a bending-type actuator with a proper combination shows fast actuation performance and low power consumption.