Experimental investigations for the characterisation of an SMA-bias spring actuator in a flexible tube manipulator

The present article describes an application of shape memory alloy (SMA) spring-based actuator for the development of a flexible tube manipulator intended for tumour irradiation application. A constitutive model is proposed that incorporates the nonlinearity of SMA spring along with the loading history of material and predicts 4 N as the force generation capability of the SMA-bias spring actuator. The simulation results follow the characteristic profile of SMA in both normal as well as cyclic loading conditions. Further, experimental characterisation of the actuator is carried out to determine various parameters like modulus of rigidity, critical shear stresses, etc. and a proportional integral derivative (PID) controller is experimentally implemented which made the tip of the tube following a series of predefined points. The maximum positional error is around 5%, which shows the positional tracking ability of the developed manipulator and the maximum bending angle of the tube is 74.6°.