Design of a Continuous Body Hole-Probing Bending Mechanism Driven by Self-Resetting SMA Filaments
A self-resetting bending mechanism driven by a shape memory alloy(SMA)artificial muscle wire is designed for the adaptive bending of hole detector probes.Firstly,the performance test platform of SMA wire is built,and the basic characteristics of SMA wire with a diameter of 0.8 mm is tested under different currents.Secondly,a 4-segment bending mechanism based on SMA wires is designed,its kinematic model is estab-lished,and the bending angle of each segment under the excitation of a single SMA wire is theoretically calcu-lated and tested.Finally,both a single and two SMA wires are energized respectively and then the overall bend-ing angles of the mechanism are tested and compared with its original shape.Additionally,the shape reconstruc-tion of such mechanisms is achieved using a fiber-optic 3D shape sensing system.The results show that:the shrinkage rate of the SMA wire increases from 2.01％to 4.54％,when the current varies from 2.1 to 3.3 A,which increase by 2.26 times.And the restoring stress of the SMA wire is 200 N at a current of 3.3 A.The test results of the bending angles of the joints match well with the theoretical values.The overall bending angle of the mechanism under energization of the two SMA wires can reach up to 114°,which is much larger than the de-flection angle of 65°achieved with a single wire,showing good practicality.
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