Research On Rehabilitation Manipulator And The Electrothermal Driving Characteristics Based On NiTi Shape Memory Alloy

With the accelerating trend of population aging in China,the rehabilitation robotic technology,represented by rehabilitation manipulators,can effectively replace traditional manual rehabilitation training and help patients repair damaged nerves and restore physical functions.The existing rehabilitation manipulators are generally driven by electric motors,hydraulic pressure,and pneumatic pressure,which generally have problems such as complex structure,high weight,high impact force,poor self-adaptation,safety,etc.NiTi Shape memory alloy(SMA)has a unique superelasticity(SE)and shape memory effect(SME),as well as the advantages of a large power-to-weight ratio and high energy density,which is expected to overcome the drawbacks of traditional driving methods and become one of the innovative research directions for future rehabilitative robotic drive devices.This dissertation takes NiTi SMA drive-based rehabilitation manipulator as the research object and NiTi SMA electrothermal driving mechanism research as the core.The key questions such as the preparation of NiTi SMA driving elements,the design of NiTi SMA driving module and the development of NiTi SMA rehabilitation manipulator are focused on.The research is carried out,starting from process selection and drive mechanism research,platform construction and drive performance evaluation,module design and electro-thermal-mechanical characteristics research,prototype development and performance testing.The specific contents of this dissertation are as follows:(1)Research on the laser processing process and performance of NiTi SMA wire.To address the processing defects such as porosity,stress concentration,microcracks,and formation of brittle compounds during laser processing of NiTi SMA,a double-sided laser processing method based on the minimum line energy of NiTi SMA wire is proposed.Parameter optimization of the laser processing process is carried out.The macroscopic morphology,microstructure,phase transformation behavior,mechanical properties,and functional recovery characteristics of the two types of processed samples are studied in detail,and the results show that the double-sided processed samples have better mechanical properties and functional recovery characteristics.The heat treatment technology is used to control and optimize the performance of the NiTi SMA wire doublesided processed samples,and the mechanism of the key factors such as heat treatment temperature,load angle,and excitation current on their electrothermal drive performance is investigated.(2)Research on the heat treatment process and performance of NiTi SMA springs.A cross-scale evaluation method is proposed to design,manufacture,evaluate and improve the driving performance of NiTi SMA springs based on a combination of material intrinsic properties and environmental external factors.The microstructure,phase transformation behavior,and mechanical properties of the prepared NiTi SMA springs are studied from the endogenous dimension based on metallographic analysis.Further,the electrothermal driving performance of NiTi SMA springs is evaluated from the exogenous dimension.The optimal preparation process parameters of NiTi SMA springs are obtained,and the influence mechanism of key factors such as heat treatment temperature,external load,excitation current,tensile length and spring mid-diameter on the electrothermal driving performance is revealed.(3)Design and electrical-thermal-mechanical characteristics of the NiTi SMA drive module.A set of drive module design scheme based on NiTi SMA wire specimens and NiTi SMA spring drive elements is proposed,which can realize the extension and bending functions.Starting from the driving principles of NiTi SMA wire specimens and NiTi SMA springs,the design scheme of two NiTi SMA driving modules,including the working principle,structural design,and fabrication process,is investigated.Further,the electrical-thermal effect simulation,electrical-thermal-mechanical behavior characterization and electrical-thermal-mechanical fatigue performance study of the NiTi SMA drive module are carried out to verify the rationality,safety and reliability of the structural design of the NiTi SMA drive module,so as to lay the foundation for the overall configuration co-design of the NiTi SMA rehabilitation manipulator.(4)Design,development and testing of NiTi SMA drive-based rehabilitation manipulator.The design theory and implementation plan of a modular rehabilitation manipulator based on NiTi SMA actuation are proposed.The design objectives,design principles,design basis,and design process of the NiTi SMA rehabilitation manipulator are established,the key issues in the overall configuration and collaborative design of the rehabilitation manipulator are systematically analyzed,and the overall structural design of the modular rehabilitation manipulator is proposed.Taking the index finger as an example,the 3D design model of the rehabilitation manipulator is proposed,the function,structure,material,manufacture and assembly of each component module are explained,and the kinematic modeling and analysis of the index finger are completed.Based on the proposed test method and experimental platform,the performance tests of key technical indexes such as wearing adaptability,working angle,working frequency,and working driving force of the NiTi SMA rehabilitation manipulator index finger prototype are completed.The results show that the NiTi SMA rehabilitation manipulator is significantly improved in terms of overall weight and maximum working angle.