| Traffic accidents and natural disasters occur every year around the world.These unpredictable accidents have caused many people to be physical disabled,and lower limb knee amputation accounts for a large part of amputees.However,scholars’ research on medicine and biology has not regenerated the limbs.Therefore,artificial limbs have become an important tool for lower limb amputators to return to society.The magnetorheological damper has the advantages of good flexibility,simple and stable structure,and can output a continuously controllable damping force at low power,which has made more and more researchers pay attention to its prospects in the prosthetic knee joint.At present,in the existing research,the magnetorheological damper in the knee joint of the magnetorheological prosthesis is large and bulky,whose gait recognition can’t be realize and wearer comfort can’t be guaranteed,which makes the magnetorheological prosthesis knee joint still far from commercialization.Therefore,it is of great scientific significance and application value to develop one magnetorheological damper highly adapted to the knee joint of artificial limbs.In this paper,a new type of micro-nano magnetorheological fluid with better performance is developed by adding nanomagnetic particles to the traditional micron magnetorheological fluid,and a damping force test system was built to test the micro-nano magnetorheological fluid damping performance and saturation magnetic field strength.Based on the actual application standard of the prosthetic knee joint and the working mode of the magnetorheological damper,the structural design and magnetic circuit design of the magnetorheological damper are carried out,and the micro-nano magnetorheological fluid damper for the knee joint of the artificial limb is developed.A multi-objective genetic algorithm(NSGA II)is proposed to optimize the volume and power consumption of micro-nano magnetorheological fluid dampers.The multi-objective optimized damper parameters are obtained through the gamultiobj function in Matlab.The model is established based on the optimized size parameters of the micro-nano magnetorheological fluid damper,and ANSYS is used to simulate the internal magnetic field of the working gap of the damper under different currents,which verifies the rationality of the distribution of magnetic induction lines inside the damper,and obtains the relationship between the magnetic induction intensity and current in the working gap.The performance test platform of the micro nano MR fluid damper is built.The damping force of the damper under different current and different temperature is tested and analyzed.The relationshipcurve of the damping force with the change of current and temperature is obtained.The performance test platform of micro-nano magnetorheological fluid damper is built to test the relationship between the damping force with different currents and different temperatures.It shows that the actual output damping of the developed micro-nano damper meets the design requirements,which lays a research foundation for the subsequent control recognition to improve the gait quality. |
