Analysis And Design Of The Composite Transmission Of Electro-thermal Shape Memory Alloy And Magneto-rheological Fluid

In the existing study of the magnetorheological transmission device,due to the work process in the excitation coil power loss,the master and slave devices between the high shear,bearing friction and other factors,which will lead to the magnetorheological transmission device in the working state of the environment temperature rising.Thus cause the loss of magnetorheological effect,the shearing force change uncontrollable even transmission efficiency decreased.Therefore,this paper is based on rheological properties of magnetorheological fluid and electro-thermal drive characteristics of shape memory alloys,a composite transmission method of electro-thermal shape memory alloy and magnetorheological fluid is proposed.The use of electro-thermal shape memory alloy spring drives to sense temperature changes,then promote the friction block and the outer cylinder wall are combined to generate friction torque.The loss transmission torque of magnetorheological fluid in high temperature environment is compensated effectively.Through the use of mechanical design methods and electromagnetic field structure simulation technology,the relevant transmission mechanism,transmission performance analysis,transmission device design and related test methods are studied,which provide a theoretical basis for the development of intelligent transmission devices with large transmission torque,wide speed range,reliable operation and variable working temperature.The main research work of this paper is as follows:1)The main material properties,preparation methods and magnetorheological transmission technology of magnetorheological fluid are introduced,and the chain mechanism and rheological properties of magnetorheological fluid under external magnetic field are analyzed,the effects of ambient temperature on the viscosity,yield stress,thermal expansion and shear stress of magnetorheological fluid were studied.2)The principle of electro-thermal shape memory alloy driving technology and the research status at home and abroad are introduced.The output characteristics and design method of the biased shape memory alloy driver are analyzed,and the time response equation of electro-thermal shape memory alloy spring is derived.3)The working principle of electro-thermal shape memory alloy and magnetorheological fluid composite transmission device is analyzed.Respectively,the electro-thermal shape memory alloy spring auxiliary force equation and the disc-type magnetorheological transmission torque equation are derived.The relationship between the transmission torque of the composite transmission and the parameters such as the applied current,the magnetic field strength,the material properties,the rotation speed and the structure size are established.4)According to the transmission principle and transmission equation of composite transmission,this paper designed key geometrical dimensions of the magnetorheological fluid transmission part and the electro-thermal shape memory alloy driving friction block to carry auxiliary transmission part.Combined with the magnetic circuit design method,the simulation and analysis of the magnetic field distribution of the coil internal and external compound transmission device is carried out,Thus the relationship between the excitation coil position,the thickness of the working gap,the master and slave device materials and the magnetic induction intensity is defined.5)The electro-thermal drive performance test experiment of shape memory alloy spring under different current is established,the relationship between the driving force and the applied current and temperature of the electro-thermal shape memory alloy spring is verified,and the time response curve of the electric shape memory alloy spring is obtained.The theoretical calculation is carried out to obtain the torque that can be transmitted by the disc magnetorheological fluid,and the theoretical value is compared with the experimental test value.