Design And Experimental Study Of Magneto-rheological Fluid Transmission For Compliant Joints

The traditional rigid robot and software robot respectively solve the problem of security in human-robot interaction and the work precision of the robot itself.The research of flexible joints in robot work makes the two requirements of the robot meet at the same time.In view of the smaller output force and torque of the last generation of compliant joints,it is important to develop a multi disc magnetorheological fluid transmission.Magnetorheological fluid(MRF)is a kind of intelligent material change characteristics in the field of magnetic field with phase.The viscosity can be changed continuously in several milliseconds with the change of the applied magnetic field.In this paper,a robot compliant joint based on magnetorheological fluid is proposed,and a magnetorheological transmission device is designed.The main contents are as follows:(1)A flexible joint based on multi disk magnetorheological(MRF)is proposed.The magnetorheological transmission is embedded in the joint of a rigid robot.The flexibility of the joint is guaranteed by the variable stiffness transmission mode,and the output strength and safety are guaranteed from the single disk to multi disk lift.(2)The force model of magnetic particles in magnetorheological fluid transmission is analyzed,and the macro shear model of magnetorheological fluid is established from microscopic view by interaction force between particles.The control mechanism of compliant joints in MRF is studied.The speed control model is established by using the magnetorheological fluid constitutive model,the fitting parameters of magnetorheological fluid test,the flux calculation model and the torque transfer model.(3)In order to ensure the output strength,the maximum torque of the target is set to 5N·m.A magnetorheological fluid transmission device is designed,as well as the magnetic circuit.The influence of the parameters in the torque transfer model is simulated by Matlab,and the optimal parameters are selected according to the actual situation.The electromagnetic field strength of the device working gap is analyzed by electromagnetic simulation software Maxwell.According to the simulation results,the optimal parameters are obtained to process the prototype.The simulation results show that the magnetic field strength can reach 0.3T.(4)MRF compliant joint prototype is processed according to different surface roughness and surface texture of torque transmission.The experimental platform of MRF compliant joint transmission is built and experiments were done to analyze the characteristic of magnetorheological fluid transmission device.The experimental results show that the rougher the surface roughness is,the greater the torque can be transmitted,and the different textures also have a certain influence on the torque transfer.The output of the magnetorheological fluid transmission is stable and fast response,and it can be controlled stepless.The magnetorheological fluid transmission device can effectively ensure the accuracy of joint operation and meet the requirements of the design.