Study On Dynamics Of Permanent Magnetic Planetary Gear Drive System

In this paper, a new non-contact drive permanent magnetic planetary gear drive isstudied. Compare with traditional planetary gear drive, the permanent magnetic planetarygear drive has many advantages. The magnetic planetary gear drive does not needlubrication and cooling. It can reduce maintenance and improved reliability. It need lowstarting torque and can offer overload protection. The operating efficiency of the magneticplanetary gear drive is much higher than that of the traditional planetary gear drive. Themagnetic gear drive is without wear and noise.So it can find good application in thetechnical field such as medical apparatus, chemical equipment, food processing equipment,etc.In this paper, the operating principle of the permanent magnetic planetary gear driveis introduced. Relationship between the parameters of transmission system is researchedfrom the condition of concentricity, the condition of adjacency, the condition of the equalpole distance, and the mounting condition of the drive.Using the equivalent current method, the equations of the magnetic inductionintensity for one magnetic gear tooth or multiple magnetic gear teeth are deduced. From it,the equations of the torques between the planetary gears and sun gear or crown gear, andthe equation of the output torque for the drive are developed aswell. The magnetic fluxdensity of the magnetic gear teeth and its distribution are investigated. The torquesbetween the gears and their changes along with the main drive parameters are analysed.Results show that the pole pair number, the tooth thickness, the tooth width, and the speedratio of the drive have obvious influence on the magnetic output torques. Reasonableselection of parameters can make the system structure more compact.The translation-torsion dynamic model for a permanent magnetic planetary geardrive is proposed. Based on the model, the dynamic equations for the permanent magneticplanetary gear drive are given. From the magnetic meshing forces and torques between theelements for the drive system, the tangent and radial magnetic meshing stiffness isobtained. Using these equations, the natural frequencies and the modes of the magnetic planetary gear drive are investigated. The sensitivity of the natural frequencies to thesystem parameters is discussed. Results show that the pole pair number, the tooth width,the air gap and the tooth thickness have obvious effects on the natural frequencies. For theplanetary gear number larger than two, the vibrations of the drive system include thetorsion mode of the center elements, the translation mode of the center elements, and theplanet modes. For the planetary gear number equal to two, the planet mode does not occur,the crown mode and the sun gear mode occur.The forced vibration equation for the permanent magnetic planetary gear drive iseduced. The time and frequency forced responses are computed and analyzed under threekind of condition，only consider the input excitation, only consider output excitation andconsider input excitation and output excitation comprehensively. The influence ofstructure parameters to frequency forced responses is discussed. Results show that thedynamic displacement when only considering output excitation is larger than that whenonly considering input excitation. Magnetization intensity, pole pair number, air gap andaxial thickness have obvious effects on the low frequency vibration amplitude of elements.Selecting rational system structure parameters is very important, which can avoid systemelements generating larger vibration.The experimental prototype of the permanent magnetic planetary gear drive isdesigned, and measure the maximum torque and transmission efficiency. The validity oftheoretical calculation and rationality of parameter design are proved by comparing theexperimental data and theoretical analysis results.