| The rotary driving component is a rotary power output unit for drilling and sampling device,and provides enough rotary power for the sampling drill string at the end of system.The rotary driving component is composed of a rotary motor and a planetary transmission component,the planetary transmission component consists of two 2K-H planetary gear systems.The surface environment on the moon is very different from that on the earth,it has the characteristics of high vacuum,strong radiation and large range of temperature.In this paper,the lunar extreme environmental conditions will be aimed at,the planetary transmission component is taken as the research object,temperature rise and dynamic characteriscs considering temperature factors are studied,and the corresponding test verification are carried out.The temperature difference between day and night is above 340 centigrade,and the highest temperature exceeds 160 degrees Celsius.The moon's atmospheric pressure is less than 10-10kPa.The heat generated by the planetary transmission component can only be transmitted through radiation and conduction,the thermal convection can not be realized in the absence of gas medium.Excessive temperature will lead to serious consequences such as lubricant failure,material strength reduction and irreversible damage of electronic components.Considering its structural form,planetary transmission component is a closed structure with a fixed shell.The parts inside rotate around their own axis and center axis,the temperature can not be tested directly.In this paper,a theoretical system for predicting the temperature rise of planetary transmission component will be established by combining theoretical calculation with experimental verification.Firstly,thermal network method is used to calculate the internal temperature rise.two dimensional model of planetary transmission component is simplified,thermal network nodes are divided,and the friction heat source,radiation thermal resistance,conduction thermal resistacne are calculated.The transient heat balance equations are established based on the heat transfer relationships between nodes.The equations are solved by Quasi-Newton method and temperature field and higher temperature rise area in planetary transmission components obtained quickly.Secondly,finite element method is used to calculate the internal temperature rise.A three dimensional model is established in a finite element software.Mesh of the model is divided reasonably according to the calculation results of the thermal network method,locations with higher temperature rise are devided into detailed meshing.The contact surfaces are set and the heat loads are applied at the corresponding positions.Then high efficiency calculation of temperature field in planetary transmission components based on finite element method can be realized.At last,a set of working parameters is introduced,the calculation results of temperature field are predicted.In order to verify the correctness of the theoretical method,a simulated lunar environmental test platform is built based on the high and low temperature vacuum chamber,and 60 contrast tests under different working conditions are carried out.According to the thermal network calculaton results,finite element simulation results and the test results,the correctness of the thermal network method and the accuracy of the finite element method are verified.By comparing the temperature rise of the same nodes in thermal network method with that in the finite element method,the temperature field distribution and heat transfer path are determined.Comparing the results under different working modes,the effects of working speed,working load and ambient temperature on temperature rise can be analyzed,and the calculation model of temperature rise in the highest temperature region is obtained.Finally,the working parameters are introduced,and the internal temperature field is predicted by theoretical method,the working mode is guided and improved based on the calculation results.Based on the combination of theory and experiment,prediction system for temperature field of planetary transmission component can be obtained,the system can guide the practical engineering.When the planetary transmission component works on the moon,the large range of temperature change has significant impact on transmission characteristics.The deformation mechanism of involute cylindrical gear teeth considering temperature is studied,and the polar coordinate parameter equations of actual tooth profile after thermal deformation are obtained.The curves of mesh stiffness and tooth clearance with temperature are obtained.A translational torsional dynamic model has 36 degree of freedom is established,including time-varying meshing stiffness,damping,tooth clearance and errors.A program is written in Matlab software and is used to sovle the system dynamic model,then the natural frequencies and corresponding formations are obtained.The natural characteristic tests are carried out based on the test platform,and the correctness of the theoretical model is verified by comparing the theoretical results with the experimental results.At last,temperature factor is introduced,the narutal frequencies and formations in 300 and-300 degrees Celsius are studied.In order to avoid errors between stiffness and response due to excessive difference of magnitude,dimensionless processing of the established translational torsion dynamic model is carried out.Based on Runge-Kutta method,a program is written to solve the differential equations of motion.Through the displacement of the time domain response,phase diagram,Poincare map of various analytical techniques,the system response characteristics of nonlinear dynamics have been studied.The test platform of planetary transmission component is set up to test the time-domain and frequency-domain characteristics under different working conditions.At last,the influence of meshing stiffness,meshing errors and damping ratio on the dynamic characteristics of system is studied by introducing temperature factors. |
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