Design Of 3-DOF Landing Lighting System Based On Pan Tilt Structure

Landing lighting system is an important subsystem of helicopter,which is an essential airborne equipment for helicopter to complete flight operation.The performance of landing lighting system directly determines the landing speed of military helicopter and whether it can land smoothly in complex environment.At the same time,the landing lighting system as the helicopter external lighting equipment,due to wind resistance,external vibration and other loads,the working environment is very bad,which puts forward high requirements for the structural strength of the landing lighting system itself.There are design defects in the structure of the landing lighting system which needs to be optimized in the subject.According to the feedback from the helicopter driver during actual operation,the landing lighting system has problems such as structure shaking,loose lamp head and even falling off with the increase of service time.Functionally,lighting requirements can only be fulfilled through continuous manual adjustment of helicopter driver driving experience and aircraft flight attitude.Therefore,it is urgent to optimize the structure of the landing lighting system to solve the shortcomings of the existing structure.At the same time,by optimizing and increasing the stabilization function of adaptive stabilization adjustment,the illumination performance can be improved by reducing the operation of helicopter driver.Taking this as the starting point,this paper optimizes the existing land system structure to solve the above problems.Specific research contents are as follows:First,the defects of the existing land lighting system are analyzed.There are two main problems:（1）the bolt fastening of the lamp head and rotating component and the structure of the double-dome wire roof reinforcement will cause the lamp head to loose and fall off due to the vibration generated by the helicopter flying;（2）the rubber block which eliminates the transmission clearance will aging and failing with the sunlight and rain.In order to meet the requirements of new functions,the pan-tilt structure is introduced to solve the problem of looseness caused by space limitation at the lamp head connection,and the adaptive stabilization adjustment function of the landing lighting system is realized with servo motor.Rubber block is replaced by mechanical rear limit device,which avoids aging due to harsh environment.Drive design and overall structure design are completed according to the optimization scheme,and three-dimensional model drawing is completed by CATIA software.Secondly,in order to solve the problem of insufficient torque of selected servo motor under strong wind load,a NGW type reducer is designed.The rigid virtual prototype of the designed reducer and the rigid-flexible coupling virtual prototype are established by using ADAMS software,and the difference between the speed of each gear stage simulated by the two virtual prototypes and the theoretical calculation data is compared.The results show that the average error of rigid virtual prototype is 1.58%compared with theoretical value and that of rigid-flexible coupling virtual prototype is reduced to 0.42%compared with theoretical value.It can be seen that the simulation results of rigid-flexible coupling virtual prototype are not only practical,but also more accurate,which proves that the structure is feasible.Then,the static analysis of the designed pan-tilt structure is carried out by ANSYS Workbench software.The maximum stress of the structure is 106.46 MPa,which is much less than the yield strength of material LY12.The maximum strain displacement of the structure is 0.0028mm,which is within the 10^-3 magnitude required by the design.Structural strength and rigidity of pan-tilt are relatively high,and structural quality can be appropriately reduced by parametric optimization.The parametric optimization design is carried out by ANSYS APDL module.After the iteration calculation of the algorithm,the structure mass is reduced by 60.13%,the maximum stress is increased to 107.84Mpa,which is only 1.30%higher than that of the original structure,and the maximum strain displacement is increased to 0.00443mm,still in the order of 10^-3.After optimization,the structure can still meet the design strength and stiffness requirements.Finally,the modal analysis of the designed NGW planetary reducer and the optimized pan-tilt structure is carried out by ANSYS Workbench software.By comparing the natural frequency with the main exciting vibration frequency of the helicopter,the NGW planetary reducer will not resonate and the pan-tilt structure may resonate in the high frequency range of random vibration.Resonance can be avoided by adding rubber dampers to the connection between the pan-tilt and the lighting components.Then carry out random vibration analysis and response spectrum analysis on key loaded components,and verify that the structure can meet the requirements of random vibration test after simulation.Through the above research,the paper carries on the simulation to the optimized design of the structure,and verifies the feasibility of the subsequent production of the structure.It provides theoretical basis and practical reference for the next real experiment.