Development Of A Multi-function Calibration System With Large Loads For Wind Tunnel Balances

The wind tunnel strain balance is a kind of experimental device which converts mechanical quantity into electric quantity,decomposes and measures the aerodynamic load acting on the aircraft model.Strain balances are the most important measurement device applied in the wind tunnel force/moment tests.Before a strain balance being mounted in a wind tunnel,it must be calibrated.The result of the calibration directly decides the performance of the balance.So the balance calibration machine and system become very important in all major aerodynamic research institutes.This thesis studies the general scheme of six-component automatic correction and loading calibration system in the body coordinates of the balance,based on the FL-9 Low-speed High-Reynolds number facility.Also the specific technical parameters are determined.The key issues for designing the calibration system are the automatic loading and the repositioning.The automatic system includes gemels with alterable ratios to enable different loading ranges and coordinate different components of the load applied.The repositioning system is the core of the calibration machine.This system utilizes self-compensating truss structures to reposition.The system innovatively adopts the symmetric loading to test and adjust the calibration machine,and acquires repositioning precision.This whole new designed calibration system is now put into application.It has calibrated multiple sting balances and external balances.These balances are applied in various wind tunnels,and the precision is high.The initial applications show that the system parameters meet the criteria of GJB eligibility criteria,and the lift,drag and pitching moment accuracy indexes can meet the criteria of GJB advanced level,so the system is reliable and precise.It is proved that the system scheme is feasible,economical and applicable.