Study On The Measuring Technique Of Thrust Line Of Solid Rocket Motor With Laser Tracker

Solid rocket motors are widely applied in medium-long range missiles for the benefits such as simple structure, high density of propellant, high acceleration and easy storage. The thrust line of solid rocket motor will depart from the designed value because of various errors in the process of production and assembly. The offset and deflexion of the thrust line will make the missiles depart from the prearranged path for the deflection moment in the working process. Therefore, it's important to measure the thrust line of solid rocket motor after its assembly.In this thesis, the domestic and foreign present status of measuring the thrust line of the solid rocket motor are investigated thoroughly, typical static and dynamic measurements are dissertated, also the limitation of the recent measuring techniques is discussed. Based on the analysis of present status of large scale coordinate measurement, this paper proposes a new scheme which uses Laser Tracker to measure the thrust line since Laser Tracker has predominance on measuring precision, range and efficiency.This thesis takes solid rocket motors used in one model of missiles as a measuring object, and studies the measuring techniques of base axis, circular zero line and the thrust line of a solid rocket motor. The solid rocket motor nozzle has a combined rotation structure, aiming at this feature, the measuring techniques of complex rotatory surface is studied. According to the measuring equation of the thrust line, the computation model of the offset, deflexion and azimuth of deflection is deduced. What's more, in terms of the measuring and handling process of the thrust line, several key techniques are summed up which includes optimal fitting algorithm for the thrust line of solid rocket motor, solving algorithm of coordinate conversion parameters for moving station measurement and the uncertainty evaluation for the thrust line measurement of Laser Tracker.The thesis takes nozzle combined with arc concave and paraboloid as the investigated subject. In allusion to the complexity of traditional non-linear least squares solution and the randomicity of the solid rocket motor nozzle's location, an optimal fitting algorithm of the symmetry axis of complex rotary surface is put forward, which is based on coordinates conversion and optimal Hooke-Jeeves pattern search method. Moreover, further research is taken on the initial value estimate of this algorithm to improve the efficiency of an optimal fitting algorithm.The working principle of moving station measurement of Laser Tracker and the solution algorithm for coordinate conversion parameters were analyzed in this paper. On the basis of that, the solution model based on spherical coordinate residuals of coordinate conversion parameters for moving station measurement was established according to Laser Tracker's spherical coordinate measuring principle. The algorithm of initial value estimate for optimal coordinate conversion parameters was confirmed after studying Laser Tracker's application characteristics. On the foundation of the distributed rule of Laser Tracker's uncertainty, different weight coefficients were given to the angle residuals and the distance residual, the optimal solving model of weighted spherical residuals coordinate conversion parameters was established and simulated, which proved that this algorithm provided higher resolving precision.The transportation model of the uncertainty in moving station measurement was studied on the basis of the analysis of uncertainty source in Laser Tracker's measuring process. A simulation was also taken to measure the thrust line of a solid rocket motor based on Monte-Carlo method. It was proved that the thrust line measurement scheme of the solid rocket motor based on Laser Tracker could satisfy the designed uncertainty requirement by the simulation results.At last, experiments for one standard gauge and one solid rocket motor were taken, and these experiments proved that the algorithm proposed in this paper was correct. In addition, the thrust line measurement scheme of the solid rocket motor provided higher measuring precision and better repeatability.