| While the vessel is navigating the sea,it tends to sway largely under the influence of weaves.Thus,it would be very difficult for helicopters to land on the quarterdecks.In order to provide a stable guiding beam which can lead pilots to land helicopters safely,a stabilized platform of three degrees of freedom is designed.This stabilized platform is composed of a 2-DOF parallel mechanism which has passive link and helps to eliminate the rolling and pitching motion,and an azimuth mechanism whose angles can be adjusted according to the direction that the helicopters come from.Firstly,according to the overseas and domestic research status on stable platform,the function and design requirements of parallel platform,and the construction type,drive mode and working principle of existing parallel stabilized platform,an overall mechanism scheme is put forward,which is made up of a 2-DOF parallel mechanism that has passive link and can roll around two orthogonal axes,and an azimuth mechanism that consists of a pair of gears.The scheme is featured with compact structure,big conversion ratio,low effect of load inertia towards motor characteristics,and high driving accuracy.So as to unify driving mechanism and improve the overall level of integration,a modular linear actuator is designed.Besides,an overall control program is designed,based on mechanism features and function.Secondly,With the analysis of kinematics of the two degrees of freedom parallel mechanism by using coordinate transformation method finished,the kinematics inverse solution and positive solution model is established.Velocity Jacobin matrix is obtained through the derivation of the equation of motion constraints.Kinematics simulation model and three-dimensional is established by using the MATLAB/Simulink tool and UG software simulation model respectively.The same result is concluded at the same time after the kinematics simulation analysis.And the accuracy of the structure parameter design is verified.Lagrange method is adopted to establish the dynamics equation of two degrees of freedom parallel mechanism,and the dynamics simulation was carried out on the parallel mechanism through the MATLAB/SimMechanics tool.To verify the effectiveness of the motor driver's ability,and to analyze the working space of the two degree of freedom parallel mechanism,the result of meets the design requirements.Finite element analysis was carried out on the key parts with the aid of UG senior simulation function.And the validity of the size parameters of the parts design is verified.Then,the factors that influence the attitude angles' error of the moving platform is analyzed by combing combining with the characteristics of mechanism and the principle of work.Through the method that the key variables of the kinematic constraint equations is differentiated on both sides at the same time,the error model of two degrees of freedom parallel mechanism is established.Through the simulation analysis of error model,it has been made clear about the extent of the impact of the various error sources impact on the posture error of moving platform,and the error distribution is completed.The influencing factors of the error of bar length which are the error of gear and screw driving has been Analyzed.Finally,the experimental prototype of 3-DOF stabilized platform has been developed according to the designed parameters,and the experimental platform is set up which is based on the dSPACE semi physical simulation system,the precision of electric draw stem test and stabilized platform open loop test and closed loop test are completed.The error curve of the experiment is the same as forecasted,which turns out that the scheme and the rationality of the design of structural parameters are correct. |
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