Capture Trajectory Test Six Degrees Of Freedom Mechanism Kinematics Dynamics Research

In order to avoid the collision of these external objects with the aircraft when launching or launching missiles,bombs,auxiliary fuel tanks,etc.,it is necessary to simulate the movement of the external objects from the aircraft after launch or release.Analog measurements require a six-degree-of-freedom mechanism placed in the wind tunnel.In this paper,a new six-degree-of-freedom mechanism is designed,and the kinematics,dynamics and trajectory planning of the organization are studied.1)In view of the fact that the previously designed wind tunnel capture six-degree-of-freedom mechanism can not meet the requirements of the current travel,this paper proposes a new type of serial-parallel hybrid six-degree-of-freedom mechanism;since all movements of the D-H method are related to the X-axis and the Z-axis,It is impossible to express the motion about the Y axis.In this paper,the basic coordinate transformation and D-H method are combined to establish the kinematics positive solution equation for the whole mechanism,and the finite element analysis of the mechanism under different attitude conditions is carried out.The Monte Carlo method is used to analyze its workspace and use SimMechanics.The simulation method is compared to verify the correctness of the motion model and the workspace.The results show that the X-direction and Y-direction stroke are increased by 4 times and the Z-direction stroke is increased by 4.8 times under the condition of structural strength and stiffness.2)The BP neural network method,numerical method and analytical method are used to explore the inverse kinematics of the mechanism.The results show that the BP neural network method has larger error than the numerical method and the analytical method,and the numerical method and the analytical method have high precision.The analytic method does not need to assign initial values and loop iterations,so the solution time is faster and is suitable for finding the inverse of the deterministic expression.The numerical method is more suitable for the case where the inverse expression cannot be used to determine the expression.For the problem that the initial value estimation is difficult when numerical method is solved,a new kinematic inverse solution numerical method equation initial value assignment method is proposed.The correctness of the method is proved by an example.3)In the multi-degree-of-freedom dynamics derivation process,the kinetic energy derivation process is extremely cumbersome because each mass point of the bar is analyzed and then summed and finally formed into a rigid body analysis.Imagine whether it is possible to simplify the calculation by simply reducing the rigid body directly to a particle.From the perspective of energy conservation,the formula for the equivalent rotation of a rigid body to a mass point is proposed,which is referred to as the equivalent particle model.Then the rigid body,particle and equivalent particle dynamics models are established respectively,and compared with the adams simulation analysis,the correctness of the equivalent particle model is established when the rigid body dynamics analysis of two degrees of freedom is established.At the same time,the dynamic model of the six-degree-of-freedom mechanism is applied by using the formula.The mathematical model is calculated by simulink and compared with the adams simulation results.It is verified that the method is effective in both cases with or without external load.It simplifies the tedious formula for deriving the kinetic energy of rigid bodies.This paper provides a new mathematical modeling method for multi-free mechanism dynamics analysis.4)The polynomial and 5th degree polynomial trajectory planning for the joint space displacement of the mechanism is carried out.By comparing the insufficiency points of the 3rd and 5th degree polynomials,the 535 polynomial trajectory planning method is comprehensively proposed.Compared with the cubic polynomial,it overcomes the acceleration curve.The mutation is discontinuous,which saves 0.003 seconds of run time compared to the fifth-order polynomial.At the same time reduce the maximum acceleration.In order to achieve a fast and stable organization of the organization to achieve a predetermined position to lay the theoretical foundation.