| Because of the particularity of the working environment of the ship,the ship is an elastic body with full degree of freedom floating on the surface of the water.The ship will generate random motions such as roll,pitch,yaw,heave and sway at sea.The various equipments loaded on the ship will be affected by different external interference forces at sea.These interference forces will cause the overall or local vibration of the shipborne equipments,if the shipborne equipments are over-loaded.Degree vibration can make shipborne equipment work out of order and damage,resulting in shorter service life;Vibration can cause deformation of elastic components in Shipborne equipment,resulting in poor contact or open circuit of these components with contacts(potentiometers,band switches,etc.).When the natural frequency of components in shipborne equipment is the same as the excitation frequency,resonance phenomenon will occur,endangering the positivity of components.Frequent operation will affect the normal operation of the whole shipboard equipment.In order to ensure the reliability of Shipborne equipment,it is necessary to design an active vibration isolation mechanism to isolate the vibration of shipborne equipment and ensure the normal operation and stability of equipment.In this paper,a parallel reconfigurable vibration isolation and stabilization platform is innovatively designed according to the motion characteristics of ships.The parallel reconfigurable vibration isolation and stabilization platform mechanism designed in this paper is 4-CRS(CPS)/RPS structure.The mechanism can realize 3 rotations,2 translations and 5 degrees of freedom.The mechanism can respond to the position and attitude information of ship feedback in real time and realize active vibration isolation.Its working characteristics are very strong.Environmental adaptability and sensitivity,the main contents of this paper are as follows:1)Screw theory is used to analyze the degree of freedom of the mechanism,and the positional inverse solution,velocity and acceleration analysis of the parallel reconfigurable platform are carried out,and the velocity Jacobian matrix is established and calculated.Finally,the correctness of the inverse position and positive solution of the position is verified by MATLAB.2)The singularity analysis of parallel reconfigurable vibration isolation and stabilization platform structure is carried out.When the structure is singular at the same time,there exists compound singularity.In order to avoid the occurrence of singularity,this paper optimizes the drive,and avoids the occurrence of compound singularity by means of three moving and two cylindrical pairs.Secondly,the workspace of the parallel reconfigurable vibration isolation and stabilization platform is analyzed,and the MATLAB search method is used to solve the workspace.Finally,the factors causing theposition and attitude accuracy of the parallel reconfigurable vibration isolation and stabilization platform and the evaluation index of vibration isolation are analyzed.3)The dynamic equation of rigid body is deduced by Lagrange method,and the correctness of the dynamic equation of parallel reconfigurable vibration isolation and stabilization platform is verified by the joint simulation of MATLAB and ADAMS.4)The elastodynamic equation of the element is derived by finite element method.According to the two constraints of parallel reconfigurable vibration isolation and stabilization platform: kinematics constraints and dynamics constraints,the kinematics constraints equation and dynamics constraints equation are deduced through two constraints,and the elastodynamics equation of the branched chain is assembled into the elastodynamics equation of the parallel reconfigurable vibration isolation and stabilization platform system to complete the parallel reconfigurable vibration isolation and stabilization level.Elastodynamic modeling of the platform.The elastodynamic equation of the parallel reconfigurable vibration isolation and stabilization platform is solved by Newmark method.The curves of displacement error,velocity error and acceleration error of the output of the parallel mechanism in X and Z directions with time are obtained.5)The stiffness and damping of parallel mechanism are modeled,then the vibration response of parallel mechanism is analyzed,and the response ofparallel mechanism under harmonic excitation and arbitrary excitation is analyzed.Finally,on the basis of wave theory,the real-time ship position and attitude signal is established when the ship moves at sea.The PID control strategy is adopted,the branch closed-loop PID control method is adopted,and the parallel reconfigurable mechanism is used.As an input and output system,the branching chains of the vibration isolation and stabilization platform cooperate with each other to achieve the desired posture.Finally,through the joint simulation of Adams and Simulink,the effect of controlling parallel reconfigurable vibration isolation and stabilization platform is verified. |
