| As the key basic experimental equipment,the hydraulic servo vibration is used to verify the control stability and structural reliability of the equipment in the real vibration environment required for use or transportation.It is widely used in the fields of seismic test of large-scale projects such as dams or high-rise buildings,road simulation test of automobiles or walking machinery,high frequency fatigue test of engineering materials and so on.Because of the complexity of the structure and the non-linearity of the hydraulic servo vibrator,especially due to the eccentric load,the output coupling of the freedoms channel of the system is serious,the frequency response is low and the robust stability is poor,which restricts the overall control performance of the vibrator.Therefore,this paper takes the 2-DOF servo vibrator as the research object,and studies its mode decoupling control under eccentric load.The work of this paper mainly focuses on the following four aspects:(1)The mechanical system,hydraulic drive system and data acquisition and servo control system of 2-DOF servo vibrator are designed.The key work is to use ABAQUS finite element software to analyze the natural frequencies of parts and whole parts of the vibrator to meet its natural frequencies requirements,and then design the hydraulic drive system and xPC Target data acquisition and servo control system based on Rapid Prototyping control technology.(2)The kinematics and dynamics model of the 2-DOF servo vibrator is established,and its dynamic and coupling characteristics are analyzed.Firstly,the position and attitude of the upper platform are described by using Euler angle,and the relationship between the freedom space and the joint space is studied.Secondly,Newton-Euler method and Lagrange method are used to establish the overall dynamic model of the parallel mechanism of the upper platform,hydraulic cylinder,eccentric load and vibrator.The dynamic model of hydraulic power components is established by mechanism modeling method and linearization method.Finally,the whole kinematics and dynamics model of electro-hydraulic drive vibrator system is established by using MATLAB/Simulink software,and the theoretical simulation is carried out.(3)The vibration differential equation of the vibrator is established by using the theory of vibration mechanics,and the coupling reasons of the freedom channels of the system are analyzed.The control structure of the virtual joint is constructed to transform the modal matrix into square matrix.The physical space of the strong coupling is mapped to the uncoupled modal space by the modal transformation.A three-state controller is built in the modal space to adjust the parameters so that the modal channels can be independently controlled and dynamically controlled.The performance consistency makes it satisfy the decoupling condition of DOF channel.(4)Through the experiments of step and sinusoidal response of single cylinder and system degree of freedom,the results show that the vibrator has good dynamic tracking performance.The mapping relationship between physical space and modal space,the independent control characteristics of each modal channel in modal space and the dynamic performance consistency experiments show that the modal decoupling control method combined with the three-state method is effective in decoupling the DOF channel of the 2-DOF servo vibrator system with eccentric load. |
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