Design And Simulation Of Vibration Isolation And Balance Device Based On 3-RPS Parallel Mechanism

In order to meet the needs of our military’s future rapid and mobile combat operations,it is necessary to improve the ability of troops to quickly assemble,deploy,and transfer personnel.However,the battlefield environment is complex and changeable,especially when driving in plateaus,hills and other areas.Due to the influence of various road conditions,passengers will be exposed to low-frequency vibrations transmitted from the floor of the compartment,which is likely to cause secondary injuries to the wounded.The initial method to reduce the vibration response is to reduce the tire pressure and adjust the suspension system parameters.The range of change is limited,which affects the performance of the vehicle,and the cost is relatively expensive and the calculation is complicated.Designing a vibration isolation and balanced seat that can effectively control vibration and instability caused by external excitation can ensure the overall driving performance of the car,reduce production costs and shorten the production cycle,so it has more application and development prospects.The semi-active control system only needs less energy to drive the system parameters such as stiffness or damping of the structure to change,thereby reducing the response of the device mechanism and adapting to changes in environmental excitation.It has the advantages of relatively simple structure,better robustness and stability.Among them,the magnetorheological damper has continuously adjustable damping,low power consumption and fast response speed.It is a semi-active intelligent vibration isolation device with excellent performance.The parallel mechanism is composed of upper and lower platforms and motion branch chains connecting the two platforms.It has compact structure,high motion accuracy,high rigidity,small motion redundancy error,and easy control.It can be used to design a balance device.This paper mainly considers the vertical direction excitation and the pitch and roll rotation excitation in the forward direction of the occupants when the vehicle is traveling.A magnetorheological damper is used as a vibration isolation device to isolate vibrations from vertical excitation.The 3-RPS parallel mechanism with less degrees of freedom is used as a balancing device to level the two rotational excitations of pitch and roll.Then the two devices are coupled in series to form a vibration isolation balance device to comprehensively control the excitation of the three degrees of freedom.As the basic structure of a vehicle-mounted stable seat,it can suppress and reduce the excitation of the human body,effectively reduce the damage to the human body caused by vibration and instability,and improve the comfort and safety.The main research contents and results are as follows:(1)Design the vibration isolation device based on the magnetorheological damper and construct the dynamic model.In order to obtain a good vibration isolation effect and obtain an accurate dynamic model of the magnetorheological damper,this paper proposes to combine the Bingham model and the Bouc-wen model to fit the output damping force of the damper in sections,based on the good yield characteristics of the Bingham model in the high-speed zone and the Bouc-wen model’s good hysteresis characteristics in the low-speed zone.The Bouc-wen model is used in the low-speed zone before yielding,and the Bingham model is used in the high-speed zone after yielding.Taking the yield rate as the node,the Bingham-Bouc Wen model was obtained by piecewise fitting,and used Matlab simulation to verify the fitting effect and smoothness of the new model.Then,constructed a single-degree-of-freedom vibration isolation system with magnetorheological damper.Simulation and analysis of the amplitude-frequency characteristic curve of the system under different currents and different amplitudes.Simulated the vibration isolation effect of the magnetorheological damper vibration isolation device.And use PID control strategy to optimize and set the control current to improve the vibration isolation effect.(2)In this paper,used the 3-RPS parallel mechanism as the balance device,and analyzed the dynamics analysis and the leveling method.Calculated and deduced the degree of freedom of the mechanism.Used analytical method to inversely solve the position of the device,and obtained the calculation formula based on the posture of the moving platform and the rotation angle of the rotating joint.Derive the Jacobian matrix of the mapping relationship between the input speed of the mechanism driving member and the output speed of the end moving platform according to the inverse solution equation.Based on this,analyzed the singularity of the device,and the dexterity of the device is analyzed by the condition number of the F-norm of the Jacobian matrix.Based on the classic center-point immobile leveling method,considering the structure and movement characteristics of the device itself,taking the high dexterity pose as the initial condition of the device,proposed an improved center-point immobile leveling method.And deduced the mathematical model of the device’s leveling.(3)Couple the vibration isolation device and the balance device in series to form a vibration isolation balance device,and analyze the overall vibration isolation and balance performance.Determined the installation method and key size parameters of the device,and determined the control mode of the device for the three excitations according to the characteristics of the device structure and input excitation.Coupled the dynamic model of the magnetorheological damper and the leveling model of the 3-RPS parallel mechanism as the overall control model of the device.Deduced the response of the system to the displacement,velocity and acceleration of the input excitation.Used Matlab software to simulate and verify the vibration isolation and balance performance of the device.Random vibrations with frequencies of 5Hz,10Hz,25Hz and amplitude within 5mm and band-limited white noise were used as vertical excitation Z.The sine function and the cosine function are used to simulate rotating excitationβandγto make them change in the range of±10°.The results show that the vertical displacement response of the device can be controlled within 2mm,the speed response is not greater than 9mm/s,the acceleration response is less than 450mm/s~2,and the acceleration response of low frequency vibration below 50Hz can be greatly reduced;the speed of the balance device support rod is 2.5mm/s,the acceleration changes within 1mm/s~2.To sum up,in order to effectively reduce the multi-dimensional vibration excitation of people when the vehicle is running,and improve the comfort,this paper designed a vibration isolation and balance device based on a magnetorheological damper and a 3-RPS parallel mechanism with a small degree of freedom to control the vertical excitation and the pitch and roll rotation excitation in the forward direction.Firstly,proposed a new dynamic model of magnetorheological damper,which has better fitting effect and smoothness.Secondly,carried out the kinematics analysis of the3-RPS parallel mechanism,obtained the inverse solution equation of its position,and analyzed the dexterity and singularity of the mechanism.Then,based on the typical leveling method,combined with the device’s own structure and movement characteristics,proposed an improved center-point immobilization leveling method.Finally,the dynamic model of the vibration isolation device is coupled with the leveling mathematical model of the balance device.Verifies the device’s good vibration isolation and balance capabilities by the Matlab simulation.The research results of this paper can provide a theoretical reference for the vibration isolation and balance control of personnel and precision instruments on different transportation platforms.