Papers by Author: Zhao Bo Chen

Abstract: Within this work, a six-axis parallel vibration isolation platform with semi-active control ability is investigated. Traditional magnetorheological (MR) dampers could supply large output force and long stroke, but it also comes with a large self-weight. This problem is more serious when several MR dampers are needed in a parallel platform. Firstly, a double-piston MR damper have been developed, which will brings a small self-weight feature to the damper. Hyperbolic tangent model have been used to describe damper's nonlinear hysteresis. Using six of this double-piston MR damper, a parallel vibration isolation platform based on a cubic Stewart platform mechanism has been designed. Dynamical model of this platform has been built and simulated. Numerical simulation results in frequency domain indicate that the parallel semi-active vibration isolation platform has desirable vibration isolation properties in all six axes.

Abstract: In order to develop a compact and lightweight controllable damper for space truss structures vibration suppression, a novel double-piston magnetorheological (MR) damper is proposed. Working principle of this damper has been analyzed. One prototype damper have been designed and fabricated according to the analysis results. A series of experiments have been performed to get this prototype damper's dynamical properties. Hyperbolic tangent model have been used to describe damper's nonlinear hysteresis. After model optimization using the nonlinear least squares method, the relationship between damper force and drive currents have been acquired under different excitation conditions. Comparison between the reconstructed results and testing data indicates that the optimized model shows enough accuracy to not only present the experimental data, but also forecast the hysteretic properties of this damper.

Abstract: A novel intelligent driver based on digital signal controller (DSC) has been put forward for magneto-rheological (MR) damper. The working principles of MR damper were described, as well as the hardware circuit scheme of signal condition and MR damper driver etc. on account of TMS320F28335 DSC. A hierarchical control algorithm was designed and the studies for the performance of the driver were conducted. The results suggest that the driver could provide accurate drive current for MR damper, and meanwhile the respond time is less than 2ms, which can meet the drive requirements of MR damper.

Abstract: Shape memory alloy (SMA) is a type of smart material with huge driving force, and large driven displacement. Using SMA as the structure driver may force a bi-directional deformation structure that can achieve high efficiency and compact driving structure. SMA, together with elastic component, forms the two-way driving structure; however the two, if respectively serving as the driver, can enable the occurrence of the simplest bi-directional drivable structure. The offset structure constituted by SMA, not only can achieve two-way drive, and does not require continuous input of energy during the shape-stabilizing period. This paper studies the design methods of these two structures, gives the typical formulas, which makes possible efficient and compact bi-directional drivable structures.

Abstract: Current coach mainly use the passive rubber mount system to isolate vibration, it’s hard to meet the engine broadband range isolation requirements. In order to reduce the coach engine vibration’s influence on the ride comfort and operational stability, it’s proposed that a magnetorheological fluid powertrain mount system. Set up the six degrees of freedom dynamic model and 1/4 engine single freedom vibration model. Design a fuzzy controller, which the input is dynamic exciting force and second order main frequency, the output is control current. Simulate the three types systems with the help of software of MATLAB/SIMULINK and Fuzzy control toolbox. The result shows that when fuzzy controller works, adjustable damping effect is obvious, it can attenuate vibration in large degree. The magnetorheological hydraulic mount with the fuzzy control ,compared with rubber mount and traditional hydraulic mount, has better isolation effect. Its damp can be controlled real-time, and it can be effective in isolation within the broadband.

Abstract: To efficiently reduce vibration and noise of a plate, an optimization of passive constrained layer damping (CLD) is presented. The dynamic equation of a sandwich plate with CLD treatment is derived using Lagrange’s method. The assumed modes method is employed to solve the equation and obtain the vibrational energy and sound power, which are used as the objective of optimal design. A genetic algorithm of big mutation is employed to search for the optimum of the location of CLD treatment, the thicknesses of both the constraining layer and the viscoelastic layer and the shear modulus of the viscoelastic material with the restriction of added mass of the total CLD treatment. Numerical results show that for a simply-supported plate with a transverse force (1Hz~200Hz) applied at (0.8L_a, 0.8L_b), the optimized CLD significantly reduce the vibrational energy and sound power.

Abstract: with the development of finite element technology, finite element model is becoming to the main analysis tool. However, because some theoretic assumptions, unsuitable constraint and uncertain material property are applied, the simulation result of finite element model isn’t different from the testing data. In order to improve the design quality and safety of spacecraft, this paper deduced the formula of spacecraft finite element updating, developed the spacecraft finite element model updating system, the software mainly of five parts: the frequency response function calculation, the loading inverse solution, the finite element model updating, the data display, virtual experimentation. Software can complete exciting force inverse, parameter sensitivity analysis, parameters screening and finite element model updating. The calculation result of updated finite element model is in accordance with testing curve shape on the main vibration direction, first-order frequency error is ±5%, response error is ±10%. Software meet the need of finite element model updating, it provide a software base for spacecraft design.

Abstract: In this paper, an optimization study of partially covered beam with a constrained viscoelastic layer is presented. An energy approach and Lagrange’s method are used to establish the governing equation of motion of a CLD covered beam, and the assumed modes method is employed in solving the equation to obtain the modal loss factors which are used as the objective of optimal layout. A genetic algorithm of big mutation is employed to search for the optimum of the patch’s location, the thicknesses of both the constraining layer (CL) and the viscoelastic layer (VL) and the shear modulus of the viscoelastic material with the restriction of added volume of the total CLD treatment. Numerical results show that the optima of the design variables are highly relevant to each other. The thinner constraining layer requires a softer viscoelastic material for an optimal damping treatment. The variation of the CL thickness decreases slowly and that of the VL thickness increases with the increase of the thickness of the CLD treatment. One end of optimal damping treatment locates closely one end of base beam.

Abstract: Acording to the fact that the finite element model of electromagnetic vibration shaker for virtual experiment is not accurate enough to complete accurately spacecraft test, made a correlation analysis of the finite element output frequency response function and the measured frequency response function by their correlation coefficients. Analyzed the sensitivity of the materials for FRF and screened the parameters to update, made the correlation coefficient error of electromagnetic vibration shaker finite element model frequency response function and the measured as the optimization objective, the optimization and modification of shaker finite element model parameters were completed by iteration method. The frequency response function of the modified finite element model approximately agreed with the experimental frequency response function. It met the virtual experiments of electromagnetic vibration shaker.