Chunsheng Song

Effect of stacking sequence on the torsional stiffness of the composite drive shaft

Torsional stiffness is an important parameter judging the performance of composite drive shaft. In this paper, a new mechanical analytical solution of torsional stiffness for the composite drive shaft with balance laminate is derived based on classical lamination theory and mechanical analysis. Finite element analysis (FEA) has been used to calculate the torsional stiffness of carbon fiber-reinforced plastic (CFRP) drive shaft. A torsion test platform has also been constructed to measure the torsional stiffness of CFRP drive shaft specimens. Results of the mechanical analytical solution, FEA, and experiments show that the composite tube with the location of ±45° layers near to the outer surface is larger than the ones with the location of ±45° layers near to the inner surface. The effect of stacking sequence on torsional stiffness is larger in the thick-walled than that in the thin-walled composite drive shaft. The mechanical analytical solution can complement classical lamination theory which cannot reflect the effect of stacking sequence in calculating the torsional stiffness.

Fuzzy Control of a Semi-active Multiple Degree-of-freedom Vibration Isolation System

Semi-active isolation systems fill the gap between passive and active systems, delivering the versatility and adaptability of fully active systems, by expending a small amount of energy to change system parameters such as stiffness and damping. Magnetic suspension vibration isolation provides an excellent active isolation technology, and has shown useful characteristics including noncontact isolation, fast response, high reliability and long lifespan. However, because it is highly nonlinear and time variant, the control of magnetic suspension vibration isolation is an area that still requires further exploration. This paper presents a fuzzy control algorithm for a semi-active multi-degree-of-freedom vibration system. The fuzzy control is based on the minimization of the weighted sum of squared output forces. The output force response of the fuzzy, PID control semi-active vibration isolation system and passive system under the same excitation are simulated. The simulation results show that the fuzzy control system has much better performance in vibration isolation. An experimental platform is developed to test the performance of the magnetic suspension vibration isolation system and the proposed fuzzy control algorithm. The experimental results are found to be in good agreement with simulation.

Fuzzy logic control based on genetic algorithm for a multi-source excitations floating raft active vibration isolation system

The floating raft active vibration isolation system itself is a complex system with high nonlinearity, strong coupling, and multi-source excitations, so it is difficult to build a mathematical model and control the system. As an intelligent control method, the fuzzy control algorithm can provide an intelligent path for the active control of the complex floating raft system. In this article, the system identification method is adopted to establish the discrete transfer function mathematical models for the floating raft active vibration isolation system. And then for the purpose of simulation and experimental study, the fuzzy controller is designed based on dual inputs of the acceleration and its variation and single output of control voltage. Since the control effect cannot be optimized due to the fact that the quantization factors and scale factors are usually gained by trial and error method and the control rules are designed by expert experience, the quantization, scale factors, and control rules are simultaneously optimized by adopting the genetic algorithm in which hybrid coding is conducted for both real numbers and integers. The simulation and experimental results show that the fuzzy controller based on genetic algorithm is superior to the conventional fuzzy controller on vibration suppression effect.

Research on Forces and Dynamics of Maglev Wind Turbine Generator

Maglev wind turbine generator (MWTG) technology has been widely studied due to its low loss, low maintenance cost, and high reliability. However, the dynamics of the magnetic bearing system differ fromthe those of the traditional mechanical bearing system. A horizontal axial MWTG supported with a permanent magnetic bearing is designed in this research and the radial forces and the natural frequencies of the rotor system are studied. The results show that the generatorhas a cyclical magnetic forceand an unreasonable bearing stiffness may mean that the rotor system needs to work in the resonance region; the bearing stiffness is the key factor to avoid this problem. This is the main rule of the bearing stiffness design in the MWTG, and this rule can also be used in other maglev permanent magnet motors.

Study on structural optimization design and cascade PID control of maglev actuator for active vibration isolation system

In view of the nonlinear output characteristics of actuators, and due to necessary large strokes for low-frequency vibration isolation platforms in microgravity environment, a method for structural optimization design and cascade PID control of maglev actuators was put forward based on the principle of Lorentz force. Furthermore, the method was utilized to design a magnetic circuit in accordance with the self-demagnetization effect and to multi-objectively optimize the structure parameters of a coil. A mathematical model was established of the remarkably nonlinear output force, due to the nonuniform magnetic fields to optimize its output force and current, so that the time-varying output requirements of controllers may be satisfied. System identification was performed to obtain the mathematical model of its control channel and design cascade PID controllers. This method was applied to lower the phase lag and equivalent time constant of a closed secondary circuit system so that not only the system stability and response rate may be improved, but also the growth of the gain of the controller may lead to growth of the damped natural frequency of the cascade control system; thus, the system settling time may fall and the system control quality may be improved. Simulation was also carried out to the cascade PID control corresponding to the mathematical model so that the cascade PID controller may have a relatively good control effect on disturbing acceleration signals. Experiments were carried out to cascade PID control of maglev actuators to further verify vibration control performances. Comparisons of the measured and simulated acceleration transmissibility data are basically consistent within the band 1–25 Hz. Measured and simulated results indicate that application of the cascade PID control method may attenuate the control object in the range −22.522 to −2.189 dB within the band 1–25 Hz and perform effective vibration control.

Semi-active Fuzzy Control for Vibration Isolation System with Magnetic Suspension Isolator

The magnetic suspension isolator is designed. The vibration isolation system supported by magnetic suspension and ordinary vibration isolators’ series structure and its equivalent model are established. Taking the system as research subject, the dynamic mathematic expression of the system is established. Equivalent stiffness and damping are obtained .Base on the expression, semi-active output feedback mode fuzzy controller is designed for the isolation system. Then, the appropriate current and optimal stiffness of magnetic suspension isolator could be obtained. Under complex-frequency exciting signal and shock exciting signal are simulated. The simulation results indicate that the isolation performance and shock resistance characteristic of magnetic suspension supporting isolation system with semi-active mode fuzzy control method are more effective in vibration isolation in comparison with the passive system.

Experimental study on sliding mode variable structure control of active vibration isolation system of floating raft under multiple excitations

The frequency components of vibration signal in vibration isolation system under multiple excitations are quite complex.Self-adaptive feedforward control method based on Least Mean Square algorithm has strict requirements for reference signal, which results in a certain restriction on its practical application. Sliding mode variable structure control method needs neither complicated reference signal nor accurate mathematical model. It has the strong robustness for external disturbance and system parameter perturbation, and the physical implementation is simple. To this end, application of sliding mode variable structure control method is studied. First, mathematical model of the control channel through system is established for identification. Second, the discrete sliding mode variable structure controller based on state-space model is designed to carry out simulation and experiment. The experimental result indicates that root mean square value of vibration signal after control is decreased by 57.90%, of which the amplitudes of two main frequency components 17 and 25 Hz reduce by 42.66 and 72.71%, respectively. This shows that sliding mode variable structure control is an effective control method for active vibration isolation of floating raft under multiple excitations.

Analytical model for flexural damping responses of CFRP cantilever beams in the low-frequency vibration

In this paper, an analytical model for the flexural vibration damping of Carbon Fiber Reinforced Plastics (CFRP) cantilever beams was proposed, which is based on the Lamination Theory and Euler–Bernoulli Beam Theory. By using a finite element analysis and an analytical model, four sets of specific damping capacity with different pavement schemes were predicted, and flexural vibration test and damping analysis were carried out. Comparing the analytical model, finite element analysis, and test results, it could be found that the analytical model had relatively good accuracy in predicting the first-order natural frequency and specific damping capacity of the bending vibration of CFRP beams. The maximum error of the first-order natural frequency between the analysis result and the experimental result was 7.05%; the maximum specific damping capacity error was only 5.65%. Comparing the finite element analysis method and the experiment results, the maximum error of the first-order natural frequency was 7.8%, the error of the specific damping capacity was bigger, and the [±30°]5S specimen was as high as 18.7%. However, there was a significant error when the analytical model was used to predict the second-order natural frequency and the specific damping capacity of CFRP beam’s flexural vibration.

The Bending Responses of Sandwich Panels with Aluminium Honeycomb Core and CFRP Skins Used in Electric Vehicle Body

The aim of this paper was to investigate bending responses of sandwich panels with aluminium honeycomb core and carbon fibre-reinforced plastic (CFRP) skins used in electric vehicle body subjected to quasistatic bending. The typical load-displacement curves, failure modes, and energy absorption are studied. The effects of fibre direction, stacking sequence, layer thickness, and loading velocity on the crashworthiness characteristics are discussed. The finite element analysis (FEA) results are compared with experimental measurements. It is observed that there are good agreements between the FEA and experimental results. Numerical simulations and experiment predict that the honeycomb sandwich panels with ±30° and ±45° fibre direction, asymmetrical stacking sequence (45°/−45°/45°/−45°), thicker panels (0.2 mm∼0.4 mm), and smaller loading velocity (5 mm/min∼30 mm/min) have better crashworthiness performance. The FEA prediction is also helpful in understanding the initiation and propagation of cracks within the honeycomb sandwich panels.

Study on Forced Torsional Vibration of CFRP Drive-Line System with Internal Damping

The use of CFRP transmission shaft has positive effect on the weight and flexural vibration reduction of drive-line system. However, the application of CFRP transmission shaft will greatly reduce the torsional stiffness of the drive-line, and may cause strong transient torsional vibration. Which will seriously affect the performance of CFRP drive-line. In this study, the forced torsional vibration of the CFRP drive-line system is carried out using the lumped parameter model. In addition, the effect of rotary inertia, internal damping, coupling due to the composite laminate, and excitation torque are incorporated in the modified transfer matrix model (TMM). Then, the modified TMM is used to predict the torsional frequency and forced torsional vibration of a CFRP drive-line with three-segment drive shafts. The results of modified TMM shown that the rotational speed difference of the CFRP transmission shaft segment is much larger than metal transmission shaft segment under excitation torque. And compared the results from finite element simulation, modified TMM and torsional vibration experiment respectively, and it has shown that the modified TMM can accurately predict forced torsional vibration behaviors of the CFRP drive-line system.