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Improving pitch and yaw motion control of twin rotor MIMO system
Get PDFIn this paper, a fuzzy logic controller approach is presented for twin rotor multi-input-multi-output (MIMO) system in order to improve the control of pitch and yaw motions under hovering conditions. Twin rotor MIMO system resembles a helicopter model in some common aspects like cross coupling of pitch and yaw motions. The proposed approach is compared with another control strategy by simulations for a nonlinear two degrees of freedom twin rotor model. Set point reaching and trajectory tracking behaviours of the TRMS are analysed by time and step response characteristics. Results of time and step responses indicate that fuzzy logic controller improves set point reaching and trajectory tracking performance of the closed loop system
A delay analysis of mass volume train security detection network
Get PDFMass volume train security detection network is a real-time and reliable onboard data communication network based on the train level and vehicle level Ethernet network, which will transmit and send mass volume train status and fault diagnosis information, the event log data, rich audio and video data. The network structure and topology is presented, which include all devices which can attach to the network. Then, a delay model of different network topology is put forward, which indicates that the onboard ring network is superior to the linear network topology. Finally, the analysis is confirmed by simulation results. The results indicated that onboard ring topology network will improve control and network function of train, enhance trains’ service and maintenance efficiency
Theoretical study on self-synchronization of two homodromy rotors coupled with a pendulum rod in a far-resonant vibrating system
Get PDFThe objective of this paper is to investigate the self-synchronization of two homodromy rotors coupled with a pendulum rod in a far-resonant vibrating system. Using the average method and revisionary small parameters, we derive the dimensionless equation of the self-synchronization criterion and synchronous stability of the vibrating system. Meanwhile, to prove the correctness of the theoretical analysis, the diversity feature of the vibrating system is simulated numerically. Both results of theoretical analysis and numerical simulation show that increasing the length of the pendulum rod or decreasing the mass of the rotor connected with pendulum rod can ensure the self-synchronization and synchronous stability of two homodromy rotors in the vibrating system
Optimization design of muffler based on acoustic transfer matrix and genetic algorithm
Get PDFSo as to improve the noise reduction performance and the optimization efficiency of the muffler, an optimization design method based on acoustic transfer matrix and genetic algorithm was proposed in this paper, wherein the transmission loss at certain frequency was treated as the optimization objective, and each structural dimension of the muffler as the design variable, the structural optimization design was conducted through genetic algorithm, thus the optimal solutions were eventually obtained; Moreover, single objective optimization and multiple objective optimization were successively performed, with the results compared with each other, through which it could be demonstrated that the result of the latter was superior to that of the former, concretely, the noise was reduced by 21.32 dB
Experiment and simulation studies on sound insulation performance of the wooden component
Get PDFWooden component has been used extensively in industries and the sound insulation performance of these components will directly be associated with the noise problem. We used sound pressure method and sound intensity method separately to measure the transmission loss of wood component, their results were in good agreement through the entire frequency band and the differences between them are in reasonable engineering error range. Test failures have been avoided by this as well as providing some protection for the subsequent simulation validation. After that, the damping loss factor of wood component has been measured by pulse attenuation method and imported into AML model to calculate the transmission loss, compared to experiment results, they were in good agreement, which indicates this kind of simulation method is available in the prediction of the acoustic performance for wooden component. Various technique means have been used to optimize the sound insulation performance, such as changing the density, elastic modulus, thickness of wooden component and surface treatment and sound package, and the results show that all the optimization programs can be effective in the improvement of sound insulation performance. At last, all the optimization data was arranged and compiled into a database, through the operation of the database interface, it is easy to select any group of data to draw graphics. This database provides an effective way to develop the optimal program of wooden component which has the best sound insulation performance
Aerodynamic simulation of wind turbine blade airfoil with different turbulence models
Get PDFThe different turbulence models have significant impacts on the aerodynamic performance of wind turbine blade airfoil. A kind of wind turbine blade airfoil was applied as the research object, in order to analyze the impacts of three different turbulence models which are S-A, k-εRNG, k-ωSST on the aerodynamic performance of wind turbine airfoil under different attack angles. By comparing the aerodynamic simulation results with the theoretical values of the lift coefficients, drag coefficients and the ratio of lift coefficient to drag coefficient for the forecast of best angle of attack, the effects of these three turbulence models on the blade airfoil aerodynamic performance were estimated in detail. The simulation of lift coefficient of wind turbine blade airfoil was verified with the flow field simulation of blade airfoil. A combined turbulence model, using different turbulence model for different angle of attack, was put forward. The simulation results demonstrate that, for the selected blade airfoil, using S-A turbulence model before the best attack angle and k-εRNG turbulence model after the best attack angle respectively, can make the simulation of blade airfoil aerodynamic performance much more accurate than the aerodynamic performance simulation using one single turbulence model, with the acceptable iterative time and the acceptable ratio of lift coefficient to drag coefficient. Therefore, the combined turbulence model can overcome the shortcomings when using only a traditional single turbulence model to simulate the aerodynamic performance of wind turbine blade airfoil, which will have a development and application value in the future
Using Taguchi’s method to minimize cogging force of a PM transverse flux linear motor
Get PDFCogging force accounts for important downsides in several aspects, namely causing the speed ripples, inducing vibrations and noises, and increasing the difficulty of position control. All of these negative affects will become more obvious, particularly under light loads and low speeds. So if the cogging force can be kept as minimal as possible, or even completely disappeared, the operational performance of motors will be improved significantly. As our preliminary study indicates, the magnitude of cogging force is influenced by construction of motors, which govern a number of motor parameters. In this paper, the cogging force of a novel type of permanent magnet excited transverse flux linear synchronous motor will be minimized in two steps. First, theoretical analysis will be employed to obtain the most influential parameter on cogging force. Second, Taguchi’s method including 2D finite element analysis is applied to minimize the cogging force. Analytical and simulation results indicate the usefulness of our approach in practice
Piezoelectric actuator for micro robot used in nanosatellite
Get PDFThe nanosatellites of the CubeSat standard (10×10×10 cm and with mass 1-10 kg) was designed to reduce cost and development time and to maximize science return. However, the small size of the spacecraft imposes substantial mass, volume, and power constraints. The challenge remains to be the miniaturization of the various robots for the manipulation of functional objects, such as cameras, laser sources, mirrors and other used in nanosatellites. Therefore in particular, precision positioning of the manipulated object is important task for robots used in nanosatellites as well. In this paper authors present the design of robot driven by the piezoelectric actuators. Investigations of the robot are presented and they prove ability to improve the accuracy of the movement for the robot arm using two bending bimorph type piezoelectric actuators and 3DOF rotary piezoelectric motor
The multivariable finite elements based on B-spline wavelet on the interval for 1D structural mechanics
Get PDFWavelet finite elements with two kinds of variables for 1D structural mechanics are constructed based on B-spline wavelet on the interval (BSWI) and the generalized variational principle. In contrast to the traditional method, the BSWI element with two kinds of variables (TBSWI) can improve the solution accuracy of the generalized stress apparently, because generalized displacement and stress are interpolated separately. Another superiority of the elements constructed is the interpolating function BSWI, which has very good approximation property, further guarantees solution accuracy. Euler beam, Timoshenko beam and Elastic foundation beam are studied providing several numerical examples to verify the efficiency
Study of wave barriers design for the mitigation of railway ground vibrations
Get PDFNowadays, the consolidation of the rail in highly populated areas has become a reality. Foundations, buildings, high accuracy devices and people are susceptible to suffer from vibrations induced by passing trains. Therefore, models for predicting ground vibrations are required in order to determine new mitigation measures. Rectangular open or in-filled trenches are a suitable solution to be used near constructed railway lines. Their installation is fast, easy and economic since no intrusion in the track is needed. In this work, the influence of the trench design on its effectiveness is analyzed considering a train moving with subsonic speed. A finite element model of the track has been developed and validated with real data registered along the tram network in Alicante (Spain). The analysis is carried out in the time domain considering the quasi-static movement of the vehicles. The results demonstrate that, in ascending order, the most relevant parameters in a trench are its width, depth and in-filled material or trench typology. However, it is also concluded that other conditions such as the stratification of soil are essential in order to determine an optimal design of a wave barrier