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The net power control of hydraulic-electricity energy regenerative suspension
Get PDFFor achieving the control of hydraulic-electricity energy regenerative suspension (HERS), a novel control algorithm, net power control (NPC), is applied in this study. A HERS unit as a new energy reclaiming suspension device is equipped with an energy-harvesting hydraulic-electricity shock absorber (HESA). The composition and classification of HESA damping force were analyzed based on the basic working principle of HESA. Thus, the mathematical model of HESA damping force is deduced as a function of suspension dynamic speed and load current. A series of experiments were made to verify the reliability of the model. Based on the energy flow analysis of the suspension system, the net power flowing into the suspension is calculated. In order to minimize the vibration acceleration of the vehicle body, a novel net power control is proposed. The comparison result indicates the control effect of NPC is more significant than skyhook control, especially in the high excitation frequency. Also, the HERS bench test was carried out to verify the feasibility of NPC. The related results show that the maximum acceleration of the vibration is improved by 34.23 % with NPC on bump pavement excitation. And on B-class random road, the root mean square (RMS) value of the sprung mass vibration acceleration is reduced by 65 %. Furthermore, the influence of suspension dynamic velocity and deflection on the optimal control load current is obtained
Effects of misalignment on the nonlinear dynamics of a two-shaft rotor-bearing-gear coupling system with rub-impact fault
Get PDFIn rotor-bearing system, the misalignment can lead to secondary faults, such as the rub-impact fault. How the development of misalignment could affect the rub-impact force and other dynamic responses is important for the vibration control and fault diagnosis of rotor system. In this paper, a mathematical model of a two-shaft rotor-bearing- gear coupling system is established. The model is validated through the misaligned force of gear coupling, the supporting force of the lubricated ball bearing and the whole rotor response. To overcome the limit of traditional approaches and further dig out fault characteristics, the time-frequency method is introduced to analyze the dynamic response from both the time and frequency domains points of view. It is found the misalignment effect on rotor dynamic responses is mainly focused in high rotating speed range. The development of misalignment has an obvious adverse effect on the rotor stability. Some intermittent components in low frequency range due to the occurrence and development of misalignment can be found affecting the rotor stability at low speed range, and the high frequency rub-impact components can be found responsible for the unstable state of rotor
Feature extraction method based on VMD and MFDFA for fault diagnosis of reciprocating compressor valve
Get PDFAiming at the nonlinearity, nonstationarity and multi-component coupling characteristics of reciprocating compressor vibration signals, an integrated feature extraction method based on the variational mode decomposition (VMD) and multi-fractal detrended fluctuation analysis (MFDFA) is proposed for a fault diagnosis for a reciprocating compressor valve. Firstly, to eliminate the noise interference, a novel VMD method with superior anti-interference performance was utilized to obtain several components of the quasi-orthogonal band-limited intrinsic mode function (BLIMF) from a strong non-stationarity vibration signal, and a consistent number K of BLIMFs was selected based on a novel criterion for all fault states. Secondly, the MFDFA method, which can describe the multi-fractal structure feature of non-stationary time series, was applied to analyze each BLIMF component, and the parameters of MFDFA were employed as the eigenvectors to reflect the structure characteristics and local scale behavior of the vibration signal. Then, the principal component analysis (PCA) was introduced to refine the eigenvectors for a higher recognition efficiency and accuracy. Finally, the vibration signals of four types of reciprocating compressor valve faults were analyzed by this method, and the faults were identified correctly by pattern classifiers of BTSVM and CNN. Further results comparison with other feature extraction methods verifies the superiority of the proposed method
The fuzzy model of the emergency level assessment at sea
Get PDFThis paper presents the model based on a fuzzy set theory, designed to assess the level of emergency situations at sea. The model consists of three linguistic input variables and one single output. To determine the emergency level at sea, the following was taken into account: information about the dangers to human health and life (group of persons), the extent of damage to the ship and the level of environmental pollution. The paper presents the fuzzy sets corresponding to the term of these linguistic variables and their analytical and graphical representation. The fuzzy product base of fuzzy model contains 80 rules
Dynamics of tripod drive with elastic self-sustaining transmission
Get PDFThe article describes a mathematical model of dynamics of electromechanical drive with elastic transmission gear. A motor is connected to the tripod actuating links by self-sustaining transmission. The analytical conditions of drive dynamic seizure absence have been obtained
About formation of the stable modes of the movement of multilink mechanical systems
Get PDFThe problem of synthesis of the controlled movement of the stepping robot, the movers of that move on trajectories with the sites, which are close to rectilinear, is considered. Stabilization of movement of points on the movers of stepping robot on a rectilinear trajectory will allow synthesizing algorithm of stepping without jumps of the accelerations in points of change of phases of a support of movers. In this case, under the control object, the point of mover is understood, and the controlled coordinate is a corresponding coordinate of such point
The use of decision trees for applying the method of analogy with the cognitive design of complex dynamical systems
Get PDFModern intelligent methods to extract knowledge from data allow the use of the available material for evaluation of the complexity of parts of different class, identify any patterns in the data and, thus, replace expert – technologist (quantity surveyor). In the analysis of pre-production, it is also advisable to go by the time required to manufacture the product to the price tag. Method of analogy is based on solving the dynamic problems of classification trees using algorithms solutions
A stochastic averaging method on the strongly nonlinear Duffing-Rayleigh oscillator under Gaussian colored noise excitation
Get PDFA modified stochastic averaging method on a Duffing-Rayleigh oscillator with strongly nonlinearity subject to Gaussian colored noise excitation was proposed. The so-called He’s energy balance method was applied to obtain the averaged frequency of the conservative system. Subsequently, the stochastic averaging method of strong nonlinearity was used. The modified method can offer more concise approximate expressions of the drift and diffusion coefficients without weakening the accuracy of predicting the responses of the systems too much. The stationary responses of probability density of amplitudes, together with joint probability density of displacement and velocity are studied to verify the presented approach. The reliability of the systems was also investigated to offer further support. Digital simulations were carried out and the output of that are coincide with the theoretical approximations well
Research into the characteristics of horizontal gaseous jets underwater
Get PDFThe gaseous jet of the solid rocket motor running under water is influenced by both gravity and buoyancy, which will have a significant influence on the flow field structure and thrust of the motor, especially in the initial period when vehicles are launching horizontally. The work in this paper consists of three parts: firstly, to understand the mechanism of the thrust oscillation characteristics and the jet structure of a solid rocket motor running under water, as affected by gravity and buoyancy, a 3-d numerical simulation using the volume of fluid (VOF) model was established. Compared with those results neglecting gravity and buoyancy, conclusions were obtained that the jet structure, considering gravity and buoyancy, are more consistent with the experimental results. Secondly, the principle of momentum was used to analyze the flow field structure and the thrust oscillating characteristics in the initial period of operation. Finally, after analyzing the density gradient along the axis of the motor, results indicated that the length of jets under the influence of gravity and buoyancy varies linearly and the slope of the line is related to the working conditions. Comparing the trajectories under different conditions, a common theme emerged. The laws of thermodynamics are also used to simulate the jets as gas-water-vapor, three-phase, systems. The effect of phase transitions on the structure of jets and the characteristics of their thrust form the key conclusions
New mixed adaptive detection algorithm for moving target with big data
Get PDFAiming at the troubles (such as complex background, illumination changes, shadows and others on traditional methods) for detecting of a walking person, we put forward a new adaptive detection algorithm through mixing Gaussian Mixture Model (GMM), edge detection algorithm and continuous frame difference algorithm in this paper. In time domain, the new algorithm uses GMM to model and updates the background. In spatial domain, it uses the hybrid detection algorithm which mixes the edge detection algorithm, continuous frame difference algorithm and GMM to get the initial contour of moving target with big data, and gets the ultimate moving target with big data. This algorithm not only can adapt to the illumination gradients and background disturbance occurred on scene, but also can solve some problems such as inaccurate target detection, incomplete edge detection, cavitation and ghost which usually appears in traditional algorithm. As experimental result showing, this algorithm holds better real-time and robustness. It is not only easily implemented, but also can accurately detect the moving target with big data