面向多机动态调度问题的两层Q学习算法

对于单机动态调度问题十分有效的Q学习,在多机动态调度环境下却由于缺乏全局眼光而效果欠佳,因此提出了一种双层Q学习算法.底层Q学习着眼于局部,以最小化设备空闲和作业平均流经时间为目标,学习单机调度策略;而顶层Q学习则着眼于全局,以平衡机器负载、最小化整体拖期值为目标,学习如何分配作业到合适机器.文中分别给出了两层Q学习的动作集、状态空间划分方式和奖惩函数设计,并通过对多机动态调度问题的仿真实验表明,提出的双层Q学习能够很好地解决改善动态环境下多机调度问题.

Inchworm locomotion gait for snakelike robot

To establish a universal and easily controlled gait for practical use of snakelike robot movement, an inchworm locomotion gait model based on a serpenoid curve is presented. By analyzing the relations of two adjacent waves in the process of locomotion and doing an approximation of the serpenoid curve, the motion function of relative angles between two adjacent links and the absolute angles between each link and the baseline on the traveling curve are built. Two efficiency criterions of the gait are given as the energy loss function f and the unit displacement in one cycle dunit.Three parameters of the criterions affecting the efficiency of the gait （ the number of links that form the traveling wave n, the included angle between two adjacent links α, and the phase difference of adjacent included angles β） are discussed by simulations and experiments. The results show that f is insensitive to n; raising n increases dunit significantly; the maximum wave amplitude of α is a decreasing function of n; and increasing α reduces the displacement influence off when n is determined. The gait model is suitable for different inchworm locomotions of a snakelike robot whose traveling waves are formed by different numbers of identical links. A wave formed by more links or a greater relative angle between two adjacent links both lead to greater velocity of the movement.

Nonlinear multi body dynamic modeling and vibration analysis of a double drum coal shearer

The double drum coal shearer is widely applied for the underground coal exploration in the mining industry.The vibration and noise control are significant factors for the stability design of the double drum coal shearer.In this paper,the vibration properties of a double drum coal shearer are firstly investigated.The horizontal,transverse and torsional vibrations of the motor body and the angle displacements of the rockers are taken into account.The walking units and the hydraulic units are modeled by the stiffness-damping systems.The nonlinear equation of motion of the double drum coal shearer is established by applying the Lagrange’s equation.The nonlinear vibration response of the system is calculated by using the Runge Kutta numerical method.The effects of the shearing loads,the equivalent damping and stiffness of the walking units,the inclination angels of the rockers and the equivalent damping and stiffness of the hydraulic units on the vibration properties of the system are discussed.

Coupling problem between the dynamical and tribological behaviors in the piston-liner systems of multi-cylinder IC engines

This paper deals with the coupling problem between the dynamic behaviors and the tribological behaviors of the piston-liner systems in multi-cylinder internal combustion engines. Firstly, based on the correction of some errors in the equation of piston secondary motion, which have been employed by many authors for several years, a detailed mathematical model for the coupling problem between the dynamical and tribological behaviors in the piston-liner systems of multi-cylinder internal combustion engines is presented. Secondly, the lubrication and friction between the liner and piston in each cylinder is included applying the average flow model of the Reynolds equation. Thirdly, the vibration of each liner is computed through the finite element model of a four-cylinder engine block, by which not only the liner motions caused by the block vibration but also the local vibration and the local static deformation of each liner can be figured out and taken into account. Through theoretical analysis and computation, some conclusions can be drawn as: 1) Both the liner vibration and piston motion are different for different cylinder in a multi-cylinder internal combustion engine, and hence different piston-liner systems will have different tribological behaviors. 2) Different liners have coincident dynamic response on the whole, especially for the lower frequency components. However, differences still exist among the vibrations of different liners, and these differences are mainly owing to the higher frequency components. 3) The impacts of liner vibrations on the tribological behaviors in piston-liner systems are primarily ascribed to its higher frequency components.

Engine Noise Prediction by Using Multi-body Simulation

Abstract： This paper presents a coupled multi-body and FEM （finite element method）-BEM （boundary element method） methodology used to carry out a comprehensive NVH （noise, vibration and harshness） investigation of a four-cylinder internal combustion engine prototype. Firstly, a MBDS （multi-body dynamic simulation） of the internal combustion engine has been carried out, at a defined operating condition, in order to determine the excitation force of the powertrain exciting the cylinder block. In this way, the dynamics of the engine powertrain have been described taking into account both the effects of the gas forces of the combustion process and the inertia forces of the moving parts. Afterwards, the cylinder block excitation forces have been used to evaluate the engine block vibrations and to predict the external noise radiated with both the well-known ATV （acoustic transfer vectors） and MATV （modal acoustic transfer vectors） methodologies at a distance of 1 m from the engine, according to the standard ISO 3744. The dynamics of the engine powertrain and its vibro-acoustic behaviour have been described using LMS （learning management system） Engineering Innovation Virtual.Lab tools.

Dynamic Visualization Approach of the Multiphase Flow Using Electrical Capacitance Tomography

Identifying the flow patterns is vital for understanding the complicated physical mechanisms in multiphase flows.For this purpose,electrical capacitance tomography(ECT) technique is considered as a promising visualization method for the flow pattern identification,in which image reconstruction algorithms play an important role.In this paper,a generalized dynamic reconstruction model,which integrates ECT measurement information and physical evolution information of the objects of interest,was presented.A generalized objective functional that simultaneously considers the spatial constraints,temporal constraints and dynamic evolution information of the objects of interest was proposed.Numerical simulations and experiments were implemented to evaluate the feasibility and efficiency of the proposed algorithm.For the cases considered in this paper,the proposed algorithm can well reconstruct the flow patterns,and the quality of the reconstructed images is improved,which indicates that the proposed algorithm is competent to reconstruct the flow patterns in the visualization of multiphase flows.

Multi-dimension and multi-modal rolling mill vibration prediction model based on multi-level network fusion

Mill vibration is a common problem in rolling production,which directly affects the thickness accuracy of the strip and may even lead to strip fracture accidents in serious cases.The existing vibration prediction models do not consider the features contained in the data,resulting in limited improvement of model accuracy.To address these challenges,this paper proposes a multi-dimensional multi-modal cold rolling vibration time series prediction model(MDMMVPM)based on the deep fusion of multi-level networks.In the model,the long-term and short-term modal features of multi-dimensional data are considered,and the appropriate prediction algorithms are selected for different data features.Based on the established prediction model,the effects of tension and rolling force on mill vibration are analyzed.Taking the 5th stand of a cold mill in a steel mill as the research object,the innovative model is applied to predict the mill vibration for the first time.The experimental results show that the correlation coefficient(R^(2))of the model proposed in this paper is 92.5%,and the root-mean-square error(RMSE)is 0.0011,which significantly improves the modeling accuracy compared with the existing models.The proposed model is also suitable for the hot rolling process,which provides a new method for the prediction of strip rolling vibration.

Dynamic Simulations of Post-stall Performance in Multistage Axial Compressors

In this contribution a quasi-one-dimensional tool for stationary and transient simulations of post-stall flows in multistage axial compressors is presented. An adapted version of the 1D Euler equations with additional source terms is discretized with a finite volume method and solved in time by a fourth-order Runge-Kutta scheme. The equations are discretized at midspan both inside the blade rows and the non-bladed regions. The source terms express the blade-flow interactions and are estimated by calculating the velocity triangles for each blade row. Loss and deviation correlations are implemented and compared to experimental data in normal flow, stalled flow and reversed flow regions. Transient simulations are carried out and a parameter study is presented to analyze the shape of the surge cycles and the frequency of the surge oscillations. At last, a bleeding control strategy is implemented to study the recoverability of the instabilities in a compression system.

Analysis of some large-scale nonlinear stochastic dynamic systems with subspace-EPC method

The probabilistic solutions to some nonlinear stochastic dynamic (NSD) systems with various polynomial types of nonlinearities in displacements are analyzed with the subspace-exponential polynomial closure (subspace-EPC) method. The space of the state variables of the large-scale nonlinear stochastic dynamic system excited by Gaussian white noises is separated into two subspaces. Both sides of the Fokker-Planck-Kolmogorov (FPK) equation corresponding to the NSD system are then integrated over one of the subspaces. The FPK equation for the joint probability density function of the state variables in the other subspace is formulated. Therefore, the FPK equations in low dimensions are obtained from the original FPK equation in high dimensions and the FPK equations in low dimensions are solvable with the exponential polynomial closure method. Examples about multi-degree-offreedom NSD systems with various polynomial types of nonlinearities in displacements are given to show the effectiveness of the subspace-EPC method in these cases.