数控机械机床维护与保养策略

数控机械机床是机电一体化应用程度非常高的一种产品,其在现代机械生产过程中发挥着非常重要的作用,因此应当重视机床的应用维护和保养。本文以某数控机械机床应用故障为例,说明数控机械机床维护与保养的重要性,并在此基础上就如何进行维护和保养,谈一下自己的观点和认识,以供参考。

电动铲运机卷缆装置的数控方法研究

卷缆系统是矿山电动铲运机的重要部分,其自动放缆、自动收缆的可靠性直接影响着铲运机的工作效率。通过提出一种数控策略,设计了数控卷缆装置,从而提高了卷缆装置的可靠性和自动化程度。

面向高速切削加工的数控编程技术研究

高速加工数控编程技术是高速加工研究的关键内容之一,它极为重要也非常复杂。针对高速切削加工的特点,提出了新的数控加工编程策略,深入分析了高速粗加工和精加工过程中走刀路径的优化。通过这样的优化科学地编出最优、最实际的高速铣削数控加工程序,充分发挥高速铣削加工的特长。从而缩短零件的生产工艺过程,增加切削余量的去除率,提高表面的加工精度。

浅谈如何有效培养中职生的数控技能

数控技能的培养是中职生学习的重要任务之一,这正是适应社会需要大量技术型的人才的需要,如何比较有效地培养中职生的数控技能,以使他们毕业后能尽快适应岗位,适应社会,本文结合教学实际,从社会需求、课程教学和方案实施等方面作了一定的探讨。

数控机床维修改造中的问题与对策研究

数控机床技术的应用对机电一体化进程的加快具有重要意义。随着经济的发展和社会的进步,数控机床技术也在不断的进行更新和发展。数控机床技术在使用过程中与传统的技术相比,具有结构复杂、多元化的特点,代表了数控机床技术在进行维修改造时,需要投入大量的人力、物力。这与企业效益为先的经济发展形式不符,需要进行改造和创新。

Active Control of Structurally Radiated Sound from an Elastic Cylindrical Shell

A numerical and experimental study was presented on active control of structurally radiated sound from an elastic cylindrical shell.An analytical model was developed for the active structural acoustic control (ASAC) of the cylindrical shell.Both global and local control strategies were considered.The optimal control forces corresponding to each control strategy were obtained by using the linear quadratic optimal control theory.Numerical simulations were performed to examine and analyze the control performance under different control strategies.The results show that global sound attenuation of the cylindrical shell at resonance frequencies can be achieved by using point force as the control input of the ASAC system.Better control performance can be obtained under the control strategy of minimization of the radiated sound power.However,control spillover may occur at off-resonance frequencies with the control strategy of structural kinetic energy minimization in terms of the radiated sound power.Considerable levels of global sound attenuation can also be achieved in the on-resonance cases with the local control strategy,i.e.,minimization of the mean-square velocity of finite discrete locations.An ASAC experiment using an FXLMS algorithm was implemented,agreement was observed between the numerical and experimental results,and successful attenuation of structural vibration and radiated sound was achieved.

On Prediction of Longitudinal Attitude of Planing Craft Based on Controllable Hydrofoils

The purpose of this research study was to examine the attitude response of a planing craft under the controllable hydrofoils.Firstly,a non-linear longitudinal attitude model was established.In the mathematical model,effects of wind loads were considered.Both the wetted length and windward area varied in different navigation conditions.Secondly,control strategies for hydrofoils were specified.Using the above strategies,the heave and trim of the planing craft was adjusted by controllable hydrofoils.Finally,a simulation program was developed to predict the longitudinal attitudes of the planing craft with wind loads.A series of simulations were performed and effects of control strategies on longitudinal attitudes were analyzed.The results show that under effects of wind loads,heave of fixed hydrofoils planing craft decreased by 6.3%,and pitch increased by 8.6% when the main engine power was constant.Heave decreased by less than 1% and trim angle decreased by 1.7% as a result of using variable attack angle hydrofoils;however,amplitude changes of heave and pitch were less than 1% under the control of changeable attack angle hydrofoils and longitudinal attitude.

Design and application of electric oil pump in automatic transmission for efficiency improvement and start–stop function

For the purpose of improving efficiency and realizing start–stop function, an electric oil pump(EOP) is integrated into an 8-speed automatic transmission(AT). A mathematical model is built to calculate the transmission power loss and the hydraulic system leakage. Based on this model, a flow-based control strategy is developed for EOP to satisfy the system flow requirement. This control strategy is verified through the forward driving simulation. The results indicate that there is a best combination for the size of mechanical oil pump(MOP) and EOP in terms of minimum energy consumption. In order to get a quick and smooth starting process, control strategies of the EOP and the on-coming clutch are proposed. The test environment on a prototype vehicle is built to verify the feasibility of the integrated EOP and its control strategies. The results show that the selected EOP can satisfy the flow requirement and a quick and smooth starting performance is achieved in the start–stop function. This research has a high value for the forward design of EOP in automatic transmissions with respect to efficiency improvement and start–stop function.

Inventory control model based on external and interior reverse logistics

To improve the inventory control strategy for enterprise and optimize inventory control parameters of existing external and interior reverse logistics, a multi-resource inventory control model is proposed to better simulate the logistics fact, which is aimed at periodic inventory checking and pull mode of inventory control strategy, based on the return product arrival time obeying Poisson distribution, the return product employing lotsize process and the nonzero lead time of manufaeturinge/remanufacturing. The rational cost function with multiple constraints is employed to describe the inventory model. The genetic algorithm is employed to solve the inventory cost function to obtain the optimal solution of inventory checking periods, safe inventory point, product lot-sizes and process lot-sizes of return product. An example is presented to prove the feasibility and validity of the proposed method. Moreover, the influence of manufacturing/remanufacturing lead time and reuse rate of return production on the inventory control strategy of enterprise is analyzed.

Sliding-mode control of path following for underactuated ships based on high gain observer

A nonlinear robust control strategy is proposed to force an underactuated surface ship to follow a predefined path with uncertain environmental disturbance and parameters.In the controller design,a high-gain observer is used to estimate velocities,thus only position and yaw angle measurements are required.The control problem of underactuated system is transformed into a control of fully actuated system through adopting an improved line-of-sight(LOS) guidance law.A sliding-mode controller is designed to eliminate the yaw angle error,and provide the control system robustness.The control law is proved semi-globally exponentially stable(SGES) by applying Lyapunov stability theory,and numerical simulation using real data of a monohull ship illustrates the effectiveness and robustness of the proposed methodology.

Hybrid Improved Self-adaptive Differential Evolution and Nelder-Mead Simplex Method for Solving Constrained Real-Parameters

In this paper, a new hybrid algorithm based on exploration power of a new improvement self-adaptive strategy for controlling parameters in DE （differential evolution） algorithm and exploitation capability of Nelder-Mead simplex method is presented （HISADE-NMS）. The DE has been used in many practical cases and has demonstrated good convergence properties. It has only a few control parameters as number of particles （NP）, scaling factor （F） and crossover control （CR）, which are kept fixed throughout the entire evolutionary process. However, these control parameters are very sensitive to the setting of the control parameters based on their experiments. The value of control parameters depends on the characteristics of each objective function, therefore, we have to tune their value in each problem that mean it will take too long time to perform. In the new manner, we present a new version of the DE algorithm for obtaining self-adaptive control parameter settings. Some modifications are imposed on DE to improve its capability and efficiency while being hybridized with Nelder-Mead simplex method. To valid the robustness of new hybrid algorithm, we apply it to solve some examples of structural optimization constraints.

Robust Control of Time Delay Systems

This study presents the design of both H∞ Loop Shaping Control （HLSC） and Internal Model Control （IMC） strategies for linear time delay systems. For first order time delay system, a systematic approach for weight selection based on the sensitivity function was proposed, then compared to the internal model control strategy. For both methods, the synthesis was based on the Pade approximation. Two cases are considered for time delay： upper or lower than system time constant. Simulation results for the proposed approaches are acceptable ever in presence of disturbances and model mismatches.

Effect of the coordinated reset stimulations on controlling absence seizure

Based on a macroscopic mean-field model associating with the thalamus and cerebral cortex, we investigate how the newly proposed coordinated reset stimulation(CRS) strategy controls the absence seizures as some key parameters are changed.Different from the previous stimulation processes, CRS represents the intermittent pulse current administered to different structures including cortex, specific relay nuclei(SRN) and thalamus reticular nucleus(TRN) at different time by using three different micro-electrodes. In particular, we first simulate a typical absence epilepsy activity under the combined effect of the coupling strength between inhibitory interneurons(IIN)-excitatory pyramidal neurons(EPN) and EPN-TRN pathway. And then we explore the control mechanism of different parameters of 3:2 ON-OFF CRS on spike and slow-wave discharges(SWDs)region. Through analyzing the corresponding two-dimensional bifurcation diagrams, we find CRS is effective on controlling absence seizures in proper ranges of stimulation parameters. Especially, the combination of frequency and positive input duration can inhibit the pathological area more effectively. The obtained results might be helpful to study the pathophysiology mechanism of epilepsy, although the CRS's feasibility still needs further exploration in clinical experiments.

Event-Triggered Consensus for Multiple Nonholonomic Systems

The paper investigates the consensus problem of multiple nonholonomic systems. Two event-triggered control strategies, one centralized and the other distributed, are developed, which can reduce the frequency of control updating. Under the proposed protocols, the multiple nonholonomic systems can achieve consensus, and the bound of inter-event time intervals is provided to illustrate that no Zeno behavior exists. Finally, numerical simulations are also provided to demonstrate the effectiveness of the proposed control strategies.

Mixed H_∞ and Passive Projective Synchronization for Fractional Order Memristor-Based Neural Networks with Time-Delay and Parameter Uncertainty

This paper investigates the mixed Ho~ and passive projective synchronization problem for fractional-order （FO） memristor-based neural networks. Our aim is to design a controller such that, though the unavoidable phenomena of time-delay and parameter uncertainty are fully considered, the resulting closed-loop system is asymptotically stable with a mixed H∞ and passive performance level. By combining active and adaptive control methods, a novel hybrid control strategy is designed, which can guarantee the robust stability of the closed-loop system and also ensure a mixed H∞ and passive performance level. Via the application of FO Lyapunov stability theory, the projective synchronization conditions are addressed in terms of linear matrix inequaiity techniques. Finally, two simulation examples are given to illustrate the effectiveness of the proposed method.

Feedback control for manipulating magnetization in spin-exchange optical pumping system

Control of magnetization plays an important role in the scientific and technological field of manipulating spin systems. In this work, we study the problem of manipulating nuclear magnetization in the spin-exchange optical pumping system, including accelerating the recovery of nuclear polarization and fixing it on a specific desired state. A real-time feedback control strategy is exploited here. We have also done some numerical simulations, with the results clearly demonstrating the effectiveness of our method, that the nuclear magnetization is able to be driven towards the equilibrium state at a much faster speed and also can be stabilized to a target state. We expect that our feedback control method can find applications in gyro experiments.

Role of precautionary measures in HIV epidemics： A mathematical assessment

United Nations Political Declaration 2011 on HIV and AIDS calls to reduce the sexual transmission and the transmission of HIV among people, who inject drugs by 50% by 2015, through different control strategies and precautionary measures. In this paper, we propose and study a simple SI type model that considers the effect of various precaution- ary measures to control HIV epidemic. We show, unlike conventional epidemic models, that the basic reproduction number which essentially considered as the disease eradica- tion condition is no longer sufficient to eliminate HIV infection. In particular, we show that even when the basic reproduction number is made less than unity, the disease may persist if the initial outbreak is not low. Eradication of disease is however guaranteed if the ensemble control measure exceeds some upper critical value. It is also shown that an epidemic model with mass action incidence may exhibit backward bifurcation and bistability if density-dependent demography is considered. Our theoretical study thus indicates that extra attention should be given in controlling HIV epidemic to achieve the desired result.