风火打捆传统直流外送系统中控制环节对轴系-控制交互模式的影响机理研究

风火打捆直流外送系统中风电场和电网换相换流器高压直流输电(line commutated converter based high voltage direct current,LCC-HVDC)控制系统可能会激发火电机组的轴系扭振。文章首先采用复转矩系数法和特征值分析法识别出LCC-HVDC定电流、风机直流电压外环控制是影响轴系-控制交互模式的关键控制环节。然后,通过推导系统传递函数,提取出反映LCC-HVDC定电流和风机直流电压外环控制对轴系-控制交互模式影响的多条关键控制路径,包括HVDC定电流控制路径、风机直流电压外环控制路径和两者间交互控制路径。进一步,定量计算每条作用路径在轴系-控制交互模式处的阻尼系数,并通过相位补偿在关键控制路径上分别设计附加阻尼控制来提高对应阻尼系数,从而抑制火电机组轴系扭振。最后,基于PSCAD/EMTDC的详细电磁暂态仿真,验证了理论分析的正确性及振荡抑制策略的有效性。

基于磁流变弹性体的推进轴系半主动式吸振器研究

根据船舶推进轴系纵振动力学特性,针对动力吸振器的减振机理进行研究,并对半主动式吸振器的设计参数影响规律进行理论分析。基于磁流变弹性体的剪切模量可由外加磁场控制的特性,设计了一种剪切刚度可调的半主动式吸振器,对其移频特性进行了试验测试,并在1∶4的船舶轴系缩比模型上进行了变转速工况下吸振效果试验。实验结果表明,该吸振器具有12.3 Hz的移频范围,移频特性曲线线性度良好;并且在不同转速下相比被动式吸振器均有更好的吸振效果,进一步验证了利用磁流变弹性体设计推进轴系半主动式吸振器的可行性。

基于CAD/CAM的舰船螺旋桨精度控制技术研究

为解决船舶螺旋桨内部角动量不平衡、精准解耦能力较弱等问题,提出基于CAD/CAM的船舶螺旋桨精度控制方法。通过控制轴系确定、定点坐标变换2个步骤,完成船舶螺旋桨结构的CAD/CAM建模。在此基础上,通过铣削方式与加工路径分析、残余精度量计算、微小控制误差确定3个步骤,完成新型精度控制方法的搭建,实现基于CAD/CAM的船舶螺旋桨精度控制技术研究。对比实验结果表明,与传统控制方法相比,应用新型精度控制方法后,船舶螺旋桨内部角动量呈现明显的平衡状态,精准解耦能力最大值可达到70%。

主动控制技术在船舶振动噪声控制中的应用

低频线谱噪声是船舶的“声指纹”特征,影响船舶的隐蔽性,而主动控制技术是抑制船舶低频线谱振动噪声的重要方法。为此,首先简要介绍了船舶低频线谱噪声的主要传递路径;然后,从船舶机械主被动隔振技术、船舶管路噪声主动控制技术、船舶推进轴系纵向和横向振动控制技术等方面,综述了近年来船舶振动与噪声主动控制技术的国内外研究进展和应用情况,梳理了技术应用的难点,对技术发展趋势进行了展望。

Visible and Infrared Band Tracking and Measuring Control System

This paper describes a new tracking and measuring control system for optical and electronic theodolite.This control system can provide automatic flying object tracking and measuring in visible and infrared band.It also can provide real-time output of the measured results.By using the multi-mode measuring methods and the on-axis tracking control technique, the stability of automatic tracking,tracking accuracy and the comprehensive tracking performance of the theodolite can be improved.At the same time the smooth switch-over among several tracking modes can be carried out.New tracking techniques have been developed to deal with angular tracking rate that exceed 60 deg/s in velocity and 90 deg/s 2 in acceleration.At the present the tracking and measuring control system has been successfully applied in the optical and electronic theodolite.

Torsional vibration active control of hybrid construction machinery complex shafting

Due to the coaxial connection of engine, motor and pump, the dynamic characteristics of hybrid construction machinery are changed, which generates a new torsional vibration problem of multi-power sources. To reduce the torsional vibration of the hybrid construction machinery complex shafting, torsional vibration active control was proposed. The three-mass model of coaxial shafting of hybrid construction machinery was established. The PID control and the fuzzy sliding mode control were chosen to weaken torsional vibration by controlling the motor speed and torque. The simulation results show that the fuzzy sliding mode control has 12% overshoot of the PID control when the engine torque changes. The active control is effective and can realize smooth power switch.

The development of real time data driving multi-axis linkage and synergic movement control system of 3D variable cross-section roll forming machine

The three dimensional variable cross-section roll forming is a kind of new metal forming technol- ogy which combines large forming force, multi-axis linkage movement and space synergic movement, and the sequential synergic movement of the ganged roller group is used to complete the metal sheet forming according to the shape of the complicated and variable forming part data. The control system should meet the demands of quick response to the test requirements of the product part. A new kind of real time data driving multi-axis linkage and synergic movement control strategy of 3D roll forming is put forward in the paper. In the new control strategy, the forming data are automatically generated according to the shape of the parts, and the multi-axis linkage movement together with cooperative motion among the six stands of the 3D roll forming machine is driven by the real-time information, and the control nodes are also driven by the forming data. The new control strategy is applied to a 48 axis 3D roll forming machine developed by our research center, and the control servo period is less than 10ms. A forming experiment of variable cross section part is carried out, and the forming preci- sion is better than ＋ 0.5mm by the control strategy. The result of the experiment proves that the control strategy has significant potentiality for the development of 3D roll forming production line with large scale, multi-axis ganged and svner^ic movement

Contouring error modeling and simulation of a four-axis motion control system

A layered modeling method is proposed to resolve the problems resulting from the complexity of the error model of a multi-axis motion control system. In this model, a low level layer can be used as a virtual axis by the high level layer. The first advantage of this model is that the complex error model of a four-axis motion control system can be divided into several simple layers and each layer has different coupling strength to match the real control system. The second advantage lies in the fact that the controller in each layer can be designed specifically for a certain purpose. In this research, a three-layered cross coupling scheme in a four-axis motion control system is proposed to compensate the contouring error of the motion control system. Simulation results show that the maximum contouring error is reduced from 0.208 mm to 0.022 mm and the integration of absolute error is reduced from 0.108 mm to 0.015 mm, which are respectively better than 0.027 mm and 0.037 mm by the traditional method. And in the bottom layer the proposed method also has remarkable ability to achieve high contouring accuracy.

Harmonic amplitude-phase adaptive control and its application in three-axis simulators

This paper proposes a compensation method for using the Harmonic Amplitude-Phase Adaptive Control(HAPAC)to increase the precision of sinusoidal motion simulators. It also expounds on the HAPAC principle and structural disposition, develops the HAPAC control laws and analyzes the system stability in the HAPAC. A method for further improving the precision using online identification of the system’s frequency-response models is presented. The tested data and tracking errors of the simulator demonstrate that the HAPAC makes the sinusoidal motions achieve higher precision than the common classical controls. The HAPAC can also be used in other tracking systems of precision sinusoidal motions.

Effects of Unequal Couplings on Fidelity of a Quantum Controlled-Controlled-Not Gate

By numerically solving the Sch6dinger equation of a three-nuclear-spin system, the effects of the non-uniform nearest-neighbor （NN） interaction on the fidelity of a quantum controlled-controlled-no （CCN） gate are investigated for a digital initial state and a superposition initial state respectively. It is found from our simulation that the ratio of the deviation of the NN coupling δJ to the NN coupling J should be smaller than 0.0005 to ensure a high fidelity of the quantum CCN gate.

A Study on the Levitation Control of the Multi-degrees-of-Freedom Rotational Machine Supported by Magnetic Bearings Using Flux Feedback

This paper deals with an open-loop characteristic of a magnetically levitated system including flux feedback. In order to design a controller to obtain a good disturbance rejection and to be insensitive to parameter variations, it might be useful to employ a flux feedback loop. The air gap flux which can be sensed by a proper sensor has linear relationship with respect to the change of the current and the air gap. This linear property decreases the inherent nonlinearity of the magnetic suspension system that is caused by the coupling between the electrical actuator and the mechanical plant. Simulation results achieved from a multi-degree-of-freedom numerical model show that the flux feedback loop makes an improvement of the performance of the magnetic suspension system against the load variations.

Robust adaptive cross-coupling position control of biaxial motion system

The stability and synchronous performance are usually hard to be improved simultaneously in the biaxial cross-coupling position motion control system.Based on analyzing the characteristics of the cross-coupling control system,a robust adaptive cross-coupling control strategy is proposed.To restrict influences of destabilizing factors and improve both of stability and synchronous performance,the strategy forces dual axes to track the same reference model using Narendra adaptive control theory.And then,a robust parameters adaptive law is proposed.The stability analysis of the proposed strategy is conducted by applying Lyapunov stability theory.Related simulations and experiments indicate that the proposed strategy can improve synchronous performance and stability simultaneously.

Nonlinear optimal control of rotating flexible shaft in active magnetic bearings

The optimal control of nonlinear systems has been studied for years by many researchers. However, the application of optimal control problem to nonlinear non-affine systems needs more attention. In this paper we propose an optimal control design technique for a class of nonlinear and control non-affine equations. The dynamic equations of a flexible shaft supported by a pair of active magnetic bearings (AMBs) are used as the nonlinear control non-affine equations. Mathematical model for the flexible beam is chosen to be the well known Timoshenko beam model, which takes rotary inertia and shear deformations into account, and it is assumed that the shaft is supported by two frictionless bearings at the ends. The effective control of such systems is extremely important for very high angular velocity shafts which are a feature of many modern machines. The control must be able to cope with unbalanced masses and hence be very robust. We shall approach the problem by discretising the Timoshenko beam model and using standard difference formulae to develop a finite-dimensional model of the system. Then we use a recently developed technique for controlling nonlinear systems by reducing the problem to a sequence of linear time-varying (LTV) systems. An optimal control designed for each approximating linear, time-varying system and recent results show that this method will converge uniformly on compact time intervals to the optimal solution.

Cross-coupled controller design for triaxial motion systems based on second-order contour error estimation

The cross-coupled control(CCC)is widely applied to reduce contour errors in contour-following applications.In such situation,the contour error estimation plays an important role.Traditionally,the linear or second-order estimation approach is adopted for biaxial motion systems,whereas only linear approach is available for triaxial systems.In this paper,the second-order contour error estimation,which was presented in our previous work,is utilized to determine the variable CCC gains for motion control systems with three axes.An integrated stable motion control strategy,which combines the feedforward,feedback and CCC controllers,is developed for multiaxis CNC systems.Experimental results on a triaxial platform indicate that the CCC scheme based on the second-order estimation,compared with that based on the linear one,significantly reduces the contour error even in the conditions of high tracking feedrate and small radius of curvature.