大时滞大惯性变频泵控马达调速系统研究

针对大时滞、大惯性负载变频泵控马达调速系统动态性能差的特点,提出了采用极点配置最优预报自校正PID控制.介绍了极点配置最优预报自校正PID控制器的结构和算法.仿真结果表明,基于极点配置最优预报自校正PID控制器不仅具有良好的动态特性,很强的鲁棒性和自适应性,而且调节快速,参数整定方法简单.     

基于改进模糊自适应的机械手阻抗控制研究

为解决因机械手非线性不确定系统、负载变化及力传感器测量不准确等引起的轨迹位置和接触力的控制问题,研究了一种反演自适应模糊控制方法。在目标阻抗控制模型上引入改进的力补偿以及自适应控制律,并采用Lyapunov函数证明了控制系统的稳定性,同时利用模糊理论设计了模糊控制系统完成目标阻抗参数的自整定,实现了无需依赖信息模型的力/位控制。以简化的二自由度机械手模型完成仿真实验。结果表明:该控制方法具有较好的力/位控制性能,系统鲁棒性较好。     

A neural network thrust force controller to minimize delamination during drilling of graphite-epoxy laminates

Delamination is a well-recognized problem associated with drilling fiber-reinforced composite materials (FRCMs). The most noted problems occur as the drill enters and exits the FRCM. Since drilling is often a final operation during assembly, any defects introduced in parts through the drilling process that result in the part being rejected represent an expensive loss. Studies based on linear-elastic fracture mechanics theory have proposed critical cutting and thrust forces in the various drilling regions that can be used as a guide in preventing crack growth or delamination. Using these critical force curves as a guide, a thrust force controller was developed to minimize the delamination while drilling a graphite-epoxy laminate. A neural network control scheme was implemented which required a neural network identifier to model the drilling dynamics and a neural network controller to learn the relationship between feed rate and the desired thrust force. Experimental results verifying the validity of this control approach as well as the robustness of the design are presented. Visual measurements of the delamination zones were used to quantify the benefits of the thrust force controlled drilling process versus the conventional constant feed rate drilling process.     

模糊自校正PID控制技术在线材活套控制中的应用

为提高线材热连轧活套的响应速度及鲁棒性,采用了先进的模糊自校正PID控制技术来改造活套控制系统,介绍了该系统的组成、动态数学模型及模糊自校正PID控制器的设计与仿真结果,结果表明,该控制器动态、静态和抗干扰性能均较理想。     

基于状态空间法的板料成形过程闭环控制系统的建模及仿真

冲压过程中,因材料的性能参数、润滑条件的波动和模具参数的改变,导致冲压件质量的不稳定,因此必须提高冲压件质量的控制鲁棒性。压边力是板料冲压过程的重要工艺参数之一,合理控制压边力的大小,可以避免起皱或破裂等缺陷。文章提出了一种基于结合RBF神经网络和经典状态空间理论的板料成形过程控制策略,并建立了其控制模型。引入时序分析法,将压边力的调整与反映工件成形质量的法兰边的吸入量误差联系起来,同时应用非线性最小二乘法识别出增益系数。仿真结果表明,在加入一噪声后,仍能获得满意的冲压件质量,模型具有较高的控制鲁棒性。     

Application of self-tuning feed-forward and cross-coupling control in a retrofitted milling machine

In this work, a traditional manually operated milling machine with a lead screw transmission system is retrofitted to AC servo motor control. This obsolescent milling machine has nonlinear time-varying behaviors due to obvious backlash and irregular Coulomb friction of the sliding surfaces. Classical digital control cannot assure the required stability and accuracy of a closed loop system. Hence, a pole placement self-tuning control strategy is proposed for this nonlinear time-varying system by introducing an on-line estimator of system parameters to adjust the feedback gains. Concepts of feed-forward and cross-coupling control are employed to improve the accuracy of trajectory tracking control. The experimental results show that this control method achieves satisfactory performance of stability, transient response, tracking and robustness under the influence of about 0.4 mm backlash on each axis and large stick-slip friction. This performance verifies the applicability of this economical approach to automation of traditional milling machines.     

电机电流的检测及其在模糊智能加工系统中的应用

分析了进给电机电流与相应的切削分力之间关系,用最小二乘法建立了它们之间的数学模型,以进给电机电流为监测切削负载的手段,实现了基于模糊芯片的铣削过程的模糊控制。     

Characteristics of cutting forces and chip formation in machining of titanium alloys

Chip formation during dry turning of Ti6Al4V alloy has been examined in association with dynamic cutting force measurements under different cutting speeds, feed rates and depths of cut. Both continuous and segmented chip formation processes were observed in one cut under conditions of low cutting speed and large feed rate. The slipping angle in the segmented chip was 55°, which was higher than that in the continuous chip (38°). A cyclic force was produced during the formation of segmented chips and the force frequency was the same as the chip segmentation frequency. The peak of the cyclic force when producing segmented chips was 1.18 times that producing the continuous chip.The undeformed surface length in the segmented chip was found to increase linearly with the feed rate but was independent of cutting speed and depth of cut. The cyclic force frequency increased linearly with cutting speed and decreased inversely with feed rate. The cutting force increased with the feed rate and depth of cut at constant cutting speed due to the large volume of material being removed. The increase in cutting force with increasing cutting speed from 10 to 16 and 57 to 75 m/min was attributed to the strain rate hardening at low and high strain rates, respectively. The decrease in cutting force with increasing cutting speed outside these speed ranges was due to the thermal softening of the material. The amplitude variation of the high-frequency cyclic force associated with the segmented chip formation increased with increasing depth of cut and feed rate, and decreased with increasing cutting speed from 57 m/min except at the cutting speeds where harmonic vibration of the machine occurs.     

面向电子压力机模糊神经网络PID控制的研究

针对电子压力机位置伺服系统的非线性和时变的不确定性,压装力、压装速度和压入深度高可控性,系统的高稳定性、适应性及较强的抗干扰能力等特点,提出将神经网络实现模糊PID自调整的控制特性应用在现存的小型电子压力机的位置伺服系统中的方法。该控制策略将模糊控制的推理能力和神经网络的学习能力进行了有效的结合,其中,PID控制器参数自调整是通过学习并记忆PID参数调整的基本规则来实现的,以满足电子压力机位置伺服系统的要求并用MATLAB软件编程进行仿真分析。仿真结果表明:相比较常规神经网络与传统PID相结合组成的控制器,模糊神经网络PID自调整控制器对于电子压力机的位置伺服系统具有更快的响应特性及更好的稳定性。     

升船机对接锁定机构竖向液压缸比例同步泄压系统设计与仿真

针对升船机对接锁定机构退出工作时,竖向液压缸比例同步泄压需要,设计了电液比例同步泄压回路。建立了比例泄压回路的数学模型;结合泄压过程中系统工作点在较大范围变化的特点,设计了基于模糊控制带前馈的自整定PI控制策略,通过前馈提高系统的响应速度,通过模糊控制来提高系统的鲁棒性。采用AMESim和MATLAB联合仿真的方法,验证了对接锁定机构电液比例泄压回路及控制策略的有效性。     

Adaptive turning force control with optimal robustness and constrained feed rate

In rough cutting operations, the typical economic objective is to maximize the metal removal rate by the highest possible feed rate under the constraint of tool breakage. This type of control strategy is called adaptive constraint control. However, the strategy has a poor industrial acceptance record because of the potential problems of controller instability and tool breakage resulting from the sudden change of cutting depth or spindle speed. In this paper, an adaptive turning force controller that has optimal robustness under the constraint of feed rate is presented. The experimental results for the sudden change of cutting depth are demonstrated. The proposed controller may be a promising method for the industrial application of turning force control.     

Constant turning force operation with a fixed metal removal rate via a prior fuzzy controller system

This study examines constant metal removal rate (MRR) with constant turning force (CTF) that operates by means of a prior fuzzy controller (PFC) that is able to automatically manipulate the spindle speed to maintain the MRR at a specified suitable value. Fuzzy-control techniques and grey theory are integrated to integrate a PFC into the constant turning force operation. The most important difference between the PFC and conventional fuzzy controller (FC) is that the fuzzy control signal is determined by the future predicted-state value obtained by a grey model instead of by the present-state value used in the traditional fuzzy controller (FC). Hence, the control signal can be obtained in advance and ensure the safety of the system. This study adopts an auxiliary fixed metal removal rate (MRR) controller, which can respond to the lathe power, machining roughness or tool chatter, and which in constant turning force (CTF) operations is adopted because when the controlled system is a non-linear function, as F_c = aK_ff^p, the productivity will always decrease. With the exponential function, the increase in cutting depth a will entail decrease in the feed f, thus reducing the metal removal rate (MRR), which is defined as MRR = afV_c (mm³ s⁻¹). A suitable solution is to increase the cutting speed V_c (mm s⁻¹). Consequently, the concept of the MRR is built into the auxiliary controller to improve the CTF control system.     

Fuzzy control of feed rate in end milling operations

In order to improve productivity in end milling operations, a new adaptive control system based on fuzzy logics to maintain a constant cutting force is developed. It is shown, by experimental cutting tests, that the cutting tool travels in the air cut with fast feed rate, yet in the varying depths of cut, the tool travels with an adjustable feed rate to prevent the occurrence of tool breakage and maintain a high metal removal rate.     

基于RBF神经网络电液恒功率调速自整定PID控制

采煤机电液调速系统对保证煤矿生产具有重要的作用。在分析恒功率自动调速的电液控制系统原理的基础上,建立了基于RBF神经网络自整定的PID控制的数学模型。通过在MATLAB/GUI仿真平台上计算得到系统的实际输出和模型输出的误差不超过5%,设计的RBF神经网络的电液恒功率调速自整定PID控制系统具有更高的跟踪精度和响应特性,完全可以实现系统的高精度与快速调速控制。     

An approach based on current and sound signals for in-process tool wear monitoring

This paper presents a tool condition monitoring system (TCMS) for on-line tool wear monitoring in turning. The proposed TCMS was developed taking into account the necessary trade-off between cost and performance to be applicable in practice, in addition to a high success rate. The monitoring signals were the feed motor current and the sound signal. The former was used to estimate the feed cutting force using the least squares version of support vector machines (LS-SVM). Singular spectrum analysis (SSA) was used to extract information correlated with tool wear from the sound signal. The estimated feed cutting force and the SSA decomposition of the sound signal alone with the cutting conditions constitute the input data to the TCMS. Again LS-SVM was used to estimate tool condition and its reliability for on-line implementation was validated by experiments using AISI 1040 steel. The results showed that the proposed TCMS is fast and reliable for tool condition monitoring.     

机器人恒力磨抛材料去除研究

针对传统机器人-砂带磨抛工件时材料去除量难以定量控制的问题,结合Preston磨削经验公式与赫兹弹性接触理论,将法向磨抛力、砂带速度、工件进给速度3个工艺参数作为变量,建立机器人恒力磨抛的材料去除深度模型;然后进行硬件选型,搭建机器人恒力磨抛实验平台;最后以上述3个工艺参数为变量设计了机器人恒力磨抛单因素实验,实验结果...     

高速大推力直线电机直接驱动进给系统动态性能的分析

大推力直线电机直接驱动是一种新颖的高速数控机床直线进给系统驱动方式,它将直线电机的定子和动子分别安装在机床床身和工作台上,取消一切机械传动环节,大大提高进给系统的伺服性能,但这种驱动方式对外界干扰非常敏感,机床运行过程中切削力甚至进给系统运动部件质量的变化等均是系统的直接干扰.本文根据直接驱动进给系统的控制模型,分析了系统动态刚度的计算方法和主要影响因素,提出了提高动态性能的方法.根据系统的特点,设计动态质量估计器,实现直接驱动进给系统的动态质量在线估计和补偿.对实际系统的仿真分析表明,本文提出的基于系统动态质量在线估计与补偿方法,能大大提高系统的性能.     

基于模糊自整定参数PID控制的铝合金薄板脉冲MIG焊

针对铝合金薄板脉冲MIG焊,提出了一种比例积分微分(proportion integral derivative,PID)参数模糊自整定控制方法,文中介绍了其原理及设计思路,将模糊逻辑控制器引入已建立的PID控制器的Simulink仿真模型,实现了PID参数模糊自调节,并进行了输入适应性对比试验和抗干扰试验分析,表明PID参数模糊自整定控制器在输入适应性和抗干扰方面更胜一筹,能进一步提高弧焊电源性能.最后对铝合金1 mm薄板进行了传统PID控制和模糊自整定参数PID控制焊接试验对比.结果表明,该方法焊缝光亮、飞溅少、焊接过程比较平稳,可获得较好的焊缝质量和稳定的焊接过程.     

A Cutting Force Estimator for CNC Machining Centers

This study presents a cutting force estimator topology for feed drives of CNC vertical machining centers to compute the machining forces accurately. The estimator employs recursive discrete Fourier transform to not only estimate inertial forces on the system but also to filter effectively the noise components in the measurements. The accuracy of the estimator is compared to that of a Luenberger observer while the overall performance of the estimator is evaluated through an experimental study. The paper also discusses its inherent limitations.     

基于状态观测器增益自调整的交流伺服系统

针对永磁同步交流伺服系统易受机械参数的变化和负载扰动的影响,论文设计了一个负载观测器,并采用递推最小二乘法对系统的转动惯量和粘滞摩擦系数进行了在线辨识,然后用辨识得到的转动惯量和粘滞摩擦系数对系统参数进行更新,保证了观测器的精度。采用极点配置法设计的观测器增益可以根据前面估计得到的转动惯量和粘滞摩擦系数在线调整,使该观测器在自身的机械参数发生剧烈变化时,仍能准确地观测突加的外部负载扰动进行补偿,大大提高了伺服系统的精度。仿真结果表明,系统在转动惯量和粘滞摩擦系数发生变化时,基于负载观测器增益自调整的高精度永磁交流伺服系统无论是在上升时间,速度跟踪的精确性和鲁棒性方面都优于传统的负载观测器的增益固定的控制方案。