Iterative learning control of electro-hydraulic proportional feeding system in slotting machine for metal bar cropping

A non-linear method, iterative learning control (ILC), is proposed to control the electro-hydraulic feeding process of a new slotting machine. The method attempts to acquire high precision of feeding length and trapezoid feedrate, whereas the complexity of iterative learning control algorithm does not increase much more than that of industrial PID controller. After an analysis of the two-way proportional feeding system, a non-linear dynamical mathematic model with system delay, saturation and dead-zone is developed. The computer flowrate control and the ILC controller are investigated in detail. PID controller, ILC of displacement and ILC of feedrate are compared with the dynamical model under the same desired trajectory. It is experimentally found that the proposed control scheme is more effective to improve the tracking accuracy of hydraulic feeding system of the slotting machine than that of fuzzy PID controller.     

烧结压机的伺服油泵电控、液压系统设计

对现有烧结压机设备进行改进,采用伺服油泵系统替代电液比例阀控制系统,详细论证分析伺服油泵系统的工作原理、电气控制及PLC控制伺服电机流程,同时比较伺服油泵系统与普通比例阀系统在应用过程中的优缺点。改进后经客户使用,结果显示:烧结压机中伺服液压系统压力控制精度为±0.1 MPa,稳定了产品质量;噪音由65 dB降到45 dB,改善了工作环境;烧结压机油箱温度较没改进前降低12.5℃,节能效果明显;延长了液压元件的使用寿命,降低设备的维护成本;提高了烧结压机设备稳定性。      

Shape accuracy in the forming of deep holes with retreat and advance pulse ram motion on a servo press

A method for keeping lubrication in the backward extrusion of deep holes for lightweight structural components is proposed utilizing a servo press and a punch with an internal channel for liquid lubricant supply. The punch is pushed into the specimen with a servo press in a manner that combines pulsed and stepwise modes. Sufficient liquid lubricant is periodically supplied to the deformation zone through the internal channel upon the retreat of the punch. The appropriate punch motions for prevention of galling of the formed hole for extrusion ratios in the range 1.07–1.80 were determined in the proposed forming method using a servo press. Furthermore, the proposed method was found to produce the formed holes with high shape accuracy. The shape accuracy of the formed hole is discussed with experimental and finite element simulation results in terms of lubrication state and temperature change.     

Experimental and numerical analysis of friction in high aspect ratio combined forward-backward extrusion with retreat and advance pulse ram motion on a servo press

A method for maintaining lubrication in the backward extrusion of deep holes for lightweight structural components is proposed utilizing a servo press and a punch with an internal channel for liquid lubricant supply. In this forming method, the punch is pushed into the specimen with a servo press in a manner that combines pulsed and stepwise modes. Sufficient liquid lubricant is periodically supplied to the deformation zone through the internal channel upon the retreat of the punch. This forming method with pulse punch ram motion was tested in combined forward-backward extrusion process with a high aspect ratio (height/diameter) in this study. The material flow of the aluminum specimen during the extrusion with pulse punch ram motion was investigated to determine the coefficient of shear friction at the specimen–punch interface. The punch wear was assessed by a finite element analysis of the material flow of the specimen during the extrusion with pulse punch ram motion.     

Theory and application of a combined feedback–feedforward control and disturbance observer in linear motor drive wire-EDM machines

This paper presents a combined two-degree-of-freedom controller and disturbance observer design for a direct drive motion control system actuated by permanent-magnet linear synchronous motors (PMLSM). A feedback controller based on pole-placement design method is proposed to achieve desired tracking performance as well as stabilize the closed-loop system. A newly designed feedforward controller is proposed to reduce tracking errors based on an inverse model of the direct drive system. A digital disturbance observer is implemented to be included in the proposed feedback–feedforward control structure to compensate for nonlinear friction, cogging effects, and external load disturbance. Furthermore, the proposed control scheme has been verified as being internally stable. Experimental results indicate that the proposed controller can achieve a high contouring accuracy of ±0.3 μm as well as provide disturbance rejection and robustness. The maximum contour error of circular trajectory was reduced from 8.5 to 3.2 μm in comparison with proportional-integral-derivative (PID) controller.     

Prevention of galling in forming of deep hole with retreat and advance pulse ram motion on servo press

To prevent galling in backward extrusion of deep holes, an extrusion method utilizing a servo press and a punch having an internal channel for supplying liquid lubricant is proposed. On the servo press, the punch is pushed into the billet in a manner combining pulsed and stepwise modes. The lubricant is sucked into the formed hole through the internal channel during the retreat motion of the punch. Appropriate punch ram motions for preventing galling are determined from the surface observation of the formed hole. The maximum aspect ratio of the hole attained by the proposed method is discussed.     

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。     

80MN锻造液压机液压控制系统的研制

研制了具有等温锻功能的80 MN锻造液压机液压控制系统.针对能量损耗低和控制精度高的要求,采用了西门子S7-400 PLC与Trio控制器相结合的控制方案,PLC实现液压泵的控制、电液伺服阀的切换、工作台控制、加热与冷却系统控制、润滑系统控制及安全监测;Trio完成速度控制与平度控制的任务,获得了预期的控制结果.     

24MN玻璃钢制品液压机控制系统的研制

24MN玻璃钢制品液压机有其特殊的工艺要求,需要对液压机的压力、速度和平度进行控制.为此设计了液压系统的结构,采用八缸框架式结构,并提出PLC与Trio控制器相结合的控制方案.PLC主要负责系统运行、维护与模式切换.Trio控制器依靠设计的控制算法,调节比例伺服阀,以控制压力、速度和平度.通过调试,系统运行良好并实现了要求的控制目标.     

无速度传感器的滑模变结构直接转矩控制系统研究

本文针对无速度传感器直接转矩控制的交流伺服系统,运用滑模变结构控制理论,设计了一种滑模变结构控制器,并对常规滑模控制器存在的抖动问题提出一种改善方法,即在滑模控制器后加一个模糊比例积分环节。仿真实验证明了该控制器设计方法的有效性。     

基于改进迭代学习的并联6-DOF运动平台控制策略研究

为了改善并联6-DOF运动平台的轨迹跟踪效果提出了一种新颖的控制算法。该控制方法结合了非奇异Terminal滑模控制(NTMSMC)和迭代学习控制(ILC),非奇异Terminal滑模控制器可以在有限的时间到达和消除控制器奇异,将其作为第一控制器来处理模型参数不确定性、未知的非线性和外部干扰;在到达滑模面之后,用PD型迭代学习控制器作为第二控制器来消除周期性轨迹跟踪误差。Simulink仿真结果表明,这种组合控制器与其它控制器(如PID控制、滑模控制、迭代学习控制)相比有更高的轨迹跟踪精度和较强的鲁棒性。     

电液比例系统位置伺服迭代学习控制

针对电液比例控制系统存在的时变性、非线性、强耦合以及液压参数摄动等问题,提出一种带补偿的迭代学习控制（ILC）算法。在分析电液比例位置伺服系统机制的基础上,建立系统的数学模型。设计不严格依赖于系统精确模型的迭代学习算法,以非常简单的方式处理不确定度相当高的非线性强耦合动态系统。为解决误差收敛过程中存在的抖动和尖峰毛刺,在算法中加入输入和误差补偿。利用先前控制输入和误差的变化量,对系统进行补偿。仿真和实验结果表明：迭代学习控制算法能够有效实现系统对期望轨迹的精确跟踪;与传统PID控制相比,迭代学习控制提高了系统的控制精度和快速跟踪能力。     

基于WinCE7和WiFi的数控转塔冲床数控系统无线通信的实现

通过分析基于PC的传统开放式数控系统的缺陷,提出一种基于高实时性、多任务的嵌入式操作系统WinCE7和CORTEXA8微处理器的数控转塔冲床数控系统,WinCE7操作系统是一个紧凑高效的模块化操作系统,配合CORTEXA8微处理器能满足数控转塔冲床对实时控制的要求。分析了计算机与数控机床之间通信方式的发展趋势和对机床加工高效化、自动化的影响,提出基于WiFi的数控转塔冲床无线通信解决方案。实验结果表明:WiFi模块工作正常,能实现上位机与嵌入式控制器之间的数据收发,降低了成本,提高了效率。     

22000kN大型伺服压力机电控系统研究与实现

介绍了基于发那科伺服系统的大型伺服压力机机械结构及特点,并简单介绍了压力机多连杆的传动方式;结合伺服压力机的电气控制方式及特点,对发那科控制系统进行了阐述。将自主研发的上下位机系统与发那科动力系统相结合,实现整个伺服压力机自动化系统,并给出了其优异的性能指标。证明了此方案适合用于伺服压力机控制系统。     

不锈钢水槽拉伸压力机液压及控制系统设计

针对传统不锈钢水槽拉伸压力机存在的诸多问题,根据水槽的生产工艺过程,设计基于德国博世力士乐公司生产的XM21型运动控制器和4WRPEH型高频响比例阀的比例伺服液压控制系统。改造后的压力机具有控制精度高、响应速度快、运行平稳可靠等特点,实现了水槽生产自动化。运行结果表明：该系统模具更换方便快捷,大幅缩短了设备调试时间,生产效率明显提升,产品质量和稳定性大大提高,给企业带来了显著的经济效益。     

分数阶控制器在压力机位置伺服控制系统中的应用研究

针对压力机位置伺服控制系统的大惯量、强非线性等问题,提出一种基于分数阶微积分的分数阶PIλDμ矿控制策略,给出了分数阶控制器的数字实现方式.分数阶控制器的分数阶微积分可以增加传统PID控制器的设计灵活性和系统的稳定性.为验证分数阶控制器的控制效果,在Matlab/Simulink下建立了压力机位置伺服系统模型.仿真结果表明:分数阶控制器的控制效果优于传统的整数阶控制器.     

Springback behaviour in bending of ultra-high-strength steel sheets using CNC servo press

The springback behaviour of ultra-high-strength steel sheets in bending was investigated under controlled conditions using a CNC servo press. Although the ultra-high-strength steel sheets are attractive in reducing weight of cars, the amount of springback of the ultra-high-strength steel sheets in the forming is very large due to high strength. The CNC servo press has the function of accurately controlling the motion by two servo motors. The effects of the material, the finishing reduction in thickness, the forming speed and the holding time at the bottom dead centre on the amount of springback in V-shaped bending were examined. The scatter of the springback for the ultra-high-strength steel sheets was improved by using real thickness and not nominal thickness of each individual sheet in the control of the punch stroke. The amount of springback for the ultra-high-strength steel sheet in the V-shaped bending was much larger than that for the mild steel sheet, and the amount was decreased by the finishing reduction in thickness direction because of uniform stress distribution. The effects of the forming speed and the holding time at the bottom dead centre were small. The amount of springback for the steel sheets was almost proportional to the ratio of the tensile strength to the elastic modulus.     

Performance robustness and stiffness analysis on a machine tool servo design

The machine tool servo design is very different from the traditional high performance servo systems. Traditional servo design depends heavily on a precise system model so that frequency domain or time domain compensation techniques can be applied, and many synthesis tools such as LQG, H_∞, or LMI, … are available based on this concept. While these synthesis tools are becoming very useful in many situations, they are not used in the machine tool servo design. Most high performance machine tool systems still rely on the more primitive PID or PDF controllers in conjunction with complicated friction and temperature compensation algorithms. This paper investigates the different approaches based on a house-designed servo control board. With the ability to change the servo control algorithms on a test machine tool, the performance robustness and servo stiffness were tested both numerically and experimentally. The numerical tests conducted with PID, PDF, and LQG controllers showed that the PID controller is the easiest to achieve good performance, but the PDF controller contains the best performance robust margin. Experimental results also indicated that the PDF controller exhibits far superior robustness properties over the other two controllers.     

西门子840Dsl数控系统在全电伺服转塔冲床上的应用

本文介绍利用西门子840Dsl数控系统的冲压模块功能,实现对伺服转塔冲床的控制,冲压速度快、精度高、性能稳定,进一步提高了设备的自动化程度.     

基于预测控制器的电液伺服系统节能方法研究

设计基于预测控制器的电液伺服系统节能方法,以控制电液伺服系统准确追踪期望位置的同时,达到节能的效果。从电液伺服系统的原理出发,分析电液伺服系统的工作原理及结构组成。利用比例方向控制阀阀芯位移,计算出液压缸腔室与油箱压力及供给压力间的压差值。利用活塞位移求取腔室内的压力连续性方程。在考虑比例方向控制阀阻尼系数的基础上,建立其对应的运动方程。利用比例溢流阀的开度,求取其动态方程。通过腔室压力值、比例溢流阀的开度,建立电液伺服系统的状态模型。以期望位置为依据,计算出腔室内压力的期望值,进而求取所需供给压力。利用所需供给压力,构造预测控制器,对电机的转速进行预测控制,以达到动态调节供给压力的效果,实现节能控制。实验结果表明：与采用滑模控制的恒压方法相比,该方法对正弦及随机期望位置的追踪精度分别提高了44.93%和39.98%,对应的能耗分别降低了13.45%和10.54%。 该方法对电液伺服系统的位置控制效果及节能控制效果都较好