Numerical Simulation of Residual Stress in Injection Molding

1 Introduction Injection molding is a flexible production technique for the manufacturing of polymer product. A typical injection molding process consists of four stages: filling, packing, cooling and ejection of product. During these processes, residual stress is produced due to high pressure and cooling, which induce the warpage and shrinkage of product. To make the product with high precision, it is important to simulate the pressure and thermal effect induced residual stress in the process…     

Mathematical modelling of ball and plate system with experimental and correlation function-basedmodel validation

The ball and plate system is an inherently nonlinear under actuated benchmark system used for validating the performance of various control schemes. A mathematical model depicting the dynamics close to that of the system is very much required for such a test bed. In this correspondence, the complete nonlinear model, a simplified nonlinear model, and a linearized model of the ball and plate system are developed. The system comprises a ball and plate mechanism and a rotary servo unit. The ball and plate mechanism is modelled using the Euler–Lagrange method, whereas the rotary servo subsystem is modelled from the first principles. The nonlinear model of the combined system is developed by including the dynamics of the servo motor with gear and rolling resistance between the ball and the plate. The simplified nonlinear model of the system is obtained with suitable assumptions. The model is linearized around the operating point using the Jacobian. The validity of the developed models is investigated through correlation function analysis. The open-loop response of the three models, viz., nonlinear, simplified nonlinear, and linearized models, is analyzed in the MATLAB/Simulink platform. Since the open-loop system is unstable, the experimental validation of the model is performed with a double-loop PSO (particle swarm optimization) PID control scheme.     

Introduction to the benchmark challenge on common rail pressure control of gasoline direct injection engines

As one of the most important actuators for gasoline direct injection technology, common rail systems provide the requested rail pressure for fuel injection. Special system characteristics, such as coupled discrete-continuous dynamic in the common rail system, limited measurable states, and time-varying engine operating conditions, impel the combination of advanced methods to obtain the desired injection pressure. Therefore, reducing the pressure fluctuation and satisfying engineering implementation have become noteworthy issues for rail pressure control (RPC) systems. In this study, the benchmark problem and the design specification of RPC proposed by 2018 IFAC E-CoSM Committee are introduced. Moreover, a common rail system model is provided to the challengers, and a traditional PI control is applied to show the problem behaviors. Finally, intermediate results of the challengers are summarized briefly.     

Modeling and Control of Hybrid Machine Systems – a Five-bar Mechanism Case

A hybrid machine (HM) as a typical mechatronic device, is a useful tool to generate smooth motion, and combines the motions of a large constant speed motor with a small servo motor by means of a mechnical linkage mechanism, in order to provide a powerful programmable drive system. To achieve design objectives, a control system is required. To design a better control system and analyze the performance of an HM, a dynamic model is necessary. This paper first develops a dynamic model of an HM with a five-bar mechanism using a Lagrangian formulation. Then, several important properties which are very useful in system analysis, and control system design, are presented. Based on the developed dynamic model, two control approaches, computed torque, and combined computed torque and slide mode control, are adopted to control the HM system. Simulation results demonstrate the control performance and limitations of each control approach.     

A new adaptive backstepping method for nonlinear control of turbine main steam valve

A new approach for nonlinear adaptive control of turbine main steam valve is developed. In comparison with the existing controller based on ＂classical＂ adaptive backstepping, this method does not follow the classical certaintyequivalence principle in the design of adaptive control law. We introduce this approach, for the first time, to power systems and present a novel parameter estimator and dynamic feedback controller for a single machine infinite bus （SMIB） system with steam valve control. This system contains unknown parameters such as reactance of transmission lines. Besides preserving useful nonlinearities and the real-time estimation of uncertain parameters, the proposed approach possesses better performances with respect to the response of the system and the speed of adaptation. The simulation results demonstrate that the proposed approach is better than the design based on ＂classical＂ adaptive backstepping in terms of properties of stability and parameter estimation, and recovers the performance of the ＂full-information＂ controller. Hence, the proposed method provides an alternative for engineers in applications.     

具有传输时延的网络控制系统故障估计与调节

In this paper, a method of fault estimation and fault tolerant control for networked control system (NCS) with transfer delay and process noise is presented. First, the networked control system is modeled as a multiple-input-multiple-output (MIMO) discrete-time system with transfer delays, process noise, and model uncertainties. Under this model and under some conditions, a fault estimation method is proposed to estimate the system faults. On the basis of the information on fault estimation and the sliding mode control theory, a fault tolerant controller is designed to recover the system performance. Finally, simulation results are used to verify the efficiency of the method.     

Adaptive Kalman filter and dynamic recurrent neural networks-based control design of macro-micro manipulator

In this paper,a composite control scheme for macro-micro dual-drive positioning stage with high acceleration and high precision is proposed.The objective of control is to improve the precision by reducing the influence of system vibration and external noise.The positioning stage is composed of voice coil motor(VCM) as macro driver and piezoelectric actuator(PEA) as micro driver.The precision of the macro drive positioning stage is improved by the combined PID control with adaptive Kalman filter(AKF).AKF is used to compensate VCM vibration(as the virtual noise) and the external noise.The control scheme of the micro drive positioning stage is presented as the integrated one with PID and intelligent adaptive inverse control approach to compensate the positioning error caused by macro drive positioning stage.A dynamic recurrent neural networks(DRNN) based inverse control approach is proposed to offset the hysteresis nonlinearity of PEA.Simulations show the positioning precision of macro-micro dual-drive stage is clearly improved via the proposed control scheme.     

具有传输时延的网络控制系统故障估计与调节

In this paper,a method of fault estimation and fault tolerant control for networked control system (NCS) with transfer delay and process noise is presented.First,the networked control system is modeled as a multiple-input-multiple-output (MIMO) discrete-time system with transfer delays,process noise,and model uncertainties.Under this model and under some conditions, a fault estimation method is proposed to estimate the system faults.On the basis of the information on fault estimation and the sliding mode control theory,a fault tolerant controller is designed to recover the system performance. Finally, simulation results are used to verify the efficiency of the method.     

Robust Optimization-Based Iterative Learning Control for Nonlinear Systems With Nonrepetitive Uncertainties

This paper aims to solve the robust iterative learning control(ILC)problems for nonlinear time-varying systems in the presence of nonrepetitive uncertainties.A new optimization-based method is proposed to design and analyze adaptive ILC,for which robust convergence analysis via a contraction mapping approach is realized by leveraging properties of substochastic matrices.It is shown that robust tracking tasks can be realized for optimization-based adaptive ILC,where the boundedness of system trajectories and estimated parameters can be ensured,regardless of unknown time-varying nonlinearities and nonrepetitive uncertainties.Two simulation tests,especially implemented for an injection molding process,demonstrate the effectiveness of our robust optimization-based ILC results.     

An online estimator for rotor resistance in vector drives of induction machines based on Walsh functions

In a modern electrical driver, rotor field oriented control an appropriate transient response. In this method, the space （RFOC） method has been used to achieve a good performance and vector of the rotor flux comes handy by the rotor resistance value. The rotor resistance is one of the important parameters which varies according to motor speed and room temperature alteration. In this paper, a new on-line estimation method is utilized to obtain the rotor resistance by using Walsh functions domain. The Walsh functions are one of the most applicable functions in piecewise constant basis functions （PCBF） to solve dynamic equations. On the other hand, an integral operational matrix is used to simplify the process and speed of the computation algorithm. The simulations results show that the proposed method is capable of solving the dynamic equations in an electrical machine on a time interval which robustly estimates the rotor resistance in contrast with injection noises.     

直驱式巷道超前支架油缸控制方法

考虑到传统的阀控液压系统存在伺服阀容易因受到油液污染而无法正常工作、阀控液压系统效率低、节流损失大、造成能源浪费等问题,研究一种基于伺服电机直驱液压泵的超前支架电液控制方法.伺服电机直驱液压泵系统由于电机的启动和转向过程中存在滞后性,因此使用常规PID算法的控制效果较差,使用模糊PID算法对伺服电机直驱液压泵系统进行控制.使用Matlab/Simulink仿真软件建立本文研究的直驱泵控巷道超前支架控制系统的仿真模型,并建立超前支架的实验样机,使用常规PID与模糊PID算法进行对比研究,研究结果表明:模糊PID算法作用下,伺服电机直驱液压泵的超前支架液压缸位置变化的超调量更低,调整速度更快,能够快速跟踪给定信号曲线,具有较好的鲁棒性.     

三螺杆泵寿命试验台测控系统设计

为了测试结构参数和使用参数对三螺杆泵性能和使用寿命的影响,设计研发了全自动化寿命测试试验台。通过分析三螺杆泵常见故障,选定输出流量和泵内压力作为寿命评价指标,制定模拟工况下的多因素试验方案和寿命试验流程,确定本测试系统实现功能。本系统基于PLC控制器,采用伺服电机驱动可实现螺杆泵转速的精确调节,设置电磁阀来调节系统油压,运用外部加热器控制油温,应用iFix组态软件实现测试系统参数设置及流量传感器和压力传感器数据的实时显示及数据的存储。本试验台测控系统实现了在模拟工况下三螺杆泵性能及寿命的测试,性能稳定,测试数据精确,为三螺杆泵故障分析和寿命试验研究提供了软硬件支撑。     

Harmonic control of a dual-valve hydraulic servo system with dynamically allocated flows

Modern industries face increasing demands to improve the precision and workability of equipment, leading to stringent requirements for hydraulic servo systems in terms of flow, accuracy, and output power. High-flow servo valves and multi-valve synchronous control methods have seen more applications in the industry to meet these demands. However, high-flow servo valves are expensive and have unsatisfactory performance, and synchronous control methods require servo valves to have the same hydraulic characteristics, resulting in higher cost and lower accuracy of high-flow hydraulic servo systems. Also, very little has been conducted on controlling single actuators using multiple valves. In this study, we design a novel dual-valve hydraulic servo system structure with a high-flow proportional directional valve that is connected in parallel with a low-flow servo valve and further develop the mathematical model of this dual-valve system. Next, a harmonic control scheme was proposed, which included a flow allocation layer and trajectory tracking layer. Thereby, we achieved optimal control of two valves, and robust performance was guaranteed. Finally, we investigate the relationships between the flows of two valves, the deadband of the proportional directional valve, and trajectory tracking errors. Experimental results show that the proposed control scheme can effectively adjust the output flow of each valve dynamically according to the tracking trajectory and the hydraulic characteristics of the two valves, and the tracking performance of the servo system is significantly improved. This method is promised to enable the realization of an economical, high-flow, high-precision hydraulic servo system that can be generally used in various fields, such as marine engineering and construction.     

电液伺服控制技术在大型高炉减压阀组控制中的应用

介绍了一种在大型高炉减压阀组中得到广泛运用的电液伺服控制技术。文中从介绍电液伺服控制技术入手,对电液伺服控制系统的构成及工作原理进行了详细的分析,最后阐述了电液伺服控制系统在大型高炉减压阀组自动控制过程中的应用。     

高压软管智能化检验系统开发

为了解决高压软管检验过程中手动操作精度低、效率低的问题,通过对高压软管耐压性与气密性检验流程和控制要求的分析,采用伺服电机推动比例阀芯的方法来控制压力,即压力传感器的实测压力值与上位机设定压力值在PLC中进行比较处理,计算出偏差压力值,控制器不断修正原有的电流以完成压力的修正,从而达到自动化闭环控制压力的目的;设计了专用的上位机操作软件及数据库以录入、存储和查询高压软管检验信息,开发了一套智能化检验系统。该系统实现了集耐压性与气密性两项检验于一体、恒速率升压、圧力曲线实时显示、自动生成检验报告等功能,显著提高了检验精度与效率。     

基于模糊理论的液压马达伺服系统设计和实现

模糊控制技术和阀控液压马达位置伺服系统相结合,对提高机床工作台移动位置精确度有重要的意义,能够容易实现加工零件要求的尺寸公差。介绍了传统阀控液压马达伺服系统的实现方案,针对它建立了系统的数学模型。并分析工作台移动位置与阀控流量的规律,提出了一种基于专家经验的模糊控制方案,结合系统的数学模型进行Matlab／Simulink仿真。     

电液速度伺服系统的模糊PI控制

为了提高控制精度、改善系统的静动态特性,针对液压马达速度伺服系统的非线性时变特点,提出了电液速度伺服系统中液压马达速度的控制方法。通过模糊推理在线实时调节PID参数,使系统控制参数迭到全局优化,解决了一般PID参数只是对于桌一工作点局部优化的问题。与单纯PID控制器相比,模糊PI方法使系统动态性能和鲁棒性得到了犬幅度提高,试验结果表明了该方法对非线性系统大范围控制的有效性。     

左心辅助循环系统的模糊控制

本文描述一种微机控制的左心辅助循环装直(LVAD)。这是一个以平均主动脉压为被控量、以辅助血泵的收缩速度为控制量的闭环系统。针对系统的特点,采用了模糊控制算法,以直流无刷电机为执行元件。控制系统的性能在循环系统水力学模拟台上做了试验,取得了满意的效果。     

基于DSP控制的液压注塑机伺服控制系统

介绍了一种基于数字信号处理器TMS320F2812控制的液压注塑机伺服控制系统的控制原理、系统硬件组成和软件设计。仿真结果表明,该系统电路简单、工作可靠、动态响应性能和静态性能良好,具有较高的性价比。     

Buoyancy engine developed for underwater gliders

A buoyancy engine with a swashplate-type axial piston pump was developed. Its oil extrusion and drawing properties under high hydraulic pressure were evaluated. This buoyancy engine is now installed in an underwater glider that will achieve long-term monitoring of ocean environments up to 2100 m depth in a designated area with lower operational costs. This bidirectionally functioning pump can control the amount of oil in extrusion and draw operations. When drawing oil under high pressure, the hydraulic pump and the electric motor, respectively, act as a hydraulic motor and an electric generator. The generated electric power is absorbed by a damping resistor. The oil-drawing and extrusion properties were measured using a large hyperbaric chamber that is able to produce an almost identical environment to that of actual operations. Results confirmed stable oil extrusion operations up to 21 MPa. Regarding oil-drawing properties, although it was measured only up to 10 MPa in the hyperbaric chamber, it can be inferred that the system can draw the oil and can control the buoyancy precisely up to 21 MPa by replacing the two-way ball valve with an electromagnetic latching solenoid valve.