多因素耦合条件下数控机床进给系统负载惯量比的综合分析与设计

负载惯量比是数控机床进给系统性能分析与设计的重要内容,数控机床的高速化、高精度化发展使得负载惯量比的优化选择问题更加突出。这要求设计者能够系统地分析负载惯量比与系统性能之间的相互关系,并为之提供负载惯量比的精确有效的设计方法。采用双惯量机械系统模型,通过解析分析与数值试验相结合的方法,分析负载惯量比与能量匹配效率的关系;分析了半闭环与全闭环两种控制结构下负载惯量比与控制增益上限、闭环频率特性以及抗干扰动刚度的关系;并在此基础上给出了数控机床进给系统负载惯量比的设计步骤与方法。为数控机床的设计者提供一种在多因素作用下设计最优负载惯量比的方法,具有理论和实际的工程价值。     

平衡阀对破拆机器人液压位置闭环系统影响的研究

破拆机器人为提高定位精度其臂系常采用液压位置闭环系统，然而，在负负载情况下当负负载和闭环增益增大时系统存在明显振荡。因此，通过AMESim软件建立了平衡阀及臂系液压位置闭环系统的模型，且实验验证了模型的正确性；仿真分析了不同负负载、闭环增益、平衡阀先导压力和压力流量系数等参数对闭环系统振荡的影响规律，提出了通过平衡阀及其关键性能参数的设置来抑制系统振荡的方法。仿真结果表明了该方法的正确性，为破拆机器人定位精度的提高提供了理论参考和技术途径。     

直流电机位置伺服系统设计

以机械臂的驱动电机为研究对象,采用廉价的旋转电位器作为位置传感器,设计了基于单片机的直流电机位置闭环控制系统。首先,研究了直流电机的位置控制原理和实现方法,并提出了适用于该系统的力矩控制方式。然后,从设计指标出发,计算了电机的负载,选择了执行电机,并设计了系统的硬件电路和相应的控制程序。最后,重点对系统调试过程中出现的非线性问题进行了研究,针对机械产生的非线性问题提出了改进方案和补偿的方法,并应用到了系统实际设计中。成功实现了直流电动机在空载、负载这两种不同状态下的位置控制。     

基于成本切换的闭环供应链离散动态模型及其模糊鲁棒控制

为研究Internet环境下基于成本切换的不确定闭环供应链运作问题,建立了一类基于成本切换的闭环供应链动态模型,该模型包括基于成本的切换信号向量以及第三方逆向物流服务商回收和制造商自行回收两个子系统,该模型的逆向物流部分包括废旧产品回收再制造部分和产品无偿回收部分.针对闭环供应链系统在第三方逆向物流服务商回收和制造商自行回收两种模式切换过程中成本波动较大的问题,分析了闭环供应链切换系统的运作过程,且在运用Lyapunov-Krasovskii函数方法和并行分布补偿算法的基础上,以线性矩阵不等式形式提出和证明了闭环供应链切换系统渐近稳定的充分条件,并设计了切换律.通过一个仿真例子验证了所提方法的有效性.     

变刚度电液力负载模拟器自适应反步控制

某电液力负载模拟系统以钢丝绳为传递介质,其特性随钢丝绳刚度大范围变化而改变,针对定常控制策略难以实现其大范围控制难题,提出采用自适应反步控制策略。结合间接自适应方法和反步控制方法的优点,通过反步设计方法获得与系统模型参数直接相关的控制器,通过参数预估实时更新刚度值并修正控制器参数,从而补偿刚度变化对闭环控制系统性能的影响。仿真结果表明：在所设计的力加载范围内,该控制算法能够准确预估钢丝绳刚度值,可以实现变刚度电液力负载模拟系统大范围高精度控制,并且可以消除多余力对负载模拟精度的影响。     

多电平级联光伏逆变器稳压控制研究

研究了一种多电平级联光伏逆变器系统的稳压控制问题,提出了一种新型的双闭环PI控制方法,能够在负载扰动的情况下迅速实现稳定、可靠运行。通过搭建仿真模型,分析证明了该控制方法具有较高的控制精度及可行性。     

一种改进型负载线移相器MMIC的设计方法

在采用传统微带线负载移相器设计小相位数字移相器时,遇到了负载线宽过窄的问题,而一般半导体工艺很难实现。在此基础上,提出了一种改进型微带线负载移相器的设计方法。该移相器主传输线的两端各挂载一个相同输入阻抗的开路支节,通过调节支节的阻抗值使移相器的输入／输出反射损耗达到最小;通过加载两个开路支节,在同样的相移量下,加宽负载线的宽度,提高产品的成品率。利用此设计的移相量为11．25°,同时数字移相器的实验结果验证了该设计方法的正确性和可行性。     

一种PMLSM的速度辨识控制方法

针对永磁同步直线电机的矢量控制问题,提出了基于模型参考自适应的速度辨识方法。通过分析永磁同步直线电机的数学模型,设计了并联模型参考自适应模型,并利用Popov超稳定性定理推导了模型参考自适应律,得到了速度辨识自适应算法,实现了对电机速度和位置的辨识。将速度辨识算法嵌入永磁同步直线电机的双闭环矢量控制模型中,建立了基于模型参考自适应速度辨识的双闭环矢量控制系统。在MATLAB中对电机及其控制系统进行建模,并在负载突变和速度突变两种工况条件下对系统模型进行了仿真,仿真结果表明,该方法能实现对速度和位置的高精度估算,稳定性较好。     

一种气-液比例智能调节模拟负载系统的研制

在汽车起动机的性能测试设备研制中,负载模拟是一项关键技术。为适应某新型综合测试设备具备多功能和通用性的要求,研制了一种气—液比例控制刹车系统作为模拟负载,并为之设计了智能控制器。该控制器将PID算法与神经网络学习技术相结合,通过在线优化PID参数,提高了负载的闭环特性和自适应能力,保障了对多种型号起动机的参数检测快速、准确。该系统已在起动机生产线上实际运行,效果良好。     

基于磁粉制动器加载的液压系统压力响应特性实验

为在实验室环境下模拟真实负载工况,优化液压系统控制性能,采用磁粉制动器作为加载元件,实现了变转速的模拟压力加载控制。针对压力开环加载存在稳态误差及磁滞现象的缺点,设计并开发压力闭环。通过实验分析对比了开环加载与闭环加载的系统压力动态响应特性及相同负载工况条件下抗干扰性能,为实际工况的负载模拟提供了可靠的模拟加载技术。     

Enhanced IMC design of load disturbance rejection for integrating and unstable processes with slow dynamics

In view of the deficiencies in existing internal model control (IMC)-based methods for load disturbance rejection for integrating and unstable processes with slow dynamics, a modified IMC-based controller design is proposed to deal with step- or ramp-type load disturbance that is often encountered in engineering practices. By classifying the ways through which such load disturbance enters into the process, analytical controller formulae are correspondingly developed, based on a two-degree-of-freedom (2DOF) control structure that allows for separate optimization of load disturbance rejection from setpoint tracking. An obvious merit is that there is only a single adjustable parameter in the proposed controller, which in essence corresponds to the time constant of the closed-loop transfer function for load disturbance rejection, and can be monotonically tuned to meet a good trade-off between disturbance rejection performance and closed-loop robust stability. At the same time, robust tuning constraints are given to accommodate process uncertainties in practice. Illustrative examples from the recent literature are used to show effectiveness and merits of the proposed method for different cases of load disturbance.     

Discrete-time domain two-degree-of-freedom control design for integrating and unstable processes with time delay

A discrete-time domain two-degree-of-freedom (2DOF) design method is proposed for integrating and unstable processes with time delay. Based on a 2DOF control structure recently developed, a controller is analytically designed in terms of the H₂ optimal control performance specification for the set-point tracking, and another controller is derived by proposing the desired closed-loop transfer function for load disturbance rejection. Both controllers can be tuned relatively independent to realize control optimization. Analytical expression of the set-point response is given for quantitatively tuning the single adjustable parameter in the set-point tracking controller. At the meantime, sufficient and necessary conditions for holding robust stability of the closed-loop control system are established for tuning another adjustable parameter in the disturbance rejection controller, along with numerical tuning guidelines. Illustrative examples from the literature are used to demonstrate the effectiveness of the proposed method.     

IMC-PID design based on model matching approach and closed-loop shaping

Motivated by the limitations of the conventional internal model control (IMC), this communication addresses the design of IMC-based PID in terms of the robust performance of the control system. The IMC controller form is obtained by solving an H-infinity problem based on the model matching approach, and the parameters are determined by closed-loop shaping. The shaping of the closed-loop transfer function is considered both for the set-point tracking and for the load disturbance rejection. The design procedure is formulated as a multi-objective optimization problem which is solved by a specific optimization algorithm. A nice feature of this design method is that it permits a clear tradeoff between robustness and performance. Simulation examples show that the proposed method is effective and has a wide applicability.     

Generalized predictor based active disturbance rejection control for non-minimum phase systems

In this paper, a generalized predictor based control scheme is proposed to improve system performance of set-point tracking and disturbance rejection for non-minimum phase (NMP) systems. By using a generalized predictor to estimate the system output without time delay, a model-based extended state observer (MESO) is designed to simultaneously estimate the system state and disturbance. Accordingly, an active disturbance rejection control design is developed which consists of a state feedback control and a feedforward control for the disturbance rejection. The MESO and feedback controllers are analytically derived by specifying the desired characteristic roots of MESO and closed-loop system poles, respectively. To improve the output tracking performance, a pre-filter is designed based on a desired closed-loop transfer function for the set-point tracking. A sufficient condition guaranteeing robust stability of the closed-loop system against time-varying uncertainties is established in terms of linear matrix inequalities (LMIs). Three illustrative examples from the literature are used to demonstrate the effectiveness and merit of the proposed control scheme.     

Nonlinear robust dual-loop control for electro-hydraulic load simulator

This paper investigates on the high performance torque control of electro-hydraulic load simulator (EHLS). In order to suppress actuator׳s motion disturbance, a nonlinear robust dual-loop control scheme is developed, which consists of a open-loop nonlinear velocity feed-forward compensator and a closed-loop nonlinear deterministic robust torque controller. The main function of the open-loop compensator is to decouple actuator׳s active motion disturbance, whereas the torque loop controller aims at guaranteeing the dynamics performance of tracking torque reference. Besides actuator׳s motion disturbance, both the nonlinearity characteristics and friction problem of the EHLS system are taken into consideration in this paper. The effectiveness of the developed method are verified through comparative co-simulations and experiments.     

A new fractional-order sliding mode controller via a nonlinear disturbance observer for a class of dynamical systems with mismatched disturbances

This paper investigates the stabilization and disturbance rejection for a class of fractional-order nonlinear dynamical systems with mismatched disturbances. To fulfill this purpose a new fractional-order sliding mode control (FOSMC) based on a nonlinear disturbance observer is proposed. In order to design the suitable fractional-order sliding mode controller, a proper switching surface is introduced. Afterward, by using the sliding mode theory and Lyapunov stability theory, a robust fractional-order control law via a nonlinear disturbance observer is proposed to assure the existence of the sliding motion in finite time. The proposed fractional-order sliding mode controller exposes better control performance, ensures fast and robust stability of the closed-loop system, eliminates the disturbances and diminishes the chattering problem. Finally, the effectiveness of the proposed fractional-order controller is depicted via numerical simulation results of practical example and is compared with some other controllers.     

基于微分平坦的旋转倒立摆双闭环抗扰 PID 控制

针对一类不稳定、欠驱动二自由度旋转倒立摆系统, 提出一种基于微分平坦的双闭环抗扰 PID 控制方法。 首先, 建立倒 立摆的非线性动力学模型, 利用近似线性化分析系统的不稳定零动态与非最小相位特性; 然后, 结合微分平坦理论, 设计倒立摆 平坦输出,重构系统平坦状态, 并建立平坦状态与角度输出之间的转化关系,克服倒立摆的非最小相位影响; 进一步, 针对微分 平坦系统, 设计抗扰 PID 双闭环控制结构和带宽化调节方法, 在主动抗扰机制下实现对摆杆角度与悬臂角度的精准控制; 最后, 通过仿真与实验, 验证所提方法的有效性和实用性。 所提方法为欠驱动系统提供了一种结构简单、抗扰能力强的控制方案。     

Adaptive robust control of a class of non-affine variable-speed variable-pitch wind turbines with unmodeled dynamics

In this paper, a novel synthesis of Nussbaum-type functions, and an adaptive radial-basis function neural network is proposed to design controllers for variable-speed, variable-pitch wind turbines. Dynamic equations of the wind turbine are highly nonlinear, uncertain, and affected by unknown disturbance sources. Furthermore, the dynamic equations are non-affine with respect to the pitch angle, which is a control input. To address these problems, a Nussbaum-type function, along with a dynamic control law are adopted to resolve the non-affine nature of the equations. Moreover, an adaptive radial-basis function neural network is designed to approximate non-parametric uncertainties. Further, the closed-loop system is made robust to unknown disturbance sources, where no prior knowledge of disturbance bound is assumed in advance. Finally, the Lyapunov stability analysis is conducted to show the stability of the entire closed-loop system. In order to verify analytical results, a simulation is presented and the results are compared to both a PI and an existing adaptive controllers.     

Extended observer based on adaptive second order sliding mode control for a fixed wing UAV

This paper addresses the design of attitude and airspeed controllers for a fixed wing unmanned aerial vehicle. An adaptive second order sliding mode control is proposed for improving performance under different operating conditions and is robust in presence of external disturbances. Moreover, this control does not require the knowledge of disturbance bounds and avoids overestimation of the control gains. Furthermore, in order to implement this controller, an extended observer is designed to estimate unmeasurable states as well as external disturbances. Additionally, sufficient conditions are given to guarantee the closed-loop stability of the observer based control. Finally, using a full 6 degree of freedom model, simulation results are obtained where the performance of the proposed method is compared against active disturbance rejection based on sliding mode control.     

A robust disturbance reduction scheme for linear small delay systems with disturbances of unknown frequencies

A robust disturbance reduction scheme for linear small delay systems with disturbances of unknown frequencies is presented in this paper. Unlike other methods, the proposed scheme does not require disturbance frequencies to be known. The linear systems modeled in this study are nominally stable and minimum phase systems with relative degree. The control structure is an integration of Astrom's modified Smith predictor and the proposed scheme. The proposed scheme consists of an input disturbance reduction controller (IDRC) and a residual disturbance reduction controller (RDRC). The IDRC using an artificial neural network (ANN) is proposed to reduce unknown load disturbances and modeling uncertainties in stable systems and unstable systems. The ANN can appropriately approximate the product of an inverse time delay and a nonnegative gain in the IDRC. The residual signals including residual disturbances and residual uncertainties are suppressed by the RDRC based on a disturbance observer. Simulation examples are illustrated to show the effectiveness of the proposed robust disturbance reduction scheme for linear delay uncertain systems with periodic or non-periodic unknown load disturbances.