An improved auto-tuning scheme for PI controllers

Ziegler-Nichols tuned PI and PID controllers are usually found to provide poor performances for high-order and nonlinear systems. In this study, an improved auto-tuning scheme is presented for Ziegler-Nichols tuned PI controllers (ZNPICs). With a view to improving the transient response, the proportional and integral gains of the proposed controller are continuously modified based on the current process trend. The proposed controller is tested for a number of high-order linear and nonlinear dead-time processes under both set-point change and load disturbance. It exhibits significantly improved performance compared to ZNPIC, and Refined Ziegler-Nichols tuned PI controller (RZNPIC). Robustness of the proposed scheme is established by varying the controller parameters as well as the dead-time of the process under control.     

Fuzzy Self-tuning PID Controller for Speedtronic Governor Controlled Heavy Duty Gas Turbine Power Plants

Heavy duty gas turbine power plants may cause severe instability in grid connected operation under load fluctuations. To overcome such instability problems, an attempt has been made to develop proportional-integral-derivative controller for all the heavy duty gas turbine models with Speedtronic governor. Proportional-integral-derivative gains are tuned by Ziegler-Nichols and performance index methods and the step responses are obtained by using MATLAB/Simulink considering various droop settings. Simulation results of all the models reveal that the integral of squared error tuned proportional-integral-derivative controller provide better response. In order to improve the stability further, fuzzy self-tuning proportional-integral-derivative controller has been proposed in this article for all the heavy duty gas turbine models. On analyzing the simulation results, the proposed fuzzy self-tuning proportional-integral-derivative controller is found to be adaptive for all the heavy duty gas turbine models irrespective of the droop settings and yield better transient and steady state responses than Ziegler Nichols and Performance index methods.     

混合有源电力滤波器的新型电流迭代学习控制

混合有源电力滤波器可以动态抑制电网谐波电流和补偿容性无功功率,改善电网电能质量。针对传统PI型迭代学习控制算法在并联有源电力滤波器应用中的不足,算法收敛性严重依赖于学习控制的初始输入,迭代学习控制器的参数是定常值,会影响有源滤波系统的控制性能。本文提出一种新型PI迭代学习控制算法,将其应用于混合有源电力滤波器系统的电流反馈控制中,得到了应用迭代算法的收敛性条件,并采用一种改进的Ziegler-Nichols方法对控制器参数进行了优化,以提高系统的控制精度。为了提高系统的动态响应性能,提出一种谐波电流误差的反馈-前馈控制策略,其中电流误差信号的D型前馈控制环节用于实现滤波器系统的电流快速补偿,同时利用一个三层BP神经网络对前馈控制增益进行优化。仿真和实验结果证明了该迭代算法及控制策略的可行性与有效性。     

交流伺服系统的Ziegler-Nichols PI控制

针对永磁伺服系统速度调节器性能较差的问题,提出Ziegler-Nichols PI控制方法.介绍了控制器结构组成及从理论上分析了Ziegler-Nichols PI调节原理;通过大量的仿真实验,详细研究控制器参数对系统性能的影响,得到有关参数选取及控制器设计规律.结果表明,该方法具有较强的鲁棒性及自调节能力.     

食品包装高精度计量控制方法

目的 为提高食品包装过程计量组件的称量精度和效率,采用智能控制算法设计一种高精度计量控制系统.方法 在分析动态称量系统工作原理的基础上,建立称量过程数学模型,将控制对象由放料阀门开度转换为电机轴位置.考虑到传统PID控制的缺陷,结合PI Ziegler-Nichols和预测控制设计一种高精度计量控制系统.该控制系统可实现比例和积分系数的在线调整,能够抑制参数变化、负载扰动;预测控制可提高系统收敛速度和跟踪能力.最后进行仿真和实验研究.结果 仿真结果表明,智能控制算法具有比较强的自适应、自整定能力,计量精度可以达到静态称量水平,均高于99.5％.结论 食品包装高精度计量控制系统具有精度高、稳定性好、称量效率高等特点,在实际应用中对称量过程的控制效果相对较好.     

Performance improvement of PI controllers through dynamic set-point weighting

Responses of high-order systems under Ziegler-Nichols tuned PI controllers (ZNPIs) are characterized by excessive oscillation with a large overshoot. Although, a fixed set-point weighting based PI controller (FSWPI) may decrease the overshoot considerably, it fails to reduce the oscillation in the set-point response. Moreover, both FSWPI and ZNPI exhibit equally poor load regulation. Keeping in mind an overall improved performance, we propose an online dynamic set-point weighting technique for ZNPIs. The dynamic set-point weighting factor (β_d) is heuristically derived from the instantaneous process trend. Performance of the proposed dynamic set-point weighting based PI controller (DSWPI) for various second- and third-order processes including a pH process shows a significant improvement during both the set-point and load disturbance responses over other methods. Stability and robustness of the proposed DSWPI are addressed. Effectiveness of the DSWPI is demonstrated through the real-time implementation on a practical DC position control system.     

无人机俯仰角增益调参控制律设计

针对传统增益调参控制系统设计过程中离线工作量大的问题,研究设计了无人机俯仰角增益调参控制系统。首先对无人机模型进行线性化和简化处理,得到俯仰角系统模型;其次针对不同特征点处的子模型,利用根轨迹法设计得到阻尼器,利用Ziegler-Nichols以及Signal Constraint方法整定得到PID参数,得到增益调度表;然后利用sftool工具箱生成全局控制器;最后对得到的无人机俯仰角控制系统进行仿真。仿真结果表明,所设计的无人机俯仰角控制系统在全局范围内具有良好的动态响应性能。     

专家自适应PID控制在布输送张力调节中的应用

对纺织工业中布输送张力调节结构的调节原理进行了分析。对张力调节结果工作状态分段线性化，对每个线性化区间由Ziegler-Nichols规则预先整定相应一组PID控制器参数，通过专家在线判断张力调节机构的工作区间，采用相应PID控制器参数，实现布输送张力的自适应调节。在实际生产过程中，现场控制效果表明这种控制方法有效、可行。     

一种模糊PID控制在热工对象中的应用

本文研究一种新型模糊PD控制器在一般热工对象中的应用问题。由于热工对象存在参数时变的问题，因此本文采用仿真方法针对对象参数时变的情况进行了控制器的鲁棒性分析。针对多变量输入，模糊控制规则多而控制器不易实现这一问题，本文提供了一种结构简单、性能优良的一维模糊控制器与PD控制相结合的控制策略。这种控制结构很好的解决了模糊控制不跟踪输入的问题。     

SET POINT WEIGHTED PI/PID CONTROLLERS

A systematic method is given for selection of the set point weighting parameter (b) in the PI/PID controller for stable first order plus time delay systems. The parameter b is selected to minimize the over shoot for a servo problem. The responses of the PID controllers, designed by Ziegler-Nichols method or by pole placement method, without and with the set point weighting are compared. The present method significantly reduces the overshoot.