Nonlinear Decoupling PID Control Using Neural Networks and Multiple Models

For a class of complex industrial processes with strong nonlinearity, serious coupling and uncertainty, a nonlinear decoupling proportional-integral-differential （PID） controller is proposed, which consists of a traditional PID controller, a decoupling compensator and a feedforward compensator for the unmodeled dynamics. The parameters of such controller is selected based on the generalized minimum variance control law. The unmodeled dynamics is estimated and compensated by neural networks, a switching mechanism is introduced to improve tracking performance, then a nonlinear decoupling PID control algorithm is proposed. All signals in such switching system are globally bounded and the tracking error is convergent. Simulations show effectiveness of the algorithm.     

Nonlinear Decoupling PID Control Using Neural Networks and Multiple Models

For a class of complex industrial processes with strong nonlinearity, serious coupling and uncertainty, a nonlinear decoupling proportional-integral-differential (PID) controller is proposed, which consists of a traditional PID controller, a decoupling compensator and a feedforward compensator for the unmodeled dynamics. The parameters of such controller is selected based on the generalized minimum variance control law. The unmodeled dynamics is estimated and compensated by neural networks, a switching mechanism is introduced to improve tracking performance, then a nonlinear decoupling PID control algorithm is proposed. All signals in such switching system are globally bounded and the tracking error is convergent. Simulations show effectiveness of the algorithm.     

基于自适应模糊PID控制器的非线性系统仿真

对于缺乏精确模型的过程或参数时变的滞后过程,传统PID控制难以达到良好的控制效果.普通模糊控制能够对一些非线性系统进行控制,并不需被控对象精确的数学模型,但是模糊控制难以消除系统的静态误差.针对复杂的非线性系统,设计了自适应模糊PID控制器.该控制器将模糊控制的动态性能好的优点和PID控制的稳态精度高的优点结合起来,采用模糊控制与PID控制分段控制策略,当偏差大于某一阈值时,采用模糊推理的方法调整系统的控制量,当偏差小于某一阈值时,切换到PID控制以消除系统的静态误差,较好地克服了传统PID控制和普通模糊控制所存在的主要问题.通过仿真实验分析,证明了该控制方法的有效性.     

一种新型非线性PID控制器

将非线性函数与简单的PID控制器相级联，构成一种新型的非线性PID控制器，以提高现有PID控制器的性能，新型PID控制器的设计过程十分简单，只要适当构造非线性函数，并与原PID控制器级联起来便可实现，数值仿真结果表明，所提出的PID控制器比简单的PID控制器具有更好的动静态性能。     

大射电望远镜精调Stewart平台非线性PID控制

为了实现大射电望远镜馈源指向跟踪系统精调Stewart平台的高精度轨迹跟踪,针对Stewart平台的系统特点,基于机器人关节控制策略,设计了一种非线性PID的Stewart关节调节器。该非线性PID算法构造了增益参数关于误差信号的非线性拟合函数,算法能够同时保证响应速度快、超调量小以及自适应能力强的系统特性。通过建立平台的数学模型,进行了典型信号输出响应数值仿真。仿真结果验证了关节空间控制策略以及非线性PID控制方法的可行性和有效性。     

Nonlinear asymptotic attitude tracking control of an underactuated 3-degree-of-freedom helicopter using neural network feedforward term

This paper proposes a new asymptotic attitude tracking controller for an underactuated 3-degree-of-freedom (DOF) laboratory helicopter system by using a nonlinear robust feedback and a neural network (NN) feedforward term. The nonlinear robust control law is developed through a modified inner-outer loop approach. The application of the NN-based feedforward is to compensate for the system uncertainties. The proposed control design strategy requires very limited knowledge of the system dynamic model, and achieves good robustness with respect to system parametric uncertainties. A Lyapunov-based stability analysis shows that the proposed algorithms can ensure asymptotic tracking of the helicopter’s elevation and travel motion, while keeping the stability of the closed-loop system. Real-time experiment results demonstrate that the controller has achieved good tracking performance.     

基于非线性PID的调距桨控制系统仿真研究

船舶调距桨控制系统中采用一般PID控制器往往难以达到最佳控制效果。针对调距桨控制系统过程模型的特点，设计了相应的非线性PID控制器，该非线性PID控制器各增益参数与偏差信号之间呈现非线性关系，调节控制器的各参数可根据对相应参数的非线性函数进行调整来实现，并采用遗传算法来优化此控制器各部分参数。仿真结果表明，该控制器能根据实际情况快速地调整和完善PID参数，具有响应速度快，稳态精度高等优点，控制效果优于传统的PID控制器。     

A unified design for feedback-feedforward control system to improve regulatory control performance

The PID controller is widely used in industries because of its simplicity and robustness. A simple approach to improve regulatory control performance is to combine both feedback PID and feedforward controllers. The feedforward controller enables early compensation of a measured disturbance before it can seriously affect the process. The conventionally derived non-ideal feedforward controllers are not often used in practice. The reason is that an ideal feedforward controller based on direct inversion of process model is often not physically realizable. Several non-ideal feedforward control designs have been proposed where some of them involve rather intensive tuning procedure to obtain good disturbance rejection. In this paper, we present a new systematic method for designing a combined feedback-feedforward control system. The proposed design method is easy to use and applicable to stable, unstable and integrating deadtime processes where the ideal feedforward controller is physically not realizable.     

电熔镁砂熔炼过程带输出补偿的PID控制

电熔镁砂熔炼过程是以三相电机转动方向与频率为输入,以三相电极电流为输出的强非线性工业过程,其模型参数埋弧电阻率、熔池电阻率和熔池高度随熔炼过程和原矿颗粒长度及杂质成分的变化而变化.本文采用线性模型和未知高阶非线性项来描述电熔镁砂熔炼过程,其中未知高阶非线性项用已知的前一时刻高阶非线性项和其变化率来描述,采用线性模型设计PID控制器,并设计消除前一时刻高阶非线性项的补偿器和消除其变化率的补偿器,提出了带输出补偿的PID控制器,同时采用一步最优前馈控制律和一步最优调节律设计控制器参数.通过仿真实验和电熔镁炉的工业应用,表明当该过程的动态特性发生未知随机变化时,本文所提方法在所有运行时间内可以将电流跟踪误差控制在目标值范围内.     

柴油机自适应遗传非线性PID调速控制仿真

研究船用柴油机控制优化问题,柴油机调速要求快、稳、准。针对船用柴油机调速系统的时变、非线性及外界干扰等特点,传统PID调速稳定时间长,控制效果不佳。为提高喷油量达到控制准确度,改善调速系统性能,提出了一种柴油机自适应遗传非线性PID调速控制策略。采用Matlab对柴油机调速系统模型进行辨识并验证其准确性。利用非线性PID控制实现各参数增益的实时调整,提高了抗干扰能力,通过自适应遗传算法对系统的动态偏差进行监控,优化非线性PID控制器参数,减少了超调量,提高控制精度。仿真结果表明,采用自适应遗传非线性PID控制器稳定时间更短,鲁棒性强,控制精度更高,优化了柴油机调速系统性能。     

水下自航器航迹控制系统仿真研究

该文提出了一种带优化修正函数的非线性ＰＩＤ控制器设计方法,用它设计 控制器能对复杂非线性对象进行简单而有效的控制。用它为某型自抗器设计的航迹控制器在不同入水条件下进行了仿真研究。仿真结果表明,用带优化修正函数的非线性ＰＩＤ控制器设计方法设计的自航器航迹控制系统,在不同入水条件下都具有良好的动、静态特性。说明非线性ＰＩＤ控制方案较好地解决了空投入水自航器的航迹控制问题。     

基于粒子群算法的自动着陆非线性PID控制器

针对线性PID控制器在自动着陆控制中难以达到满意的控制效果的缺点,在分析各增益参数与偏差信号之间非线性关系的基础上,设计了一种P/I/D各部分参数根据控制与误差之间的调节规律连续变化的非线性PID控制器。为了选择合适的非线性PID控制器的权系数,利用粒子群算法对其各参数进行寻优整定。针对某型飞机自动着陆系统,给出了设计的一般步骤。仿真结果表明,与线性PID控制器相比,设计的非线性PID控制器能更准确地跟踪期望轨迹并满足着陆指标的要求,并具有良好的动态品质。     

Non-linear generalized minimum variance feedback, feedforward and tracking control

A generalized minimum variance control law is derived for the control of nonlinear, possibly time-varying, multi-variable systems. The solution for the tracking and feedback/feedforward control law was obtained in the time-domain using a nonlinear operator representation of the process. The cost index involves both error and control signal costing terms and is normally quadratic but may also involve nonlinear functions. The feedback controller obtained is simple to implement and includes an internal model of the process. The tracking controller can include future reference change information, providing a predictive control capability. In one form the compensator might be considered a nonlinear version of the Smith Predictor that has feedforward action.     

基于IMC原理的电子节气门控制策略

发动机系统中的电子节气门是一种典型的非线性控制对象,特别是节气门运动过程中的弹簧扭矩和摩擦阻力十分复杂,其数学模型很难精确建立,参数不易获取.针对电子节气门的非线性因素,提出一种内模控制器的设计方法.首先分析电子节气门系统的数学模型,在Matlab/Simulink仿真平台上对模型的有效性进行验证,进而以内模控制结构为基础,建立电子节气门复域模型,分析系统的非线性干扰,设计针对时变参数的内模控制器.仿真结果显示,在模型较精确的情况下,内模控制器具有优于传统PID和一般滑模控制的控制性能,而在模型失配的情况下,内模控制器的鲁棒性能够保证它的控制性能仍然优于传统PID.在所提出的内模控制器设计方法中,前馈滤波器的设计并未用到任何系统参数,但仍然能够保证理想的稳态响应和扰动响应,因此所提出方法相比于很多针对具体模型的控制策略,具有更好的实用价值.     

基于变频干扰的前馈-反馈控制器设计

针对存在变频干扰的三容水箱液位系统的开环不稳定、大惯性、大时滞等特性,结合常规PID控制和前馈控制的优点,提出一种前馈-反馈复合控制方案：添加以变频器扰动量为对象的纯比例前馈补偿器与常规PID反馈控制器复合控制调节器的输出,以抵消变频干扰和其他扰动对被控对象的影响。运用智能仪表在组态环境下的实验结果表明：与常规PID控制系统所得的数据相比较,前馈-反馈控制系统有明显的优势,超调量小而且滞后时间小等特点;既保证了系统稳态效果,又提高了系统的动态性能。     

Linear parameter varying PID controller design for charge control of a spark-ignited engine

This paper presents the design and experimental test of a fixed-structure LPV controller for the charge control of a spark-ignition engine. A nonlinear model of the plant is transformed into an affine LPV model in the form of an LFT representation. Using a hybrid evolutionary-algebraic synthesis approach that combines LMI techniques based on K-S iteration with evolutionary search, a scheduled PID controller is designed. To reduce conservatism, the technique of quadratic separators is used in the analysis step. To improve tracking behavior, the gain scheduled feedback controller is supported by an LTI feedforward controller. The controller has been implemented on a standard electronic control unit, and experimental results on a test car illustrate that it meets the performance requirements in a wide range of operation.     

Energy-based control of a distributed solar collector field

Model-based control of the outlet temperature of a distributed solar collector field is studied. An energy-based controller is derived using internal energy as a controlled variable. The controller relies on a distributed parameter nonlinear plant model and includes feedforward from the solar irradiation and inlet temperature. Convergence of the closed loop is proved, and the method is experimentally verified to perform well on a pilot-scale solar power plant.     

基于模糊PID前馈控制的VRV空调控制方法研究

变制冷剂流量（VRV）空调系统由于其舒适性、环保性和节能性得到了广泛的应用,但是系统具有多变量、非线性、强耦合等特点。对于这个问题,在VRV空调系统房间模型基础上,应用仿真实验以及数学建模的方式建立蒸发器过热度、制冷剂质量流量以及电子膨胀阀的数学关系,通过前馈控制满足了有效抵消各蒸发器之间耦合量的需求;通过模糊PID控制器可以体现不同蒸发器之间的耦合关系,同时通过模糊补偿器还可以提高系统建模的精度。最后经过仿真和实验结果发现,经过模糊PID控制以及前馈控制以后,其他房间由于耦合性对于被控房间所造成的的扰动可以被有效抵消,实现了被控房间的稳定运行的目的。通过设计和实验仿真证明了模糊PID控制器的有效性以及前馈模糊控制器良好的控制性。     

Computational intelligence approach to PID controller design using the universal model

Despite the popularity of PID (Proportional-Integral-Derivative) controllers, their tuning aspect continues to present challenges for researches and plant operators. Various control design methodologies have been proposed in the literature, such as auto-tuning, self-tuning, and pattern recognition. The main drawback of these methodologies in the industrial environment is the number of tuning parameters to be selected. In this paper, the design of a PID controller, based on the universal model of the plant, is derived, in which there is only one parameter to be tuned. This is an attractive feature from the viewpoint of plant operators. Fuzzy and neural approaches - bio-inspired methods in the field of computational intelligence - are used to design and assess the efficiency of the PID controller design based on differential evolution optimization in nonlinear plants. The numerical results presented herein indicate that the proposed bio-inspired design is effective for the nonlinear control of nonlinear plants.     

Robust self-tuning PID controller for nonlinear systems

In this paper, we propose a robust self-tuning PID controller suitable for nonlinear systems. The control system employs a preload relay (P_Relay) in series with a PID controller. The P_Relay ensures a high gain to yield a robust performance. However, it also incurs a chattering phenomenon. In this paper, instead of viewing the chattering as an undesirable yet inevitable feature, we use it as a naturally occurring signal for tuning and re-tuning the PID controller as the operating regime digresses. No other explicit input signal is required. Once the PID controller is tuned for a particular operating point, the relay may be disabled and chattering ceases correspondingly. However, it is invoked when there is a change in setpoint to another operating regime. In this way, the approach is also applicable to time-varying systems as the PID tuning can be continuous, based on the latest set of chattering characteristics. Analysis is provided on the stability properties of the control scheme. Simulation results for the level control of fluid in a spherical tank using the scheme are also presented.