A compound scheme on parameters identification and adaptive compensation of nonlinear friction disturbance for the aerial inertially stabilized platform

A compound scheme is proposed to compensate the effect of nonlinear friction disturbance on the control precision of a three-axis inertially stabilized platform (ISP) for aerial remote sensing applications. The scheme consists of friction parameters identification and adaptive compensation. A LuGre model-based ISP friction model is first developed. Then, a comprehensive experimental scheme is proposed to obtain the static friction parameters. Further, the dynamic parameters are identified by experiments and dynamic optimization. On the basis of identified parameters and Lyapunov stability theory, a backstepping integral adaptive compensator is designed to compensate the nonlinear friction disturbance. Simulations and experiments are carried out to validate the scheme. The results show that the compound scheme can accurately obtain the friction parameters and improve the control precision and stability of ISP.     

New tuning method for PID controller

In this paper, a tuning method for proportional-integral-derivative (PID) controller and the performance assessment formulas for this method are proposed. This tuning method is based on a genetic algorithm based PID controller design method. For deriving the tuning formula, the genetic algorithm based design method is applied to design PID controllers for a variety of processes. The relationship between the controller parameters and the parameters that characterize the process dynamics are determined and the tuning formula is then derived. Using simulation studies, the rules for assessing the performance of a PID controller tuned by the proposed method are also given. This makes it possible to incorporate the capability to determine if the PID controller is well tuned or not into an autotuner. An autotuner based on this new tuning method and the corresponding performance assessment rules is also established. Simulations and real-time experimental results are given to demonstrate the effectiveness and usefulness of these formulas.     

PID控制器参数快速整定的新方法

本文分析了影响控制器参数整定的几个基本问题（控制目标、优化准则和被控过程的特性），提出了精确地确定被控过程模型参数的方法。通过计算机仿真，系统地提出了可适用于多容过程的ＰＩＤ控制器参数快速整定新方法。     

均匀控制器的设计及整定

本文根据优化方法对均匀控制器进行了设计，给出了均匀液位控制器的一种整定方法，简述了非线性控制及对不规则容器的校正，从而实现可以最大限度地使用容器的波动能力并由此使整个装置趋于平稳。     

Dual-rate-loop control based on disturbance observer of angular acceleration for a three-axis aerial inertially stabilized platform

This paper presents a dual-rate-loop control method based on disturbance observer (DOB) of angular acceleration for a three-axis ISP for aerial remote sensing applications, by which the control accuracy and stabilization of ISP are improved obviously. In stabilization loop of ISP, a dual-rate-loop strategy is designed through constituting inner rate loop and the outer rate loop, by which the capability of disturbance rejection is advanced. Further, a DOB-based on angular acceleration is proposed to attenuate the influences of the main disturbances on stabilization accuracy. Particularly, an information fusion method is suggested to obtain accurate angular acceleration in DOB design, which is the key for the disturbance compensation. The proposed methods are theoretically analyzed and experimentally validated to illustrate the effectiveness.     

基于自抗扰控制技术提高航空光电稳定平台的扰动隔离度

提出一种基于电流环的自抗扰控制新方法以进一步提高航空光电稳定平台的抗干扰能力。首先,利用电流环将硬件电路中复杂的电机模型简化为一阶模型,从而减小了由于参数过大噪声对扰动观测值的影响;然后,采用带宽单参数化的设计方法为简化后的一阶系统设计了扩张状态观测器及带扰动补偿的控制规律;最后,在飞行模拟转台中测试了自抗扰控制器对2.5Hz以内任意频率扰动的抑制能力,并与目前航空光电稳定平台中常用的平方滞后超前校正方法进行了对比。实验结果表明:与传统的平方滞后超前控制器相比,采用自抗扰控制器后系统的扰动隔离度至少提高了6.56dB;而且随着扰动频率大于0.5Hz,自抗扰控制器的扰动抑制能力更为明显,扰动隔离度最多可提高12.03dB。同时,自抗扰控制器具有很强的鲁棒性,允许被控对象参数在15%的范围内任意变化,可满足高精度航空光电稳定平台的性能要求,对提高航空光电稳定平台控制系统的抗扰动性能具有较高的实用价值。     

Design and robust tuning of control scheme based on the PD controller plus Disturbance Observer and low-order integrating first-order plus dead-time model

This paper presents an effective design and robust tuning method for the control structure based on a series PD controller and a simple Disturbance Observer. All elements of the proposed controller are directly obtained from the low-order Integrating First-Order Plus Dead-Time (IFOPDT) model, used to approximate essential dynamic characteristics of lag-dominant stable, integrating and unstable plants. The structure of the proposed controller is an effective, easy to implement and tune, extension of the series PID controller. For the same robustness, a better disturbance rejection response is obtained by the proposed controller than that of the PID, by adjusting only two parameters with a clear meaning. A comparison with well-tuned PIDs, done by simulations, and the experimental results, obtained on a real thermal power plant, confirm that high performance and robustness are obtained, for dynamic characteristics common to industrial processes.     

惯性稳定平台变置信度优化平滑CMAC复合控制

提出了一种基于变置信度(MC)及优化平滑算法(OS)的改进型小脑模型关节控制器(CMAC)复合控制方法,用于提高航空遥感惯性稳定平台控制系统指向精度及稳定性。首先,以CMAC学习过程中存储单元被激活的次数为依据,对存储单元设置不同的置信程度,提高了CMAC控制器的学习效率与控制精度,避免了系统动态跟踪中过学习发散现象而导致的控制系统精度下降甚至崩溃;其次,针对常规CMAC算法系统输出波动较大问题,加入优化权值算法,改善系统输出平滑性,提高了CMAC控制器的稳定性,避免了系统输出波动对电机及传动系统损害;最后对提出方法进行了仿真分析并利用实验室某三轴惯性稳定平台进行实验验证。实验结果表明:采用基于MCOS的改进型CMAC复合控制方法后,稳定平台系统控制精度、响应速度及输出平滑稳定性均得到有效提高,动基座推车实验框架角位置水平跟踪误差RMS值为0.021 6°,相对PID与常规CMAC控制方法分别降低了55.09%和30.55%。     

Design and implementation of continuous finite-time sliding mode control for 2-DOF inertially stabilized platform subject to multiple disturbances

Control performances of inertially stabilized platforms (ISPs) are always affected by various disturbed phenomena such as cross-couplings, mass unbalance, parameter variations, and external disturbances in real applications. To improve the dynamic response and the disturbance rejection ability of the ISP, a continuous finite-time sliding mode control (SMC) approach with cascaded control structure is proposed. By constructing a finite-time disturbance observer, the multiple disturbances are precisely estimated in real time without the complex modeling and calibration work. Under the field oriented control framework, for the stabilized loop subsystem, an improved super-twisting controller incorporating the disturbance estimates is developed whereas for the current loop subsystem, the super-twisting control method is directly employed. Finite-time convergence of the inertial angular rates is guaranteed with the continuous control action such that chattering is alleviated remarkably. Moreover, by utilizing the manner of disturbance compensation, the feedback control gains can be tuning down without sacrificing the disturbance rejection ability. Comparative experiments are performed to verify the effectiveness of the proposed control approach.     

航空遥感惯性稳定平台LuGre摩擦参数的分步辨识

由于航空遥感惯性稳定平台框架角运动受限,本文提出了基于LuGre摩擦模型进行参数初步和精确辨识的方法以进一步提高其控制精度。从数字控制系统出发,构建了摩擦参数辨识系统,把摩擦参数辨识问题转化为曲线拟合问题。通过限定输入信号幅值和频率,解决了框架角运动受限导致摩擦参数辨识困难的问题。结合数字控制系统特性,优先辨识摩擦线性项参数;根据摩擦静态和动态特性,提出分步夹逼和分步搜索法依次辨识剩余参数,完成初步辨识。然后代入初步辨识结果,用遗传算法完成摩擦参数的精确辨识。仿真结果表明:摩擦参数初步辨识误差小于5%,精确辨识误差小于0.7%;用辨识出的摩擦参数构建摩擦补偿器,系统对基座低频角运动干扰的抑制能力提高了4倍。最后,基于某原理样机开展了摩擦参数辨识和补偿实验,结果表明控制精度提高了1倍,证实了提出的辨识方法的有效性和工程实用意义。     

航空遥感惯性稳定平台齿隙非线性建模与补偿

针对航空遥感惯性稳定平台框架伺服系统中齿隙非线性环节造成的系统驱动延时、换向跳变及冲击振荡等问题,对航空遥感惯性稳定平台齿隙非线性进行建模与补偿.在分析齿隙非线性环节结构和传动特点基础上,建立了齿隙非线性死区模型;利用MATLAB仿真分析了齿隙对系统性能的影响;以框架伺服系统为研究对象,应用反步积分法,通过依次选择Lyapunov函数,设计了基于状态反馈的控制器,并进行实验验证.结果表明:齿隙误差补偿可有效提高系统控制精度;与传统PID控制相比,反步积分法显著降低了齿隙非线性对伺服系统性能的影响,在给定框架期望转角情况下,反步积分法比PID控制响应速度提高78.26％、稳态精度提高23.1％.     

A novel disturbance-observer based friction compensation scheme for ball and plate system

Friction is often ignored when designing a controller for the ball and plate system, which can lead to steady-error and stick-slip phenomena, especially for the small amplitude command. It is difficult to achieve high-precision control performance for the ball and plate system because of its friction. A novel reference compensation strategy is presented to attenuate the aftereffects caused by the friction. To realize this strategy, a linear control law is proposed based on a reduced-order observer. Neither the accurate friction model nor the estimation of specific characteristic parameters is needed in this design. Moreover, the describing function method illustrates that the limit cycle can be avoided. Finally, the comparative mathematical simulations and the practical experiments are used to validate the effectiveness of the proposed method.     

On performance analysis of ADRC for a class of MIMO lower-triangular nonlinear uncertain systems

This paper designs the active disturbance rejection control (ADRC) to achieve desired performance for a class of MIMO lower-triangular nonlinear systems with large uncertainties under un-matched condition. We develop the ADRC with a set of extended state observers, and prove that the closed-loop system can achieve satisfied dynamic performance. The theoretical results illustrate the relationship between the bound of the concerned error and the bandwidth of extend state observers.     

A hybrid disturbance rejection control solution for variable valve timing system of gasoline engines

A novel solution for electro-hydraulic variable valve timing (VVT) system of gasoline engines is proposed, based on the concept of active disturbance rejection control (ADRC). Disturbances, such as oil pressure and engine speed variations, are all estimated and mitigated in real-time. A feed-forward controller was added to enhance the performance of the system based on a simple and static first principle model, forming a hybrid disturbance rejection control (HDRC) strategy. HDRC was validated by experimentation and compared with an existing manually tuned proportional-integral (PI) controller. The results show that HDRC provided a faster response and better tolerance of engine speed and oil pressure variations.     

A new Smith predictor and controller for control of processes with long dead time

Good control of processes with long dead time is often achieved using a Smith predictor configuration. Typically a PI or PID controller is used; however, it is shown in this paper that for some situations improved set point and disturbance responses can be obtained if a PI-PD controller is used. Several methods are possible for selecting the parameters of the PI-PD controller but when the plant transfer function has no zeros, the use of the standard forms provides a simple algebraic approach, and also reveals why difficulties may be encountered if a PID controller is used. Some examples are given to show the value of the approach presented.     

Tuning of an optimal fuzzy PID controller with stochastic algorithms for networked control systems with random time delay

An optimal PID and an optimal fuzzy PID have been tuned by minimizing the Integral of Time multiplied Absolute Error (ITAE) and squared controller output for a networked control system (NCS). The tuning is attempted for a higher order and a time delay system using two stochastic algorithms viz. the Genetic Algorithm (GA) and two variants of Particle Swarm Optimization (PSO) and the closed loop performances are compared. The paper shows that random variation in network delay can be handled efficiently with fuzzy logic based PID controllers over conventional PID controllers.