Dynamic identification of a synchronous machine using an extended sliding mode observer

This paper presents two identification methods for permanent magnet synchronous machine based on sliding modes. The first one is a new algorithm obtained from an identification technique based on an extended sliding mode observer and a least square solution using an instrumental variable. The second approach uses a direct identification algorithm using a sliding mode observer. Both techniques are tested in simulation and applied in experimentation on a synchronous motor. A comparison study is done in the aim of enhancing their performances.     

Parametric system identification using neural networks

Neural networks are used in many applications such as image recognition, classification, control and system identification. However, the parameters of the identified system are embedded within the neural network architecture and are not identified explicitly. In this paper, a mathematical relationship between the network weights and the transfer function parameters is derived. Furthermore, an easy-to-follow algorithm that can estimate the transfer function models for multi-layer feedforward neural networks is proposed. These estimated models provide an insight into the system dynamics, where information such as time response, frequency response, and pole/zero locations can be calculated and analyzed. In order to validate the suitability and accuracy of the proposed algorithm, four different simulation examples are provided and analyzed for three-layer neural network models.     

带参数辨识的自适应二阶滑模观测器PMSM无传感器矢量控制

针对表贴式永磁同步电机无位置传感器矢量控制系统, 提出一种具有电机参数在线辨识的基于Super-twisting algorithm的自适应二阶滑模观测器.在两相静止坐标系下,将模型参考自适应方法与基于Super-twisting algorithm的二阶滑模方法相结合,实现反电动势的准确估计.采用李亚普诺夫理论证明观测器的稳定性,并由李亚普诺夫稳定性方程推导定子电阻和转子转速的自适应律.在同步旋转坐标系下,采用二阶滑模观测器估计永磁磁链,并将其输入位置跟踪观测器估计转子位置.该算法充分抑制了滑模抖振,同时避免了低通滤波和相位补偿环节的使用,转子位置检测不受定子电阻和永磁磁链变化的影响,具有较强的鲁棒性.仿真结果验证了所提出算法的有效性.     

Observation and identification of mechanical systems via second order sliding modes

A second-order sliding-mode observer based on the modified super-twisting algorithm providing finite time exact observation is applied for system identification. The value of the equivalent output injection is used to identify perturbations directly. Continuous time versions of least square and forgetting factor methods are proposed to identify unknown time-invariant parameters respectively.     

Nonlinear robust fault reconstruction and estimation using a sliding mode observer

This paper considers fault detection and estimation issues for a class of nonlinear systems with uncertainty, using an equivalent output error injection approach. A particular design of sliding mode observer is presented for which the parameters can be obtained using LMI techniques. A fault estimation approach is presented to estimate the fault and the estimation error is dependent on the bounds on the uncertainty. For a special class of uncertainty, a fault reconstruction scheme is presented where the reconstructed signal can approximate the fault signal to any accuracy. The proposed fault estimation/reconstruction signals are only based on the available plant input/ouput information and can be calculated on-line. Finally, a simulation study on a robotic arm system is presented to show the effectiveness of the scheme.     

Observer based fault reconstruction schemes using terminal sliding modes

ABSTRACT

Two state/fault estimation methods using terminal sliding mode (TSM) concepts are presented in this paper. In contrast with conventional sliding modes, which guarantee asymptotic convergence of non-output estimation errors and faults, TSMs enable finite time convergence of estimation errors for faults and all the states. The minimum-phase condition, as a common condition required for fault estimation, is released in the proposed methods. Method I implements fractional power of the so-called switching term to make it robust against matched faults and disturbances. Compared with previous terminal scheme, this method covers a wider class of systems. In Method II, fractional power sliding variable is considered to achieve finite time convergence of estimation errors and their derivatives. In contrast with Method I, this approach is also robust against unmatched faults. Finally, the methods are applied to an unstable aircraft model.     

Robust reduced-order sliding mode observer design

In this article, a triple state and output variable transformation-based method combined with linear matrix inequality (LMI) techniques to design a new robust reduced-order sliding mode observer for perturbed linear multiple-input and multiple-output systems is developed. The state and output variables of the original system are triple transformed into suitable canonical form coordinates to facilitate the design of a reduced-order observer. The existing transformations are summarised in this study and presented systematically. A new combined observer configuration is proposed and compared with another type of observers. Global asymptotical stability LMI and sliding mode existence conditions for the coupled observer error system are derived using Lyapunov full quadratic form. Reaching and sliding modes of motion of decoupled observer error system are discussed as well. Two numerical and simulation examples are given to illustrate the usefulness of the proposed design techniques.     

Fault tolerant control using sliding modes with on-line control allocation

This paper proposes an on-line sliding mode control allocation scheme for fault tolerant control. The effectiveness level of the actuators is used by the control allocation scheme to redistribute the control signals to the remaining actuators when a fault or failure occurs. The paper provides an analysis of the sliding mode control allocation scheme and determines the nonlinear gain required to maintain sliding. The on-line sliding mode control allocation scheme shows that faults and even certain total actuator failures can be handled directly without reconfiguring the controller. The simulation results show good performance when tested on different fault and failure scenarios.     

Parametric identification of linear systems using Laplace transform

Proposed was a method for identification of the transfer function coefficients of the stationary one-input one-output linear system using the Laplace images of the input and output measurements. The measurement processes are considered over the given set of values of the transformation parameter. The a posteriori density of distribution of the vector of identified parameters was determined with regard for the autocovariance functions of the measurement errors. A generalization to the multiple-input multiple-output linear system with perturbations and measurements of the state coordinates was described.     

采用鲁棒滑模观测器实现一类混沌系统的同步

提出一种鲁棒滑模观测器，并应用于一类混沌系统的同步，该鲁棒滑模观测器通过滑模与相应的控制策略来实现，可调整观测器跟踪系统状态的收敛速度，实现两个混沌系统的同步，将所提出的鲁棒滑模状态观测器用于一类存在参数摄动和／或干扰的混沌系统的同步具有鲁棒性，该鲁棒滑模状态观测器不仅能实现低维的混沌系统的同步，而且能实现超混沌系统的同步，以Chua’s电路和超混沌Roessler系统为例给出了设计过程和仿真实验，其结果验证了所提出方法的有效性。     

Parametric eigenvalue-eigenvector assignment in reduced-order observer design

The design of reduced-order state observers for linear multivariable systems is considered. The procedure used is based on the assignment of prespecified sets of eigenvalues and associated eigenvectors to the observer model, whereby the state estimation error is effectively governed. It is shown, in particular, that the restrictions on the assignable eigenvectors are removed when the number of system outputs equals or exceeds half the number of state variables. Moreover, with the outputs in excess of half the state variables, some design parameters remain unaffected by the assignment of both sets of eigenvalues and eigenvectors. A certain part of these additional parameters can be adjusted to alleviate the impact of misalignment between the system and the observer initial states. The remaining part contributes to the identification of the observer matrices—other than the dynamical coefficient matrix. The one-to-one correspondence between the observability of the system and the eigenvalue assignability of the observer in the framework of this approach is demonstrated.     

FPGA-realization of a sensorless speed controller for PMSM drives using novel sliding mode observer

Microsystem Technologies - FPGA-realization of a rotor position estimation algorithm based on a novel sliding mode observer (SMO) for permanent magnet synchronous motor (PMSM) drives is adopted in...     

基于高阶滑模观测器的自适应时变滑模再入姿态控制

针对再入飞行器鲁棒姿态控制问题, 提出一种基于高阶滑模观测器的自适应时变滑模控制器设计方法. 首先, 设计了一种时变滑模面, 并在此基础上推导了相应的时变滑模控制律, 其中滑模控制中切换增益通过一种自适应算法获得, 消除了控制器设计过程中对系统不确定性上界已知的要求; 然后, 利用高阶滑模观测器对控制器设计过程中用到的姿态角导数信息进行观测, 同时能够获得系统扰动估计值, 从而构造一种基于观测器的控制器形式; 最后, 通过仿真验证了所提出的控制算法在提高再入飞行器姿态控制精度以及系统鲁棒性方面的有效性.     

Variable structure systems with sliding modes

Variable structure systems consist of a set of continuous subsystems together with suitable switching logic. Advantageous properties result from changing structures according to this switching logic. Design and analysis for this class of systems are surveyed in this paper.     

Modeling and online parameter estimation of intake manifold in gasoline engines using sliding mode observer

Model based control of automotive engines for fuel economy and pollution minimization depends on accuracy of models used. A number of mathematical models of automotive engine processes are available for this purpose but critical model parameters are difficult to obtain and generalize. This paper presents a novel method of online estimation of discharge coefficient of throttle body at the intake manifold of gasoline engines. The discharge coefficient is taken to be a varying parameter. Air mass flow across the throttle body is a critical variable in maintaining a closer to stoichiometric air fuel ratio; which is necessary to minimize the pollution contents in exhaust gases. The estimation method is based on sliding mode technique. A classical first Sliding mode observer is designed to estimate intake manifold pressure and the model uncertainty arising from the uncertain and time varying discharge coefficient is compensated by the discontinuity/switching signal of sliding mode observer. This discontinuity is used to compute coefficient of discharge as a time varying signal. The discharge coefficient is used to tune/correct the intake manifold model to engine measurements. The resulting model shows a very good agreement with engine measurements in steady as well s transient state. The stability of the observer is shown by Lyapunov direct method and the validity of the online estimation is successfully demonstrated by experimental results. OBD-II (On Board Diagnostic revision II) based sensor data acquisition from the ECU (Electronic Control Unit) of a production model vehicle is used. The devised algorithm is simple enough to be designed and implemented in a production environment. The online estimation of parameter can also be used for engine fault diagnosis work.     

Robust decentralized actuator fault detection and estimation for large-scale systems using a sliding mode observer

In this paper, robust decentralized actuator fault detection and estimation is considered for a class of non-linear large-scale systems. A sliding mode observer is proposed together with an appropriate coordinate transformation to find the sliding mode dynamics. Then, based on the features of the observer, a decentralized fault estimation strategy is proposed using an equivalent output error injection, and a decentralized reconstruction scheme follows by further exploiting the structure of the uncertainty which is allowed to have non-linear bounds. The estimation and reconstruction signals only depend on the available measured information and thus the proposed strategy can work on-line. The theoretical results which have been obtained are applied to an automated highway system. Simulation shows the feasibility and effectiveness of the proposed scheme.     

一种滑模观测器的多故障诊断方法

针对非线性系统的执行器故障及传感器故障,提出一种鲁棒多故障检测方法．首先,对可能发生的每种执行器故障分别构造模型,并设计相应的滑模观测器用于残差生成,从而实现执行器故障检测．然后,设计一种算法,利用简单滤波器将传感器故障转换为执行器故障,从而直接利用执行器故障检测的方法实现传感器故障的检测,将执行器故障的检测方法推广到执行器、传感器故障同时存在的情况．最后,通过在单关节机械手中的仿真应用验证了所提方法的有效性．     

非线性不确定系统的鲁棒滑模观测器设计

对非线性不确定性系统,提出一种鲁棒滑模观测器.所提出的鲁棒滑模观测器通过滑模与相应的控制策略来实现,设计参数的选取不需要求解大量方程,同时能保证对系统的非线性不确定项具有鲁棒性.通过设计滑模,可以调整观测器跟踪系统状态的收敛速度,使状态估计达到预期的指标.仿真结果验证了提出方法的有效性.     

A new methodology for observer design and implementation

Observers are usually formulated as explicit systems of differential equations and implemented using standard ODE solvers. In this paper, we show that there can be advantages in formulating the observer as a differential-algebraic equation (DAE). We propose a canonical DAE observer and show that it can be implemented using standard DAE solvers. The DAE implementation of the observer can be considered regardless of the design philosophy used. We present a simple design strategy for this canonical DAE observer based on the extended linearization method     

Virtual sensing of load forces in hydraulic actuators using second- and higher-order sliding modes

External load forces are challenging for sensing or estimating in the hydraulic actuators. Once it is due to inconvenient instrumentation of the force sensors, especially on an open-end mechanical interface. The other way, the complex nonlinear system behavior aggravates reconstructing the system states in a robust and real-time suitable manner. This paper proposes a sensorless estimation of external load forces in standard hydraulic actuators by using a well-established equivalent output injection of the second-order sliding mode and also higher-order sliding mode differentiator. Only the basic inertial and frictional parameters are assumed to be known from an initial identification without external load. Afterwards, the robust exact differentiators are used in order to reconstruct the system states. Noisy signals of the cylinder chamber pressures and piston stroke are the single quantities available from the measurement. An experimental case study, accomplished on the setup of two hydraulic cylinders arranged and operated in antagonistic way, is provided. The force-cell on the rigid interface between both cylinders is used for reference measurements and evaluation of the estimation algorithms. Two estimation approaches, one of the 2nd and another of the 4th order, are assessed in performance and compared to each other along with discussion.