基于卷积神经网络的永磁同步电机转矩观测器

内嵌式永磁同步电机具有高功率密度、高可靠性和弱磁性等诸多优点,但由于电动机参数具有非线性化特征,导致电磁转矩难以精确估算。该文提出了一种基于卷积神经网络的电磁转矩估算方 法,即转矩观测器。首先,基于所搭建的高保真非线性内嵌式永磁同步电机模型,获得用于神经网络训练的转矩观测器数据;然后,基于所提出的卷积神经网络转矩观测器实现内嵌式永磁同步电机的精确控制;最后,为获取最优的转矩估算误差,在仿真实验阶段对不同参数和结构的卷积神经网络进行了对比和分析。结果表明,该神经网络可以实现电磁转矩的准确估算,所建立的转矩观测器具有良好的性能参数和泛化能力。     

Modeling and vibration control for a flexible pendulum inverted system based on a PDE observer

This study addresses the problem of trajectory control of a flexible pendulum inverted system on the basis of the partial differential equation (PDE) and ordinary differential equation (ODE) dynamic model. One of the key contributions of this study is that a new model is proposed to simplify the complex system. In addition, this study proposed a nonlinear PDE observer to estimate distributed positions and velocities along flexible pendulum. Singular perturbation method is proposed to solve the coupling system of nonlinear PDE observer. The nonlinear PDE observer is divided into a fast subsystem and a slow subsystem by the use of the singular perturbation method. To stabilise this fast subsystem, a boundary controller is proposed at the free end of the beam. The sliding-mode control method is proposed to design controller for slow subsystems. The asymptotic stability of both the proposed nonlinear PDE observer and controller is validated by theoretical analysis. The results are illustrated by simulation.     

On the conditions of exponential stability in active disturbance rejection control based on singular perturbation analysis

Stability of active disturbance rejection control (ADRC) is analysed in the presence of unknown, nonlinear, and time-varying dynamics. In the framework of singular perturbations, the closed-loop error dynamics are semi-decoupled into a relatively slow subsystem (the feedback loop) and a relatively fast subsystem (the extended state observer), respectively. It is shown, analytically and geometrically, that there exists a unique exponential stable solution if the size of the initial observer error is sufficiently small, i.e. in the same order of the inverse of the observer bandwidth. The process of developing the uniformly asymptotic solution of the system reveals the condition on the stability of the ADRC and the relationship between the rate of change in the total disturbance and the size of the estimation error. The differentiability of the total disturbance is the only assumption made.     

Extended state observer-based motion synchronisation control for hybrid actuation system of large civil aircraft

Hybrid actuation system with dissimilar redundant actuators, which is composed of a hydraulic actuator (HA) and an electro-hydrostatic actuator (EHA), has been applied on modern civil aircraft to improve the reliability. However, the force fighting problem arises due to different dynamic performances between HA and EHA. This paper proposes an extended state observer (ESO)-based motion synchronisation control method. To cope with the problem of unavailability of the state signals, the well-designed ESO is utilised to observe the HA and EHA state variables which are unmeasured. In particular, the extended state of ESO can estimate the lumped effect of the unknown external disturbances acting on the control surface, the nonlinear dynamics, uncertainties, and the coupling term between HA and EHA. Based on the observed states of ESO, motion synchronisation controllers are presented to make HA and EHA to simultaneously track the desired motion trajectories, which are generated by a trajectory generator. Additionally, the unknown disturbances and the coupling terms can be compensated by using the extended state of the proposed ESO. Finally, comparative simulation results indicate that the proposed ESO-based motion synchronisation controller can achieve great force fighting reduction between HA and EHA.     

Consensus of linear multi-agent systems with exogenous disturbance generated from heterogeneous exosystems

This paper addresses the consensus tracking problem for multi-agent linear systems subject to exogenous disturbances generated from heterogeneous exosystems. For the case that the disturbances are generated from linear heterogeneous exosystems, a linear disturbance observer and distributed control law are proposed, and sufficient condition for consensus tracking is established by combining the input-to-state stability and Lyapunov analysis methods. For the case when the disturbances are generated from non-linear heterogeneous exosystems, a non-linear disturbance observer is presented to estimate such disturbance by using the dynamic gain technique; then, a distributed control law is designed, and sufficient condition is also presented for achieving consensus tracking. Two simulation examples are provided to demonstrate the effectiveness of the proposed consensus protocols.     

Distributed finite-time trajectory tracking control for multiple nonholonomic mobile robots with uncertainties and external disturbances

This paper investigates the distributed finite-time trajectory tracking control for a group of nonholonomic mobile robots with time-varying unknown parameters and external disturbances. At first, the tracking error system is derived for each mobile robot with the aid of a global invertible transformation, which consists of two subsystems, one is a first-order subsystem and another is a second-order subsystem. Then, the two subsystems are studied respectively, and finite-time disturbance observers are proposed for each robot to estimate the external disturbances. Meanwhile, distributed finite-time tracking controllers are developed for each mobile robot such that all states of each robot can reach the desired value in finite time, where the desired reference value is assumed to be the trajectory of a virtual leader whose information is available to only a subset of the followers, and the followers are assumed to have only local interaction. The effectiveness of the theoretical results is finally illustrated by numerical simulations.     

Simultaneous estimation of multiple channel faults for two-dimensional linear systems

This study focuses on the problem of simultaneous estimation of multiple channel faults for two-dimensional linear systems, which are described by Fornasini–Marchesini second (FM-II) model, and the faults that exist in state equation and measurement equation. By transforming the fault in the measurement equation as augmented state, the FM-II model with faults in the state equation and measurement equation can be rewritten into a singular system. Hence, several observers are proposed for the singular systems, and then the estimation of the faults in the state equation and measurement equation can be obtained. Using Lyapunov stability theory, sufficient conditions for the existence of the asymptotically stable observer and uniformly ultimately bounded observer are derived in the context of time domain. For the bounded observer, the upper bound of estimation error can be provided referring to the fault bound. Numerical and practical examples are given to demonstrate the effectiveness of the proposed method.     

Structure‐independent motion recovery from a monocular image sequence with low fill fraction

Real‐world image sequences are usually characterized by frequent loss and replacement of tracked feature data, and the key to accurate motion recovery from such image sequences lies in the synthesis of a structure‐independent dynamic filter that enables the replacement of lost point features with newly acquired points in a seamless manner. In this note, a novel nonlinear observer is proposed that relies on filtered estimates of optical flow to accomplish structure‐independent motion recovery from monocular image sequences with a low fill fraction. With a single component of linear velocity assumed known, the proposed scheme relies on the perspective observation of at least five points to yield exponentially convergent estimates of the unknown motion parameters that converge to a uniform, ultimate bound in the presence of model error. The unknown linear and angular velocities are assumed to be generated using an imperfectly known model that incorporates a bounded uncertainty, and optical flow estimation is accomplished using a robust differentiator that is based on the sliding‐mode technique. Numerical results are used to validate and demonstrate superior observer performance compared to a leading alternative design on a real‐world–like image sequence that is characterized by significant measurement noise and high feature turnover rate.     

Time‐varying input delay compensation for nonlinear systems with additive disturbance: An output feedback approach

This paper addresses the output feedback tracking control of a class of multiple‐input and multiple‐output nonlinear systems subject to time‐varying input delay and additive bounded disturbances. Based on the backstepping design approach, an output feedback robust controller is proposed by integrating an extended state observer and a novel robust controller, which uses a desired trajectory‐based feedforward term to achieve an improved model compensation and a robust delay compensation feedback term based on the finite integral of the past control values to compensate for the time‐varying input delay. The extended state observer can simultaneously estimate the unmeasurable system states and the additive disturbances only with the output measurement and delayed control input. The proposed controller theoretically guarantees prescribed transient performance and steady‐state tracking accuracy in spite of the presence of time‐varying input delay and additive bounded disturbances based on Lyapunov stability analysis by using a Lyapunov‐Krasovskii functional. A specific study on a 2‐link robot manipulator is performed; based on the system model and the proposed design procedure, a suitable controller is developed, and comparative simulation results are obtained to demonstrate the effectiveness of the developed control scheme.