Event-triggered-based finite-time cooperative path following control for underactuated multiple marine surface vehicles

This paper develops an event-triggered-based finite-time cooperative path following (CPF) control scheme for underactuated marine surface vehicles (MSVs) with model parameter uncertainties and unknown ocean disturbances. First, a finite-time extended state observer (FTESO) is proposed, in which the FTESO can estimate the velocities and compound disturbances in finite time. Then, the finite-time LOS guidance law based on velocity estimation values is designed to obtain the desired surge velocity and the desired yaw rate. In order to realize the cooperative control of multiple paths in finite time, the cooperative control law for the path variable is designed. In addition, the relative threshold event-triggered control (ETC) mechanism is incorporated into the formation control algorithm, and an event-triggered-based finite-time CPF controller is designed, which not only effectively reduces the update frequency of controller and the mechanical loss of actuator but also improves the control performance of system. Furthermore, by using homogeneous method, Lyapunov theory, and finite-time stability theory, it is proved that under the proposed finite-time CPF control scheme, the formation errors can converge to a small neighborhood around origin in finite time. Finally, numerical simulation results illustrate the effectiveness of the proposed control scheme.     

Fault‐tolerant spacecraft attitude control under actuator saturation and without angular velocity

In this paper, a fault‐tolerant control scheme is proposed to control the attitude of a rigid spacecraft subject to external disturbances and multiple system uncertainties, as well as actuator faults and saturation. More challengingly, it is assumed that the angular velocity is unavailable. A super‐twisting observer with time‐varying gain is firstly designed to accurately estimate the angular velocity in finite time. The choice of the time‐varying gain is dependent on a state‐norm estimate. Then, using the information from the observer (estimate of angular velocity), a fault‐tolerant controller is proposed, where an adaptive law is introduced to address the unknown loss of effectiveness and neural networks are used to approximate the unknown nonlinear functions. It is proved that the attitude orientations converge to the desired values at a fixed time. Finally, a simulation example is utilized to verify the effectiveness of the proposed scheme.     

无位置传感器的BLDC控制设计与调制优化

基于无位置传感器控制设计了一种可应用于三相直流无刷电机的驱动控制器,采用反电动势法检测转子位置,梯形波驱动控制方式实现BLDC电机的启转 、运行.介绍了BLDC运行原理及实现无位置传感控制方法,探讨了如何选择最佳调制方式及电机速度最快时的换相时机,并优化了调制方法.本文设计的控制器具有启转顺 、加速快 、防输出短路等特点,适用于多种高低速 、高低电压BLDC.     

Robust adaptive admittance control of an exoskeleton in the presence of structured and unstructured uncertainties

In this paper, an admittance control scheme for a user-in-charge exoskeleton is presented. The controller basically consists of a composite adaptive controller implementing a feedback law to estimate the structured uncertainties and to modify the apparent dynamics of the robot, and an LWPR estimator which tries to give an appropriate approximation of unmodeled uncertainty along with a robust term aiming to overcome the approximation residue. The control scheme offers a unified general control structure that explains the effect of each control component on the others. It is proved that based on the developed controller, the tracking and estimation errors converge to small boundaries with ultimate boundedness property due to the presence of the unstructured uncertainty. Based on simulations of a 2-DOF leg, the effectiveness of the controller is investigated. The results show the effectiveness of employing a universal approximator alongside a robust adaptive control and the success of the recommended approach in estimating model parameters and unmodeled dynamics simultaneously.     

汽车电子燃油泵中无刷无位置传感器直流电机控制研究

针对现有汽车电子燃油泵电机油品适应性差、噪声大、寿命短等问题,设计了一种无刷无位置传感器电机控制系统,并应用于电子燃油泵中.在分析无刷电机旋转原理的基础上,利用反电动势法在控制程序中构造虚拟中性点电压来确定反电动势过零点信号,并结合预定位启动法进行启动,从而实现了无刷无位置传感器电机的控制.实验表明:该系统能够准确判断电机反电动势过零点信号,电机运行平稳,且输出油量满足实际需求.     

一类不确定非线性系统的重复学习控制

针对一类在有限时间区间上重复作业的不确定非线性系统,本文提出一种重复学习控制方法,用于解决非参数不确定性问题.该方法采用死区修正学习律对期望控制输入与界函数进行估计,以避免参数的正向累加导致系统发散,并使该控制算法较少地依赖于系统信息,更方便于控制器的实现.基于Lyapunov方法所设计的控制器,保证了闭环系统所有信号的有界性,并使得跟踪误差收敛于死区界定的邻域.通过仿真算例及电机实验结果验证所提学习控制算法的有效性.     

Output feedback second order sliding mode control for spacecraft attitude and translation motion

This paper studies an output feedback control problem for spacecraft position and attitude control when uncertainties related to system parameters and external disturbances are present. Firstly, a new finite-time control law is designed using second order sliding mode concepts. In the presence of external disturbances and inertia uncertainties, the new control law provides finite-time convergence and high tracking precision. Secondly, a new sliding-mode-based filter is developed to estimate the first time derivatives of attitude and position in finite time. Instead of the translational and angular velocity variables, the estimated derivative values are used for the controller design. The proposed controller with this filter is an output feedback controller since translational and angular velocity measurements are not required. The closed-loop system under this controller is non-homogeneous and the stability is proven by using concepts of a strong Lyapunov function and Lyapunov stability theory. The trajectories of the closed-loop system can be controlled to converge to a ball centered at the origin that can be made as small as desired. Numerical simulations of position and attitude control of spacecraft are given to demonstrate the performance of the proposed controller and filter.     

New variable gain super-twisting sliding mode observer for sensorless vector control of nonsinusoidal back-EMF PMSM

This paper presents a new discrete-time super-twisting sliding mode observer with variable gains for sensorless nonsinusoidal vector control of permanent magnet synchronous motors. This observer is adopted to estimate the back electromotive forces (back-EMF) that are required for the rotor speed estimation and for the nonsinusoidal vector control. In addition, their gains are time-varying to minimize the chattering. So, they are adjusted based on internal states of the super-twisting algorithm. The stability analysis is investigated from the Lyapunov theory for discrete-time systems. Finally, simulation and experimental results are presented to demonstrate the good performance and the effectiveness of the proposed observer.     

Task-space fully distributed tracking control of networked uncertain robotic manipulators without velocity measurements

This paper investigates the task-space synchronised tracking problem of uncertain networked manipulators interconnected on directed graphs, where the dynamic leader is available to only a subset of followers and followers have only local interaction. A fully distributed tracking controller is proposed, which is composed of a distributed desired trajectory estimator, a joint-space velocity observer and an adaptive cooperative control algorithm. Specifically, the proposed controller allows each manipulator to track the dynamic leader solely using local task-space position measurements. Besides, in the presence of both dynamic and kinematic uncertainties, the adaptive cooperative control algorithm indeed improves the system's robustness. Furthermore, it is strictly proved that the proposed control scheme ensures that both task-space position and velocity tracking errors converge to zero as time tends to infinity. In the end, simulation results are provided to demonstrate the effectiveness of the proposed controller.     

基于快速终端滑模面的两旋翼飞行器有限时间姿态控制

针对带有模型不确定和外部干扰的两旋翼飞行器,提出一种基于快速终端滑模面的有限时间自适应姿态控制方法,保证两旋翼飞行器对期望姿态角度的有限时间跟踪。构造快速终端滑模面,并设计分段连续函数避免滑模变量求导产生的奇异值问题。在此基础上,设计有限时间姿态控制器,并设计系统不确定上界的自适应更新律,抵消模型不确定性和外部干扰的影响。经李雅普诺夫方法证明滑模变量、姿态角误差、角速度误差等闭环信号最终一致有界,且有限时间收敛至平衡点邻域,收敛时间与系统状态变量初始值有关。最后,采用了矩形波和 曲线作为设定信号,设计相应的跟踪实验,并在两旋翼飞行器平台上验证所提控制方法的有效性,且分析双曲正切函数对系统控制输入影响,经实验测试其可减少系统颤振现象。     

A speed-sensorless indirect field-oriented control for induction motors based on high gain speed estimation

The authors design a new speed sensorless output feedback control for the full-order model of induction motors with unknown constant load torque, which guarantees local asymptotic tracking of smooth speed and rotor flux modulus reference signals and local asymptotic field orientation, on the basis of stator current measurements only. The proposed nonlinear controller exploits the concept of indirect field orientation (no flux estimation is required) in combination with a new high-gain speed estimator based on the torque current tracking error. The estimates of unknown load torque and time-varying rotor speed converge to the corresponding true values under a persistency of excitation condition with a physically meaningful interpretation, basically equivalent to non-null synchronous frequency. Stability analysis of the overall dynamics has been performed exploiting the singular perturbation method. The proposed control algorithm is a “true” industrial sensorless solution since no simplifying assumptions (flux and load torque measurements) are required. Simulation and experimental tests show that the proposed controller is suitable for medium and high performance applications.     

Supervisory control using a new control-relevant switching

This paper presents a new supervisory control scheme, which is based on a control-relevant switching logic. Unlike most of the existing switching methods considering only estimator performance, the proposed scheme takes both estimator and controller performance into account. As an index to the controller performance, an iISS (integral-input-to-state stability) Lyapunov function is employed; it is ensured that the Lyapunov function satisfies a certain inequality. This Lyapunov-based switching is then coupled to the state-dependent dwell-time switching developed recently, and the state of the uncertain plant is shown to converge asymptotically. The proposed supervisory control scheme is applied to an input-constrained neurally stable linear plant.     

A robust controller for trajectory tracking of a DC motor pendulum system

This work presents a solution to the output feedback trajectory tracking problem for an uncertain DC motor pendulum system under the effect of an unknown bounded disturbance. The proposed algorithm uses a Proportional Derivative (PD) controller plus a novel on-line estimator of the unknown disturbance. The disturbance estimator is obtained by coupling a standard second-order Luenberger observer with a third-order sliding modes differentiator. The Luenberger observer provides estimates of the motor angular position and velocity. Moreover, an ideal disturbance estimator in terms of the Luenberger observer error and its first and second time derivatives is obtained from the observer error formulae; these time derivatives are not available from measurements. Subsequently, the sliding modes third-order differentiator allows obtaining estimates of these time derivatives in finite time. The estimates replace the real values of the first and second time derivatives in the ideal disturbance estimator thus producing a practical disturbance estimator, and also permit obtaining an estimate of the motor angular velocity. A depart from previous approaches is the fact that the disturbance is not directly estimated by the Luenberger observer or the third-order differentiator. Numerical simulations and real-time experiments validate the effectiveness of the proposed approach.     

考虑输入受限的航天器安全接近姿轨耦合控制

针对存在外部扰动和输入受限的航天器安全接近的问题,当扰动上界未知时,基于积分滑模控制理论设计了抗饱和的有限时间自适应姿轨耦合控制器.控制器的设计过程中采用了新型的避碰函数限制追踪航天器运动区域进而保证接近过程中航天器的安全性,同时通过辅助系统和自适应算法分别处理了输入受限和扰动上界未知.借助李雅普诺夫理论证明了在控制器的作用下系统状态在有限时间内收敛,且能够保证追踪航天器在实现航天器接近的过程中不与目标航天器发生碰撞.最后通过数字仿真进一步验证了所设计控制器的有效性.     

Nonsingular terminal sliding mode control of nonlinear second‐order systems with input saturation

This paper considers the nonsingular terminal sliding mode (TSM) controller design for a nonlinear second‐order system subject to input saturation. A new nonsingular TSM manifold is constructed by integrating the conventional nonsingular TSM manifold with a saturation function. When the bound of the uncertainty is known, based on the designed TSM manifold, a saturated controller can be designed directly for the nonlinear system. When the bound of the uncertainty is unknown, a disturbance observer is first employed to estimate the uncertainty, followed by constructing a composite controller consisting of a bounded feedback controller and a forward compensator. Theoretical analysis shows that under the proposed two control methods, the states of the closed‐loop system will both converge to zero in finite time. Simulation results demonstrate the effectiveness of the proposed methods. Copyright © 2015 John Wiley & Sons, Ltd.     

Improved torque performance in BLDC-motor-drive through Jaya optimization implemented on Xilinx platform

Robust dynamic speed response with less maintenance and efficient operation makes the Brushless Direct Current (BLDC) motors as an oblivious choice for many motoring applications which needs instantaneous speed control while developing high torque. This paper proposes Jaya optimization Algorithm on Xilinx platform for BLDC Motor and Fractional Order Proportional Integral Derivative controller to improve its efficiency through minimizing the ripples present in the Torque of the motor. The control strategy of torque controller works with the combinations of Xilinx and optimization algorithms. In this proposed controller, the strategy of control is achieved after deriving the BLDC motor's dynamic mode there after the electronic interaction with BLDC motor is enrooted with the Math lab/Simulink model while tactically utilizing Xilinx tools for all kind of co-simulation in the same model. Initially the dynamic model of a BLDC motor drive is derived and the control topology is designed with the help of the proposed controller. The controlling mechanism established in this paper is effective and efficient in minimizing the ripples present in the torque of the motor. The proposed controller is utilized for possible low-cost and high-performance industrial applications. The results are obtained and analyzed with existing methodologies and it shows that the proposed technique outperforms the existing models.     

State observer-based robust control scheme for electrically driven robot manipulators

By using a state observer, a new robust trajectory tracking control scheme is developed in this paper for electrically driven robot manipulators. The role of the observer is to estimate joint angular velocities. The proposed controller does not employ adaptation, but assures robust stability of tracking error between joint angles and desired trajectories. At sacrificing asymptotical stability of the tracking errors, the configuration of the proposed controller becomes very simple, compared with regressor-based adaptive controllers. It is shown in the closed-loop system using the proposed controller that the Euclidian norm of tracking errors arrives at any small closed region with any convergent rate by setting only one design parameter. Especially for the desired trajectories converging to constant ultimate values, it is assured that tracking errors converge to zero.     

导弹姿态的自抗扰有限时间控制

针对导弹模型同时具有不确定性和执行机构饱和受限的问题, 首先针对模型不确定性, 将质心运动方程的非线性影响、耦合影响、外部环境干扰视为总干扰, 并设计扩展状态观测器对其进行实时估计; 然后针对舵偏角和角速度存在饱和受限的问题, 设计辅助系统和限幅微分器; 最后结合反演和有限时间稳定系统理论, 设计有限时间控制器, 以保证整个闭环系统在受限条件下能收敛到参考信号. 数值仿真结果表明, 所设计的控制器与理论分析结果一致, 是可行而有效的.

     

Output-feedback stabilization of stochastic nonlinear systems driven by noise of unknown covariance

We address the class of stochastic output-feedback nonlinear systems driven by noise whose covariance is time varying and bounded but the bound is not known a priori. This problem is analogous to deterministic disturbance attenuation problems. We first design a controller which guarantees that the solutions converge (in probability) to a residual set proportional to the unknown bound on the covariance. Then, for the case of a vanishing noise vector field, we design an adaptive controller which, besides global stability in probability, guarantees regulation of the state of the plant to zero with probability one.     

多伺服电机智能化协调容错轨迹跟踪控制系统设计

针对一类具有执行器、传感器故障的多伺服电机控制系统,设计了相应的多伺服电机智能化协调容错轨迹跟踪控制系统.首先,提出了一种新结构的分布式中间估计器,修改了其设计结构,提高了估计方案的可行性.其次,通过在线强化学习估计策略,可以显著提高估计性能,其核心是自适应切换机制与源故障模式定位功能块的集成,并根据估计值设计了协调容...