Adaptive sliding mode control of modular self-reconfigurable spacecraft with time-delay estimation

The reconstruction control of modular self-reconfigurable spacecraft (MSRS) is addressed using an adaptive sliding mode control (ASMC) scheme based on time-delay estimation (TDE) technology. In contrast to the ground, the base of the MSRS is floating when assembled in orbit, resulting in a strong dynamic coupling effect. A TED-based ASMC technique with exponential reaching law is designed to achieve high-precision coordinated control between the spacecraft base and the robotic arm. TDE technology is used by the controller to compensate for coupling terms and uncertainties, while ASMC can augment and improve TDE’s robustness. To suppress TDE errors and eliminate chattering, a new adaptive law is created to modify gain parameters online, ensuring quick dynamic response and high tracking accuracy. The Lyapunov approach shows that the tracking errors are uniformly ultimately bounded (UUB). Finally, the on-orbit assembly process of MSRS is simulated to validate the efficacy of the proposed control scheme. The simulation results show that the proposed control method can accurately complete the target module’s on-orbit assembly, with minimal perturbations to the spacecraft’s attitude. Meanwhile, it has a high level of robustness and can effectively eliminate chattering.

Finite-time adaptive sliding mode control for heavyweight airdrop operations

This paper investigates the problem of designing a fast convergent sliding mode flight controller of a transport aircraft for heavyweight airdrop operations in the presence of bounded uncertainties without the prior knowledge of the bounds. On the basis of feedback linearization of the aircraft-cargo motion system, a novel integral sliding mode flight control law with gains adaptation is proposed. It contains a nominal control law used to achieve finite-time stabilization performance and a compensated control law used to reject the uncertainties. The switching gains of the compensated control law are tuned using adaptation algorithms, and the knowledge of the bounds of the uncertainties is not required to be known in advance. Meanwhile, the severe chattering of the sliding mode control that caused by high switching gains is effectively reduced. The controller and its performance are evaluated on a transport aircraft performing a maximum load airdrop task in a number of simulation scenarios.

Adaptive terminal sliding mode control for high-order nonlinear dynamic systems

An adaptive terminal sliding mode control (SMC) technique is proposed to deal with the tracking problem for a class of high-order nonlinear dynamic systems. It is shown that a function augmented sliding hyperplane can be used to develop a new terminal sliding mode for high-order nonlinear systems. A terminal SMC controller based on Lyapunov theory is designed to force the state variables of the closed-loop system to reach and remain on the terminal sliding mode, so that the output tracking error then converges to zero in finite time which can be set arbitrarily. An adaptive mechanism is introduced to estimate the unknown parameters of the upper bounds of system uncertainties. The estimates are then used as controller parameters so that the effects of uncertain dynamics can be eliminated. It is also shown that the stability of the closed-loop system can be guaranteed with the proposed control strategy. The simulation of a numerical example is provided to show the effectiveness of the new method.

Receding horizon H_∞ control for discrete-time Markovian jump linear systems

Receding horizon H∞ control scheme which can deal with both the H∞ disturbance attenuation and mean square stability is proposed for a class of discrete-time Markovian jump linear systems when minimizing a given quadratic performance criteria. First, a control law is established for jump systems based on pontryagin’s minimum principle and it can be constructed through numerical solution of iterative equations. The aim of this control strategy is to obtain an optimal control which can minimize the cost function under the worst disturbance at every sampling time. Due to the difficulty of the assurance of stability, then the above mentioned approach is improved by determining terminal weighting matrix which satisfies cost monotonicity condition. The control move which is calculated by using this type of terminal weighting matrix as boundary condition naturally guarantees the mean square stability of the closed-loop system. A sufficient condition for the existence of the terminal weighting matrix is presented in linear matrix inequality （LMI） form which can be solved efficiently by available software toolbox. Finally, a numerical example is given to illustrate the feasibility and effectiveness of the proposed method.

A current-mode buck DC–DC controller with adaptive on-time control

A current-mode buck DC-DC controller based on adaptive on-time （AOT） control is presented. The on-time is obtained by the techniques of input feedforward and output feedback, and the adaptive control is achieved by a sample-hold and time-ahead circuit. The AOT current-mode control scheme not only obtains excellent transient response speed, but also achieves the independence of loop stability on output capacitor ESR. In addition, the AOT current-mode control does not have subharmonic oscillation phenomenon seen in fixed frequency peak current-mode control, so there is no need of the slope compensation circuit. The auto-skip pulse frequency modulation （PFM） mode improves the conversion efficiency of light load effectively. The controller has been fabricated with UMC 0.6-μm BCD process successfully and the detailed experimental results are shown.

面向海流扰动和通信时延的欠驱动AUV编队跟踪控制

由欠驱动自主水下航行器(Autonomous Underwater Vehicle,AUV)编队组成的水下探测阵列具有响应快、机动性好、智能化程度高的特点。针对无速度信息传输的多AUV在海流和时延复合扰动下的编队控制问题,提出一种虚拟轨迹、轨迹预测、自适应反演滑模控制技术相结合的编队控制方法。使用领航者的位置信息和期望队形得到跟随者的参考轨迹,并引入虚拟轨迹使其与跟随者参考轨迹有限时间重合,从而得到跟随者的期望位置和速度。在此基础上,使用最小二乘法拟合轨迹曲线进行时延补偿,并通过自适应反演滑模控制技术完成海流干扰下的编队轨迹跟踪。理论分析和仿真结果表明,新方法具有可行性和有效性。

永磁直线同步电机改进预测电流控制

永磁直线同步电机(PMLSM)预测电流控制(PCC)时存在易受参数变化和延迟以及负载扰动影响,为此提出基于二阶超螺旋滑模观测器(STSMO)的改进型PCC。首先,建立包含不确定性的PMLSM动态数学模型。然后,为了补偿参数变化以及延迟的影响,采用二阶STSMO估计下一周期的电流和参数变化造成的扰动电压,估计值用以计算下一周期的给定电压,以提高电流跟踪精确度,通过李雅普诺夫函数证明观测器的稳定性。同时,采用基于改进指数趋近律的自适应滑模控制器(ASMC)对速度进行跟踪,将状态变量和滑模面加入到指数趋近律中,不仅削弱了电流抖振,且进一步提升了系统的鲁棒性。半实物仿真实验结果表明,与传统PCC相比,提出方法能有效地抑制不确定性对系统影响,使系统具有更好的跟踪性能和鲁棒性。

基于滑模自适应有限时间一致性算法的微电网二次控制

随着微电网规模日益增大,如何快速稳定完成二次控制目标是一个亟待解决的问题。因此首先针对现有微电网中分布式二次控制器的收敛速度问题,提出了一种基于自适应有限时间的分布式二次控制,所提的控制器在不同的场景下,可以通过分布式的方式来获取当前情况下最适合的有限时间控制器的收敛系数,从而加快二次控制的速度。其次针对分布式控制器易受到扰动而无法完成控制目标的问题,设计了基于滑模控制的分布式有限时间控制器来消除扰动影响。然后通过李雅普诺夫函数证明方法分析了所提策略的稳定性和可行性。最后通过MATLAB/Simulink搭建仿真模型,在4个不同的算例下验证了本文所提的控制策略的有效性和可行性。

一款高效率宽输入电压边界导通模式反激变换器

本文提出了一款高效率、宽输入电压的边界导通模式反激变换器结构。为了防止负载切换过程中芯片过压和欠压,提出了一种由电流调节电路(CRC)与自适应频率控制电路(AFCC)组成的新型模式切换环路,实现了芯片在不同模式之间的平滑切换,提高了负载的瞬态响应和转换效率;通过在环路中引入电流调节控制技术,减小了低纹波突发模式(LRBM)下的原边充电电流和输出最小负载电流,从而减小轻负载下的开关频率,降低功耗。基于0.18μmBCD工艺,实现了电路设计和版图设计,芯片面积为1.48×2.5mm^(2)。仿真结果表明,变换器在输入电压为3~32V、输出电压为5V时,轻、重负载切换过程中的输出电压瞬态响应最大变化为6%,峰值转换效率为88.6%。

Fixed-time adaptive model reference sliding mode control for an air-to-ground missile

This paper addresses the fixed-time adaptive model reference sliding mode control for an air-to-ground missile associated with large speed ranges, mismatched disturbances and un-modeled dynamics. Firstly, a sliding mode surface is developed by the tracking error of the state equation and the model reference state equation with respect to the air-to-ground missile. More specifically,a novel fixed-time adaptive reaching law is presented. Subsequently, the mismatched disturbances and the un-modeled dynamics are treated as the model errors of the state equation. These model errors are estimated by means of a fixed-time disturbance observer, and they are also utilized to compensate the proposed controller. Therefore, the fixed-time controller is obtained by an adaptive reaching law and a fixed-time disturbance observer. Closed-loop stability of the proposed controller is established. Finally, simulation results including Monte Carlo simulations, nonlinear six-DegreeOf-Freedom(6-DOF) simulations and different ranges are presented to demonstrate the efficacy of the proposed control scheme.

基于自适应有限时间控制策略的高分辨率显微镜运动控制

针对大数值孔径显微成像技术对物镜位移台提出的长行程、高精度和大负载的要求,提出了一种非线性鲁棒运动控制策略以实现物镜位移台的精密运动。设计了大数值孔径显微镜的光路系统、虚拟样机以及由滚珠丝杠驱动的物镜位移台,采用双螺母预紧的方式消除滚珠丝杠传动间隙。将自适应技术引入非奇异终端滑模控制,实现系统状态的有限时间收敛,提高系统鲁棒性。针对滚珠丝杠传动机构内部的非线性摩擦效应,采用时延估计技术实现摩擦力的在线估计和实时补偿,将时延估计技术和自适应非奇异终端滑模控制相结合获得无模型控制特性。通过Lyapunov理论证明了闭环系统的稳定性。搭建了一个高分辨率的光学显微镜,实现物镜位移台的精密运动,采集到小鼠心肌细胞的显微图像,证明了所提算法的有效性。

变分数阶不确定混沌系统的有限时间自适应滑模投影同步

研究变分数阶不确定混沌系统的有限时间自适应滑模投影同步问题.利用变分数阶微积分的性质,建立变分数阶有限时间收敛原理.设计变分数阶滑模面和自适应滑模控制器,得到变分数阶不确定混沌系统有限时间投影同步的充分条件,推导出投影同步时间的上界.仿真结果表明论文所设计控制器的有效性和鲁棒性.

考虑故障穿越和时变延迟的孤岛微网电压功率控制

为了解决孤岛交流微电网由时变通信延迟和不确定性故障引起的不稳定性问题,提出1种新型鲁棒分层控制方法。该方法包括级联结构的电流环、电压环、虚拟阻抗和下垂控制环。首先,在电流环中设计1种基于自适应反推积分非奇异快速终端滑模控制的鲁棒控制器,用于在未知有界不确定性和外部干扰时调节和跟踪电流参考值;接着,在电压环中采用混合H_(2)/H_(∞)控制,利用状态反馈控制律生成内环参考值,增加控制器对扰动的鲁棒性,并在线性矩阵不等式基础上给出充分条件。考虑到时变延迟TVD(time-varyingdelay)的不稳定影响,在第二控制层采用基于一致性的分布式协议,以提高控制器应对TVD的鲁棒性。然后,为提高系统的功率分配精度,采用下垂控制和虚阻抗环;最后,通过半实物仿真,评估了控制方法的性能,并验证了所提控制方法的有效性。与已有研究进行对比分析,仿真结果表明:所提方法在大、小信号扰动下的瞬态响应、稳态性能和故障穿越能力等方面具有一定的优越性。

压电快反镜的预定时间自适应滑模控制

针对压电快反镜系统(Piezoelectric Fast Steering Mirror,PFSM)在跟踪过程中由自身压电磁滞和外界环境所引起的不确定干扰问题,文中提出了一种创新的预定时间自适应滑模控制器。此控制器使用障碍函数设计自适应律,并引入了预定时间的概念,以确保系统的响应更加灵活和高效。在保证控制系统状态的收敛时间小于预定时间上界的基础上,该控制策略还可通过障碍函数将滑模变量的收敛范围限制在一个微小的邻域内。文中利用Lyapunov稳定性理论证明了闭环控制系统的稳定性。最后,通过数值仿真验证了所设计控制器的有效性。结果表明:该控制器在提升PSFM性能、缩短跟踪时间以及提高精度方面具有显著优势。

一种低谐波高效率CRM BOOST PFC变换器

为了在解决临界导通模式(CRM)中Boost功率因数校正变换器半负载时输入电流总谐波失真率(THD)与变换器运行效率之间的性能矛盾问题,在传统谐振时间控制的基础上提出了一种部分谐振时间控制方法,分析了部分谐振时间控制法对输入电流THD及变换器运行效率的改进效果;通过适当调整反向谐振时间,并由数字信号处理器DSP28032发出控制信号,决定开关管的开通时刻。最后搭建了一台400 W单相CRM Boost PFC变换器实验样机,实验结果表明,所提控制方法能在有效降低THD值的同时保证变换器的工作效率。

基于自适应滑模的直流微网光伏发电控制策略

针对双光伏直流微电网运行时存在光伏发电端光照不均、负载端突变导致的微电网系统运行不稳定问题,提出了一种双光伏直流微网有限时间非奇异自适应滑模控制方法,并利用李雅普诺夫稳定性理论证明了该方法的稳定性.该方法根据两个光伏发电单元输出电压与电流的变化来构建控制器中的状态变量,结合有限时间非奇异滑模控制策略,使两个光伏发电单元输出电压快速相等并达到设定值,进而减小由于负载突变或光照不均引起的母线电压波动.仿真结果表明,该方法可有效地解决光照不均、负载突变带来的母线电压波动问题,具有良好的抗干扰能力.

双足步行机器人嵌入式控制系统设计分析

双足步行机器人因其仿人类运动方式和优良的适应性,近年来成为机器人研究的热点。该文设计并实现一种基于嵌入式系统的双足步行机器人实时控制系统。通过引入滑模控制算法和自适应平衡模块,实现对机器人在不同环境下的稳定控制。实验结果表明,所设计的控制系统在跟踪领导者状态和同步控制左右两足运动方面表现出卓越的实时性和稳定性。该文的研究为双足步行机器人的智能化控制提供新的思路和方法。

基于自适应扰动补偿的有限时间滑模负荷频率控制

为解决可再生能源输出功率波动性导致的电力系统频率不稳定问题,提出了一种基于自适应扰动补偿的有限时间滑模负荷频率控制(LFC)策略,使得电力系统面对未知扰动时可以在有限时间内实现频率的快速稳定。首先,针对可再生能源输出功率和负荷不确定导致的扰动上界未知问题,引入了一种自适应滑模扰动观测器,在不需要扰动上界信息的情况下获得扰动估计值,并直接在输入通道实现扰动补偿;然后,将自适应滑模扰动观测器与非奇异终端滑模控制(TSMC)相结合,利用终端滑模的有限时间收敛特性实现频率快速稳定。仿真分析发现,所提出的控制策略在面对风光输出功率波动和系统负荷扰动的情况下能快速维持频率稳定,提高了系统调频性能。

Three-dimensional guidance law based on adaptive integral sliding mode control

For the terminal guidance problem of missiles intercepting maneuvering targets in the three-dimensional space, the design of guidance laws for non-decoupling three-dimensional engage- ment geometry is studied. Firstly, by introducing a finite time integral sliding mode manifold, a novel guidance law based on the integral sliding mode control is presented with the target acceler- ation as a known bounded external disturbance. Then, an improved adaptive guidance law based on the integral sliding mode control without the information of the upper bound on the target accel- eration is developed, where the upper bound of the target acceleration is estimated online by a designed adaptive law. The both presented guidance laws can make sure that the elevation angular rate of the line-of-sight and the azimuth angular rate of the line-of-sight converge to zero in finite time. In the end, the results of the guidance performance for the proposed guidance laws are pre- sented by numerical simulations. Although the designed guidance laws are developed for the con- stant speed missiles, the simulation results for the time-varying speed missiles are also shown to further confirm the designed guidance laws.