Robust Adaptive Gain Higher Order Sliding Mode Observer Based Control-constrained Nonlinear Model Predictive Control for Spacecraft Formation Flying

This work deals with the development of a decentralized optimal control algorithm, along with a robust observer,for the relative motion control of spacecraft in leader-follower based formation. An adaptive gain higher order sliding mode observer has been proposed to estimate the velocity as well as unmeasured disturbances from the noisy position measurements.A differentiator structure containing the Lipschitz constant and Lebesgue measurable control input, is utilized for obtaining the estimates. Adaptive tuning algorithms are derived based on Lyapunov stability theory, for updating the observer gains,which will give enough flexibility in the choice of initial estimates.Moreover, it may help to cope with unexpected state jerks. The trajectory tracking problem is formulated as a finite horizon optimal control problem, which is solved online. The control constraints are incorporated by using a nonquadratic performance functional. An adaptive update law has been derived for tuning the step size in the optimization algorithm, which may help to improve the convergence speed. Moreover, it is an attractive alternative to the heuristic choice of step size for diverse operating conditions. The disturbance as well as state estimates from the higher order sliding mode observer are utilized by the plant output prediction model, which will improve the overall performance of the controller. The nonlinear dynamics defined in leader fixed Euler-Hill frame has been considered for the present work and the reference trajectories are generated using Hill-Clohessy-Wiltshire equations of unperturbed motion. The simulation results based on rigorous perturbation analysis are presented to confirm the robustness of the proposed approach.

PMSM speed control using adaptive sliding mode control based on an extended state observer

In this study,a composite strategy based on sliding-mode control( SMC) is employed in a permanent-magnet synchronous motor vector control system to improve the system robustness performance against parameter variations and load disturbances. To handle the intrinsic chattering of SMC,an adaptive law and an extended state observer( ESO) are utilized in the speed SMC controller design. The adaptive law is used to estimate the internal parameter variations and compensate for the disturbances caused by model uncertainty. In addition,the ESO is introduced to estimate the load disturbance in real time. The estimated value is used as a feed-forward compensator for the speed adaptive sliding-mode controller to further increase the system's ability to resist disturbances. The proposed composite method,which combines adaptive SMC( ASMC) and ESO,is compared with PI control and ASMC. Both the simulation and experimental results demonstrate that the proposed method alleviates the chattering of SMC systems and improves the dynamic response and robustness of the speed control system against disturbances.

Robot Interaction Force Estimation Using an Adaptive Sliding Mode Observer

In constrained motion control of a robot,the interaction force is an important variable,which directly describes the state of interaction.It is required in a number of algorithms for interaction control.Desirably,the interaction force has to be measured by force sensors.However,there are inherent limitations with force sensors,such as the cost,sensing noise,limited bandwidth,and the difficulty of physical location at the required place,which is dynamic.In the present paper,the interaction force is estimated by using high order sliding mode observers.An adaptive version of a high order sliding mode observer is developed to robustly reconstruct the interaction force.Experimental results are given to show the effectiveness of the developed algorithms.

Improved estimation of rotor position for sensorless control of a PMSM based on a sliding mode observer

This work proposes a new strategy to improve the rotor position estimation of a permanent magnet synchronous motor(PMSM) over wide speed range. Rotor position estimation of a PMSM is performed by using sliding mode observer(SMO). An adaptive observer gain was designed based on Lyapunov function and applied to solve the chattering problem caused by the discontinuous function of the SMO in the wide speed range. The cascade low-pass filter(LPF) with variable cut-off frequency was proposed to reduce the chattering problem and to attenuate the filtering capability of the SMO. In addition, the phase shift caused by the filter was counterbalanced by applying the variable phase delay compensation for the whole speed area. High accuracy estimation result of the rotor position was obtained in the experiment by applying the proposed estimation strategy.

Observer-Based Control for a Cable-Driven Aerial Manipulator under Lumped Disturbances

With the increasing demand for interactive aerial operations,the application of aerial manipulators is becoming more promising.However,there are a few critical problems on how to improve the energetic efficiency and pose control of the aerialmanipulator forpractical application.In this paper,a novel cable-drivenaerialmanipulatorused for remote water sampling is proposed and then its rigid-flexible coupling dynamics model is constructed which takes joint flexibility into account.To achieve high precision joint position tracking under lumped disturbances,a newly controller,which consists of three parts:linear extended state observer,adaptive super-twisting strategy,and fractional-order nonsingular terminal sliding mode control,is proposed.The linear extended state observer is adopted to approximate unmeasured states and unknown lumped disturbances and achieve model-free control structure.The adaptive super-twisting strategy and fractional-order nonsingular terminal sliding mode control are combined together to achieve good control performance and counteract chattering problem.The Lyapunovmethod is utilized to prove the overall stability and convergence of the system.Lastly,various visualization simulations and ground experiments are conducted,verifying the effectiveness of our strategy,and all outcomes demonstrate its superiorities over the existing control strategies.

Output feedback adaptive super twisting sliding mode control for quadrotor UAVs

In this paper, a sliding mode control with adaptive gain combined with a high-order sliding mode observer to solve the tracking problem for a quadrotor UAV is addressed, in presence of bounded external disturbances and parametric uncertainties. The high order sliding mode observer is designed for estimating the linear and angular speed in order to implement the proposed scheme. Furthermore, a Lyapunov function is introduced to design the controller with the adaptation law, whereas an analysis of finite time convergence towards to zero is provided, where sufficient conditions are obtained. Regarding previous works from literature, one important advantage of proposed strategy is that the gains of control are parameterized in terms of only one adaptive parameter, which reduces the control effort by avoiding gain overestimation. Numerical simulations for tracking control of the quadrotor are given to show the performance of proposed adaptive control–observer scheme.

Second-order terminal sliding mode control for hypersonic vehicle in cruising flight with sliding mode disturbance observer

This paper focuses on the design of nonlinear robust controller and disturbance observer for the longitudinal dynamics of a hypersonic vehicle （HSV） in the presence of parameter uncertainties and external disturbances. First, by combining terminal sliding mode control （TSMC） and second-order sliding mode control （SOSMC） approach, the second- order terminal sliding control （2TSMC） is proposed for the velocity and altitude tracking control of the HSV. The 2TSMC possesses the merits of both TSMC and SOSMC, which can provide fast convergence, continuous control law and high- tracking precision. Then, in order to increase the robustness of the control system and improve the control performance, the sliding mode disturbance observer （SMDO） is presented. The closed-loop stability is analyzed using the Lyapunov technique. Finally, simulation results illustrate the effectiveness of the proposed method, as well as the improved overall performance over the conventional sliding mode control （SMC）.

Integrated guidance and control of guided projectile with multiple constraints based on fuzzy adaptive and dynamic surface

Based on fuzzy adaptive and dynamic surface(FADS),an integrated guidance and control(IGC)approach was proposed for large caliber naval gun guided projectile,which was robust to target maneuver,canard dynamic characteristics,and multiple constraints,such as impact angle,limited measurement of line of sight(LOS)angle rate and nonlinear saturation of canard deflection.Initially,a strict feedback cascade model of IGC in longitudinal plane was established,and extended state observer(ESO)was designed to estimate LOS angle rate and uncertain disturbances with unknown boundary inside and outside of system,including aerodynamic parameters perturbation,target maneuver and model errors.Secondly,aiming at zeroing LOS angle tracking error and LOS angle rate in finite time,a nonsingular terminal sliding mode(NTSM)was designed with adaptive exponential reaching law.Furthermore,combining with dynamic surface,which prevented the complex differential of virtual control laws,the fuzzy adaptive systems were designed to approximate observation errors of uncertain disturbances and to reduce chatter of control law.Finally,the adaptive Nussbaum gain function was introduced to compensate nonlinear saturation of canard deflection.The LOS angle tracking error and LOS angle rate were convergent in finite time and whole system states were uniform ultimately bounded,rigorously proven by Lyapunov stability theory.Hardware-in-the-loop simulation(HILS)and digital simulation experiments both showed FADS provided guided projectile with good guidance performance while striking targets with different maneuvering forms.

Adaptive Sliding-Mode Tracking Control for an Uncertain Nonlinear SISO Servo System with a Disturbance Observer

An adaptive sliding mode controller with a disturbance observer(ASMC-DO) is proposed for the control of a single-input and single-output(SISO) servo system which has uncertain parameters, nonlinear friction,disturbance and input saturation. It is difficult to choose the suitable value of the parameters. The newly designed adaptive method is used to reduce the effects of system time-varying parameters, such as the moment of inertia and the damp coefficient. The robustness of object is improved. A DO is selected to approximate the compound disturbance and to render the estimate error convergent in finite time. The stability and the convergence of the closed-loop system are proved by using the Lyapunov theory. Experimental results show that the proposed ASMC-DO can better satisfy the influence of variable parameters and external disturbance to the control precision of the SISO servo system than other two controllers. The effectiveness of the proposed controller is showed. The control input stability and robust performances of the input saturation system are enhanced and the chattering is reduced.

Integral sliding mode control for flexible ball screw drives with matched and mismatched uncertainties and disturbances

The design of servo controllers for flexible ball screw drives with matched and mismatched disturbances and uncertainties is focused to improve the tracking performance and bandwidth of ball screw drives.A two degrees of freedom mass model is established based on the axial vibration characteristics of the transport ball screw,and the controller of an adaptive integral sliding mode is proposed combining the optimal design of state feedback gain matrix K to restrain the vibration and the matched disturbances and uncertainties.Then for the counteraction of the mismatched disturbances and uncertainties,a nonlinear disturbance observer is also developed.The trajectory tracking performance experiments and bandwidth analysis were conducted on experimental setup with the proposed control method.It is proved that the adaptive integral sliding mode controller has a high tracking performance and bandwidth especially for the axial vibration characteristics model of ball screw drives.And the ball screw tracking accuracy also has a considerable improvement with the application of the proposed nonlinear disturbance observer.

Extended state observer-based finite-time adaptive sliding mode control for wheeled mobile robot

In this paper,an Improved Extended State Observer-based Finite-Time adaptive sliding mode control,is investigated for trajectory tracking control of a wheeled mobile robot.First,a novel finite-time adaptive sliding mode control,based on the fractional power of the sliding surface,is developed to deal with the chattering problem.Moreover,this strategy improves the conver-gence rate by adjusting online the switching part in sliding mode control.Second,an improved Non-linear ESO is employed to reconstruct and compensate for the unknown disturbances.To complete the trajectory tracking control,the kinematic algorithm is in troduced.Theoretically,the proposed control scheme converges within finite-time thanks to the Lyapunov method.Finally,numerical simulations show the efficiency of the designed controller.

基于ADE优化的IPMSM全速域无传感器控制

为了实现内置式永磁同步电机(IPMSM)全速域的无传感器控制和切换速域的平滑过渡,提出了一种基于自适应差分进化(ADE)算法优化的复合控制方法。分别在零低速域、中高速域采用旋转高频电压注入法和滑模观测器法来对电机转速和转子位置进行估算,并在切换速域采用基于ADE算法的权重系数优化法来实现上述两种控制方法的平滑切换,从而实现IPMSM全速域无传感器控制。仿真结果表明:提出的复合控制方法能够实现电机全速域的无感控制和切换速域的平滑过渡,且具有良好的稳定性。

基于新型自适应滑模观测器的PMSM无传感器控制

为了实现无位置传感器控制策略在永磁同步电机中的应用,在传统滑模观测器的基础上提出了一种改进型的自适应滑模观测器算法。提出的改进型自适应滑模观测器中使用更平滑的sigmoid函数取代了传统的符号函数,并结合反电动势的自适应律有效地减少了提取的反电动势中包含的高频分量,避免了低通滤波器在使用过程中带来的抖振和相位延迟现象。最后反电动势中包含的转子位置信息与速度信息通过锁相环提取。为了验证模型的可行性,基于MATLAB/Simulink搭建了仿真模型进行了仿真分析,并以TMS320F28377芯片为核心搭建了永磁同步电机硬件实验平台进行实验验证,仿真与实验结果验证了该方法的有效性和实用性。

一种新型永磁同步电机高阶滑模控制算法

针对永磁同步电机控制系统易因外部扰动等不确定性影响而导致控制性能下降的问题,提出了一种基于改进自适应非奇异终端滑模控制器和滑模扰动观测器补偿技术的复合控制算法。选择新型自适应指数趋近律设计非奇异终端滑模转速环控制器,新型趋近律可以在保证减少抖振的同时保证控制系统能够快速收敛,可动态适应被控系统的变化;利用扩展滑模扰动观测器实时估计系统中不确定性参数,并对控制器进行前馈补偿,且通过Lyapunov函数证明了其稳定性。仿真和试验结果表明,与PI控制、传统滑模控制方法相比,所提方法有效改善了抖振问题,提高了控制系统对电机的控制精度,提升了系统的鲁棒性和抗干扰性能。

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。

基于扰动观测器和改进自适应二阶快速终端滑模的PMLSM伺服系统控制

针对永磁直线同步电动机(PMLSM)在运行时易受到摩擦力、负载扰动及环境变化等不确定影响,设计一种基于扰动观测器和自适应二阶快速终端滑模控制方法。首先,该方法在高阶滑模的基础上结合了快速终端滑模控制,有效加快了系统响应速度。其次,在二阶滑模面的基础上引入条件积分项,该项仅作用于边界层内部,能够有效避免滑模到达阶段由于积分饱和现象导致的超调量过大及响应时间过慢的问题。此外,设计自适应切换控制律,使切换增益在合理的区间内,并根据系统状态进行实时更新,从而削弱抖振现象。最后,为进一步提升系统的鲁棒性,采用扰动观测器对PMLSM系统的集总不确定性进行补偿。经实验验证,该控制方法具有良好的位置跟踪精度和强鲁棒性,且对系统抖振现象有明显削弱作用。

具有低开关频率的感应电机无传感器控制

着眼于传统低开关频率控制方法对无感磁链观测带来不利影响的问题,提出了一种具有低开关频率的感应电机无传感器控制方法.使用速度自适应滑模观测器与预测控制方法相结合,构成感应电机无传感器预测控制系统.其可以在较高采样频率下,有效降低开关频率,并保证系统具有较高的动态特性.同时,滑模思想的引入使观测器具有较强的鲁棒性.实验结果表明,所提出的低开关频率无传感器控制策略具有较高的控制精度和较强的抗干扰性能,研究的自适应滑模观测器在稳态和动态实验中均具有良好的观测精度,其中电流环响应时间可以达到1.52 ms,可以实现75 r·min^(–1)及以上转速范围内的稳定观测及运行,且系统最高平均开关频率保持在500 Hz上下,为较低的水平.

基于扰动观测器的PMSM系统自适应反步滑模控制

针对负载转矩波动和系统参数变化的永磁同步电机(PMSM)系统的控制问题,提出了一种带有非线性扰动观测器的自适应反步滑模位置跟踪控制方法。首先,设计了自适应反步滑模控制器,以确保电机位置快速收敛到期望值,并设计了自适应收敛增益,以减小电机位置响应下的大的过冲;其次,设计非线性扰动观测器估计未知扰动,并为自适应反步滑模控制提供前馈补偿,以提高系统的鲁棒性,并减少稳态位置误差。仿真结果表明,该方法可以有效减少过冲,很好地实现了PMSM系统的快速位置跟踪控制,具有良好的抗扰动性能。

协作机械臂碰撞环境下的安全控制

针对人机协作过程中机械臂末端与操作者之间可能存在物理碰撞的问题,本文提出一种基于自适应导纳和滑模控制的机械臂安全控制方法.首先,采用基于广义动量的干扰观测器估计机械臂各关节和末端执行器上的干扰力.然后,设计一个双环控制结构,内环是基于干扰观测的双幂次趋近律滑模轨迹跟踪控制器,用以克服外界干扰的影响,达到期望的轨迹跟踪精度;外环是自适应导纳控制器,依据碰撞外力的大小和方向更新期望轨迹,以保证机械臂碰撞发生时的柔顺性和碰撞解除后迅速恢复工作状态的能力.最后,对所提算法进行仿真和实验验证.实验结果表明,协作机械臂碰撞环境下的安全控制算法能保证人机协作的安全性和机械臂工作的连续性,满足人机协作过程中的工作需求.

基于自适应滑模观测器的氢燃料电池空气供应系统泄露故障容错控制

空气泄漏是质子交换膜燃料电池(proton exchange membrane fuel cell,PEMFC)系统中常出现的一类故障,并且发生概率会随着系统运行时间的增加而逐渐增大,直接影响PEMFC的性能。为此,提出基于自适应滑模观测器(adaptive slide mode observer,ASMO)的容错控制策略。首先采用观测器实现泄露故障下流量重构,通过主动容错控制器调节空压机的供给流量,补偿泄漏的空气流量。同时,设计一种背压阀开度的迭代调节算法用于控制供气压力,保证稳定、合适空气供应,避免电堆出现“氧饥饿”现象。最后,基于模型在环平台对观测器以及容错控制策略进行验证与分析,结果表明:ASMO拥有比传统滑模观测器更好的收敛速度和估计精度;采用基于ASMO的容错控制策略后,系统能够在故障后恢复正常的空气供应,提高了系统整体可靠性。