Sliding mode control and stability analysis of buck DC-DC converter

This paper is proposed to deal with the voltage regulation of buck DC-DC converter based on sliding mode control (SMC) technology. A buck DC-DC converter with parasitic resistance is inherently a bilinear system possessing inevitable uncertainties, such as variable resistive load and input disturbance. First, the buck DC-DC converter is modified into an uncertain linear model. Then, SMC technology is adopted to suppress the input disturbance and reduce the effects from the load variation. In addition, the continuous conduction mode (CCM) for normal operation can be guaranteed by the design of sliding function. Finally, experimental results are included for demonstration.     

Modeling,control and experimental investigation of horizontal hydraulic flight motion simulator

The horizontal hydraulic flight motion simulator (HHFMS) is widely applied in the hardware-in-the-loop (HWIL) simulation of the aircraft attitude attributing to high dynamic response and large power density when a heavy load is tested. In order to achieve a high-precision control performance of the HHFMS, some serious mismatched uncertainties consisting of nonlinear friction torque, unbalanced gravity torque, inertia variation and unmodeled dynamics have to be taken into account. In particular, gravity torque, as an asymmetrical load, will degrade the control performance at the starting moment. In this paper, via transforming mismatched uncertainties into matched uncertainties as a unified disturbance, a cascaded model was firstly established, which can not only avoid designing the complex virtual control laws but also help indirectly reduce the asymmetrical effect of gravity torque. Then, a linear extended state observer (LESO) based continuous sliding mode control (SMC) was proposed. LESO is expected to realize a good suppression of disturbance, as well as convenient acquisition of states signals such as velocity and acceleration. In addition to ensuring the control accuracy and the robustness, continuous SMC without sign function also frees from worrying about possible chattering. Moreover, a setting criterion of two parameters that satisfy Hurwitz's Condition in the third-order SMC was also provided. Finally, experimental investigation shows the effectiveness of dynamic modeling and the practicability of the proposed control method.     

Leader‐Following Formation Control of Multiple Robots with Uncertainties through Sliding Mode and Nonlinear Disturbance Observer

This paper presents a control scheme for the leader‐following formation of multiple robots. The control scheme combines the sliding mode control (SMC) method with the nonlinear disturbance observer (NDOB) technique. The formation dynamics suffer from uncertainties because the individual robots are uncertain. Concerning such formation uncertainties, the leader‐following formation dynamics are modeled. Assuming that the formation uncertainties have an unknown boundary, an NDOB‐based observer was designed to estimate the formation uncertainties. A sliding surface containing the observer outputs has been defined. Regarding the sliding surface, an SMC‐based controller was investigated to form uncertain robots. A sufficient condition in the sense of the Lyapunov theory was proven such that the formation system is asymptotically stable. Herein, some comparison results between the sole SMC method and the second‐order SMC method are presented to demonstrate the effectiveness and feasibility of the control scheme for multiple robots in the presence of uncertainties.     

High-Gain Observers With Sliding Mode for State and Unknown Input Estimations

To handle the state estimation of a nonlinear system perturbed by a scalar disturbance distributed by a known nonlinear vector, a sliding-mode term is incorporated into the nonlinear high-gain observer (HGO) to realize a robust HGO. By imposing a structural assumption on the unknown input distribution vector, the observability of the disturbance with respect to the output is safeguarded, and the disturbance can be estimated from the sliding surface. Under a Lipschitz condition for the nonlinear part, the nonlinear observers are designed under the structural assumption that the system is observable with respect to any input. In the sliding mode, the disturbance under an equivalent control becomes an increment of Lipschitzian function, and the convergence of the estimation error dynamics can be proven similar to the analysis of HGOs. The proposed technique can be applied for fault detection and isolation. The simulation results for the bioreactor application demonstrate the effectiveness of the proposed method.      

A new controller for boost dc–dc converters based on a novel sliding surface

ABSTRACT

In this paper, two control schemes for boost converters affected by uncertainties in input voltage and load are proposed. The boost converter dynamics is redefined in terms of new state variables to facilitate the use of a disturbance observer that can estimate matched and unmatched disturbances. A sliding surface, which is new in the context of boost converters, is proposed to enable tracking and regulation of output voltage without requiring measurement of input voltage and load current. The stability of the overall system including the disturbance observer, the sliding variable and the output is proved. The performance of the schemes is assessed for regulation of output voltage and tracking of reference voltage by simulation as well as experimentation in which various types of uncertainties and various types of reference voltages are considered.     

具有攻击角约束的无抖振滑模导引律设计

为了提高拦截器弹头的杀伤力,带攻击角度约束的导引律一直是学术界研究的热点。因此,制导律的设计既要保证较小的脱靶量又要保证以相应的攻击角度打击目标,目前已有很多的控制方法应用在拦截器制导设计中,包括最优制导律,滑模制导律,PN制导律,等等。我们知道滑模控制方法对外界扰动和参数不确定性有较好的鲁棒性,但是滑模控制的抖振缺陷普遍存在于传统的线性滑模和终端滑模中。因此,本文提出了一种新的无抖振终端滑模控制方法用于制导律的设计中,该方法不仅对外界有界扰动有较好的鲁棒性,还有效的消除了抖振的产生。最后数字仿真验证了该方法的有效性。     

Shifted Switching Plane Design for Third-Order Systems with Elastic and Conventional Input Constraints

In this paper a new sliding mode control algorithm for a third-order uncertain, nonlinear, and time-varying dynamic system subject to unknown disturbance and input constraint is proposed. The algorithm employs a time-varying switching plane. At the initial time t = t₀, this plane passes through the point determined by the system initial conditions in the error state space. Afterwards, the switching plane moves with a constant velocity to the origin of the space. In order to select the switching plane parameters, the integral of the time multiplied by the absolute error is minimised. Two types of input signal constraints are considered. First a conventional constraint expressed by an inequality is analysed, and then an elastic (or stretchable) constraint is taken into account. In the second case, we assume that the threshold value of the system input signal is known and that exceeding this value is undesirable, however not definitely forbidden. Exceeding this value is acceptable if it leads to an essential improvement of the system performance. In both cases the switching plane is chosen in such a way that the reaching phase is eliminated, insensitivity of the system to the external disturbance and the model uncertainty is guaranteed from the very beginning of the proposed control action, and fast, monotonic error convergence to zero is achieved.     

PID-type sliding mode-based adaptive motion control of a 2-DOF piezoelectric ultrasonic motor driven stage

This paper presents a new scheme of adaptive sliding mode control (ASMC) for a piezoelectric ultrasonic motor driven X–Y stage to meet the demand of precision motion tracking while addressing the problems of unknown nonlinear friction and model uncertainties. The system model with Coulomb friction and unilateral coupling effect is first investigated. Then the controller is designed with adaptive laws synthesized to obtain the unknown model parameters for handling parametric uncertainties and offsetting friction force. The robust control term acts as a high gain feedback control to make the output track the desired trajectory fast for guaranteed robust performance. Based on a PID-type sliding mode, the control scheme has a simple structure to be implemented and the control parameters can be easily tuned. Theoretical stability analysis of the proposed novel ASMC is accomplished using a Lyapunov framework. Furthermore, the proposed control scheme is applied to an X–Y stage and the results prove that the proposed control method is effective in achieving excellent tracking performance.     

基于反步滑模控制的TCP网络的主动队列管理

针对TCP网络的拥塞问题,考虑到网络本身存在参数不确定因素和非响应流的干扰,基于反步滑模控制提出了一种主动队列管理算法。在总的不确定的界已知而且不必很小的情况下,设计了一种反步滑模控制器来补偿系统不确定所带来的影响。仿真结果表明,该方法对TCP网络的复杂变化具有较好的鲁棒性和较快的系统响应。     

基于模型参考的直线伺服系统离散滑模控制

针对永磁直线同步电机伺服系统存在的诸多不确定性问题,设计了模型参考离散滑模（MRDSMC）位置跟踪控制器。将伺服问题转化为调节问题,为了保证跟踪的快速性,在传统DSMC滑模面的基础上,引入遗忘因子。并采用一步延迟扰动近似来补偿未知扰动。此外,为了抑制由高频未建模动态引起的抖振,在MRDSMC设计中加入低通滤波器。仿真结果表明,该方案能有效地抑制系统未建模动特性的影响,具有很强的鲁棒跟踪性能。     

Sliding mode control for an active magnetic bearing system subject to base motion

This paper describes the application of an active magnetic bearing (AMB) system to levitate the elevation axis of an electro-optical sight mounted on a moving vehicle. In this type of system, it is desirable to retain the elevation axis in an air–gap between magnetic bearing stators while the vehicle is moving. A sliding mode control is applied to increase robustness to model uncertainties and to reduce disturbance responses. To ensure the authority of sliding mode control, model parameter uncertainties of AMB systems are analysed and reachability to sliding surface has been verified. The sliding surfaces are designed such that the poles of the closed-loop system locate at desired locations. The proposed control is applied to a 2-DOF active magnetic bearing system subject to base motion. The feasibility of the proposed technique is verified with experimental results.     

改进型滑模扰动观测器的感应电机控制系统

针对传统PI调节器在负载剧烈突变时控制性能不佳及使用传统滑模观测器抖振严重的问题,文中以感应电机为研究对象,提出了一种基于滑模观测器和传统PI调节器的扰动实时补偿方案。通过改进型的扰动观测器对系统扰动进行实时观测估算,将估算出的扰动反馈至PI调节器进行前馈补偿,从而有效提高电机控制性能,改善抖振现象。文中搭建了基于MATLAB的仿真平台和TMS320F28335 DSP的实验平台,对所研究的改进滑模观测器扰动前馈补偿方法与常规单PI调节、常规滑模观测器扰动补偿进行了对比分析。该结果验证了所提方案的有效性与可行性,速度超调量优化了0.5%,响应时间为30 ms。     

Robust H �� Filtering for Uncertain Nonlinear Stochastic Systems with Mode-dependent Time-delays and Markovian Jump Parameters

This paper investigates the problem of robust H _∞ filtering for a class of uncertain nonlinear stochastic time-delay systems with Markovian jump parameters. The system under consideration contains parameter uncertainties, It?-type stochastic disturbances, unknown nonlinearities as well as time-varying delays, which vary in a range and dependent on the mode of the operation. We aim to design a full-order Markovian jump filter such that, for all admissible uncertainties, the filtering error system is robustly asymptotically stable in the mean square, and a prescribed H _∞ disturbance attenuation level is guaranteed. By using the Lyapunov stability theory and It? differential rule, some sufficient conditions in terms of linear matrix inequality (LMI) are proposed to guarantee the existence of the desired H _∞ filter. Then, the explicit expressions of the desired filter parameters are given. Illustrative examples are provided to demonstrate the effectiveness and applicability of the proposed method.     

Adaptive Fuzzy Sliding Mode Control Algorithm for a Non-Affine Nonlinear System

This paper concerns the design of robust controller for a nonlinear system that can be represented or approximated in a non-affine form. The control algorithm is based on sliding mode control that incorporates a fuzzy tuning technique, and it superposes equivalent control, switching control, and fuzzy control. An equivalent control law is firstly designed based on a nominal system model that was obtained by using curve fitting techniques under MATLAB. Switching control is then added to guarantee that the state reaches the sliding surface in the presence of parameter and disturbance uncertainties. Also, fuzzy tuning schemes, which can be supported by learning techniques derived from neural networks, are employed to improve control performance and to reduce chattering in the sliding mode. To verify the performance of this controller, an experimental platform of a pneumatically actuated top-guided single-seated control valve, which belongs to a classical complex nonlinear system, was constructed. Also, the experimental results show that high performance and attenuated chatter are achieved and thus verify the validity of the proposed control approach to dynamic systems characterized by severe uncertainties.     

参数未知的时延混沌系统滑模变结构同步控制

将滑模控制策略用于时延混沌系统的同步,采用了对系统参数摄动鲁棒性好的变结构控制,使系统对噪声和参数失配情况具有更强的鲁棒性。同时将自适应技术、系统辨识技术应用于系统中的未知参数逐步逼近,实现具有扰动以及参数未知的时延混沌系统的同步。仿真结果证实了该方法的有效性。     

Adaptive incremental sliding mode control for a robot manipulator

An adaptive incremental sliding mode control (AISMC) scheme for a robot manipulator is presented in this paper. Firstly, an incremental backstepping (IBS) controller is designed using time-delay estimation (TDE) to reduce dependence on the mathematical model. After substituting IBS controller into the nonlinear system, a linear system w.r.t. tracking errors is obtained while TDE error is the disturbance. Then, the AISMC scheme, including a nominal controller and an SMC, is developed for the resulted linear system to improve control performance. According to the equivalent control method, the SMC in the AISMC scheme is to handle TDE error. To receive optimal control performance at the sliding manifold, an LQR controller is selected as the nominal controller. The SMC is designed based on positive semi-definite barrier function (PSDBF) since it prevents switching gains from being over/under-estimated, and two practical problems are addressed in this paper: A new PSDBF is designed and conservative (large) setting bounds affecting tracking precision and/or system stability are avoided; An improved PSDBF based SMC is developed where the PSDBF and an adaptive parameter are used simultaneously to regulate switching gains, and the system is still stable when sliding variable occasionally exceeds the predefined vicinity. Moreover, finite-time convergence property of the sliding variable is strictly analyzed. Finally, real-time experiments are conducted to verify the effectiveness of the proposed control method.     

Digital Controller Design for Analog Systems Represented by Multiple Input–Output Time-Delay Transfer Function Matrices with Long Time Delays

This paper presents a digital controller design methodology for multivariable analog systems represented by minimally realizable multiple input–output time-delay transfer function matrices with long time delays. First, the analog transfer function matrix with multiple input–output time delays is minimally realized and represented by a delay-free state-space model and a multiple output-delay function. For a specific multiple time-delay transfer function matrix with complex poles, a minimal realization scheme is newly proposed. Then the minimized delay-free state-space model is utilized for linear quadratic regulator (LQR) design. Furthermore, the designed analog LQR is digitally redesigned via a predictive state-matching method for finding a low-gain digital controller from the pre-designed high-gain analog controller. For implementation of the digitally redesigned controller, a digital observer is constructed for the multiple time-delay system with long time delays. An illustrative example is given to demonstrate the effectiveness of the proposed method.     

Sliding Mode Observer-Based Fault Detection of Distributed Networked Control Systems with Time Delay

This paper considers the fault detection problem of distributed networked control systems (DNCS) with time delay. A sliding mode observer-based fault detection method for a two-level DNCS is presented and two different situations are considered. When all the states of the system are available for measurement, we convert the fault detection problem to a sliding motion stable and reachable problem. When some states of system are not available for measurement, we design a transformation matrix to separate the measurable states and the unknown states, and then different sliding mode observers for those unknown states are developed to achieve fault detection. Finally, a numerical example is provided to illustrate the effectiveness of the proposed method with simulation results.     

Fuzzy sliding-mode controllers with applications

This paper concerns the design of robust control systems using sliding-mode control that incorporates a fuzzy tuning technique. The control law superposes equivalent control, switching control, and fuzzy control. An equivalent control law is first designed using pole placement. Switching control is then added to guarantee that the state reaches the sliding mode in the presence of parameter and disturbance uncertainties. Fuzzy tuning schemes are employed to improve control performance and to reduce chattering in the sliding mode. The practical application of fuzzy logic is proposed here as a computational-intelligence approach to engineering problems associated with sliding-mode controllers. The proposed method can have a number of industrial applications including the joint control of a hydraulically actuated mini-excavator as presented in this paper. The control hardware is described together with simulated and experimental results. High performance and attenuated chatter are achieved. The results obtained verify the validity of the proposed control approach to dynamic systems characterized by severe uncertainties