Sliding mode control of quadruple tank process

The process investigated herein is the quadruple tank system that is stable only within a limited zone of operating parameters. The process model has been developed from fundamentals and tuned with experimental data. A controller design based on feedback linearization has been tested on this process model. Coupling feedback linearization with sliding mode algorithm provides robust control of the process and performs far superior to conventional PI control. A PC based controller interfaced to the experimental quadruple tank experimental set up has been used to implement this algorithm and test its performance. Inserting a ‘boundary layer’ around the sliding surface reduced the ‘chattering’ associated with sliding mode control. The implemented controller provides robust control and excellent set point tracking.     

Sliding mode control design principles and applications to electricdrives

The basic concepts, mathematics, and design aspects of variable-structure systems as well as those with sliding modes as a principle operation mode are treated. The main arguments in favor of sliding-mode control are order reduction, decoupling design procedure, disturbance rejection, insensitivity to parameter variations, and simple implementation by means of power converters. The control algorithms and data processing used in variable structure systems are analyzed. The potential of sliding mode control methodology is demonstrated for versatility of electric drives and functional goals of control     

Sliding mode control with time-varying hyperplane for AMB systems

Deals with sliding mode hyperplane design for a class of linear parameter-varying (LPV) plants, the state-space matrices of which are an affine function of time varying physical parameters. The proposed hyperplane, involving a linear matrix inequality (LMI) approach, has continuous dynamics due to scheduling parameters and provides stability and robustness against parametric uncertainties. We have designed a time-varying hyperplane for a rotor-magnetic bearing system with a gyroscopic effect, which can be considered an LPV plant due to parameter dependence on rotational speed. The obtained hyperplane is continuously scheduled with respect to rotational speed. We successfully carried out experiments using a commercially available turbomolecular pump system and results were reasonable and good     

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.     

Sliding mode multilevel control for improved performances in powerconditioning systems

A novel control technique has been devised to obtain high dynamics responses from a multilevel power conditioning converter. The theory of variable structure control systems with sliding mode has been followed, taking into account several problems that may be encountered in space environments. The analytical study made provides general tools to design AC power conditioning systems for any application. The new control scheme, its mathematical analysis and digital simulation results relevant to a 115 V/400 Hz AC power system are presented and discussed     

时变扰动下的永磁同步电机滑模控制

时变扰动环境下,永磁同步电机(PMSM)采用鲁棒性较好的滑模控制.根据滑模控制中传统指数趋近律,提出一种改进型的趋近律,并基于改进型趋近律设计了一种PMSM调速系统的滑模速度控制器,提高电机的运行性能.通过仿真结果对比分析,设计的基于改进型趋近律的滑模速度控制器不仅可以提高系统的动态性能,而且削弱了系统的抖振现象,使电...     

具有输入饱和的光电伺服平台的滑模控制

为了解决光电伺服平台中的输入饱和问题，采用了基于过渡过程的滑模控制算法。过渡过程算法是基于时间最优理论设计的，将跳变的输入信号变为一个缓慢上升的信号，使系统的初始跟踪误差减小，从而避免了输入饱和现象，提高了系统的稳定性。结果表明，该方法可以有效消除输入饱和现象，适用于光电伺服平台的目标跟踪，具有重要研究与应用价值。     

Sliding mode closed-loop control of FES: controlling the shank movement

Functional electrical stimulation (FES) enables restoration of movement in individuals with spinal cord injury. FES-based devices use electric current pulses to stimulate and excite the intact peripheral nerves. They produce muscle contractions, generate joint torques, and thus, joint movements. Since the underlying neuromuscular-skeletal system is highly nonlinear and time-varying, feedback control is necessary for accurate control of the generated movement. However, classical feedback/closed-loop control algorithms have so far failed to provide satisfactory performance and were not able to guarantee stability of the closed-loop system. Because of this, only open-loop controlled FES devices are in clinical use in spite of their limitations. The purpose of the reported research was to design a novel closed-loop FES controller that achieves good tracking performance and guarantees closed-loop stability. Such a controller was designed based on a mathematical neuromuscular-skeletal model and is founded on a sliding mode control theory. The controller was used to control shank movement and was tested in computer simulations as well as in actual experiments on healthy and spinal cord injured subjects. It demonstrated good robustness, stability, and tracking performance properties.     

Sliding mode input-output linearization and field orientation forreal-time control of induction motors

This paper deals with real-time control of an induction motor based on a digital signal processor (DSP) TMS320C31/40-MHz-based system. A sliding mode controller (SMC) is presented and compared with the well-known field orientation and input-output linearization techniques. To estimate the rotor flux, a sliding mode observer is used. Experimental results are given to highlight the performances and disadvantages of these methods with respect to rotor resistance variations     

Technical note Sliding mode control for a class of hydraulic position servo

The present paper discusses a sliding mode control method suitable for controlling a hydraulic position servo with a flexible load. Due to the requirements of the control system, the reference model is designed for the case of a flexible load. The core of sliding mode control is switching surfaces which are specially defined for the system according to the mathematical model and control goal. A novel algorithm is developed, and the simulated and experimental results of the control system are shown. The results show the extremely good robustness of the proposed method.     

新型混联机构结合扰动观测器的滑模控制

针对一种新型混联式汽车电泳涂装输送机构,考虑其在实际控制中存在建模误差、参数不确定性、摩擦力和外部未知干扰,为削弱其对系统产生的不利影响,提高输送机构的控制性能,提出一种结合扰动观测器的滑模控制策略。运用Lyapunov稳定性理论证明了所提出控制算法的稳定性,并对滑模控制和结合扰动观测器的滑模控制进行MATLAB仿真比较。     

Sliding mode based powertrain control for efficiency improvement in series hybrid-electric vehicles

This study involves the improvement of overall efficiency in series hybrid-electric vehicles (SHEVs) by restricting the operation of the engine to the optimal efficiency region, using a control strategy based on two chattering-free sliding mode controllers (SMCs). One of the designed SMCs performs engine speed control, while the other controls the engine/generator torque, together achieving the engine operation in the optimal efficiency region of the torque-speed curve. The control strategy is designed for application on a SHEV converted from a standard high mobility multipurpose wheeled vehicle (HMMWV) and simulated by using the Matlab-based PNGV Systems Analysis Toolkit (PSAT). The performance of the control strategy is compared with that of the original PSAT model, which utilizes PI controllers, a feedforward term for the engine torque, and comprehensive maps for the engine, generator and power converter (static only), which constitute the auxiliary power unit (APU). In this study, in spite of the simple modeling approach taken to model the APU and the optimal efficiency region, an improved performance has been achieved with the new SMC based strategy in terms of overall efficiency, engine efficiency, fuel economy, and emissions. The control strategy developed in this work is the first known application of SMC to SHEVs, and offers a simple, effective and modular approach to problems related to SHEVs.     

一种单连杆机械臂柔性关节的滑模变结构控制

研究一种带柔性关节的单连杆机械臂的跟踪控制问题,其中体现关节柔性的是连接单连杆机械臂和驱动电机的两个仿腱线弹簧。利用Lagrange方程导出跟踪控制问题的数学模型,引进滑模变结构控制技术,给出Hurwitz多项式的确定以及滑模控制器的设计方法,并讨论Hurwitz多项式的根对控制效果的影响。将滑模控制器的表示式代入跟踪控制问题的数学模型中,得到状态变量的非线性微分方程组,利用Matlab进行仿真,得到了理想的控制输出效果。     

Sliding mode control with closed-loop filtering architecture for a class of nonlinear systems

It is well known by equivalent control theory, that in the sliding mode a low-pass filter, working as an average operator, can capture the desired control fairly well from the switching control signals. However, directly adding the filtered signals in parallel with the switching control does not warrant any improvement in the control system performance. In this work, we make clear the underlying reason why the sliding mode control (SMC) system does not function properly with such a simple closed-loop filtering structure. The correct way of incorporating the closed-loop filtering into SMC requires a second low-pass filter, which works concurrently with the first low pass filter to scale down the gain of the switching control. The SMC system with the new closed-loop filtering is able to realize the acquisition of equivalent control or estimate the disturbance, effectively reduce the switching gain to the minimum level, and as a result to eliminate chattering. Complementary to existing SMC, the proposed control system can easily incorporate feed-forward control into the closed-loop for bounded system perturbations. In addition, the frequency-domain knowledge can be easily used to construct the two filters.     

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.     

Sliding mode based harmonic oscillator synchronization

This paper deals with the synchronization problem of harmonic oscillatory systems, such as two- and three-phase harmonic oscillators. Synchronization between referent and controlled harmonic oscillators, based on amplitude and phase control, is pursued by employing a variable structure control system. Synchronization is achieved by organizing sliding mode along the intersection of two appropriate nonlinear sliding surfaces, individually providing amplitude and phase identity. In case of three-phase harmonic oscillator synchronization an additional symmetry condition arises, which is handled by introduction of another sliding surface. Parameter perturbations and external disturbances are taken into consideration in control system design. Variable structure controllers for two- and three-phase synchronization are designed, which provide sliding mode along the intersection of sliding surfaces in finite time in spite of present disturbances. Ideal sliding dynamics is proved to be insensitive to internal and external disturbances resulting in an ideal harmonic response. Mathematical analysis as well as experimental and simulation results are presented.     

Sliding mode controller by use of neural networks

This paper proposes a method to design a robust controller by use of a neural network. The trained neural network functions as a sliding mode controller which is robust against uncertainties. From the analysis of the neural network, it is proved that the switching surface is not the same as the sliding surface like conventional sliding mode control theory. The neural network shows that the switching surface should be a nonlinear surface because of a hard limitation on control inputs, even if the designed sliding surface is linear. From the result of estimating the robustness of neural networks, we propose that generalization of neural networks which are used as controllers should be measured by the robustness. Numerical simulations show that the controller is robust against uncertainties and robustness can be improved by the proposed method.     

模糊滑模变结构控制技术的应用研究

针对包含非线性和不确定性的坦克炮控系统,提出了一种基于模糊控制的滑模变结构控制器的设计方法。首先采用极点配置的方法确定了等效控制,再通过应用带有切换增益的鲁棒反馈控制来保证滑模到达条件,然后,利用模糊调节策略来加速到达滑动模态区并削弱抖振。本文所提出的模糊逻辑的应用是一种可计算的智能方法,针对工程问题,具有精确表达式的调整过程,使得控制策略的调整变得更加容易实现。通过仿真结果可以看出,系统得到了更好的性能指标,并且削弱了抖振。系统响应的快速性和鲁棒性都得到了提高。     

Sliding mode control combined with extended state observer for an ankle exoskeleton driven by electrical motor

A novel sliding mode control combined with extended state observer (ESO) is proposed for an ankle exoskeleton driven by electrical motor. During the process of assisting, it is necessary to design an effective controller for assisting torque of ankle exoskeleton. However, the parameter uncertainty of complex dynamics model and the irregular motion of human ankle may affect the torque control accuracy. For a high control precision of assisting torque when facing the modeling uncertainty, the sliding mode control is employed, but a large switching gain is usually needed in order to suppress the disturbance, which cause the control signal vibrate greatly. ESO can observe and suppress the disturbance and modeling uncertainty, but its tracking performance needs to be improved. Therefore, the proposed complex controller takes the advantages of sliding mode control and extended state observer, which can not only improve torque tracking performance but also overcome the disturbance force caused by the change of human joint angle without increasing chattering of control signal. Experimental studies are carried out to validate the effectiveness of the proposed control. The results show the presented controller have better torque tracking performance and robustness stability, and the proposed controller can reduce the chattering compared with the tradition sliding mode control.     

Sliding mode audio class-D amplifier for portable devices

Audio class-D amplifiers are widely used in industrial and consumer portable electronic devices, such as mobile phones, thanks to their high efficiency. However, these amplifiers have a limited linearity due to their switching behavior and also a limited control bandwidth. To overcome these major drawbacks, this paper introduces a self-oscillating control technique based on the sliding mode theory which combines a large control bandwidth and a spread spectrum technique. A high power supply rejection, which is a crucial parameter in modules directly connected to a noisy battery, has also been achieved by introducing a variable hysteresis window. Theoretical analysis, behavioral and electrical simulations are discussed in detail in this paper. An integrated circuit using 0.13 μm CMOS process has been realized focused on mobile phone applications (0.8 W, 3.6 V and 8 Ω). The audio amplifier achieves 97 dB(A) signal-to-noise ratio, 0.02 % harmonic distortion and up to 80 dB of power supply rejection. The die area is smaller than 0.4 mm² while keeping more than 90 % efficiency at 1 W.