Sliding-mode observers for systems with unknown inputs and measurement disturbances

The method to design sliding-mode observers for systems with unknown inputs and measurement disturbances is presented in the paper. An augmented system is constructed by viewing the measurement disturbances as unknow inputs. For such an augmented system, the so-called observer matching condition is not satisfied. Based on the construction of auxiliary outputs, the observer matching condition may be satisfied. High-order sliding-mode differentiators are developed to obtain the estimates of those unmeasurable variables contained in the auxiliary output vector. Employing the estimate of auxiliary output vector, a sliding-mode observer is designed. The simulation results to a real model show that the proposed method is effective.

Sliding-mode control of path following for underactuated ships based on high gain observer

A nonlinear robust control strategy is proposed to force an underactuated surface ship to follow a predefined path with uncertain environmental disturbance and parameters.In the controller design,a high-gain observer is used to estimate velocities,thus only position and yaw angle measurements are required.The control problem of underactuated system is transformed into a control of fully actuated system through adopting an improved line-of-sight(LOS) guidance law.A sliding-mode controller is designed to eliminate the yaw angle error,and provide the control system robustness.The control law is proved semi-globally exponentially stable(SGES) by applying Lyapunov stability theory,and numerical simulation using real data of a monohull ship illustrates the effectiveness and robustness of the proposed methodology.

Sliding Mode Control Approach with Integrated Disturbance Observer for PMSM Speed System

The research on high-performance vector control of permanent magnet synchronous motor(PMSM)drive system plays an extremely important role in electrical drive system.To further improve the speed control performance of the system,a fast non-singular end sliding mode(FNTSM)surface function based on traditional NTSM control is developed.The theoretical analysis proves that the FNTSM surface function has a faster dynamic response and more finite-time convergence.In addition,for the self-vibration problem caused by high sliding mode switching gain,an FNTSM control method with anti-disturbance capability was designed based on the linear disturbance observer(DO),i.e.the FNTSMDO method was employed to devise the PMSM speed regulator.The comparative simulation and experiment results with traditional PI control and NTSM control methods indicate that the FNTSMDO method could improve the dynamic performance and anti-interference of the system.

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.

Model predictive current control for PMSM driven by three-level inverter based on fractional sliding mode speed observer

Based on the fractional order theory and sliding mode control theory,a model prediction current control(MPCC)strategy based on fractional observer is proposed for the permanent magnet synchronous motor(PMSM)driven by three-level inverter.Compared with the traditional sliding mode speed observer,the observer is very simple and eases to implement.Moreover,the observer reduces the ripple of the motor speed in high frequency range in an efficient way.To reduce the stator current ripple and improve the control performance of the torque and speed,the MPCC strategy is put forward,which can make PMSM MPCC system have better control performance,stronger robustness and good dynamic performance.The simulation results validate the feasibility and effectiveness of the proposed scheme.

Preliminary Study on the Differences between Automatic-observed and Manual-observed Wind Speed and Its Correction

Comparing and analyzing the difference between automatic-observed and manual-observed wind speed based on the wind speed parallel observations in two methods, we find that many elements can influence the difference between automatic-observed and manual-observed wind speed, including the levels of speed wind, observation instruments and different regions. According to these elements, correction has been conducted, and find that the correction according to the level of wind speed has the best correction effect.

Unsteady Behavior of Cavitating Waterjet in an Axisymmetric Convergent-Divergent Nozzle: High Speed Observation and Image Analysis Based on Frame Difference Method

Although it is well known that cloud cavitation shows unsteady behavior with the growing motion of an attached cavity, the shedding motion of a cloud, the collapsing motion of the cloud shed downstream and a reentrant motion in flow fields such as on a 2-D hydrofoil and in a convergent- divergent channel with a rectangular cross-section, observations for the periodic behavior of cloud cavitation in a cylindrical nozzle with a convergent-divergent part, which is mainly used in an industrial field, have hardly been conducted. From engineering viewpoints, it is important to elucidate the mechanism of periodic cavitation behavior in a cylindrical nozzle. In this study, a high-speed observation technique with an image analysis technique was applied to the cloud cavitation behavior in the nozzle to make clear the mechanism of unsteady behavior. As a result, it was observed in the nozzle that the periodic behavior occurs in the cloud cavitation and pressure waves form at the collapse of clouds shed downstream. Also, it was found through the image analysis based on the present technique that the pressure wave plays a role as a trigger mechanism to cause a reentrant motion at the downstream end of an attached cavity.

NOVEL SENSORLESS VECTOR CONTROL SYSTEM OF INDUCTION MACHINE BASED ON FLUX OBSERVER IN FIELD WEAKENING

A speed-sensorless vector control system for induction machines （IMs）is presented, According to the vector control theory of IMs, the rotor flux is estimated based on a flux observer,and the speed is estimated through the method of q-axis rotor flux converging on zero with proportional integral regulator, A 0.75 kW,50 Hz,two-pole induction machine was used in the simulation and experimental verification, The simulation model was constructed in Matlab. A series of tests were performed in the field weakening region, for both no-load and loaded operation. The estimated speed tracks the actual speed well in the based speed region and field weakening region （ 1 per unit value to 4 per unit value）. The small estimation error of residual speed is due to the existence of slip.

High Speed Observation of Periodic Cavity Behavior in a Convergent-Divergent Nozzle for Cavitating Water Jet

Cloud cavitation shows an unsteady periodic tendency under a certain flow condition. In a cavitating water jet flow with cavitation clouds, the cavities or the clouds produce high impact at their collapse. In order to make clear a mechanism of the periodic cavity behavior, we experimentally examine the behavior in a transparent cylindrical convergent-divergent nozzle using a high-speed video camera. An effect of upstream pressure fluctuation due to a plunger pump is investigated from a viewpoint of unsteady behavior in a cavitating water jet. As a result, it is found that the cavitating flow has two kinds of oscillation patterns in the cavity length (cavitation cloud region). One is due to the upstream pressure fluctuation caused by the plunger pump. The other is much shorter periodic motion related to the characteristic oscillation of cavitation clouds accompanied with the shrinking (reentrant), growing and shedding motion of the clouds.

Modified sensorless vector control system of IM based on flux observer

This paper presents a speed sensorless vector control system for induction machine (IM),which is based on a flux observer. According to vector control theory of IM,the q-axis rotor flux converging on zero is utilized for speed estimation. Additionally this system solved the online identification of stator resistance by d-axis flux error. The advantages of the proposed system are simplicity and avoidance of the problems caused by only using a voltage model. The effectiveness of the proposed system has been verified by simulation and experimentation.

An Observing Method for Flux and Speed with Direct Torque Control

An observing method for stator flux and rotor flux is presented. Based on the proposed flux observing method, a novel speed estimator has been designed. At last, the speed estimator combined with the flux observing is applied in the direct torque control system without speed sensor. The simulation results show that these methods can improve the accuracy of speed observing and the low speed performance of direct torque control system, and strengthen the robustness of system.

Vehicle Speed Observation Models Based on the Data on the Smartphone GPS

The development of GPS （global positioning system） receiver now can be integrated on a smartphone. GPS receiver on smartphones has been developed for location-based applications. Smartphones are very suitable to be used as an experimental tool, because smartphones are usually equipped with various types of sensors. This paper proposes a model observation vehicle speed on a road section based on the GPS data on the smartphone. Observations made by calculating the speed of the speed of vehicles moving through the data transfer at the GPS location of the smartphone, the data are then sent periodically to the server and server processing and storage of vehicle speed data. After tested with test reliability indicators use RMSE, observations with model observations speed, speed based on GPS data on a smartphone are relevant when compared with the speed directly from the vehicle＇s speedometer with the difference between the value of the difference of speed that is 3.1785 km/h.

Sliding-mode Observer-based Grid Voltage-observation Method with Frequency-fixed Dual SOGI and Cross-compensated Phase-locked Loop

Conventional sliding-mode observer(SMO)-based grid-voltage observation methods often require a low-pass filter(LPF)to remove high-frequency sliding-mode noise.However,a complicated phase-and amplitude-compensation method,which is highly sensitive to the DC-offset,is required.A frequency-adaptive dual second-order generalized integrator(SOGI)can be used to replace the LPF,eliminating the compensation link and the effects of the DC-offset;however,strong coupling is introduced between the front-end SOGI block and back-end phase-locked loop(PLL)block,thereby reducing the dynamic performance.To solve this problem,this study proposes an SMO-based grid-voltage observation method with a frequency-fixed dual SOGI and cross-compensated PLL that can eliminate the frequency coupling between the front-end SOGI block and back-end PLL blocks,thereby increasing its dynamic performance.In this study,the phase and amplitude are compensated simultaneously using the proposed cross-compensation method,achieving an accurate observation of the grid voltage under off-nominal frequencies.An analysis of the small-signal model theoretically verified that the proposed method has good dynamic performance.Finally,the superiority of the proposed method is verified through comparative experiments.

带扰动补偿的永磁同步电机预测速度控制

【目的】为提高永磁同步电机(PMSM)调速系统的抗干扰能力,本文提出了一种具有固定开关频率的带扰动补偿的预测速度控制(PSC)策略。其中,速度环采用PSC,并对扰动进行补偿;电流环采用比例积分(PI)控制。【方法】首先,依据PMSM的机械运动方程推导出实现参考速度的q轴给定电流。为了更精确地跟踪给定q轴电流,本文采用机械运动方程的二阶泰勒展开式,其精度高于一阶前向欧拉离散化。其次,传统的滑模观测器依靠较大的开关增益来确保观测误差在有限的时间内收敛为零,但较大的开关增益会带来严重的抖振现象。因此,本文提出了一种改进的滑模扰动观测器(SMDO),其在Luenberger观测器的基础上增加了一个额外的开关项,不需要很大的开关增益。然后,为了进一步提高PSC的抗干扰性能,在PSC反馈部分的基础上引入了前馈干扰补偿,提出了PSC+SMDO的控制方法。最后,在以dSPACE DS1103为控制核心的试验平台上进行试验。【结果】试验结果表明:所设计的改进SMDO能够准确估计负载扰动,并将扰动信息实时反馈给速度控制器,实现无稳态误差运行;所设计PSC+SMDO速度控制器具有较强的抗干扰性能和跟踪性能,在参数摄动时,基于自抗扰控制(ADRC)的速度控制器受参数变化影响,而PSC+SMDO速度控制器仍能保持良好的鲁棒性;在PSC+SMDO速度控制器下,电机a相电流总谐波失真(THD)为3.44%,分别比PSC、ADRC速度控制器下的a相电流THD低2.21%、4.69%。【结论】与PSC、ADRC以及PI控制器相比,所设计的PSC+SMDO控制器能很好地提高PMSM调速系统的动态响应性能和抗干扰性能。

基于扩展滑模扰动观测器的高速列车分布式速度协同滑模控制

针对高速列车运行中因受外界未知扰动而导致的各车厢速度不同步问题,提出一种基于扩展滑模扰动观测器的高速列车分布式滑模控制算法。首先,考虑高速列车运行的受力情况,建立高速列车多质点模型;其次,设计领航者车厢滑模控制器和跟随者车厢分布式滑模控制器,构建扩展滑模扰动观测器估计外界未知干扰,并反馈给分布式滑模控制器,以消除外界未知干扰对高速列车各车厢速度同步造成的影响,同时利用Lyapunov理论证明了算法的稳定性。最后,通过Matlab仿真验证了该算法能实时精确观测外界未知扰动并反馈补偿,跟随者车厢能快速跟踪领航者车厢的速度,速度跟踪精确度高达99.9%。

Effects of land use and cover change on surface wind speed in China

The surface wind speed(SWS)is affected by both large-scale circulation and land use and cover change(LUCC).In China,most studies have considered the effect of large-scale circulation rather than LUCC on SWS.In this study,we evaluated the effects of LUCC on the SWS decrease during 1979-2015 over China using the observation minus reanalysis(OMR)method.There were two key findings:(1)Observed wind speed declined significantly at a rate of 0.0112 m/(s·a),whereas ERA-Interim,which can only capture the inter-annual variation of observed data,indicated a gentle downward trend.The effects of LUCC on SWS were distinct and caused a decrease of 0.0124 m/(s·a)in SWS;(2)Due to variations in the characteristics of land use types across different regions,the influence of LUCC on SWS also varied.The observed wind speed showed a rapid decline over cultivated land in Northwest China,as well as a decrease in China’s northeastern and eastern plain regions due to the urbanization.However,in the Tibetan Plateau,the impact of LUCC on wind speed was only slight and can thus be ignored.

Compound control for speed and tension multivariable coupling system of reversible cold strip mill

To weaken the nonlinear coupling influence among the variables in the speed and tension system of reversible cold strip mill, a compound control(CC) strategy based on invariance principle was proposed. Firstly, invariance principle was used to realize static decoupling between the speed and tension of reversible cold strip mill. Then, considering the influence caused by the time variation of steel coil radius and rotational inertia of the left and right coilers, as well as the uncertainties, a CC strategy that is composed of extended state observer(ESO) and global sliding mode control(GSMC) with backstepping adaptive was proposed,which further realized dynamic decoupling and coordination control for the speed and tension system. Theoretical analysis shows that the resulting closed-loop system is global bounded stable. Finally, the simulation was carried out on the speed and tension system of a 1422 mm reversible cold strip mill by using the actual data, and through the comparison of the other control strategies, validity of the proposed CC strategy was shown by the results.

A Synthesized Design of Adaptive and Sliding-Mode Observer-Based Incipient Fault Detection for a Quadrotor

This study in westigatn the fault detection and fault atimation problem of a quadrotar with disturbanea.A synthesiand design of adaptive and sliding mode obeerver is propoeed to addres the efkctive detection and atimation of inepient faulta.First,the decom pased subaystems are obtalned through the coardinate transdormation,and the in Stial and ineipkent faults are sea rated from the disturbanon.Second,an adaptive obeerver is applied to the decamposd un petubad subaystem to atimate ineipient faults,while the sliding mode obearver remalns robust to disturbanos for the perturbed subaytem.Lyapumov stahility theory mmas the mavergenae o dynamic erors and the stability of the quadrotor ayatem.Pinally,the dfc tiveess of the proposed synthated algod thm of ineipient fault detection is weified by the quadrotor simulation.

Investigation of monitoring system for high-speed railway subgrade frost heave

This paper presents methods for monitoring frost heave, device requirements, testing principals, and data analysis re- quirements, such as manual leveling observation, automatic monitoring （frost heave, frost depth, and moisture）, track dynamic detection, and track status detection. We focused on the requirements of subgrade frost heave monitoring for high speed railways, and the relationship of different monitoring methods during different phases of the railway. The com- prehensive monitoring system of high speed railway subgrade frost heave provided the technical support for dynamic design during construction and safe operation of the rail system.

Cascaded Sliding-mode Observer and Its Applications in Output Feedback Control Part II:Adaptive Output Feedback Control

Part II proposes a cascaded sliding-mode observer based output feedback controller for control of multi-input multi-output(MIMO)system.The controller,designed based on feedback linearization control strategy,requires the information of the states and perturbations of the system for realization of disturbance rejection.The observer studied in part I[1]is then utilized to provide the accurate estimates of states and perturbations.As is proved,the proposed observer-based controller can ensure Lyapunov stability of the closed-loop system.Also,it can be used for output tracking control.Simulation studies are carried out on a single-wind-energy-conversion-system-infinite-bus(SWNCSIB)system to test the performances of the proposed observer-based output feedback controller.