期刊文献+
共找到1,971篇文章
< 1 2 99 >
每页显示 20 50 100
Regulations for the Manufacture and Control of Live Poliovirus Vaccine: International Experience and China’s Path
1
作者 Miao Wu 《Chinese Medical Sciences Journal》 CAS CSCD 2023年第4期315-320,共6页
The eradication of poliomyelitis is a landmark achievement in the history of public health, providing strong protection for children’s health. The introduction of the Chinese Regulations for the Manufacture and Contr... The eradication of poliomyelitis is a landmark achievement in the history of public health, providing strong protection for children’s health. The introduction of the Chinese Regulations for the Manufacture and Control of Live Poliovirus Vaccine is a prerequisite and safeguard for the large-scale production and use of domestically produced live poliovirus vaccines, serving as an indispensable component of vaccine safety. This article, based on archival documents, letters, collections of essays, and oral interviews, examines the historical experience of the development of Chinese Regulations for the Manufacture and Control of Live Poliovirus Vaccine. It contends that the emphasis on localization and the active engagement in international cooperation are critical factors in the swift introduction of Chinese Regulations for the Manufacture and Control of Live Poliovirus Vaccine. 展开更多
关键词 Chinese regulations for the Manufacture and control of Live Poliovirus Vaccine international cooperation localization Gu Fang Zhou
下载PDF
Modified Two-Degrees-of-Freedom Internal Model Control for Non-Square Systems with Multiple Time Delays 被引量:25
2
作者 Jian-Chang Liu Nan Chen Xia Yu 《Journal of Harbin Institute of Technology(New Series)》 EI CAS 2014年第2期122-128,共7页
A modified two-degrees-of-freedom( M-TDOF) internal model control( IMC) method is proposed for non-square systems with multiple time delays and right-half-plane( RHP) zeros. In this method,pseudo-inverse is introduced... A modified two-degrees-of-freedom( M-TDOF) internal model control( IMC) method is proposed for non-square systems with multiple time delays and right-half-plane( RHP) zeros. In this method,pseudo-inverse is introduced to design the internal model controller,and a desired closed-loop transfer function is designed to eliminate the unrealizable factors of the derived controller. In addition,set-point tracking and load-disturbance rejection of each process are separately controlled by two controllers. The simulation results show that in addition to high decoupling performance and robustness,the proposed control method also effectively improves loaddisturbance rejection and simultaneously optimizes the input tracking performance and disturbance rejection performance by selecting the parameters of controllers. Furthermore,the higher tolerance of model mismatch is achieved in this paper. 展开更多
关键词 non-square system two degrees of freedom internal model control
下载PDF
Multi-loop Internal Model Controller Design Based on a Dynamic PLS Framework 被引量:9
3
作者 胡斌 郑平友 梁军 《Chinese Journal of Chemical Engineering》 SCIE EI CAS CSCD 2010年第2期277-285,共9页
In this paper,a multi-loop internal model control(IMC) scheme in conjunction with feed-forward strategy based on the dynamic partial least squares(DyPLS) framework is proposed.Unlike the traditional methods to decoupl... In this paper,a multi-loop internal model control(IMC) scheme in conjunction with feed-forward strategy based on the dynamic partial least squares(DyPLS) framework is proposed.Unlike the traditional methods to decouple multi-input multi-output(MIMO) systems,the DyPLS framework automatically decomposes the MIMO process into a multi-loop system in the PLS subspace in the modeling stage.The dynamic filters with identical structure are used to build the dynamic PLS model,which retains the orthogonality among the latent variables.To address the model mismatch problem,an off-line least squares method is applied to obtain a set of optimal filter parameters in each latent space.Without losing the merits of model-based control,a simple and easy-tuned IMC structure is readily carried over to the dynamic PLS control framework.In addition,by projecting the measurable disturbance into the latent subspace,a multi-loop feed-forward control is yielded to achieve better performance for disturbance rejection.Simulation results of a distillation column are used to further demonstrate this new strategy outperforms conventional control schemes in servo behavior and disturbance rejection. 展开更多
关键词 internal model controller partial least squares latent subspace servo behavior disturbance rejection
下载PDF
Design of active disturbance rejection internal model control strategy for SISO system with time delay process 被引量:3
4
作者 靳其兵 刘立业 《Journal of Central South University》 SCIE EI CAS CSCD 2015年第5期1725-1736,共12页
A novel control scheme of active disturbance rejection internal model control(ADRIMC) is proposed to improve the anti-interference ability and robustness for the dead-time process. The active anti-interference concept... A novel control scheme of active disturbance rejection internal model control(ADRIMC) is proposed to improve the anti-interference ability and robustness for the dead-time process. The active anti-interference concept is introduced into the internal model control(IMC) by analyzing the relationship between IMC and disturbance observer control(DOB). Further, a design process of disturbance filter is presented to realize the active anti-interference ability for ADRIMC scheme. The disturbance filter is used to estimate an equivalent disturbance consisting of both external disturbances and internal disturbances caused by model mismatches.Simulation results demonstrate that the proposed method possesses a good disturbance rejection performance, though losing some partial dynamic performance. In other words, the proposed method shows a tradeoff between the dynamic performance and the system robust. 展开更多
关键词 internal model control (IMC) disturbance observer (DOB) active disturbance rejection internal model controller(ADRIMC) low pass filter (LPF) robusmess
下载PDF
Vehicle Active Steering Control Research Based on Two-DOF Robust Internal Model Control 被引量:12
5
作者 WU Jian LIU Yahui +3 位作者 WANG Fengbo BAO Chunjiang SUN Qun ZHAO Youqun 《Chinese Journal of Mechanical Engineering》 SCIE EI CAS CSCD 2016年第4期739-746,共8页
Because of vehicle's external disturbances and model uncertainties,robust control algorithms have obtained popularity in vehicle stability control.The robust control usually gives up performance in order to guarantee... Because of vehicle's external disturbances and model uncertainties,robust control algorithms have obtained popularity in vehicle stability control.The robust control usually gives up performance in order to guarantee the robustness of the control algorithm,therefore an improved robust internal model control(IMC) algorithm blending model tracking and internal model control is put forward for active steering system in order to reach high performance of yaw rate tracking with certain robustness.The proposed algorithm inherits the good model tracking ability of the IMC control and guarantees robustness to model uncertainties.In order to separate the design process of model tracking from the robustness design process,the improved 2 degree of freedom(DOF) robust internal model controller structure is given from the standard Youla parameterization.Simulations of double lane change maneuver and those of crosswind disturbances are conducted for evaluating the robust control algorithm,on the basis of a nonlinear vehicle simulation model with a magic tyre model.Results show that the established 2-DOF robust IMC method has better model tracking ability and a guaranteed level of robustness and robust performance,which can enhance the vehicle stability and handling,regardless of variations of the vehicle model parameters and the external crosswind interferences.Contradiction between performance and robustness of active steering control algorithm is solved and higher control performance with certain robustness to model uncertainties is obtained. 展开更多
关键词 active steering internal model control model tracking robust performance crosswind disturbances
下载PDF
Generalized Internal Model Robust Control for Active Front Steering Intervention 被引量:8
6
作者 WU Jian ZHAO Youqun +2 位作者 JI Xuewu LIU Yahui ZHANG Lipeng 《Chinese Journal of Mechanical Engineering》 SCIE EI CAS CSCD 2015年第2期285-293,共9页
Because of the tire nonlinearity and vehicle's parameters'uncertainties,robust control methods based on the worst cases,such as H_∞,μsynthesis,have been widely used in active front steering control,however,in orde... Because of the tire nonlinearity and vehicle's parameters'uncertainties,robust control methods based on the worst cases,such as H_∞,μsynthesis,have been widely used in active front steering control,however,in order to guarantee the stability of active front steering system(AFS)controller,the robust control is at the cost of performance so that the robust controller is a little conservative and has low performance for AFS control.In this paper,a generalized internal model robust control(GIMC)that can overcome the contradiction between performance and stability is used in the AFS control.In GIMC,the Youla parameterization is used in an improved way.And GIMC controller includes two sections:a high performance controller designed for the nominal vehicle model and a robust controller compensating the vehicle parameters'uncertainties and some external disturbances.Simulations of double lane change(DLC)maneuver and that of braking on split-μroad are conducted to compare the performance and stability of the GIMC control,the nominal performance PID controller and the H_∞controller.Simulation results show that the high nominal performance PID controller will be unstable under some extreme situations because of large vehicle's parameters variations,H_∞controller is conservative so that the performance is a little low,and only the GIMC controller overcomes the contradiction between performance and robustness,which can both ensure the stability of the AFS controller and guarantee the high performance of the AFS controller.Therefore,the GIMC method proposed for AFS can overcome some disadvantages of control methods used by current AFS system,that is,can solve the instability of PID or LQP control methods and the low performance of the standard H_∞controller. 展开更多
关键词 active front steering system generalized internal model robust control H_∞ optimization PID split-μ road
下载PDF
Improvement of precision for pendulous integrating gyro accelerometer via adaptive internal model control 被引量:1
7
作者 Xu Fengxia Xia Gang +2 位作者 Zeng Ming Sun Baoku Zhao Xuezeng 《Journal of Systems Engineering and Electronics》 SCIE EI CSCD 2007年第4期841-845,共5页
An adaptive internal mode control is proposed to eliminate effectively periodic disturbance with uncertain frequency caused by input error angle of PIGA (Pendulous Integrating Gyro Accelerometer). An adaptive algori... An adaptive internal mode control is proposed to eliminate effectively periodic disturbance with uncertain frequency caused by input error angle of PIGA (Pendulous Integrating Gyro Accelerometer). An adaptive algorithm with periodic disturbance frequency identification on line is applied and the internal model controller parameters are adjusted to eliminate disturbance. Then the convergence of this algorithm and the stability of the system are proved by the averaging method. Simulation results verify the proposed scheme can eliminate periodic disturbance and improve the test precision for PIGA effectively. 展开更多
关键词 PIGA periodic disturbance adaptive algorithm internal model control
下载PDF
Support vector regression-based internal model control 被引量:2
8
作者 黄宴委 彭铁根 《Journal of Harbin Institute of Technology(New Series)》 EI CAS 2007年第3期411-414,共4页
This paper proposes a design of internal model control systems for process with delay by using support vector regression(SVR).The proposed system fully uses the excellent nonlinear estimation performance of SVR with t... This paper proposes a design of internal model control systems for process with delay by using support vector regression(SVR).The proposed system fully uses the excellent nonlinear estimation performance of SVR with the structural risk minimization principle.Closed-system stability and steady error are analyzed for the existence of modeling errors.The simulations show that the proposed control systems have the better control performance than that by neural networks in the cases of the training samples with small size and noises. 展开更多
关键词 internal model control support vector machine neural networks steady error STABILITY
下载PDF
Hybrid internal model control and proportional control of chaotic dynamical systems 被引量:1
9
作者 齐冬莲 姚良宾 《Journal of Zhejiang University Science》 EI CSCD 2004年第1期62-67,共6页
A new chaos control method is proposed to take advantage of chaos or avoid it. The hybrid Internal Model Control and Proportional Control learning scheme are introduced. In order to gain the desired robust performance... A new chaos control method is proposed to take advantage of chaos or avoid it. The hybrid Internal Model Control and Proportional Control learning scheme are introduced. In order to gain the desired robust performance and ensure the system's stability, Adaptive Momentum Algorithms are also developed. Through properly designing the neural network plant model and neural network controller, the chaotic dynamical systems are controlled while the parameters of the BP neural network are modified. Taking the Lorenz chaotic system as example, the results show that chaotic dynamical systems can be stabilized at the desired orbits by this control strategy. 展开更多
关键词 CHAOS Neural network internal model control Proportional control
下载PDF
SVM Approximate-based Internal Model Control Strategy 被引量:15
10
作者 WANG Yao-Nan YUAN Xiao-Fang 《自动化学报》 EI CSCD 北大核心 2008年第2期172-179,共8页
一台支持向量机器(SVM ) 近似底的内部模型控制(IMC ) 策略为同步发电机的蒸气 valving 控制被介绍。建议 SVM IMC 策略包括二主要部分:在内部模型结构的 SVM 近似反的控制器和无常赔偿。SVM 反的控制器经由泰勒扩大用一条输入产量近... 一台支持向量机器(SVM ) 近似底的内部模型控制(IMC ) 策略为同步发电机的蒸气 valving 控制被介绍。建议 SVM IMC 策略包括二主要部分:在内部模型结构的 SVM 近似反的控制器和无常赔偿。SVM 反的控制器经由泰勒扩大用一条输入产量近似途径直接被导出,并且没有进一步的联机训练,它通过非线性的系统鉴定被实现。而且,一个坚韧性过滤器在内部模型结构被用于无常赔偿。模拟为蒸气 valving 控制显示出 SVM IMC 策略的有效性。 展开更多
关键词 内模控制 非线性控制 支持向量机 神经网络 逼近模型
下载PDF
Temperature Control Based on Fuzzy Logic Two-degree-of-freedom Smith Internal Model 被引量:4
11
作者 WANG Zhigang HE Meng 《Instrumentation》 2020年第2期1-8,共8页
According to the characteristics of the large time delay,nonlinearity and the great inertia of temperature control system in biomass pyrolysis reactor,a two-degree-of-freedom Smith internal model controller based on f... According to the characteristics of the large time delay,nonlinearity and the great inertia of temperature control system in biomass pyrolysis reactor,a two-degree-of-freedom Smith internal model controller based on fuzzy control is proposed.Firstly,the mathematical model of the temperature control system is established by using the step response method,and then the two-degree-of-freedom Smith internal model controller is designed,and the good tracking performance and disturbance suppression performance can be obtained by designing the set value tracking controller and interference rejection capability.Secondly,the fuzzy control algorithm is used to realize the on-line tuning of the control parameters of the two-degree-of-freedom Smith internal model algorithm.The simulation results show that,compared with the traditional internal model control,fuzzy internal model PID control and two-degree-of-freedom Smith internal model control,the algorithm proposed in this paper improves the influence of lag time on the control system,realizes the separation control of set point tracking and anti-jamming performance and the self-tuning of control parameters,and improves the control performance of the system. 展开更多
关键词 Smith Predictive controller internal model control Two Degrees of Freedom Fuzzy control Algorithm
下载PDF
Model reduction and active control of flexible beam using internal balance technique
12
作者 谢永 赵童 蔡国平 《Applied Mathematics and Mechanics(English Edition)》 SCIE EI 2011年第8期1009-1018,共10页
The internal balance technique is effective for the model reduction in flexible structures, especially the ones with dense frequencies. However, due to the difficulty in extracting the internal balance modal coordinat... The internal balance technique is effective for the model reduction in flexible structures, especially the ones with dense frequencies. However, due to the difficulty in extracting the internal balance modal coordinates from the physical sensor readings, research on this topic has been mostly theoretical so far, and little has been done in experiments or engineering applications. This paper studies the internal balance method theoretically as well as experimentally and designs an active controller based on the reduction model. The research works on a digital signal processor (DSP) TMS320F2812- based experiment system with a flexible beam and proposes an approximate approach to access the internal balance modal coordinates. The simulation and test results have shown that the proposed approach is feasible and effective, and the designed controller is successful in restraining the beam vibration. 展开更多
关键词 flexible beam internal balance model reduction active control EXPERIMENT
下载PDF
Eigen-Space Decomposition(ESD)Method for the Design of Internal Model Controller(IMC)from Noisy Input and Output Plant Data
13
作者 吴国海 华建兴 《Journal of China Textile University(English Edition)》 EI CAS 1999年第4期13-16,共4页
A novel approach to design Internal Model Controller(IMC)is proposed in this paper directly from measuredinput and output plant data,which are assumed to becontaminated by measurement noise.In order to avoidthe compli... A novel approach to design Internal Model Controller(IMC)is proposed in this paper directly from measuredinput and output plant data,which are assumed to becontaminated by measurement noise.In order to avoidthe complicated structure-identification problem inmost cases,two Finite Impulse Response(FIR)modelsare taken to represent the plant model and the internalmodel controller respectively.Taking account of mea-surement noise both in the plant input and its output,anESD based Total Least Squares(TLS)solution is appliedfor the unbiased identification of the plant model and itsinverse model,the latter constitutes the internal modelcontroller according to the principle that the internalmodel controller approximates the inverse dynamics ofthe plant model.Simulations are given for a testifica-tion. 展开更多
关键词 internal model control total least SQUARES EIGEN - space DECOMPOSITION parameter estimation identification
下载PDF
Synthetical Control of AGC/LPC System Based on Neural Networks Internal Model Control
14
作者 Hu He, Xiaodong Luan, Yikang Sun Information Engineering School, University of Science and Technology Beijing, Beijing 100083, China 《Journal of University of Science and Technology Beijing》 CSCD 2001年第1期75-77,共3页
One synthetical control method of AGC/LPC system based on intelligence control theory-neural networks internal model control method is presented. Genetic algorithm (GA) is applied to optimize the parameters of the neu... One synthetical control method of AGC/LPC system based on intelligence control theory-neural networks internal model control method is presented. Genetic algorithm (GA) is applied to optimize the parameters of the neural networks. Simulation results prove that this method is effective. 展开更多
关键词 hot strip rolling AGC LOOPER neural networks internal model control GA
下载PDF
Electrostatic Suspension System Nonlinear Character Analysis and Its Internal Model Control
15
作者 糜长军 郭晋峰 +1 位作者 金志华 田蔚风 《Journal of Shanghai Jiaotong university(Science)》 EI 2007年第3期377-382,共6页
Nonlinearity is an important characteristic in electrostatic suspension system (ESS). This paper concludes the nonlinear parts in ESS, which generally result from the relationships between rotor displacement and capac... Nonlinearity is an important characteristic in electrostatic suspension system (ESS). This paper concludes the nonlinear parts in ESS, which generally result from the relationships between rotor displacement and capacitance, rotor displacement and electrostatic force, and control voltage and electrostatic force. In terms of the nonlinearities, a new control method with modified internal model control (IMC) was proposed to analyze the ESS, deduce the transfer function of the modified IMC controller in ESS, and simulate this new application in ESS. Comparing with proportional integral derivative (PID) control, IMC has only a parameter, and has better performance. As a result, IMC solves nonlinearity error well in ESS with only one uncertain parameter, and performs well when the rotor has large displacement. 展开更多
关键词 electrostatic suspension system (ESS) internal model control (IMC) NONLINEARITY
下载PDF
Adaptive Internal Model Control of a DC Motor Drive System Using Dynamic Neural Network
16
作者 Farouk Zouari Kamel Ben Saad Mohamed Benrejeb 《Journal of Software Engineering and Applications》 2012年第3期168-189,共22页
This work concerns the study of problems relating to the adaptive internal model control of DC motor in both cases conventional and neural. The most important aspects of design building blocks of adaptive internal mod... This work concerns the study of problems relating to the adaptive internal model control of DC motor in both cases conventional and neural. The most important aspects of design building blocks of adaptive internal model control are the choice of architectures, learning algorithms, and examples of learning. The choice of parametric adaptation algorithm for updating elements of the conventional adaptive internal model control shows limitations. To overcome these limitations, we chose the architectures of neural networks deduced from the conventional models and the Levenberg-marquardt during the adjustment of system parameters of the adaptive neural internal model control. The results of this latest control showed compensation for disturbance, good trajectory tracking performance and system stability. 展开更多
关键词 Adaptive internal model control RECURRENT NEURAL Network DC MOTOR PARAMETRIC ADAPTATION Algorithm LEVENBERG-MARQUARDT
下载PDF
Optimized Model Based Controller with Model Plant Mismatch for NMP Mitigation in Boost Converter
17
作者 R.Prasanna Uma Govindarajan NSBhuvaneswari 《Computer Systems Science & Engineering》 SCIE EI 2023年第8期1961-1979,共19页
In this paper,an optimized Genetic Algorithm(GA)based internal model controller-proportional integral derivative(IMC-PID)controller has been designed for the control variable to output variable transfer function of dc... In this paper,an optimized Genetic Algorithm(GA)based internal model controller-proportional integral derivative(IMC-PID)controller has been designed for the control variable to output variable transfer function of dc-dc boost converter to mitigate the effect of non-minimum phase(NMP)behavior due to the presence of a right-half plane zero(RHPZ).This RHPZ limits the dynamic performance of the converter and leads to internal instability.The IMC PID is a streamlined counterpart of the standard feedback controller and easily achieves optimal set point and load change performance with a single filter tuning parameterλ.Also,this paper addresses the influences of the model-based controller with model plant mismatch on the closed-loop control.The conventional IMC PID design is realized as an optimization problem with a resilient controller being determined through a genetic algorithm.Computed results suggested that GA–IMC PID coheres to the optimum designs with a fast convergence rate and outperforms conventional IMC PID controllers. 展开更多
关键词 Boost converter non-minimum phase internal model control dynamic controller
下载PDF
Predictive Functional Controller with a Similar Proportional Integral Optimal Regulator Structure:Comparison with Traditional Predic-tive Functional Controller and Application to Heavy Oil Coking Equipment 被引量:1
18
作者 张日东 王树青 《Chinese Journal of Chemical Engineering》 SCIE EI CAS CSCD 2007年第2期247-253,共7页
By extending the system's state variables,a novel predictive functional controller has been developed.The structure of this controller is similar to that of classical proportional integral(PI)optimal controller an... By extending the system's state variables,a novel predictive functional controller has been developed.The structure of this controller is similar to that of classical proportional integral(PI)optimal controller and in-cludes a control block that can perform a feed-forward control of future P-step set points.It considers both the state variables and the output errors in its cost function,which results in enhanced control performance compared with traditional state space predictive functional control(TSSPFC)methods that consider only the predictive output er-rors.The predictive functional controller(PFC)has been compared with TSSPFC in terms of tracking ability,dis-turbance rejection,and also based on its application to heavy oil coking equipment.The results obtained show the effectiveness of the controller. 展开更多
关键词 state space model PI optimal regulator predictive functional control
下载PDF
Event-triggered robust cooperative output regulation for a class of linear multi-agent systems with an unknown exosystem
19
作者 Yangyang Qian Lu Liu 《Journal of Automation and Intelligence》 2024年第2期119-127,共9页
This paper investigates the robust cooperative output regulation problem for a class of heterogeneousuncertain linear multi-agent systems with an unknown exosystem via event-triggered control (ETC). By utilizingthe in... This paper investigates the robust cooperative output regulation problem for a class of heterogeneousuncertain linear multi-agent systems with an unknown exosystem via event-triggered control (ETC). By utilizingthe internal model approach and the adaptive control technique, a distributed adaptive internal model isconstructed for each agent. Then, based on this internal model, a fully distributed ETC strategy composed ofa distributed event-triggered adaptive output feedback control law and a distributed dynamic event-triggeringmechanism is proposed, in which each agent updates its control input at its own triggering time instants. It isshown that under the proposed ETC strategy, the robust cooperative output regulation problem can be solvedwithout requiring either the global information associated with the communication topology or the bounds ofthe uncertain or unknown parameters in each agent and the exosystem. A numerical example is provided toillustrate the effectiveness of the proposed control strategy. 展开更多
关键词 Adaptive control Event-triggered control internal model Multi-agent systems Output regulation
下载PDF
Optimal Cooperative Secondary Control for Islanded DC Microgrids via a Fully Actuated Approach
20
作者 Yi Yu Guo-Ping Liu +1 位作者 Yi Huang Peng Shi 《IEEE/CAA Journal of Automatica Sinica》 SCIE EI CSCD 2024年第2期405-417,共13页
DC-DC converter-based multi-bus DC microgrids(MGs) in series have received much attention, where the conflict between voltage recovery and current balancing has been a hot topic. The lack of models that accurately por... DC-DC converter-based multi-bus DC microgrids(MGs) in series have received much attention, where the conflict between voltage recovery and current balancing has been a hot topic. The lack of models that accurately portray the electrical characteristics of actual MGs while is controller design-friendly has kept the issue active. To this end, this paper establishes a large-signal model containing the comprehensive dynamical behavior of the DC MGs based on the theory of high-order fully actuated systems, and proposes distributed optimal control based on this. The proposed secondary control method can achieve the two goals of voltage recovery and current sharing for multi-bus DC MGs. Additionally, the simple structure of the proposed approach is similar to one based on droop control, which allows this control technique to be easily implemented in a variety of modern microgrids with different configurations. In contrast to existing studies, the process of controller design in this paper is closely tied to the actual dynamics of the MGs. It is a prominent feature that enables engineers to customize the performance metrics of the system. In addition, the analysis of the stability of the closed-loop DC microgrid system, as well as the optimality and consensus of current sharing are given. Finally, a scaled-down solar and battery-based microgrid prototype with maximum power point tracking controller is developed in the laboratory to experimentally test the efficacy of the proposed control method. 展开更多
关键词 DC microgrids distributed control high-order fully actuated system approach linear quadratic regulator microgrid modeling secondary control
下载PDF
上一页 1 2 99 下一页 到第
使用帮助 返回顶部