A modified Preisach hysteresis operator

FeTaPt多层膜的磁粘滞研究徐静【摘要】FeTaPt films were prepared by reactive magnetron co - sputtering on Si substrate at 800℃. X -ray difffraction(XRD) measurement revealed that the multilayer films were single phase. The time dependence of magnetization under double - field were measured and studied by Preisach hysteresis model, and we get the parameters through the simulation. The results show that the magnetic intensity linearly changes with the logarithm of time near coercive force. When the external magnetic field deviate away from coercive force, the magnetic viscosity will change its linear variation, which not only related to H1, and H2, but also to the difference value of H1 and H2 .The smaller the difference between the H1 and H2, is, the more obvious the nonlinear attenuation is.%在800℃基底温度下,以单晶硅为基底,采用磁控溅射法制备了FeTaPt多层膜.通过XRD检测样品为单相,利用VSM测量了样品在双磁场下的磁化强度与时间的关系,并且利用磁滞Preisach模型得到材料的拟和参数.结果表明:在样品矫顽力附近出现了磁化强度随时间对数的线性变化,当磁场偏离矫顽力时,磁粘滞行为将偏离线性变化,这不仅与H1和H2有关,而且与H1、H2的差值有关,H1、H2差值越小,非线性衰减越明显.【期刊名称】《河北工程大学学报（自然科学版）》【年(卷),期】2011(028)003【总页数】3页(P108-110)【关键词】多层膜;磁粘滞;双磁场【作者】徐静【作者单位】河北工程大学理学院,河北邯郸056038【正文语种】中文【中图分类】O.482随着信息时代的发展,对信息记录的密度要求越来越高,而记录介质的尺寸也在不断减小,从而导致介质的热稳定性较差。

A:An Assertion Language for Distributed Systems Andrew Tjang,F´a bio Oliveira,Richard.P.Martin,Thu D.Nguyen{atjang,fabiool,rmartin,tdnguyen}@Department of Computer Science,Rutgers University,Piscataway,NJ08854Abstract.Operator mistakes have been identified as a significant source of unavailability in Internet services.In this paper,we pro-pose a new language,A,for service engineers to write assertions about expected behaviors,proper configurations,and proper struc-tural characteristics.This formalized specification of correct be-havior can be used to bolster system understanding,as well as help toflag operator mistakes in a distributed system.Operator mistakes can be caused by anything from static misconfiguration to physical placement of wires and machines.This language,along with its as-sociated runtime system,seeks to beflexible and robust enough to deal with the wide array of operator mistakes while maintaining a simple interface for designers or programmers.1.IntroductionLarge and complex distributed systems are expanding in impor-tance as users’dependency on Internet services grows.Reasoning about correct behavior of such systems is difficult because these systems are comprised of complex conglomerates of distributed hardware and software,such as load balancers,loggers,databases, and application servers.Unlike traditional monolithic applications,these systems re-quire considerable human interaction to keep them operational,and these interactions are a significant source of unavailability[2,3,7, 9,10,12].More recently,we found that mistakes are responsible for a large fraction of the problems in database administration[9].In this paper,we propose a new method of reducing the above class of errors.Our approach uses a new assertion language,called A,combined with a runtime monitoring system to directly support abstractions that allow system engineers to both(1)describe cor-rect behavior and(2)reason about human-computer interactions in complex distributed systems.The goals of the A language and run-time include both reducing the number and impact of operator mis-takes,as well as reducing the human cost of constructing models of correctness for distributed services.For years,administrators have developed individual,ad-hoc methods of managing operator mistakes and the resulting system errors.Indeed,often significant IT budgets are devoted to develop-ing,maintaining and managing in-house software to operate large-scale systems.We believe that a language specifically tailored to the task of operator-system interaction could improve this process.Instead of a collection of ad-hoc scripts tailored to a specific site and environment,a language-based approach will allow a concise, Permission to make digital or hard copies of all or part of this work for personal or classroom use is granted without fee provided that copies are not made or distributed for profit or commercial advantage and that copies bear this notice and the full citation on thefirst page.To copy otherwise,to republish,to post on servers or to redistribute to lists,requires prior specific permission and/or a fee.Copyright c ACM[to be supplied]...$5.00understandable,and verifiable method of specifying correctness. Codifying the process in a specific language would also ease the generalization and parameterizing of operator tasks,thus allowing for the re-use of software to manage operator interactions across different organizations.For example,an organization could re-use existing parameterized libraries to manage the interactions with load-balancers,databases and application servers instead of having to develop custom scripts as they do today.In this paper we thus argue:•The abstractions in A are suited for verifying correct behavior in distributed systems;•The A runtime supports these abstractions;and•It is easier to use the A language and runtime for preventing and catching mistakes than ad-hoc solutions.A provides a way to name components of a service,access the state of the components(both dynamic attributes and static prop-erties),and conveniently write assertions about these states.The runtime system provides a gateway between A programs and a ser-vice monitoring infrastructure that provides dynamically measured information about the service to the A programs.To abstract human actions,the language has constructs to allow a programmer to de-scribe discrete steps of an operator’s task as well how their models may evolve during the execution of the task.One example might be switching a load balancing policy-from a completely balanced one to a weighted one.We also consider that while modeling performance captures dy-namic behaviors,many mistakes result in improper static configu-rations.In fact,a good number of mistakes resulting in security and latent performance faultsfit this pattern.A and its runtime system have specific constructs that represent configuration state(e.g.,a start-upfile)as well as its audit state(e.g.,a log).We have found that validating both static and dynamic properties was critical for completeness;that is,both are needed to cover a wide range of mistakes.In the remainder of the paper we introduce the reader to the A language and describe the constructs that make A uniquely suited to help system designers formalize their ideas of correct behavior. Section2details A,with Section2.2introducing the running exam-ple mistake used throughout this paper.Section3provides a brief overview of the supporting runtime system.Section4overviews our evaluation methodologies and results.Section5describes re-lated research,with Section5.1describing current solutions and their inadequacies.Finally,Section6looks at ongoing work and future directions.2.The A Assertion LanguageThis section describes the A language.Wefirst give an overview. We then describe a common system,a mistake and an example A program that catches mistakes for that system.Finally,we give a brief overview of the major A language constructs.2.1OverviewA’s primary constructs are assertions,elements,and and tasks. These three abstractions allow the programmer to(1)describe correctness,(2)access system state,and(3)reason about temporal state changes with respect to operator actions.The assert construct was directly inspired by its use in procedu-ral languages such as C and Java.Anecdotally,maintaining a large set of assertions about correct conditions has been critical toward writing correct programs.Indeed,[6],devotes an entire chapter to the subject of how craft assertions for C programs.Some of the key ideas from that work that cross-over into the domain of cor-rectness for the systems we describe are that assertions should(1) be side-effect free,(2)exhibit fail-fast behavior,and(3)should be explicitly labeled to the high-level conditions they are testing.Elements in A were modeled after aggregate types,such as the C struct.In our case,an element describes the current system state of devices such as load balancers and databases.It is the runtime’s job to map the language-level declared state to the current values of the devices.For example,the number of jobs in the run-queue of the OS on a particular machine might be afield of an element.A special stat variable type captures the notion of statistically sampled values,such as load average,for our class of system devices.In addition,because we are concerned with operator mistakes,elements can also describe the configuration state of devices;e.g.values in a configurationfile.Tasks represent sequential execution of an operator’s actions. The language-level construct allows for the programmer to specify which assertions should be checked,and provides interval points to wait for operators to complete actions.Tasks also allow the A programmer to save state in variables to compare past state with present state.The task abstraction thus directly addresses how to describe how system state should change with time,which is often left unresolved in many modeling languages.Execution in A follows a discrete event model,similar in spirit to triggered databases or user-interface libraries(e.g.the Tk widget library[11]).The run-time takes monitored and measured values from real devices as well as input from human operators and for-wards them to a central location.Assertions checks and wait state-ments in tasks map to a scheduled event stream executed at the central location.Operators are then notified when assertions fail.2.2Example System,Mistake,and ProgramIn this section,we briefly introduce an example system,the Linux Virtual Server(LVS),a common mistake made configuring LVS, and an A program designed to catch mistakes operating on the LVS system.One of the main applications of LVS is an advanced load bal-ancing solution.A commonly seen LVS operator misconfiguration [5]occurs when LVS is set up in the direct routing mode with Web servers on the back-end.A popular method to achieve direct routing involves assigning the same IP address that the LVS uses to receive requests from the clients to a virtual interface of a loopback device on each Web server.This causes requests to be handled by the LVS machine,with responses handled directly by the individual Web servers.The caveat is that Web servers must ignore ARP requests for the loopback devices.Clearly,the effect of a misconfiguration here will lead to all Web servers and the load balancer answering ARP requests for the shared IP address,leading to a race condition. The manifestation of this misconfiguration is that some client re-quests might be sent directly to the Web servers,while others go through the load balancer,resulting in an unbalanced load on the Web servers.Although the above is only one specific example in a long list of possible mistakes that can be introduced into a distributed system, it is a fairly representative one with several interesting qualities.Infile:assertions.a:1:config LVSCfg{...2::lvsadm:‘‘ipvsadm.pl’’3:set weight=/root/workers/worker/weight,"";4:}...5:config ApacheCfg{...6::iptables:‘‘iptables.pl’’;7:single destination=/root/chain[...]/destination8::netint:"netinterfaces.pl"9:single hidden=/root/real-interfaces/all/hidden,"";10:}11:online wsall..cpu.util))){14:on;global;15:}else{//print"Web servers load unbalanced"}16:assert dest(wsFigure1.An example set of assertions and configurations in A that help to catch our LVS mistake.Keywords are shown in bold. Firstly,the mistake has a real,tangible impact on the distributed system.Secondly,the mistake is fairly common and simple to achieve.Finally,the impact of the mistake may or may not result in a latent error.Figure1shows a small A program designed to catch mistakes when manipulating an LVS server.At a high-level,lines1-10type the configuration state we care about,in this case the LVS and Web server(Apache)configurationfiles.Lines11-12instantiate the elements types against real servers,and lines13-19are assertions to describe correct behavior.We give a brief,bottom-up description of these language constructs in the remainder of this section.2.3ElementsElements represent states of running service components as re-ported by runtime monitors.Each element must be declared to be of some element type and consists of a number offields.Eachfield can hold a value of a primitive data type,a statistical object,or another element.Rather than being programmer specified,these values within elements are defined by the monitored state of the component.Elements are bound to specific components.In the list-ing,the element lbalancer represents a single load balancer bound to a load balancer that has the address domain.tld.Similarly,wsConfiguration and log types.Since static configurations dictate how a majority of distributed components behave,it is natural to include configuration constructs.Each element may have an attachment of one or more objects of the configuration or log types.Each attached configuration object refers to a set of static information about the service component bound to the element.The definition of a configuration type involves the specification of a set offiles or program outputs(Line2)that can be parsed to obtain the desired static characteristics,a set of drivers that can be used to translate the configurationfiles into the XML format,and a set of XPath queries to extract the desired characteristics.In the same vein,definitions of log types,a log object is a stream of information being written to anyfile.Configuration Aggregates.It is often useful to name an aggregate set of configuration parameters.For our example,the weight of each of the workers seen by LVS is referred to as a set(Line3).A programmer can later refer to all weights using this one parameter.2.4AssertionsMuch like the assert directives in C and Java,an assertion is a boolean expression.In A,assertions make statements about the val-ues in elements.An assertion evaluating to true models correctness, while one evaluating to false models incorrect behavior.Each assertion is comprised of four parts:a name,a conditional expression,a control block,and a set of action statements to be ex-ecuted if the assertion fails.An assertion is thus like a stylized ob-ject in that it contains assertion specific parameters(e.g.frequency to be evaluated),as well as implements a single method that returns a boolean value.Name.A common problem with assertions directives in C and Java is that they can become opaque;sometimes even the author can-not remember the higher-level reason a particular assertion was in-cluded.It thus becomes difficult to know if the assertion or program is faulty.We hope to mitigate this effect by at least forcing program-mers to name the assertions.For example,the name balanced in line13has a simple intuitive meaning.Expression.An expression returns a boolean value.If the statement evaluates to true,the system is correct.If the expression evaluates to false,the code in the action block(the else clause)is eval-uated.In the listing,Line13shows an assertion that models the balanced nature of all Web servers.Control Block.The programmer can optionally specify values to control the scheduling of assertions:frequency,delay(when to start an assertion),status(on or off),and type(global or task related). Action Block.The action block(Line15)refers to what the run-time system should do in the event that the particular assertion has failed.We leave actuation,i.e.adjusting the system in response to failed assertions,as future work.Hierarchical Assertions.The A language provides support for ab-stracting assertions,which can be used to build assertion hierar-chies.This allows programmers to think about correct behavior in terms of high-level concepts that eventually resolve to low-level, specific parameter/value checking.For example,the idea that two components are“connected”is a high-level idea that requires more specific checks.Aggregates.Relations in the expression part of an assertion can accept aggregate element types as arguments.For example,the EQUAL operator can take an aggregate element(e.g.,a set of repli-cas).The EQUAL operation applied to a statfield of an aggregate element returns true if all stat objects in thefield are equal,using the definition of statistical types.The balanced assertion shows this usage.2.5LibrariesLibraries support abstraction over different element instances as well as hide detailed sets of assertions.One can think of libraries as “templates”.Libraries can be organized by components,subcom-ponents,or by goal.Libraries have the added benefit of allowing code reuse via parameterized assertions.Our LVS assertions could be logically classified in many ways. The balanced assertion could be part of a library of assertions on dynamic properties or could be part of a libraryfilled with other properties that need to be“balanced”(eg.memory usage, network usage,etc.).Similarly the dest assertion could be part of a configuration library or could be part of a library indicating connectivity of components.The assertions may also be found in libraries describing their component parts(e.g.an LVS library and a Web server library).The A programmer is free to decide how to organize the models in the most suitable and easily manageable way.2.6TasksTasks represent human-system interactions.One can think of tasks as sets of assertions grouped together with intervening wait state-ments.Tasks,unlike assertions,are stateful and can compare sys-tem properties throughout the course of task execution.This is par-ticularly useful when checking“before”and“after”values of as-sertions with dynamic properties.Our LVS assertions would be included in a task-perhaps one involving setting up a new Web server.For the sake of brevity, the task itself,has been omitted from the listing.Tasks have a few constructs specific to them:Wait statements.These tell the runtime system to wait on particu-lar operator events,explicitly indicated by the operator. Conditional waits.The runtime waits on a specific condition within the system,e.g.an elementfield to reach a certain value. External waits.The runtime system waits for operator input.This is especially useful when some assertions depend on information only known to the operator.An example of this is the hostname of component currently being modified.Call statements.These explicitly call for other non-task specific assertions to be evaluated immediately.Variable assignment.A variable stores the current elementfield for comparison to future values.Wait statements allow system engineers a way to segregate operator actions into subspaces-each with its own set of assertions. Wait statements have a timeout(specified in milliseconds),and will cause the task to run the else block if the action is not completed by the time allocated.A conditional wait keeps the task from reaching the next block of assertions until an expression evaluating element values becomes true(or it times out).3.The A Runtime SystemRecall the most critical job of the run-time is to reflect the real system state in the A run-time.For example,the current values of system configurationfiles and sampled state of running devices must be brought into a single location where the assertions are evaluated.This task is basically system monitoring,which is vast topic in and of itself.In this section we just briefly describe our current implementation.Configuration is obtained through a series of drivers.These drivers take the vastly different configuration formats and create XML equivalents.A programs can then parse these XML fragments in any way.Dynamic information is gathered by a set of monitors, which capture the dynamic state of running service components.all.In the case of the former,itfinds the one reporting host whose identity matches the argument given“domain.tld”.In the latter case,the runtime,matches ws5.1Current Monitoring and Correctness Tools.Assuring correct behavior of distributed systems is often assigned to an organization’s system administrators.The Internet is littered with monitoring and alerting scripts that can assist them with the monumental task of keeping a smoothly operating system.Anec-dotal evidence suggests the coverage and behavior of these tools is often random and chaotic in nature.Their usage and output leave many things open to interpretation and even the smallest of organi-zations may have many of them cobbled together to create a suit-able solution.In any event,these system administration scripts suf-fer from a number of problems that show them to be sub-optimal for ensuring correct behavior of distributed systems.1)They lack continuity:the same script used to monitor and identify problems in network traffic may vastly differ from a script used to monitor CPU utilization,even though one may be tightly related to the other.2) Manageability/Readability:Adding new alerts or monitors can in-volve editing multiple scripts/tools.Determining what components, alerts,monitors,exist also involves multiple scripts/tools in multi-ple formats.4)Interpretation:Many tools provide the means by which information is gathered,but interpretation of this informa-tion is largely left to a person.Different people have differing opin-ions of correctness.A seeks to solve these problem areas by providing a clear and concise method for system designers and administrators to formal-ize policies of correct behavior.The assertions in A are expres-sive enough to encode multi-component dependencies and sim-ple enough to be easily and readily readable and editable.A fea-tures elements,element groups,dynamic bindings,and configura-tion structures-all of which make great strides in simplicity and uniformity.When we look at our LVS case,traditional monitoring and alerting tools might used to detect excessive CPU usage in an overloaded state,or a saturated ually by this time,the effects of the misconfiguration have been exposed to end users as slow response times,timeouts,or other undesirable behavior.The root cause,however,would remain hidden to administrators.5.2Modeling,Verification and Event LanguagesOther systems have combined assertion languages with dynamic assertion checking.Both PSpec[13]and Pip[14]used assertion checking for performance debugging.While Pip focuses on dis-tributed systems,it also seeks to verify their communication struc-ture.However,because they are concerned with dynamic,run time problems as opposed to detecting operator mistakes,these systems did not consider some important static and structural issues,such as improper system configurations and latent security problems.Oper-ator tasks arefirst-class concepts in our assertion language,allow-ing us to detect these types of problems and relate them to specific tasks.There have also been recent languages and systems designed for temporal,event-based programming.For example,FRP[15]is designed with abstractions for temporal event-based programming.A is not as focused on abstracting temporal events handling as it is on expressing correctness about time-varying state.On the systems side,Drools[4]is an event-based rule engine designed to assist enterprises in codifying their business logic.A prime focus of Drools is execution efficiency,and so it can also serve as a framework for other domain specific languages,such as A.Its use and implementation are somewhat orthogonal to our work. 6.Current Status and Future WorkIn this paper we introduced a language for determining correct behavior in distributed systems.We overviewed the many unique constructs in the A language that can help system designers model correct behavior.We also showed the event-based and procedural components that lend themselves nicely to modeling operator tasks.The question of utility of a new domain specific language ver-sus that of traditional languages is a subjective one.More work must be done to investigate how easily A programs are written,and how effective the resulting programs are at modeling correct behav-ior.Our initial experiences have shown promise in a simple three tiered Internet service.Examining A in other distributed scenarios is another avenue for further work.Scalability of A programs is an open issue.Our intuition is that A programs can be modularized and then combined.This combination raises consistency and efficiency problems that might need to be resolved.Ultimately,we believe that having a domain specific language like A can help to structure,organize and formalize ideas of cor-rectly operating systems,especially in the context of operator ac-tions.We have shown that the carefully designed constructs in Afit the domain of distributed systems well.References[1]G.Box,G.Jenkins,and G.Reinsel.Time Series Analysis:Forecastingand Control.Prentice Hall,Inc,Englewood Cliffs,NJ,third edition, 1994.[2]J.Gray.Why do Computers Stop and What Can Be Done About It?InProceedings of5th Symposium on Reliability in Distributed Software and Database Systems,Jan.1986.[3]J.Gray.Dependability in the Internet Era.Keynote presentation at the2nd HDCC Workshop,May2001.[4]Jboss rules(drools)./portal/jbossrules/.[5]Linux virtual server project./.[6]S.Maguire.Writing Solid Code.Microsoft Press,Redmond,WA,1993.[7]B.Murphy and B.Levidow.Windows2000Dependability.TechnicalReport MSR-TR-2000-56,Microsoft Research,June2000.[8]K.Nagaraja,F.Oliveira,R.Bianchini,R.P.Martin,and T.D.Nguyen.Understanding and Dealing with Operator Mistakes inInternet Services.In Proceedings of OSDI’04,Dec.2004.[9]F.Oliveira,K.Nagaraja,R.Bachwani,R.Bianchini,R.P.Martin,and T.D.Nguyen.Understanding and Validating Database System Administration.In Proceedings of the2006USENIX Annual Technical Conference,June2006.[10]D.Oppenheimer,A.Ganapathi,and D.Patterson.Why do InternetServices Fail,and What Can Be Done About It.In Proceedings of USITS’03,Mar.2003.[11]J.Ousterhoust.Tcl and the Tk Toolkit.Addison Wesley,Reading,MA,1994.[12]D.A.Patterson,A.Brown,P.Broadwell,G.Candea,M.Chen,J.Cut-ler,P.Enriquez,A.Fox,E.Kiciman,M.Merzbacher,D.Oppenheimer, N.Sastry,W.Tetzlaff,J.Traupman,and N.Treuhaft.ROC:Motiva-tion,Definition,Techniques,and Case Studies.Technical ReportUCB//CSD-02-1175,UC,Berkeley,Mar.2002.[13]S.E.Perl and W.E.Weihl.Performance Assertion Checking.InProceedings of SOSP’93,Dec.1993.[14]P.Reynolds,C.Killian,J.L.Wiener,J.C.Mogul,M.A.Shah,andA.Vahdat.Pip:Detecting the unexpected in distributed systems.InProc.NSDI2006,May2006.[15]Z.Wan and P.Hudak.Functional Reactive Programming from FirstPrinciples.In ACM SIGPLAN Conference on Programming Language Design and Implementation,June2000.。

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0379. ___D___ is not a condition for a ship of 400 tons gross tonnage and above other than an oil tanker to discharge certain amount of oil or oily mixtures into the sea．对于400总吨及以上的非油轮，下列哪一项不是排放一定数量的油类或油类混合物入海的条件A．the ship is not within a special area 船舶不在特殊区域内B．the ship is more than 12 nautical miles from the nearest land 距最近陆地12海里以上C．the ship is proceeding en route 船舶航行中D．the instantaneous rate of discharge of oil content does not exceed 60 liters per nautical mile含油物的瞬时排放率不超过60升每海里0380. ___D___ is not considered as anti-pollution equipment．（）不被认为是防污设备A．Oil discharge monitoring and control system 油类监控系统B．Oily-water separating equipment 油水分离设备C．Oil filtering system 滤油系统D．Oil loading and discharge system 油类装卸系统0381. A ship that，at any time，operates seaward of the outermost boundary of the territorial sea is required to prepare，submit，and maintain a（n）___C___．[184]任何从事国际航行的船舶都必须准备、提交和保持一份（）A．Synthetic plastic discharge plan 合成塑料排放计划B．Oil discharge plan 油类排放计划C．Shipboard oil pollution emergency plan 船上油类应急计划D．Vapor recovery procedures plan 蒸汽回收程序计划0382. A vessel emitting harmful substances into the air or spilling oil into the sea is a __A____．排放有害物质进入大气或泄漏入海的船舶是（）A．Polluter 污染者B．Emitter 排放者C．Spiller 泄漏者D．Oiler 加油工0383. A vessel in ocean service that does not have an approved means of processing oily bilge slops or oily ballast must have ____A__．从事远洋服务的未配备经认可的处理含油污水或压载水的方法的船舶应持有（）A．A fixed piping system for ballast discharge to a receptionfacility 固定的将压载水排入接收设施的的管路系统B．A discharge outlet for the ballast system on each side of the weather deck 在开敞甲板两侧装有压载水的排放口C．One portable adapter for a shore connection to the ballast line 一个手持的岸上接口与压载水管线之间的适配器D．All of the above 以上全部0384. A vessel to which Annex V to MARPOL 73/78 applies is located in a MARPOL designated special area，14 nautical miles from nearest land．What type of garbage is permitted to be discharged ___D_____．[260]某适用MARPOL 73/78附则V的船舶位于MARPOL 公约指定的特殊区域，距最近陆地14海里，（）垃圾允许排放入海。

中文3450字附二: 外文翻译High Precise Control Method for a New Type ofPiezoelectric Electro—hydraulic Servo Valve Abstract：A new type of piezoelectric electro-hydraulic servo valve system was proposed．And then multilayer piezoelectric actuator based on new piezoelectric ceramic material was used as the electricity-machine converter of the proposed piezoelectric electro-hydraulic servo valve.The proposed piezoelectric electro -hydraulic servo valve has ascendant performance compared with conventional ones.But the system is of high nonlinearity and uncertainty, it cannot achieve favorable control performance by conventional control method．To develop an efficient way to control piezoelectric electro—hydraulic servo valve system．A high—precise fuzzy control method with hysteresis nonlinear model in feedforward loop was proposed.The control method is separated into two parts：a feedforward loop with Preisach hysteresis nonlinear model and a feedback loop with high-precise fuzzy contro1.Experimental results show that the hysteresis loop and the maximum output hysteresis by the PID control method are 4.22％and 2．11 pm, respectively；the hysteresis loop and the maximum output hysteresis by the proposed control method respectively are 0．74％and 0．37μm，respectively；the maximum tracking error by the PID control method for sine wave reference signal is about 5．02％, the maximum tracking error by the proposed control method for sine wave reference sign al is about 0．85％．contro1．Key words：piezoelectric electro—hydraulic servo valve；hysteresis nonlinearity；Preisach model；fuzzy control1 IntroductionElectro—hydraulic servo system is widely applied in industrial domain nowadays．for example．robot drive，machine building, architectural engineering．The electro-hydraulic servo valve is the kernel of the electro-hydraulic servo system,and its performance has decisive effect Of the whole system．The conventional drive mode of electro．hydraulic servo valve has lower resolution and narrower work band width，which restricts the applications of the electro-hydraulic servo valve．The proposed piezoelectric electro-hydraulic servo valve adopts multilayer piezoelectric actuator as electricity-machine converter. This Hew type of piezoelectric electro-hydraulic servo valve has better dynamic performance than that of conventional ones．At present，with the research and the development of new-type actuator based on new type materials, it is possible to make the new electricity-machine converter with high frequency. New materials include piezoelectric ceramic materials, magnetostrjctive materials, shape memory alloys．Thereinto, multilayer piezoelectric actuators based on new piezoelectric ceramic materials have many merits such as small cubage，high resolution，high frequency and large drive force．Hence，they are widely used in the micro-position device of machine tools and other precision machines [1-6]．However, they also have many shortcomings，for example，hysteresis nonlinearity model in feedforward loop was proposed．2 Work principle and characteristic of new-type of piezoelectricelectro-hydraulic ValveBecause the pulling force capacity of multilayer piezoelectric actuator is very poor, it cannot make the slide valve of the electro, hydraulic servo valve bidirectionallv move.Two multilayer piezoelectric actuators were adopted to solve this problem [7-8].The shortcoming of this method is high cost and system is difficult to contro1.Utilizing the restoring force of a leaf spring，one multilayer piezoelectric actuator can realize bidirectional movement of the slide valve in this paper. W hen the voltage imposed on multilayer piezoelectric actuator 1s increased，multilayer piezoelectric actuator will elongate and drive the slide valve to move towards the left，which makes the leaf spring deform．On the contrary, when the voltage imposed on multilayer piezoelectric actuator is reduced，multilayer piezoelectric actuator will be shortened and then drive the slide valve move towards the right by the action of the restoring force of the leaf spring.The structure of new type of piezoelectric electro—hydraulic servo valve is shown in Fig．1．The input-output characteristic of the new type of piezoelectric electro-hydraulic servo valve system indicates that it has hysteresis nonlinearity with nonloca1 memory(see Fig．2).At any reachable point L (Ua ，Ya)in input-output diagram，the number of alternative curve that describes the future path of hysteresis nonlinearity with nonloca1 memory is ly, the future output of the system depends not only on the current output Ya and future input，but also on the past history of input value’s extremum. Hence, the output response of new type of piezoelectric electro-hydraulic servo valve to an applied input voltage becomes unpredictable.In the system，there exist other nonlinearities such as force of friction and work dead zone of valve, furthermore，damping coefficient and oil temperature are also changed with time．The nonlinearity and uncertainty have seriously effects on the position precision. To improve the performance of the new type of piezoelectric electro-hydraulic servo valve system,a valid control method is needed3 Control algorithmAt present, conventional PID controller is widely applied in industrial control domain because of its simple control structure, easy design and inexpensive cost．However, conventional PID controller is difficult to achieve good control performance in the new type of piezoelectric electro, hydraulic servo valve system because the control object has high nonlinearity and uncertainty．Fuzzy controller shows good results in the case of controlling high nonlinear systems. However, conventional fuzzy controller is essentially a kind of nonlinear PD controller, there exists steady state error, which cannot meet the demand of high precise of the system．In this paper, a high-precise fuzzy control algorithm with Preisachhysteresis nonlinear model in feedforward loop was proposed ．The block diagram of the combined controlis shown in Fig ．3．The control system is composed of a feedforward loop based on Preisach model and a feedback loop of high precise fuzzy controller ．Ul( is the output of feedforward loop based on Preisach mode1．As a linear term, it is selected from a Preisach function table based on the given position value ．U2( is the output of the high precise fuzzy controller ．The sum U(t) of feedforward control voltage f and feedback control voltage U2(t) ，as ultimate control voltage ，is acted on new type piezoelectric electro-hydraulic servo valve.3．1 Feedforward loop based on Preisach modelThe open loop response of the new type piezoelectric electro-hydraulic servo valve system under an arbitrary and non-cyclic input signal is shown in Fig ．2．This phenomenon appears as hysteresis nonlinearity with nonlocal memory, which can be predicted by Preisachmode1．The numerical form of Preisach model can bewritten as foliows ：βωαβαd d t u u t f S ⎰⎰=+)(),()( (1)Eqn.(1) can be used to calculate the response of the new type of piezoelectricelectro-hydraulic servo valve subject to a known arbitrary input voltage sequence ．A series of first order functions ''kk r βα of the new type of piezoelectric electro-hydraulic servo valve are experimentally determined ． The procedure is as follows ．The space between zero and saturation voltage Us is divided into n equipartitions, and the voltage of every equantpoint is kUs ／n ，where k=-0，1，2， ⋯ n ．Voltage is applied from zero to every equant point kUs ／n ，and then decreased to zero ．In this process ，the position output values of the new type of piezoelectric electro-hydraulic servo valve are recorded at every equant point between zero and saturation voltage Us ，therewith ，''k k rβα and the Preisach functiontable are obtained(see Fig ．4)，βααβγχβαd d t u d d u t f S t u ⎰⎰⎪⎪⎭⎫ ⎝⎛=+)(),,()( （2） Based on the driver voltage range of the new type of piezoelectric electro ．hydraulic servo valve ， the coordinate space is selected as 0≤'αU ≤ l 50 V and 0≤'βU < 1 50 V From Fig ．4，the limit triangle is divided into several squares and triangles ．Decreasing the size of the squares and triangles is expected to increase the accuracy of the mode1, however, it will spend massive computational time ．Based on the experiments, n is selected as 5，namely, the size of each of sides of the squares and triangles is selected as 30 V.Based on the given position value and the numerical form of the Preisach model ， 1')(-n U t U βγ or )('t U n αγ can be obtained ．Thereby, based on Preisach function table ，the control voltageUl(t) is obtained when 1'-n U βlies on the vertical line or 'αU lies on the horizontal line ．For theinexistence voltage in the Preisach function table ．it can be obtained by the linear interpolation ．In comparison to a conventional feedback controller, the main advantage of this mode1-based feedforward controller is that it can compensate the hysteresis nonlinearity of the system and achieve highly dynamic operation at the same time, and no additional sensor is needed ．This leads to a very simple and inexpensive control system ．The main drawback of the feedforwardcontroller is sensitive to unmodel data and unconsidered external disturbances such as temperature drift ．For a new type of piezoelectric electro —hydraulic servo valve system that needs high control precision ．mode1．based feedforward controller cannot obtain good control effect ．Then a compound control method with feedforward and feedback control project was proposed in this pape. In the feedback control loop ，a high —precise fuzzy control algorithm was adopted ．The method can obtain good performance ．3．2 High precise fuzzy controlConventional fuzzy controller has two input variables ，e and Δe ，and one output variable （U ），they are error, change of error and output control of fuzzy controller ． In the new type of piezoelectric electro-hydraulic servo valve system ，the physical range of the slide valve position error( and change of error (△e) are [-x ，x] and [-Δx ，Δ x]，respectively ．The corresponding discrete universes of discourse of e ，△e and u are E ，EC and U respectively ．E, EC and U are designed as normalized form ：{-n ，-(n 一1)，⋯，0，⋯，n 一1，n}(i=1，2，3) (3)The scale factors are e k ，ec k and u k ，respectively. Thenx n k e /1=, x n k ec /2=,3/n y k u = (4) Based on control rule of conventional fuzzy controller, when e k e < 0．5 and e k ec ∆ <0．5，the conventional fuzzy controller considers the inputs e and e ∆ as zero and the output u is also zero ．However, the inputs e and △e are not certainly equal to zero. Hence conventional fuzzy controller has control dead zone. Control dead zone of conventional fuzzy controller is the main reason why the steady state precision of look-up table algorithm is poor. The key to improving the controlling precision of fuzzy control algorithm based on look-up table is to eliminate its control dead zone.To resolve this problem, an improved fuzzy controller is adopted. When E or EC is not equal to 0, the look-up table is adapted to calculating the control output U; when E or EC are equal to 0,Interpolation algorithm is adopted to calculating the control output U ’ instead of quantization. The method of interpolation calculation is shown in Fig.5. The U(I,j),U(i+1,j),and U(i+1,j+1) are four point in the look-up table ,and the value of U ’ can be calculated based on them.4. Experimental research The position precision of the new type of piezoelectric electro-hydraulic servo valve system is significantly reduced due to the effect of nonlinearity and uncertainty ．In this paper ，the high-precise fuzzy control method with Preisach hysteresis nonlinear model in feedforward loop was developed to solve this problem. To demonstrate the effectiveness of this proposed controlmethod ，a series of experiments were performed on the new type of piezoelectric electro-hydraulic servo valve system under various conditions ．The experimental setup was built. which consisted of industrial control computer, hydraulic pressure experimental bench ，pumping station ，PES arbitrary waveform generator(Model AG1200，Yokogawa Co ．) and multi-purpose FFT analyzer (Model CF-5220，Onosokki Co ．)．The experiments were conducted under a hydraulic pressure of 7 MPa. Hydraulic pressure experimental bench was used to provide the operational environment for the PESV .Pumping station was used to provide the liquid pressure for hydraulic pressure experimental bench ．Waveform generator was used to provide the waveform ．Fourier analyzer was used to analyze the experimental result ． Industrial control computer was used to receive the position feedback signals and provide control voltage based on the proposed control method ． The industrial control computer still includes a 12 bit AD ／DA card (Model PC 一63 l1，Zhongtai Co ．)，a power amplifier and program of the proposed control method ． Industrial control computer accepts the given signal from waveform generator and position feedback signal through A ／D conversion interface ， soon afterwards ， calculates the control voltage signal based on the proposed the control method and sends it through D ／A conversion interface to a power amplifier ．In the power amplifier, the control method was amplified with l 0 times gains to drive the piezoelectric actuator of the PESV The position feedback signal was also sent to the Fourier analyser for analyzing the experimental data besides sending to industrial control computer for calculating the control voltage ．Firstly, the experiments were done under open loop control ， PID control ， and high —precise fuzzy control method with Preisach hysteresis nonlinear model in feedforwardloop ． The hysteresis loop curves were plotted ．Fig ．6(a) shows the hysteresis loop output curve of the system under open loop contro1．It was calculated that hysteresis loop is about 13．08％ and the maximum output hysteresis is about 6.64μm ．Fig ．6(b) shows the hysteresis loop output curve of the system under PID control method ．It was calculated that the hysteresis loop is about 4.22％ and the maximum output hysteresis is about 2.11μm ．This control method can restrain the nonlinear effects of the system ．Fig ．6(c) shows the hysteresis loop output curve of the system under the high-precise fuzzy control method with Preisach hysteresis nonlinear model in feedforward loop ．It wascalculated that the hysteresis loop is about 0.74％ and the maximum output hysteresis is less than 0.37μm ．This control method can virtually eliminate the nonlinear effects of the system ．The control results show that the proposed control method gives the minimum outputhysteresis and the highest precision compared with open loop control andPID contro1．Secondly, the comparative experiments of the tracking result for a sine wave reference signal under PID control method and the proposed control method were done．Fig．7 shows the tracking result of PID control method for sine wave reference signa1．The maximum tracking error is about 5.02％．For the position precise requirement, this tracking result cannot be accepted．The main reason for this result is the hysteresis nonlinearity of the new type of piezoelectric Electro-hydraulic servo valve system．Fig．8 shows the tracking result of the proposed control method for sine wave reference signa1．The maximum tracking error is about 0.85％．The tracking results show that the proposed control scheme gives faster and more accurate responses compared with those Of PID contro1, and they can satisfy the high precision demand of the new type of piezoelectric electro-hydraulic servo valve system．5. Conclusions1) A new type of piezoelectric electro-hydraulic servo valve system is proposed．Multilayer piezoelectric actuator based on new piezoelectric ceramic materials is used as the electricity-machine converter of the proposed piezoelectric electro-hydraulic servo valve．2) Because of high nonlinearity and uncertainty of the proposed piezoelectric electro—hydraulic servo valve system，the precision requirements for position are influenced seriously．Hence．a high—precise fuzzy control method with Preisach hysteresis nonlinear model in feedforward loop was proposed．The proposed control method can availably eliminate the influence of the nonlinearity and uncertainty, and improve the performance of the new type of piezoelectric electro—hydraulic servo valve system．References[1] K1M J D，NAM S R．Development of a micro-depth c0ntrol systemfor an ultra-precision lathe using a piezo-electric actuator[J]．Intemationa1 Jouma1 of Machine Too1s& Manufacture，I997，37(4)：495—509[2] KATSUSH1 F, M1TSUNOR1 U，NAOTAKE M Displacement Control of piezoelectricelement bv feedback of induced charge[J] Nan0fechnology，1 998，9(2)：93—98[3] SUN Liming, SUN Shao-yun，QU Dong-shen，eta1．Micro-drive positioning system based0n PZT and its cont roll J1_Optics and Precisi0n Engineering 2004，12(1)：55—59．(in Chines[4] WE1 Yan-ding LU Yong-gui, CHEN Zi-chen . Research on open-1oop precisionpositioning contro1 of a microdisplacement platform based on piezoelectric actuators[J]．Chinese Jouma1 of Mechanica1 Engineering，2004，40(12)：8l_85．(in Chinese[5] ZHOU Miao-lei, YANG Zhi-gang,GAO Wei, etal. Fuzzy control of a new type ofpiezoelectric direct drive electro-hydraulic servo valve[C]// Proceedings of the Fourth International Conference on Machine Learning and Cybernetics. Guangzhou: IEEE Computer Soc, 2005；；819-824[6] YI Y0u-ping SEEMAN W GAUSMAN R, eta1. A new hybrid piezoelectric ultrasonic motorwith two stator[J]Jouma1 of Central South University ofTechno1og 2005，12(3)：324—328 [7] YOKOTA S，HIRAMOTO K. Ultra high．speed electro-hydraulic servo va1ve by makinguse of a multilayered piezoelectric device (PZT)(compensation of a hysteresis by introducing a software algorithm)[J]l Tran a i0n of Japan society of Mechanical Engineers Part B, 1991, 57(533):182-187[8]LU Hao，ZHU Cheng-lin，ZENG Si，eta1．Study on the new kind of Electro-hydraulichigh-speed on-off valve driven by pzt components and its high．powerful and speedy technique[J]．Chinese Journal of References Mechanical Engineering，2002，38(8)：1 1 8-12 1．(in Chinese)[9] GE MUSE J Modeling hysteresis in piezoceramic actuators[J]．Precision Engineering，1995，17(3)：21 l一221·[10] L1U Shao-jun，HUANG Zhong-hua，CHEN Yi-zhang. Automobileactive supension on system with fuzzy control[J]. Journal of Cental South University ofTechnology,2004，11(2)：206-209新型直动式压电电液伺服阀复合控制方法摘要：设计了一种新型直动式压电电液伺服阀。

[2201] Which document lists all the lifesaving equipment required for a vessel ?______A. Certificate of InspectionB. American Bureau of Shipping Classification CertificateC. International Convention for the Safety of Life at Sea CertificateD. Certificate of Registry哪一个文件列出船上要求的救生设备？检验证书[2202] Which document will describe lifesaving equipment located aboard your vessel?______A. Muster ListB. Certificate of InspectionC. Forecastle CardD. Clearance Papers哪种文件上有你船上关于救生设备的描述？检查证书。

[2203] Which emergency equipment should you keep near the towing bitts ?______A. A self-contained breathing apparatus (SCBA)B. A boat hook and a spanner wrenchC. A fire ax and / or cutting torchD. A Stokes litter basket你应该在拖带缆桩旁边准备什么紧急设备？消防斧或者切割器。

[2204] Which ending is NOT acceptable in a wire rope that is free to rotate when hoisting?A. Poured socketB. Liverpool eye spliceC. Eye formed with a pressure clamped sleeveD. Eye formed by clips为了让钢丝绳吊起时不至于旋转下面哪种绳端不被采用？利物浦眼接头。