Adaptive controlImprovements in CNC machine tools depend on the refinement of adaptive control, which is theautomatic monitoring and adjustment of machining conditions in response to variations inoperation performance. With a manually controlled machine tool, the operator watches forchanges in machining performance (caused, for example, by a dull tool or a harder workpiece)and makes the necessary mechanical adjustments. An essential element of NC and CNCmachining, adaptive control is needed to protect the tool, the workpiece, and the machine fromdamage caused by malfunctions or by unexpected changes in machine behaviour. Adaptivecontrol is also a significant factor in developing unmanned machining techniques.One example of adaptive control is the monitoring of torque to a machine tool’s spindle andservomotors. The control unit of the machine tool is programmed with data defining theminimum and maximum values of torque allowed for the machining operation. If, for example, ablunt tool causes the maximum torque, a signal is sent to the control unit, which corrects thesituation by reducing the feed rate or altering the spindle speed.Basic principles.Several other techniques enter into the design of advanced control systems. Adaptive control is thecapability of the system to modify its own operation to achieve the best possible mode of operation. Ageneral definition of adaptive control implies that an adaptive system must be capable of performingthe following functions: providing continuous information about the present state of the...Improvements in CNC machine tools depend on the refinement of adaptive control, which is theautomatic monitoring and adjustment of machining conditions in response to variations in operationperformance. With a manually controlled machine tool, the operator watches for changes in machiningperformance (caused, for example, by a dull tool or a harder workpiece) and makes the necessary...http://www.controleng.com/single-article/patent-for-cnc-adaptive-control-system/dcd02f7f852695a253965ee939016628.html sCNC integrates adaptive control to addproductivityFanuc iAdapt S adaptive control solution has beenintegrated into computer numerical controls to improve the
ability for CNC material removal and decrease CNC cycletime. 07/06/2011anuc Factory Automation America (Fanuc FA America) has integrated its iAdapt S adaptivecontrol solution into the CNC system for increased machine tool productivity. Fanuc iAdapt Simproves material removal and minimizes cycle time by automatically optimizing the cuttingfeedrate based on the actual spindle load. Additionally, integration of the iAdapt S productwithin the CNC now eliminates the need for mounting space, simplifying installation whileimproving the capabilities of the original iAdapt product.The original iAdapt product introduced the concept of roughing cycle productivity to CNCcustomers. The ―On Demand‖ control feature simplified the use of the adaptive control bymaking it easy to setup and operate.The new iAdapt S has an arsenal of improvements which allows the operator to improvemachine cycle time and tool life. By automatically optimizing the cutting feedrate based on theactual spindle load, iAdapt S improves material removal and minimizes cycle time. In fact,productivity is increased as cycle times are reduced by up to 40% as every part is automaticallyoptimized in real-time, including the first. iAdapt S compensates for material and processvariations including: material hardness, tool wear, depth of cut and width of cut. Additionally,feedrate control is 100 times finer which increases the responsiveness and accuracy of theadaptive control. To view and improve the machining process, a graphing feature has beenadded, which displays both the spindle load and feedrate override versus time. A new 64-entrysetting table has been introduced in iAdapt S which allows easy saving of settings for later useand recall. A new Torque Override feature has been added to allow the operator to dynamicallymodify the adaptive control set point during the machining cycle.Additionally, iAdapt S keeps roughing tools fully loaded, putting the heat into the chips ratherthan the part, thus extending tool life. As a result, there are fewer minor stoppages,which increases productivity and reduces labor costs.Fanuc Corporation, headquartered at the foot of Mt. Fuji, Japan, is a diversified manufacturer ofFactory Automation (FA), Robots and Robomachines. Since its inception in 1956, Fanuc hascontributed to the automation of machine tools as a pioneer in the development of computernumerical control equipment. Fanuc is committed to developing efficient, reliable and innovativeproducts.Fanuc FA America is the exclusive provider of industry leading Fanuc CNC systems andsolutions in the Americas, providing a one-stop shop for comprehensive CNC solutionsincluding industry-leading control systems, a complete range of drives and motors and CO2 lasersolutions. Fanuc FA America also offers engineering support, genuine parts, repair and factoryautomation solutions and training programs to machine tool builders, dealers and users. FanucFA America has headquarters in Hoffman Estates, IL, and supports 37 offices and service centersin the U.S., Canada, Mexico, Brazil and Argentina.
www.fanucfa.comhttp://www.controleng.com/channels/machine-control.htmlPatent for CNC adaptive control systemFanuc Factory Automation America (Fanuc FA America)received a patent for developing on-demand integratedadaptive control for their CNC control system.06/05/2012Fanuc Factory Automation America ( Fanuc FA America) and Jerry Scherer, engineerwith Fanuc FA America, have been awarded a patent for the development of their CNCAdaptive Control System for on-demand integrated adaptive control of machining operations.This system was developed to increase machine tool productivity with Fanuc FA AmericasiAdaptS adaptive control solution.Fanuc FA Americas patented CNC Adaptive Control System measures the present value of thespindle load and then compares this value to a present value of a target spindle load. Theadaptive controller is configured to control the feed rate of the machine tool relative to theworkpiece to maintain the present value of the spindle load approximately equal to the presentvalue of the target spindle load using one or more calculations of the first feed rate value, thefirst feed rate dither adjustment value and the second feed rate dither adjustment value.This CNC adaptive control system is the base technology in Fanuc FA Americas iAdaptSsolution that improves material removal and minimizes cycle time by automatically optimizingthe cutting feedrate based on the actual spindle load. Additionally, integration of the iAdaptSsoftware solution within the CNC now eliminates the need for mounting hardware, simplifyinginstallation while improving the capabilities of the original iAdapt product. The original iAdaptproduct introduced the concept of roughing cycle productivity to CNC customers. The "OnDemand" control feature simplified the use of the adaptive control by making it easy to setup andoperate. iAdaptS extends tool life by keeping roughing tools fully loaded, putting the heat intothe chips rather than the part. As a result, there are fewer minor stoppages which furtherincreases productivity and reduces labor costs.Fanuc Factory Automation Americawww.fanucfa.com- Edited by Chris Vavra, Control Engineering, www.controleng.comAlso see controleng.com/machinecontrol
Related News: Real-time diagnostics system for micromilling - 11.07.2012 21:12 PLC-controlled robotic case packing, unpacking - 04.10.2011 23:13 PC-based Control, Robotics Help Packaging - 19.09.2011 17:22 Computer Numerical Control: CNC Faceoff - 13.07.2011 11:20 CNC integrates adaptive control to add productivity - 06.07.2011 03:57 CNC outlook: making tracks in midrange products - 28.06.2011 19:32Real-time diagnostics system formicromillingControl Engineering International: Tool conditionmonitoring is important for quality of micromillingprocesses and can be improved with a real-time diagnosticssystem. Diagnostic signals selection, tool wear inspectionalgorithm, and proper measuring system selection all help.Testing and validation were completed in operatingconditions.Bogdan Broel-Plater, Krzysztof Pietrusewicz, Paweł Waszczuk07/11/2012ShareWith wider use of miniature components in all industries, attention to quality in micromilling ofvarious materials has become more important. A real-time diagnostics system for micromillingallows tool condition monitoring and improves metal component production quality. Amonitoring system ensures accuracy, quality, and most of all, microcutting process stability.
Selecting a proper signal that provides the best information about process conditions is crucial.Due to availability, simplicity of use, and price, accelerometers are the most common sensingchoice. Sensors placed in key areas of a micromilling machine ensure that an acceleration signalprocessing algorithm can create reliable and useful information about the process.It’s also important to measure microcutting process cutting forces. Because of the nature ofmicromilling, cutting force amplitude can be very low (<1N) and hard to measure. Likeinformation about vibration, cutting force information is extremely helpful for diagnostics. Measurements, diagnosticsSelecting an appropriate measuring system is an important issue during development of adiagnostics system. A real-time diagnostics system for micromilling was created based onNational Instruments hardware and software: cRIO-9022 PAC controller and analog moduleswith dynamic signal acquisition for making high-accuracy frequency measurements from anintegrated electronic piezoelectric (IEPE) accelerometer. The controller includes a reconfigurablefield-programmable gate array (FPGA) chassis, which allows analog signal acquisition up to51.2 kHz. Data are filtered then processed in real time to provide determinism and stability of themonitoring algorithms. Depending on need, acquired data can be written on a device’s hard drive
or visualized by the user interface panel on a computer screen. Additionally, the system cancommunicate with the micromilling machine drives controller.Thanks to the flexibility of the measurement equipment used, a monitoring system was createdand specially adapted for microcutting processes. The FPGA module and LabVIEW Real-TimeSystem allow development of deterministic data acquisition and data processing algorithms.As for other technologies, motion control uses Aerotech linear nano-modules (250 ns movementresolution); force measurement is based on Kistler dynamometer for small forces; and PCBPiezoelectronics is used for acceleration measurement.The main assumption of the diagnostic procedure was to process obtained signals using an FFTalgorithm. An inspection program based on rotational speed of the electric spindle observedadequate spectrum section of acceleration and cutting force signals at all three axes. In case ofadditional frequencies near the excitation frequency, the monitoring algorithm immediatelyinforms the operator via the user interface panel and sends appropriate notification to themicromilling machine drives controller.During microcutting operations, the device’s hard drive stores data to analyze all diagnosticsignal variations. If necessary, a quick implementation of new algorithms is possible, to gainmeasurement variety. Relatively small dimensions and rugged design permit use in a wide rangeof applications.18,000 rpmTo test the real-time diagnostics system for micromilling, a set of experiments on carbon steel18G2 and two-bladed, 0.61mm diameter tool was prepared. Spindle rotational speed was set to18,000 rpm, with step size of 6 µm and milling depth of 10 µm. Accelerometers were attached tothe electro spindle, based on prior experiments. A 3-axis dynamometer was placed on the verticalaxis of the micromilling machine. The work piece was attached on top of the dynamometer.Experiments were performed for five tool passes through the entire work piece, during which thetool condition was monitored. Before and after every operation, tool images were made using adigital microscope (500X magnification).
During experiments,significant degradation of the tool and surface quality deterioration were observed. Powerspectrum analysis of recorded acceleration and cutting force signals shows a similar relationship.Figure 3 compares diagnostic signal power spectrum graphs of a new and a worn tool. Theexcitation frequency of spindle rotational speed (600 Hz) is clearly dominant. In the case of aworn tool, additional undesirable frequencies occur, indicating damaging vibrations that canhave a negative impact on micromilling process quality.The real-time diagnostics system developed for micromilling is an interesting solution for anyapplication where accuracy and improved quality are required. Due to modularity, it can bequickly reconfigured to fit various conditions. Small dimensions and ruggedness allow use in awide range of applications. The intuitive user interface can be adapted to operator needs.Implementing a real-time diagnostics system for micromilling in industrial applications helpssave time and money.- Bogdan Broel-Plater, Krzysztof Pietrusewicz, and Paweł Waszczuk are with West PomeranianUniversity of Technology, Control Engineering Poland. Edited by Mark T. Hoske, contentmanager CFE Media, Control Engineering and Plant Engineering, mhoske(at)cfemedia.comwww.controlengpolska.com
Szczecin University of TechnologyONLINE extra - More about the authors- Bogdan Broel-Plater, PhD, is with the West Pomeranian University of Technology, Szczecin,Faculty of Electrical Engineering. His research work involves artificial intelligence utilizationwithin the digital control and supervision systems.- Krzysztof Pietrusewicz, PhD, is with the West Pomeranian University of Technology, Szczecin,Faculty of Electrical Engineering. He is also an editor for Control Engineering Poland. Hisresearch work involves robust open architecture controls and integrated condition monitoringapproach for machine tools.- Paweł Waszczuk, PhD student, is with the West Pomeranian University of Technology,Szczecin, Faculty of Electrical Engineering. His research interests include real-time conditionmonitoring systems for machine tools as well as micromilling.Related News: Domestic machine tool manufacturer facility expansion drives new opportunities - 17.08.2012 12:17 Technologies used: Motion control system for Boeing 787 assembly - 06.07.2012 09:50 Patent for CNC adaptive control system - 05.06.2012 10:59 Five control market trends for 2012 - 30.05.2012 13:00Domestic machine tool manufacturer facilityexpansion drives new opportunitiesBrian Papke, president of Mazak Corp., talks about how alarge expansion to the companys Florence, Ky. facility isdriving new opportunities for the company in the U.S.08/17/2012Share
Mazak Corp. has announced a large expansion of its Florence, Ky., manufacturing facility tohandle the rapid growth in the domestic machine tool business. Brian Papke, president of MazakCorp., talks about how that growth is driving new opportunities for the company in the U.S.PE: What have the last three years been like for Mazak? Have you been able to invest inR+D while serving the existing customer base?Papke: Our incoming orders in 2010 were up 100%, last year up 60% (on a calendar year basis),and this year are up 20% thus far. Also during the past 3 years, we continued to develop new,innovative products, as opposed to simply meeting the increases in demand with existing oldermachine models.During the downturn prior to the manufacturing upswing, we continued to reinvest in our factoryand in our R+D resources to ensure that we could competitively produce new products that werereceptive to the market when the economy was back on track in 2010. Even though business isnow good for most manufacturers, they must still strengthen their competitiveness, and doing sorequires truly new, innovative, and productive equipment, not technology that’s as much as 5years old.And Mazak, like other manufacturers, is under the same pressure, which is why we continuallyimprove our technology and invest in new equipment for our own production-on-demandmanufacturing operations to increase our productivity and competitiveness. Our customers, likeus, want the latest and greatest technology that will increase their productivity better thananything else on the market and better than what their competitors are using.A favorable business climate doesn’t imply that a company will automatically be successful. Youstill have to be competitive or you will lose that success. Our customers are very receptive to theproducts we develop because they consistently provide more productivity and a competitiveadvantage.PE: As IMTS approaches, what are you hearing from your customers about what theyneed to continue to grow their business?Papke: As IMTS approaches, our customers are seeking new technology that will give them thecompetitive advantage and improve their business. Additionally, they are quite concerned withhow those products will help reduce the labor content in operations—not in an effort tonecessarily reduce labor costs, but instead to improve production without increasing theirdependency on skilled labor.To reduce their reliance on skilled labor, manufacturers are also seeking to automate as manyoperations or processes as possible. Such automation can take different forms besides thecommonly thought-of stand-alone robot. For instance, a multitasking machine combines enoughdifferent processing capability that, in itself, automates production because parts are loaded inthe machine once and come out completed.PE: Conversely, what do they say are the barriers to growing their business?
Papke: The biggest barrier to our customers’ abilities to grow is the current lack of skilled labor.Recruiting, training, and maintaining skilled employees on an ongoing basis are provingincreasingly challenging for these manufacturers. Therefore, we continue to strengthen ourefforts in providing not only highly productive machines and fully automated solutions that willease the need for skilled labor, but also providing customers with various training programs aspart of our Pyramid of Learning and through our regionally located technology centers.PE: Mazak is a global company. What are the secrets to being both global and local today,and why is that of benefit to manufacturing?Papke: There is really no big secret, except for the fact that a company has to be committed.Being a successful company on both a global and local level simply takes a strong commitmentto being where your customers are and having a well-established presence in those areas.We are not only a company that sells machine tools, but one that also works closely with itscustomers to develop complete turnkey manufacturing solutions that provide them the lowestpossible cost of ownership and the fastest return on their investment. But equally important,these solutions optimize their operations and increase equipment utilization rates.In the machine tool business, those who survive, prosper, and grow over long periods of time arethe ones that are completely committed to providing innovative technology and unmatchedcustomer support. Ultimately, our desire is to always have our customers tell us that they’veimproved their profitability as a result of investing in Mazak equipment. We want them to growand prosper, and in the process, we want to grow as partners with them.Related News: Mid-Year Report: Bullish on manufacturing - 20.08.2012 08:00 Packaging machinery initiatives - 08.08.2012 09:47 Using 3D to deliver a new view of manufacturing - 07.08.2012 11:03 Real-time diagnostics system for micromilling - 11.07.2012 21:12
http://www.slideshare.net/guestac67362/adaptive-control-systems-paper-presentationAdaptive Control Systems Paper Presentation — DocumentTranscript 1. www.studentyogi.com www.studentyogi.com co om Adaptive control system with knowledge server system m in CNC system gi. .c oogi ntyy eent ADAPTIVE CONTROL SYSTEM WITH KNOWLEDGE t t dd SERVER IN INTELLEGENT CNC SYSTEM ssuu w. . w ABSTRACT: ww ww In an ideal scenario of intelligent machine tools the human mechanist was almost replaced by the controller. During the last decade many efforts have been made to get closer to this ideal scenario, but the way of information processing within the CNC did not change too much. The paper summarizes the requirements of an intelligent CNC evaluating the advancement of technology in this field using different adaptive control systems. In this paper a low cost concept for artificial intelligence named www.studentyogi.com www.studentyogi.com 2. www.studentyogi.com www.studentyogi.com Knowledge Server for Controllers (KSC) is introduced. It allows more devices to solve their intelligent processing needs using the same server that is capable to process intelligent data. The KSC concept is used in an open CNC environment to build up an intelligent CNC. om Key words: Intelligent CNC, knowledge server, adaptive control systems i.c og nty de 1. INTRODUCTION: stu There are many definitions of the intelligent machine tools. In a well known book Wright and Bourne said that ―We must therefore acknowledge that the degree of intelligence can be gauged by the complexity of the input and/or the difficulty w. of ad hoc in-process problems that get solved during a successful operation. Our unattached, fully matured intelligent machine tool will be able to manufacture accurate aerospace components and get a good part right the first time‖. They told that an ww intelligent machine tool had the CAD data, the materials and the set-up plans as inputs and could produce correctly machined parts with quality control data as outputs. 2 It is clear that adaptive control techniques are necessary to apply if one wants intelligent CNC machine, but - of course - the usage of them is not adequate in intelligent behavior. www.studentyogi.com www.studentyogi.com 3. www.studentyogi.com www.studentyogi.com Table 1 summaries the features of an intelligent CNC (Wright and Bourne collected them more than ten years ago) and shows two further things: the positive changes done in the recent years and the still existing gaps where - according to the scientific community – adaptive control systems offers solutions with its information om processing methods. Analyzing the above list, it is clear that many features do not require direct adaptive control methods. We can state that the main reasons of the advancement were: i.c (1) The development of the hardware elements (more sensitive sensors, more precise actuators, quicker and stronger computers etc.) even in higher requirements. og (2) The development of the software and the methodology mainly in the preparation phases of the manufacturing (in design, planning, scheduling, resource management etc.) and in the user interface issues (more comfortable and informative windows-like screens nty and Menus). de Table 1. Commercial needs
for the intelligent machine tools: stu Features (forecasted in 1988) Big Artificial advanceintelligence by 2001 methods still needed w. 1. Reduce the number of scrap partsfollowing initial setup. ww 2. Increase the accuracy with which parts are made. 3.Increase the predictability of machine tool operations. 4. Reduce the manned operationsin the machine tool environment. www.studentyogi.com www.studentyogi.com4. www.studentyogi.com www.studentyogi.com 5. Reduce the skill level required formachine setup and operations. 6. Reduce total costs for part fabrication. om 7. Reducemachine downtime. 8. Increase machine throughput. 9. Increase the range of materialsthat can be both setup and i.c machined. 10. Increase the range of possible og geometriesfor the part 11. Reduce tooling through better operation planning nty 12. Reduce numberof operations required for setup 13. Reduce setup time bydesigning parts for ease of setupde 14. Reduce the time between part design and fabrication stu 15. Increase the quantityof information between the machine 16. control and part design w. operations ww Eventhere is a big advance in the technology of the CNCs, the Knowledge processing andother adaptive control methods have not appeared within the Intelligent Open CNCSystem Based on the Knowledge Server Concept 3controllers, so in some points there isno real development. Special heuristic rules, problem-solving strategies, learningcapabilities and knowledge communication features are still missingwww.studentyogi.com www.studentyogi.com5. www.studentyogi.com www.studentyogi.com from the recent controllers available onthe market. It is also true for many new, open or PC-based CNC s, where DSP add-on-boards provide the necessary computation power and speed. Further requirements ofintelligent CNC s can be find out and defined. (Table 2.): The second column indicateswhether the different adaptive control om techniques (mainly rule base systems, neuralnets and fuzzy logic) would provide methods and solutions. One can find positiveanswers to all these issues in the resent literature: i.c og nty de Table2. Futurerequirements of an intelligent CNC: stu Table 2. Future requirements of an intelligentCNC w. Further features Artificial intelligence methods ww would helpwww.studentyogi.com www.studentyogi.com6. www.studentyogi.com www.studentyogi.com • Model based on-line path generation •Automatic tool selection • Technological based settings of the operational parameters •Automatic compensation of machine limits • Automatic back-step strategies om •Detection and compensation of geometrical deflection • On-line selection of controlalgorithms • Intelligent co-operation with other devices to solve problems i.c together •Detection and correction of tool wear and breakage • Automatic handling of rejectedwork pieces og • Detection and managing of emerging situations of the machine tool •Complex self-diagnostics nty The list may be continued with the learning capabilities andothers. In the users point of view these features rough in a controller, that "recognizes theproblem" and de "efficiently and reasonable solves them" with minimal disturbance ofthe environment of the controller. stu w. 2. RESULTS IN INTELLIGENT CNC s: wwOn the one hand in the recent literature one can find many different topics related tointelligent CNCs. Unfortunately they often do not mean intelligent behaviors but theapplication of intelligent methods. Sometimes it is the case that authors call their devices―intelligent" if one module of the system contains based method. On the other hand (2)the key controller vendors leave everything to the users or machine tool builders offering
PC/Windows based CNCs. With these systems any software modules (e.g. evenwww.studentyogi.com www.studentyogi.com7. www.studentyogi.com www.studentyogi.com adaptive control based ones) can becoupled into the controller but they do not offer J real solutions or methodologies, butonly software possibilities. The following list summarizes the most important activeresearch topics in this field. A real intelligent CNC would contain most of these issues.om 1) Fuzzy logic based concurrent control of some operating parameters (E.g. cuttingspeed, depth of cut, feed rate) independently from the Given tool and the work piece. i.c2) Neural nets and fuzzy rules in the CNCs control algorithms. Optimal path planning,real-time correction of the trajectory. 3) og 4). Compensation of temperature (and other)deformations. Life time management of the tools and other parts of the machine 5) Toolincluding self-diagnostics. nty 6) Tool breakage detection (maybe forecasting) and toolwear Monitoring (maybe compensation) with AI methods. 7) The utilization of CNCmanagement (setup, orders, etc.) via Intelligent agents. de Intelligent parts of a CNC canbe classified into three groups, namely: stu (1) Tool monitoring, (2) operation/machinetool modeling and (3) Adaptive control. w. A general problem in all the three groups isthat the adaptive control based solutions are typically limited and valid only in a verynarrow field. If one changes some parameters of the operation or the environment, theearlier successful methods become ww false. A special type of adaptivity partly helps onthis hard and well-known problem. If it is possible to replace the different modules of thecontroller time by time, than one can guarantee, that a given adaptive control module canrun within its limitation, and over it another module (e.g. a much simpler one) covers thesame functionality. It can be realized (among others) if the controller is open to allow thisreplacement. www.studentyogi.com www.studentyogi.com8. www.studentyogi.com www.studentyogi.com 3. Adaptive Control System : Inadaptive control, the operating parameters automatically adapt themselves to conform tonew circumstances such as changes in the dynamics of the particular process and anyarise. The adaptive would check load conditions, adapt an appropriate desired braking omprofile (for ex: antilock brake system and traction control), and then use feed back toimplement it. With advanced adaptive controllers the gain may vary continuously withchanges in operating condition. i.c Purpose of adaptive control: 1. to optimize productionrate 2. to optimize product cost og 3. to minimize cost The functions common to adaptivecontrol systems are the following: 1. Determine the operating conditions of the process,including measures of nty performance. Thos typically achieved by using sensors whichmeasure process parameters (such as force, torque, vibration, and temperature). 2.Configure the process control in response to the operating conditions. Large changes dein the operating conditions may provoke a decision to make a major switch in controlstrategy. More modest alterations may be the modifications of process parameters (suchas changing the speed of operation or the feed in manufacturing). stu 3. continue tomonitor the process, making further changes in controller when and As needed. In anoperation such as turning on lathe, the adaptive control system senses real – w. timecutting forces, torque, temperature, tool-ware, tool chipping or tool fracture, and surfacefinish of the work piece. The system then converts this information into commands thatmodify the process parameters on the machine tool to hold them ww constant (or with incertain limits) or to optimize the cutting operation. 4. DIFFERENT APPROACHES OFKNOWLEDGE SERVERS: www.studentyogi.com www.studentyogi.com
9. www.studentyogi.com www.studentyogi.com The features of World Wide Web led tointroduce knowledge server to easier solve the installation and version control problemsof expert systems and to provide a web based interface of the knowledge base for thedifferent users. Some advanced knowledge based systems are based on this concept.There are some applications of knowledge servers in manufacturing. In the HPKB (HighPerformance Knowledge Environment) om some hundred thousand rules are performedin an intelligent knowledge environment. In this project the different intelligentcomponents are called knowledge servers. The components are communicating with eachother via the OKBC (Open Knowledge Base Connectivity) protocol specified at Stanford.i.c On communication networks, the protocol named MAP uses a bus configuration,broad band transmission, a token passing access scheme and data Transmission rate of og10mbps. MAP is based on specification defined by the identical standard organizations(ISO) called the open system interconnection (OSI) reference model. nty The seven layerstructure of MAP standard the first four layers are connected with the inter connectionfunctions, and the top three layers are connected with inter working functions. Theapplication layer (seventh layer) is the highest layer in MAP at the time of de this writing.It is possible that this layer may be sub divided into multiple layers as applications ofcommunication protocol and computer techniques evolve in future. stu w. ww 5.KNOWLEDGE SERVER FOR CONTROLLERS: Knowledge Server for Controllers(KSC) is defined as a server providing capability of intelligent data processing for othersystems. It allows the basic system to reach external intelligent processing resources,because it does not have any. The KSC contains a high performance reasoning tool, anddifferent knowledge based modules. All www.studentyogi.com www.studentyogi.com10. www.studentyogi.com www.studentyogi.com the modules have their special rulesand procedures. The client system calls these modules, passes them specific data ifnecessary, and the KSC module can collect data if the knowledge processing requires. Allthe data acquisition and user interaction is done by the client system. It is clear that inKSC the clients have much more tasks than a simple browser based user interface and inthe applications listed in the previous chapter. om It should be stated that KSC does notdeal with fuzzy and neural net based adaptive control modules. The computing power andthe necessary software costs and complexity of these methods are less than the rule ormodel based ones. (In the case of the neural nets it is true only if the net is not trained on-line.) . i.c The KSC allows the different modules to run independently, to cooperate asagents or to control each other. The third case means that one module is started byanother one og because either the second one uses the results of the first one or theinference of the first one led to the need of the second module. Generally the resources ofthe KSC can use more clients (controllers) nty simultaneously. It leads to a cost effectiveAI solution, because one costly AI tool can solve all the intelligent problems in adistributed environment. The overhead of the KSC (network connection, one morecomputer, some delay etc.) is much less comparing to the advantages (adaptive controltool licensing, less computing power in the de clients/controllers, one server module mayused by more clients etc.). Using the KSC together with the component based softwaretechnology (e.g. stu CORBA) gives a very adaptive software frame to solve complexproblems. In the Fig. 1 a CNC with an embedded PLC controls a machine tool. Themodules of both controllers are open and some of them are also clients of a knowledgeserver (KSC). It means that these modules can run special adaptive control Intelligent
Open w. CNC System Based on the Knowledge Server Concept methods during theirwork that is an independent service is implemented in the KSC. wwwww.studentyogi.com www.studentyogi.com11. www.studentyogi.com www.studentyogi.com om i.c og nty 6. PROTOTYPEINTELLIGENT CNC BASED ON KSC: In an early prototype of the intelligent openCNC that is using KSC, Adaptive de control system was implemented An advance axistester is put on the top of this. Axis Test module handles all the tests but it gets thenecessary position and velocity values from a stu knowledge based general tester runningas an application on the KSC. The KB tester determines some goal positions and motionspeeds, that the Axis Test module executes with the axis using jog commands. The results(execution time, tuning in errors etc.) are w. sent to the KSC that analyses and qualifiesthe axis. In the prototype the modules are built in CORBA, the controller and the HMI isprogrammed in Java. ww www.studentyogi.com www.studentyogi.com12. www.studentyogi.com www.studentyogi.com 7. CONCLUSIONS: The controllableparameters in machining by using micro controller i.e. adaptive om control system arecutting force, torque, vibrations, feed and depth of cut. The controllable parameters inmachining by using artificial intelligenceModel based on-line path generation •Automatic tool selection i.c • Technological based settings of the operational parameters •Automatic compensation of machine limits og • Automatic back-step strategies •Detection and compensation of geometrical deflection • On-line selection of controlalgorithms nty • Intelligent co-operation with other devices to solve problems together •Detection and correction of tool wear and breakage • de Automatic handling of rejectedwork pieces • Detection and managing of emerging situations of the machine tool Byintroducing an interface between micro controller of adaptive control system stu and thedata base of artificial intelligence we can control all the above parameters bycommunicating with knowledge server. The features of KSC were discussed and an earlyprototype was introduced. w. References: ww Adaptive control system -------- Bernardwplrow,Samuel D.stearns Manufactureing Engg and technology by Serope Kalpak Jain,Steven R. schmid Computer integrated manufacturing---------------- James A Regh, Henryw scrab Manufacturing system Engg -------------------- katsundo Hitoniwww.studentyogi.com www.studentyogi.com
http://my.safaribooksonline.com/book/manufacturing/9780132441889/computer-controls-in-nc/ch09lev1sec7#X2ludGVybmFsX0ZsYXNoUmVhZGVyP3htbGlkPTk3ODAxMzI0NDE4ODklMkZjaDA5bGV2MXNlYzg=9.7. Adaptive Control Machining SystemsAdaptive control (abbreviated AC) machining originated out of research in the early 1960ssponsored by the U.S. Air Force at the Bendix Research Laboratories. The initial adaptivecontrol systems were based on analog control devices, representing the state of technology at thattime. Today, AC uses microprocessor-based controls and it is typically integrated with anexisting CNC system. Accordingly, the topic of adaptive control is appropriate to include in thischapter on computer controls in NC.For a machining operation, the term adaptive control denotes a control system that measurescertain output process variables and uses these to control speed and/or feed. Some of the processvariables that have been used in adaptive control machining systems include spindle deflectionor force, torque, cutting temperature, vibration amplitude, and horsepower. In other words,nearly all the metal-cutting variables that can be measured have been tried in experimentaladaptive control systems. The motivation for developing an adaptive machining system lies intrying to operate the process more efficiently. The typical measures of performance in machininghave been metal removal rate and cost per volume of metal removed.Where to use adaptive controlOne of the principal reasons for using numerical control (including DNC and CNC) is that NCreduces the nonproductive time in a machining operation. This time savings is achieved byreducing such elements as workpiece handling time, setup of the job, tool changes, and othersources of operator and machine delay. Because these nonproductive elements are reducedrelative to total production time, a larger proportion of the time is spent in actually machining theworkpart. Although NC has a significant effect on downtime, it can do relatively little to reducethe in-process time compared to a conventional machine tool. The most promising answer forreducing the in-process time lies in the use of adaptive control. Whereas numerical controlguides the sequence of tool positions or the path of the tool during machining, adaptive controldetermines the proper speeds and/or feeds during machining as a function of variations in suchfactors as work-material hardness, width or depth of cut, air gaps in the part geometry, and so on.Adaptive control has the capability to respond to and compensate for these variations during theprocess. Numerical control does not have this capability.Adaptive control (AC) is not appropriate for every machining situation. In general, the followingcharacteristics can be used to identify situations where adaptive control can be beneficiallyapplied:
Sources of variability in machiningThe following are the typical sources of variability in machining where adaptive control can bemost advantageously applied. Not all of these sources of variability need be present to justify theuse of AC. However, it follows that the greater the variability, the more suitable the process willbe for using adaptive control. 1. Variable geometry of cut in the form of changing depth or width of cut. In these cases, feed rate is usually adjusted to compensate for the variability. This type of variability is often encountered in profile milling or contouring operations. 2. Variable workpiece hardness and variable machinability. When hard spots or other areas of difficulty are encountered in the workpiece, either speed or feed is reduced to avoid premature failure of the tool. 3. Variable workpiece rigidity. If the workpiece deflects as a result of insufficient rigidity in the setup, the feed rate must be reduced to maintain accuracy in the process. 4. Toolwear. It has been observed in research that as the tool begins to dull, the cutting forces increase. The adaptive controller will typically respond to tool dulling by reducing the feed rate. 5. Air gaps during cutting. The workpiece geometry may contain shaped sections where no machining needs to be performed. If the tool were to continue feeding through these so- called air gaps at the same rate, time would be lost. Accordingly, the typical procedure is to increase the feed rate by a factor or 2 or 3, when air gaps are encountered.Two types of adaptive controlIn the development of adaptive control machining systems, two distinct approaches to theproblem can be distinguished. These are: 1. Adaptive control optimization (ACO) 2. Adaptive control constraint (ACC)Operation of an ACC SystemTypical applications of adaptive control machining are in profile or contour milling jobs on anNC machine tool. Feed is used as the controlled variable, and cutter force and horsepower areused as the measured variables. It is common to attach an adaptive controller to an NC machinetool. Numerical control machines are a natural starting point for AC for two reasons. First, NCmachine tools often possess the required servomotors on the table axes to accept automaticcontrol. Second, the usual kinds of machining jobs for which NC is used possess the sources ofvariability that make AC feasible. Several large companies have retrofitted their NC machines toinclude adaptive control. One company, Macotech Corporation in Seattle, Washington,specializes in retrofitting NC machine tools for other manufacturing firms. The adaptive controlretrofit package consists of a combination of hardware and software components. The typicalhardware components are: 1. Sensors mounted on the spindle to measure cutter deflection (force).
2. Sensors to measure spindle motor current. This is used to provide an indication of power consumption. 3. Control unit and display panel to operate the system. 4. Interface hardware to connect the AC system to the existing NC or CNC control unit.Benefits of adaptive control machiningA number of potential benefits accrue to the user of an adaptive control machine tool. Theadvantage gained will depend on the particular job under consideration. There are obviouslymany machining situations for which it cannot be justified. Adaptive control has beensuccessfully applied in such machining processes as milling, drilling, tapping, grinding, andboring. It has also been applied in turning, but with only limited success. Following are some ofthe benefits gained from adaptive control in the successful applications. 1. Increased production rates. Productivity improvement was the motivating force behind the development of adpative control machining. On-line adjustments to allow for variations in work geometry, material, and tool wear provide the machine with the capability to achieve the highest metal removal rates that are consistent with existing cutting conditions. This capability translates into more parts per hour. Given the right application, adaptive control will yield significant gains in production rate compared to conventional machining or numerical control. The production rate advantage of adaptive control over NC machining is illustrated in Table 9.1 for milling and drilling operations on a variety of work materials. Savings in cycle time reported in this table range from 20% up to nearly 60% for milling and 33 to 38% for drilling. Table 9.1. Comparison of Machining Times—NC versus Adaptive Control Work NC Percent Operation Description material time AC time saving Profile Aircraft flap ribs Aluminum 152 min 81 min 46 milling Profile Aircraft flap ribs Aluminum 641 min 319 50 milling min Profile Aerospace component Stainless steel 9.6 h 7.5 h 22 milling Profile Aerospace component Stainless steel 11.8h 9.4 h 20
Table 9.1. Comparison of Machining Times—NC versus Adaptive Control Work NC Percent Operation Description material time AC time saving milling Profile Space shuttle engine ring Inconel 718 35 milling Profile Engine Mounting ring Inconel 718 45 milling Profile Aircraft component Titanium 64 min 35 min 48 milling End milling Aerospace component 4330 Steel 61 min 25 min 59 Drilling 0.433″ diameter × 1.0″ deep 1019 Steel 8s 5s 38 Drilling 0.433″ diameter × 1.75″ Cast iron 10.5 s 7s 33 deep Source: Data courtesy of Macotech Corp.2. Increased tool life. In addition to higher production rates, adaptive control will generally provide a more efficient and uniform use of the cutter throughout its tool life. Because adjustments are made in the feed rate to prevent severe loading of the tool, fewer cutters will be broken.3. Greater part protection. Instead of setting the cutter force constraint limit on the basis of maximum allowable cutter and spindle deflection, the force limit can be established on the basis of work size tolerance. In this way, the part is protected against an out-of- tolerance condition and possible damage.4. Less operator intervention. The advent of adaptive control machining has transferred control over the process even further out of the hands of the machine operator and into the hands of management via the part programmer.5. Easier part programming. A benefit of adaptive control which is not so obvious concerns the task of part programming. With ordinary numerical control, the programmer must plan the speed and feed for the worst conditions that the cutter will encounter. The
program may have to be tried out several times before the programmer is satisfied with the choice of conditions. In adaptive control part programming, the selection of feed is left to the controller unit rather than to the part programmer. The programmer can afford to take a less conservative approach than with conventional NC programming. Less time is needed to generate the program for the job, and fewer tryouts are required.9.8. Trends and New Developments in NCWe will conclude these three chapters on numerical control by discussing some of the importanttrends and new developments in NC technology. Without question, the most important generaltrend in NC involves the expanding use of computer technology. The use of computers hasalready provided significant improvements in part programming procedures (e.g., computer-assisted programming, interactive graphics, and voice programming). The control of NCmachinery has also been dramatically enhanced through computer technology (e.g., CNC, DNC,and adaptive control). We have covered these topics in Chapter 8 on programming and in thecurrent chapter on computerized NC. In the following sections, we discuss some additionaltopics likely to influence the future evolution of numerical control. http://www.moldmakingtechnology.com/articles/optimize-cnc-machining-with-add-on- adaptive-controlsOptimize CNC Machining With Add-OnAdaptive ControlsThe use of CNC adaptive controls can help moldmakers not only reduce cycle times, but alsoextend the life of their cutting tools.While CNC technology coupled with CAD/CAM has long helped to introduce flexibility inbatch production, there still remain some major inefficiencies inherent in most machiningprocesses.Present day CNC technology relies on the programmers input of appropriate cutting parameters -even when sophisticated software systems are used to generate NC programs. The fact is that NCprogramming is based on predetermined and unchanged conditions.The control mechanisms of CNC machines are limited to geometry and kinematics. As such,they follow pre-programmed and constant speed and feedrates during each cutting segment.Consequently, they do not have the flexibility required for adapting to the dynamic changes thatoccur during cutting. This inflexibility would be acceptable if cutting conditions were uniform
during machining. In practice, however, cutting conditions tend to continuously vary for many ofthe following reasons: Uneven workpiece surface. Gradual tool wear. Material hardness varies within each workpiece. Workpiece dimensions vary from piece to piece. Temperature variations in material during cutting. The fixtures stability may be affected during cutting. NC programs may contain errors.Advances in CAD/CAM technology have caused machinists to focus most of their attention to"defining the required geometry" and ignore the need to consider the rest of the previouslymentioned conditions. However, with all of the those deviations in mind, NC programmers haveno alternative but to be conservative in determining cutting parameters - resulting in safer butmore inefficient cutting processes. No matter how optimized NC programs may be, they cannottake into account these dynamic variations encountered during cutting. At best, long NCprograms may be created with different feedrates for each segment. However, these programsstill cannot modify cutting parameters in real time in order to adapt to unexpected conditions thatmay occur during cutting.Dynamic Optimization SolutionCNC machining can be fully optimized through the implementation of add-on adaptive controlsystems, which continuously monitor cutting conditions in real time. Such optimization andmachine automation technology systems are indispensable if expensive CNC machines are everto run at their full capacity and if cutting tools are to be utilized up to their maximum life ratherthan incurring in-process catastrophic breakage and production disruption. Similarly, machineoperators will not be required to intervene in the machining process to watch and manually fine-tune the process. In this way, true automation is made a reality and programmers may be moreaggressive, knowing that the adaptive controls will adjust the feedrate based on the load.Manufacturers require optimization features that can be added on to their existing CNCmachinery. Add-on adaptive control systems connect directly to the CNC machine controller;sense and monitor actual cutting load conditions; and adjust feedrates to optimal levels in realtime. This ensures a constant cutting load, which takes into account the variations in the cuttingconditions during the cut. In this way, these systems ensure that machine cycle times areminimized and that the machines run at the maximum permissible capacity for each tool.One of the most attractive features of these systems is that they apply the optimal feedrate in realtime based on the most basic parameters for each specific tool and material. These parametersmay be input, if necessary, from an external tool library. The operator is not required to knowspecific load threshold for each tool, as the internal expert system determines these limits foritself.
This enhancement allows NC programmers to be aggressive and program feeds as though thetools are new and sharp. During cutting, the adaptive controls automatically compensate for toolwear since feedrates are automatically and continuously adjusted partly as a function of theextent of tool wear. The system also gives operators a quantitative indication of tool wear duringthe cut. Based on the systems indication, operators can get ready to replace the worn tools intime without actually incurring costly and disruptive tool breakage or replacing the tool muchsooner than necessary.In addition to detecting tool wear, the devices also protect tools from breakage through theirsensitivity to the spindle load. Fewer broken tools also reduce scrap and the need for rework.Breakage protection is provided in the form of an alarm system that alerts the machineoperator/supervisor when acute overload conditions occur in the cutting process and, ifnecessary, automatically stops the machine.Adaptive control systems ensure automatic optimization of the machining process to reducecycle times, increase tool utilization and prevent tool breakage, thus lowering machining costsand increasing machine capacity.These adaptive control systems are applicable on CNC milling, turning and drilling applications.Typical applications include rough milling when the material and workpiece surface hardnessvary, die and mold manufacturing, blade manufacturing anCnc, dnc & adaptive control — Presentation Transcript 1. CNC, DNC &Adaptive Control Arvind Deshpande 2. Problems with Conventional NC1. Partprogramming mistakes2. Nonoptimal speeds and feeds3. Punched tape4. Tape reader5. Controller6. Management information4/10/2012 Arvind Deshpande(VJTI) 2 3. Conventional hard- wired NC controller Computer Numerical Control unit NC system that utilizes stored programs in replaced by computer. a dedicated computer to perform some or Soft-wired all NC functions Flexibility4/10/2012 Arvind Deshpande(VJTI) 3 4. CNC4/10/2012 Arvind Deshpande(VJTI) 4 5. Functions of CNC1. Machine tool control Hybrid CNC –Hard-wired logic circuits for functions like feed rate generation , circular interpolation etc. in addition to computer Mass production of circuits and less expensive computer Straight CNC – Computer to perform all NC functions4/10/2012 Arvind Deshpande(VJTI) 5 6. Hybrid CNC4/10/2012 Arvind Deshpande(VJTI) 6 7. Straight CNC4/10/2012 Arvind Deshpande(VJTI) 7
8. Functions of CNC2. In-process compensation – Dynamic correction of machine toolmotion for changes or errors that occur during processing Adjustment of errors sensedby in-process inspection probes and gauges Recomputation of axis positions when aninspection probe is used to locate a datum reference on the work part Offsetadjustments for tool radius and length Adaptive control adjustments to sped and feedComputation of predicted tool life and selection of alternate tooling whenindicated.4/10/2012 Arvind Deshpande(VJTI) 89. Functions of CNC3. Improved programming and operating features Use of tape andtape reader only once On-line editing of part programs at the machine Special cannedcycles. Graphic display of tool path to verify the tape Various types of interpolation:circular, parabolic, cubic Support of various units. Conversion from one unit to another unit. Use of specially written subroutines or macros Manual data input (MDI) Severalpart programs in bulk can be stored.4/10/2012 Arvind Deshpande(VJTI) 910. Functions of CNC4. Diagnostics – Equipped with diagnostic capability to assist inmaintaining and repairing the system Identification of reason for downtime Indicationof imminent failure of certain component Redundancy of components4/10/2012 ArvindDeshpande(VJTI) 1011. Direct Numerical Control A manufacturing system in which no. of machines arecontrolled by a computer through direct connection and in real time.4/10/2012 ArvindDeshpande(VJTI) 1112. DNC with satellite computer4/10/2012 Arvind Deshpande(VJTI) 1213. DNC – Drip Feeding very large NC program Very complex part shapes NCcontroller memory may not handle HUGE part program computer feeds few blocks ofNC program to controller When almost all blocks executed, controller requests moreblocks4/10/2012 Arvind Deshpande(VJTI) 1314. Behind the Tape Reader (BTR) Computer is linked directly to regular NC controllerunit The connection is made behind the tape reader Two temporary storage buffersLess cost4/10/2012 Arvind Deshpande(VJTI) 1415. Special Machine Control Unit Regular NC controller is replaced by special MCUMore accuracy in circular interpolation and fast material removal rates than BTR systems Most CNC machines are sold with computer4/10/2012 Arvind Deshpande(VJTI) 1516. NC, CNC and DNC4/10/2012 Arvind Deshpande(VJTI) 1617. Functions of DNC1. NC without punched tape2. NC part program storage Programsmust be made available for downloading to CNC machine tools Part program can beuploaded after editing from CNC machine Entry of new programs. Editing of programs ,deletion of programs Tool management Tool offsets can be downloaded in to MCU Postprocessor Data processing and management functions Primary storage andsecondary storage Syntax checking and graphic proving of programs on CNC computerCNC can be operated directly from DNC computer Flexibility in shop floor scheduling Part program preparation Machinability database for calculating speed/feed4/10/2012Arvind Deshpande(VJTI) 1718. Functions of DNC3. Data collection, Processing and reporting Monitor production in the factory Data processing and report generation by DNC computer Getting thedata about health of the machine in the form of sensor signals or diagnostic messageswhich can be used for preventive/predictive maintenance Metrological data in the form
of dimensional acceptance4. Communications Central computer and machine toolsCentral computer and NC part programmer terminals Central computer and bulkmemory, which stores the NC programs CAD system Shop floor control system Corporate data processing Remote maintenance diagnostics system4/10/2012 ArvindDeshpande(VJTI) 18 19. Justification of DNC Interconnected CNC machines are large in Very largeprogram number size. Can not be accommodated in the part program Large memory ofMCU variety of part programs and small Frequent changes in batch sizes programdesigns4/10/2012 Arvind Deshpande(VJTI) 1920. Advantages of DNC1. Elimination of punched tape and tape reader2. Greatercomputational capability and flexibility3. Convenient storage of NC part programs incomputer files4. Programs stored as CLFILE5. Reporting of shop performance6.Establishes the framework for evolution of future computer automated factory (CIM)7. 2-5 % increase in operational efficiency of CNC machine tools. Cost of DNC installationcan be recovered quickly.4/10/2012 Arvind Deshpande(VJTI) 2021. Combined CNC/DNC systems Development of hierarchical computer systems in manufacturing Flexibility Ability to gradually build the system More versatile andeconomic approach Distributed Numerical System Part program downloaded onlyonce Redundancy Improved communication between central computer and shopfloor4/10/2012 Arvind Deshpande(VJTI) 2122. Adaptive Control A control system that measures certain output process variableslike spindle deflection, force, torgue, cutting temperature, vibration amplitude, horsepower and uses them to control speed or feed NC reduces non productive time in amachining o peration AC determines proper speeds and feeds during machining as afunction of variation in work piece hardness, width or depth of cut, air gaps in part geometry etc. Increased metal removal rate and reduced cost per volume of metalremoved4/10/2012 Arvind Deshpande(VJTI) 2223. Where to use adaptive control?1. In-process time consumes significant portion of themachining cycle time. (>40%)2. Significant sources of variability in the job3. Higher costof operation of machine tool4. Work material – steel, titanium, high strenghalloys4/10/2012 Arvind Deshpande(VJTI) 2324. Sources of variability in machining1. Variable depth/width of cut2. Variableworkpiece hardness and variable machinability3. Variable workpiece rigidity4.Toolwear5. Air gaps during cutting4/10/2012 Arvind Deshpande(VJTI) 2425. Adaptive Control Optimization(ACO) Index of performance is a measure of overallprocess performance such as production rate or cost per volume of metal removed.Objective is to optimize the index of performance by manipulating speed or feed in theoperation IP = MRR/TWR MRR – Material removal rate TWR – Tool wear rateSensors for measuring IP not available4/10/2012 Arvind Deshpande(VJTI) 25 26. Adaptive control Constraint (ACC) Less sophisticated and less Nearly all ACsystems is of this type expensive Objective is to manipulate speed than research ACOsystems or feed so that measured process variables are maintained at or below theirconstraint limit values.4/10/2012 Arvind Deshpande(VJTI) 26 27. Operation of ACC system Profile or contour milling on NC machine tool Feed iscontrolled variable Cutter force and horsepower are used as measured variables
Hardware components1. Sensors mounted on the spindle to measure cutter force2.Sensors to measure spindle motor current3. Control unit and display panel to operate thesystem4. Interface hardware to connect the AC system to existing NC/CNCsystem4/10/2012 Arvind Deshpande(VJTI) 2728. Relationship of AC software to APTprogram4/10/2012 Arvind Deshpande(VJTI) 2829. Operation of ACC system duringmachining process4/10/2012 ArvindDeshpande(VJTI) 2930. Benefits of AC1. Increased production rate2. Increased tool life3. Greater partprotection4. Increases machine life5. Less operator intervention6. Easier partprogramming4/10/2012 Arvind Deshpande(VJTI) 30