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Lin Xueping | digital twins: the rise of the fourth quadrant (10000 words)

发布时间:2021-12-31作者来源:金航标浏览:2425


Explain the back of Physics
 
 

Information, models, software, have been trying to explain their physical back.


The world is ternary, composed of matter, information and energy. Information is often the value-added part of physical resources, which releases interpretable meanings. A physical entity that does not carry any information is unimaginable. People usually pay more attention to the value of physical entities, while information is often ignored. However, in the manufacturing of key equipment, the mastery of information is far better than the possession of physical products.


In 1980, China first introduced 300000 and 600000 kW power plant equipment. After three years of negotiation, two of the five were selected. The most difficult negotiation is the price. For example, ge of the United States, which is generally favored, can only give up because its quotation is twice as high as that of Westinghouse; The second difficulty is the transfer of technical drawings. At that time, the Swiss BBC (later merged into ABB) left the negotiating table. Westinghouse and another company, which were finally selected, made huge concessions. The generator set information they finally provided was up to 35 tons. (compared with a 600000 kW power plant boiler weighing up to 15000 tons, this figure is amazing. Of course, this unit itself is also an irony. Before entering the digital era, the information of a device can only borrow measurement units from physical products). Among these materials, light drawings add up to nearly 100000. This is the value of negotiation, the introduction of technology, and the most important thing is to make a huge space exchange of information. Without clear information, all kinds of manufacturing activities and products are puzzling, and the operation efficiency is extremely inefficient. At present, the storage methods of information have been very different. The ton weight samples and technical data have eliminated the physical carrier, which also makes it more difficult to obtain the value-added information of physical entities. The technical data of Bosch Rexroth's electronic hydraulic pump and valve products, Caterpillar's engineering machinery and new products have all adopted electronic drawings. The era of unauthorized maintenance plants that can be seen everywhere in the past, which can carry out maintenance with one drawing, is coming to an end. Information is invisible again. It will become more and more difficult for pursuers to obtain and identify the intention of the forerunner only by the identification of physical forms.


Information has been interpreting physical entities in various ways, and models are a common example. Model is a high-level expression of information. It presents the characteristics of high organization, and generally has modularity, which can be easily reused. Reusability is the greatest virtue of the model, which meets the needs of human classification memory. With the help of these models, design and R & D engineers quickly combine various ideas in their minds to form manufacturable products.


In addition to models, software is also a high-level form of information organization. It extracts the knowledge from the information and becomes an executable information combination package. Compared with loose information, its combat effectiveness advantage is like that of a fully armed soldier to an unarmed civilian. Unfortunately, this metaphor can not stand scrutiny in China. Because the valuation of a device is almost different from that of a set of software. Without the support of equipment, software is often regarded as priceless because it is invisible. It is often bundled in machines and sold together. It looks like a "free gift". The great value of software can only be expressed in the premium of equipment. This is a selective cognition, which reflects that people are still full of ignorance about the value of information.


Shuttle between the first and second quadrants


In the process of digital design, a product can be decomposed into digital models of various particle sizes. These models exist in one world, while physical products and manufacturing processes exist in another world. This is the difference between digital space and physical space, which can be regarded as the difference between the first quadrant and the second quadrant on the mathematical coordinate axis. There is a boundary between reality and reality.

 
  Figure 1 from digital space to physical space  


After the design is completed, a definite digital model package (such as EBOM) will eventually cross this hidden line and enter the manufacturing process. But in fact, when the designer's detailed design is frozen, the machine will not be started in the workshop for large-scale production immediately. There is another link in the middle, that is, the physical prototype. It will be made to check and verify whether the models in digital space match accurately, including ergonomics, dynamic characteristics, etc. This is the last line of defense for the model to move towards the product. The physical prototype must be able to prove that it carries the correct information. Obviously, the physical prototype will move forward the predictability of production, although both are in the same physical space and in the second quadrant.


Obviously, without the model of physical prototype, direct production will be an impulsive and dangerous journey. In practice, the physical prototype is still expensive, especially when it cannot prove that the information of a prototype appropriately expresses the demands of the model, so it is inevitable to rework. The construction period and cost will rise sharply, which is the reason for many product development failures or delays. It is often said that design determines 70% of the cost, because design not only needs to complete the functional expression of physical products, but also needs to design good logic at the beginning to keep the information consistent in the whole process and throughout the product life cycle. A large number of failed physical prototypes prove that the consistency of information is not easy to maintain. Products have to return to the origin, and a large number of resources have been consumed, a factory will show a lack of competitiveness.


In order to avoid unnecessary risks for the physical prototype, the predictability of production is moved forward again. It returns to the digital space, and the digital prototype appears in the first quadrant. It gives more simulation and simulation to the performance and manufacturability of a model. In 1989, MDI, a simulation company at that time (later acquired by MSC), first put forward the concept of "virtual prototype", while other CAD manufacturers such as Autodesk, UG and Dassault system put forward the concepts of digital prototype, active prototype and digital prototype from their respective perspectives, including digital mock up (DMU) Is widely used. It pours more relations and contextual meanings between three-dimensional models, and carries out complex simulation. The existence of digital prototype greatly reduces the failure of physical prototype (sometimes it simply replaces the real prototype). Due to the consistency of information transmission, the difficulty of manufacturing is greatly reduced. Digital prototype is not only a rehearsal in which information replaces physics, but also a great victory of industrial software. It has greatly promoted the popularization of user end. From this point of view, physical prototype is an expensive transition product formed by the blockage of information resources. Before a car really moves towards large-scale manufacturing, it needs to spend a huge cost to do blowing experiments. The car will be placed in a huge wind tunnel to simulate the resistance distribution of windshield and body shape through strong airflow. Wind tunnel experiments on aircraft and spacecraft are even more expensive. The wind tunnel with huge cost can be said to be a pure gold test bench prepared for physical entities. When the wind tunnel rings, there will be ten thousand taels of gold. This is the high cost of information congestion. Later, when people began to use digital prototype for blowing experiment, the cost began to be greatly reduced. The most famous wind tunnel laboratory in the United States, Langley laboratory, has fewer and fewer wind tunnel startup times.


From this point of view, design is the most expensive manufacturing. Unfortunately, this link is often erased by the cover of selective cognition. People only believe in high-speed rotating machines in the workshop and AGV cars running around. Only these busy are considered to be expensive costs, so they are paid special attention. Design is often subordinate to manufacturing process. Information has been thrown aside.


Professor Mr. grieves of the University of Michigan once mentioned in his book "virtual perfection model: driving innovation and Lean products": "information is a substitute for wasted physical resources". If we take a step forward, we will find that the cost waste in many factories actually starts with the neglect of information. When a machine begins to "get sick", there will always be precursory signals. However, this signal is either too weak or directly omitted, which will eventually lead to low OEE efficiency of plant equipment. In this sense, if we want to really pay attention to the improvement of machine efficiency and the rationality of material consumption, it is far from enough to only use high-grade machines or automated storage systems. How to transfer and identify the information between these machines and parts is the key to improve efficiency.


When this information transmission is blocked, the waste of physical resources will inevitably accelerate. Why did Toyota's lean model become a blockbuster and a model for all factory managers after it was sorted and disclosed by American scholars? That's because there is still a lot of careless waste in almost all factories that seem to be well organized and managed. These wastes exist in the form of machine downtime, repeated processing, raw material stacking, quality deterioration, delayed delivery and so on. Toyota's lean model finds the key invisible information flow behind it. Items are no longer easily moved (for example, the zero inventory model advocated by timely production is to block unnecessary object movement), because physical movement has a huge cost. The cheap flow of information needs to run first. The correct time, the correct station and the correct material are realized because the information flow is one step ahead.


This is a busy scene on one side of the factory, while on the other side of the factory is the world of users.


Product orphans in the third quadrant


A product has actually come a long way before it finally comes into the hands of users. It originated from a designer's neuronal impulse, which is an idea. The designer captures this neuron impulse and converts it into a size constrained model through design software. This model, after determining the future performance through virtual digital prototype DMU and various analog simulations, enters the physical prototype stage and moves towards the manufacturing of physical products. This is a process from digital space to physical space. The product enters the physical space of the second quadrant from the digital space of the first quadrant.



Figure 2. Three quadrants of traditionally manufactured products


After the product is manufactured, it will be delivered to users. The product leaves the second quadrant and enters the user space of the third quadrant, which is the normal destination of a product and the place where it realizes its value. Only when purchased and used can a product be recognized as a commodity. The biggest value of the third quadrant is to establish the ultimate meaning of the product.


However, most products will lose contact with manufacturers after entering the third quadrant. This phenomenon can be called "product orphan". It is produced by the manufacturer in the second quadrant, but after it leaves the factory and enters the third quadrant, it is basically irrelevant to the manufacturer - only when the fault requires warranty, the two will rebuild the unpleasant connection. The most important reason for the loss of product contact is that the flow of information in the whole process of product design and manufacturing has basically stopped. It may remain in the hands of manufacturers and users do not know; Or the information about product operation is left at the user's end. Careless users may not pay attention to it, and the manufacturer can't understand it.


Product orphans are essentially formed by the rupture of information flow. This kind of fracture takes the connection between the user and the manufacturer as the decomposition line. The moment the payment is completed, the connection strength between the two immediately drops sharply. Considering that there are many distributors, agents and installation teams between manufacturers and users, the information is completely broken, scattered and stored in institutions at different levels.


Design, manufacturing and users are things that happen in the three quadrants of I, II and III. Design and manufacture, on the other side of the user; The physical world of manufacturing and users is on the other side of the design model. The crossing between quadrants is not perfect for information. Some useful information will be lost and some irrelevant information will increase. All these increase the difficulty of backtracking. But the important thing is that the movement of physical entities is expensive, while the movement of information flow is extremely cheap and can be reused. Therefore, it is always a cheap way to let information flow replace physical movement.


This basic product flow path and the information flow behind it have dominated the model of commodity society for thousands of years. The extensive use of design tools and software for more than half a century has made the flow of information more and more transparent. The waste of physical resources caused by poor information flow has also become amazing, and the value of information has begun to attract people's attention.


The rise of digital twins


This understanding is slowly being strengthened. With the concept of information, model, software and digital prototype as the groundwork, a concept that is easier to understand and closer to the people began to appear.


The concept of digital twins is closely related to Professor grieves mentioned earlier. Not surprisingly, the professor is a participant in digital manufacturing for more than 40 years and knows PLM (full life cycle management) software like the back of his hand. Obviously, the proposal of this concept is closely related to the whole product life cycle, product model and digital manufacturing. Digital twin is regarded as "rebuilding the digital information of physical system into an independent body". The "roadmap of analog simulation technology" released by NASA in 2010 should clearly put forward the concept of digital twins in the literature at the earliest.


If you think this is a star's action doubles, considering that this doubles has always been an undisclosed existence, and the physical existence is almost zero, then this understanding is not impossible. In contrast, Gartner defines it as "a digital representation of a real-world entity or system", which is much broader and more general. It even puts forward the digital twin organization dto, which is more difficult to understand.


NASA has carried out extraordinary practice on the rocket platform. A rocket and its corresponding digital twin give people intuitive imagination, and really form engineering value. However, the digital twin at that time was still an expensive luxury, or a superior model. It can only work in very limited situations. Later, Ge aviation's engine further invited the digital twin to the temple to form a commercial application. In the GE90 engine, there are only 14 physical sensors, but it constructs a digital twin model. Through a large number of virtual sensors and various timing data, a huge data flow is formed and analyzed. The remote maintenance of the engine has become more controllable, which is a huge and successful business model. Go with the trend, and then later, GE's concept of industrial Internet became famous, which was natural.


Then why is it that today, this concept is beginning to become hot. The biggest driver behind this undoubtedly belongs to the Internet of things. All things are interconnected, and this ambition also includes the shadow of all things. The popularity of cheap sensors and the deep coverage of digital technology make connections almost everywhere. This also makes digital twins, completely get rid of an academic concept and become a key role in the center of the stage.


When did the digital twin "life" begin to activate? The glory of this moment of birth does not belong to its manufacturer. It does not start from the design software CAD or PDM. No matter how much "dowry" (model, database, algorithm, etc.) designers and manufacturers give it, its life starts from the moment it is delivered to users. This is a model that opens the window to the most meaningful moment of light. Before that, all actions are just debugging and just a preparation for life. If we say that the twins accompanying new products can be called original digital twins, we can also directly build a "circulation digital twin" around the operating existing equipment, which will point to a more clear goal.


Digital twin is like a Wikipedia web page. From the blank at the beginning, to the first article, to more articles, these web pages will become thicker and thicker, and the connection between them will become more and more complex. They record the growth of digital twins, and behind this is an attempt to record the real state of physical products at any time. Think about a simple scenario. If you look through the flow of wechat payment, the track formed by these numbers actually records your credit performance in a form of digital twins.


From here, we will find that the biggest difference between digital twin and traditional models and software is that it is a self growing dynamic model. If we can quickly browse the whole life span of a digital twin (this may be a few minutes or decades), we may see the traces of its evolution. Just like the history of human evolution: an ape stood up, had a fire in his hand, learned to tame wheat and sheep, became the king of all things at the top of the food chain, and entered the city from the edge of the field. Similarly, digital twins, with the energy to accumulate records and simulate optimization, began to learn to grow. Herali, the author of a brief history of mankind, mentioned that the cognitive revolution (the earliest origin stage of Homo sapiens) was the driving force that separated history from biology. Before that, all human behaviors were actually biological categories. Digital twins certainly do not have the characteristics of organisms, but if viewed in this metaphorical way, they can be recorded and simulated, which also makes digital twins further separated from the model category. The two intersect, but also play a greater role.


The new master of the fourth quadrant


The whole life cycle of products (including use after delivery, operation and maintenance until scrapping) has always been of great interest to product manufacturers. However, such costs and costs are often very high, and only a few high-value products have the necessity of such development. For institutions such as NASA, each launched aircraft is extremely expensive, and full life cycle tracking is a matter of life and death. Therefore, these practices can only be used in large-scale engineering background, and can not make digital twins widely used in business.


However, the popularity of the Internet of things has changed this layout. After a product is delivered to users, due to the nowhere of the network, the convenience of data transmission, tracking an entity and simulating according to its model become accessible. A new territory of digital space has emerged on the user side. The originally empty fourth quadrant has a new master. Digital twin not only echoes the existence of physical products, but also is closely related to the use of users. The quiet fourth quadrant became lively due to the emergence of digital twins.



Figure 3 , new owners in the fourth quadrant


Before there was no digital twin, there were two information flow channels in the three quadrants. There was a two-way channel between design and manufacturing, which was the interaction between information space and physical space. It may or may not belong to an institution. Generally speaking, there is a single channel between manufacturing and users. After the information of product manufacturing is transmitted to users, the channel is closed. The product is in an "orphan" unconnected state. Of course, there are exceptions. For example, remote maintenance is a two-way information exchange between manufacturing and users. Even without the concept of digital twin, Luoluo engine successfully supervised its flying engine in the sky in 1998 and successfully locked it into a business model. This surprise attack once led to the loss of loyal customers such as All Nippon Airways. Later, this business model has become the standard configuration of the aeroengine industry and the most classic foundation case in the field of industrial Internet.



Figure 4 # three new information channels


Because digital twins have a firm foothold in the fourth quadrant, it adds three data channels. One is the interaction between digital twins and physical products: This is the fulcrum definition of digital twins. Without this, digital twin is no different from its predecessor, various models. The reason why digital twin stands out from the model stack is that it has the interaction and similarity with physical entities, and it also has real-time in many occasions. In the always silent data warehouse, there was a regular heartbeat for the first time. This is the fourth quadrant. As a new territory, it declares a brotherly existence to the third quadrant.


If the product orphan is a silent physical entity, then the digital twin is an enthusiastic rapper. If it is not limited, it is "talking" all the time. Massive data is its best output. These massive data are the description, diagnosis, early warning and even prediction of the physical world. In special cases, these data will also trigger the actual operation to control the physical product. Of course, this is often regarded as a dangerous action in the industrial field.


The second information channel is that it returns its own clues to the hands of the manufacturer. There are still many restrictions and discussions on the legitimacy of this channel. But the manufacturer can finally have enough signals to listen to the echo of the product. This is a milestone handshake, which is of great significance for manufacturers to improve product performance.


One of the pain of the defects of China's industrial civilization is that there is no friendly and continuous interaction between manufacturers and users. Once the product is delivered, the operation data will be cut off, and the road of continuous design verification will become a dead end. This was originally the best opportunity to improve product feedback. A boiler plant and a steam turbine plant basically go their separate ways after hundreds of millions of yuan of equipment is delivered to the power plant. If the power plant comes back to the main engine plant one day in the future, it is generally not something else, but "fault finding" and requires repair for various faults.


The third information channel is a digital twin, pointing to the design department. Generally speaking, in the manufacturing process, the digital twin feedback information will be provided to the design department. However, the more direct method is that the design department can directly obtain the dynamic information of physical products. PTC once showed a heartwarming scene, that is, the torque, tire pressure and other information transmitted to the design department when a bicycle crosses the street and streams. A designer can finally directly see how his ideas work in the physical world. It should be a moment of great pride.


Digital twinning has changed people's expectation of a product working condition. A car, a machine, no matter how customized, will present an average characteristic when it leaves the factory. Your machine may be the only one in the world in terms of shape and size, but its average energy consumption and conventional application scenarios are locked in a range. The design parameters of the machine will be set as the average working condition in advance. The reason is very simple. The information flow is cut off at the moment of product delivery. The manufacturer cannot know the real-time operation of the machine. The digital twin makes personalized customization and further moves towards the customization of applications. In fact, personalized customization can better reflect the realization of users' exclusive value than personalized customization.


The digital twins of five aircraft of the same batch and model customized by an airline are different.Airbus A321 with tail number N123, once put into operation, has its unique digital twin N123, even if they carry exactly the same information when they leave the factory.It makes the operation and maintenance of an aircraft begin to move towards different scenarios.In other words, due to the digital twin, the working condition of the machine is recorded in real time, and the compressed average working condition begins to recover into an instantaneous parameter.Only at this stage can real personalized meaning be produced.This returns to the value of digital twins:It was born to optimize the performance of physical products in real time.



Figure 5 , from personalized customization to personalized customization


If we can get through the whole data flow, a continuous data flow will be formed from the first quadrant to the fourth quadrant. The data flow across the four quadrants is the surging power driving product design. The rise of digital twins in the fourth quadrant makes the whole data flow form a complete closed loop in the whole life cycle for the first time. This framework of information interaction and communication is particularly important to ensure the accuracy and fidelity of information transmission.


After all, it's just a model


Digital twin is a model describing the world, or an advanced model. Because it contains data, analysis, professional knowledge and software capabilities, and has various interfaces and applications. But because of its simulation ability, it has more pertinence and initiative than the model. At this point, it is similar to software.


This means that digital twinning is not the whole response of the real world. It is always just a local imitation of the physical world, a follow-up model and a defective shadow. Its only effort is to move closer to reality and infinity. This means that the high fidelity of a digital twin is a key proposition. Although the independent body wants to be as close to the real body as possible, it is an impossible mission. A dazzling array of digital twins, like the dazzling apples in the apple orchard, have experienced the harvest season, large and small. But after taking it off, it is different in size and luster, and it should be divided into many levels. Good apples can sell at a good price, while unsightly apples can't even enter the trading market. Digital twins can also be divided into good and bad grades. Healthy digital twins will have better fidelity; A bad digital twin will deviate far from its physical entity. It is entirely possible to give people false information, which is the dangerous digital twin. It can be said that in the world of digital twins, if we count them one by one, they must be full of sick men everywhere - they can't fulfill people's overly enthusiastic expectations for digital twins.


The factors that determine the health of digital twins depend on how digital twins are constructed. Unfortunately, digital twins are now used by various industries. There is no standard for digital twins, and each company has its own definition.


In short, the current overly enthusiastic description makes people worship it, relax their vigilance and ignore the truth: the digital twin does not completely reconstruct the whole of physical products. On the contrary, in most cases, it is a highly condensed simplified version of a large number of physical entities. A machine with thousands of parts will be cut into different granularity by different users. Perhaps only a few parts will enter the digital twin world. Digital twin is an incomplete existence by nature.


Of course, it came warmly.


There are tools under the system


How did the healthy digital twin come into being? Expertise is of course the key. It is also essential to understand its system and tools.


Especially for the construction of digital twins of complex products, we need to deeply understand the surrounding environment of digital twins. Its emergence represents a new connection of space-time view, from the past, the present to the future, from physical space to digital space. Behind this is a huge relationship system, and the method to solve this complex relationship requires a set of system engineering methodology and a complete description of system requirements.


In fact, NASA's digital twin in 2010 has a serious and grand engineering background. First, NASA plans to fully use digital twins in the Venus lander program, which is part of NASA's ambitious space exploration program. More importantly, digital twins appear in a complete set of technical architecture of system engineering, including computing, modeling, simulation and information processing. Digital twin is the digital heart after the four diamond layers are woven. It can be said that digital twin is an intersection of model-based systems engineering (mbse) and the Internet of things (IOT) era. If we peel off these surrounding conditional elements and regard mbse as nothing, the digital twin will inevitably not be vulgarized and carried out alone, becoming an interesting and fun interface game. The single digital twin is weak. It is only visually superficial and meets the mind of pursuing a gorgeous surface. It is no different from buying a coin and returning a pearl. This is a selective shortsightedness of the industry. If we further enlarge the digital twin into a vigorous demonstration project, it will become a tragedy.



Figure 6. NASA system breakdown structure


To build a digital twin, the underlying tools are essential, and industrial software is the most obvious. If we can understand that digital twins originated from PLM thinking and extension, we can understand why traditional PLM Software manufacturers (including CAD and CAE software) are so enthusiastic about digital twins. If the original weapon is polished, you can show your skills. With the tools that traditional engineers have been using, combined with the current popular technologies such as microservices and containers, digital twins can also be built with the help of the industrial Internet platform. Ge builds a digital twin for its GE90 engine, which takes 25 weeks. With the help of industrial Internet platform, this time is expected to be reduced to 6 weeks. After construction, the digital twin can be embedded into the industrial app in the form of various functional modules, and the information and results pushed by it can also be seen through the browser.


Building digital twins is like building a palace. The roof is the architecture of system engineering, and the foundation is all kinds of software. The builder loads various industry knowledge into it. When the digital twin is praised, we need to deeply understand that system engineering is the foundation of leading the structure, and industrial software is an indispensable tool.


Notes: beware of concept storm


The physical entity represented by digital twin in the fourth quadrant, whether it is an offshore wind turbine, a magnificent building, a city with prosperous population, or even a supply chain, the situation has not changed much. A few and local physical features have reconstructed a refreshing new world, which can be retracted, replayed and reconstructed. It is closer to the ambition of "everything is under control".


The rise of digital twins from the fourth quadrant means that the focus of manufacturers has shifted from "product economy" to "experience economy". A user's experience is a difficult thing to quantify. However, through digital twinning, many abstract parameters are faithfully recorded by real behavior. Experience economy is no longer an art of understanding, but a scientific law that can be captured. This makes the manufacturer's profit point and has a new blue ocean voyage. Digital twin has realized "personalized customization", which also gives full play to the internal attribute of "personalized customization", which is the ultimate goal of experience economy. Large scale fixed use to realize thousands of people, thousands of planes and thousands of machines.


It can be said that digital twin has become a new distribution center of data. This is the real meaning of the rise of the fourth quadrant. It turns a three quadrant world into a perfectly symmetrical four quadrant world. The data flow of the whole life cycle of the product can finally form a valuable closed loop. The integration of manufacturing and service has become more logical.


However, digital twin is only a model that can be simulated after all, a model that complements the industrial Internet. It itself does not automatically release value, let alone be regarded as an independent productive force. Raising the value of digital twins alone is of little significance. The biggest inspiration it brings is to use more information flow and data analysis to build a narrative way of "behavior exposing the truth". In the United States, Japan and Germany, digital twin is just an ordinary academic concept, which is calmly cited by the engineering community without any magical spark. This is more an evolution of the way of thinking. Instead of being obsessed with the magic of digital twins (actually not), it's better to take the opportunity to vigorously edify and promote the landing of system engineering thinking, otherwise digital twins has really become the best advertising language for promoting tool software.

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