[Turn] The Hydraulic Gap between China and Foreign Countries: An Interview with Zhang Haiping

Can you tell us something about your work experience in Germany?

1988 received his doctorate from Shanghai jiaotong university, and was the first doctoral student majoring in fluid transmission and control in China at that time. From August 1988 to March 1990, he worked as a postdoctoral fellow in the Institute of Hydraulic and Pneumatic Engineering of Aachen University of Technology, Germany, and studied under Professor W.Backé. I belong to a generation delayed by special times. I spent ten years on a farm in the suburbs of Shanghai, and started my professional study very late. Although I later became a hydraulic teacher, I didn't know much about hydraulic technology except simulation because the subjects of master's degree and doctor's degree were simulation. After arriving at the Hydraulic and Pneumatic Institute of Aachen University of Technology, I tried to improve their existing digital simulation software package DSH.

Professor Barker asked me to do it myself at first, but it was some time before he pointed out to me that I also wanted to study some practical problems. At the end of my postdoctoral period, Professor Barker asked me, what will happen after the end? I told him that he would definitely teach at the university when he came back. He told me that in Aachen University of Technology, engineering graduates, whether masters, doctors or postdocs, can't stay in school directly after the end. They must work in this industry for at least five years before they can apply for the position of university professor. He said that he had been to China several times, and although he didn't know Chinese, he could understand a thing or two about the university hydraulic textbook in China. He said that there are many theories, but they are far from reality, and the hydraulic teaching in China University is also far from the industry. So he suggested that I take this opportunity to practice in a German factory after my postdoctoral work. At that time, Le Cai Company came to Aachen to find a major in hydraulics, so it suggested me to go there, saying that a medium-sized factory is better and can get in touch with all aspects of the enterprise. If you go to a big company with thousands of engineers, you can only get access to a small part of the business. In this way, I went to the R&D department of Le Cai Company for an internship. Although the sparrow of Zoeller-Kipper is small and complete, it has branches and subsidiaries in France, Britain, Austria, Czech Republic, Poland and other European countries, and has been building factories for more than 50 years, specializing in manufacturing gyro-compressors and hoists for waste container trucks. After I went, I participated in the improvement and research and development of its hydraulic system. Since then, I have devoted myself to the actual hydraulic engineering, paying attention to the technical problems that I thought I was incompetent and indifferent when I was a teacher in the university, but I can't ignore the performance and reliability of the actual hydraulic system.

After the internship, I stayed in the R&D department of Le Cai Company, responsible for the research and development of hydraulic and electronic control systems. At the same time, as the head of the hydraulic system of the whole company group, I provided consultation and training for various departments and subsidiaries, and was responsible for solving the hydraulic problems that they could not solve themselves until I retired. Now I often go back and forth between China and German.

I remember Professor Barker's teaching me: "Pay attention to reality and go into practice", which changed the track of my professional study and benefited me for life, and I have always been deeply grateful for it.

What are the steps to develop a new product abroad?

Two points need to be emphasized in advance.

First, this problem is too big. I only know a few German companies.

I have also participated in some products that are completely divorced from the existing solutions and developed from scratch to find new principles and new structures. The basic steps are roughly as follows. In fact, China also knows:

1, widely collect market information and customer needs;

2. Try to understand the level and characteristics of competitors' products;

3. Analyze the problems of existing products in detail;

4. Determine the performance level and cost ceiling that the new product should reach-better performance and lower price than competitors;

5. Carefully analyze and organize and imagine all possible solutions; At this time, almost only at this time can the ability of invention and innovation be fully exerted. At this time, it is also a time to test the tolerance of "whimsy" and "heresy". At this time, only ideas are allowed, and you can be unconstrained, and you are not allowed to say "no".

6. Then compare the feasibility, advantages and disadvantages of each scheme in detail, from the technical and economic point of view;

7. Determine the scheme and start the design. At this time, some modern means are also adopted, such as finite element strength analysis, flow field analysis (CFD), and digital simulation of dynamic characteristics. , but only a few are based on a large number of tests, focusing on practical goals rather than publishing papers.

8, making a prototype;

9. Conduct safety assessment;

10, under laboratory conditions: no load, full load and overload;

1 1, improved;

12, field test, test under various climatic conditions;

13, and then improve;

14, small batch trial production;

15, sent to customers in various regions and countries for trial use, and started high-frequency and high-strength life test at home;

16, and then improve;

17, mass production, put on the market;

18, and make a comprehensive improvement after one or two years according to the actual application. Time is long, investment is large, and risks are considerable. I have participated in two such R&D projects from scratch: one, after two years of R&D trial production and two or three years of improvement, the complaint rate of repair rate has been reduced to almost zero, which is very popular with customers, bringing considerable profits to the company and becoming the golden hair of the company; On the other hand, although after several years of improvement, the performance has reached the requirements of the market, but the manufacturing cost has exceeded the plan, which is basically a failure, and alternative products have been developed.

I have heard the report of Mr. G.Dueck, a German professor of mathematics and a senior manager of IBM. He mentioned that according to statistics, only one out of every 10 correct ideas (patents) can become a successful product. Therefore, to develop new products, we must first consider the possible risks.

Your experience determines that you have a broad vision, so what do you think is the main difference between China's hydraulic industry and German?

I did live and work in Germany for more than 20 years, but that's all. I don't think my vision is broad.

The hydraulic industry needs the support of other industrial sectors. Personally, I feel that we have a great gap in materials, casting process, forging process, heat treatment, precision machining, measuring instruments, seals, working media, electronic components, servo amplifiers and electronic controllers, valve electromagnets, supporting hydraulic parts and so on. But these can be gradually localized, and some materials or components are imported from abroad and then digested and absorbed before innovation.

For the backwardness of the hydraulic industry in China, Mr. Wang Changjiang, the special consultant of the Liquid-tight Association, once brilliantly summed it up as follows

In the 1980s, the products were backward and the means of production were backward.

In the 1990s, the system was backward and the management was backward.

265438+In the 2000s, the concept was backward and the market ability was backward.

This can be summed up by experienced and broad-minded people, but I can't. I fully accept his point of view.

From my own very limited experience, I can only add two points.

First, employees' serious attitude towards their work. In the German enterprises I know, leaders pay more attention to the voluntary or forced working conditions and welfare of employees, and employees are proud of making good products and don't muddle along. When they work, most of them are not nervous, but serious and responsible. Meticulous, almost to the point of rigidity. For example, the incoming inspector of our company must measure the length of the connecting wire of the purchased solenoid valve. Even if it is a few millimeters longer than the drawing size, it is not easy to release. I have to sign a special approval. Mechanical manufacturing is different from artistic creation, and perfect quality requires this almost rigid attitude.

They are not superstitious about theory and want to test everything for themselves. For example, cavitation is common in hydraulic components. It's been many years, and it's enough to tell some truth and write some formulas. But in the laboratory of Sun Dede's subsidiary, I witnessed the cavitation phenomenon for the first time-a blue flame the size of a grain of rice was ejected from the outlet of the overflow valve.

Secondly, unfortunately, the hydraulic teaching materials and experimental equipment in some universities in China are also quite backward (see my humble opinion published in the sixth issue of your magazine in 2009), which is also a big gap between China's hydraulic industry and Germany. Because everything is done by people. If the students trained in our universities are old-fashioned, ignorant of reality and poor in scientific research, who will make good products in our industry?

We are willing to spend billions on importing foreign hydraulic products and hundreds of millions on importing production equipment every year. I don't know, how much money are we willing to spend to improve the professionalism and research literacy of employees? How much effort will you put into writing or translating some hydraulics textbooks that really keep pace with the times?

To put it mildly, what should our enterprises do to narrow these gaps?

In my opinion, if an enterprise only investigates and imitates, instead of testing R&D, it will always fall behind. If we want to narrow the gap, we must be down-to-earth, persevere and constantly improve. This improvement not only includes improving performance, stabilizing quality and prolonging life, but also includes adding variants to adapt to more application fields. Improvement also belongs to R&D, which is an indispensable part of R&D and more important than designing new products.

Take the manual of almost any Rexroth product as an example. Just look at its modification date, replacement date and improvement code, and you will know how they are constantly improving. Good hydraulic products are painstakingly improved!

Take the problems encountered in actual use and the opinions put forward by customers as opportunities for improvement, not fooling. These, as far as I know, are all done seriously by German enterprises. Many domestic entrepreneurs also understand and work hard to do it seriously. It is said that the cleanliness of workshops in existing enterprises in China has reached the level that "steamed bread can be picked up and eaten when it falls to the ground". However, I have also visited the hydraulic assembly workshop of a domestic enterprise: people must pass through the front and rear isolation dressing rooms, wear hats, isolation suits and shoes, but there is a door next to it that is always open. Forklift trucks carrying workpieces roared in and out, and the wheels were covered with debris.

Seriously, this is a virtue. He who fools others finally fools himself.

From your point of view, what advantages do Chinese hydraulic enterprises have? Or what advantages do we need to develop?

Compared with European and American enterprises, I think China's hydraulic enterprises have two advantages.

First, it is still about labor costs. In Europe and America, most of the income of fluid technology enterprises must be used to pay employees' wages and benefits. I know some world-class fluid technology enterprises, although the product price is very high, but there is no profit, of course, do not pay income tax. Their employees not only have good wages and benefits, but also work much shorter hours than in China. On the other hand, it should be noted that the technical quality and work seriousness of its employees are also higher. This is an indispensable factor in determining productivity and product quality. Therefore, I think our enterprises in China should not abuse China's low labor cost for a long time, but also care about the treatment of employees, so that they can share the sweetness of enterprise development and really work with peace of mind. Times are changing, and business leaders in China can no longer expect their current employees to be treated like apprentices. In this regard, a competition has quietly begun. Whoever takes the lead in improving the treatment of employees will win the hearts of employees and retain and obtain experienced and high-quality employees. People-oriented is also the truth. Whoever uses it to fool his employees will eventually be fooled by his employees-when they can't vote with their hands, they will vote with their feet.

Second, regional (geographical) advantages. China has become or will become the world's largest market for hydraulic products. China's hydraulic enterprises are close to the market and users, which is also a big advantage. Make good use of it: run more users, do more field tests, and make timely and serious improvements according to the actual use. Don't underestimate this advantage. Imagine how many obstacles your hydraulic products will encounter in exporting abroad, and you will understand. Although some foreign companies have the first-Mover advantage, their distance from customers in China will also bring problems. A few days ago, I met an employee of a China subsidiary of a world-class company. He lamented that in order to persuade the relevant departments to make some improvements on the products exported to China, I stayed in my parent company for two weeks, so I was tired. When will these changes be realized? I don't know

In the field of hydraulic and pneumatic, do you think there are some new products and applications that have just started abroad? If domestic enterprises intervene now, they can at least stay at the starting line?

There are some such new products, but I'm sorry, my knowledge is limited and I haven't paid special attention to this problem. I think the hydraulic industry is relatively mature compared with electronic information and biotechnology, and new products appear far less frequently. Therefore, today's competition in the hydraulic industry is not a 100-meter race, but a marathon. It doesn't matter if it's early or late. The key is who can make continuous progress and stick to the end. The experience of senior engineer Xu, the leader of CY Pump, was published in the fifth issue of your magazine, 2010-ten years without improvement and twenty years behind-which really hit the nail on the head, the truth!

For example, when my company Le Cai developed the garbage compressor in 1997, because it had no experience, it first learned from other companies and used the hydraulic valves of world-class companies. But I have been thinking about the working principle and performance requirements of the compressor. In 2004, the opportunity finally came. I put forward a new circuit and adopted valves from other companies. After a year of testing and improvement, it began to be used in a series of products in 2005, and the products of that world-class company are no longer used. They sent four sales technicians and department heads to negotiate. The leader of Le Cai Company answered them very briefly: Sorry, you are late. Our new hydraulic system has better performance and cheaper price, so it is impossible to use your products any more. I started at least seven years late, but I finally caught up.

Give another example. Mr. J, a doctor engineer I know, studied the piston pump when he was a doctor at the Institute of Hydraulic and Pneumatic Engineering of Aachen University of Technology. 1992, after receiving his doctorate, he stayed in the institute as chief engineer until 1996, and then worked as chief engineer in Brueninghaus Hydromatik, a pump factory in Ulm Rexroth. When he was a doctor, the institute put forward a patent-setting a medium pressure buffer chamber in the transition zone from the low pressure chamber to the high pressure chamber of the piston pump to improve the performance of the pump. At the party in 2005, he said, now I am happy to report that this idea has finally been applied to a series of products. It took nearly ten years to improve a water pump. Is this a marathon or a 100-meter race?

It takes a lot of investment and risk to engage in new products. Even if the product is technically impeccable, whether it can be converted into a commodity is still a question of market acceptance and acceptable cost. So I think it's better to do the existing products seriously. At present, in the domestic market of hydraulic devices in China, imported parts account for about one third, amounting to tens of billions of yuan (liquid-tight trade association); In the international market, Chinese mainland's fluid technology products only account for 3.2%, and Taiwan Province's is 1.0% (VDMA, Germany, 2007). It will be a great achievement if China enterprises can make their own products well, reduce their import share and increase their export share within a few years. I'm not against new products, but I don't think it's necessary to pursue new products. If the existing products are not good, why can we make new products?

By the way, Mr. J returned to Aachen University of Technology as a professor two years ago. Students under the guidance of such professors will not be divorced from reality and lack research literacy?

Professor Lu Yongxiang once pointed out, "In our discipline, there are a lot of comprehensive, integrated, integrated and innovative applications. According to the needs and demands of the application, it is also an innovation to integrate the existing technology, the most suitable technology and the most suitable technology to form a new technology. " I agree with both hands on this.

Give an example of personal experience.

During 1997, when Lecai Company developed a new generation of garbage bucket elevator, I adopted differential circuit and electro-hydraulic proportional valve, which were properly integrated. There is no obvious change in the driving mechanism and the operating habits, so there is no problem of market acceptance. However, its performance is obviously improved, its efficiency is greatly improved, and it is very popular with users, thus bringing output value of hundreds of millions of yuan to Le Cai company. The principle of differential circuit is so old that every freshman has to learn hydraulics. If you write a paper on it, you will be laughed at. I was embarrassed when the company wanted to apply for a patent for it. But it does meet the needs of the application, and at the same time shortens the working cycle to the limit allowed by the safety standards. In this way, no rival can be faster than it, ensuring the company's lasting leading position in this kind of product market, and no product can replace it so far.

So my experience is that it is not necessary to pursue innovation, but it is important to meet the needs and demands of applications around practical problems.

Many years ago, I participated in a project (as a translator). A large state-owned enterprise wanted to buy a new technology (non-hydraulic) from Germany. On and off, we talked back and forth for several years. The Chinese side proposes that this technology must be the latest in the world, and it must stand the test of practical use for at least ten years. Of course, China's requirements have minimized his own risks, but how is this possible? Unless this decade, the whole world will stop innovative research and development. This state-owned enterprise has thousands of technicians, but it is only prepared to buy ready-made prototypes and complete sets of drawings. But only a few people in Germany dare to take risks and innovate, and this spirit cannot but be admired.

In your opinion, as a technician, how should I improve my technical level quickly?

As far as I am concerned, the practical ability and practical understanding ability of mechanical graduates in domestic universities are generally worse than those in Germany. Therefore, my advice to domestic university graduates who enter the hydraulic industry is,

(1) Go to the workshop more, go to the construction site more, do more tests, pay attention to solving practical problems, and be less self-deceiving.

(2) Learn more, think more, and don't be superstitious. There will be mistakes in international standards (see my essay "Testing is the Soul of Hydraulic Pressure", No.6 of your publication 20 10), not to mention other standards, manuals and teaching materials. Recently, I came across the revised draft of the existing industry standard of a hydraulic valve testing method. There are many mistakes, some of which are copied from the old version 1998. This shows that the reviser is unwilling or unable to spend energy on it and has not carefully revised it. If these mistakes cannot be corrected in the final draft, these fallacies will spread for another five years, to 10 year.

However, we should never throw away some data just because it may be wrong, but should study it critically. Deepen understanding through thinking. Finding possible mistakes is also an improvement.

(3) If possible, take part in short-term study, technical lectures and seminars related to work.

Professor Barker mentioned in his "The Past and Future of Fluid Technology" (edited by You, No.5, 20 10) that the cover plate type two-way cartridge valve significantly reduced the cost of the system in the field of large flow, so can the threaded cartridge valve play a huge role in the field of small flow?

In fact, the threaded cartridge valve not only can, but also has played a huge role in the field of small flow.

(1) Compared with other assembled valves, the cartridge valve can be said to be a valve without jacket, which can not work independently, and can only work when installed in a valve block or manifold block. But because of this, it is especially suitable for wearing a suit with other cartridge valves-manifold blocks, which is particularly compact. By reducing the number of connecting pipes, the pressure loss is reduced, the parts that may leak are reduced, and the working reliability is improved, thus reducing the construction cost and operating cost.

(2) The popularity of 3D design software and CNC machine tools has broken through the bottleneck of integrated block design and manufacturing technology, shortened the delivery time and reduced the cost. The supplier of the integrated block has gone through the whole process of design, manufacture, assembly and debugging of the integrated block since receiving the system circuit diagram, which greatly reduces the design cost of the main engine factory. Therefore, the assembly method of cartridge valve manifold block has become the first choice for hydraulic system designers. The application of tubular valve, plate valve and superposition valve has been greatly rejected, especially tubular valve and superposition valve.

(3) Screw cartridge valves are mostly used in mobile machinery, and the proportion of traveling hydraulic pressure in the whole hydraulic industry is increasing. According to the statistical report in 2009, traveling hydraulic pressure has accounted for two-thirds of the total hydraulic output value in Europe and three-quarters of the world. The application of threaded cartridge valves has also greatly increased.

(4) Eaton Company mentioned in the product sample in 2003 that the growth rate of cartridge valve manifold block business is two to three times that of other hydraulic industries. According to the report of Sun Hydraulics, the global hydraulic valve market is about $3.5 billion, while the threaded cartridge valve and its integrated block have reached $65.438+0.3 billion. It is said that HydraForce Company, which specializes in manufacturing threaded cartridge valves and their manifold blocks in the United States, has increased its output value by 1.5 times in recent five or six years, from 90 million dollars to 240 million dollars.

(5) In recent years, various hydraulic giants have bought screw cartridge valve manufacturers because of the promising development prospects of screw cartridge valves. For example, Bucher Hydraulic Group acquired the Swiss company Futgen, and Pike Group acquired the British Sterling Hydraulic Company. Eaton Group acquired British integrated hydraulic company, Bosch-Rexroth Group acquired Italian oil control company, Sauer-Danfoss Group acquired Italian Comatrol company, and so on. Now, except HydraForce and Sun Hydraulics, all the world-class professional manufacturers of threaded cartridge valves have been acquired.

You mentioned that "the popularity of 3D design software and CNC machine tools has broken through the bottleneck of integrated block design and manufacturing technology". As far as I know, domestic 3D software is mainly used for hole calibration.

I want to know, do you still use two-dimensional drawings in the design of integrated blocks abroad? Is it a direct three-dimensional design?

Specializing in the design and manufacture of integrated blocks, I have been to Germany's Fluitronics, the German branch of SUN Company of the United States, the United Kingdom's Integrated Hydraulics and Sterling Hydraulics. Seven or eight years ago, without exception, three-dimensional software was used, such as NX, Solidworks, Solidedge, VEST and so on. , directly design the integrated block. Only by completing the three-dimensional design can two-dimensional drawings be generated. As far as I know, some domestic enterprises have all adopted 3D software to directly design integrated blocks, and an engineer can complete the complete design of an integrated block in a day or two.

For some complex control, the traditional hydraulic system circuit design is not easy, or even easy to really understand, but with the popularization of proportional valve technology and servo motor, will the hydraulic system circuit become simpler and simpler? So, for hydraulic system engineers, should we strengthen the study of electronic knowledge?

You are right. The rapid development of electronic technology, especially microprocessor technology, is bringing profound changes to hydraulic technology. The application of electro-hydraulic proportional technology is more and more. Just talk about the compressors and hoists I am familiar with in European garbage container trucks: in the middle range, the microprocessor is generally used to control the hydraulic system and exchange information with various electronic control systems on the truck chassis; High-grade, electric proportional valve, dynamic weighing, CAN bus, GPS satellite positioning and seven or eight microprocessors have been used for a long time. Garbage container trucks have reached this level, not to mention other advanced construction machinery. Faced with such a comprehensive electro-hydraulic control and drive system, it is difficult for hydraulic system engineers to cooperate with electrical engineers and programmers if they don't know some electronic knowledge, and it is difficult to do design or maintenance. Because hydraulic pressure is driven by pipes, the machine can't move, and it is always the first to doubt hydraulic pressure. Therefore, if hydraulic engineers can analyze the problem and convince mechanical or electrical engineers, life will be better.

Adopt electro-hydraulic proportional technology, servo motor and so on. The hydraulic system circuit may look simpler, but the technical difficulty is definitely increasing. Because both the electro-proportional valve and the servo motor have their own unique steady-state and transient characteristics, which are not so ideal. At present, the main purpose of this development trend is not to simplify the hydraulic circuit, but to improve the controllability, safety, adaptability and energy saving of the hydraulic system.

I read your book "Testing is the Soul of Hydraulics", and I deeply feel that China enterprises generally lack the attention to testing, and of course they may also lack the conditions. I hope you can introduce more about the establishment method, test method and test result analysis of the hydraulic test bench in the future.

Thank you for your encouragement. I will try my best.

Regarding the establishment of the hydraulic test bench, I want to say: aim at the purpose and do less fancy. Zu Xun said, "The layman looks at the excitement, and the expert looks at the doorway." At first glance, the test-beds in the Institute of Fluid Technology of Aachen University of Technology are in disorder. But it is here that the most advanced research in the world is going on, at least 5 years ahead of the current application to 10 years.

Test methods, don't be superstitious about standards, as long as you can measure differences. I am currently compiling a book "Hydraulic Threaded Cartridge Valve" (Mechanical Industry Press, scheduled to be published in the first half of 201/kloc-0). In this book, I intend to try to sort out the testing circuits and processes of steady-state and dynamic performance of various valves, hoping to give readers some help.

The analysis of test results, especially the analysis of test curves, is a great knowledge, and I am still learning. I can understand seven or eight points in some curves, while others can only understand three or four points. But I think this is more interesting and practical than playing with theoretical formulas that are divorced from reality, and it can solve practical problems and see practical benefits.

On the other hand, my personal strength is very limited, and there are still many talents in China. Professor Barker said that "engineering graduates must go to the industry first and work for at least five years before they can come back to apply for a professorship", which may be difficult to do at present in China. However, many hydraulic teachers in colleges and universities actively participate in practical scientific research or engineering projects, and have achieved results and gained practical experience, thus enriching the teaching content and improving the teaching quality. This is also a correct and promising road in line with China's current national conditions. I admire and respect them. They will train many excellent students and promote the development of China hydraulic industry.

What do you think of the future of fluid technology?

I think the machinery industry and hydraulic industry are the pillars of the national economy. If the machine is compared to human, then the steel member is equivalent to the skeleton of the machine, the hydraulic system is equivalent to the muscle of the machine, and the electric control is equivalent to the nerve of the machine. This model will become more and more popular and coordinated, and there will be no major changes for the time being. Because the two basic points on which hydraulic technology depends-higher energy density than electric transmission and greater flexibility than mechanical transmission-are not so easy to break through.

Now the hydraulic part of the fixed equipment is squeezed out by electric drive-servo motor and so on. That's because electricity can generally be obtained directly, and using water energy will result in one more energy conversion and one more energy loss. But this only happens on low-power fixed equipment. On those hydraulic presses with thousands to tens of thousands of tons, after 20 years, there will be no rivals for hydraulic pressure.

At present, the power of walking equipment basically comes from internal combustion engine, so whether it is electric drive or hydraulic drive, it needs an energy conversion. Therefore, electric drive has no advantage in this respect. I know that a European garbage container truck company received an order from a city, because the environmental protection party entered the city Council, and the garbage container truck must be electric, not hydraulic. It took a lot of effort to get it out, not to mention the research and development costs and assembly labor. The purchase cost alone, the electric drive control element is more than ten times that of the common principle hydraulic element, and its performance has been greatly sacrificed. Whether there is a future, all parties are skeptical.

Fuel cells and room-temperature superconductors were once highly expected, because fuel cells can directly convert the chemical energy of fuel into electrical energy, while room-temperature superconductors allow the current intensity to be greatly increased, thus greatly increasing the magnetic field energy density and greatly reducing the volume of electromagnetic actuators. However, it seems that after being hot for a while, it has cooled down again.

Even if one day, fuel cells and room temperature superconducting technology can enter the practical stage and can be applied to walking equipment, the application of hydraulic technology in walking equipment has been strongly challenged. By then, the service life of hydraulic technology will reach at least 65,438+00 years. Because the promotion of any new technology needs a gradual expansion process from point to surface, such a widely used technology as hydraulic pressure is not so easy to be replaced. Before this, how many new achievements will be made in hydraulic research and development?

Do you have any suggestions for our magazine?

I wonder if it is appropriate to hold a reader's forum to express readers' opinions, suggestions and comments on the manuscript? I think we need to encourage the spirit of discussion. Seeking truth from facts can spread out problems and distinguish right from wrong. Professor Barker always asks questions at academic seminars I have attended, whether it is a large international conference with dozens or thousands of people. Germans often use a proverb to encourage questions: there are only stupid answers and no stupid questions. I hope my answer is not all silly, and it can inspire readers and serve as the basis for further discussion.

Conclusion: After the interview, my biggest feeling is that I have confidence. Some foreign companies do have the first-Mover advantage, but we are closer to the market and users, so we should learn to make full use of our own advantages. Hydraulic industry is a relatively mature industry. Its race is not a 100-meter race, but a marathon. Now all the difficulties are temporary. As long as we are serious, pragmatic and persistent, we will certainly win in the competition.