Professor Fei Yetai: 60 Years in Pursuit of Real Data


Trailblazer of Precision Theory in China 

—by Zhouhui

Professor Fei Yetai was awarded among the “Ten Figures Touching HFUT” since the founding of this university. The honorary alumnus Jia Chengbing, former Chairman of the Supervisory Board for Key Large State-Owned Enterprises, State-owned Assets Supervision and Administration Commission was giving the award to Professor Fei.

China's breakthroughs in high technologies in recent years, whether the Shenzhou 10 Spacecraft or the manned submersible Jialong, are inseparable from the precision instrument discipline, in which error and precision theories and technology constitute a major role. There is an old man who devoted nearly six decades to precision instruments and made outstanding contribution to the development of the theories. He is renowned as the trailblazer of the precision theory in China. 80 years old as he is, he is still working in the laboratory. He is Professor Fei Yetai from School of Instrument Science and Opto-electronics Engineering, ICMI Lifetime Contribution Award winner in 2007.

“I spent my entire life with a pair of antonyms —‘precision and error’”

“A minimal error or deviation may result in wide divergence”. Human beings have to carry out measurements and calculations on different phenomena in the nature constantly whereas the data from the measurements and experiments are invariably deviant from the true value due to limited experimental equipments, environments and human cognition. Even though people are narrowing down errors with advanced science and technology, errors still exist. What Professor Fei pursues in his lifetime is to eliminate errors incessantly so as to obtain the true value with a great precision.

Professor Fei was graduated from HFUT in 1955, where he started his career as a teacher. In 1959, he was transferred from the discipline of mechanical manufacturing to the newly-established discipline of precision instrument. The discipline of precision instrument meant everything to him ever since.

Precision is the fundamental guarantee of modern precision engineering. In the age of IT technology, the large amounts of data gained from any scientific experiment or engineering practice would only be of real value after undergoing proper data processing and scientific evaluation. However, China didn’t have a systematic theory on precision and error in the early years of initial industrial development but relied on copying the foreign modes. The awareness of precision was severely deficient alongside the booming development of mechanical industry. At that time, the newly-opened teaching and research facilities on precision instrument in HFUT lacked materials, equipments and even knowledge. All of the teachers were transferred from the discipline of mechanical engineering.  

Everything is difficult at the start. As the director of the teaching and research section, Professor Fei was very conscious of his duty. “I spent my entire life with a pair of antonyms —‘precision and error’”, said he. He has been working around the clock in the labs and offices since then, sacrificing weekends for years and only had a one-day rest on the first day of Lunar New Year. The error correction experiment on precision instruments is an arduous work. As precision instruments are extremely sensitive to interference sources, even a subtle tremor of the floor would affect the stability of the data. To ensure the quality of experiments, he usually grabbed a quick bite on bread for dinner and spent his night in the lab for experiments.

A human hair is between 70 to 100μthick. The average precision of grating measure in China is 5μ. In the early 1980s, the “grating meter measurer” mainly developed by Professor Fei substantially enhanced the precision of the instruments by adopting the modeling of comprehensive error analysis based on multi-error sources, thereby breaking the limits from traditional single-error modeling and correction. As tested by Chinese Academy of Computing Technology, the measurer reached 2.3μ in one meter, reaching the level of top products abroad, making it a monumental achievement in China’s precision instrument discipline.

On this basis, Professor Fei conducted comprehensive and in-depth studies on the application of the error theory and achieved a series of research results that comprehensively improved the error and precision theory in China. Based on the dynamic characteristics of modern instruments, Professor Fei proposed the dynamic precision theory and the shedlike model for dynamic precision loss, and set up the system-wide dynamic error analysis modeling method. In doing so, he further disintegrated and sought the source of dynamic system loss function, analyzed the rules for precision loss in the different units of the dynamic system, and put forward the theory and method of system-wide uniform design based on equivalent loss of different units, all of which are major processes in China’s error and precision theories.

“We are all guided into the field of precision instrument by your books.”— these words are frequently heard by Professor Fei at high-level instrument science conferences in China. Professor Fei published 9 books, of which his Error Theories and Data Processing published in 1981 was listed as national key textbook that opened up the field of precision instrument theories. This textbook was reprinted for six times in the past 30 years and more and was adopted by over 200 Chinese universities. The course has even been chosen as a required course for students majoring in Measuring & Control Technology and Instrumentations or the likes. The new generation of talents in instrument science all read his books before. Therefore, Professor Fei is reputed as the trailblazer of Chinese precision theories.

I always seek perfection in my studies on precision instrument science”

Professor Fei undertook and accomplished nearly 49 high-level scientific research projects in the past 40 years including 17 projects supported by the National Natural Science Foundation of China. He published over 320 papers and won nine awards of provincial and ministerial levels. A lot of his books and papers are recognized by the academic circles, solving a large number of practical problems in many national key scientific research programs.

The components in the instrument would expand with heat and contract with cold, and some of these variations my affect the normal functionality of the instrument. To get a clear picture of this rule, Professor Fei spent days and nights in the labs on hot deformation experiments with high intensity and long duration. Through analyzing huge volumes of data, he found that the outline dimension of some components may even contract as temperature rises. To seek a scientific explanation of these special physical phenomena, he conducted an in-depth study that ultimately led to the innovative thermal error theory based on the characteristics of the error of instrument measurement and their influence on precision, and broke the restraints of the traditional theories. Through the design of the thermal deformation volume of the instrument body, this theory guarantees minimum thermal deformation, thus improving the efficiency and quality of different industrial products. His precision error theory has already become the basic method of precision evaluation and the theoretical basis of precision instrument studies. The thermal error theory also becomes one of three classic directions of this field.

As a spacecraft flies in the outer space, its two sides are exposed to different temperatures. There would be hundreds of Celsius degrees’ difference between the sun-facing side and the dark side along with the problem of varying expansion of different materials. What kind of material would ensure the normal functioning of the satellite is a longstanding issue for China. The official in charge of one satellite development agencies approached Professor Fei with this problem. Based on scores of experiments, Professor Fei identified significant problems in the application of national thermal expansion coefficient. “There exists great deviation in expansion volume the same material in different outline dimension. Experimentalists used cylinders to measure the expansion volume to set the national thermal expansion coefficient, which gave an inaccurate reflection of the deviation.” In this connection, he made an innovative move by applying spherical objects in setting up the thermal expansion coefficient that would faithfully reflect the properties of materials without influence from the outline dimension of the materials. That became the foundation of the brand-new thermal error theory.

Similar problems surfaced when China was building the Three Gorges Dam in early 1990s. Since the motors were produced in Harbin, the freezing city in northern China, they would inevitably experience major errors in internal catenation devices due to sharp temperature difference that would even affect the normal functioning of the motors. “We cannot afford any mistake because this project is a matter of life and death.” With that in mind, the leaders of the Harbin Electrical Machinery Plant turned to Professor Fei, who quickly solved this problem by applying the thermal deformation theory, ensuring the smooth proceedings of this important project.

Professor Fei’s precision theory has already penetrated into every aspect of China’s modernization drive for over half a century. China once experienced misconceptions that all of the components should be as much precise as possible. In terms of this, Professor Fei took the lead in his proposition that “Best components do not necessarily produce the best property.” Through numerous experiments, he found the rule of error transmission and thus put forward a new method which advocates optimizing grouping of components instead of pursuing absolute precision in each and every component. The method has later become an important part of China’s latest precision theory.

The Modern Precision Engineering R&D Center in HFUT was founded by Professor Fei, whose dozens of projects supported by National Natural Science Foundation of China were all carried out in the center. All of the precision-related laboratory instruments were made by himself. Over 40 academicians, renowned scholars and officials from the central government have visited this state-of-the-art center with countless accolades to him. The center has always been open to the public as insisted by Professor Fei. For many years, many PhD students who lacked the suitable experimental conditions have been allowed to accomplish their experiments there.

“Self-conduct Comes before Scholarship”

Professor Fei has already guided over 100 PhDs or masters in his past 60 years as a teacher. He remained stringent on both students and young teaches with high standards and strict demands, both academically and morally. He even did everything himself to ensure the quality of talents.

All of his students were guided under his motto — ”Diligent, realistic and humble in studies”. It is believed by Professor Fei that diligence is the primary requirement of scholarship; being realistic is the building block of successful teaching and R&D; humility is the propellant to breaking limits and turning barriers into supports. For over 60 years, Professor Fei has been interpreting this motto through his own deeds. With this spirit, he strived to build a favorable academic environment in the academia. He was invited to Taiwan for academic exchanges, visits and lectures for over 10 times, bringing the scholars across the straits closer for academic exchanges. His moral integrity also won the recognition and support from the academia in Taiwan.

“Professor Fei kept pushing us to engage in high-level projects, throwing tasks at us, and ‘forcing’ us to submit papers to first-rate journals.” said by a young teacher. In guiding young teachers on project application, Professor Fei would examined all application documents, without letting go of any details.

With stringent supervision from Professor Fei, his students would also be under his meticulous care in personal life. Professor Fei was always concerned about his students. He would manage to win more subsidies for those students with poor family conditions and prepared refrigerator and microwave oven in the labs so that students wont’ starve. He was even a middleman sometimes who introduced students to each other who finally tied the knots.

“A research should not consider interests but academic demands.” These are the words that are repeatedly mentioned by Professor Fei. He is thrifty in his own life and seldom receives any gift. But a flashlight is held as precious by him. It is a gift from his student. For some period in the past, he had his office at the 7th floor. Because he always got off work late at night, he had to manage to go downstairs in darkness since lights have already been shut off on campus. At his 65th birthday, his postgraduate students sent him a flashlight as a birthday gift. This flashlight not only light sup his way home, but also reflects his lifetime principle — “sacrificing himself but lighting up the others”. Professor Fei would always bring some gifts home after he returns from his official visit elsewhere but those gifts are for the gatekeeper of the school because the gatekeeper has to get out of bed to open the door for him late in the night.

Thrifty as he is, he never saves any money on the funds for students even if he would save his fund for studies.

In 2008, Professor Fei retired at the age of 74. But his life remained the same: spending the day at the labs and the night at home.

Unfortunately, he was diagnosed with kidney tumor that year. After the surgery, he didn’t forsake his career as well but has been working at the labs since then.

One day in 2011, the 77-year-old professor was anxiously waiting for the plane back to Hefei after he finished his work at a national project argumentation in Beijing. As Beijing was struck by a rainstorm that day, the plane had been held off until 11 p.m. His students were worry about his health so they persuaded him to stay for another night. But he insisted going back soon because he had an important thing to do. Therefore, the students accompanied him to the Beijing Railway Station and the Beijing Railway South Station, yet they couldn’t get a ticket instantly. In the end, professor insisted waiting at the airport. The plane finally took off at 4 a.m. the next day. Upon his arrival at Hefei at 7 a.m., he rapidly threw himself into his work. It was then that his students found out that what the professor claimed important was his appointment with a postgraduate to edit a paper.

It is his incessant arduous work that helps him attain his status in the field of precision instrument. He has been undertaking several academic posts concurrently, including the standing member of International Committee on Measurements and Instrumentation (ICMI), chairman of National Error and Uncertainty Research Council, honorary member of China Instrument and Control Society, member of China Society for Measurement and the deputy director of its affiliated Commission of Geometric Measurement, etc. Under his efforts, the discipline of precision instrument in HFUT has taken a leap from a one of no mark to a leading one in China with a complete system from undergraduate to PhD studies.

Today, Professor Fei still remains committed to his work in the labs at the age of 82. He is still busy attending major academic conferences and contributing his share to precision instrument. In HFUT, his achievements have gone beyond his scholarship, with great implications for us to learn from.