Humans have set foot on the moon 380,000 kilometers away, and probes have landed on Mars 100 million kilometers away, but we still know very little about the ocean 10,000 meters deep. The sea is a treasure house, and the rich fish resources are the treasures that humans rely on for survival, but the phenomenon of "illegal fishing" that has occurred repeatedly during fishing and breeding has caused many fishermen to suffer huge losses. Two years ago, Malaysia Airlines flight MH370 lost contact, and the underwater search and rescue has not made any major breakthroughs so far.

The reporter learned from Beijing University of Technology that seven students from the School of Electronic Information and Control Engineering of the school, under the guidance of their teachers, have developed a "responding hydroacoustic digital remote-controlled diving buoy" with high performance and low price. The buoy dives underwater and accurately feedbacks fishery information through hydroacoustic communication technology to prevent "illegal fishing". The students imagine that this buoy can also be used in the field of marine search and rescue. If it is installed on civil aircraft, once there is a loss of contact in the water, it will greatly increase the efficiency of search and rescue in conjunction with the black box. This achievement won the second prize in last year's "Challenge Cup" Chinese College Students' Extracurricular Academic Science and Technology Works Competition, and is about to be put into production and put on the market.

Farming in the vast ocean

Preventing illegal fishing is a difficult problem

Wang Ruichuan is a senior student in the School of Electronic Information and Control Engineering and the person in charge of this research project. Born in a naval family, he has dealt with many things in the sea. "The most feared thing for fishermen in fish farming and fishing is that they lay out the nets and find that someone has already "taken the lead" after a day of fishing, so they have to return empty-handed."

How can we prevent "illegal fishing"? In the vast ocean, fishermen often rely on buoys on the water surface to locate their nets, which is also equivalent to tipping off others, "There are seafood here", and they cannot prevent villains. So the key is to hide the buoys and make them find themselves.

Because of his excellent academic performance, Wang Ruichuan joined Professor Wang Tieliu's laboratory through the school's Outstanding Student Program when he was a freshman. When he shared his confusion with Professor Wang, he found that his mentor had been researching in this field for many years. Wang Tieliu said that as early as the late 1990s, the fishing industry in Russia's Far East was trying to solve similar "illegal fishing" problems, but the difficulties were not small. He had previously participated in the research projects of diving buoys for the navy and central enterprises, but they were all supporting large-scale projects. A single buoy weighed dozens of kilograms and was worth hundreds of thousands of yuan, which was definitely not something that ordinary fishermen could afford. "Or you can try to make a civilian low-cost buoy." Wang Tieliu encouraged Wang Ruichuan.

The seven team members

Each has his own unique skills

Professor Wang's encouragement gave Wang Ruichuan confidence. But for an undergraduate student, it is not easy to develop an electronic buoy from software to hardware. He began to teach himself related knowledge such as single-chip microcomputer programming and communication principles.

As the research deepened, Wang Ruichuan encountered problems in designing circuit boards. At this time, he met Liu Gang, who was good at hardware design, and the two hit it off. Because he was very interested in circuits, Liu Gang's hardware circuit foundation just made up for Wang Ruichuan's shortcomings.

Wang Ruichuan said that in the early research, several graduate students in the laboratory provided great help to make the overall function of the circuit mature. However, in the second semester of the sophomore year, because the graduate students had to start preparing for graduation and job hunting, the two felt overwhelmed by the sudden increase in workload. "I stayed in the laboratory except for classes, but I still felt too busy." Fortunately, a group of "fresh blood" including Wu Mo and Yin Wei joined in soon.

During the research process, because the diving buoy is used in the deep sea, the design of the shell with a pressure resistance of 200 meters underwater became a difficult problem that must be overcome. At this time, Li Jin, who likes mechanical design, joined in and solved many problems. After repeated modifications to the mechanical design of the unlocking mechanism, the diving buoy can reliably perform mechanical unlocking under the control of the microcontroller. Before the competition, a 7-person R&D team was finally formed. "I feel that we have the talent we need, and we are very lucky to work with such a team." Wang Ruichuan and Wu Mo told reporters.

Building a pool to measure signals in the school corridor

Wang Ruichuan said that it is easy to sink the buoy to the bottom of the water, but it is difficult to accurately find the buoy and the net cage it is connected to in the wind and waves, because this involves underwater communication issues. The wireless radio frequency communication technology we have been exposed to in the past is powerless underwater. The teacher said that only sound waves are the most effective, so let's do underwater acoustic communication. "The speed of sound in the air is only 340 meters per second, but in the sea, its speed is greatly increased to 1500 meters per second. Otherwise, how can submarines use sonar for communication?" Therefore, they immediately decided to use sound waves to control the buoy's snorkeling and positioning.

As soon as the principle was determined, it immediately entered the actual research and development. But the problem came at the beginning, "We did communication remote control experiments in the air, and the success rate of buoy remote control was always very low." Ma Shuo, who participated in the circuit design, said that the students in the team were very anxious at the time because it meant that the reliability could not meet the requirements. "In order to solve this problem, we adjusted the program from morning to night, and often didn't have time to eat lunch." Fortunately, after a tough battle, this problem was finally solved.

The buoy is to be used in the sea, and it is definitely not enough to test it in the air. The team has to find water. They found the waterproof cloth used to raise fish in the aquatic market and set up a small pool with a diameter of one meter and a depth of one meter in the corridor. "Every day we keep putting the buoy into the water, testing it, and then fishing it out, repeating the cycle." Wang Ruichuan said that as the technology gradually matures and the signal becomes stronger and stronger, the experimental site will be changed to the artificial lake outside the building, "continuously debugging, trying different parameters, and repeatedly experimenting to ensure that all control programs can be successfully implemented."

Remotely controllable buoy within three kilometers

In the electrical experiment teaching center of Beijing University of Technology, the reporter saw the industrial sample of this "response-type hydroacoustic digital remote control diving buoy". The buoy is about 30 centimeters long and 12 centimeters in diameter. It is cylindrical and contains various circuit boards and cables. "After sealing, it can be submerged in the water." Wang Tieliu told reporters that today's students are very good and have independently developed a buoy positioning system with a liquid crystal display, which is very easy to operate. "After installing it on a fishing boat, ordinary fishermen can use it proficiently after a little training."

Reporters learned that in order to test whether the performance of this submersible buoy meets the requirements in different environments, researchers also went to the Yuqiao Reservoir in Jixian County, Tianjin and the Bohai Sea area of Shandong Peninsula. The results show that the buoy still has correct remote control capabilities within a range of 3 kilometers. This means that after the fishing boat lays the fishing net equipped with a submersible buoy, when it needs to fish, it only needs to issue a command within 3 kilometers of the buoy, and the buoy will automatically float up to "expose the target", and the fishermen can return with a full load by following the signal.

Wang Tieliu told reporters that the biggest advantage of this achievement is cost. Some similar products abroad cost more than 150,000 yuan, and military equipment costs hundreds of thousands of yuan, but the equipment developed by college students costs less than 29,000 yuan. "We have done tests and found that this set of civilian equipment can be made of engineering plastics. In this way, if it is mass-produced after the mold is opened, the cost can be greatly reduced, even to the level of several thousand yuan."

During the interview, the reporter mentioned the search and rescue of Malaysia Airlines flight MH370, which has been attracting much attention in recent years. Wang Tieliu told reporters, "From the bottom of the sea to the surface of the sea, the attenuation of infrared and electromagnetic signals will be particularly severe, but at a distance of several thousand meters, the attenuation of sound signals is very small." Such diving buoys are also promising in maritime search and rescue. In the event of a shipwreck or a plane crash at sea, the attached buoy can communicate with the search and rescue ship through hydroacoustic signals, quickly and accurately locate, and greatly speed up the search and rescue efficiency.