With the development of space industry, simulating the space suspension technology in microgravity environment has become an important means to carry out related high-tech research. At present, the suspension technologies mainly include electromagnetic levitation, optical levitation, acoustic levitation, airflow levitation, electrostatic levitation and particle beam levitation, among which electromagnetic levitation technology is relatively mature.
Electromagnetic levitation technology is called EML technology. Its main principle is to use the eddy current generated by high-frequency electromagnetic field on the metal surface to realize the suspension of metal balls.
When the metal sample is placed on the coil with high frequency current, the high frequency electromagnetic field will produce high frequency eddy current on the surface of the metal material. This high-frequency eddy current interacts with the external magnetic field, so that the metal sample is subjected to Lorentz force. Under proper space configuration, Lorentz force can be opposite to gravity, and electromagnetic force can be equal to gravity by changing the power of high frequency source, thus realizing electromagnetic levitation. Usually, the frequency of alternating current passing through the coil is104-105 Hz.
At the same time, Joule heat generated by eddy current on metal can melt metal, thus achieving the purpose of melting metal without container. At present, in the field of space materials research, EML technology has played an important role in the study of crystal growth, solidification, nucleation and deep supercooling in microgravity and containerless environment.
There are three kinds of magnetic levitation in the world at present. One is the normal magnetic levitation represented by Germany, and the other is the superconducting magnetic levitation represented by Japan. Both kinds of magnetic levitation need electricity to generate magnetic levitation power. The third type is permanent magnet suspension in China, which uses special permanent magnet materials and does not need any other power support.
[Edit this paragraph] Does China have magnetic levitation technology?
On August 17, 2006, the model of "Zhonghua 0 1" permanent magnet suspension road vehicle was unveiled at the 2006 China International Patent Technology and Products Fair held in Dalian. This model is a miniature simulation model of Dalian 3000m permanent magnet suspension test line, which is specially designed for regional traffic between cities. The train runs on the elevated magnetic track with a design speed of 230 kilometers per hour, which can be used for both freight and passenger transport, and is suitable for transportation in metropolitan areas.
According to the Peninsula Morning News, the "suspended" train, which can only be seen in novels and science fiction movies, will soon appear beside Dalian people. The reporter learned from yesterday's special Expo that the 3000-meter permanent magnet suspension test line is planned to be built in the development zone at the end of the year.
On the morning of August 17, 2006, at the "2006 China International Patent Technology and Products Fair" held in Dalian World Expo Plaza, the "Zhonghua 0110" permanent magnet suspension mini road bike with trough rail attracted special attention. The car is miniaturized according to the ratio of110, and the geometric size is miniaturized according to the actual car; Road and bridge structure, track structure, vehicle structure and suspension function are all simulated miniature models. Under the operation of technicians, the mini-train suspended on the track is very light and "running", and its starting and braking are very flexible and silent.
It is understood that there are three kinds of magnetic levitation technologies in the world, namely, Japanese superconducting magnetic levitation, German permanent magnetic levitation and China permanent magnetic levitation. Permanent magnet suspension technology is an original innovative technology with core and related technology invention patents in Dalian, China. According to the technicians, the maglev trains in Japan and Germany are in contact with the track without electricity, while the maglev trains manufactured by permanent magnet suspension technology are not in contact with the track under any circumstances.
Compared with foreign magnetic levitation, China's permanent magnetic levitation has five advantages: First, it has strong levitation. Second, it is economical. The third is energy saving. Fourth, safety. Fifth, balance and stability.
The permanent magnet suspension of slot rail is specially designed for regional traffic between cities. The train runs on the elevated track with a design speed of 230 kilometers per hour, which can carry both passengers and goods. Su Xun, general manager of Dalian Cigu Science and Technology Research Institute Co., Ltd. told reporters that the 3000-meter permanent maglev train line is expected to be completed by the end of this year, and the location is planned in the development zone.
[Edit this paragraph] Maglev train
Based on the principle of "like-sex repulsion and opposite-sex attraction", the maglev train makes the magnet have the ability of defying gravity, which makes the car body completely off the track, suspended at a distance of about 1 cm from the track, and flew in the air, creating a miracle of space flight with almost zero height.
Shanghai maglev train is the first demonstration operation line of maglev train in the world. After completion, it only takes 6-7 minutes from Longyang Road Station in Pudong to Pudong International Airport.
Shanghai maglev train is a kind of "constant magnetic attraction type" (referred to as "constant conductivity type"), which is designed according to the principle of "opposites attract" and is a suction suspension system. The suspension electromagnets installed on the bogies on both sides of the train and the magnets laid on the track are used, and the vehicle is suspended by the suction generated by the magnetic field.
Electromagnets are installed at the bottom of the train and at the top of bogies on both sides. The induction plate and the induction steel plate are respectively installed above the I-beam track and below the upper arm. Control the current of electromagnet to keep a gap of 65,438 0 cm between electromagnet and track, and balance the attraction between bogie and train with the gravity of train. By the attraction of magnets, the train can float about 65,438+0 cm, and the train can be suspended on the rails. This must accurately control the current of the electromagnet.
The driving principle of suspension train is exactly the same as that of synchronous linear motor. Generally speaking, the alternating current flowing in the coils on both sides of the track can turn the coils into electromagnets, and the train will start because of the interaction with the electromagnets on the train.
The N pole of the electromagnet at the head of the train is attracted by the S pole of the electromagnet installed on the front track and repelled by the N pole of the electromagnet installed on the back track. When the train moves forward, the current in the coil flows in the opposite direction, that is, the original S pole becomes the N pole, and the N pole becomes the S pole. When the cycles alternate, the train will run forward.
Stability is controlled by the navigation system. The "constant magnetic attraction" guiding system is a group of electromagnets installed on the side of the train for guiding. When the train deviates from the left and right, the guide electromagnet on the train interacts with the side of the guide rail to produce repulsive force, which makes the vehicle return to the normal position. When the train runs on a curve or ramp, the control system can control the operation by controlling the current in the guide magnet.
The idea of "normal guidance" maglev train was put forward by German engineer Herman Corpster in 1922.
"Normal-oriented" maglev train, the working principle of track and motor is exactly the same. Just arrange the "rotor" of the motor on the train and lay the "stator" of the motor on the track. Through the interaction between "rotor" and "stator", electric energy is converted into positive kinetic energy. We know that when the "stator" of the motor is electrified, the "rotor" can be driven to rotate through electromagnetic induction. When the power is transmitted to the "stator" of the track, the train is driven to move linearly like the "rotor" of the motor through electromagnetic induction.
Shanghai maglev train runs at a speed of 430 kilometers per hour, and only one train can run in one power supply area. There are isolation nets at 25 meters on both sides of the track and protective equipment on both sides. The radius of the bend is 8000 meters, and the naked eye is almost a straight line; The minimum radius is1300m. Passengers will not feel uncomfortable. The most advanced isolation devices in the world are installed within 50 meters on both sides of the whole track. The Shanghai line will eventually extend to Hangzhou. And directly serve the World Expo.
[Edit this paragraph] Advantages of maglev train
Maglev train has many advantages: the train is suspended above the rail, and the rail is not in contact with the vehicle, which is not only fast, exceeding 500 km/h, but also stable and comfortable, and easy to realize automatic control; No noise and harmful waste gas, which is beneficial to environmental protection; Can save construction funds; Low operation, maintenance and energy consumption costs. It is an ideal super express train in 2 1 century, and all countries in the world attach great importance to the development of maglev train. At present, China, Japan, Germany, Britain, the United States and other countries are actively studying this kind of car. Japan's superconducting maglev train has been overloaded with people and is about to enter the practical stage, running at a speed of more than 500 kilometers per hour.
Up to now, it can be said that the track technology of maglev train is in China and the technology of maglev train is still in Germany, so it is impossible to introduce technology from imported products. China's wheel-rail railway technology has a history of nearly a hundred years, forming an industrial force specializing in locomotive design, scientific research and innovation, with an industrial chain of more than 400,000 people who have designed, manufactured, operated and maintained for decades. Magnetic levitation technology is in the hands of a few experts and professors and does not have the application conditions. The maglev train needs to be elevated, and the winding of the elevated beam must be less than1mm. Therefore, the span of viaduct is generally less than 25m and the depth of pier foundation is more than 30m. Therefore, from Shanghai to Hangzhou, more than 200 kilometers of retaining wall should be formed on the ground. In addition, due to the influence of operation dynamics, no other buildings are allowed within the range of 100 meters on both sides of the track. Shanghai-Hangzhou maglev construction covers a large area and has a great impact on the environment.
[Edit this paragraph] Disadvantages of maglev train
In 2006, a German maglev control train collided with a maintenance vehicle during its trial operation. It is reported that there were 29 people on board, 23 people died on the spot, 25 people actually died and 4 people were seriously injured. This shows that the braking ability of maglev train in emergency is not reliable, which is not as good as that of wheel-rail train. It is dangerous for vehicles on land to have no wheels. Because the train has to drop from a great momentum to a standstill, and to overcome a great inertia, it can only be overcome by the braking force of wheels and tracks. Maglev trains have no wheels. It is very dangerous to rely on sliding friction if there is a sudden power failure. In addition, the maglev train is elevated, and it is difficult to rescue at a height of 5 meters when an accident occurs. Without wheels, it is difficult to drag it out of the scene of the accident. If there is a power outage in the section, it is difficult for other vehicles and cranes to get close.