Analysis of 2019 National Competition Questions: Questions F, H, and K

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Analysis of 2019 National Competition Questions: Questions F, H, and K [Copy link]

The following is a retelling of one of our netizen D’s analysis of questions J and H in the national competition.

Question F: Paper counting display device

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F题_纸张计数显示装置.pdf (184.97 KB, downloads: 139)

2019-8-7 09:47 上传

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Question: Can this topic be understood as the basic function of a money counting machine?

D's answer: No, this is much better than a money counting machine that doesn't require any brains.

This consideration is the knowledge of capacitance measurement. In fact, it is to calibrate the dielectric constant according to the change of capacitance, and then assume that the dielectric constant remains unchanged and reversely calibrate the substrate distance.

Then find the number of papers.

This involves a slightly complicated scientific calculation. One problem is that it assumes that the dielectric constant of the material remains unchanged. If the paper is toxic, then it will be a disaster.

Q: What if the plate material is not good?

Answer: It has little to do with the substrate material. The substrate material can be considered a constant parameter, so you only need to calibrate the dielectric constant and distance, and at most add error correction.

A: There is a certain error when it is close to the plate.

B: Speaking of this thing, the conditioning circuit is an LCR capacitor

C: FDC2214 is a TI chip. Once the chip driver is ready, it will be much easier to adjust.

D: The main thing is that the performance of the front end must be sufficient. Otherwise, if the accuracy is not enough when calibrating the relative dielectric constant, it will be very troublesome to compensate later.

Questions H and K: Simulating electromagnetic indirect-fire guns

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H题_模拟电磁曲射炮.pdf (225.76 KB, downloads: 86)

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Question: This year, both the undergraduate group and the higher vocational group have a topic on simulating an electromagnetic indirect projection gun. Is there any difference?

D: There is no difference in the title, the requirements are the same.

This is a national defense question. Actually, the requirements for accuracy seem to be higher than the realization, and there are more things to consider.

It is necessary to correctly consider the effects of charging, trajectory, and projectile. Moreover, this type of projectile is largely suitable for electromagnetic gun weapons used by the navy. In fact, the requirements for actual circuit design are not very high, except for precise charging.

In fact, I think precise charging is not particularly necessary, and it can be corrected by correcting the launch angle. It is necessary to consider the design of the projectile, the flight trajectory, trajectory correction, and the suppression of projectile tumbling, which is similar to considering the basic physics, but it is relatively complicated.

showgu

Our solution is to use a boost circuit to raise the voltage to a certain level, and then discharge it instantaneously. The discharge is controlled by a thyristor. The boost part can be ZVS, or it can be an inverter boost, or other methods. We make a voltage closed loop, charge it to the set voltage each time, and then make a relationship between the path and the angle, perform curve fitting, and obtain the corresponding function relationship. It is worth noting that with continuous firing, the bullet will be magnetized, the coil will heat up, and the switching device will also heat up, which will affect the consistency of the photo. This needs to be overcome in practice. As for the target, we use a camera that can read the distance and calibrate the angle. The gimbal part calibrates the angle.

showgu

Question F also uses TI's solution and FDC chip. At that time, I wanted to use 555 square wave to measure capacitance. I did this after doing FDC last year. This question should not be difficult. It is mainly a matter of details. I don't know how strong the opponent is. Then I feel that I can do it well. It is still difficult to do it very accurately.

showgu

As for the creativity part, I couldn't think of any other ideas, so my classmates made a money counting machine. I don't know if it will be recognized.

qiushenghua

Didn’t TI say that its products cannot be used in military applications? How could it be possible to ask questions about national defense?

sjl2001

qiushenghua posted on 2019-8-13 10:36 Didn’t TI say that its products cannot be used in military applications? How could it be possible to ask questions about national defense?

This cannon poses no threat at 3 meters.

generalcircuits

Question F is a question about counting money. There may not be many people, and it is easy to implement.