Chapter 658: Match up

"The multi-rotor system, as the name suggests, is a special helicopter with three or more rotor shafts in the entire flight system."
Lu Hesheng only sorted out his thoughts and began to tell: "The earliest known multi-rotor system was manufactured by the Gaul Breguet brothers under the guidance of Professor C. Richet in 1907. This time is only the first time that humans are officially recognized. The flight was less than 4 years late, but although the aircraft was tested, the results were not satisfactory. It only flew 1.5 meters. The only good news is that the aircraft and the test flight left clear text. And the picture record also made it the earliest multi-rotor aircraft."
Speaking of this, Lu Hesheng could not help but sigh slightly: "At the beginning of the twentieth century, the human aviation industry had just sprouted. The people at that time were enough to make us ashamed today. Among them, there were countless geniuses and lunatics who wanted to fly. They are inspiring them to try all kinds of solutions that may seem incomparably absurd, just to send themselves to the blue sky. Many people even paid the price of their lives for this, but unfortunately, we missed the gold era."
He shook his head slightly, aroused by his own words, and felt a little sad for a while, but Tan Zhenhua said loudly: "China has missed the first golden age of the aviation industry because at that time, Huaxia people were trying to cut their brains. After the braids, break the shackles in my heart, and I think that for a nation, that is the most important thing."
Lu Hesheng gave Tan Zhenhua a surprised look. Instead of picking up his voice, he continued to say after a moment of silence: "The unsuccessful flight of the Breguet brothers did not extinguish people's enthusiasm for the pursuit of helicopter-type aircraft. Instead, it inspired. The creativity of the pioneers, they tried a variety of solutions, and finally achieved a breakthrough in 1920, another Gaul engineer Etienne Oehmichen designed a multi-rotor aircraft successfully took off and achieved a 14-minute flight, creating the time A world record in the field of helicopters."
"It's been 14 minutes, and it's still manned. It's amazing!" Tan Zhenhua sighed and asked, "What happened later?"
"Later, there were differences in the development of this type of aircraft." Lu Hesheng replied: "With the increase in the output power of a single engine, people found that vertical take-off and landing can be achieved without the need for a multi-rotor system. On this basis, they developed in-depth, and finally It has evolved into a modern helicopter, and some others continue to explore the future of multi-rotor systems. However, since our topic today is focused on multi-rotor systems, the helicopter is not to be discussed."
Tan Zhenhua nodded, and Lu Hesheng continued: "In the 1950s after World War II, the U.S. government felt that it needed a vertical take-off and landing aircraft with greater capacity than helicopters, so they approved the U.S. Army. Among the series of research projects, the most successful one should be the "flying jeep" of Curtiss-Wright, which uses lever gas turbines as power. Among them, the "Curtiss-WrightVZ-7" was realized during 1959-1960. More stable and controllable flight."
"Since stable and controllable flight was achieved in 1960, why do you still say that this multi-rotor structure is a classic problem?" Tan Zhenhua asked curiously.
Lu Hesheng glanced at him and said slowly: "Because this research project finally stalled."
"Why? It seems that this Curtiss-Wright company has achieved phased research results?"
"Because after a period of test flight, people discovered some inherent shortcomings of this multi-rotor structure, and these shortcomings are almost fatal to a manned aircraft." Lu Hesheng replied.
When it comes to Tan Zhenhua’s blind spot of knowledge, he has no choice but to listen to the explanation of Mr. Lu:
Take your 4-rotor structure as an example. First of all, from the aerodynamic point of view, the 4-rotor structure must be statically unstable. That is to say, even if the power, speed, and lift of the four motors and the propellers are exactly the same, the center of gravity is also at the absolute center point, but as long as there is a slight disturbance, the four-rotor system will deviate from the equilibrium state and cannot Rely on the aerodynamic layout itself to restore balance."
After all, Tan Zhenhua also followed the two China Airlines big names as disciples for a few days. He still understands the word "quiet and unstable", and after all, he personally produced the world's first real one. 4 Rotor UAV system, recalling the enormous energy it took to fix the center of gravity on the center point when making the prototype, I couldn't help but nodded sadly.
Seeing him nodding, Lu Hesheng continued: "In order to solve this problem, the quadrotor system needs to be equipped with a whole set of negative feedback system of "attitude sensor-flight control-engine" to maintain the balance of the aircraft. This system either uses a conventional helicopter. The complex control mechanism of the rotor either used the method of precisely controlling the engine speed and then changing the propeller lift to maintain a balanced state, and both of these solutions had almost insurmountable obstacles at the time."
He didn’t wait for Tan Zhenhua’s question to directly explain:
It is certainly feasible to use the complex control mechanism of conventional helicopter rotors, and there are also ready-made methods that can be applied-but it is obviously superfluous to make such a scheme based on the existing helicopter. It makes no sense at all. The rotor system can almost be regarded as the core and most expensive part of a helicopter. Installing 4 sets of such systems on a single aircraft cannot achieve the same efficiency as the cumulative effects of 4 helicopters. The plan, at least economically speaking, has no practical significance."
Tan Zhenhua nodded slightly. Indeed, Lu Hesheng was right. From the perspective of cost-effectiveness, this first option is indeed worthless.
"So what about the second one? Isn't it feasible to precisely control the output of the engine?" he asked
"Of course it is not feasible." Lu Hesheng replied: "The internal combustion engine, whether it is a piston, a turbojet, a turbofan, or a turboshaft, is limited by its working principle. It is impossible to achieve precise power output control or to be more accurate. , The accuracy of this control is not enough, so you can imagine how hard it took the original "flying jeep" to achieve controlled long-term flight, but this effort wanted to transform it from a laboratory environment into It is unknown how many engineering and technical obstacles are insurmountable for mass production."
"The motor should be possible, right?" Tan Zhenhua couldn't help but interject: "The motor is easier to achieve precise control, and on my small 4-rotor, this solution has been proved to be feasible."
"Yes, motors are possible, but in the 1960s, such motors were almost impossible to obtain. What's more, in order to adapt to the complicated flight envelope, a central control mechanism or a special attitude adjustment center computer was required to take charge. To control the output of each motor, this obviously requires the central computer to have strong computing power, and it is also necessary to formulate the power output plan of 4 independent motors according to the various situations that may arise-and this obviously requires one Powerful computers were available in the early 1960s. Where did we get such microcomputer systems?
Tan Zhenhua suddenly realized: "I used a z80 CPU and a piece of flight control code to complete all this, but the Z80 was not designed at all at that time. At that time, the computer was simply a model of slow development and timelessness. It’s the Z80 I’m using now, and its computing power is probably not enough to meet the calculation requirements within the flight envelope of manned aircraft.

Lu Hesheng replied approvingly: "Eric, what you said is right, this is enough to cause headaches, but the defects of the multi-spin system are more than that."
To be honest, even Tan Zhenhua’s two major Chinese aviation industry teachers Guo Rongwei and Song Wenhua, I am afraid that the understanding of the multi-rotor system is not as deep as the old man Lu, after all, he is not only the big cow of the US aviation industry, Grumman After Tan Zhenhua had tossed out the 4-rotor, in order to respond to the CIA’s bid for the program, he conducted a deep research on this type of aircraft, so at this moment, it is really piles and pieces, and it is clear.
The old man was willing to say that Tan Zhenhua would like to listen. Xu Xin, who had been sitting and observing for a long time, found that the older and younger became more and more in love each other.