Explain how sensor technology on rotary wing aircraft part two

Lei feng’s network (search for “Lei feng’s network” public attention) by writer YY Shuo, from Xinjiang engineers. This article is divided into two articles, article links on here.

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2014 in June, I know “civilian UAV sales and prospect of what? -YY Shuo replied: “the question publish an article popular science multi-rotor aircraft technical answer, has obtained 889 in the know agree, close to 100,000 views and were forwarded by dozens of media outlets and the general public. 2014 multi-rotor aircraft market in the years before the outbreak of air, many friends tell me that it is precisely this attracts them into a number of rotary-wing aircraft industry.

Two years ago, Xinjiang Elf series updated for two generations, and updated flight control technology for two generations, and smart navigation technology from scratch, many new software and hardware products released. We also have many friends, hot market now rotary wing aircraft, many products, prices vary. In order to understand the difference between these vehicles, we must first understand the sensor technology for use on aircraft. I think now it is necessary to send a popular science article, defining “smart navigation” concept, by the way the lines about two years of Xinjiang’s efforts in sensor technology.

Text:

4. the Elf 4 sensor iPhone 6 plus cases hello kitty

Xinjiang implemented on Elf 4 binocular stereo vision system and inertial measurement unit Visual odometry, installed two sets of stereo vision system for aircraft, a look forward, look down, and there are four cameras.

Explain how sensor technology on rotary wing aircraft (part two)
Explain how sensor technology on rotary wing aircraft (part two)

Two sets of binocular stereo vision system are involved in Visual odometry calculation. Typically of binocular stereo vision system to look down, and if looking down the camera at some obscure environment (such as solid floors, sea, etc), feel the image changes, Visual odometry stereo vision system automatically switches to the forward-looking measure. Although Elf 4 using machine vision technology is more mature, but because of the Elf airborne computation is very limited on the 4, Jiang is still quite a long time of hard work optimizing algorithm and uses Movidius company making algorithm of image processing chip, combined with Movidius’s library of image processing algorithms optimized four-channel image processing performance.
It is worth mentioning that soon will launch Google
Project Movidius Tango also uses the company’s chips. But because Movidius algorithm does not contain Visual odometry company chip, so Google’s product Visual odometry algorithm with ELF 4 algorithm is quite different.

Two sets of binocular stereo vision system also offers two advantages besides Visual odometry: 1.
Looking down a binocular stereo vision system of three dimensional position can be detected on the ground below, so as to know the ground distance; 2. Forward-looking set of binocular stereo vision system can be used to detect the depth of an object in the scene ahead, barriers perceived depth chart. Depth map can also be used to rebuild a local map around the aircraft, with fine motion planning, this is the Elf 4 pointing flight basis, not described in detail in this article.

Explain how sensor technology on rotary wing aircraft (part two)

Apart from increasing beyond Visual odometry, Elf 4 also adds built-in ultrasonic module. So Elf 4 on a total of GPS+ IMU + barometer + geomagnetic compass + binocular vision system + ultrasonic module six sensors. There are two sets of binocular vision system, all 4 camera inertial measurement unit has two, dual redundant; magnetic compass has two same double redundancy. When working in the IMU or when serious disruptions to the magnetic compass, the system will automatically backup switch, switch to another sensor. The number of these sensors, features and summarized in the following table:

Explain how sensor technology on rotary wing aircraft (part two)

After these sensors, integrated navigation systems upgrade to become an intelligent navigation system. Smart navigation technology greatly extends the space of aircraft activity, when there is GPS when 15 State system by GPS measurements, Visual odometry is still can continue to operate, providing additional value to improve the precision of measurement of velocity and position; when the GPS signal is bad, Visual odometry replace the GPS observation of stability for the entire system. Intelligent navigation system there are three determining height of sensor: ultrasonic, pressure gauge, binocular vision, three sensors cover almost all the traditional headaches of rotary wing aircraft fixed-height: above the trees, Interior, close to the building, wind conditions, and so on.

Redundant design of the magnetic compass can be reduced to a large extent a compass fault from external magnetic interference. May of course was given visible Visual odometry, complementary to both improve the accuracy of course. In previous aircraft, bombing due to interference of magnetic compass issues more, because of multiple protection measures at the Elf 4, magnetic compass interference caused the problem has greatly reduced.

With smart navigation system, you also need to have a powerful software system to organize navigation algorithms and flight control. Elf 4 flight control and the latest A3 flight control is similar, is the third generation frontier flight controllers. Jiang Wang Tao himself wrote the first flight control, performance is very good, and flight control in the past few years has made two big reconstruction of the flight control software systems, sensors and to support more functions. 2014 launch at the end of the second generation joined the optical flow velocity measurement in the flight control modules support, SDK, restricted flying area and novice mode functions in early 2016 developed third-generation adding redundant flight control sensors, binocular vision support, avoidance and smart home functions. Because in every reconstruction of the entire software system to do a massive adjustment, adding lots of new software architecture and software modules, so for three generations. Others started when flight control, Xinjiang is refactoring the code twice himself, which is one of the most proud of Xinjiang.

Elf 4 intelligent navigation systems in any State can accurately measure their three dimensional position and velocity, which has very important significance for functionality.

In recent years, the industry there are many avoidance should be using binocular stereo vision or the controversy of laser radar sensors and other sensors. In Xinjiang, choose what kind of sensor in the intelligent navigation system for obstacle avoidance, protracted discussion on the engineering team, and finally select the binocular stereo vision programme. I believe that with the development of science and technology in the future will continue to have more and better new sensor was born, is likely to have other sensors instead of binocular vision, but stability is not used in avoidance of obstacle avoidance sensors. Obstacle avoidance before and after this incident, aircraft brakes body must occur, whole will experience a lot of attitude and Acceleration, in this case, if aircraft can stably measure out his 15-State weight, is the impact on security issues.

If the system after the brakes, the overall observation speed observation even divergent, this time around aircraft could float out, or will it blow up. If not blow up, after avoidance before and after the plane from side to side, will also give the user psychologically insecure feelings, very poor user experience. Elf 4 occurs in many harsh avoidance actions, the aircraft will automatically lock position, quickly reduced to 0 State, will soon be able to recover completely from the high-speed fixed, very stable hover, avoid the obstacle near the instability caused by bombing.

https://www.youtube.com/watch?v=xuEvjrM8Y-w

Elf 4 plus lots of seemed very simple, but very high requirements on sensor system of flying scenes. For example more than 10 storey window hover the aircraft flew from indoor to outdoor. Under such a scenario, when out from the window, looking down the sensor failure almost immediately, due to the construction of shelter, GPS will not take immediate effect, the sensor system was not robust enough aircraft could lose speed and position measurement of wind on the building caused by high altitude bombing. Elf 4 before you can do so by Visual observation of the binocular vision system, look down the sensor temporarily failures continue to run Visual odometry, support speed and position detection in a timely manner to avoid unable to control speed and location led to bombing occurs.

In fact, due to the previously said GPS could easily be blocked leading to not enough signal to do observations of the situation often encountered in aerial scenes. As in a wooded Canyon aerial, it is often the case when the aircraft on the ground not receive GPS signals, if flying dozens of meters in height will be received. Take off and landing very dangerous in these critical circumstances, if you want to ensure that aircraft are able to maintain a steady state during the lifting process, the craft must be able to seamlessly convert between GPS and Visual odometry, in order to allow users to safely take off and land. If the user is dropped from a height lower suddenly no GPS, Visual odometry is not filled in a timely manner, out of position and speed have become very difficult to control, is likely to hit in the trees.

Readers may ask, optical flow velocity effect module in these cases is the same. We’ve algorithm for optical flow velocity measurement module has many simplifying assumptions, in particular object to be observed must be in the same plane as the assumption that makes optical flow velocity module in the Woods above the space above, varied terrain, are very bad and cannot meet the needs of outdoor aerial. Although large Visual odometry calculation, but it is more practical and effective than optical flow Velocimetry module programme.

Also worth mentioning is that the second generation flight control of Xinjiang using remote control acceleration directives into aircraft, while the third generation frontier flight control on the Elf 4 into remote control lever into the aircraft’s speed command. In ELF 3, and big Xinjiang of Qian generation aircraft and many no machine products Shang, if you push remote control full Rod forward, aircraft will to a fixed of angle accelerated fly out, until acceleration was air resistance offset, such control does not intuitive, so novice hard operation aircraft; and in ELF 4 Shang, if you push remote control full Rod forward, aircraft will himself adjustment to a fixed of speed Shang, directly control speed is very directly, very easy control. The past, keeping the aircraft flying at a constant speed is the only professional fly can do things now really so ordinary people can reach. This change may seem simple, but provide better operational feel and makes flying more stable.

For aerial operations manual, and all the whistles are hovering well than steady, stable flies this important, because the plane shook so much, will always give users a “I don’t really have a problem of plane did” feel, extremely bad user experience. We went to Tibet, Qinghai and other very beautiful place drive, must hope that a smooth, slowly open, so as to concentrate on beauty; if you open the throttle gently speed up to 200 km race, sitting in the car while being pushed back, turns left and right swing, do people still have the mood to enjoy the scenery on the way?

Remote control rods weight changes also shows Jiang on his intelligent navigation system provides stability of three-dimensional velocity measurement confidence. At present I have not seen other company aircraft control system using the remote control into aircraft velocity command.

5. when I talk about the drone when what I’m talking about

In this article, up to now I have not been “drone” three words. I feel like a qualified vehicle must have safety belts, airbags, rear-view mirror, fire-retardant Interior, dashboard, and more security measures can be called as cars, a qualified rotary-wing aircraft must have inertial measurement unit, GPS, Visual odometry, obstacle avoidance system, pressure meters and ultrasonic sensor of intelligent navigation system known as drones. Rotary-wing aircraft are not toys, hit by a car at high speed may cause serious injury, many don’t even need rotary wing aircraft propellers for high speed can cause serious injury, multi-rotor aircraft sensor must have a strong sense of security and stability.

Back in 2014, flight control group of Xinjiang have a whiteboard, reads: “competitors” following written in small print with several brand names in the industry, but using big letters he wrote “Boeing”. In recent years, Xinjiang dreams of flight control can make cheap cheap multi-rotor aircraft like the Boeing passenger jet, the only fatal accident rate of one out of 10,000. Flight control with sensor technology promotion and improve the quality of, and by the end of May 2016, Elf 4-core sensor failure probability is approximately one out of 10,000. Although than manned aircraft, Xinjiang has lot of effort, but in the unmanned rotary wing aircraft industry, Xinjiang is the enterprise with the lowest failure rate of the aircraft in the industry as a whole. Many other companies, may not calculate the probability of accidents is the number of parts per million, even very much.

Many other company multi-rotor aircraft, but most only had a navigation fur, plus an optical flow velocity measurement module, then move some crooked mind began to boast about its safety. Is like building a car, saying “my safety is very good because I feel the steering wheel very good, also installed a car GPS”, but he did not even air bags and rear-view mirror of the car.

Some companies have new sensors on the aircraft as a selling point. But a complete, reliable sensor system is accumulated bit by bit, new sensors must be and integrated navigation system in hardware and software integration carefully, can play a role. Many known as laser, infrared, “eye-level smart” sensors, readers just ask them: “do you seamless switching sensors and GPS? “” Your sensor indoor high problem solving “” sensors in the brakes when you stay: position detection “, it can be seen that they are piling out of the castle in the air.

Some manufacturer’s slogan is “drones are not local Toys”. If all the promotional language in the “drone” replacing the word “auto”, then such information guided by logic and the concept seems very wrong. For cars, some cars are expensive is because they provided better reverse radar and sensor systems around the car, the increase in car prices enhance the driving experience, is as it should on the other, require cheaper, should not require the removal of the safety sensor, it should start from the body material, Interior to reduce costs.

Xinjiang is extremely offensive to such acts is not to combat these competitors to capture the market, but by ensuring that all manufacturers are able to take it easy, perfect vehicle sensors. Consumer electronics like multi-rotor aircraft is not a phone, but, like automobiles, aircraft carrier with a certain risk, can no longer compete on price or unconventional. We hope that can appear on the market with a full range of intelligent navigation system and algorithm remains at $ 2999 aircraft. We firmly believe that only through a comprehensive navigation system, to make a truly secure UAV products, to allow substandard vehicles enter the market, damage the interests of all manufacturers, also endangering the security of society as a whole.

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