Extension of the Micro-Class Notes, Issue Five | About Plant Protection Machines
On July 25th, the Extension of the Micro-Classroom welcomed Mr. Guo Ning, the Sales Manager of Shanghai Topo Robot Co., Ltd., to share his insights on plant protection machines. The content shared that day has been compiled into these class notes by the Agricultural Small Series to facilitate future reviews and learning. Don't forget to bookmark this article for future reference!
Background of Plant Protection Drones
Drones were initially known as models or aircraft. With the growing market demand, more and more enthusiasts and civil aviation practitioners got involved, laying the groundwork for the drone industry. The influx of investment has accelerated the growth of the drone market, leading to the emergence of companies with varying levels of expertise. Segments within the market include entertainment aerial photography, photogrammetry, and plant protection drones. Drones come in multiple configurations like single-rotor, multi-rotor, fixed-wing, and vertical takeoff and landing fixed-wing.
Today, we're discussing the plant protection drone, which was initially used for agricultural spraying operations. It is essentially a manned plant protection aircraft with large drug capacity and high operational efficiency, but it's not suitable for small plots. With the maturity of Yamaha's single-rotor plant protection drone technology and its introduction to China, many domestic manufacturers have developed their own plant protection drones based on this technology. The earliest domestic plant protection drones were primarily single-rotor. However, with the entry of multi-rotor MK flight controls into the country, multi-rotor drones have gradually gained popularity. Especially after DJI's emergence in the multi-rotor market, the development of multi-rotor drones has accelerated, and multi-rotor plant protection drones have also flourished.
Components of Plant Protection Drones
Next, we'll discuss the components of the plant protection drone. We've always emphasized that the plant protection machine is not a simple assembly, but rather a reasonable mix of the system. The proper and effective combination of various parts can enhance flight and spraying performance. A plant protection drone consists of four parts: structural part (frame), power part (motor, ESC, battery, and propellers), control part (flight control, remote control, and ground station control), and the spraying part (water pump, nozzle, etc.).
Structural Part - Plant Protection Machine Frame
The general frame structure design should take into account the elements of easy transportation, maintenance, durability, and cost-effectiveness. Based on these design factors, different manufacturers have different concepts, leading to diverse product designs. Currently, we often see quadcopters, hexacopters, and octocopters. Some frames are non-folding, while others can fold vertically or horizontally. Depending on the wheelbase, different power packs can be used to achieve different payloads. The most common payload is 10 kg, with four or six rotors.
Firstly, the non-folding frame has the advantage of high structural strength and rigidity, but the downside is that it's not easy to transport. Secondly, the vertical folding frame is easy to carry and minimizes the connection structure. However, if the central plate isn't designed well, especially when using straight blades, the adjacent blades will collide when folded down. Using folding blades can avoid this problem. Lastly, the horizontal folding frame has a partial folding part compared to the vertical folding frame, making it easier to fold and unfold, which is why the horizontal folding frame is popular.
Precautions for Assembling the Plant Protection Machine Frame
Firstly, for parts that aren't frequently disassembled, screws should be glued in place as much as possible.
Secondly, it's crucial to ensure that all motor mounting surfaces are at the same height and maintained in the same horizontal plane.
Many people often ask how to ensure the motor is at the same height if the folding parts have a certain angle. This is indeed a tough question to answer. In theory, if each arm's length is the same and the angle of each folding member is the same, then the mounting plane of the motor and each arm generates the same angle. However, in practice, the processing precision of the folded parts varies, leading to different upper and lower angles. Additionally, each arm is different, resulting in a large cumulative error. Ultimately, our plant protection machine struggles to fly, and the temperatures of each motor vary. Individuals tend to be simplistic and less connected, improving stability.
Thirdly, ensure that the center of gravity of the plant is at its geometric center after assembly. Otherwise, the imbalance in the center of gravity will cause inconsistent motor outputs, reducing the lifespan of the entire aircraft and increasing the failure rate.
Power Section
Stable power output is the greatest guarantee for flight safety. When selecting power, many people encounter problems. What kind of motor, propeller, ESC, and battery size should be chosen, especially for beginners. Many manufacturers offer power packages, such as K3000, K5000, 8-Series power kits, and 6-Series power kits. Whether we choose a power mix or a manufacturer's power package, the principle is that the power must have sufficient redundancy when fully loaded. Typically, during full-throttle takeoff, the aircraft's throttle output must be below 70%, or there won't be enough redundancy to maneuver. This is also why we often see the same frame with different power setups, resulting in varying flight performances.
Secondly, for power, it's not enough to ensure sufficient power; the dynamic balance of the motor and propeller is better. Otherwise, during high-intensity operation of the plant protection machine, the vibration of the motor and aircraft may increase, leading to more instability issues. This is what many people often complain about: my plane flew very well initially, but with use, it became less stable, with the first few flights flying well, but subsequent flights showing significant differences.
Finally, when installing the blades, expand the frame to observe the pitch of the blades. Generally speaking, the pitch of the blades should be less than 0.2 times the blade diameter. The force of the blades will be greatly reduced due to the vortex interference at the blade tips, and on the other hand, the vibration of the blades will increase. As a result, the vibration of the aircraft increases. The final outcome is that the aircraft appears unstable, and the battery consumption is fast.
Control Section
The control part is divided into two major sections: the flight controller that controls the aircraft and the command control part, including the remote control and ground station control. Next, we'll focus on the flight controller.
Flight control is also known as the brain of the drone, which is the core of our technology. We can say that a multi-rotor aircraft cannot fly without flight control. Stable flight or hovering of a multi-rotor is achieved by controlling the speed of the motor to achieve a balance between torque, lift, and drag. Some people might say there's another way to control multi-rotor flight by using the torque of the blades to achieve different tensions, ensuring the aircraft's hovering or stable flight.
Through its high-precision sensors, the flight control senses the attitude changes of the aircraft and then controls the acceleration and deceleration of different motors to stabilize the flight attitude of the aircraft. The general flight control achieves stable control of the aircraft through two-stage PID control. It typically consists of a magnetic compass, GPS, accelerometer, gyroscope, barometer, and more.
The so-called magnetic compass determines the direction of the aircraft. By sensing the state of the accelerometer, GPS is also used to measure speed, and the ultimate flight speed of the aircraft is a fused data. On the other hand, the gyroscope perceives the attitude of the aircraft. For example, how many degrees the roll direction shifts, how much the pitch direction shifts, and how much the heading turns are calculated by the gyroscope data. Knowing these data allows for stable control of the aircraft's flight attitude. The barometer calculates the altitude of the aircraft by sensing changes in air pressure. For attacks, GPS also participates in fixed-height calculations. Of course, every flight control has its own characteristics, and the control methods differ. It's precisely because these manufacturers have different flight mathematical models, i.e., the algorithms are different, and the adaptability differs.
Spraying Part
Next, let's talk about the spraying part. Generally, the pumps we see are both brushed and brushless. The nozzles are further divided into pressure nozzles and centrifugal nozzles. Pressure nozzles have a general plastic fan nozzle and a pressure cone nozzle. Centrifugal nozzles come in quick-release and non-quick-release varieties. The advantage of the brushed water pump is that the cost is lower, but compared to the brushless water pump of the same power, the weight is heavier and the life is shorter; in terms of nozzles, pressure nozzles are prone to clogging when applying powder or emulsions, whereas the advantage of centrifugal nozzles is that they are less likely to clog, but they are more expensive compared to pressure nozzles, and their wind resistance is worse.
We often encounter situations where the liquid rolls up when the plane is flying forward. Especially when the relative height of the nozzle and the motor is not ideal, the rolling will be more noticeable. This is because the eddy current disorder under the propeller causes the direction of the liquid to be unstable. To avoid these problems, the easiest way is to test the spraying of the liquid when the nozzle is different from the motor, and continuously adjust the relative height to achieve the best results.
Precautions for Assembling the Plant Protection Machine
We often see different flight effects on the same aircraft using different flight controls; some are suitable for Dajiang, while others are suitable for extensions. But these are only surface phenomena, and the reasons are very complex. So how do we solve these problems? What do we need to pay attention to during the assembly and assembly process? We know that many flight control systems now have internal shock absorption. Like DJI, T-A plant protection flight control has its internal damping. It involves its natural frequency, especially because of aircraft vibration and flight control. The frequency is similar or multiplier, and the half-frequency relationship causes the vibration to increase, i.e., resonance phenomenon causes poor flight effects.
On the other hand, the output frequency of the flight control is inconsistent with the control frequency of the ESC, causing these problems. There is also a mathematical model of power inconsistency. Some blades do not cause problems on a single plane. For example, when the heading of the remote controller is centered, the motor output of the positive and negative poles is too different. When a certain threshold is reached, it is still not guaranteed that the aircraft can hover stably. Then the flight control defaults to the aircraft cannot hover, causing the aircraft's spin problem. This threshold is somewhat set by the flight controllers, and some manufacturers are relatively small. It will also happen that we often say that flying with other flight controls is very good, but you can't fly with yours.
These problems are hidden in the flight control algorithm, so the phenomenon is consistent, but the reasons are very different. Therefore, as a plant protection company, our professional quality should also be improved. We have been saying that the plant protection machine is not a simple patchwork, but a systematic project. For example, some large manufacturers use the same flight control as you, but the flight effect is much better. Many people copy their shapes, but the reason for doing so is not understood. We often say that we must know more about it, otherwise we will have problems. We don’t even know where the problem is. It’s hard to solve it. In the end, it may be said that the flight control is not good and the ESC is not good. There are problems with the rack.
It's very likely that we have our own problems. When we assemble, we don’t pay attention to it. The power is not well matched. The installation of the flight control is not good. Strong electricity interferes with weak electricity. So how do we solve these problems? What do we need to pay attention to during the assembly process?
For the plant protection machine, deformation of the frame will inevitably occur during flight. When deforming, the deformation of the material, the direction of deformation, etc., are all calculated when we design the aircraft. Generally speaking, a good airplane is calculated, not pieced together. A good match is achieved by the combination of load and load, frame structure, material, and connector. When choosing a frame, we try to choose as few connectors as possible, carry it portable, and fold it. Of course, cost is also one of the considerations. After the power is matched, the disturbance of the tip vortex has a great influence on the flight stability of the aircraft. The high-intensity operation of the plant protection machine and the high-temperature and high-humidity environment also make the requirements for each component of the plant protection machine higher.
Especially now, we are more concerned about the durability of flight control, ESC, and motor, but we do not know that the durability and stability of the aircraft structure is very important, often we ignore a lot of these aspects. The frame does not cause irreparable deformation for a long time in continuous flight, which is often the basis for determining the durability of our aircraft structure. On the other hand, the dynamic balance of power is also very important. In the case of high-intensity operation, the dynamic balance is not good, which will lead to problems such as motor tuning and stalling. On the other hand, the force effect is also something we need to consider. Generally speaking, Motors with small KV values ​​will work better with large-sized propellers, but the corresponding maneuvering wind resistance is also worse, so we must consider the maneuverability and wind resistance while considering the force effect.
Of course, there are still many people who don’t know how to choose when they choose the plant protection flight control accessories. Firstly, we need to know what kind of flight effect we want to achieve. Secondly, we need to know what the function and function of each component is, for example, the height is high. Radar, he can not only realize the imitation flight, but also improve the height setting effect. The digital transmission can not only see the data but also realize the self-planning route through the ground station. The role of RTK is not only to improve the positioning accuracy of the level, but also to improve our Height setting effect. For example, if you want to be able to fly with high precision and full autonomy, you must choose accessories such as RTK, digital transmission, and radar. When assembling the plant protection machine, we are more concerned with the compatibility and matching between the components. Only by choosing a reasonable combination can we achieve good results.
Black Technology of the Plant Protection Machine
Currently, the development direction of plant protection machines is towards intelligence and automation. Many people will also say that the intelligentization of plant protection will only make the employees less important, and the operation process is too intelligent. These people are just porters. However, some people say that plant protection manufacturers are growing wildly, but the gap in the market lies in flying hands. The shortage of flying hands has caused a large number of plant protection aircraft to idle. The shortage of flying hands is also because the operation of the aircraft is still very complicated. It takes at least one month for a person who has never been in contact to learn from being able to work independently. This has led more and more manufacturers to develop aircraft in the direction of intelligence.
Simple operation, simple requirements for flying hands, so that a large number of flying hands can be quickly filled. However, the intelligence also makes the requirements for aircraft sensors higher, the higher the requirements of intelligence, the requirements for flight control, the power requirements will be higher, and the self-checking function of the aircraft should be improved accordingly. Ability to avoid obstacles, automatic dispensing, filling, active obstacle avoidance, aircraft motor temperature, number of revolutions to be able to monitor in real time, etc.; it can also make the flight control more scalable, the aircraft more intelligent will also make The requirements of flying hands are getting lower and lower. There are still many people who are implementing self-service landing and landing platforms, realizing automatic battery replacement, automatic dosing and other operations. The addition of these technologies will make the drones take off their wings and use cutting-edge technology to drive the growth of agriculture.
The above is all about the plant protection machine. If you have any problems in the process of using the extension flight control and the experience in the actual operation process, you can share it with us and help us further optimize the product to provide you with better and more practical products.
Question Time
1. Why does a spinning phenomenon occur after changing the flight control when the plane takes off?
Teacher Guo: If there is a problem with take-off self-selection, you can check it from three points:
First, does the remote control calibrate the median?
Second, whether the motor is installed in balance
Third, whether the magnetic compass is calibrated
2. The LED indicator light of the flight control extension sometimes appears red light, and sometimes the blue light is long, but not bright.
Teacher Guo: If you encounter this problem during flight, it is recommended to send the LED indicator to the after-sales test to find out the specific cause of the problem.
3. What is the reason for a lack of motor power output?
Teacher Guo: This problem will occur in three situations. First, whether the ESC has been calibrated at the same time. Second, whether the flight control output has a problem. Third, the flight control and ESC connection lines pass through the distribution board, causing a large signal resistance, resulting in signal attenuation, which can also cause the above problems, which can be eliminated by the exclusion method.
4. Why is the effect of the expansion of the flight control with the expansion of the power package flight better than other power sets? Will the P80's power kit match the difference?
Teacher Guo: The effect of the expansion and control of the flight control with the extension of the power package will be better because the program of the ESC has been modified, and the matching of the flight control is better. At the same time, the motor, the ESC and the blade have also been matched. The P80's power package effect is also good, we also have customers in use, the P80 blade and motor dynamic balance effect is better, so the body vibration will be greatly reduced, at the same time, force, response, reaction speed is also better It is also good to match the expansion and control flight control.
Warm Little Stickers
In the coming year, the Extension of the Micro-Classroom will launch online courses from time to time. We will invite relevant experts such as pesticides and agricultural machinery to station in the Micro-Classroom. I hope everyone will pay more attention to it. Regarding the plant protection power system, if you have any questions, or if you want to know more about other aspects of the drone, you can pay attention to the official message of the “Top-Up Agriculture†subscription.
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