1. Definition and principle of planetary gearboxes
A planetary gearbox is a mechanism that reduces the transmission speed ratio and increases the torque of the motor proportionally. Its structure includes multiple planetary gears rotating around a sun gear. This design enables the planetary gearbox to provide efficient deceleration and torque increase effects in a compact space. The working principle of the planetary gearbox is based on the motion characteristics of planetary gears. The planetary gears not only rotate around their own rotation axis (autorotation), but also rotate around the axis of other gears with the planet carrier (revolution). This design enables the planetary gearbox to provide a smooth transmission effect between the high-speed rotating motor and the low-speed rotating load.

2. Control function of planetary gearbox
1. Deceleration function: When the sun gear remains fixed, the pinion rotates around the sun gear, and the output shaft realizes the transmission of the deceleration ratio through the rotation of the pinion. This configuration makes the output shaft rotate at a lower speed than the input shaft.
2. Reversing function: During the reversing process, the sun gear is used as the power input, the ring gear is used as the power output, and the planetary gear carrier remains fixed. This configuration allows the power to be transmitted from the sun gear to the ring gear to achieve the reversing function.
‌3. Direct connection function‌: Power is input from the sun gear and directly transmitted to the planetary gear carrier through the ring gear to achieve direct connection of power. This configuration simplifies the transmission system and improves the efficiency of power transmission‌.
‌4. Acceleration function‌: When the planetary gear carrier is used as the input end, the sun gear is output, and the ring gear remains fixed, the structure becomes a speed-increasing transmission. This configuration makes the output shaft rotate faster than the input shaft‌.

3. Design features of planetary gearboxes
‌1. Efficient transmission‌: The planetary gearbox has a large speed-increasing ratio, strong load-bearing capacity, compact structure and light weight. At the same time, the input and output shafts are collinear, which is very suitable for the needs of wind turbines‌. This design allows the planetary gear to perform both internal meshing transmission and external meshing transmission of the sun gear, and to rotate around its own axis while revolving around the axis with the planetary carrier‌.
‌2. Efficient transmission ratio‌: The transmission ratio range of the planetary gear set can be adjusted according to the different fixed components. For example, when the outer ring gear is fixed, the sun gear and the planet carrier rotate in the same direction, and the transmission ratio is between 3:1 and 12:1; when the planet carrier is fixed, the sun gear and the inner ring gear rotate in opposite directions, and the transmission ratio is between 2:1 and 11:1; when the sun gear is fixed, the planet carrier and the outer ring gear rotate in the same direction, and the transmission ratio is between 1.1:1 and 1.7:1.
‌3. Compact structure: The structural design of the planetary gearbox makes it small in size and light in weight, suitable for use in equipment with limited space. This design not only saves space, but also reduces the overall weight, which is conducive to the portability and installation convenience of the equipment.
‌4. High efficiency: The planetary gearbox has high efficiency, which can reduce energy loss and improve the operating efficiency of the overall system. This high efficiency makes the planetary gearbox perform well in various industrial applications, especially in situations where high-efficiency transmission is required.
‌5. Multi-purpose: The planetary gearbox can achieve functions such as differential, deceleration (speed increase), and reversal by fixing different components, which makes it highly flexible in various application scenarios. For example, in the automotive industry, planetary gear sets are used in power splitting in AT transmissions and hybrid systems.

4. Common application industries of planetary gearboxes
‌1. Machine tool industry‌: Planetary gears are widely used in CNC machine tools and machining centers to transmit high-precision, high-torque power. In the machine tool industry, planetary gears are mainly used to transmit rotational and linear motion, such as spindle transmission and feed transmission. Planetary gears have the advantages of high precision, high transmission efficiency and low noise.
‌2. Robot industry‌: Planetary gears have important applications in robot joint transmission and end effector transmission. The working environment of robots is usually harsh, requiring high-precision, high-reliability and low-noise transmission devices, and planetary gears just meet these requirements.
‌3. Aerospace industry‌: Planetary gears are widely used in key components such as aircraft engines and aircraft landing gears. Its high precision, high torque transmission capacity and low noise can meet the high requirements of the aerospace field for transmission devices.
‌4. Medical device industry‌: Planetary gears are used in various medical devices, such as surgical robots and medical imaging equipment. Its high precision, high reliability and low noise ensure the accuracy and safety of medical devices‌.
‌5. Financial machinery and game consoles‌: Planetary gearboxes are used in conjunction with motors for micro reduction motors, automatic curtains, smart toilets, lifting systems, banknote counters, advertising light boxes and other equipment. These applications cover office automation, smart homes, production automation and other fields‌.
Source:https://blog.udn.com/stepperrelation/182487893