Reducers are core components of robot joints, used to reduce motor speed, increase output torque, and improve motion control precision, making them indispensable, especially in scenarios requiring high precision and high load. In terms of transmission precision, the three types of precision reducers, ranked from highest to lowest, are: precision planetary reducer > harmonic reducer > RV reducer.
Among various types of robots, the precision reducer is one of the important components, mainly serving the following functions:
(1) Improved accuracy: The rotational motion of the motor is converted into the required speed and torque, while significantly reducing errors in motion and improving the robot's operational accuracy;
(2) Increase torque: By using a reducer, the output speed of the motor is reduced while the output torque is increased, enabling the robot to perform heavier load tasks;
(3) Improved response speed: Precision reducers can respond quickly to control signals, enabling rapid start and stop, thus improving the robot's dynamic performance and flexibility;
(4) Improved stability: Precision reducers reduce vibration and impact during motion, thus improving the robot's operational stability;
(5) Reduce size and weight: The precision reducer is compact in design, providing sufficient torque while maintaining a relatively small size and weight, which helps to reduce the overall weight of the robot.
Classification and Principle of Speed Reducers
1. Harmonic reducer
Structure: It consists of a wave generator (elliptical cam), a flexible wheel (thin-walled elastic gear), and a rigid wheel (rigid internal gear).
Principle: The wave generator causes the flexible wheel to undergo elastic deformation and mesh with the rigid wheel. As the wave generator rotates, the meshing position of the flexible wheel teeth and the rigid wheel teeth changes, thereby achieving speed reduction (the transmission ratio is usually 30:1 to 320:1).
Features:
Advantages: compact structure, light weight, high precision (hysteresis ≤1 arcmin), zero backlash.
Disadvantages: Flexible wheels are prone to fatigue, have low torsional stiffness, and may have a reduced lifespan under long-term heavy loads.
Applications: Collaborative robots (such as UR robots), industrial robot wrist joints, medical robots, and other lightweight applications.
Representative manufacturers: Harmonic Drive Systems, Green Harmonic Drive Systems, Rockford Fosgate, Shinpo, Tongchuan, Han's Laser Technology Industry Group
2. RV reducer
Structure: Two-stage reduction, the first stage is a planetary gear, and the second stage is a cycloidal pinwheel.
Principle: After the planetary gears perform initial reduction, the crankshaft drives the cycloidal wheel to mesh with the needle gear, achieving a high reduction ratio (typically 50:1 to 200:1).
Features:
Advantages: High rigidity, large load-bearing capacity, high precision (hysteresis ≤ 1 arcmin), and long service life.
Disadvantages: Complex structure, high cost, and difficult to manufacture.
Applications: Industrial robot bases, boom joints (such as FANUC and ABB heavy-duty robots).
Representative manufacturers: Nabtesco, Huandong Technology, Sumitomo, Zhuhai Pegasus, Zhongda Lide
3. Planetary gear reducer
Structure: Sun gear, planet gears, ring gear, and planet carrier.
Principle: The motor drives the sun gear, the planet gears revolve around the sun gear and mesh with the ring gear, and the power is output by the planet carrier (transmission ratio 3:1 to 100:1).
Features:
Advantages: High transmission efficiency (>95%), uniform load distribution, and compact structure.
Disadvantages: Increased size and slightly lower accuracy at high reduction ratios (hysteresis of about 5-10 arcmin).
Applications: AGV drive wheels, service robot joints, and low-to-medium load industrial scenarios.
Representative manufacturers: Xinbao, Kefeng Intelligent, Newstar Technology, Jingrui Technology, Zhongda Lide
4. Cycloidal pinwheel reducer
Structure: The input shaft eccentric sleeve drives the cycloidal wheel, which meshes with the needle teeth on the needle tooth housing.
Principle: Eccentric motion is converted into the rotational motion of the cycloidal wheel, achieving a high reduction ratio (50:1 to 200:1).
Features:
Advantages: High rigidity, strong impact resistance, and long service life.
Disadvantages: High manufacturing precision requirements and high cost.
Application: Partially replaces RV reducers, suitable for heavy-duty industrial robots.
Selection Recommendations
High precision, lightweight: harmonic reducers (e.g., for collaborative robots).
Heavy load, high rigidity: RV reducer (e.g., industrial robot base).
Cost-effective, medium load: planetary reducer (e.g., AGV drive).
Impact resistant and long lifespan: cycloidal pinwheel reducer.
Future Trends
Integration: Integrated design with the motor (such as electromechanical modules).
New material: Carbon fiber flexible wheel extends the life of harmonic reducer.
High-precision machining: Increase the localization rate of RV reducers (such as Nantong Zhenkang).
