A magnetic encoder is a sensor that uses changes in a magnetic field to measure rotational angle, direction, and speed. In simple terms, it acts as the robot's "proprioceptor" — when the robot's "brain" issues a command like "raise the left arm by 30 degrees," the magnetic encoder works like a "protractor" attached to the joint, feeding back in real time the actual angle reached. Once a deviation is detected, the system immediately corrects it.
Compared with traditional optical encoders, magnetic encoders feature strong anti-interference capability, excellent environmental adaptability, and flexible structure, making them particularly suitable for industrial and complex environments with dust, oil, and vibration. In the robotics field, magnetic encoders are evolving from conventional supporting components into key sensing devices within intelligent motion control systems.
Which Joints Does a Robot Magnetic Encoder Sensor Apply To?
Magnetic encoders are used in almost all joints that require motion feedback in robots.
In terms of joint types, core joints such as the knee, shoulder, and waist of humanoid robots all need encoders. A typical humanoid robot with 14+ joints requires 20–30 encoders. More strikingly, industry data shows that a single humanoid robot requires an average of about 71 magnetic encoders. These encoders are usually deployed at both the motor end and the reducer end, working together to improve speed and position accuracy.
Apart from humanoid robots, magnetic encoders are also widely used in robot dogs and other scenarios that demand fast response and have limited space. In a quadruped robot, each leg is typically equipped with 3 rotational joints (controlling hip, thigh, and calf movement), so one quadruped robot uses a total of 12 encoders to ensure precise motion control.
In addition, compact encoders can be installed in narrow spaces like the robot's wrist, fingers, and neck without compromising performance.
How Effective Are They? What Level of Accuracy Can They Achieve?
The performance of magnetic encoders in robot joints can be summed up in one word: precise.
Currently, mainstream magnetic encoders have reached considerably high accuracy levels. For example, magnetic encoders using AMR (anisotropic magnetoresistance) technology can achieve angular measurement accuracy up to ±0.07°; some high-end products even reach 0.05° absolute angle accuracy. In terms of resolution, advanced magnetic encoders can provide up to 18-bit resolution over a 360° range, allowing robots to perform tasks with greater consistency and repeatability.
In practical applications, a test report from a collaborative robot manufacturer showed that after adopting high-performance magnetic encoders, joint repeatability positioning accuracy improved from ±0.1 mm to ±0.03 mm. Every joint of the Yaskawa MOTOMAN robot is equipped with built-in high-precision magnetic encoders, achieving ±0.01 mm repeatability positioning accuracy.
Magnetic encoders also support multi-turn absolute encoding technology, which retains position information even after power loss, eliminating the need for re-homing as required by incremental encoders.
Are They Vibration-Resistant?
Extremely vibration-resistant. This is one of the key advantages of magnetic encoders over optical encoders.
Because they operate on a non-contact measurement principle, magnetic encoders avoid mechanical wear and have a theoretical service life exceeding 100,000 hours. In terms of vibration resistance, test data is compelling: under continuous vibration (5–2000 Hz), the position output fluctuation of high-quality magnetic encoders is less than 0.1°, far superior to the typical 3°–5° values of conventional encoders.
In addition, magnetic encoders also offer IP67 protection ratings, ensuring stable operation in harsh environments with dust and oil contamination. AMR-technology magnetic encoders are insensitive to magnetic field strength variations under saturated operating mode, featuring excellent anti-vibration and anti-temperature-drift performance. Some products cover an operating temperature range from -40°C to +125°C, meeting industrial-grade application requirements.
In short, under severe conditions such as high-frequency start-stop, forward-reverse rotation, and continuous vibration in industrial robots, magnetic encoders still deliver stable and accurate position signals.
SDM’s Robot Magnetic Encoder Sensors
In the magnetic encoder supply chain, the quality of magnetic materials directly determines the final performance of the sensor. SDM Magnetics Co., Ltd. is a leader in this field.
Founded in 2009, with its headquarters in Xiaoshan, Hangzhou, and its factory in Tonglu, Hangzhou, SDM is a national-level high-tech enterprise specializing in rare-earth permanent magnets and magnetic component systems. For over a decade, the company has been dedicated to the R&D and production of magnetic materials, providing one-stop solutions worldwide for industries such as automotive, consumer electronics, home appliances, green energy, medical, telecommunications, and aerospace.
In the field of robot magnetic encoder sensors, SDM’s core competitiveness lies in a complete precision manufacturing chain:
First, integrated injection molding. SDM’s encoder magnets are produced using injection-molded ferrite technology, which mixes ferrite powder with high-performance resins (e.g., nylon, PP, PPS) and shapes them via injection molding. This process endows the magnets with both the processability of plastics and the magnetic properties of ferrites. Moreover, they can be integrally molded with metal shafts or plastic structural parts, greatly enhancing structural strength and integration. Injection-molded magnets are well-suited for multipole magnetization — a dozen or two dozen poles are common, and more sophisticated versions can be magnetized with up to a hundred poles.
Second, magnetic-printing point magnetization. The key to encoder magnets lies in magnetic pole accuracy — resolution is directly affected by the pole pitch/width. SDM employs specially developed high-precision magnetization processes and equipment to achieve narrow-pitch, high-accuracy magnetization, ensuring excellent signal quality. This "magnetic-printing" style point-magnetization technology precisely controls the position and intensity of each magnetic pole, laying a solid foundation for subsequent sensing accuracy. The company also supports multi-track magnetization and customization of different narrow pole pitches, meeting various requirements from single-track incremental to multi-track absolute encoders.
Third, 100% full inspection of magnetic field waveform patterns. After magnetization, SDM performs strict full inspection of the magnetic field waveform for every single product. This is because even if dimensional designs are correct, insufficient magnetization accuracy can still lead to unstable signal output, reduced resolution, or sensor calibration difficulties. Through full inspection, SDM ensures that the magnetic field waveform of every encoder magnet meets design standards, guaranteeing consistency, reliability, and accuracy from the source.
From integrated injection molding, to magnetic-printing point magnetization, to full inspection of magnetic field waveforms — SDM leverages this complete precision manufacturing chain to provide high-consistency, high-reliability magnetic core components for robot magnetic encoder sensors, helping to drive higher-precision motion control in China’s robotics industry.
