Introduction To The Precision of Robot Joints

Improving Robot Joint Precision: Unveiling the High-Performance Magnetic Encoder Code Disk

At the 2026 CCTV Spring Festival Gala, a robot performance captivated audiences across the nation. The robots not only executed highly difficult somersaults and martial arts stunts with precision but also performed delicate tasks such as spinning walnuts in their palms, picking up grilled sausages, and folding clothes—once again pushing the boundaries of people's understanding of robotic motion capabilities. Their flawlessly synchronized steps and silky-smooth joint movements rely not only on advanced AI algorithms but also on a component hidden within their joints—the magnetic encoder disc.

twirling handkerchiefs. Their flawless dance steps and smooth joint bends rely not only on advanced AI algorithms but also on a precision component hidden deep within their joints: the magnetic encoder code disk.

The "Ruler" Inside the Joint: What is an Encoder?

For a robot to precisely lift an arm or rotate a wrist, it first needs to know the exact position of its joints. This is the core function of an encoder: converting mechanical rotation angles into electrical signals, effectively serving as the "ruler" that allows the control system to perceive the world.

In a robot joint, two types of encoders typically work in tandem: one is a high-speed encoder mounted on the motor shaft for real-time motor torque control; the other is installed at the output end of the reducer to directly measure the final angular output, compensating for errors introduced by mechanical transmission.

Magnetic vs. Optical Encoders: Why Did the Gala Robots Prefer "Magnetic"?

Traditional high-precision applications often use optical encoders. However, in the "metal-intensive" and space-constrained environment of humanoid robots, magnetic encoders demonstrate unique advantages:

1. Contamination Resistance: Optical disks are susceptible to dust and oil; any obstruction can blind them like a human eye. Magnetic encoders, which rely on magnetic field sensing, are insensitive to common elements in robot joints such as grease, dust, and even moisture, offering exceptional reliability.

2. Compact Structure and Off-Axis Design: Humanoid robot joints are increasingly designed with hollow structures for easier cabling. Magnetic encoders support "off-axis" installation, fitting around the shaft like a bracelet, which significantly frees up space.

3. Shock and Vibration Resistance: The impact from a robot landing during a dance can be substantial. Due to their non-contact nature and simple construction, magnetic encoders possess inherent anti-vibration advantages.

Unveiling High Precision: The Technological Breakthroughs Behind ±0.01°

The key to the Gala robots' delicate movements lies in the astonishing precision of their joint encoders. According to the latest industry solutions, achieving extremely high control quality requires encoder accuracy to be controlled within ±0.01° to ±0.02°. What "black technologies" support this?

1. The Vernier Principle: Physical-Level Segmentation

Traditional single-pair magnetic encoders have limited resolution. To improve accuracy within a minimal space, engineers borrowed the principle of the vernier caliper. For example, by magnetizing a ring with 7 pole pairs on the inner track and 8 pole pairs on the outer track, the phase difference between the two magnetic fields can be used to mathematically subdivide the angle down to an extremely high resolution.
This "vernier magnetic ring" technology, utilizing a dual-track magnet design, achieves an accuracy of ±0.015° after calibration without increasing the size.

2. TMR and 3D Hall: A Leap in Sensing Capability

The sensors that detect magnetic fields are also evolving. Traditional Hall effect elements have limited accuracy, whereas next-generation products employ TMR (Tunnel Magneto-Resistance) technology, such as the KTM5900 series from companies like QuinDelta, offering higher sensitivity and signal-to-noise ratio. When combined with 3D Hall sensors (e.g., KTH5701), they can not only sense magnetic field strength but also accurately calculate the three-dimensional direction of the field, thereby algorithmically eliminating errors caused by installation eccentricity.

3. Non-Linear Self-Calibration: The Chip That Corrects Itself

All sensors are subject to errors due to factors like temperature and installation deviations. High-precision magnetic encoder chips integrate an automatic non-linear calibration function. The chip contains a high-speed ADC (Analog-to-Digital Converter) and uses a built-in error Look-Up Table (LUT) to compensate in real-time for imperfections in the magnet and distortions from mechanical assembly. This ultimately keeps the non-linearity error (INL) below ±0.025°, and even as low as ±0.01°.

4. Breaking the "Bottleneck": The Progress of Localization

In the past, high-resolution (e.g., 19-bit, 20-bit and above) magnetic encoder disks were heavily reliant on imports, leading to high costs and long lead times. In recent years, Chinese startups have made significant breakthroughs in this field.
For instance, the precision code disks from SDM, supporting 17/23-bit resolutions and compatible with various industrial and collaborative robots, not only achieve performance on par with international standards but also reduce costs to 1/2 or 2/3 of imported products, strongly supporting the self-reliance and control of the Chinese humanoid robot industry chain.

Future Outlook: Beyond Precision, Towards Perception

As technology advances, the magnetic encoders of the future will provide more than just position data. Smart encoders integrating temperature monitoring and vibration analysis are emerging. They will upload real-time health status via interfaces like IO-Link, enabling predictive maintenance.

From the stunning dance on the Spring Festival Gala stage to precision assembly in factories, the high-performance magnetic encoder code disk is quietly driving the advent of the robotic era. It proves that profound simplicity often lies within these seemingly inconspicuous yet critically important details.