As a core component of high-precision position detection, the magnetic encoder ring's installation eccentricity directly disrupts the uniformity of the magnetic field distribution, leading to periodic distortion of the output signal. This distortion not only manifests as jumps in angle data but also reduces the stability of the control system in high-speed operation scenarios, even triggering equipment protection mechanisms. Specifically, the impact of eccentricity on the signal can be analyzed from five dimensions: changes in magnetic field strength, signal waveform distortion, periodic error distribution, deterioration of dynamic performance, and increased installation compatibility requirements.
When the magnetic encoder ring is installed eccentrically, the relative position between the permanent magnet and the sensor changes periodically with rotation, causing the magnetic field strength detected by the sensor to fluctuate periodically. For example, in a shaft-end configuration, if a radially magnetized magnet is used, eccentricity will cause the magnetic field strength to change sinusoidally during rotation. This change is directly reflected in the output signal of the Hall element or magnetoresistive sensor, manifesting as periodic attenuation or enhancement of the signal amplitude, thus causing angle calculation errors. While using axially magnetized magnets can reduce lateral magnetic leakage, the magnetic field area is smaller, further amplifying the angular error caused by eccentricity, especially in high-speed rotation scenarios where the cumulative effect of the error is more significant.
Eccentricity also disrupts the symmetry of the signal waveform, leading to distortion in the output signal. Ideally, the output signal of a magnetic encoder ring should be a regular sine wave or square wave, but eccentricity causes jitter or spikes at the waveform edges. For example, when a Hall element for detecting longitudinal magnetic field strength is used in an eccentric system, the periodic change in the input magnetic field strength causes the output signal to distort from a square wave to a trapezoidal wave, or even result in signal loss. This distortion directly reduces the signal-to-noise ratio (SNR), making it difficult for the control system to accurately identify position information, especially in low-speed or micro-motion scenarios where the amplification effect of the error is more pronounced.
The error caused by eccentricity has a significant periodic characteristic, with its frequency proportional to the rotational speed. For example, in a motor control system, the eccentricity error is superimposed on the actual position signal in the form of a periodic electrical angle, forming periodic angular jumps. If this error is not compensated for by algorithms, it will lead to increased vibration and decreased efficiency during motor operation, and may even cause mechanical resonance. Furthermore, periodic errors can affect the stability of the closed-loop control system, causing oscillations or loss of synchronization at specific speeds.
In terms of dynamic performance, eccentricity significantly reduces the response speed and resolution of the magnetic encoder ring. As the rotational speed increases, the signal jitter and distortion caused by eccentricity will further intensify, making it difficult for the control system to accurately capture position changes in a short time. For example, in high-speed CNC machine tools or robot joints, eccentricity errors may lead to decreased trajectory tracking accuracy or even trigger equipment protection mechanisms. In addition, eccentricity limits the maximum usable speed of the magnetic encoder ring, making it unsuitable for high-dynamic scenarios.
To address the eccentricity problem, the installation of the magnetic encoder ring requires extremely stringent requirements for coaxiality and parallelism. For example, in shaft-end mounting configurations, the concentricity of the permanent magnet center and the sensor center must be ensured, while controlling the installation gap within a very small range. If a hollow shaft design is used, the impact of the radial clearance between the magnetic ring and the shaft on the magnetic field distribution must also be considered. Furthermore, while introducing eccentricity calibration algorithms can reduce errors through software compensation, it increases system complexity and cost, and cannot completely eliminate fundamental errors caused by hardware installation deviations.
The installation eccentricity of the magnetic encoder ring can have multi-dimensional effects on the output signal through pathways such as changes in magnetic field strength, signal waveform distortion, periodic error distribution, dynamic performance degradation, and increased installation compatibility requirements. To ensure system accuracy and stability, coordinated improvements are needed in both hardware installation accuracy optimization and software algorithm compensation.
