How to isolate interference in industrial servo feedback loops?

Isolation of the servo feedback loop (including encoders, resolvers, etc.) is crucial for blocking power-side noise interference and ensuring control accuracy. Etymotic's isolation solution employs electrical isolation, using isolation devices between the feedback sensor and the controller. For digital encoders, high-speed digital isolators (such as ADuM140x) or optocoupler isolation modules are used, with independent isolated DC-DC power supplies. For analog resolver signals (sin/cos), isolated operational amplifiers or resolver-to-digital converters (RDCs) followed by digital isolation can be used.

A Y capacitor (1nF/Y1) is connected between the isolation grounds to provide a path for high-frequency common-mode noise. Simultaneously, the feedback loop PCB area should be surrounded by an "isolation trench" (>3mm gap), with no copper below the trench. With complete isolation, the feedback loop can withstand power frequency withstand voltage tests up to 2500Vrms and reduce the impact of power switching noise by more than 40dB, significantly improving system stability in noisy environments.