Optimizing Servo System Performance: A Comprehensive Guide to Eliminating Electrical Noise and Enhancing Noise Immunity
Executive Summary
Electrical noise (EMI) is a critical challenge in servo systems, degrading precision, stability, and reliability. This whitepaper provides a systematic approach to mitigating EMI through proven techniques in grounding, shielding, cabling, and component selection, ensuring optimal performance in high-precision applications.
1. Introduction
Servo systems are vulnerable to electromagnetic interference (EMI) from both conducted and radiated noise sources. Noise corrupts feedback signals (e.g., encoders, resolvers), leading to:
- Positional inaccuracies
- Velocity fluctuations
- System instability
This guide outlines 12 actionable steps to enhance noise immunity, supported by engineering best practices.
2. Noise Mitigation Strategies
2.1 Proper Grounding
Goal: Minimize ground loops and impedance disparities.
- Single-Point Grounding: Connect all grounds to a common node.
- Star Grounding: Radial ground wires to a central point.
- Best Practices:
- Use thick, low-impedance wires.
- Keep ground paths short (<30 cm).
- Avoid daisy-chaining grounds.
2.2 Shielding
Goal: Block EMI ingress/egress.
- Cable Types: Foil (high-frequency) vs. braided (durability).
- Shielding Grounding: Terminate shields at one end (controller side) to prevent ground loops.
- Critical Note: Ensure shield continuity across connectors/joints.
2.3 Cable Routing & Selection
Goal: Reduce crosstalk and inductive coupling.
- Separation: Maintain >30 cm between power and signal cables.
- Crossing Angles: 90° crossings minimize coupling.
- Twisted Pairs: Use shielded twisted pair (STP) cables for differential signals.
2.4 Noise Filtering
Goal: Attenuate high-frequency noise.
- Ferrite Beads: Absorb RF noise on cables.
- Common-Mode Chokes: Suppress noise in power lines.
- Low-Pass Filters: Block frequencies above signal bandwidth.
2.5 Power Supply Optimization
Goal: Ensure clean, stable power.
- Regulated PSUs: Select supplies with <1% ripple.
- Capacitor Banks: Smooth voltage transients.
- Isolation Transformers: Decouple servo systems from noisy mains.
2.6 Differential Signaling
Goal: Reject common-mode noise.
- Encoders/Resolvers: Use RS-422 or LVDS interfaces.
- Impedance Matching: Prevent signal reflections.
3. Advanced Considerations
3.1 Environmental Noise
- RFI Mitigation: Shield systems from wireless devices/radar.
- Conductive EMI: Filter power inputs near VFDs/switch-mode supplies.
3.2 System-Level Design
- Component Placement: Separate high-power (drives) and low-power (controllers) sections.
- Enclosures: Use conductive coatings (e.g., nickel) for EMI containment.
3.3 Software Techniques
- Digital Filtering: Implement moving-average or Kalman filters for noisy feedback.
- Adaptive Control: Auto-tune PID loops to compensate for noise-induced latency.
4. Validation & Maintenance
- Testing Tools: Oscilloscopes (time-domain), spectrum analyzers (frequency-domain).
- Routine Checks:
- Inspect cable shields for damage.
- Measure ground impedance (<0.1 Ω recommended).
- Monitor encoder jitter.
5. Conclusion
By integrating multi-layered noise mitigation—from hardware (shielding, grounding) to software (filtering)—engineers can achieve sub-micron precision in servo systems. Electromate’s 35+ years of expertise ensures tailored solutions for the most demanding applications.
About Electromate Inc.
Led by President Warren Osak, Electromate specializes in motion control and automation solutions, offering:
- Technical consulting for EMI challenges.
- Certified components (CE/FCC compliant).
- Custom system integration.
Contact: Electromate Website
Key Takeaways
- Grounding and shielding are foundational to noise control.
- Differential signaling and twisted pairs reject common-mode noise.
- Regular maintenance prevents degradation over time.
