Linear Motor Winding Inductance Asymmetry Detection

Overview of Technical Issues:

The winding structure in the linear motor exhibits insufficient symmetric magnetic field generation due to inductance asymmetry across phases or sections, producing a harmful effect where unbalanced electromagnetic forces act on the mover, resulting in thrust ripple, positioning inaccuracy, and vibration that degrade motion control performance; the goal is to detect and characterize this inductance asymmetry to enable compensation or correction for achieving uniform force transmission and precise linear motion.

Solution directions generated for this problem

Problem Direction 1 :

ImproveInductance asymmetry detection precision
VS
ConstraintMeasurement system complexity

Inspiration 1 : Cross-domain reference

Application Principle: #26 Copying
Cross-domain applicability Assess applicability
Inferential fluid condition sensor and method thereof
Innovative Solution Refine solution

Model-based inductance asymmetry estimation from terminal measurements

Estimate phase inductance distribution using parametric electromagnetic model calibrated by terminal measurements
How to solve :
  • Inject controlled voltage pulses (50–200V, 1–5ms duration) into motor phases at standstill
  • measure terminal voltage and current waveforms using existing 3-channel controller sensors (16-bit ADC, ≥10kSa/s sampling)
  • Feed measured data into pre-calibrated FEA-derived parametric model that maps terminal impedance to spatial inductance distribution — model uses 8–12 coefficients representing dominant spatial harmonics, calibrated once during motor commissioning using 5-position reference measurements
  • Extract phase-to-phase inductance variation and spatial asymmetry pattern via least-squares parameter fitting — algorithm runs on standard industrial controller (ARM Cortex-M7 class), computation time <2s, outputs asymmetry magnitude with 0.5% resolution and spatial profile with 10mm resolution
Expected Effect : Detection resolution 0.5% (vs 3% baseline); zero additional sensors; processing time <2s; setup <5min
Risk Control :
  • Model accuracy degradation with winding temperature variation beyond ±5°C
  • Parameter fitting convergence failure if initial inductance estimate >15% off
  • Pulse injection may trigger motor motion if brake not engaged

Problem Direction 2 :

ImproveInductance asymmetry detection precision
VS
ConstraintDiagnostic operation difficulty

Inspiration 1 : Cross-domain reference

Application Principle: #35 Parameter changes
Cross-domain applicability Assess applicability
Apparatus and method for estimating blood pressure
Innovative Solution Refine solution

Temperature-normalized differential inductance measurement for linear motor asymmetry detection

Perform diagnostics at fixed winding temperature to eliminate thermal drift
How to solve :
  • Stabilize motor windings at 25°C ±1°C using 10-minute passive cooling or active thermal control before measurement—eliminates temperature compensation matrices and reduces calibration from multi-condition to single-point
  • Inject 1 kHz square-wave excitation at 10% rated current into each phase sequentially, measure voltage response with existing current sensors, calculate inductance from V=L(di/dt) slope—reuses control hardware, no additional sensing channels required
  • Automated software computes phase-to-phase inductance ratio and displays single pass/fail result with asymmetry percentage—operator initiates test via single button, receives result in 3 minutes without manual data interpretation or calibration equipment
Expected Effect : Detection resolution <0.8%, setup time reduced from 30min to 3min, zero external calibration equipment
Risk Control :
  • thermal stabilization time variability in different ambient conditions
  • current sensor noise floor limiting resolution at low excitation levels
  • software algorithm sensitivity to motor geometry variations across product batches

Problem Direction 3 :

ImprovePhase inductance uniformity
VS
ConstraintMeasurement system complexity

Inspiration 1 : Cross-domain reference

Application Principle: #26 Copying
Cross-domain applicability Assess applicability
Method and apparatus for selecting an access and mobility management function in a mobile communication system
Innovative Solution Refine solution

Model-based inductance uniformity verification using single-phase spatial measurement

Measure single phase inductance profile then predict other phases via calibrated electromagnetic model
How to solve :
  • Measure phase-A inductance at 15-20 spatial positions along motor travel using existing current sensor and PWM inverter in diagnostic mode, inject 1kHz test signal at 10% rated current
  • Use pre-calibrated electromagnetic FEA model (validated once during motor commissioning with full 3-phase measurement) to compute phase-B and phase-C inductance distributions from phase-A data and geometric symmetry
  • Verify uniformity by checking measured phase-A profile matches model prediction within ±1.5% tolerance—if deviation exceeds threshold, flag asymmetry without requiring full multi-phase hardware
Expected Effect : Measurement channels reduced from 9-12 to 1; uniformity verification time <8min; detection resolution 0.8%; hardware cost -70%
Risk Control :
  • FEA model calibration accuracy dependency
  • temperature drift affecting single-channel measurement
  • geometric asymmetry not captured by symmetric model
Patsnap Eureka Solution