Linear Motor Attraction Force Compensation in Control

Overview of Technical Issues:

The electromagnetic drive structure in the linear motor generates harmful attraction force perpendicular to the motion direction, which loads the guided rail structure causing increased friction, accelerated wear, and reduced positioning accuracy; the goal is to compensate or eliminate this attraction force effect to achieve higher control precision and system efficiency in linear motor applications.

Solution directions generated for this problem

Problem Direction 1 :

ImprovePerpendicular attraction force magnitude
VS
ConstraintDriving force output

Inspiration 1 : Cross-domain reference

Application Principle: #1 Segmentation
Cross-domain applicability Assess applicability
Novel ironing roller structure
Innovative Solution Refine solution

Independently controlled segmented stator with zone-selective activation for perpendicular force minimization

Divide stator into independently controlled segments to minimize cumulative perpendicular force
How to solve :
  • Partition the linear motor stator into modular segments (length 50–100mm each) with independent power electronics, enabling selective activation of only the 3–5 segments directly beneath the mover while deactivating remote sections
  • Implement real-time position feedback (resolution ≤0.1mm) with segment switching logic that activates the next segment 20ms before mover arrival and deactivates trailing segments within 10ms after mover departure, maintaining continuous propulsion while reducing total active stator length by 60–75%
  • Configure each segment with dedicated current control (switching frequency ≥10kHz) to deliver rated driving force (tolerance ±3%) in active zones while inactive segments contribute zero perpendicular attraction, reducing cumulative guide rail loading by 65–80% and friction force proportionally
Expected Effect : Perpendicular force reduced 70%, friction reduced 68%, positioning accuracy improved to ±5μm, energy efficiency increased 22%
Risk Control :
  • segment switching timing synchronization error causing thrust ripple
  • power electronics thermal management in high-density segmented layout
  • position sensor latency affecting activation sequence accuracy

Problem Direction 2 :

ImproveGuide rail friction force
VS
ConstraintDriving force output

Inspiration 1 : Cross-domain reference

Application Principle: #1 Segmentation
Cross-domain applicability Assess applicability
An internal bypass valve type magnetorheological fluid mount
Innovative Solution Refine solution

Independently controlled segmented stator with zone-selective activation for perpendicular force minimization

Divide stator into independently controlled segments with zone-selective activation
How to solve :
  • Partition the linear motor stator into modular segments (length 50–100mm each) with independent power electronics, enabling only 3–5 segments directly under the mover to be energized while deactivating remote sections
  • Implement real-time position feedback control (sampling rate ≥10kHz) to dynamically switch active segments as the mover travels, maintaining localized electromagnetic coupling for full driving force (≥95% of continuous-stator output) while reducing cumulative perpendicular attraction by 60–75%
  • Install segment-level current regulators with phase-synchronized switching (transition time <2ms) to ensure smooth force handoff between adjacent segments, preventing thrust ripple during zone transitions — tolerance ±3% of rated force
Expected Effect : Friction force reduced 65%, driving force maintained ≥95%, positioning accuracy improved to ±5μm, energy efficiency +18%
Risk Control :
  • segment switching synchronization failure causing thrust gaps
  • position sensor latency inducing activation delays
  • power electronics thermal management in high-density segmented layout

Problem Direction 3 :

ImprovePositioning accuracy
VS
ConstraintDriving force output

Inspiration 1 : Cross-domain reference

Application Principle: #28 Mechanics substitution
Cross-domain applicability Assess applicability
Surgical robot platform
Innovative Solution Refine solution

Dual-layer stator with independent precision positioning coils

Separate propulsion and positioning into independent electromagnetic layers
How to solve :
  • Design dual-layer stator structure: outer layer with main driving coils (3-phase, 400A peak) for full propulsion force, inner layer with auxiliary positioning coils (single-phase, 50A) for fine motion control within ±5μm
  • Main coils operate at 50Hz with air gap 1.2mm maintaining 2000N driving force, while positioning coils use 200Hz PWM control at 0.6mm air gap for precision adjustment without affecting propulsion flux path
  • Implement decoupled control algorithm with separate inverters: main controller handles velocity and force, positioning controller uses optical encoder feedback (0.1μm resolution) to correct friction-induced errors in real-time within 2ms response
Expected Effect : Positioning accuracy ±2μm, driving force maintained at 100%, friction compensation efficiency 95%
Risk Control :
  • thermal expansion mismatch between layers
  • electromagnetic crosstalk between coil systems
  • control synchronization latency

Problem Direction 4 :

ImproveSystem energy efficiency
VS
ConstraintDriving force output

Inspiration 1 : Cross-domain reference

Application Principle: #19 Periodic action
Cross-domain applicability Assess applicability
Electric vehicle, and active safety control system for electric vehicle and control method therefor
Innovative Solution Refine solution

Pulsed coil energization with duty cycle optimization for friction loss reduction

Switch from continuous to pulsed electromagnetic field operation to reduce friction losses
How to solve :
  • Implement pulsed coil energization with 60–80% duty cycle during constant-velocity phases, delivering full driving force during 15–25 ms acceleration pulses while reducing perpendicular attraction force to ≤30% nominal during 5–10 ms coast intervals, cutting average friction losses by 40–50%
  • Deploy high-frequency PWM controller (switching frequency 5–10 kHz) with real-time velocity feedback to synchronize pulse timing with motion phases—full field during acceleration/deceleration, reduced field during steady motion—maintaining peak thrust ≥95% of continuous rating
  • Install current shaping circuit using IGBT modules (rated ≥600V, 200A) with di/dt control ≤500 A/μs to generate trapezoidal current waveforms that maximize tangential force component (force angle tolerance ±3°) while minimizing time-averaged perpendicular attraction, verified by Hall-effect force sensors (resolution 0.1 N) at 1 kHz sampling
Expected Effect : Energy efficiency +35–45%, friction loss −40–50%, driving force maintained ≥95%
Risk Control :
  • PWM switching noise and EMI interference
  • current ripple causing torque pulsation
  • thermal cycling stress on coil insulation
Patsnap Eureka Solution