Linear Motor Forcer Design for Minimal Moving Mass

Overview of Technical Issues:

The electromagnetic forcer assembly in the linear motor system suffers from excessive moving mass due to structural support frames, cooling mechanisms, and power transmission cables that, while performing their necessary functions, add significant weight beyond the minimum required for electromagnetic operation. This excessive mass creates a harmful effect by reducing acceleration performance, limiting positioning speed, increasing inertial forces during motion, and elevating power consumption and heat generation. The goal is to minimize the forcer's moving mass while maintaining structural integrity, adequate cooling, and reliable power delivery to achieve optimal dynamic performance.

Solution directions generated for this problem

Problem Direction 1 :

ImproveForcer moving mass
VS
ConstraintStructural strength

Inspiration 1 : Cross-domain reference

Application Principle: #1 Segmentation
Cross-domain applicability Assess applicability
Bearing system for reciprocating pump and method of assembly
Innovative Solution Refine solution

Modular Zone-Differentiated Forcer Frame with Selective Reinforcement

Divide frame into functional zones with mass allocation
How to solve :
  • Partition the forcer support frame into three distinct modules: central coil-mounting zone (40% of length, 70% of mass) using 6061-T6 aluminum with wall thickness 4–6mm to handle peak electromagnetic forces up to 5000N
  • intermediate transition zones (30% of length) using magnesium alloy AZ91D with 2.5mm walls providing 35% density reduction
  • end sections (30% of length) using carbon fiber reinforced polymer panels at 1.2mm thickness for cable routing and sensor mounting where loads remain below 500N
Expected Effect : Total frame mass reduced 42%, stiffness maintained at critical zones ≥8×10⁶ N/m, acceleration improved 38%
Risk Control :
  • interface stress concentration between dissimilar materials
  • tolerance stack-up in multi-segment assembly
  • galvanic corrosion at aluminum-magnesium joints

Problem Direction 2 :

ImproveCooling thermal efficiency per unit mass
VS
ConstraintOperating temperature

Inspiration 1 : Cross-domain reference

Application Principle: #2 Taking out
Cross-domain applicability Assess applicability
Stator winding heat sink configuration
Innovative Solution Refine solution

Stationary coil architecture with moving permanent magnet forcer

Relocate heat source from moving to stationary side
How to solve :
  • Invert motor topology to stationary coils on stator and moving permanent magnets on forcer — eliminates all heat generation from moving assembly
  • Install unlimited cooling mass on fixed stator: aluminum extrusion heat sinks with embedded liquid cooling channels (water flow 2–4 L/min, inlet 20°C) directly bonded to coil windings
  • Mount NdFeB N52 grade magnets (remanence 1.45T) on lightweight carbon fiber forcer frame — magnet assembly mass ≤30% of original coil assembly, zero heat generation during operation
Expected Effect : Forcer mass reduced 65%, coil temp ≤60°C, acceleration +120%
Risk Control :
  • magnetic field uniformity across travel range
  • thermal expansion mismatch between coil and heat sink
  • electromagnetic force ripple during commutation

Problem Direction 3 :

ImproveCable power transmission density
VS
ConstraintOperating temperature

Inspiration 1 : Cross-domain reference

Application Principle: #2 Taking out
Cross-domain applicability Assess applicability
Wireless charging system, apparatus and method
Innovative Solution Refine solution

Stationary coil architecture with moving permanent magnet forcer

Relocate heat source from moving to stationary side
How to solve :
  • Invert motor topology to stationary copper coils on stator and moving NdFeB magnets on forcer — eliminates all power cables and onboard heat generation
  • Install unlimited liquid cooling channels (water flow 2–4 L/min, ΔT=15°C) directly into stationary coil housing, maintaining winding temperature ≤65°C under continuous operation
  • Forcer carries only passive magnet array (N52 grade, 1.45T remanence) with aluminum backing plate (thickness 3mm) — total moving mass reduced by 55–65% versus cable-fed coil design
Expected Effect : Moving mass -60%, coil temp ≤65°C, acceleration +80%
Risk Control :
  • magnet demagnetization risk under shock
  • air gap tolerance ±0.1mm critical
  • magnetic force attraction increases bearing load

Problem Direction 4 :

ImproveStructural stiffness-to-weight ratio
VS
ConstraintMust not deteriorate

Inspiration 1 : Cross-domain reference

Application Principle: #1 Segmentation
Cross-domain applicability Assess applicability
Composite sandwich with high flexural stiffness
Innovative Solution Refine solution

Functionally-graded lattice frame with load-adaptive density zones

Divide frame into load zones with optimized mass
How to solve :
  • Partition forcer frame into three functional zones: central coil-mounting region (high-density lattice, 70% relative density), mid-span transition region (gradient lattice, 40–60% density), and end regions (low-density lattice, 25% density)
  • Manufacture via selective laser melting (SLM) of AlSi10Mg alloy with unit cell size 2–5mm, strut diameter 0.4–1.2mm varying by zone, build layer thickness 30μm, laser power 350W, scan speed 1200mm/s
  • Implement FEA-driven topology optimization to map electromagnetic force distribution (peak 2000N at coil center, <200N at ends) onto lattice density field, ensuring local stiffness ≥5×10⁶ N/m at mounting points while overall frame mass reduces by 55%
Expected Effect : Frame mass -55%, stiffness maintained ≥5×10⁶ N/m, acceleration +40%
Risk Control :
  • SLM build defects in thin struts (porosity >2%)
  • dimensional tolerance deviation ±0.15mm affecting assembly fit
  • fatigue crack initiation at density transition interfaces under cyclic loading
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