Linear Motor Forcer Mass Reduction for Acceleration

Overview of Technical Issues:

The forcer assembly's excessive mass creates a harmful effect by adding inertia that resists acceleration, resulting in an insufficient force-to-mass ratio that directly limits achievable acceleration performance and reduces system responsiveness; the goal is to reduce forcer mass while maintaining electromagnetic force generation capability to enable higher acceleration rates.

Solution directions generated for this problem

Problem Direction 1 :

ImproveForcer assembly mass
VS
ConstraintElectromagnetic force generation capability

Inspiration 1 : Cross-domain reference

Application Principle: #35 Parameter changes
Cross-domain applicability Assess applicability
Distributed propulsion system
Innovative Solution Refine solution

Liquid-cooled high-current-density coil system for enhanced force-to-mass ratio

Integrate forced liquid cooling to boost current density without mass penalty
How to solve :
  • Design hollow copper conductors (wall thickness 0.6–0.8mm) with internal coolant channels — circulate deionized water or dielectric oil at 2–4 L/min flow rate to remove resistive heat
  • Increase coil current density from 5 A/mm² to 8–10 A/mm² under continuous operation — achieve 60–100% force boost while cooling system adds only 8–12% mass (pump, tubing, heat exchanger)
  • Implement real-time thermal monitoring with embedded thermocouples (±0.5°C accuracy) at hotspot locations — limit coil temperature to ≤85°C, use PID-controlled variable-speed pump to maintain thermal equilibrium within ±3°C
Expected Effect : Force output +60–100%, net force-to-mass ratio +45–80%, acceleration response improved by 40–70% vs air-cooled baseline
Risk Control :
  • coolant leakage causing electrical short
  • flow distribution non-uniformity creating hotspots
  • pump reliability under vibration

Problem Direction 2 :

ImproveForcer assembly mass
VS
ConstraintManufacturing precision requirement

Inspiration 1 : Cross-domain reference

Application Principle: #1 Segmentation
Cross-domain applicability Assess applicability
Fluid delivery systems and methods
Innovative Solution Refine solution

Segmented thin-wall forcer frame with self-jigging stack assembly

Modularize the light frame
How to solve :
  • Split the forcer support into 8–12 stamped laminations with tabs, each 0.8–1.2mm thick, then stack-bond to form a hollow frame
  • Use self-jigging features with pilot holes, tongue-groove edges, and dowel pins, then cure epoxy at 120–150°C and finish only datum faces by one-pass grinding
  • Wind coils on separate bobbin modules and clip them onto the frame, using 5052 Al or GF-PA66 bobbins, concentricity ≤0.02mm, air-gap tolerance ±0.03mm by CMM and go/no-go gauges
Expected Effect : moving mass −25 to −35%, stiffness/weight +20%, force loss <3%, acceleration +18 to +28%, scrap rate <2%
Risk Control :
  • bondline voids or delamination
  • stack alignment drift
  • coil module fit or thermal creep

Problem Direction 3 :

ImproveForce-to-mass ratio
VS
ConstraintElectromagnetic force generation capability

Inspiration 1 : Cross-domain reference

Application Principle: #35 Parameter changes
Cross-domain applicability Assess applicability
Electric motor with flux barriers
Innovative Solution Refine solution

Forced liquid cooling with high-current-density coils for enhanced force-to-mass ratio

Boost electromagnetic force via elevated current density while maintaining coil mass
How to solve :
  • Replace solid copper conductors with hollow copper tubes (OD 3.5mm, ID 1.8mm) for coil windings, circulating deionized water or dielectric oil at 2–4 L/min through internal channels to extract resistive heat directly from current-carrying conductors
  • Increase coil current density from baseline 6 A/mm² to 9–10 A/mm² (50–67% boost) enabled by continuous liquid cooling, proportionally raising electromagnetic force output without adding coil turns or magnet mass — cooling system (pump, heat exchanger, tubing) adds only 8–12% to total forcer mass
  • Implement real-time thermal monitoring with embedded thermocouples (tolerance ±1°C) at coil hot spots, coupled with closed-loop flow control maintaining conductor temperature ≤85°C under continuous operation and ≤110°C during 100ms peak pulses — acceptance criteria: temperature uniformity within ±5°C across winding layers, verified via infrared imaging during commissioning
Expected Effect : Force-to-mass ratio +38–42%, acceleration response +35%
Risk Control :
  • hollow conductor wall thickness uniformity (±0.15mm tolerance required)
  • coolant leakage at coil terminations under vibration
  • thermal expansion mismatch between copper and potting compound

Problem Direction 4 :

ImproveForcer assembly mass
VS
ConstraintMust not deteriorate

Inspiration 1 : Cross-domain reference

Application Principle: #1 Segmentation
Cross-domain applicability Assess applicability
Positioning system
Innovative Solution Refine solution

Cable-driven stationary magnet forcer with moving coil architecture

Relocate heavy magnets to stationary track
How to solve :
  • Transfer all permanent magnets (typically 40–50% of forcer mass) to the stationary track structure, retaining only lightweight copper coils on the moving forcer that interact with track-mounted magnetic field
  • Use flexible cable constraint system (similar to patent EP3145670B1 cable positioning) to supply current and provide mechanical guidance — cables carry 20–40A current while constraining 4 DOF, eliminating heavy linear bearings (15–20% mass reduction)
  • Design forcer as hollow carbon fiber shell (wall thickness 1.5–2mm) housing coil windings, with cable attachment points at four corners — total moving mass reduced to coils + structure only, achieving 60–65% mass reduction versus conventional magnet-on-forcer design
Expected Effect : Moving mass -60%, acceleration +150%, force maintained
Risk Control :
  • cable fatigue under cyclic flexing
  • current-induced cable heating
  • positioning accuracy with cable compliance
Patsnap Eureka Solution