Linear Motor Halbach Array Design for Force Density

Overview of Technical Issues:

The magnetic field generating structure (Halbach array) provides insufficient flux concentration in the working air gap, resulting in lower electromagnetic force output relative to motor volume and mass; the goal is to optimize the array configuration to maximize force density and achieve compact, high-thrust linear motor performance.

Solution directions generated for this problem

Problem Direction 1 :

ImproveFlux concentration efficiency
VS
ConstraintMotor mass

Inspiration 1 : Cross-domain reference

Application Principle: #5 Merging (Combining)
Cross-domain applicability Assess applicability
Autoclave tolerant battery powered motorized surgical hand piece tool
Innovative Solution Refine solution

Integrated flux-structural Halbach array with load-bearing magnet assembly

Merge flux and structure functions in magnets
How to solve :
  • Design Halbach array segments as primary structural members carrying motor loads, eliminating separate aluminum housing (mass reduction 18–22%)
  • each magnet segment features interlocking dovetail joints (tolerance ±0.05mm) transferring shear forces directly, with epoxy-bonded carbon fiber skins (0.6mm thickness) providing tensile reinforcement
  • use N48 grade NdFeB with compressive strength ≥800 MPa, enabling direct bolt mounting through magnet body to end plates
Expected Effect : Motor mass −20%, air gap flux density maintained ≥1.1T, thrust-to-weight ratio +25%
Risk Control :
  • magnet mechanical failure under shock loads
  • joint precision affecting flux path continuity
  • thermal expansion mismatch between magnets and reinforcement

Problem Direction 2 :

ImproveFlux concentration efficiency
VS
ConstraintManufacturing complexity

Inspiration 1 : Cross-domain reference

Application Principle: #1 Segmentation
Cross-domain applicability Assess applicability
Package structure and fabrication methods
Innovative Solution Refine solution

Modular self-aligning Halbach array with integrated flux-structural segments

Integrate flux and structure in modular segments
How to solve :
  • Design 8-12 standardized Halbach modules where each segment serves dual function as flux generator and structural frame member, eliminating separate housing components
  • Embed magnetic self-alignment features into each module's geometry — trapezoidal interlocking edges with ±1° angular tolerance achieved via magnetic attraction forces during assembly, removing precision fixturing needs
  • Implement two-tier magnet strategy — inner row uses N52 sintered NdFeB trapezoids (15mm thickness) for critical flux concentration, outer rows use injection-molded bonded NdFeB rectangles (10mm thickness, 30% lower density) for secondary flux contribution, simplifying 70% of machining operations
Expected Effect : Air gap flux density +18-22%; assembly time -60%; tooling cost -50%
Risk Control :
  • Module interface magnetic force variation
  • bonded magnet flux degradation over thermal cycles
  • alignment feature wear after repeated assembly

Problem Direction 3 :

ImproveElectromagnetic force density
VS
ConstraintMotor mass

Inspiration 1 : Cross-domain reference

Application Principle: #2 Taking out (Extraction)
Cross-domain applicability Assess applicability
An unmanned aerial vehicle and a system for controlling an unmanned aerial vehicle
Innovative Solution Refine solution

Selective back-iron removal with flux-return optimization for force density enhancement

Remove non-flux-saturated back-iron mass while maintaining flux return capacity
How to solve :
  • Conduct FEA flux saturation mapping of existing back-iron under peak operating current (measure flux density distribution at 0.5mm grid resolution)
  • identify regions below 1.6T saturation threshold and remove 50–65% of back-iron mass in these zones while retaining 6–8mm thickness in saturated flux return paths
  • Replace removed back-iron sections with carbon fiber composite structural ribs (density 1.6 g/cm³ vs steel 7.8 g/cm³) positioned at 30mm intervals to maintain mechanical rigidity, achieving 40% total back-iron mass reduction without compromising flux return capacity
  • Implement topology-optimized back-iron geometry using generative design algorithms constrained by magnetic permeability ≥1000 μr and yield strength ≥350 MPa, creating variable-thickness back-iron (4–12mm) that follows actual flux density contours, eliminating uniform-thickness over-design
Expected Effect : Force density +35–42%, motor mass -28%, thrust-to-weight ratio +58%
Risk Control :
  • flux leakage at thinned sections exceeding 8%
  • composite rib bonding strength below 25 MPa
  • back-iron dimensional tolerance beyond ±0.15mm causing air gap variation

Problem Direction 4 :

ImproveAir gap magnetic flux density
VS
ConstraintManufacturing complexity

Inspiration 1 : Cross-domain reference

Application Principle: #1 Segmentation
Cross-domain applicability Assess applicability
User terminal device for displaying application and methods thereof
Innovative Solution Refine solution

Modular self-aligning Halbach array with factory-calibrated flux segments

Divide array into factory-tested modules
How to solve :
  • Divide the Halbach array into 8-12 standardized modules, each pre-assembled and flux-calibrated at factory to ±2% tolerance using Hall probe mapping at 25±2°C
  • modules feature interlocking dovetail joints with self-centering geometry allowing ±0.15mm positional tolerance instead of ±0.02mm for monolithic arrays
  • Magnetic keying features molded into each segment provide automatic angular alignment within ±0.8° through repulsive force guidance during assembly, eliminating precision fixtures
  • Each module undergoes individual flux density verification (target: 0.85-0.95T at air gap surface) before shipment, with QR-coded traceability linking measured flux maps to assembly position
  • Final assembly requires only stacking modules onto alignment rails with torque-controlled fasteners (8-10 N·m), reducing on-site assembly time by 70% and skill requirement from precision technician to general assembly operator
Expected Effect : Air gap flux density 0.9T maintained; assembly time reduced 70%; positional tolerance relaxed to ±0.15mm; angular tolerance ±0.8° vs ±0.3° conventional
Risk Control :
  • Module interface flux leakage at joints
  • dovetail wear after repeated assembly cycles
  • thermal expansion mismatch between modules
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