How to Control Linear Motor Position Overshoot in Stops

Overview of Technical Issues:

The positioning control mechanism insufficiently constrains the moving load structure during the stopping sequence, failing to adequately dissipate kinetic energy before reaching the target position, which causes the load to overshoot the desired stop point due to residual momentum; the goal is to achieve precise position control that eliminates overshoot and enables accurate stops at the commanded location.

Solution directions generated for this problem

Problem Direction 1 :

ImproveBraking force magnitude
VS
ConstraintSystem power consumption

Inspiration 1 : Cross-domain reference

Application Principle: #6 Universality
Cross-domain applicability Assess applicability
Ejector and airfoil configurations
Innovative Solution Refine solution

Dual-function motor regenerative braking with energy recovery for precision positioning

Motor serves dual role for motion and braking
How to solve :
  • Configure the positioning drive motor to operate in regenerative braking mode during deceleration phase—motor windings generate counter-torque proportional to velocity, converting kinetic energy to electrical energy
  • Install bidirectional DC-DC converter (efficiency ≥92%) between motor and power supply, enabling recovered energy (typically 40–60% of kinetic energy) to charge supercapacitor bank (rated 100–500F, voltage 24–48V) for reuse in next motion cycle
  • Implement position-triggered braking profile: at 50mm from target switch motor to regenerative mode with field current 1.5× rated, at 10mm increase to 2.0× rated for final arrest—braking torque reaches 150–200% of motor rated torque without external actuators
Expected Effect : Braking force +180%, net power consumption -45%, position accuracy ±0.2mm
Risk Control :
  • motor thermal management under high regenerative current
  • supercapacitor charge/discharge cycle life
  • converter switching noise affecting position sensors

Problem Direction 2 :

ImproveEnergy dissipation rate
VS
ConstraintSystem power consumption

Inspiration 1 : Cross-domain reference

Application Principle: #22 Blessing in disguise
Cross-domain applicability Assess applicability
Integrated energy generating damper
Innovative Solution Refine solution

Kinetic energy recovery damper with capacitor storage for positioning systems

Convert kinetic energy into stored electrical energy during deceleration
How to solve :
  • Install linear electromagnetic damper with coil windings on moving load — motion induces current that charges supercapacitor bank (rated 50-100F, 15V) while generating 80-150N braking force proportional to velocity
  • Configure regenerative circuit with rectifier bridge and DC-DC converter (efficiency ≥92%) to capture energy during final 50mm travel, storing 15-25J per stop cycle for reuse in next motion cycle
  • Implement velocity-dependent engagement — damper resistance increases automatically as speed rises (via back-EMF), providing gentle deceleration at high speed and maximum braking below 20mm/s, eliminating overshoot without active control
Expected Effect : Energy recovery 60-75%, overshoot reduced to <0.5mm, net power consumption -40%
Risk Control :
  • supercapacitor voltage tolerance ±5%
  • coil winding resistance variation affecting damping consistency
  • electromagnetic interference with position sensors

Problem Direction 3 :

ImprovePosition control precision
VS
ConstraintControl system complexity

Inspiration 1 : Cross-domain reference

Application Principle: #26 Copying
Cross-domain applicability Assess applicability
Fat tree adaptive routing
Innovative Solution Refine solution

Position-indexed lookup table for predictive stopping without adaptive algorithms

Pre-map stopping profiles to eliminate real-time computation
How to solve :
  • Conduct offline characterization of load mass (5-50kg range, 5kg increments) and approach velocity (0.1-2.0m/s, 0.1m/s steps) to generate stopping distance lookup table with 200 pre-calculated entries stored in controller memory
  • Install single optical encoder (resolution 0.05mm) at 500mm before target to measure instantaneous velocity, controller indexes table using velocity and known load mass to retrieve pre-determined brake engagement distance with ±0.2mm tolerance
  • Implement two-state mechanical brake — spring-loaded friction pad remains disengaged during approach, solenoid triggers full engagement when position matches table value, applying fixed 80N braking force until stop, eliminating variable force control and feedback loops
Expected Effect : Position precision ±0.3mm, overshoot <0.1mm; control logic reduced to single table lookup plus binary solenoid trigger; 70% fewer sensors than adaptive systems
Risk Control :
  • lookup table coverage gaps for intermediate loads
  • encoder mounting vibration affecting velocity reading
  • solenoid response delay variation ±5ms

Problem Direction 4 :

ImproveBraking force magnitude
VS
ConstraintMust not deteriorate

Inspiration 1 : Cross-domain reference

Application Principle: #15 Dynamics
Cross-domain applicability Assess applicability
Linear stopper
Innovative Solution Refine solution

Progressive wedge-brake with position-indexed cam modulation

Cam-driven wedge brake with variable force
How to solve :
  • Install a position-indexed rotary cam coupled to the linear guide—cam profile controls wedge insertion depth into rolling element brake assembly, providing 15-20% nominal force during approach and 100% force in final 15mm
  • Wedge angle 8-12° drives spherical rolling elements (SUJ2 steel, Ø6mm) against hardened guide rail (HRC58-62)—cam rotation from 0° to 180° progressively increases wedge penetration from 0.3mm to 2.5mm, amplifying normal force 6-8×
  • Torsion spring preload (0.8-1.2 Nm) maintains light wedge contact during approach—position sensor at stopping zone triggers solenoid release, allowing spring to drive cam to full engagement in <50ms, clamping force reaches 800-1200N
Expected Effect : Overshoot reduced to <0.2mm; braking force modulation 1:5-1:7 ratio; no external power for force variation
Risk Control :
  • cam profile machining tolerance ±0.02mm required
  • rolling element wear after 10⁵ cycles
  • solenoid response delay variability ±8ms
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