Compliance estimation and structural observability

Purpose

• Estimate quasi-static structural behavior under load

• Detect excessive compliance that risks tolerance loss

• Provide slow-varying state information for process supervision

• Not intended for real-time control loops

Tilt estimation

• Derived from accelerometer data

• Uses gravity vector for orientation reference

• Strong low-pass filtering applied

• Valid only in quasi-static conditions

• Used to estimate spindle plate rotation under load

Strain gauge measurement

• Strain gauge mounted on X carriage

• Measures bending of X gantry under load

• Acts as cutting-force proxy

• Provides information independent of vibration measurements

Motor current as load proxy

• Motor current monitored at spindle drive

• Two components used:

  • fast component: - incipient stall detection

  • slow envelope: - mean cutting load estimation

Compliance model

• Structural compliance model maintained in ECU

• Model inputs:

  • spindle plate tilt

  • X-carriage strain

  • motor current

• Model output:

  • estimated tool/spindle deflection envelope

• Model characteristics:

  • calibrated using known static or quasi-static loads

  • evaluated only in steady-state conditions

  • versioned and recalibratable

• Model is:

  • a slow observer

  • not part of safety system