Resolution Subdivision
Motion control positioning systems convert continuous analog sensor outputs into high-density digital position values. Through encoder interpolation, sine and cosine voltage signals generated by optical or magnetic readheads are electronically divided into finer angular or linear steps. Electronic subdivision allows coarse physical scale pitches to achieve nanometer-level feedback resolution without forcing mechanical manufacturing tolerances to impossible limits.
Automated surface mount pick and place heads depend on signal division to hit tiny component pads reliably.
Signal Derivation
Analog photodetectors output two sinusoidal currents shifted ninety degrees out of phase during physical scale movement. Interpolation circuits digitize these analog waves using high-speed analog-to-digital converters and calculate arctangent values to determine exact position within a single grating cycle. Electronic noise and harmonic distortion in raw signals degrade division accuracy, producing cyclic error that repeats every scale period.
Gain imbalance, DC voltage offsets and phase non-orthogonality generate systematic errors in calculated position. High-speed SMT placement gantries use real-time digital signal processors to correct gain and phase errors before calculating final position counts.
Velocity Boundary
Maximum output frequency of the interpolator limits the top axis velocity at high interpolation factors. High subdivision ratios increase feedback resolution while reducing maximum allowable feed rate across the linear motor stroke. Bandwidth constraints in input processing electronics restrict operation when scale travel speeds generate high-frequency analog signals.
Surface mount equipment engineers select interpolation factors that maintain position loop stability during rapid moves without exceeding processing throughput limits.
