Structural Dynamics
Oscillatory physical systems display frequency response shifts when drive amplitude exceeds linear spring limits. Non-linear mechanical resonance alters the amplitude peak and resonant frequency of a MEMS structure as displacement increases beyond small signal assumptions. Duffing effects cause restoring forces to deviate from Hooke’s law at large deflections.
Resonance curves tilt toward higher or lower frequencies depending on whether spring stiffness hardens or softens.
Higher Harmonics
Exceeding linear displacement limits generates higher order harmonic components in structural motion responses. Energy transfers from the fundamental drive frequency into harmonic modes, distorting output waveforms. Harmonic distortion limits the usable dynamic range of resonant sensors like MEMS gyroscopes.
Control electronics must suppress harmonic excitation to maintain stable oscillation amplitudes.
Operating Instability
Hysteretic amplitude jump phenomena occur when sweeping drive frequencies across non-linear resonance peaks. Abrupt changes in vibration amplitude occur depending on whether frequency sweeps move upward or downward. Jump phenomena disrupt closed loop drive circuits, causing control loop loss.
Amplitude stabilization circuits limit displacement to keep structural operation strictly within linear response boundaries.
Measurement Standard
Characterization sweeps drive amplitude while recording frequency response curves on laser Doppler vibrometers. Testing identifies non-linear onset thresholds and maps spring hardening or softening coefficients. Operational limits define maximum drive voltages to prevent non-linear distortion during sensor operation.
