VIBRATION MODE ESTIMATION OF SINGLE LINK FLEXIBLE MANIPULATOR BASED OF SDFT PHASE LOCKING SCHEME

Abstract

An estimation method based on sliding discrete Fourier transform (SDFT) integrated with phase locked loop (PLL) is introduced for vibration mode estimation of single-link flexible manipulator (SLFM). Based on Euler-Lagrangian state space model and first vibration mode frequency, SDFT PLL is designed to estimate first vibration mode and harmonics that appear in tip deflection. Instantaneous change in tip deflection due to payload conditions is tracked by adaptive sampling frequency control. State space model, estimated amplitudes and frequencies of tip deflection including harmonics are validated through experiments. Further, experimental investigation on SLFM demonstrates the effectiveness of online vibration mode estimation method. Adaptive controller is proposed to control the tip deflection of SLFM based on on-line frequency estimator using SDFT PLL. Instantaneous change in tip deflection frequency due to change in payload is fed to frequency estimator. Adaptive controller parameters are updated using estimated frequency. Adaptive controller efficiently suppresses the tip deflection of SLFM.