Abstract
Frequency modulation continuous wave (FMCW) Lidar inevitably suffers from vibration and nonlinear frequency modulation, which influences the ranging and imaging results. In this paper, we analyze the impact of vibration error coupled with nonlinearity error on ranging for FMCW Lidar, and propose a purely theoretical approach that simultaneously compensates for time-varying vibration and nonlinearity in one-period triangular FMCW (T-FMCW) signals. We first extract the localized characteristics of dechirp signals in time-frequency domain by using a second-order synchro-squeezing transform (second-order SST), and establish an instantaneous ranging model based on second-order SST which can characterize the local distributions of time-varying errors. Second, we estimate the nonlinearity error by using time-frequency information of an auxiliary channel and then preliminarily eliminate the error from the instantaneous measurement range. Finally, we construct a particle filtering (PF) model for T-FMCW using the instantaneous ranging model to compensate for the time-varying vibration error and the residual nonlinearity error, and calculate the range of target by using triangular symmetry relations of T-FMCW. Experimental tests prove that the proposed method can accurately estimate the range of target by compensating for the time-varying vibration and the nonlinearity errors simultaneously in one-period T-FMCW signal.
Highlights
To compensate for the vibration and nonlinearity for one-period T-frequency modulation continuous wave (FMCW) Lidar, this section first extends the traditional ranging model to an instantaneous ranging model based on second-order synchro-squeezing transform (SST) which could depict the time-frequency characteristics of the dechirp signals
The second example added two sinusoidal vibration errors with frequencies of 900 Hz and 40 Hz and amplitudes of 2 μm and 50 μm which are coupled with the nonlinearity error shown in the above subsection, and Gaussian white noise with a signal-to-noise ratio (SNR) of 5 dB was added to the measurement dechirp signal
In order to reduce the time-varying coupling errors, we first establish an instantaneous ranging model based on second-order SST by using the timefrequency characteristics of dechirp signals
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. Proposed a movement error compensation method by using a Kalman filter technique which only needs one tunable laser driven by up and down optical frequency scanning This method achieved high-precision in range measurement by using consecutive echoes. Lu et al [22] introduced a phase-locked loop on the basis of the above ranging system and effectively solved the nonlinear problem of the clock signals This method can simultaneously eliminate vibration error and nonlinearity error and has a remarkable prospect in the applications of ranging, but it needs two lasers. In Section we use four experimental tests to verify the effectiveness of the proposed method to simultaneously compensate ideal coherence detection of FMCW Lidar, and the second subsection analy for the time-varying vibration and nonlinearity in point target and 3D target imaging.
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