Highly-time-resolved FMCW LiDAR with synchronously-nonlinearity-corrected acquisition for dynamic locomotion

Abstract

Highly-time-resolved and precise tracking of position, velocity, and acceleration is urgently required when highly dynamic legged robots are walking, trotting, and jumping. Frequency-modulated continuous-wave (FMCW) laser ranging is able to provide precise measurement in short distance. However, FMCW light detection and ranging (LiDAR) suffers from a low acquisition rate and poor linearity of laser frequency modulation in wide bandwidth. A sub-millisecond-scale acquisition rate and nonlinearity correction in the wide frequency modulation bandwidth have not been reported in previous studies. This study presents the synchronous nonlinearity correction for a highly-time-resolved FMCW LiDAR. The acquisition rate of 20 kHz is obtained by synchronizing the measurement signal and the modulation signal of laser injection current with a symmetrical triangular waveform. The linearization of laser frequency modulation is conducted by resampling of 1000 intervals interpolated in every up-sweep and down-sweep of 25 µs, while measurement signal is stretched or compressed in every period of 50 µs. The acquisition rate is demonstrated to be equal to the repetition frequency of laser injection current for the first time to the best of authors’ knowledge. This LiDAR is successfully used to track the foot trajectory of a jumping single-leg robot. The high velocity up to 7.15 m/s and high acceleration of 365 m/s2 are measured during the up-jumping phase, while heavy shock takes place with high acceleration of 302 m/s2 as the foot end strikes the ground. The measured foot acceleration of over 300 m/s2, which is more than 30 times gravity acceleration, is reported on a jumping single-leg robot for the first time.

Rotary robotic gripper with LiDAR-tactile sensor fusion

“…The real-time program of the algorithm of searching peak is run to acquire the signals in time domain and analyze the frequency signals, as reported in Refs. 23 and 24. The maximum amplitude in the frequency spectra is extracted from Fig.…”

Robotics Perception and Control: Key Technologies and Applications

“…LiDAR (Light Detection and Ranging) is a technology that uses laser pulses to measure distance and speed, and it is widely utilized in robotic control and navigation systems. Depending on their operating modes, LiDAR can be classified into several main types: solid-state LiDAR [71], flash LiDAR [72], phase-shift LiDAR [73], and frequency-modulated continuous-wave (FMCW) LiDAR [74]. In robotic control, LiDAR is employed for navi-gation and positioning, environmental perception, target recognition and tracking, and obstacle detection and avoidance.…”

FMCW light source with a feedback optical phase-locked loop

“…FMCW LiDAR has no blind area of ranging, which solves the problem that the distance and positioning accuracy of pulse detection are mutually restricted in principle. It has become a new generation of measurement technology with high precision positioning and long-distance detection capabilities [5,6] .…”

“…The ranging resolution and accuracy of LiDAR system are affected by frequency sweep linearity and phase noise of FMCW light source [7] . FMCW LiDAR could be applied to lip-reading if the image resolution and imaging rate were high enough [5,8] . The ranging accuracy could be improved by averaging the sweep frequency measurement data over multiple periods [9][10][11] at the expense of imaging rate reduction.…”