Session: 17-01-01 Research Posters

Paper Number: 72321

Start Time: Thursday, 02:25 PM

72321 - Water Removal on Lidar Sensors Using Vibrations 

In the near future, autonomous vehicles are expected to use LIDAR technology for sensing surrounding objects with minimal human intervention. However, adverse weather can decrease the sensor’s performance by up to 50 percent. Most self-driving cars’ LIDARs are severely affected by the water absorption spectrum. A thin layer of water becomes the equivalent of a light filter, which happens under rain or fog conditions. Thus, it is imperative to enhance the water removal from the sensor cover to minimize signal attenuation. Water droplet motion is also crucial for other systems. Further understanding the transient dynamics of water droplets can help as well for water recovery (power plants) or water removal (fuel cells), where vibrations are one of the multiple techniques used. The most common method of droplet removal is by a gravity-driven force, where studies show that vibrations help improve droplet detachment and motion. Surface tension gradients have also been shown to drive droplets as well as the interaction by surface coatings. Researchers have investigated droplet motion under horizontal and tilted surfaces subjected to vibrations. It is a common phenomenon in many systems, but the mathematical modeling is complex for liquid, gas, and solid interface interaction under vibrations. Low-frequency (<100 Hz) and high-frequency (>10 kHz) surface vibrations have also been studied earlier for droplet spreading. This project evaluates the effects of different vibration frequencies on water droplets on vertical surface motion.

This work studied the dynamics of water droplets sliding down a vertical surface subjected to vertical vibrations. Water droplets volume ranging from 0.5 µL to 5 µL (2 to 3mm in diameter) were studied while attached to a poly(methyl methacrylate), PMMA, surface. Droplets were generated by utilizing a Transferpette S pipette from Brandtech Scientific, Inc. An electrodynamic shaker, K2007E01 from The Modal Shop, Inc., was used to generate the vibrations, and a piezoelectric PCB Piezotronics accelerometer was used to record the relative acceleration of the sensors under these conditions. Experimental results were analyzed utilizing vibration frequencies ranging from 10 up to 100 Hz at multiple acceleration levels (from 0.048 to 14.7 m/s²). Droplet behavior was analyzed under increasing acceleration at different frequencies rather than studying a single water droplet size or a fixed acceleration value. Water droplets 6 µL and larger move down due to gravity effects at velocities near 0.2 mm/s and were not part of this study. A variety of water droplet sizes represents better the wet conditions of LIDAR covers. Water droplets were found to remain either static or sliding under vibrations at given conditions. Droplets oscillated under low acceleration regimes but did not displace from their position, while at higher acceleration, the sliding motion was more pronounced. Water droplet velocities were found to vary as well, while higher velocities are related to higher acceleration levels. Droplets larger than 2 µL were driven down by frequencies under 50 Hz with acceleration levels in between 0.2 to 0.4 m/s². Droplets 1 µL and smaller required higher acceleration levels to be driven (14.7 m/s²).

Presenting Author: Kyle Steel Florida Polytechnic University

Authors:

Colton Frear Florida Polytechnic University
Kyle Steel Florida Polytechnic University
Edwar Romero -
Gerardo Carbajal Florida Polytechnic University
Zahra Sadeghizadeh University of California