Session: 17-01-01 Research Posters

Paper Number: 77567

Start Time: Thursday, 02:25 PM

77567 - Solar Heat Flux Effect on Rate of Water Droplets Deposition on Lidar Sensor Covers 

Autonomous vehicles systems use several sensor systems for measuring distances and obstacle detection. Some of these sensors include Computer Vision (CV) systems using a camera, RADAR (radio detection and ranging) systems, ultrasonic imaging systems, Global Position Systems (GPS), and LIDAR systems. LIDARs are particularly suitable for autonomous driving due to centimeter-ranging accuracy and resilience against brightness change compared with a camera. LIDARs work by sending pulses of laser light toward a target and then recording the reflected light that returns to the LIDAR sensor. However, these devices are affected by dense haze or rain due to the short-wavelength light that can be easily deflected under these conditions. If a steady temperature gradient exists, the light will follow a curved path toward the cooled air. Cold air has a higher index of refraction than warmer air.  This research is oriented to the situation when the rain or fog conditions stop. An experimental study was conducted to determine how fast the water droplet is removed from a LIDAR sensor's surface at different periods. Two mechanisms can affect the mass transfer mechanical or heat transfer effect of water droplets from a solid surface. The first mechanism is the drag force exerted by the airspeed interacting with the water droplets. The second mechanism is the heat transfer by solar radiation; in this case, the radiation heat transfer increases the temperature of the water droplet and the solid surface; therefore, the temperature of water increases and the surface tension diminishes. The reduction of the surface tension reduces the surface tension force resistance, and the drag force caused by the airspeed can easily overcome this force; thus, it can detach more water droplets from the surface.  The rate of droplets removal from the solid surface is referred to in the present study as the rate of mass transfer. A wind tunnel was applied to replicate the airspeed effect on water removal from the LIDAR sensor, the airspeed in the wind was set to 30.4 m/s. Two 500-W heat lamp bulbs placed outside the wind replicated a 656 W/m² of solar radiation heat flux. Water was sprayed on the surface of the LIDAR sensor to generate the water droplets; the volume of water droplets volume range from 0.5 µL to 5 µL with 2 to 3mm in diameter. The solid surface of the LIDAR sensor is a poly(methyl methacrylate), PMMA. The experimental results showed that the rate of mass transfer decreases quasi exponentially versus time.  The maximum speed of mass transfer measured from the LIDAR sensor with airspeed and radiation heat transfer was 0.007 g/s.

Presenting Author: Colton Frear Florida Polytech University

Authors:

Colton Frear Florida Polytech University
Danil Pegin Florida Polytechnic University
Gerardo Carbajal Florida Polytechnic University
Edwar Romero Florida Polytechnic University
Zahra Sadeghizadeh The University of California, Davis