Collision Avoidance/Detection System Research

Owned by Kevin Li
Last updated: Jan 21, 2021
3 min read

Collision Detection Features

We begin by considering a few of the various features associated with a vehicle collision avoidance system (CAS). Provided below are descriptions regarding the most commonly implemented features for a vehicle CAS.

  • Forward Collision Warning (FCW): Visual and/or audible warnings/alerts to notify the driver of a potential collision at the front end of the car

    • A FCW system will alert the driver when the distance between the vehicle ahead and the front of the driver’s own vehicle is too close for the driver to appropriately break at their given speed without avoiding a collision

    • 27% reduction in front-to-rear crashes, hence the most significant collision avoidance system feature

  • Blind Spot Warning (BSW): Visual and/or audible alerts to notify the driver that the vehicle is in the blind spot of a vehicle in an adjacent lane

    • 14% reduction in lane switching crashes and a 23% reduction in lane switching crash injuries (reduces the severity of collision in essence)

  • Lane Departure Warning (LDW): A visual, audible, or haptic alert to notify the driver that its vehicle is crossing lane markings.

    • 11% reduction in sideswipe and head-on collisions

    • 21% reduction in the probability of injury due to sideswipe and head-on collisions

 

 

Driver Assistive Features

Listed below are several common driver assistive features which may aid the driver in the event of a predicted collision.

  • Adaptive Cruise Control: Uses radars or lasers to adjust cruise control speed by throttling to maintain an appropriate between the the driver’s vehicle and any vehicle ahead

  • Automatic Emergency Braking (AEB): The automatic applying of brakes based on sensor feedback to prevent or minimize the severity of collision (reducing collision speed)

  • Rear Automatic Emergency Braking: The automatic applying of brakes to prevent the vehicle from backing into an object using a cross-traffic monitoring system or sensors

  • Electronic Stability Control (ESC): Anti-lock brake technology; ESC applies brakes automatically to help steer a vehicle during loss of traction between the vehicle and the surface. Sensors may be used to determine which wheels need to brake or accelerate.

 

 

Commercial Use

Car companies do not provide detailed selection choices regarding their CAS sensor implementations. Provided below are the types of sensors used from a few popular car companies.

  • Honda:

    • Front Windshield Camera - Monocular Camera: Installed at the center of the windshield of the vehicle

    • Front Radar Unit - Millimeter Wave Radar Unit: Installed at the front of the vehicle (precisely embedded seamlessly with the logo)

  • Alfa Romeo:

    • Camera: Installed at the center of the windshield

    • Radar: Installed behind the front bumper

  • BMW:

    • Camera: Installed at the center of the windshield

    • Sensors (vague, assumably radar): Installed at the front bumper

This combination of a camera installed at the center of a vehicle’s windshield and a radar installed at the front of the vehicle is consistent with the companies above. With further searching, one may notice that this is common among most other companies as well.

 

 

Sensor Types

The use of a camera appears as unnecessary in order to implement the core features of a basic CAS. With this in mind, we will only consider various types of radars and their strengths and disadvantages. Listed below are common radars used for CAS.

  • Millimeter Wave Radar Sensors (mmWave):

    • Transmits short-wavelength electromagnetic wave signals that objects in their path reflect (operates at 24GHz and 77-79GHz)

  • The capturing of the reflected signal provides information regarding the range, velocity, and angle of the objects to the radar (highly directional)

  • High accuracy due to short wavelengths (can detect movements that are as small as a fraction of a millimeter)

  • Advantages:

    • Has the ability to mitigate environmental factors

    • Not affected by heat or light

    • Antennas are smaller than those for ultrasonic, hence easily packageable

    • Can be adjusted to for different detection ranges

  • Disadvantages:

  • Manufacturers/Producers: Texas Instruments, MediaTek

  • Ultrasonic Radar

    • Move at the speed of sound and are thus much slower than mmWave radars and LIDAR

    • Advantages:

    • Disadvantages:

      • Are not optimal for circumstances which require fast response rates (travels at the speed of sound)

  • LIDAR

    • Uses lasers and mirrors to map surrounding environments with echo imaging in real-time

    • Advantages:

    • Disadvantages:

      • Affected by natural light and heat and thus may have weak signal transmissions which may impact mapping ability

      • Physically large

      • Expensive

With a bit of research, one can reason that mmWave radars may be a strong choice for a radar sensor to be implemented in a CAS. Texas Instruments has extensive documentation on their mmWave radars and are available on DigiKey for a reasonable price.

 

 

References