Driver Monitoring Systems May Prevent Thousands of Distracted Driving AccidentsJune 12, 2020 by Nicholas St. John
Distracted and drowsy driving is one of the leading causes of traffic-related deaths in the U.S. Here's an inside look at the technology that can put a stop to it.
According to the National Highway Traffic Safety Administration, 2,841 people died from distracted driving in 2018 alone. When assessing all road accidents, the Euro New Car Assessment Program (NCAP) found that ninety percent of them could be traced back to human error—which, aside from speeding violations and driving under the influence, include "inattentiveness, fatigue, [and] distraction."
To address this issue, engineers have created technology that will help prevent distracted or fatigued driving. A completely autonomous approach isn't the only option. There is a useful middle ground to balance driver and vehicle control. These systems are called driver monitoring systems (DMS).
What are Driver Monitoring Systems?
RIDE contributor Christian Wardlaw explains that a DMS works by using a charge-coupled camera that includes infrared sensors. This camera, Wardlaw explains, is mounted to a vehicle's steering column and "employs infrared LED detectors that track the driver’s eye movements, monitor head position, and even measure eyelid activity.”
This data allows the system to determine the driver’s awareness, and if needed, issue an alert to the driver to take a break or warn of potentially dangerous situations.
Distracted and drowsy driving accounts for a large percentage of traffic-related deaths in the U.S. Image used courtesy of Maxim Integrated (PDF)
Many car companies are beginning to implement this technology, including Lexus and Cadillac. These systems are able to monitor head position, eye movement, and eyelid activity. Using IR sensors, a DMS can continue to monitor these characteristics, even if the driver is wearing sunglasses or is driving in poorly-lit conditions, be it at night or inclement weather.
Wardlaw reports that Subaru is upping the ante, being the first to implement facial recognition into their DMS. With this facial recognition technology, these systems can personalize the car environment based on the driver, adjusting the seat, position, modifying the temperature, and defaulting to an individual's entertainment preferences.
Design Challenges of Driver Monitoring Systems
While the system seems relatively straightforward, there are a myriad of design challenges that those engineering driver monitoring systems need to meet. First, according to Texas Instruments, these devices need to be flexible in their placement and footprint within the car. They cannot take up much space, considering they will be mounted to a steering column or dashboard.
The device must also operate at low power to avoid draining extensive battery life from the car. With both of these requirements, hardware and software must be optimized for a minimal footprint, low power consumption, and excellent thermal management. Furthermore, these vision algorithms must be able to collect and analyze data quickly and efficiently.
Driver's face being analyzed in DMS. Image used courtesy of Texas Instruments
The devices being powered must deal with large surges and sags in battery voltage, especially considering its nominal 12 V level can drop to 4.5 V during a “cold crank," and up to 60 V during a voltage “dump,” according to Maxim Integrated (PDF).
Sensitive systems within the automobile, specifically the ignition spark circuit and radio, both emit and are susceptible to electromagnetic (EM) radiation. As such, these DMS must be able to withstand high-frequency EM noise while emitting little noise itself to protect other circuits.
Examples of DMS-Focused Components
In recent years, several semiconductor manufacturers have honed in on DMS-focused technology, taking into account the size, power efficiency, and EM radiation considerations.
For instance, Maxim Integrated has developed a product that can power DMS while taking the systems' constraints into account. The MAX2005x family of synchronous-buck LED drivers
with integrated MOSFETs are designed for automotive applications. Below is the IR-LED camera system for the DMS:
Structure of an IR-LED camera for DMS. Image used courtesy of Maxim Integrated (PDF)
As we can see, the LED driver is integral to providing a signal to the vision processor, and it must work in any environment. Maxim Integrated regards the MAX2005x family as a high-efficiency, synchronous circuit solution, illustrated in the following circuit:
Image used courtesy of Maxim Integrated (PDF)
The chip consists of two low-channel resistance n-channel MOSFETs, which help to mitigate any loss and provide 86% efficiency at 2.1 MHz and 92% efficiency at 400 kHz. This reliably drives the IR LED, which works with input voltages ranging from 4.5 V to 60 V. The device emits little EM radiation and is resistant to it.
Texas Instruments has developed an automotive processor for driver monitoring systems. TI's processor family, the TDA3x processor, is said to meet many of the common challenges of DMS. It has a small footprint for placement anywhere in the vehicle and efficiently manages hardware and software interactions to minimize power dissipation (~2.5 W).
TI's portfolio of ADAS solutions. Image used courtesy of Texas Instruments
TI also says the layout of these chips minimizes heat loss. It has the ability to pair with multiple different camera sensors, such as shutter cameras and IR LEDs. These processors also come with evaluation boards so engineers can test the processor and have multiple connections to cameras and other sensors.
Another company, OmniVision, has also developed technology to bolster DMS. Its new wafter-level 1 MegaPixel camera measures at 6.5 mm x 6.5 mm and offers ¼” optical format, 3 micron pixel size, and 1280 x 800 resolution. OmniVision also points out that its camera is more affordable than most DMS cameras that use glass lenses.
OmniVision's CameraCubeChip. Image (modified) used courtesy of OmniVision
Compared to its closest competitor, the camera dissipates 50% less power, minimizing temperature rise as well.
Driver Monitoring Systems for Safer Roads
Collectively, these devices are pushing the possibilities of driver monitoring systems in automobiles of the future. The idea of completely autonomous cars may be the ultimate end goal of safe travel, but for now, having these systems keep an extra hand on the wheel may provide the opportunity to save thousands of lives.