Mubina
Toa
Imagine a commute to work where, with
the press of a button, your electric car automatically drives up to you, opens its
door to let you in, navigates on its own through traffic to find the quickest route,
pulls up to a garage with automatic gates, parks itself in an available spot, drops
you off and charges itself on its own while parked. With the advancement of electric
self-driving cars, this future is already starting to become a reality.
Sensors are at the heart of automation
– embedded not only within vehicles to make smart driving decisions, but also in the
surrounding environment to create a network of intelligence. With an interconnected
system of sensors and data mapping the world as we see it, the road to innovation is
truly limitless.
How Ultrasonic Technology Performs
Five Unique Tasks to Improve the Driving Experience
Ultrasonic
sensors use sound waves to detect the presence or proximity of an object. This is
done by transmitting a sound wave in the ultrasonic frequency band and listening for
the return echo, which would be the result of the sound wave bouncing off an object
in range. Time of flight describes the round-trip time it takes for a transmitted
sound wave to come back to the receiver after bouncing off an object. Figure 1 is a simple formula that calculates the distance of an object from the ultrasonic
sensor:
Although many technologies can detect
presence, proximity and position, ultrasonic is a popular choice because of its low
system cost, performance in dirty environments, and ability to detect glass surfaces
and perform in all lighting conditions.
Let’s explore how ultrasonic
technology performs five tasks in and around the vehicle to improve the driving
experience.
1. Garage Gate Sensing
Gate sensors
are implemented in garages, parking lots and other facilities for ticketing and
security purposes. Ultrasonic sensors are beneficial here for their ability to
operate indoors, outdoors and in any lighting condition. Ultrasonic technology makes
it easy to detect larger objects like cars and motorcycles and dismiss smaller
objects like animals and debris, therefore reducing the rate of false positives
presented by other presence-sensing technologies.
2. Parking Spot Sensing
Larger
garages are adopting parking spot sensors to indicate whether a parking spot is
empty or occupied. These sensors send information to a central server, which
aggregates the number of empty and occupied spots in a certain area or floor of a
garage and displays this information in external displays to help guide drivers to
open parking spots. Sensors can be mounted on the floor or ceiling, but are
typically mounted on the ceiling for easy installation in existing facilities. To
conserve power, sensors can be duty-cycled and sampled once every few minutes to
maintain a pretty accurate count.
3. Park Assist
In the past,
ultrasonic park assist sensors were employed only in higher-end vehicles, helping
drivers understand their surroundings by detecting obstructions. With the cost of
ultrasonic sensors decreasing and their functional capabilities increasing, they are
becoming more prevalent in lower- and mid-end vehicles as well. As the push towards
autonomy progresses, employing ultrasonic park assist sensors in conjunction with
other sensors will aid in the automated parking of vehicles. Industry standards
require that ultrasonic park assist sensors sense at a range of up to 5 m and detect
objects as narrow as a 75-mm wide.
4. Wireless Charging Pads/electric
Vehicle Charging Stations
As electric
vehicles become more common, so are charging stations. They typically come in one of
two topologies: a wireless charging pad or a station that’s similar to a traditional
gas station. Wireless charging pads are typically mounted on the floor of a parking
spot, waiting for a car to drive up over it. Ultrasonic sensors ensure that the
charging pad is fully covered under the vehicle to ensure best-case efficiency when
charging. An embedded sensor can also ensure that there are no unintentional objects
in proximity (such as a pet) before charging initiates. Wireless charging stations
often have sensors on them as a measure to conserve electricity by keeping the
station in sleep mode until it detects a car in proximity.
5. Kick-to-open Trunks
Kick-to-open trunks or smart trunk openers are becoming more prominent in vehicles. They enable hands-free opening of the trunk by hovering a foot below the bumper. Other body sensors located around doors and trunks
can make sure that there is enough space to open and close them without hitting a wall, pole, another vehicle or a human. Capacitive sensing is used in these applications, but due to sensor failures in icy or snowy conditions, ultrasonic
sensing is preferable, as such environments don’t affect its performance.
Get Started with TI’s Ultrasonic Technology
Figure 2 below is a screenshot from the PGA460-Q1 ultrasonic sensor signal conditioning evaluation module with transducers, which helps you evaluate the performance of TI’s ultrasonic sensing IC in detecting obstructions and calculating Time-of-Flight.
The figure shows the echo output (the yellow line) and time-varying gain and threshold registers (the white and blue lines). The built-in threshold registers make it easy for many of these applications to decide when to perform a function.
For example, in the parking spot sensing example, it’s possible to set the threshold to ignore objects like a small animal but still detect desired objects like vehicles, which produce a stronger signal.
Ultrasonic sensing is a beneficial technology for proximity and obstruction detection. It allows for intelligent decision making in vehicles, enabling them to sense the world around them to automate processes, improve efficiency and enhance
safety.
Additional resources:
Figure 1 Equation 1
Figure 2 PGA460 Ultrasonic GUI