hello everyone my name is yang zhang today i'm really happy to be here to present our work
on vibrosight plus plus, city-scale sensing using existing retroreflective signs and markers
this work was done in collaboration with sven, jesse, and my advisor chris harrison
urban environments are expansive and complex with a wide range of facets that city planners, business
owners, citizens and many other stakeholders might wish to sense to increase efficiency, to improve
quality of lives, and to become more sustainable today the most common approach to city-scale sensing
is to distribute hundreds if not thousands of physical sensors across the urban landscape
these devices require power and connectivity and often cost thousands just to install
let's along maintain. in this research we propose an entirely different approach to
sense at city scale in a very low cost manner. we build upon advances in laser vibrometry particularly
our prior work on vibrosight which uses laser to measure the vibrations of distant object
for smart applications typically the sensing range of a laser vibrometer
is limited to just a few meters, however with the addition of a retro-reflective marker
this sensing range can be then increased to several hundred meters
even better, cities have already deployed many thousands of retro-reflective markers and signs in the form
of street signs, construction barriers, road studs, license plates, and many other markings
while, you might be wondering what can we do if we can sense vibrations off of these objects around the city.
here is one example, we found that the signs on mailboxes are actually retroreflective
so we use vibrosight plus plus to sense vibrations off of them. in this case we can use this vibration
data to infer their utilization which can be further used for smart pickup scheduling
the sensor bundle consists of a 200 milliwatt laser which can be eye safe by adjusting its divergence
we also add a photo detector to it with an optical band-pass filter and the
output of this photo detector is then sampled by an audio preamp which is then streamed to a laptop
for further computation. the entire bundle is installed on a high-precision pan-tilt platform
here is a video of our system looking for retroreflectors in the environment
overall, our system finds retroreflectors by scanning the environment and measuring the intensity of
the reflected laser light. specifically, in each direction we turn on the laser for 50 microseconds
for one measurement and then we turn it off for another measurement. the deltas between
these two measurements across all directions compose a reflectance map which we then threshold
and find clusters with, and then we mark the centers of these clusters
as the location of retroreflectors in the scene. we run an apparatus evaluation with a wide
range of retro reflectors commonly found in urban environment. overall results indicate that our
system can detect vibrations and motions robustly up to one kilometer and works with a wide range
of angles, retroreflector structural types, and colors please refer to the paper for more details
now let me conclude this talk with some example applications. we can detect vibrations of these
road paints for vehicle count, we can also quickly scan the license plates on vehicles
based on which we can detect their car types air pressure waves used by loud machines such
as engines of buses can also be picked up remotely, and we can also detect vibrations off
of infrastructure such as a bridge for infrastructure health monitoring
overall, we believe our ultra-low-cost approach is a new powerful way to achieve the flexibility, scale,
and density of sensing needed to enable truly smart and responsive urban environments. thank you