1.
Equipment
A
self-driving car would be equipped with many sensors to provide information
about road conditions in order to control its speed, brake, steering wheel as
well as safe distance with other objects or cars on the roads. Those equipment
could be
-
GPS with precision to lane
-
Photo sensor with image processing or pattern recognition capability
-
Radar or laser beam to estimate safe distance between the car and
other objects
-
Weather forecast center or the information control dashboard
should be connected to a local weather forecast station via wireless (mobile router of
a cellular phone) in order to know the current weather such as raining or
snowing.
Figure 1. A self-driving car with its sensors
2.
Laser beam
The
car would be equipped with 8 laser beams in order to estimate the distance
between itself and other objects in front of, behind, and around it.
There
are many laser tools to estimate distance of an object and a laser tool in the
market.
The
laser beam would help to estimate, or control speed of a car, or its position (moving
a little bit to the right or left) for a safe distance on the roads with other
objects around it.
There
is a physic formula to calculate distance based on the bounced back signal
strength of a wave signal, i.e. used by laser beam in this case.
If
the car in front of it is driving at slower speed than the upper speed limit
suggested by the GPS, the car could try to change lane to pass that car.
The
front/rear of the car could be equipped with 3 laser beams each to detect objects in the front/back of it.
In this note, the laser beams and photo sensors were
used to determine safe distance. For changing lanes and other tasks, more laser
beams and sensors would be needed.
3.
Photo sensor or capture
a.
Laser beam failed
There
is a case that the laser beams would fail, i.e. snowing or raining days.
In
the case that the distance reported by the laser beam changed drastically, the
photo sensors would be activated to confirm the weather around the car and estimate
safe distance along with the laser beam.
The
photo sensor is special that it could estimate if an object similar with a car’s
shape is so close to itself in order to slow down the vehicle.
b.
Rain fall and snow fall
The
rain fall and snow fall could be such a way that it blocked the laser beam to make
system thinks that a wall was around the car.
There
would be a sample of data reported by the laser periodically. For example, the
car was so close to an object, but 50 msec later the car is at safe distance to
objects around it. By confirming the laser data reported with weather forecast,
system would mark this situation as rain fall or snow fall. Otherwise, system
would report laser beam failed, and repair was suggested.
The
laser beam on the side of a car would likely report intermittent safe distance
and dangerously close repeatedly. However, to make system less expensive the
photo sensors would be equipped at the front and back of the car, i.e.
direction of a fast moving car.
By coupling a photo sensor and laser beam the
car could keep safe distance with other objects.
4.
Clarification
By
adding more laser beams or photo sensors in around a car would increase the
chance to detect safe distance in snowy or rainy days, but it is not a bullet
proof solution.
To
detect a car was in its blind spot, the car could be equipped with more laser
beams and photo sensors installed on the left side, right side, and corners of
the car.
5.
Explanation of devices
a.
GPS navigator
With
precision to lane, the control center could help to keep a car in correct lane.
With knowledge of number of lanes on a road, control center could help the car
to change lanes correctly.
b.
Laser beam
The
laser beam is using technology as used in radar. It beams waves and catches the
rebound waves in order to determine rebounded signal strength. Based on the
rebounded signal strength, it estimates the distance between the car and the
object blocking the beams.
c.
Photo sensor
The
photo sensor would capture images. Image processing software would compare the
captured image with its data in database for image recognition, i.e. snow,
rain, car, walls, etc. in the photo. Based on the captured image, the control
center would take appropriate actions.
I
don’t think a photo sensor could estimate the distance between the car and
object in the photo unless it knew the object’s size in advance. For example,
photo of the back of a Toyota Camry is stored in database. Based on photo,
system uses recorded real size of a Camry plus size of the Camry in the photo,
it could estimate the distance.
d.
Weather forecast center or car’s control center
Based
on information received from a local Weather Forecast Station via wireless
Internet, the control center could confirm and decide appropriate actions.
A
photo sensor could also detect snow or rain based on sample data in its
database stored in the control center.
The
car’s computer system or control system could connect to the information
control dashboard, where users could connect it to a cellular phone via WiFi.
6.
Using photo sensors for traffic signs
Unless
each traffic intersection implement signal transmitters to inform the current
traffic light such as red, yellow, green AND stop sign, a car must use its
photo sensors to detect traffic signs.
If traffic signal transmitters implemented, the car could catch the signals and adjust its
speed, and use photo sensors to detect cars around it in order to move correctly.
The
photo sensors could detect “green, yellow, red, or color arrow” or “stop sign” used
in a traffic intersection. It compared to its database for a known patterns
such as square box around a green, yellow, red spots.
Basically the car must
have a database of images for known objects on the roads, so it can compare and
decide the meaning of objects captured in a photo.
7.
Backup strategy in case of technology failed
Self-driving
cars have been relying on first on GPS for lane precision, or second on lane
marking to keep a vehicle travelling in correct lane.
However,
military or GPS providers could take the satellites back for upgrade or
different tasks. Thus the backup plan would be return to check the lane marking
to guide vehicle correctly if GPS system failed. The lane marking is not a
reliable source neither as many locations covered with snow during winter time.
Snow plowing process would erase or fade lane marking, too. We cannot expect
cities to maintain lane marking in perfect conditions.
If
the system could not find solid lane marking for 1 meter or missed a broken
lane marking, it should slow down; notify the driver to take over control; if
the driver didn’t take over control for 2 seconds, it should turn on the hazard
lights and bring the car into full stop on the current lane (the last known
trajectory would be the best guess by the system in this situation) if it
couldn’t change lane and park on the side road. The car system should be disabled for 1 minute to calm down the upset driver as well as giving the driver time to access traffic around the car before merging back into traffic manually.
8.
Wireless protocol
If
many car manufacturers used the same laser beam and frequency for detecting
safe distance between cars on the roads, then a simple protocol embedded in the
laser waves should be implemented by those car manufacturers. For example,
-
Common message ID: the first few characters to identify this is a
laser beam message.
-
Next 5 characters to identify a car manufacturer, e.g. TOYOT for
Toyota
-
The next 9 characters are proprietary to contain ID of the car,
e.g. the first 2 characters for model, and the last 7 characters for unique ID
of that car.
Since
there wouldn’t be necessary for vehicle to vehicle communications to avoid
hackers manipulate all cars on a road causing accidents, the last 9 characters reserved
for each manufacturers providing flexibility.
Manufacturers should avoid using unique ID such
as vehicle’s VIN and serial number as those numbers should remain private for
law enforcement, insurance, and vehicle maintenance.
