Self-driving cars with sensors v1.4

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.