AutoDrive | Automatic GPS Based Vehicle Driving System
AutoDrive is a completely automated highway driving system. By 2030 all major interstates in the US are expected to support "AutoDrive lanes" with completely automated car and commercial vehicle driving. Any car updated for AutoDrive can enter these lanes and enjoy speed limits of around 130 mph.
In this series of articles we will go through the design and development of this remarkable technology.
- GPS based position determination for accurate steering of the car. GPS position is used to accurately locate the vehicle's position on the map and then steer the car according to the path specified by the map.
- Inter Vehicle Signaling (IVS) is used for keeping track of neighboring vehicles. IVS is used to detect speed changes and respond to lane change requests from other vehicles.
- Radar feed is used to identify objects in vicinity of the car. The main objective of the radar is to detect non-vehicle objects that might be present on the highway. The precision radar is capable of detecting objects that are more than 3 cm in height.
- Map updates are obtained over a wireless internet connection. Most map updates are obtained at the time of trip start. The maps are extremely detailed and store information about the different lanes with an accuracy of +/- 1 cm.
- Weather feed is used to adjust driving parameters according to the current weather conditions.
- Construction and road closure detection is implemented using IVS. An IVS transmitter is placed in a closed lane. Vehicles receive the IVS signal from the transmitter and decide to change lanes.
GPS Based Position Determination
The current GPS position of the vehicle is the most important piece of information in the AutoDrive system. A GPS receiver is fitted in all vehicles retrofitted with the AutoDrive system. The salient features of the GPS system are:
- GPS receiver used in the AutoDrive system has the accuracy of 1 cm.
- The current GPS position is constantly compared with the map coordinates to determine the exact location of the vehicle.
- Since the GPS position is accurate to 1 cm level, it is also used to steer the vehicle so that it stays in the center of its lane.
Inter Vehicle Signaling (IVS)
IVS is used to adjust to speed changes and lane changes of the neighboring vehicles.
- All vehicles broadcast the GPS position of their center and their dimensions in terms of length and width and their speed. Vehicle type is also included in the broadcast. The vehicles determine their neighboring vehicles by keeping track of these broadcasts from vehicles that are within 100 feet. All broadcasts received from vehicles outside the 100 feet radius are ignored. (Note that the 100 feet check does not apply to IVS transmitters used for lane closures. See the section on lane closures).
- When a vehicle needs to change its lane, it sends a lane change request message containing the direction if it is left or right, to the neighboring vehicles.
- In response to a lane change request received from a neighbor or in response to an obstruction on the road, a vehicle sends a braking request message containing the deceleration rate to its neighbors.
- IVS supports priority routing of emergency vehicles. If the broadcast received from a neighboring vehicle indicates that it is an emergency vehicle, the vehicle will automatically change lanes to make way for the emergency vehicle.
- If a vehicle fails on the road, it broadcasts a speed of value zero thereby indicating that it is crippled.
An AutoDrive vehicle has a radar installed. The radar monitors the presence of obstructions other than vehicles like human beings, animals, fallen trees or rocks. The radar feed is used to take appropriate lane and speed change actions to steer clear off the obstructions.
Before the start of a journey, an AutoDrive vehicle downloads from the internet, the map of the complete path from source to destination. This map has details up to the level of number of lanes, their curvature etc. This map guides the AutoDrive vehicle to the destination.
Weather updates about the path are constantly received during the journey. If extreme weather conditions are detected, appropriate rerouting is carried out. This rerouting is performed by obtaining map updates on the fly. Weather feed is also used to adjust driving parameters like braking distance, wheel grip and radar visibility.
Construction and Road Closures
If a lane is closed for construction, an IVS transmitter is located at its center which broadcasts its GPS position, width of the lane, the length of closure and a speed value of zero. For example, if a one mile lane closure is required, an IVS transmitter is kept at half mile and it broadcasts its length as 1 mile and speed as zero.