Writing in International Journal of Vehicle Autonomous Systems, Matthew Best of Loughborough University (UK) explored the optimization of a vehicle’s standard brake, acceleration and steering control inputs in the context of avoiding collisions. He devised a computer simulation that allows all those parameters to be optimized concurrently during a safety maneuver and showed how speed reduction and swapping lanes might be carried out by an autonomous vehicle.
The optimal rapid lane-change would inevitably be an aggressive, high “g” maneuver that would destabilize the vehicle, and additional computing power would be needed to act quickly to correct under steer and other issues that arise during and after such a vehicle movement.
The high-speed lane switch would likely be rarely used in a real-world autonomous drive, but could, in exceptional circumstances, allow driverless or robot vehicles to be safer on roads that which they share with other such vehicles and vehicles with human drivers.
Best points out that simulations at 70 mph (113 km/h)—the UK national speed limit on motorways—reveal that braking alone would not lead to a safe outcome in many situations, so a lane swap would almost certainly be needed, assuming there were an empty lane for a vehicle to move into. A lane-change would in the best circumstances move the vehicle to safety in half the distance as braking at that speed.
The paper does not provide an immediately practicable controller, but simple open-loop approximation of the optimal controls suggests a route towards future real-time solution.—Matthew Best
Matthew C. Best (2012) Optimisation of high-speed crash avoidance in autonomous vehicles. Int. J. Vehicle Autonomous Systems, vol 10, issue 4, pp 337-354 doi: 10.1504/IJVAS.2012.051269