Skip to content

Autonomous Braking Algorithm

Jump to bottom
Rishabh Singh edited this page Jan 13, 2019 · 15 revisions

The Automatic Braking Algorithm includes the following Braking Systems

  • Anti-Lock Braking System (ABS) Anti-lock brakes stop the wheels from locking up in a panic braking situation. They sense the motion of each wheel and detect skidding or severe braking. If skidding or massive sudden brake pressure from the driver is detected, the ABS will pump, or pulse, the breaks as needed to prevent the car from skidding out of control. The anti-lock braking system can pump the brakes hundreds of times per second – faster than any human can – which helps the driver maintain control of the car.

  • Emergency Brake Assist (EBA) Designed to add braking power if the driver doesn’t apply enough pressure to the brakes during a panic stop, this system can override the driver entirely and apply full brake force. This alone is not an automatic braking system.

  • Forward Collision Warning (FCW) Forward collision warning (FCW) is a warning system that gives the driver time to take action first and prevent an accident – but it is only a warning system. The computer does not take over and do the braking if the driver does not react in time.

  • Forward Collision Mitigation (FCM) A forward collision mitigation (FCM) system warns the driver and applies the brakes simultaneously. This system should not be confused with forward collision warning (FCW) because FCW does not take any action. What FCM does is apply the vehicle’s brakes as the computer calculates the vehicle’s situation, such as velocity and distance. An FCM is not necessarily designed to fully stop the car in an emergency situation, but reduce , or mitigate, the damaging effects of a collision.

  • Forward Collision Avoidance (FCA) Avoiding a collision completely is what a Forward Collision Avoidance (FCA) system is designed to do. It is the most complex system because the factors that must be considered and calculated to actually avoid a collision are numerous. An FCA uses automatic braking assistance, anti-lock brakes, and even assisted steering in order to achieve its goal, but the reality is you’re probably still going to crash. An FCA, like an FCM or FCW, will help reduce the severity of a crash.

Algorithm :

Using 2D-LiDAR/ RADAR(cheap option)/Stereo camera, distance of the nearest object ahead is calculated. (let's this be = x)

Safe Braking Distance is calculated which includes reaction time factor, min. braking distance and safety factor ( = z)

  • v0 : is the speed of the vehicle at the time Emergency Braking was deployed
  • tr : is the avg. reaction time (taken as 2 sec.)
  • a : is the Retardation due to Maximum Braking Force
  • lamda : is the safety multiplier as Maximum Braking Force will not be used to stop (0.7<lamda<0.9)

If x < z Emergency Braking System is activated

Let's derive the Retardation Rate required to bring the Car to stop: The speed vs distance graph is shown in the graph.

Let's assume a very general function. (So that we can change parameters and train the system to give best result)

(alpha and beta are tuning parameters)

By differentiating this equation w.r.t. x and multiplying v, we get retardation rate :

So, this is the value of retardation, we require to stop the vehicle.

If full brakes are applied, tyres will get locked and hence there is a great possibility of slipping, So, we use the ABS Algorithm, which releases the brake in pulses when the tyres gets locked and keeps the slip ratio near it's peak value to obtain the maximum efficiency.

Clone this wiki locally