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| Fig. 1: Advanced Cruise Control Display in a 2013 Audi A8. (Source: Wikimedia Commons) |
Driver-assistance systems are automatic or semi-automatic systems which aid us while driving our vehicles. Many advancements have been made in the field and there are a number of assistance systems available with varying degrees of autonomy. These include Cruise Control and Anti-lock Braking Systems which have been around for decades, as well as Lane Assist Systems, Advanced Cruise Control, Lane Keeping, Autonomous Emergency Braking System and many more. Fig. 1 shows the dash of an Audi A8 with the advanced cruise control system active. These systems have played a crucial role in improving safety in vehicles as well as the quality of driving.
Cruise Control is a control system designed to maintain a constant speed while driving (usually on highways). This relieves the driver of having to constantly adjust the throttle to maintain speed. However, the driver is still expected to reduce speed as needed (when approaching slower vehicles etc). The system is capable of adjusting to bank and grade, and is very useful for long drives, especially on highways. Using cruise control also improves the fuel economy by ~7%. [1]
A step up from traditional cruise control, adaptive cruise control (also referred to as advanced cruise control) is able to detect a vehicle in the same lane in the direction of travel, and adjust the vehicle's speed to match that of the vehicle in front. The car usually uses radar/ultrasonic sensors to sense the lead vehicle and its speed, and maintains a pre-defined following distance behind it. Some systems may use optical (laser/camera) systems for sensing. These advanced systems are a big step towards autonomous vehicle technologies, and can have a huge positive effect on highway safety and traffic flow with widespread and appropriate use.
Lane Assist and Keeping systems are semi-automated systems for the steering system of the vehicle. The Lane Assist system augments the steering input of the driver in order to keep the vehicle in the center of the lane and avoids unintended lane departures. The Lane Keeping system is more advanced and is capable of maintaining the trajectory of the vehicle in a given lane without any input from the driver. Both systems rely on sensors to understand the lane boundaries but use different control systems for implementation. As advanced as these systems may be, they still require the driver to be vigilant at the wheel at all times in case the system is unable to perform the intended operation. They may lose lane information in areas with poorly marked lanes or if there is dirt/snow covering the lane markings.
Anti-Lock Braking Systems have become a standard feature in new vehicles these days. The system ensures that none of the wheels 'lock-up' under heavy braking, and maintain the braking capability of the vehicle. Wheel lock-up increases the stopping distance of the car as the dragging wheel is unable to provide adequate braking force.
AEBS is a purely safety intervention system which steps in and brakes the vehicle automatically if the system foresees an impending collision. The radar/ultrasound and optical sensors of the vehicle are used to determine whether the vehicle is on a collision course; and the system sends brake commands to the wheels to slow the vehicle down. It also uses audio feedback to alert the driver.
© Tushar Goel. The author warrants that the work is the author's own and that Stanford University provided no input other than typesetting and referencing guidelines. The author grants permission to copy, distribute and display this work in unaltered form, with attribution to the author, for noncommercial purposes only. All other rights, including commercial rights, are reserved to the author.
[1] M. Sivak and B. Schoettle, "Eco-Driving: Strategic, Tactical and Operational Decisions of the Driver that Influence Vehicle Fuel Economy," Transp. Policy 22, 96 (2012).
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