Have you ever imagined a fully autonomous car in which you are able to sleep while driving? This possibility is nearer than you could expect. Advanced Driver Assistance Systems (ADAS) is a novel research field whose main purpose is the so called “Active Safety”. Some of these technologies which are more likely to attract our attention are: parking aid, Adaptive Cruise Control (ACC) and Lane Keeping Assistance System (LKAS).
During the last decade, the automotive industry has been trying to enhance vehicle safety. It is offering intelligent assistance systems in order to reduce the number of fatal accidents that daily happen around the world. Drowsiness and driver inattention are two of the main causes of accidents. Hence, the majority of those systems improve active safety systems by overlapping driver manoeuvre in case of danger situation. However, and due to the present regulation, active systems are able to take the vehicle control only for a few seconds.
Adaptive Cruise Control (source: Opel)
Last Saturday, I had the opportunity to attend a special motor show organised by McLaren at the MTC (Woking, Surrey). The aim of this event was to collect money for charity purposes and there, not only the legendary Formula 1 cars could be seen, but also super cars and classic vehicles which were exhibited by McLaren employees.
First of all, let me start showing you the M7C, commonly known as the “Thursday car”. This was one of the first vehicles in which the company started studying aerodynamics. As a matter of fact you can see that there are two wings: one at the rear part and another one at the front. The explanation for having these two wings is easy: because of the height of the rear wing, the down force which was generated was so big that the front of the vehicle tended to take off and that gave rise to the need of another wing to combat that effect. The reason why this race automobile is known as the “Thursday car” is that it was introduced on a Thursday free practice in Monaco and it got banned for being too dangerous. Why? Well, basically because the front wing could act as a “guillotine” if an accident occurred.
I’ve noticed that a lot of people try to avoid using the four wheels of the car when they go over a speed bump. Out of curiosity, I asked some of those drivers and all of them gave me the exact same answer: “Because if you only hit the obstacle with the wheels of one side of the car, you will cause less damage to the vehicle and, besides, it is less uncomfortable for occupants”. Is that true? Let’s find out.
Let´s start from the beginning. The first thing we need to know is that cars have two axles (i.e.front and rear) and each of them has two wheels (i.e. right and left). On the other hand, speed bumpers are road obstacles which are designed to make drivers reduce the speed in certain areas and they are usually as wide as the lane. Why is that? Well, basically bumps are thought to be encountered by the two wheels of each axle simultaneously, creating a scenario known as “vertical symmetric load case”. This situation causes results in a bending moment which is applied to the structure of the car.
However, sometimes we can find some bumps which present a smaller width or even gaps. These are the situations where some drivers decide to vary the direction of the car so that the wheels of one of the sides avoid the contact with the obstacle. Therefore, only one wheel goes over the bump. Hence, the vehicle will suffer an “asymmetric vertical load case”. In other words, the automotive structure will be subjected to a torsional load, which is a worse scenario than the one introduced above since it can cause one of the wheels to lift off. I will show you how a relatively simple approach can be used to prove this statement.