24 May 2012

World first pedestrian airbag - standard on Volvo V40

Every year, 1.3 million people are killed on the world's roads where significant percentage comprises of pedestrian. For Volvo, safety has been a key priority for 85 years and in 2008, launched a unique goal in that ‘By 2020, nobody shall be seriously injured or killed in a new Volvo' and to contribute towards the aim, it has fitted technology including Pedestrian Detection, City Safety and the Pedestrian Airbag.

The Pedestrian Airbag technology was a world breakthrough when the all-new Volvo V40 was launched in Geneva earlier this year and will to be fitted as standard to all specifications. The system is active at speeds between 20 and 50 km/h. According to statistics, 75% of all accidents involving pedestrians take place at speed of up to 40 km/h.

Sometimes in early of the new millennium, there has been actually some design guidelines in terms of pedestrian protection. This was when car's hood start become bulbous because there needs to have 75mm minimum clearance between the highest point in the engine compartment and the lowest point of hood inner structure. Yours truly in 2005 was looking into designing the then-axed major Waja facelift, and at that time the packaging of Campro engine within the newly design hood for Waja facelift was quite a concern as the Campro engine can't be lowered any further in the chassis. However, since the project was killed sometimes after that, the whole exercise becomes academic.

At that time, the seventh generation Honda Civic was the benchmark, especially the short-hood Euro version. There's virtually "soft" padded panels everywhere in the hood, fender inner, bumper beam and even the headlight has a sliding mechanism within the bracket to reduce the force exerted on the pedestrian. More details after the jump. 

Meanwhile over the years, Volvo has seriously looked into the details, minute analysis on the mechanism that trigger the injury to the pedestrian upon each accident. They have concluded that the most serious head injuries involving pedestrians and cars are caused by the hard structure under the bonnet, the windscreen's lower edge and the A-pillars.  These were the main areas that Volvo looked at when starting development of its Pedestrian Airbag Technology.

Seven sensors embedded in the front of the car transmit signals to a control unit. When the car comes into contact with an object, the signals change. The control unit evaluates the signals and if it registers what it interprets as a human leg the pedestrian airbag is deployed.

The bonnet hinges are each equipped with pyrotechnic release mechanisms which, when the system is activated, pull out a pin and release the rear of the bonnet panel. At the same time, the airbag (consisting of a sack and a gas hybrid generator) is activated and starts filling with gas, which only takes a few milliseconds. During the inflation sequence the airbag raises the bonnet by 10 centimetres and stays in the raised position.

The added gap between the bonnet and the hard components in the engine compartment gives space for the bonnet to deform, creating a dampening effect when it is hit by a pedestrian. In its inflated position, the airbag covers the entire windscreen wiper recess, about one-third of the windscreen and the lower part of the A-pillars. The entire sequence from activation of the system to full inflation takes a few hundredths of a second.

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