TNOs project manager Margriet van Schijndel-de Nooij

TNO's project manager Margriet van Schijndel-de Nooij

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Protecting the pedestrian has been talked about for some time yet cyclist safety appears to have only recently been given the attention it deserves. For its part, Dutch firm TNO is developing an external airbag to protect pedestrians and cyclists in the event of a collision. The researchers used simulations, combined with real world accident data, to study the precise areas of the car a cyclist is most likely to come into contact with.  Continuing just-auto's series of interviews with companies pushing back the technical boundaries in the active and passive safety arena, Matthew Beecham talked with TNO's project manager Margriet van Schijndel-de Nooij to find out more.

Could we start by talking about your windshield airbag system that aims to protect cyclists and pedestrians. What is it?

The SaveCAP windshield airbag is a U-shaped airbag that covers the most critical areas of the windshield area in case of an impact with a cyclist or a pedestrian. So it covers the lower part of the windscreen and the A-pillars, both very stiff areas where majority of the severe head impacts of cyclists and pedestrians are found.

What does it do and how does it work?

The full SaveCAP airbag system consists of two major parts. First part is the sensor part. With stereo vision camera's located near the rear view mirror, the area in front of the vehicle is "checked" for the vicinity and approach of cyclists and pedestrians. At the same time, contact sensors in the bumper can feel any impact with an object. When this object was already classified as cyclist or pedestrian, the sensor system triggers the airbag. This is the second part of the full system; a large airbag covering the exterior of the windshield in a U-shape. In deploying the airbag, two actuators are used to push the bonnet upwards. Thus, the airbag gets enough space to unfold, with additional benefit that for the cyclist or pedestrian, the impact with his upper body onto the bonnet is less severe. The airbag can only be triggered when the car is actually driving.

How is it different from other pedestrian airbags?

There currently is only one pedestrian airbag on the market, available on the Volvo V40. This airbag is designed for the protection of pedestrians; the SaveCAP airbag intends to protect both pedestrians and cyclists. The practical differences can be found in the detailed shape and filling of the airbag itself, and in the sensor system. Only the SaveCAP sensor system was designed to truly detect both groups in time. Now that is done, we feel like with a minimum of efforts, optimised protection can be offered to both cyclists and pedestrians. As the number of cyclists worldwide is increasing, solutions like this are essential.

Could you talk us through how you used computer simulation techniques to develop the windshield airbag?

We used computer simulations for two purposes. We used the simulations, combined with real world accident data, to find out more details of accidents between passenger cars and cyclists, while varying the vehicle type, size of the cyclist, bicycle model, impact angles, impact speeds... thus gaining a lot of information on, for example, the head impact location and injury severity as well as potential life savings and protection from severe injury offered by the airbag or by automated emergency braking.

We also used the simulations to find out more on the kinematics of the cyclist when impacted by the car, giving us directions on the necessary stand-up time of the airbag, the airbag design (shape and size) and the area around the vehicle that should be covered by the sensor system. These simulations were also combined with volunteer testing regarding the potential scenarios during the last seconds prior to impact, as well as laboratory crash testing with a dummy. The laboratory crash testing was a major help in designing the details of the airbag shape including stabilisation areas. Crash testing was performed in many cases with only a head form, but also with a full dummy, standing or riding a bike. Within the SaveCAP project, these tests were performed both at TNO and Autoliv, the latter doing also the detailed design of the airbag and delivering a series of prototypes for testing. 

Could we turn to your advanced automatic braking system. As we understand it, in addition to the airbag, your sensor can also be used for automatic braking and other innovations. How does it work?

It uses the sensor system as described above, of course without the contact sensors in the bumper. When the cyclist or pedestrian comes into a critical area (depending on the car's speed), the braking system is triggered. The exact braking pattern is to be defined by car manufacturers who will implement the system in their cars. The system should only brake when absolutely necessary; else it won't be acceptable for the car driver.

What did you discover during your field tests and how did this help the system's development?

In our field test, we discovered some very typical near-impact scenarios between passenger cars and cyclists or pedestrians. Some of the incidents found were really, really very close encounters; too early for the airbag to be triggered, but automatic braking would have been very helpful already.

This helped us to define a set of typical scenarios that need to be covered by the sensor system, including the timing and distances between the potential impact partners. It taught us more the actual behaviour and movement of cyclists and pedestrians when being really near to a passenger car. We could not have learned this from simulation or laboratory testing, as the actual behaviour of the cyclist or pedestrian is unpredictable.

What stage are both technologies at in terms of market readiness?

SaveCAP has delivered the Proof of Concept, now it is the task of car manufacturers to take it further and to do the development for specified vehicle models, together with system suppliers.

The remainder of this interview is available on just-auto's QUBE research service

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