Continuing just-auto’s series of interviews with major suppliers of occupant restraint systems, Matthew Beecham talked with Dirk Schultz, global engineering director, Inflatable Restraint Systems, TRW Inc and Alfonso Bustos, product lead engineer, passenger airbag technologies, TRW Inc.

In terms of the evolution of the vehicle occupant restraint market, how would you sum up the position we are currently at? 

If we look back over the last 20-30 years, we have come from a situation where there were a very high number of deaths as a result of road accidents and it was clear that there was an urgent need for safety improvements in cars. This spurred the development and application of a number of technologies, including airbags and seatbelts.  Since then, the life saving potential of airbags has become increasingly clear and it is widely accepted that, to date, airbags have saved thousands of lives around the world and prevented serious injuries to many times that number of people.

Today, airbags and seatbelts are standard equipment on most vehicles and we have seen a significant improvement in road safety but there is of course the potential to do more. We are entering the next chapter of occupant restraints which focuses more on individual safety for different occupants or crash configurations – and therefore optimising occupant protection even further.

Legislation and various NCAP organisations are also playing a key role as vehicle manufacturers selling into Europe and North America and parts of the Asia-Pacific region are looking to achieve top safety results, such as ‘five star’ or at least ‘four star’ ratings.

During the last decade, the terms ‘advanced’, ‘adaptive’ and ‘smart’ airbag have often been used interchangeably.  Although today’s generation of airbag systems are technically more advanced than earlier designs, to what extent are they ‘smart’, i.e. perform in different ways in different circumstances?

Smart airbags can be adjusted to different occupant conditions as well as different crash conditions. For example, we can provide a different restraint performance for the belted or unbelted occupant; we can provide softer or stiffer bags depending on occupant size, or offer different airbag geometries – smaller of larger bags depending on occupant position. Also, airbags can be equipped with features which can further reduce the risk during deployment in out-of-position situations of the occupant such as deploying the airbag more softly if it senses that someone is sitting very close to the airbag centre of deployment.

When we refer to smart, we also mean clever concepts and how to find synergies between the technologies which can help to make airbags more affordable and therefore accessible to the widest range of consumers. 

We hear a lot about the term ‘integrated safety’ and understand it to refer to how active safety and passive safety are seen as less and less distinct from one another. Is that correct and what does it mean for TRW?

There is certainly a greater link today between active and passive safety than there has ever been. TRW produces the widest range of safety relevant components and this is a huge benefit as we have the knowledge and experience to integrate several systems – enabled by electronics – which other companies are simply not able to.

A good example of how TRW is integrating active and passive safety systems is the combination of its Automatic Emergency Braking (AEB) system with its Active Control Retractor (ACR) seatbelt technology. This can reinforce driver warning; improve occupant position in relation to the vehicle’s airbag restraint system; and provide automatic braking support.

The integrated system utilises a mid range radar in combination with a scalable video camera which independently gather data of the road and traffic situation in front of the host vehicle: the radar looks forward up to 150 metres, while the camera covers a closer, but wider field of view and helps to detect and classify objects in front.

If the sensors detect a critical situation, the driver is alerted to the potential danger (visual, audible or haptic feedback) and the ACR system pretensions the seat belt which can provide an additional warning to the driver as well as remove seat belt slack to help maintain  the position of the occupant prior to  airbag deployment. Furthermore, a certain amount of brake pressure will be applied automatically.

A further example of TRW’s integrated systems is the production Lancia Delta. In this vehicle, TRW supplies Electronic Stability Control (ESC), video based lane keeping assist and Electrically Powered Steering (EPS) systems with steering torque control functionality – the integration of ESC and EPS. In the Lancia Delta, TRW’s sensors, algorithms and electronics provide information that enables the actuation of the most appropriate systems to help deliver enhanced driving comfort and safety. The video camera is integrated with EPS to enable lateral support. It detects when the vehicle is drifting toward the lane markings and the EPS provides the driver with gentle guidance/haptic feedback through the steering wheel to stay in lane.

TRW set up a dedicated electronics division in 2007 – recognising the exponential growth in this area of the industry and enabling the business to focus on products which can enhance the communication between systems. TRW uses the term ‘Cognitive Safety Integration’ to describe how it ‘puts the thinking’ into vehicle safety systems.

Does this ‘integration’ mean more, say, merging airbag electronics with electronic control systems?

TRW’s electronics integration roadmap focuses on an individual integration ‘box’ for data fusion and environmental sensing – which we call a ‘safety domain ECU’, or SDE. Using the open AUTOSAR architecture, the SDE integrates a number of chassis, suspension and DAS control functions and has the processing capacity and flexibility to include software from vehicle manufacturers and third party suppliers.

In terms of electric vehicles, to what extent are passive safety features being fitted?

With all of our technologies we are thinking about future challenges such as electric vehicles and these might have a particular environment which needs to be investigated. This could include crash pulses which might differ, deployment time for airbags which may differ or special characteristics with seatbelts. For example, if you have a very rigid crash pulse because your vehicle is small, you would need a faster airbag deployment time or special characteristics for load limiters.

A second important point is that we are addressing supporting technologies by reducing the weight – this is a key factor to make electric vehicles more attractive as the weight of the vehicle is directly proportional to its performance. We have already successfully developed airbag applications for electric vehicles – the side and curtain airbags of the Chevy Volt in North America are one example and further application developments are ongoing.

I guess side protection airbags pose special challenges in terms of the time in which they must deploy.  How have you addressed that and could you talk us through a product example?

New side airbag systems achieve excellent deployment times to reach their final position and the results of our latest airbag products underline this. Deployment speeds for side airbags is very important and several factors can contribute to this such as the bag design, folding of the bag or the inflator characteristics. TRW’s SPI2 EVO side airbag inflator is an example of a proven technology which offers a reduced weight and packaging design with quick deployment times.

We are particularly interested in TRW’s ‘bag in roof’ concept and have a few questions to ask about this technology. What is it?

TRW’s roof airbag is a frontal passenger airbag integrated into the roof area of the vehicle and consists of a bag, an inflator and module housing.

What does it do and how does it work?

The airbag deploys from the sun visor area. The head liner bends during deployment so that the airbag can exit and the bag deploys downwards and parallel to the windscreen and is positioned in front of the occupant. 

Why is it useful?

The roof airbag offers a number of benefits:

  • It can help to increases styling flexibility for future instrument panels (IPs) as it can make room for further features such as multimedia electronics or storage.
  • There is no occupant interaction with opening IP doors so therefore reduces the risk of impact if an occupant is out of position.
  • By deploying parallel to the windscreen and not against the windscreen, the loads on the screen are reduced. This is an important point as windscreens are becoming weaker with each vehicle generation as vehicle makers strive to save weight.
  • The roof airbag can reduce the risk of injuring the occupant in out of position situations. For example, if they are leaning forward, a conventional IP airbag would be closer to the occupant!
  • Cost savings can be realised as the roof airbag is independent from the IP. Often, the IP surfaces of different car versions are made up of a different material (leather, non leather, hard and soft surfaces etc.) and the integration of the passenger airbag within each panel needs to be validated. This process can therefore be eliminated – saving time and money.
  • Timing of the development is also important factor. With an IP – we can start representative airbag product validations when the real IP is available off tool and these are huge tools which are typically not available in the early stages of development. Being independent of the IP means we can test and validate our bag in roof airbag application even earlier.

What does it replace?

The roof airbag replaces a conventional airbag in the instrument panel and therefore opens the door for advanced vehicle styling.

What does it threaten?

This technology is applicable for a major portion of the market – however there will be some limitations for certain vehicles such as sporty cars with a very flat windscreen angle or a low roof, or convertibles. In these cases we would need to more closely evaluate the vehicle and assess the packaging options.