Advances

Driving Automotive Safety

The science of safety
Steering:
Belt drive provides precision and feel

Airbag inflators:
R&D successes lead to light, compact designs

The leading edge:
• Compact vision sensor • Integrated sensors for ESC • Load-limiting seat belt • Tire pressure breakthrough

2010

Issue 31

Point of view

Suppliers are key to an innovative future
Guest editorial by Bill Hampton, publisher, The AutoBeat Group
Last year the global auto industry experienced its worst upheaval ever. Now it is more than halfway through a ‘recovery’ year that is generating impressive profits for many companies – and almost none for others. Even successful suppliers are being very careful this year because they don’t know if the global economy is truly recovering or not. No employer wants to go through the trauma of budget and personnel cutbacks again. Most are hanging onto cash, being prudent about expansion and trying to guess what will happen next. It isn’t easy. Economists and analysts increasingly agree we can expect volatile swings in the industry through the remainder of 2010 and perhaps longer, depending on the specific geographic market. Some say today’s tumultuous industry represents a new norm in business conditions. Their advice: hone your coping skills and get ready for an era of hyperchange. How can companies thrive under these uncertain conditions? In a word: innovation. Demand for effective new technologies has never been higher and the industry’s extraordinary focus on innovation these days is one of the few business constants in the automotive world. This The leading edge ........................................................................................................................... 18
A selection of the latest technologies emerging from TRW research & development centers around the world

In this issue
Algorithms at the heart of crash sensing advances ................................................................. 4
Dr Anson Foo

Belt drive gives steering precision and feel .............................................................................. 8
Alastair McQueen

Safety-critical ESC is scalable and flexible ............................................................................ 12
Thomas Straub

Materials advances lighten airbag inflators ............................................................................ 15
Johann Vetter

interest is driven by extreme competitive pressures, ever more demanding customers and the urgent need for the industry to address fundamental sustainability questions regarding air quality and energy sources. None of these issues will be solved with old answers. It takes innovation – and the companies that deliver it are almost guaranteed to excel. Good ideas must be commercially practical, of course. As anyone in the automotive sector knows, that means they must be cost-effective. Price has always been the gatekeeper for innovation; and

In brief.............................................................................................................................................. 20 Advances is published twice yearly for TRW Automotive customers and other external audiences. Please submit ideas for articles and inquiries to:
Lynette Jackson, communications director, +44 121 506 5315 [email protected] John Wilkerson, senior communications manager, +1 734 855 3864 [email protected] Roger Bishop, editor
This publication may include statements about our expectations for the future. These expectations are subject to numerous assumptions, risks and uncertainties, including those set forth in our most recent Form 10-K and Form 10-Q filed with the US Securities & Exchange Commission. We do not undertake any obligation to publicly release any update or revision to any of the forward-looking statements.

Quill Communications Inc, graphic design and layout

ADVANCES 2010 Issue 31 Page 2

it always will be. But the pricing equation is a moving target. Consider the influence of emerging vehicle markets. These increasingly important regions are full of buyers who demand world-class technology, but at a lower price than the rest of the world pays. At the same time, the acceptable price of innovation is rising significantly in mature markets. This is partly because car manufacturers want technology that can help differentiate their products. It’s also because regulatory pressure is forcing them to consider technological solutions that would have been dismissed as too expensive only a few years ago. These trends are pushing the global auto industry into a new era of closer and more productive collaboration similar to the links pioneered between Japanese car makers and their suppliers. This shift is most obvious in North America today where a traditionally adversarial business style is finally giving way to a more cooperative philosophy. It will be a gradual and dynamic process, but car makers recognize that their long-term viability depends on rethinking their relationship with the supply chain.

A decade ago, America’s domestic car manufacturers shifted responsibility for many key technologies to suppliers. Then they pulled those programs back in-house as they reasserted their desire for control. Now they appear to be searching for a middle ground that protects their core competencies, yet taps the speed and innovation that comes by inviting suppliers into the product development cycle earlier and more deeply. Regardless of where that balance point is, suppliers with high-value technology will be in great demand – and they will be able to command a good price for their knowledge and expertise. All of this is occurring against a backdrop of the true globalization of the auto industry. Vehicle manufacturers have done business on an international scale since the beginning of the auto industry, but for decades this meant managing a collection of relatively autonomous local operations set up to serve local markets. The benefit of localized products remains. The difference today is that car makers are becoming dramatically more proficient at developing truly global car platforms from

which to create these vehicles. Given the cost savings that result, they have strong reason to continue this trend, which is generating very large-scale opportunities for suppliers that also operate globally. Last year’s global financial crisis was difficult on everyone and the effect is far from over. Out of the industry’s turmoil has come a return to the sound business practices that companies know they should have been following all along. Coupling this sensible approach with an unwavering focus on product innovation is the best formula for success, no matter how uncertain the business climate.

For more information Bill Hampton +1 248 540 2530 [email protected]
Biography Bill Hampton has written about the auto industry for 39 years and is a former Detroit bureau chief for Business Week magazine. He founded the AutoBeat Group ten years ago - its four automotive-related publications can be found online at: http://autobeatgroup.com.

ADVANCES 2010 Issue 31 Page 3

Abstract Legislative pressures in Europe, North America and Asia, alongside the desire by all vehicle manufacturers (VMs) to protect occupants and other road users, are driving developments in future generations of vehicle safety systems. TRW Automotive is using its expertise in algorithm development to combine active and passive technology with electronics and sensing capabilities – to create intelligent systems that enhance the safety of drivers, passengers and pedestrians.

Algorithms at the heart of crash sensing advances
Computer modeling has a key role in the development of in-car safety technologies The integration of crash sensing with other safety and driver assistance technologies is driving future generations of cost-effective passive safety systems in cars. Advances in environmental sensing mean that data about the environment around the vehicle is fused with data from the crash sensors within the vehicle for improved performance. Radar, lidar, ultrasonic or video sensors work to anticipate what could happen from the information they draw from around the vehicle and then the accelerometers or pressure sensors provide another level of confirmation in order that the actuation of the advanced safety systems is optimized. This could be in terms of changing the position of the occupants; improving time to fire; or adapting the protection system in line with the crash type. At the center of the crash sensing activity are advances in algorithms that control these tasks. Most recently, techniques have been developed at TRW that allow frontal-rear impact systems to be designed using singlepoint sensing architecture, eliminating the now common up-front satellite sensors mounted on side members, radiator supports and elsewhere in the engine compartment. The first vehicles to use this technology are being developed for markets outside North America. These and other developments are underpinning TRW’s passive safety systems algorithm roadmap covering: frontal-rear impact sensing; side impact sensing; rollover sensing; and pedestrian impact sensing. They relate to making appropriate, robust and timely deployments of occupant restraint or protection devices to safeguard vehicle occupants and, in one sector, pedestrians. In the frontal-rear impact area, the V-Sensor_8 family of algorithms for model year (MY) 2011 vehicles provides third generation enhanced asymmetric impact sensing without the use of additional up-front satellite sensors. Nevertheless, it resolves accelerations in the ‘traditional’ frequency band of < 400 Hz, the ‘acoustic’ band of 500 Hz to 20 kHz, and at A-pillar, B-pillar and C-pillars along vehicle x and/

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Crush zone sensors

Two-wire DSI bus

Occupant sensing system

Side airbag

Side impact sensor

Seat belt pretensioners

Seat belt buckle sensors

Front airbags (multi-stage inflators)

Central electronics control module

Side airbag

Side impact sensor

Seat belt pretensioners

Algorithms ensure that crash and environment sensors communicate effectively with each other and a vehicle’s major safety systems or y axes. Achieving single point sensing of this complexity, while retaining the original sensing performance and same NCAP ratings, posed a major technical challenge to crash sensing algorithm design – in particular how to utilize only the accelerations measured by the onboard accelerometers in the safety electronic control unit (ECU) located in the passenger compartment. Looking further ahead, frontalrear impact systems for MY 2012 will see enhanced sensing performance and robustness by linking with inertial sensing (IS), vision and radar sensors, as well as electronic stability control (ESC) and adaptive cruise control (ACC) systems. In addition, there will be enhanced asymmetric and pole impact sensing through the use of dual-axis sensors in the front end. These advanced levels of integration will enable car safety systems to anticipate critically dangerous situations so that, for example, seat belt pretensioning systems like TRW’s Active Control Retractor (ACR) can be initiated and airbag initiators prepared for firing. Airbag deployment – confirmed by signals from pressure sensors and accelerometers in the event of a crash – will therefore be faster. active safety technologies such as IS sensors and ESC. For MY2012 and beyond these will be linked with vision, radar and ACC systems to provide a third generation solution, followed by more formal integration to further enhance performance and robustness. TRW’s pedestrian sensing technology is now based on the X-RISA_8 family of algorithms, measuring deflection and impact frequency. For MY2013 there will be a highly significant advance – links with IS, vision and radar sensors will enable pedestrian sensing systems effectively to ‘see’ and positively identify pedestrians in a potential zone of danger and react accordingly. To appreciate fully the scale of the research and development activity behind these achievements, it is useful to have a picture of the team involved in this exacting work at TRW; the techniques used; and the evolution of the algorithms being designed.

Impact tests
Currently, (MY2011) TRW’s E-SIDEe_8 family of side impact sensing algorithms provide third generation sensing performance and robustness to meet oblique side-pole and high speed movable deformable barrier (MDB) test standards using satellite sensors mounted in door cavities, door sills, B-pillar and C-pillar. For MY2012 these will be linked with IS, vision and radar sensors along with ESC and ACC systems. For MY2013 these features will be more closely integrated. The second generation of TRW’s rollover sensing algorithms – the RDA_8 family – already work in association with

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The very first TRW crash sensing algorithm – the first generation TRW frontal impact sensing algorithm VEAM – was designed in the early 1990s at the former TRW Space and Defense site in southern California (now part of Northrop Grumman). VEAM was an immediate success, largely due to the design and adaptation of a unique non-time based algorithm framework. The sensing performance of non-time based algorithms has been proven in the field, over the past 15 years, to be robust and reliable. Since 2005, some TRW competitors in Germany and Korea have been using a similar approach. In the early 1990s, developing a crash sensing algorithm required more than ten engineer-years. Now it takes about two engineer-years, despite today’s solutions being exponentially more sophisticated and complex. This is achieved through accumulated crash data libraries; crash dynamics and occupant kinematics knowledge; the availability of model-based algorithm/software development tools; and much improved system verification and validation infrastructures. Accumulation of knowledge in crash dynamics and occupant kinematics has been achieved collectively by VMs, restraint system manufacturers and crash sensing system suppliers. The VMs, in particular, have achieved massive advances in crash testing and data collection along with acquiring new knowledge of structure design and behavior. In parallel, restraint system suppliers have used extensive Forward-looking sensors allow airbag and seat belt systems to prepare for heavy braking or an impact TRW’s global algorithm development & applications group (ADAG) was founded in 1994 growing from an initial staff of five to more than 50 engineers with advanced degrees (masters or PhD) and of 15 nationalities. With its headquarters in Farmington Hills, Michigan, there are ADAG locations in China, Germany, Italy, Japan, Korea and Poland. math modeling and simulation to achieve a greater understanding of occupant kinematics and the deployment of restraint systems and airbag inflation. Designing an early crash sensing algorithm would involve engineers manually deriving algorithm logics (limited to linear logic) and software programmers implementing those algorithm logics in

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low-level programming language. In the mid 1990s, TRW global ADAG began utilizing offthe-shelf algorithm design and development tools (Maple V, Matlab, Simulink and later Stateflow and TargetLink). With these tools, algorithm logic design and analysis was no longer limited to linear logic but included some non-linear logic – all implemented in an automatically-generated high-level programming language such as C/C++. This resulted in much better system design; more extensively analyzed and simulated crash sensing algorithms; and enhanced implementation within microprocessors.

and Driver Assist Systems (DAS) – to enhance the overall safety of the occupant in the context of reducing the crash severity and occupant injuries. This will happen in two ways: first, through the integration of ECUs such as the crash sensing ECU and inertial sensing ECU (part of the ESC System); and second, through sharing sensor outputs via the CANbus or other communications protocols. TRW’s algorithm development program has been highly successful in recent years, but the actual implementation and realization of all that is possible will depend on the readiness of vehicle manufacturers to integrate crash sensing technologies with other systems.

Development trends
In the 1990s, validating, or verifying, the implementation of an algorithm in a microprocessor was a labor intensive activity and system coverage of the process was also narrow. Late in the decade the introduction of hardware-in-the-loop techniques at TRW global ADAG made possible the highly efficient verification of much more sophisticated and complex crash sensing algorithms. TRW’s return in 2009 to single-point architecture for its frontal impact sensing algorithm (for applications in Europe and emerging regions) demonstrates the highly innovative thinking that takes place within ADAG. Eliminating the upfront satellite sensors while maintaining sensing performance and NCAP ratings poses a major technical challenge – in particular, how to utilize only the accelerations measured by the onboard accelerometers in the ECU. Industry wide, major approaches include using dual-axis acceleration, expanding the frequency range of the acceleration signal (up to as high as 20 kHz) and the use of vehicle speed information. The other major trend is the linking, or integration, of crash sensing with other vehicle systems – in particular ESC systems

For more information Dr Anson Foo [email protected] +1 248 699 4817

ADVANCES 2010 Issu ADVANCES 2010 Issue 31 Page 7 VANC sue Page

Abstract The steering system plays an important role in defining a vehicle’s character, as it represents a continuously operated interface between man and machine. For car manufacturers, the vehicle response to steering inputs and the feedback from the vehicle and road to the driver is one of the most significant ride and handling attributes and performance differentiators. At the turn of the millennium, the challenge for suppliers of electric power steering (EPS) technologies was to match, and then exceed, the ‘feel’ of hydraulic systems. Now there are generations of drivers who have only experienced EPS.

Belt drive gives steering precision and feel
Market drivers in the automotive industry for fuel economy, emissions reduction and vehicle safety are well understood by vehicle manufacturers (VMs). Consumers, too, are becoming more conscious of how their vehicle buying decisions will impact the environment. Car manufacturers have responded by introducing new drivetrains, safety systems and power-saving technologies elsewhere on their vehicles including – importantly – the steering system. However, the VMs have not forgotten that there is a human being in the car who has a tactile connection to the road via the steering wheel. Safety, driving comfort and even the passion for driving are all affected by how well a vehicle responds to steering commands. In high profile promotions, luxury car manufacturers including BMW, Mercedes-Benz and Audi, have exalted the ‘man-machine interface’ and the ‘driver experience’ delivered through premium steering technologies and refined engineering. These solutions have usually come with a high price tag but this does not now exclude them from the mainstream vehicle market. Nor does it

A typical Belt Drive EPS steering system showing the all-important belt-driven motor unit

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mean that premium steering feel excludes environmental benefits. Electrically powered hydraulic steering (EPHS) has been available as an alternative to fully hydraulic systems since the mid-1990s and offers significant energy savings compared with a conventional beltdriven hydraulic pump. The technology is well suited to larger cars, hybrids (providing steering assist when the internal combustion engine is off) and light commercial vehicles with their heavier steering rack loads. However, for greater energy savings and for the added features it can offer, fully electric power steering (EPS) is the solution now chosen by most VMs. EPS systems provide assist via a servomotor mounted either on the steering column or the steering rack. For the steering rack designs, the servomotor can transmit power into the rack in one of three ways: a single or dual pinion gear set; via a ball nut with a concentric motor approach (motor wrapped around the rack bar); or a belt drive to a parallel mounted motor. It is this latest design – the highly efficient Belt Drive EPS – that is attracting the attention of both premium and mainstream car makers. TRW supplies both Column Drive and Belt Drive EPS to the market. TRW’s Belt Drive EPS has been launched on Ford mainstream vehicles and SUVs – the Milan/Fusion, Taurus/MKS/Flex/MKT, Focus 2010 and Escape 2011.

Brushless AC motor technology Friction compensation solutions to offset the

‘stickiness’ around the ‘on center’ position.

At the heart of the system is a compact, low weight AC servomotor capable of operating on the highest rack loads

it to be compact and low weight while being capable of operating on rack loads up to 15 KN (actual rack load capability is dependant on handwheel speed, “c” factor which is the distance the rack travels in one revolution of the handwheel). The technology requires the use of a rotor position sensor and, depending on the customer configuration requirements, can include torque sensing with single turn angle sensing or absolute angle sensing. The motor is operated via six field-effect transistor (FET) ‘switches’, under software control to produce a smooth three-phase sinusoidal current waveform. This produces an exceptionally quiet, low torque ripple response that contributes to the natural and notch-free steering feel. The integrated ECU is mounted alongside the motor on the rack. Overall the Belt Drive EPS exceeds the mechanical efficiency of dual pinion designs by 10 to 15 percent. This is due to the high efficiency of the belt and ball nut mechanism and the absence of any requirement to pre-load gear sets, resulting in precise, responsive, steering feel with no

disadvantage of high friction on alternative rack-mounted EPS systems – dual pinion designs, for example – typically result in a slightly artificial steering feel. Wear is also reduced because fewer components are under load – a major contributor to steering feel variation over time.

Packaging flexibility
As technologies move forward, Belt Drive EPS solutions are being made available in smaller and more flexible packages, helping to satisfy customer requirements. The higher static rack load capability of ball nut mechanisms compared with single and dual pinion rack drive systems can be readily scaled to cover C, D, E, SUVs and light truck segments. With its adoption in the market place and resulting economies of scale, costs have come down, making the technology price competitive for adoption on mainstream vehicles. Belt Drive EPS is extremely efficient compared with the rack and pinion hydraulic pump, using energy only when the driver demands it. With no direct energy draw

Reduced inertia
At the heart of TRW’s Belt Drive EPS are a brushless motor, toothed belt, and a low friction ball nut assembly with the pulley and bearing integrated into a single unit. This setup results in lower inertia and friction for high power applications, as well as a more direct steering feel and superior response. The AC servomotor has a very high magnetic flux density thanks to the rare earth magnets fitted to the rotor. This allows

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on the engine, Belt Drive EPS systems offer a fuel saving of up to 0.4 liter/100 km, with a corresponding reduction in carbon dioxide emissions of approximately 8 g/km compared with hydraulic power steering. Reacting to market demands for higher vehicle safety levels and driver comfort, TRW has developed advanced features that can be added to Belt Drive EPS. These fall into two functional categories – safety and driver assist. Safety functions are those that can detect and react to hazardous conditions, like slippery or icy road surfaces and torque feedback that infers a driver’s drowsiness or inattention. When coupled with sensors, surrounding or approaching vehicles can be detected, enabling the system to warn drivers of dangerous conditions. Emergency

functions allow the EPS to perform corrective maneuvers to avoid collisions. Lane guidance, lane keeping assistance and emergency steering assist are examples.

Assist functions
The electric steering system plays an important role for driver assist functions, as it can help drivers in unpleasant, but necessary, steering tasks; guide or coach drivers to quicker, more precise steering inputs; and observe the driver’s operating habits through the hands-on detection interface. For example, using specially developed algorithms, the EPS can detect and compensate for roads with high camber or crowning. The system can also detect cross wind conditions which normally require drivers to make frequent steering

The unit, with its integrated ECU and position sensor, provides highly flexible packing options as well as low inertia and friction

Toothed belt

Ball screw nut with toothed pulley and bearing

Rack/ball screw

AC motor Motor position sensor Toothed pulley, motor side

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corrections. EPS automatically calculates wind effects and inputs the right amount of steering correction to keep the vehicle on line, relieving drivers of a tiresome duty. Torque steer compensation – correcting the tendency in some front-wheel-drive vehicles to pull to one side under the influence of engine torque – is another capability. When linked to proximity sensors, EPS can ‘automate’ the sometimes challenging task of parallel parking. Sensor information, along with algorithms, are used to calculate the best parking trajectory and EPS provides the assistance to steer the vehicle. Drivers using this function for the first time are surprised by how accurately it parks a vehicle, even in the smallest spaces. No driver input is required in this ‘hands free’ style of semi-automatic parking, which places a higher assist demand on the EPS system. Belt Drive EPS is well suited for handling strenuous parking cycles on larger vehicles and is another performance advantage Belt Drive has over dual pinion. As there is no driver input with automatic parking, the full parking load must be provided by the EPS system. At TRW Automotive, enhancing driver experience is a key priority when developing new technologies. The company’s advances in the areas of steering and braking have provided innovative solutions which mirror the ‘traditional’ vehicle response, reassuring drivers that they are still in control, while offering considerable environmental and cost saving benefits. TRW’s Electrically Powered Steering (EPS) and Electrically Powered Hydraulic Steering (EPHS) technologies are prime examples. At the core of TRW’s efforts to replicate traditional feel in steering is the relationship the driver has with the vehicle and, ultimately, the degree of confidence that a driver has in that vehicle’s ability to respond in a potentially dangerous situation. Alastair McQueen, global engineering director for EPS at TRW Automotive, explained: “Maintaining a natural steering feel for the driver is a primary goal during the development of an EPS system. The specific hardware set-up and software ‘tuning’ of the steering system within the individual vehicle environment plays a critical role in achieving this.” According to McQueen, TRW’s approach to steering feel revolves around three core principles: • Attention to the sources of steering feel “distortion” in the core design such as reflected inertia, mechanical compliance and friction; • The deployment of robust closed-loop control approaches, using time and frequency domain analysis in the design, development and Stringent testing during research and development ensures that high quality, reliable, systems are delivered to customers

Driven to maintain driver experience

Mainstream solutions
Looking forward, TRW predicts further adoption of Belt Drive EPS technology for non-premium mainstream vehicle platforms as the technology of choice thanks to its performance, price and packaging advantages over other rack drive steering technologies. TRW intends to be a leader in Belt Drive EPS technology offering further packaging options, performance enhancements, wider scalability and integration with other vehicle systems for enhanced safety, driver comforts and vehicle stability.

implementation of the algorithms determining the torque delivery of the system. This is instead of static, ‘if-then-else’ or ‘fuzzy logic’ type rule-bases which can ultimately lead to an artificial steering feel; and • Close collaboration with the vehicle manufacturer (VM). He added: “TRW needs to be involved, as an active development partner, from the very start of the project. By using TRW’s sophisticated tuning and dynamic analysis tools our dedicated international vehicle dynamics teams help customers form a union between chassis components and the steering system to realize an optimized steering feel.”

For more information Alastair McQueen [email protected] + 44 121 627 3970

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Safety-critical ESC is scalable and flexible
Abstract Electronic stability control has proven itself to be a key active safety technology for its ability to help drivers during unstable driving maneuvers and for the cost benefits accruing from integration with other systems such as steering and driver assist. Offering a full product range for all cars, light commercial vehicles and high performance models, as well as powertrains ranging from internal combustion engines to full electric vehicles, is a challenge met by TRW’s EBC 460 ESC products. Here we focus on the functionality offered by this family’s ESC and ESC Premium variants. Now mandated in both North America and Europe for light vehicles, electronic stability control (ESC) has been called the “greatest automotive safety innovation since the seat belt” by former US NHTSA administrator Nicole Nason. While vehicle miles driven continue to increase and more cars are on the road than ever before, motor vehicle accident statistics and fatalities in Europe and North America continue to decrease in part thanks to safety advances like ESC. Bringing the advantages of ESC to other regions and accelerating the installation rate in the mass vehicle markets is a priority. TRW has continued to look for ways to make ESC more affordable for all vehicles while also pushing the technology boundaries for premium segment vehicles. During the winter development season of 2009/2010 TRW was able to demonstrate a scalable solution from ABS to ESC and ESC Premium to support vehicle manufacturers across their platform requirements. Although Europe and North America implemented ESC legislation, Asia Pacific and South America are seeing increased installation rates of ABS and ESC, but have not yet taken the step to legislate for ESC. TRW’s EBC 460 product family features everything from basic units – some even developed to remove the pressure sensor (ESC L) to lower cost without compromising performance – through to premium units with six-piston pumps that can rapidly build and apply brake pressure for driver assist functionality, such as emergency braking.
Half-sleeved pump 480W motor

Slip control systems (SCS) are the result of the integration of several components such as hydraulics, electronics and software. Since the product covers a wide range of functionality, the configuration matrix of components is quite large. For this generation of products, a key goal for TRW’s development engineers was to reduce the amount of system variants and deliver a higher degree of standardization compared with previous generations. This will leverage volume scale effects, increase component re-use and reduce application cost to the customer.

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The 460 family concept is primarily based on a modular approach with the aim of sharing the maximum number of parts across the different system architectures. The EBC 460 family has three main product architectures – ABS, ESC and ESC Premium – each with distinctly different packaging sizes, but sharing components for standardization purposes. Within the architecture the product can be configured to suit the vehicle manufacturer’s braking, vehicle sizing and functionality requirements. Many functional upgrades are achieved via software that can be scaled up with different microprocessor sizes. In the early stage of development, design rules were established to support efforts to standardize the product portfolio and engage a structured method to limit the variants developed and manage their content. The content of this system is structured as ‘a standard configuration’ with ‘upgrade components’ for increased functionality.

The optimization of all components, systems capabilities and required functions has been considered in the creation of EBC 460. The ESC electro-hydraulic control unit’s (EHCU) mass and volume have been further reduced resulting in weight reduction and improved packaging characteristics. The unit weighs only 1.8 kg compared with the EBC 450 at 2.4 kg – an impressive 24 percent reduction – with volume reduced by 20 percent.

Data communication can be supported using a standard control area network (CAN) or the recently developed faster and deterministic communication interface known as FlexRay. Other enhancements integrated into product configurations include: up to six valve drives with analog current control; long life pump; high frequency motor control (20 kHz) yielding increased motor life and reduced noise, vibration and harshness (NVH); an upgrade to three pressure sensors for increased comfort and enhanced support of driver assist systems (DAS); a noise attenuation chamber for increased comfort levels when used with DAS; customer-specific input/output (I/O) architecture on request; and FlexRay interface to vehicle networks. The EBC 460 product family offers, as a standard software features set, anti-lock braking (ABS), traction control (TC) and ESC along with cornering brake control and electronic brake force distribution (which eliminates the need for valves to balance brake forces between the front and rear brakes). A myriad of software and hardware upgrade features can be added to the standard system including: hydraulic brake assist; hill descent control; trailer stability control; tire inflation monitoring; active rollover management; and driver assist deceleration for systems like adaptive cruise control (ACC). Extending the functionalities of conventional slip control systems, the

Robust control
The system has a dual core microprocessor that complies with the latest standards for automotive safety control systems. It features a TRW designed applicationspecific integrated circuit (ASIC) that enables robust control and failure mode handling. It is compatible with the latest wheel speed interface for intelligent sensors for VDA (European standards) and pulse width modulation (PWM) protocols.

3 pressure transducers Analog TC ISO valve

Analog ABS ISO valve

Digital dump valve Digital supply valve Low pressure accumulator

design target for the Electronic Stability Control Premium (ESC P) was to achieve the highest possible pressure-applied dynamics

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ESC Standard
• • • • • 8/12 valves 2-piston pump 1 pressure sensor Motor 330 W Scalable micros: 700 kB – 1.4 MB (memory)

ESC Premium
• • • • • 12 valves 6-piston pump 3 pressure sensors (optional) Motor 480 W Scalable micros: 1.4 MB – 3 MB (memory)


Basic functions: • ABS/TC/ESC, CBC, EBD Function upgrades: • Hydraulic brake assist • Brake disc clean • Hill assist • Pre-fill • Hydraulic brake boost (HBB) • Adaptive cruise control • Active rollover mitigation • Hill descent control • Electronically controlled deceleration • Trailer stability control Same as standard, plus: • Driver assist functionality • Enhanced pressure apply dynamic • Automatic emergency braking • City safe • Crash mitigation • Brake warning jerk • Low vacuum support functionalities • Lowest pedal pulsation & noise • HBB – enhanced boost pressure for very low vacuum • Failed boost support

The ‘boxer design’ of the EBC 460. The pump piston arrangement is shown in three planes with its short suction channels with improved pedal comfort and NVH – setting the standard for the capabilities of future driver assist technologies. ESC P enables advanced safety technologies including collision mitigation braking at city speeds all the way through to automatic emergency braking, where the application of full brake pressure is enabled to help avoid (or mitigate the impact of) an accident. The six-piston pump provides for extremely low pedal pulsation and noise levels during active control operation. In addition, the system offers: improved and extended functionality including analog pressure control; increased pressure apply dynamics for DAS functions; and the options of emergency braking operation or brake warning jerk. Other capabilities include reduced pedal pulsation and acoustics, better durability and sufficient hydraulic boost capacity to operate in very low vacuum conditions.

Software functionality

Hardware

The system also incorporates an electronically controlled deceleration interface, which allows for autonomous pressure build-up for ACC maneuvers, resulting in smooth deceleration demands up to 0.3 G for emergency braking, with full pump pressure applied, of up to 1 G. Follow to Stop or Stop and Go, down to 0 kph, are also supported.

requirements established for failed booster conditions. TRW works vigorously to ensure proper safety cases for ‘decoupled’ brake systems that are not directly connected to the driver through the typical brake pedal, booster and master cylinder configuration. It can be seen that while ESC has been a well-developed technology for some years, the scope for adding further capabilities has been expanded by the parallel development of driver intervention and driver assist systems. Nor is the pace of development likely to slow as TRW assists its customers in meeting legislative and competitive pressures which demand that the vehicles we drive in the future be safer for both their occupants and other road users.

Reduced vacuum
With modern fuel-efficient engines, the resulting reduction in engine vacuum availability has to be managed. The TRW technology includes a vacuum adjustment that allows hydraulic brake boost functionality even with reduced vacuum availability, or under temporary very low vacuum conditions. In case of total vacuum failure, the hydraulic system takes over to support brake pressure via the ESC system. This provides the driver with sufficient brake pressure to stop the vehicle within the legal

For more information Thomas Straub +49 261 895 2700 [email protected]

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Abstract Innovative packaging to reduce vehicle weight is a constant theme within the automotive industry and no component escapes the scrutiny of development engineers. TRW has achieved remarkable success with its disctype inflators, cutting their weight by up to two thirds for those used in driver’s side airbag modules. These gains – earned through the use of new propellant formulations, high grade materials for housings and advanced welding technology – are especially important now as mainstream vehicle manufacturers begin to turn their R&D resource towards cars with electric powertrains.

Materials advances lighten inflators
Airbag inflators are among the unrecognized heroes of car technology. These complex components – highly engineered combinations of chemical, mechanical, electrical and materials science – sit unused inside steering wheels, instrument panels, B-pillars and seats, usually for years, Yet at crucial moments they need to work perfectly in response to signals from a vehicle’s onboard crash sensors. Despite their safety-critical role in vehicles, inflators are no less exempt from the pressures of size, weight and cost reduction than any other automotive system. And the rapid development of alternative powertrains, including plug-in electric vehicles, is making tough demands on the designers of these frontline safety components. TRW has made extraordinary progress with its DI10 family of inflators, usually applied to driver’s side applications but, these days, in demand for use within compact modules used elsewhere in the passenger compartment. The main thrusts of development have been weight reduction and modularization with extensive use of common parts, advanced propellant formulations and global thinking in both applications engineering and manufacturing. A disc-type inflator is a simple but highly engineered device comprising a steel housing and diffuser with holes on its periphery; an ignition tube; initiator; filters

DI10 inflator - the main components

ADVANCES 2010 Issue 31 Page 15

(to reduce gas temperatures and prevent hot particles from escaping into the airbag); the propellant; a booster charge; and a filling pack (to prevent in-car vibration breaking down the propellant tablets into powder). By far the heaviest component is the housing which has to be of a strength and thickness to contain operational pressures. It is the modified propellant that allowed TRW to reduce the combustion pressures within the inflator and, therefore, the weight of the housing.

As a result, the weight of single and dual stage DI10.1 and DI10.2 single and dual stage inflators has been massively reduced. In the case of an inflator for a 65 liter airbag (driver side), the weight has been reduced by 53 percent, from 750 g to 350 g, and for a 130 liter bag (passenger side) by 66 percent, from 1500 g to 500 g. The propellant now being used is known as GuNi. It is based on guanidine nitrate but has several proprietary additional chemicals and modifiers that give it the performance that TRW seeks. Changing just 2 or 3 percent of the mixture can alter its behavior. It can be totally different and the exact formulation is the big advantage currently held by TRW. Early DI10.1 inflators used NiGu (nitroguanidine) propellant which is good from a pressure point of view, but has a higher exit temperature – about 1100o K. Engineers in airbag module development were looking for an alternative that would avoid any possibility of stressing the bag material.

Safety margin
The predecessor of the DI10.1 inflator resulted in inflation pressures of some 350 bar. With a required safety margin of 1.7 times greater than 350 bar, this meant that pressures of around 600 bar had to be protected by the material. If the primary pressure could be reduced to around 220 bar then the housing design would only have to resist pressures up to 400 bar. This would bring down the pressure by a third, allowing for the reduction of the thickness of the steel housing correspondingly. It was an important factor in enabling TRW development engineers to reduce the weight of its inflators.

Temperature issues
GuNi propellants seemed to be the best choice. However, in formulating these there is a trade-off between combustion temperature and the amount of gas released. For example, GuNi 80 releases 80 percent of its weight as gas but is described as being ‘hotter.’ This type of propellant is therefore mainly used within hybrid inflators – gas-filled bottles where the pyrotechnic device is used to open the bottle. GuNi 65 burns more coolly but

Inflator strategy technology by region

Europe North America
DI10.2 production starts in 2012 DI10.1 & DI10.2 manufacture underway in Aschau

Asia Pacific
DI10.1 production starts in 2011

releases only 65 percent gas. The best compromise for TRW turned out to be formulations based on GuNi 75. TRW’s product, based on GuNi 75 is called GuNi LP (low pressure). The aim of the modification was not to reduce the temperature, but to bring down the combustion pressure. The product has an

ADVANCES 2010 Issue 31 Page 16

TRW’s modular concept allows great commonality of parts between DI10.1 inflators different heights: 40 mm, 50 mm and 60 mm

DI10.1X46

DI10.1X56

DI10.1X66

Standard flanges allow a wide range of mounting options further adding to the flexibility of DI10.1 and DI10.2 inflators

Equal for all inflator heights

Only used for height 40 mm

Equal for all inflator heights

Different sizes of DI10.1 inflators use many common parts, as shown here. The same is true for DI10.2 inflators. In addition, different flange designs provide a wide choice of mounting options for car manufacturers

exit temperature of around 850o K and burns at 150 to 200 bar. This is the new propellant TRW has had in serial production for the last 18 months. Laser welding in an inert gas atmosphere has also been introduced to ensure that carbon steel inflator casings are completely leak-free. The technique allows 360 welding and precise measurement and control of the energy put into the weld. The unit will therefore withstand the environmental conditions in a car over its lifetime. Paving the way for TRW’s global approach to disc type inflator manufacture are standardized products, based on a modular design, and the development of construction kits of parts that can be ‘locally’ assembled. Currently, DI10.1 inflators are manufactured in Aschau where a 120 strong research and development team is centered. Low volume manufacture of the DI10.2 started there in August this year. A joint venture is being established in China, where production of the DI10.1 will start early next year. And the North American operation in Mesa, Arizona, will begin producing the DI10.2 inflator in 2012. The use of common parts for the DI10.1 and DI10.2 covering inflator heights
o

– or sizes – of 40, 50 and 60 mm yields impressive advantages.

bag sizes on both the driver and passenger sides of the vehicle. Many of the parts are interchangeable and there are several mounting flange options, including one that allows the attachment of a vibration damper, if required. TRW believes that the concept of the DI10 family fully meets the future demands of the global market in terms of weight, package size, quality and cost. The design philosophy appears to have been endorsed by customers who report that the adaptability of the modules was a principal reason for choosing the product.

Modular approach
For DI10.1 between 50 and 70 percent of parts are common to the different versions; for DI10.2 around 50 percent of parts are common to both 40 mm and 60 mm height types; and for DI10.1 and DI10.2, some 20 to 30 percent of parts are shared. The modular approach is allowing TRW to deliver inflators offering the same levels of quality and performance for all global customers while also meeting the requirements of national standards such as FMVSS 208, EuroNCAP, C-NCAP, JapanNCAP. Construction kits are based on a standardized diameter of 63 mm covering multiple applications requiring different

For more information Johann Vetter [email protected] +49 8638 965 1473

DI10.2 size and performance range
Weight.......................................................................................................................... 350 - 550 g Diameter ...........................................................................................................................Ø63 mm Height ........................................................................................................................... 40 - 60 mm Gas output ................................................................................................................. 0.8 - 2.6 mol Exit temperature ............................................................................................................... ~850 oK Performance ...........................................................................................................130 - 500 kPa Bag size ..........................................................................................................................45 - 130 L Split.......................................................................................................................... 70/30 to 60/40

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The leading edge
Compact vision sensor makes life easier for drivers
An advanced camera and sensor unit, mounted near the rear view mirror, brings high levels of functionality to vehicles in a package no larger than a deck of playing cards. “Giving a vehicle the capability of seeing the road, the environment and the lighting conditions under which a driver is operating can be incredibly powerful,” said Dr Alois Seewald, director, integrated active and passive safety technologies. The package is small and lightweight, yet includes the processing power needed to support several functions. Beyond automatic on-off headlamp control, the camera technology also determines in low light conditions whether other traffic is in the vicinity and, if not, automatically switches headlights to high beam for better vision at night or in tunnels. In addition, an integrated optical rain sensor focuses on the windshield glass surface, measuring reflected light. Light reflection changes as rain or snow falls on the windshield and the system automatically engages the wipers, varying their speed in line with the changing levels of moisture detected. A humidity sensor can also be included. This monitors humidity in the vehicle interior and activates the blower motor within the HVAC system to keep the windshield defogged. Other functions that could be supported by the camera-sensor unit include lane departure warning and lane keeping systems, traffic signal recognition and automatic emergency braking. “With so many distractions commanding the attention of today’s driver, the automation of functions like these can help to keep greater attention on the road ahead,” said Seewald.

Integrated sensors simplify ESC
TRW is driving down costs for vehicle manufacturers by integrating inertial sensors into both its electronic stability control (ESC) systems and airbag control units (ACUs). The Lancia Delta has become the first car to use TRW’s ESC system with an integrated inertial measurement unit (IMU), to perform previously discrete sensor data acquisition directly within the ESC electronics module. And in 2014 MY, an integrated ACUIMU will be launched on a Toyota model. Traditionally ESC systems have been introduced with a stand-alone IMU. Integrating it directly into the ESC reduces the full system cost, weight and wiring harness complexity without sacrificing performance. The design also provides a scalable solution for vehicle manufacturers wishing to offer both ABS and ESC braking systems within a model range. The IMU integrations for both ESCs and ACUs are based on common sensor development and are available to meet various vehicle architectures and platform requirements. With ESC mandates in place in North America and Europe, TRW’s strategy includes further sensor integration at the silicon level to offer additional cost, performance and reliability advantages. Josef Pickenhahn, vice president, TRW braking engineering, said: “These technologies are a part of our ongoing efforts to integrate sensors and controllers with the dual goal of increasing performance while lowering costs. Integrating the IMU is the first step toward combining a variety of chassis and occupant safety control functions that will offer weight and packaging advantages and enhanced data sampling rates – enabling a variety of active and passive systems to act together to improve vehicle safety. “We are pleased to launch this advanced, integrated ESC system with the Fiat Group. As an electronics safety systems specialist, TRW is relentlessly pursuing higher levels of safety and performance.”

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TPMS and keyless entry get together
At first glance there is little connection between remote keyless entry (RKE) and a tire pressure monitoring system (TPMS) but a production contract between TRW and a major Asian car maker will combine the technologies, tuning, nor will there be any discernible change to the RKE key fob layout or performance. The transmitted commands will be received by a single smart receiver/ ECU that will process information from the RKE fobs and also the temperature and pressure signals sent from the transmitters located in the TPMS sensor units in individual tires. The integrated ECU will decode the signal to activate the lock/unlock function for vehicle doors and the trunk and provide tire pressure warning information to the driver in the same way as conventional RKE and TPMS receivers. The integrated system is anticipated to launch in 2012 for a 2013 Model Year vehicle.

Load-limiting seat belt adjusts to occupant size
A new seat belt load limiting technology that automatically adapts to the different body sizes of passengers is now in production on the Mercedes E Class. The Self Adapting Load Limiting seat belt (SALL) has been designed to meet the needs of rear seat occupants and operates without the need for sensors. Conventional load limiters are not optimized for the full range of passenger weights, but by definition must make compromises to cover the full range of passenger weights. Traditional systems compensate for this by providing two different load limiting settings but these require the use of expensive weight sensors in the vehicle. TRW’s SALL system adjusts the force level according to the amount of webbing an occupant pulls out when they are buckled up. This enables the system to classify occupants into two categories so that in a crash situation, a lower load level is triggered for a smaller passenger and a higher load level for a larger passenger. Harald Lutz, TRW’s engineering director, seat belt systems, says: “While conventional load limiting technology has a positive impact on reducing injuries in car accidents, it still shows some limitations in its standardized approach. The new self-adaptive technology recognizes that not every passenger conforms to the same height and weight group. It is a cost effective solution which can make a significant difference.”

resulting in significant efficiencies. “The integration of RKE and TPMS is an example of TRW’s drive toward enhancing value and performance through electronics integration,” says Martin Thoone, vice president, TRW electronics engineering. “This system simplifies the electronics architecture by eliminating the need for separate receivers for each system. We can maintain the performance characteristics while using less space and reducing system weight and wiring complexity, leading to lower material and assembly costs.” Highly sensitive super-heterodyne receivers will be used. They require no

ADVANCES 2010 Issue 31 Page 19

Driving Automotive Safety

In brief
Buckling up in China
As a contribution to efforts to reduce the high number of fatalities in road accidents in the region, TRW launched its Buckle Up campaign on China’s National Children’s Day in June. The campaign teaches children key road safety messages using a range of interactive tools including a seat belt demonstrator; fairytale audio CD and booklet; and cartoon-style bunny characters. The program targets kindergarten children. TRW has developed several technologies that are directly relevant to the new tests which will take into account the 5th percentile passenger occupant in addition to the 50th percentile driver. One example is TRW’s dual volume or dual depth airbag, which operates via a tether activation unit (TAU) and is able to deploy according to the size and belted condition of the occupant. Ford Motor Company World Excellence awards have been won by TRW’s Dacice plant in the Czech Republic for its outstanding performance in the supply of engine valves and the United Kingdom’s Resolven factory for the durability and reliability of its steering systems. Toyota’s Excellent Value Improvement Award recognizes suppliers who exceed the company’s expectations and was specific to TRW’s electronics business with Toyota in North America (TEMA). PSA’s award was for TRW’s work on Value Analysis and Value Engineering of airbags during 2009.

Safety JV in China
TRW has entered into a joint venture with Xi’an Dong Fang Group Co Ltd, a division of China North Industries Group Corporation, to set up a facility to manufacture airbag inflators and seat belt pretensioners. Production is expected to start before the end of the year. TRW

Ready for US NCAP
Advances in occupant restraint simulation techniques are supporting vehicle manufacturers as they prepare for more stringent US New Car Assessment Program (NCAP) safety criteria for 2011 model year vehicles. Simulations can deliver significant cost reductions compared with traditional testing processes. Changes to the US NCAP star rating include: a replacement test dummy for the passenger side and additional injury criteria that cover the four body regions (head, neck, chest and femurs) for the frontal crash test modes; the addition of a new side pole test, new test dummies and new method of injury criteria evaluation for the side impact test program; roll-over rating; an overall summary rating; and a new program to promote advanced technology solutions and crash avoidance technologies.

also has plans to expand the product range to include side and curtain airbag inflators next year. Dong Fang Group is among the leading 500 machinery companies in China and the top 30 in Shanxi Province. The move expands TRW’s manufacturing footprint of advanced occupant safety into Northwest China. TRW’s established production bases in Shanghai have long been helping its Chinese partners raise the bar of driver and passenger safety, introducing technologies that also improve vehicle intelligence and fuel efficiency.

Support for eSafety
This year’s eSafety Challenge to promote the life-saving potential of advanced vehicle safety technologies took place at the UK’s Millbrook Proving Ground. Widely regarded as an obstacle to the adoption of eSafety systems by motorists, is a lack of awareness among both policymakers and end users. This also affects policy support, user expectations and readiness for change. Key eSafety applications highlighted by the eSafety Challenge were: electronic stability control (ESC); blind spot monitoring; lane support systems; speed alert; warning and emergency braking systems; and adaptive headlights. Estimates for ESC alone show that in Europe it could save 4,000 lives and prevent more than 100,000 injuries if fitted to all cars. This year, there was a special focus on fleets.

Supplier awards
TRW Automotive’s trophy cabinet has been opened once again to receive awards from three global car makers – Ford, Toyota and Peugeot Citroën (PSA).

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