Archive for January, 2005
Posted on 26. Jan, 2005 by Ryan.
Photo Credits: Saab Automobile
Seeking Safety in the Danger Zone: How Saab Automobile AB Applied the Lessons of Real-life in Designing the Saab 9-3 and 9-5
Saab Automobile AB, the Swedish premium car maker, enjoys an industry-leading reputation in the field of crash safety. Here, Per Lenhoff, Saab Automobile AB’s Head of Crash Safety Development, describes the thinking behind the company’s approach in designing and developing the Saab 9-3 and 9-5 models.
â€œWe never forget that we are protecting real people, not just dummies in a laboratory,â€ says Per Lenhoff as he explains how the team at Saab Automobile ABâ€™s (Saab’s) Crash Safety Center are primarily concerned with what actually happens on the road under real-life conditions when it is a person, instead of a dummy, who is behind the wheel or in the passenger seat. Unlike a standard laboratory crash test, each road accident is a unique event because of the almost limitless number of variations in the speed and the point, angle or type of impact.
The fact that the Saab 9-3 and 9-5 are frequently placed at the top of major consumer crash tests published in Europe and the US, as well as Swedish and US surveys of road accident injury claims, demonstrates the effectiveness of their work.
In designing these models, Saab, almost literally, tried to cover all the angles by studying the outcome of thousands of accidents involving Saab cars on Swedish roads. This work led, for example, to the use of front and rear crumple zones. These parts of the vehicle are designed to deform in a controlled manner under varying points or angles of impact.
Saab’s real-life safety philosophy is also demonstrated by the effectiveness of the 9-3â€™s and 9-5â€™s ‘pendulum’ B-pillar design in handling side impact forces. And it also inspired the development of the Saab Active Head Restraint (SAHR), an industry first in helping to prevent neck injury following a rear-end impact.
Real-life experience also forms the basis of the crash simulation and testing work carried out by the Safety Center team at Saab’s technical development center in TrollhÃ¤ttan, Sweden. In designing the Saab 9-3 and 9-5, they performed many tough tests based on common, real-life crashes that did not figure in consumer crash tests.
Learning and applying the lessons of real-life involved three main areas of activity: accident investigations, crash simulation and crash testing. Each team responsible for the design of a structural safety element or an in-car restraint system was composed of colleagues working in these areas. In this way, real-life knowledge was shared as widely as possible and embedded in the whole process of safety engineering.
Saab’s interest in safety goes right back to the company’s roots as an aircraft manufacturer. It is routine practice to ensure the safety of test pilots and their aircraft by investigating accidents, so it was instinctive for engineers in the fledging Saab car division to do likewise. In fact, records show the first road accident investigation involving a Saab car was carried out before commercial production had even begun.
Today, the database at the Saab Safety Center holds details of about 6,100 real-life accidents on Swedish roads involving cars like the Saab 9-3 and 9-5, and the previous Saab 900 and 9000 models. Information can relate to the extent of occupant injury, as well as the performance of structures and safety restraints. â€œWe are not interested in apportioning blame or finding out who was at fault,â€ explains Lenhoff. â€œIn designing the 9-3 and the 9-5, we focused purely on examining how the car’s safety systems performed in helping to prevent injury so that we could increase our knowledge and understanding.â€
The safety team at Saab works closely with Swedish insurance companies, who usually notify them of about 50 accidents a week. The majority of these cases involve relatively minor incidents but about one or two cases per week are followed up by a full investigation. This involves reference to police reports of the circumstances, a detailed examination of the vehicle and usually a subsequent visit to the accident scene. Where appropriate, occupants may be interviewed and the team also uses the services of two medical experts, specializing in trauma and orthopedics, to assist in analyzing injuries.
â€œIt is rather like fitting a puzzle together,â€ says Lenhoff. â€œWhen we have assembled all the data, we try to find out exactly how injuries were caused and how the car safety systems functioned.â€
Advances in CAD (Computer Aided Design) and Finite Element Method (FEM) make it possible to create extremely sophisticated and accurate ‘virtual’ crashes. Numerous simulations are carried out at the Saab Crash Safety Center every year, each one requiring massive computing capacity. The work is now so complex that a real-life collision, which is over in a split second, may take the computer 12 or even 24 hours to reproduce. These simulations were used in the design of the 9-3 and 9-5.
In designing the 9-3 and 9-5, the crash safety team liaised closely with their colleagues in design and structural engineering, working with X-ray images that are often composed of 1.2 million tiny cells, each covering details of the models and their components, including the virtual dummies. The data was so detailed, and the calculations so sophisticated, that laboratory testing proves that simulations can now function with 90-95 per cent accuracy.
These virtual crashes allow the safety team to enact and analyze more impacts, more quickly and more efficiently than they can through physical testing alone. Crash simulations are used primarily in product development, allowing engineers and designers to test, for example, the effectiveness and compatibility of features or systems well before prototypes are built.
â€œThis is an area of our work which has developed a great deal over the last 10 years and will continue to become more sophisticated,â€ says Lenhoff. â€œWe have been able to explore the limits through simulation, finding out how deformation structures or restraint systems work in precise detail.
Although Lenhoff and his team can often anticipate the results of a crash test even before it is conducted, the sheer scale of their testing work is impressive. During the development of the latest Saab 9-3 product range, the structural design of the car and the deployment of its occupant protection systems were evaluated in a large number of in-house configurations, taking occupants of different sizes into consideration, as well as consumer and legally required crash tests.
Apart from using sleds with barriers and poles in the laboratory to replicate collisions with other vehicles and fixed objects, moving car-to-car, and even car-to-truck, impacts were staged in the development of the 9-3 and 9-5. These were severe examinations of crashworthiness that went beyond the demands of any statutory or consumer crash test standard. But, like all the other tests, they were based on what actually happened in real-life, irrespective of whether the authorities deemed them necessary.
To satisfy the requirements of real-life, simulation work and crash testing was used to help design metal joints in the 9-3 and 9-5 that would be resistant to tearing, as well as body structures that are designed to deform in a controlled and predictable way under varying conditions. As a result, the front structures of the Saab 9-3 and Saab 9-5 incorporate three interconnected load paths, behind a broad front beam, designed to help absorb and dissipate some of the crash energy. Inside the passenger cell, the car’s interior restraint systems – seatbelts and airbags – function effectively in helping to reduce potential injury, irrespective of an occupant’s age, size or seating location.
Even in side impacts, where there is limited scope for a deformation ‘buffer’, crash testing has helped in the development of a B-pillar (the central post between the doors) that acts as a protective ‘pendulum’. This is designed to bend inwards at the bottom, deflecting forces down towards the floor and away from the passenger compartment.
â€œFrom real-life we also know that people are human and will not necessarily do what is best.â€ adds Lenhoff. â€œThat’s why we have also put a lot of effort into having quite a persistent automatic warning system inside the 9-3 and 9-5, if the front occupants are not using their seatbelts. And we have in-car safety advice cards, similar to those found in passenger aircraft, to encourage occupants to use such things as seatbelts, head restraints or child seats properly.
â€œAt the end of the day, people must use the roads responsibly and do everything possible to avoid getting involved in a crash. But, for whatever reason, if they do become involved in a crash, our job is to help minimize the consequences. Winning awards is recognition of our work, but it is not why we do it.â€
Note to Editors:
In addition to Saab motor vehicles designed and manufactured by Saab Automobile AB, certain Saab models are designed and manufactured elsewhere in the world in consultation with the design and safety engineers of Saab Automobile AB.
Posted on 02. Jan, 2005 by Ryan.
Photo Credits: Saab Automobile
Saab 9-5 Aero BioPower Concept: Sportier Performance and More Environmental Care
The Saab 9-5 Aero BioPower concept demonstrates that Saab drivers can enjoy the benefits of increased power and performance while having a greater regard for the environment. In combining the enjoyment of sporty driving with innovative and rewarding technology, it builds on Saab’s strong Scandinavian tradition of providing ‘performance with responsibility’.
Powered by bio-ethanol (E85), a renewable and sustainable fuel, the 2.3-liter turbocharged engine of the 9-5 Aero SportCombi show car delivers almost 20 per cent more maximum power (310 v 260 bhp) and 25 per cent more torque (440 Nm/325 lb.ft v 350 Nm/258 lb.ft) than its gasoline equivalent. On the road, this is expected to translate to zero to 60 mph acceleration in under 6 seconds, compared to 6.9 seconds with gasoline. This is all achieved alongside a dramatic improvement in environmental performance, through reduced emissions of fossil carbon dioxide (CO2), the ‘greenhouse’ gas that is widely believed to contribute to global warming.
Saab already leads the European premium car segment in offering a BioPower model. Sales began on the Swedish market last year (2005), where the Saab 9-5 2.0t BioPower’s winning combination of enhanced engine and environmental performance – its power is raised from 150 to 180 bhp when running on E85 – currently accounts for 70 per cent of all 9-5 sales. The same model also recently attracted Popular Science magazineâ€™s Best of Whatâ€™s New award, an annual selection of 100 breakthrough new products and technologies.
Now BioPower technology is being applied for the first time to Saab’s top-of-the-line 9-5 Aero model, showcasing the potential of developing a version for the North American market.
Ethanol fuel is produced commercially from agricultural crops or forest residues and is already produced in the US Mid-West region from corn. Unlike gasoline, its consumption does not raise atmospheric levels of carbon dioxide (CO2). This is because emissions during driving are balanced by the amount of CO2 that is removed from the atmosphere, through natural photosynthesis, when crops for conversion are grown. To ensure good cold starting performance, ethanol is usually blended (85% ethanol/15% gasoline) and sold commercially as E85 fuel.
E85 is a high quality fuel with a much higher octane rating (104 RON) than gasoline, allowing the engine’s ignition timing to be advanced for more power without risk of harmful ‘knocking’. The adaptability of Saab’s powerful Trionic engine management system has facilitated re-programming to accommodate its different ignition and fuel/air mixture requirements. The only hardware modifications necessary for BioPower are more durable valves and valve seats, and the use of ethanol-compatible materials in the fuel system, including the tank, pump, lines and connectors.
Trionic monitors fuel quality after every visit to the filling station and automatically makes any adjustments necessary for running on E85 and/or gasoline in any combination. That means Saab BioPower drivers can also use gasoline, should E85 not be available.
During the development of BioPower, Swedish engineers liaised with their General Motors colleagues in Brazil where 100 per cent ethanol (E100), produced locally from sugar cane, is the dominant fuel on the market. Saab has found that turbocharged engines are particularly well suited to exploiting the benefits of ethanol, allowing the possibility of introducing higher compression ratios for optimum power and efficiency, while also encouraging powertrain downsizing.
“We are delighted to be taking a lead in the development of BioPower, which expresses many of the traditional values of the Saab brand, ” says Jan-Ã…ke Jonsson, Saab Automobile’s managing director. “We are convinced alcohol fuels like ethanol can provide an effective short to mid-term solution in our search for sustainable alternatives to fossil-based fuels for road transport.
“It is compatible with conventional gasoline engines and can be supplied through the existing fuel infrastructure, without the need for any major new investment. A transition towards ethanol can run in parallel with the development of other, longer-term energy solutions, which could also include ethanol as an energy-carrier for the introduction of fuel-cell technology.”
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