From the development of algorithms that help driverless cars behave in a more human like manner to advances in the sensing systems that will enable tomorrow’s vehicles to understand and respond to their environment, progress towards the fully autonomous vehicle - where the technology has removed the need for any driver controls - is well under way.
But whilst recent years have seen key advances in the underpinning technologies that will make so-called level five autonomy a reality, until now there has been relatively little attention paid to the structural engineering challenges presented by a technology area that could profoundly impact the way that cars are designed and built.
Steel E-Motive, a project involving UK engineering consultancy Ricardo and led by WorldAutoSteel (the automotive arm of the World Steel Association) is aiming to address this through the development of a virtual concept vehicle that demonstrates the role that advanced steels could play in delivering on the promise of these next generation vehicles.
WorldAutoSteel technical director George Coates explained that the programme arose from a study carried out by the association that identified the rise of autonomy, the insatiable demand for greater levels of efficiency, and the expected shift to mobility as a service, as key areas of opportunity for the global steel industry.
The new architectures associated with mobility as a service vehicle are going to be tailored perfectly for steel’s attributes
George Coates - World AutoSteel
It quickly became apparent, he said, that thanks to continuing advances in both strength and formability, steel - for decades the material of choice for automotive body structures - is the best placed material to help carmakers respond to these trends.
“You would have thought we’d get to a point where we’re mature, but the industry just keeps reinventing,” said Coates, “we’ve been able to double percent elongation [a measure of formability] whilst taking strength levels to 1200 megapascals (MPa)! We never would have thought we could have done that 10 years ago, and there’s more on the horizon.”
He added that these ongoing advances in strength and performance, mean that steel is particularly well suited to meeting some of the challenging structural engineering requirements that will be presented by a new generation of vehicles. “You have to be able to meet the crash requirements and you have to have the ability to form the material into the complex shapes of the components, and steel just continues to enhance both of those critical properties,” he said. “The new architectures associated with mobility as a service vehicle are going to be tailored perfectly for steel’s attributes."
Coates added that advanced steels will also play a key role in improving the carbon footprint of both the vehicle and the processes used to produce it. “As you go to high strength materials you’re using thinner sections which means you’re using less material, plus we’re finding that there are fabrication processes that are really material efficient in terms of how much they use versus how much is scrapped – so less material is needed for each given part.”
Expanding on the details of the Steel E-Motive project, Ricardo chief engineer Neil McGregor said that it will see the development of two variants of a level 5 autonomous vehicle: one for urban applications and another for extra urban trips. The ultimate aim is to produce a 100 percent validated virtual model of the two vehicles. “We’re essentially taking the design right up to the point where you would start committing to tooling,” he said.
Work began on the project in July 2020, with a feasibility study, before the team moved into the main engineering phase in October 2020. “We’re currently developing the design concepts for the vehicle,” said McGregor. “We’re evaluating the different grades of steel that are available, the different fabrication methods, comparing this to the vehicle requirements and trying to map out where is the best use for the steel with this unique vehicle application.”
Whilst Ricardo has a rich history of involvement in full conventional vehicle development this is its first full autonomous vehicle said McGregor, explaining that the project has presented some interesting new challenges for the team, specifically around the way in which the opportunities opened up by level five autonomy affect the structural engineering requirements.
“With level five you essentially take away the driving ability - the steering and the pedal box - and that allows you to position the occupants of the vehicle pretty much where you want,” he said. “The conventional front facing passenger is no longer a requirement and this allows you to do lots of different things with the vehicle packages – and presents some unique challenges that haven’t really been addressed.”
This is quite a game changer, the more we get into it the the more interesting it gets
Neil McGregor - Ricardo
Clearly, passenger safety is the most critical issue here, and McGregor explained that the Ricardo team has been looking closely at issues such as the design implications of having rearward facing passengers, and what this might mean in a crash situation. “We’ve been designing standard passenger cars for years and the design rules are all very well understood,” he said. “This is quite a game changer, the more we get into it the more challenges we find and the more interesting it gets.”
Coates believes that it’s only by getting to grips with these engineering challenges that we’ll move the futuristic dream of level five autonomy closer to reality. “We’ve seen lots of concepts for ride hailing autonomous vehicles, but how many of those have actually been proven or applied against crash standards? We don’t think any. You have shorter front and rear ends to manage crash loads; you’ve got to worry about comfortable vehicle access when you’re thinking about Kerb management. How do you engineer the enclosure to allow that and how do you ensure that all of that is tied in to meet side impact loads whilst also protecting the battery case? We think that all of those things are going to be uniquely solved with some of the cool attributes that the new steels bring to the table.”
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