According to the US Department of Transportation (DOT), 24% of weather-related vehicle crashes in the US occur on snowy, slushy or icy roads each year. The benefits four-wheel drive (4WD) systems can offer during these conditions have long been recognised, which primarily relate to increased traction. Now, new all-wheel drive (AWD) systems have evolved to provide even greater safety benefits.
Torque vectoring allows varying levels of power to be sent to individual wheels on a vehicle, and is an attractive technology for OEMs seeking to build increasingly safe and efficient vehicles. “As the car becomes more intelligent, being able to sense the road and alter the torque as needed, where needed, is the most interesting aspect,” explains Swamy Kotagiri, Chief Technical Officer at Magna International. He points out that although 4WD systems permanently send power to all four wheels, there are occasions where this additional traction is not required. As a result, the drivetrain saps engine power and reduces efficiency. “However, if AWD can be used only in conditions where it is needed, without the parasitic losses when it’s not needed, it makes a case for itself,” he adds.
Brimley is situated at the very northern point of Michigan’s upper peninsula. In February, temperatures of minus 14 degrees Celsius are regarded as ‘moderate’ by locals, and with thick snow and icy road conditions, it is the perfect setting for AWD systems to be pushed to the limit. A Continental-owned test facility in the area is home to an assortment of tracks, surfaces and slopes designed to hone the development of new vehicles, systems and components. Attending the facility is an invitation-only affair, but it is occasionally open for use by its peers. Taking full advantage of this, Magna frequently tests its AWD systems here and is keen to point out the key role these systems play in improving winter safety.
Megatrends joined Magna on a test day and gained firsthand experience inside the gated facility, where several vehicles fitted with a selection of Magna’s AWD systems were being put through their paces: the Cadillac CT6, Kia Sportage and GMC Canyon. Speaking to Megatrends trackside, John Zalewski, Global Product Manager, Driveline at Magna International, explained that having “two additional wheels to provide traction provides better manoeuvrability and control. With that, you can improve handling based on how torque is controlled to those two wheels.” He added that these systems help to “accentuate the safety of a vehicle by maintaining traction on the road’s surface through managing torque and getting the vehicle back to normal in the event of slipping or sliding.”
One of the key benefits an AWD system offers is the ability to help a vehicle counter a slide, something that many drivers on the road will be unable to do effectively on their own. Hitting a patch of ice or manoeuvring along a snow-covered road could result in a loss of traction, and thus control, through oversteer or understeer.
Generally speaking, OEMs favour understeer in this situation as it is easier to recover from, a senior mechanical technician within Magna’s Vehicle Verification group, explained. “Oversteer is a far quicker event, and is much harder to recover from for a normal driver,” he said. “We can help to eliminate oversteer by sending more torque to the front axle, detect the speeds of each wheel and steering angle inputs, and adjust the torque to the front or rear to try to make the best of the situation for the driver.”
In essence, these systems can start boosting power to the front or rear wheels to neutralise a slide and keep the vehicle’s intended path, explained John Zalewski, Global Product Manager at Magna Powertrain. “The other thing is that because there is additional traction, vehicles can get up and over obstacles, whether that be a snow or ice covered hill, a slippery gravel road, or a patch of thick mud. This automatically gives the driver confidence and improved safety,” he observed. What’s more, because AWD helps to maintain the vehicle’s intended driving path, there is less steering input by the driver. “Every time the driver has less input, it is a safer driving condition for them,” said Zalewski. “If they have to control too much by themselves they may overcorrect during a slide. They may then have to re-correct and accidentally overdo it, and that’s where they can get into a spin. Opposite lock is not the desire here, it’s about preventing an accident in the first place.”
Zalewski pointed to Magna’s preventative torque application, which can automatically transfer power from the engine to a wheel – or wheels – in around 300 milliseconds. As a result, “Everything is set up for what is occurring at that moment in time; that’s the whole point of having electronics in the vehicle, so you can think ahead of what’s going to happen and prevent any unsafe conditions and being out of control,” he said.
The automotive industry has been progressing toward an increasingly active approach to safety. The focus is no longer on simply protecting drivers during and after an incident on the road; technologies are being developed that intend to prevent a crash from happening in the first place. “That’s where advanced driver assistance systems (ADAS) are coming into the car,” said Zalewski. “In the future, the drivetrain might be interacting with this area more. Sometimes we can only infer traction conditions of the road surface, whereas, if we can actually see what the road surface is with camera sensors – be it snow or ice for example – we can adjust accordingly instead of waiting for a reaction coming from the tyre.” In future, he suggested, ADAS sensors will be able to provide the drivetrain system with information it can utilise in order to programme the optimum drivetrain setting before the vehicle begins to lose grip on the road. This will be particularly important with the onset of autonomous driving, he added.
In the future then, AWD systems may be able to work in tandem with autonomous driving systems, but when it comes to winter testing, “This still requires a lot of research,” said Chris Van Dan Elzen, Global Product Director of Driver Assistance Systems at Magna. “Driving in an autonomous car is going to be very much like how you and I drive our cars today. We take in the information that is available, and make decisions and risks based on that information. As our level of available data goes down, we may not choose to drive in that environment, or we choose to keep going and change our driving habits accordingly to offset those risks.”
In the case of a complete ‘white out’ during heavy snowfall, “The autonomous car is either going to decide not to drive in this environment, or evaluate how much data can be lost and still operate,” he added. Where the effectiveness of on-board camera, infrared and radar sensors can be adversely affected by a snow blizzard, systems like intelligent and predictive AWD are likely to play a greater role in keeping drivers safe.
This article appeared in the Q1 2016 issue of Automotive Megatrends Magazine. Follow this link to download the full issue.
