What will powertrains look like in a driverless future?

Fleets of self-driving vehicles are coming to the world’s roads. Whether it’s in Phoenix, Arizona, where electric taxis glide to and from their Waymo depot to recharge, or on the streets of the UK following a government decision to bring forward trials, the future is now inevitable.

Waymo provides a vision of what could be around the corner. The firm says its US-based fleet provided 4 million driverless rides last year, cutting 6 million kilograms of carbon dioxide from the air. It was able to achieve this by working its vehicles at a rate humans could never match. 

The company’s vehicles spend up to 20 hours a day in service – a rate unimaginable for privately owned cars, not least because human drivers would fatigue long before that. The workload rewards the simplicity and low maintenance of electric drivetrains, but it also requires redefining what a powertrain is when a car never sleeps.

Electric revolution

“The advent of autonomous vehicles marks a significant shift in the automotive industry, promising to revolutionise how we perceive and interact with transportation,” says Otmar Scharrer, senior vice president for R&D e-mobility at ZF Group, a German company that develops vehicle systems. But the always-on nature of how those vehicles work puts pressure on powertrains, he says. 

“Autonomous vehicles, designed to operate continuously, demand highly reliable and efficient powertrains,” he says. That means they are likely to run out of steam quicker and be prone to earlier faults than those in traditional vehicles, which are used less frequently and for shorter periods. 

“These vehicles will likely require advanced driveline technologies that integrate seamlessly with braking and motion control systems to ensure optimal performance and safety,” Scharrer says. “The need for continuous operation will drive the development of powertrains that can withstand prolonged use without compromising efficiency.”

Drivetrain durability is one problem. Another is keeping vehicles charged on the road. Slow charging is topped up with fast charging, but that pace abuses cells so developers are programming vehicles to preheat on the way back to base, pushing cell temperatures upwards so they last longer, extending life by 15% in early trials. The alternative is to simply swap batteries. California start-up Ample robot-swaps a depleted pack for a fresh one in five minutes.

It’s not just vehicles ferrying humans that could benefit from these redesigned, always-on powertrains. Amazon (and subsidiary arm Zoox), FedEx, UPS, DHL and Walmart are all big logistics firms investing in autonomous delivery and trucking. 

The problem with driverless vehicles is that you have no human available to understand or fix faults. To solve that problem, Volvo Autonomous Solutions operates duplicated steering actuators, power supplies and sensor fusion computers so the truck can continue or reach a safe stopping spot after a fault.

Beyond catastrophic failure, there is also an engineering quandary in that parts wear out quicker – including the batteries powering the next generation of electric cars. Tesla’s own data shows a noticeable capacity loss after 200,000 miles in their vehicles. 

Potential solutions to those issues include predictive maintenance, such as vehicles leaving the depot through a scanner that can flag issues, which early research suggests could improve vehicle availability by around 20%.

Want the best engineering stories delivered straight to your inbox? The Professional Engineering newsletter gives you vital updates on the most cutting-edge engineering and exciting new job opportunities. To sign up, click here.

Content published by Professional Engineering does not necessarily represent the views of the Institution of Mechanical Engineers.