Developers of driverless trucks are eliminating some of the complexity of autonomous driving in hope of shortening time to market. They are limiting the immeasurable circumstances that face driverless vehicles by deploying a variant of platooning or narrowing the operating parameters for transporting goods.
Driver shortages, growth in shipments of online purchases and the never-ending push to trim costs are among the factors that have led many to predict that commercial trucking will be an early adopter of autonomy. Several vehicle-system developers at SAE COMVEC Technology Connection in Indianapolis detailed strategies that will let them get to market more quickly by reducing the requirements of autonomous technology.
One strategy is to limit the roles of autonomous vehicles. TuSimple plans to have fully autonomous trucks on the road fairly soon. TuSimple’s systems will let trucks drive from dock to dock without a driver. But to minimize operational requirements and validation times, the company plans to limit usage. The first vehicles on highways may be limited to open roads. They won’t be operational in harsh weather conditions and in some areas such as congested streets.
“By 2021, we plan to do driver-out tests,” said Koabi Brooks, general manager at TuSimple. “At the end of that cycle, around 2023, we plan to see full production. One of the main factors will be to define the operational design domain. The narrower you define it, the less often you’ll have issues.”
Follow the leader
Another strategy is to make two-vehicle convoys, letting a driver in the lead vehicle make most driving decisions, reducing the number of challenges faced by the trailing autonomous vehicle. The trailing truck will depend on both its automated systems and the experience of the driver in the lead.
“We do autonomous convoying, hiding an autonomous truck behind another autonomous truck,” said Cetin Mericli, CEO at Locomation. “That transforms the autonomous problem into something more tractable. The driver in the following truck can leave the driver seat to do other jobs or sleep. After two or three hours, the trucks can switch roles to give the other driver a break. That’s relatively easier than taking the driver out of the cab all at once.”
It’s relatively straightforward to drive when all environmental conditions are within common operating conditions. It’s the more complex corner cases that can confuse automated systems. An experienced driver in the lead vehicle can easily navigate situations that might cause an autonomous controller to wait or even sideline the vehicle. Peloton Technology is also relying on humans to handle unusual conditions.
“The driver is the most intuitive sensor,” said Matt Hall, VP of Peloton. “This approach lets us look at areas like construction spots—the driver knows to slow down, the second truck only has to follow. In areas like traffic control, where a police officer may tell you to run a stop sign, a human driver easily understands what to do.”
While platooning can simplify driving in many different environments, proponents are also limiting operational domains. Vendors plan to start with usage models that will help build confidence in autonomous technologies by avoiding accidents and other problems that could harm the autonomous movement. “Our goal is not to provide a blanket solution,” Mericli said. “We’ll start with a matchmaking process. We’ll start finding segments in the freight network that are best suited for deployment.”
Along with reduced workloads for drivers, vehicle convoys can bring fuel savings. Narrowing the gap between trucks will improve mileage for the second truck. When trucks are closer together, it’s harder for cars to slip between them and complicate the task of making two trucks travel as one. Convoyed vehicles can have shorter following distances than ranges of NHTSA regulations, though system developers still need to figure out what’s safe.
One benefit is that sensors never sneeze or glance down at radio knobs or phones. Constant vigilance can reduce collisions or lessen damage. “We frequently reduce distances to an average of less than 200 feet,” Hall said. “We hope to reduce it to 30-50 feet. That will reduce cut-ins, which really impact following. Collisions can still occur, but autonomy mitigates the impact velocity because the trailing vehicle is slowing down.”
When trucks with trailers need to stop quickly, brake systems become a critical element. The close following distances associated with autonomous platoons may drive a change in braking systems. Digital controls and brake-by-wire are being combined into electronically controlled braking systems that manage brakes on both truck and trailer.
“The electric braking system’s footbrake module detects the stroke, and the electronic control unit calculates the brake pressure needed for the required deceleration,” said Alex Augoustidis, product manager at Bendix Commercial Vehicle Systems. “Braking systems can have axle-centric pressure control so they can apply brakes where the load is. That gives the driver more stability and more control.”
These electronic braking systems also take variances in road conditions and braking components into account. That’s important in convoys, for example when a trailing truck with worn brakes is on a slick spot while following a vehicle with new brakes on dry pavement. “Electronically controlled braking systems are the only technology that recognizes when trucks are braking on oily roads or when brakes are aging,” said Wolfgang Hahn, system integration leader at WABCO, which is being acquired by ZF.Continue reading »