A new sensor developed in Lansing and tested on the Mackinac Bridge can help nip deteriorating roads in the bud – and it's powered solely by vibrations and other movements in the road itself.
Michigan State University associate professor Nizar Lajnef and Shantanu Chakrabartty, a professor with Washington University in St. Louis, deployed prototype sensors under the bridge in a demonstration project sponsored by the Federal Highway Administration in 2016. But Lajnef says the patented technology underlying the sensors has been in the works for about 10 years.
The sensors are self-powered by any vibration, movement, or deformation in the road. Lajnef compares the sensors to the FitBit and other wearable devices that track the user's heart rate, sleep quality, or the number of steps they take.
The sensors monitor movements and vibrations under normal traffic conditions over time and "relate those variables to the health of the system," Lajnef says.
"As you see these changes, you can start predicting the future, like in the next two to three years, cracks or potholes are going to start showing up on this section, or, for a bridge, you can know that a certain component needs to be replaced in two years," he says. "You can have a plan ahead of time and don't have to wait until something gets older (and is about to fail). It's like with your health. You don't wait until something shows up and then see a doctor. You do preventive maintenance."
He says waiting until cracks appear on the surface of a road and then patching it is like "putting a bandage on someone who is lying there dead."
"We're losing billions of dollars by doing that, but if you start detecting problems a few years before they show at the surface, you can fix it ahead of time," Lajnef says. "You can extend the life of the road for a few years for a small investment and save a lot of money."
The sensor technology also has the potential to be integrated into autonomous vehicle infrastructure.
"Everyone is talking about vehicle cameras, lidar, and radar, but what we believe is that none of that is (useful) if the infrastructure isn't ready for autonomous driving," Lajnef says.
Many autonomous vehicle technologies rely on visual cues such as lane markings, but that's not always practical in a state like Michigan, where snow can obscure lane striping for several months of the year. Additionally, the global positioning system that is often used in autonomous vehicle technology is expensive and can be hacked, Lajnef says.
"But if you have thousands of sensors in the infrastructure, you can tell exactly where you are, and the infrastructure can send you information, like that there's a stop sign coming in about a hundred yards," he says.
The sensors can even be used to improve pedestrian and cyclist safety. They can be embedded in sidewalks so equipped vehicles can detect when a pedestrian may be approaching an intersection at a blind spot.
Lajnef says the fact that the sensors are self-powered is an important part of the design. A battery-powered device might be able to run for a year or two, while the sensors he and Chakrabartty created have the potential to last for 40 years or more.
Since the original deployment on the Mackinac Bridge, the technology has been used in several other places, including a Federal Highway Administration test project in Washington, D.C., and in Nantes, France. It's also being used in a test facility in New Jersey under the supervision of the Federal Aviation Administration, because "the same concept that applies to roads applies to airplane runways," Lajnef says.
East Lansing-based startup PIEZONIX LLC is working on commercializing the self-powered sensor technology so it can start appearing in roads and infrastructures around the world soon, Lajnef says.