A climbing robot developed by researchers in Switzerland could help engineers to ensure the safety and structural integrity of the country's more than 3,500 road bridges.
As a mountainous country laden with rivers and streams, Switzerland is highly dependent upon its myriad bridges to safeguard the successful operation of its road and rail system, which is vital to the sound functioning of its national economy.
The use of reinforced concrete as the material of choice for the country’s transportation infrastructure means its bridges are sturdy and capable of supporting heavy loads, yet also susceptible to corrosion with the passage of time.
This is particularly the case given that Switzerland’s frigid winters necessitate the use of salt to de-ice its roads. The chloride contained by the salt contributes to the corrosion process by eating away at the reinforcing steel within the concrete.
According to Bernhard Elsener, professor at the Institute for Building Materials at ETH Zurich, Switzerland’s bridges are highly vulnerable to this corrosion process given that many of them are already more than half a century old.
Salt-induced corrosion is especially problematic given that it often only becomes visible at a highly advanced stage of decay, and repair work comes at an exorbitant cost.
In order to help address this potentially debilitating problem for Switzerland’s infrastructure system, Elsener and a team of researchers have developed a robot inspection device which is capable of climbing bridges in order to detect signs of early corrosion.
The robot makes use of a detection method which was first devised by Elsener around 25 years ago – running an electrode-fitted wheel across the surface of a reinforced concrete structure to measure its electric potential difference. A large difference could be significant of the corrosion of the underlying steel reinforcement.
While this method has been in use since last century, it practical application has been impeded by the need to run the electrode-fitted wheel across the surface of bridge structures manually, with a long stick serving as the only means of extending its reach.
The very nature of a bridge and the barriers they are designed to overcome means the method cannot be applied to many parts of these structures, such their undersides supporting pillars.
In order to address this dilemma, the Institute of Building Materials collaborated with experts from the Institute of Robotics and and Intelligent Systems (IRIS) to develop a robot which was capable of climbing across vertical surfaces or ceilings while equipped with the detection wheel.
The team was lucky enough to have a solution ready at hand, in the form of robot called Paraswift which was developed four years ago by a student at IRIS for the purpose of shooting movie scenes from peculiar angles.
The robot is capable of climbing up walls and along ceilings by means of Vortex technology, which entails the use of a fast-rotating propeller attached to its belly in tandem with a movable suction cup to cling to difficult surfaces. The robot then uses wheels to move around, while being steered using a remote control device or computer.
For the purposes of the new project, the Paraswift was fitted with the corrosion sensing electrode wheel and in a nod to the Star Wars movies rechristened the C2D2 (Climbing Corrosion Detecting Device). It was also equipped with a sturdier casing and wheels, an additional camera to help identify any obstacles, as well as a pink ball on its top to make it easier to identify from a distance.
The researchers took a patent on the C2D2 in 2012, and won an award for the device in the “Prolongation of Service Life” category at the Concrete Innovation Conference’s inaugural competition in June 2014.
The engineers are now working on improving the robot’s ability to negotiate vertical surfaces, as well as replacing its manual steering with a navigation system which will enable it to operate with greater autonomy.