Designing Semi-Autonomous Networks of Miniature Robots for Inspection of Bridges and Other Large Infrastructures

Visual identification of structural flaws is quite valuable not only to predict an imminent collapse of a bridge, but also to determine effective precautionary measures and repairs.

Statement of objectives: In this project, we will pursue a three-year basic research program to establish new design and performance analysis principles, and technologies for the creation of a semi-autonomous network of small mobile robots to aid visual inspection of civil infrastructure. This network will aid a human surveyor to remotely and routinely inspect structure areas such as a typical girder assemblage that supports the decks of a suspension bridge. Methods to be used: The goals mentioned above will be addressed via a multidisciplinary basic research effort in hardware, algorithm design and performance analysis. In order to achieve this goal, our team includes one researcher (CTO of Resensys LLC) in the area of bridge monitoring, and 3 faculty from 2 departments. Our team's expertise covers all the key basic research areas of the proposal.

Broader Impacts: A) The activities funded by this grant will assist in the visual monitoring and guide the maintenance of bridges, which will improve public safety and reduce cost. B) The technological outcomes of this grant will be applicable to other infrastructure, such as tunnels and buildings. C) Proposed educational activities include STEM activities that will help attract and retain young talent to engineering. Here, we will prioritize the inclusion of underrepresented students. D) This grant will have a major impact not only in fostering multidisciplinary research among the PIs and beyond, but it may also lead to further investments by the University of Maryland (UMD) to promote research and education on CPS. E) This grant will promote a solid collaboration between the UMD, Resensys and the Maryland State Highway Administration. F) Our team is formed by a junior entrepreneur and faculty at the associate level whose research programs will be significantly impacted by this grant.

Summary of Technical Approach: We will investigate fundamental principles and theories on algorithm design, performance evaluation, electroadhesion, dynamic locomotion and system integration. The following is a summary of our current and recent research:

1. Work on the robot locomotion aspects of this project, including both electroadhesion for robot attachment to various surfaces and robot design, are progressing. Numerous experimental studies to validate theoretical models of electroadhesives were conducted, with experimental results. Some interesting insights from this work were recently submitted in a journal paper to Advanced Functional Materials. The electroadhesives tested generally correlated well with theory with a few exceptions. At low dielectric thicknesses, the devices underperform, indicating possible air breakdown. Bending rigidity of the device also has a significant affect with a 2.5x improvement in force at failure for devices with bending rigidity 8x less. In addition, we have also investigated failure mechanisms in our fabricated electroadhesives using high speed video. Device shape (aspect ratio) can substantially improve force at failure -- electroadhesives with an aspect ratio of 4 (short and squat) have a failure force 3x lower than adhesives with an aspect ratio of 0.25 (tall and skinny). A robot design is being explored that includes a compliant body that will allow for plane transitions (e.g. horizontal to vertical) that are common on bridges. The schematic of a control board that includes a camera as well as a radio to communicate with the static SenSpot sensors has also been completed. This board will be programmable using the open-source Arduino interface, allowing for programming accessible to undergraduate researchers.
   
2. We studied the problem of planning the deployments of (mobile) robots for bridge inspection. The robots are assumed to be initially stationed at multiple depots placed throughout the bridge. The problem is formulated as a min-max cycle cover problem in which the vertex set consists of the sites to be inspected and robot depots, and the weight of an edge captures either (i) the amount of time needed to travel from one end vertex to the other vertex or (ii) the necessary energy consumption for the travel. In the first case, the objective function is the total inspection time, whereas in the latter case, it is the maximum energy consumption among the deployed robots. We proposed a novel approximation algorithm with approximation ratio of 5+