CPS:Synergy:Collaborative Research:Designing semi-autonomous networks of miniature robots for inspection of bridges & other lar

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 are pursuing 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 are being 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 are investigating 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. To move around on complex bridge environments, a new robot has been designed and constructed. A key part of the robot design has been adding compliance to the robot for traversal across rough surfaces (e.g. rivets) and to allow for transition between horizontal and vertical surfaces. The chassis is 3D printed on an Objet Connex with multiple materials to create viscoelastic joints that help reduce vibrations and provide smooth traversal on rough surfaces. Adhesive properties between the robot and bridge are currently simulated with magnetic wheels, and electronics include a 32-bit 48 MHz ATSAMD21 chip, radio, motor drivers, a camera, and additional sensors. The electronics are programmable through the Arduino IDE making these robots accessible to undergraduate researchers. To move beyond ferrous surfaces, the last year has focused on modeling and understanding failure mechanisms in low-voltage electroadhesives. A basic friction model has been proposed and validated with a few exceptions in experimental testing. High speed video was used to better understand why devices fail and new strategies based on this data to further improve shear strength and wear over time will be evaluated during the coming year. This work is under review for Smart Materials and Structures.
2. We also initiated the development of a robot that can move along non-magnetic vertical surfaces. It uses a powerful fan to press it against the surface with enough force to allow steering using four independently controller wheels. A raspberry pi 3 is used as onboard computer, which is tasked with control of the fan, wheels, communication modules and a camera. The ultimate goal is to use this robot in a semi-autonomous mode for infrastructure inspection.
3. 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+