Mobile-manipulating UAVs for Sensor Installation, Bridge Inspection and Maintenance (AS-1)

Universities: University of Nevada, Las Vegas
                           University of Nevada, Reno
                           Missouri University of Science and Technology

Principal Investigator: Dr. Paul Oh, University of Nevada, Las Vegas

PI Contact Information: Phone: (702) 895-0168  |  Email:

Co-Principal Investigators: Dr. Hung La, University of Nevada-Reno
                                                        Dr. Genda Chen, Missouri University of Science and Technology

Funding Sources and Amounts Provided:
University of Nevada Las Vegas: $170,853
INSPIRE UTC: $198,715

Total Project Cost: $369,568

Match Agencies ID or Contract Number:
UNLV: In-Kind Match   |    INSPIRE UTC: 00055082-05A

INSPIRE Grant Award Number: 69A3551747126

Start Date: November 30, 2016
End Date: December 31, 2020

Brief Description of Research Project:

Mobile manipulating UAVs have great potential for bridge inspection and maintenance. Since 2002, the PI has developed UAVs that could fly through in-and-around buildings and tunnels. Collision avoidance in such cluttered near-Earth environments has been a key challenge. The advent of light-weight, computationally powerful cameras led to breakthroughs in simultaneous localization and mapping (SLAM) even though SLAM-based autonomous aerial navigation around bridges remains an unsolved problem.

In 2007, the PI integrated a mobile manipulation function into UAVs, greatly extending the capabilities of UAVs from passive survey of environments with cameras to active interaction with environments using limbs. Mobile-manipulating UAVs have since been demonstrated to successfully turn valves, install sensors, open doors, and drag ropes. Their research and development face several challenges. First, limbs add weight to aircraft. Second, rotorcraft, like a quadcopter, is an under-actuated system whose stability can be easily affected by limb motions. Third, when performing a task like turning a valve, limbs demand compensation for torque-force interactions. Thus, even if battery technologies afford the additional payload of limbs, current knowledge for manipulation with under-actuated systems remains sparse.

Approach and Methodology: The null-space techniques on impedance controllers will be investigated and applied to improve the controllability of mobile-manipulating UAVs. They have been successfully implemented on spacecraft (like the Space Shuttle for satellite retrieval) and underwater robots (like rovers for ocean salvage). However, to avoid instability, limb motions in bridge applications tend to be slow (hence quasi-static) with small inertias. Additionally, multi-limbed UAVs will also be designed, tested, and modeled as they show distinct advantages in valve-turning and drilling tasks. Together two limbs grip and rotate with thrust vectoring a traditional circle-shaped valve. One limb grips a pole while the other limb drills.

Overall Objectives: This project aims to develop and prototype a mobile-manipulating UAV for bridge maintenance and disaster cleanup through further study on SLAM technology for robust navigation, impedance controllers to ensure UAV’s stability with limb motion, and coordinated and cooperative motions of multiple limbs to perform simple tasks like bearings cleaning and crack sealing in concrete bridges. Two strategies will be explored for bridge maintenance: (a) A UAV brings and uses a can of compressed air for bridge cleaning, and (2) Two UAVs airlift, position, and operate hoses from ground, and clean bridges with air or water. The latter can be potentially implemented by including a station-keeping, lighter-than-air UAV like blimp that can airlift a hose and remain airborne for extended periods. The mobile-limbed UAVs can then pull-and-drag the hose into areas that need to be cleaned.  The blimp-based approach is attractive because it is easier for a UAV to drop hose lengths rather than pull the hose up in air.

Scope of Work in Year 1: (1) Design and use hyper-redundant serpentine-like limbs (to act like octopus arms, monkey tails or elephant trunks) for dexterous manipulation, and (2) Explore multiple UAVs for coordinated and cooperative missions.

Scope of Work in Year 2: (1) Design and construct a suitable end-effector for a representative arm, and (2) Make it function as a gripper that allows the mobile manipulating UAV to grasp a wide range of objects such as hoses, sensors, and tools.

Scope of Work in Year 3: Leverage the robotic limb and gripper designs to (1) conduct bridge cleaning such as hosing and debris gathering, and (2) Repair bridge components with epoxy.

Describe Implementation of Research Outcomes:
Research outcomes and implementation plan will be described towards the end of this project.

Impacts/Benefits of Implementation:
Impact/Benefits of Implementation will be summarized at the end of this project.

Project Website:
Progress Reports: