Final Design

Automated Refueling for Hovering RobotsNigel Cochran (RBE/ME), Janine Pizzimenti (RBE/ECE), Raymond Short (RBE/CS)

AbstractSmall-scale, battery-powered unmanned aerial vehicles (UAVs) suffer from short mission times before they must land for manual refueling, making the UAVs not truly autonomous for extended periods of time. This solution aims to be an innovative approach to a more refined iteration of previously proposed refueling solutions, while adding the novel functionality of being universal for many UAVs that are battery powered and can perform vertical takeoff and landing. The proposed design is a base station that positions the landed UAV to a known orientation, then exchanges and charges the UAV’s battery. This solution allows for persistent flight of the UAV by maximizing its in-air duty cycle.

Project Goals

UAV to Base Communicatio

nReliable UAV Positioning

Exchange and Store

Batteries

Charge and Balance Lithium-Polymer Batteries

Maximize In-Flight Duty

Cycle

Easily Adapted for other UAVs

Solution Features• Off-the-shelf charge/balancing with custom interface• Enough batteries to allow missions of any length with

high duty cycle, minimize time for battery swap• ~ 2’x2’ open landing area with active alignment• Custom battery mount and UAV skids• Can be made universal for many UAVs

• Rotating battery track• ROS communication• UAV reports battery level• Base signals when UAV can land

• 109 grams total weight added to UAV• Exchange time of approximately 4 minutes

Battery ChargingVenom Easy Balance AC LiPo Charger• Small: 4.01”x2.44”x1.39”• Charge Rate: 0.1-4.5 A

(Mechanical Dial)• Balances: 1 Battery, 2-4 Cells• Design Advantage: COTS

UAV Alignment DeviceAligns UAV in center of base in increments of 90°Two Servo-actuated four-bar linkages• One servo per four-bar• L-shaped arms interlock for

consistent positioning

Universal UAV SkidsCan be fitted to most vertical landing, small scale UAVsBased on Pelican’s skid designIncludes extended feet to widen base for easy battery exchange

Battery Transfer System

Scissor lift to raise/lower batteriesRack/pinion & linear bearing to move between dock and UAV• Limit switches to detect

locationStepper Motor on turntable to rotate between eight charging docks• Photo interrupters to detect

location

Battery Mating/AlignmentRotationally symmetrical design0.2” of compliance in mechanical alignmentPyramid guided touch latch

Program Flow

Advisors: Professor Ken Stafford (ME/RBE) and Professor William Michalson (CS/ECE/RBE)Acknowledgements: Brian Julian, Edward Clancy, Mike Boulet, Joe St. Germain, MITLL Group 76, MITLL Group 77