inspector drone detailed report
TRANSCRIPT
Society of Manufacturing Engineers
Direct Digital Manufacturing Competition
Inspector Drone
Presented by:
Tito Arana: [email protected] Jordan Castillo: [email protected] Michael Gager: [email protected] Dan Stella: [email protected] Joanel Vasquez: [email protected]
Academic Advisor: Dr. Stephen Johnston: [email protected]
2 http://www.dispatch.com/content/stories/national_world/2012/02/05/u-s--bridge-inspections-vital-but-pricey.html
Abstract Unmanned Aerial Vehicles (UAV) are designed to perform various task from recreational to industrial
use. This design will offer an alternative method to the way bridges are currently being inspected. Utilizing the versatility of UAVs. With the ability to print carbon fiber using the MarkForged series of 3D printers, this design is made possible. The design is based on custom made landing gear and rotor shields 3D printed to extend the deployment time of UAVs. Seeing the potential of 3D printing and UAVs to aid with bridge inspection, this project evaluates a current technology and put to practice as safety and effectiveness as a tool for bridge inspection.
Social and Environmental Impact Analysis:
The aging infrastructure of U.S. roadways is a well-documented issue, with bridges in particular receiving a C+ grade from the most recent Infrastructure Report Card1 published in 2013 by the American Society of Civil Engineers. Bridge inspections are a crucial part of deciding which bridges need replacing, repairing, or upkeep. With this in mind, the choice was made to design a component that allows drones to be used during bridge inspections. Bridge inspections can cost anywhere from $15,000 to well over $100,0002
depending on the type of inspection required and type of bridge. For this report an inspection is assumed to be $25,000. A large portion of this cost comes from the way in which bridges are currently inspected. This includes hiring a large crane to drive on top of the bridge deck. A team of engineers or licensed inspectors use the cherry picker basket operated by the crane to drop over the side of the bridge in order for the Figure 1: Comparison of Current to Drone-Based Inspection Method
inspector to visually assess the condition of the bridge. There are two primary concerns in this method. The first concern being that this method does not give full access to underneath the bridge deck. If the crane arm extends too long underneath the bridge deck, there is a tipping hazard. The second fault is that this method requires at least a portion, if not all, of the bridge to be closed to traffic. This increases traffic in other areas and also has a cost associated with it due to shipping and receiving delays.
Using drones to inspect bridges removes the need to shut down travel lanes because it can be operated remotely, requiring one on-site operator rather than a team of licensed inspectors. A drone also removes the need for inspectors to be supported by a crane. This means there is no human life in a hazardous situation, and the cost associated with hiring a large crane, operator, and traffic detail becomes unnecessary.
1 http://www.infrastructurereportcard.org/a/#p/bridges/overview
4 http://store.makerbot.com/replicator
Drones do come with their own limitations, the first being flight time and the second being stability and collision.
Design In order for a drone to be a viable option we must minimize the limitations. In order to maximize flight
time a set of landing gear was designed so that the drone can fly to the required location, deploy the landing gear between two I-beams underneath the bridge deck, and turn off the motors controlling the rotors while perched. Stability of the drone is heavily reliant on the operator. In order to assist the operator, the team designed a set of rotor shields so that during a collision the rotors are not stopped or damaged, preventing them from producing the necessary thrust.
The landing gear consists of 4 arms that are 36” long and are extended and retracted with the use of a power screw and linkage system. It is designed to work with bridges that have a distance between support beams from 1.5 - 2 meters. In order to accommodate the varying sizes of bridges the arms are built in 12” segments with quick disconnects to easily add or remove them.
In order to prevent flight failure, shields have been designed to be placed around each of the 6 rotors. These shields can be clipped in to the existing frame. The area of these shields are small enough to minimize airflow disturbance while maintaining the structural integrity necessary to shield the rotor from impact. Due to the inexpensive nature and thin frame of the shields they are considered replaceable and new ones can be printed as the need arises.
Justification of DDM Choices and Materials
A material with a high specific strength is required for the landing gear. Carbon fiber is a common material in the aerospace industry for this very reason. Not only will it give the needed structural support, but it also minimizes the added weight to the system. A MarkForged Mark Two3 series printer allows us to print carbon fiber layered with nylon. A single layer from the Mark Two is 0.1 mm thick, the truss in the landing gear arms are 1.25 mm thick. This was done to prevent buckling, even though there is a large safety factor in vertical bending. This material has a tensile strength similar to aluminum, but at a much lower weight cost. The printer also allows us to maximize the tensile strength of the material by orienting the fiber in the required direction. The shields are printed using a Makerbot Replicator4
and constructed out of ABS. The relatively inexpensive cost of ABS allows for this part to be easily and Figure 2: Stress Analysis of Landing Gear
3 https://markforged.com/
cheaply replaced when it fails. This part is expected to see failure since it is meant to absorb the collision in place of a rotor.
Cost-Benefit Analysis: As of 2013 there are
over 600,000 bridges in the National Bridge Inventory5
database and they all require routine inspection at a maximum of every 24 months. Assuming an average cost of $25,000 per inspection and a total of 300,000 bridges are inspected per year, this leads
Table 1: Cost-Benefit Analysis
to a target market of $7.5 billion annually. The goal is to start out with 0.5% of this market, or to have our design used for 1,500 bridge inspections. Assuming a scenario where a different drone is used for each bridge 1,500 complete drone modification kits need to be manufactured in the first year, or roughly 4 per day. A modification kit includes 4 arms and 6 shields. To manufacture a modification kit takes 24 hours per arm, and 4 hours per shield. A total of 16 MarkForged Mark Two printers and 4 Makerbot Replicators are necessary to achieve this production volume. A complete landing gear setup costs $257.60 in carbon fiber and nylon to produce. A full set of rotor shields will include 6 shields and cost $5.76 in ABS to produce. A stepper motor is required to drive the arms into position and costs $50.00. The total production cost of each modification kit is $313.36. If each modification kit is sold for $1,000 than an annual profit of $1.03 million is forecasted.
Table 2: Savings per Day of Inspection Selling a drone
modification kit for $1,000 is reasonable based on the cost savings for an inspection. Using a drone saves roughly $1,800 for the crane and operator, $400 for the traffic detail, and $3,200 in on-site inspectors, or a total of $5,000 per day of inspection. We believe purchasing the recommended drone and modification kit for a total of $2,000 is well worth the $5,000 per day savings.
The company expects to take at least another .25% of the market annually. This will lead to a 1.5% share of the market in 5 years, or have our drones used for 4,500 bridges. A profit of $3.09 million annually is forecasted in this scenario. Once production volume reaches 10,000 shields annually the manufacturing of these will likely be switched to injection molding rather than 3D printing in order to reduce cost and increase production speed. Currently the designs are only fitted for DJI FlameWheel F550 Hexacopter model. As the company expands we aim to increase the number of models that our landing gear can fit and even build custom gear on an individual basis. This will also increase the size of bridges that are compatible with our design and the type of test sensors that can be used in order to keep pace with emerging technology.
5 http://america.aljazeera.com/articles/2013/9/16/many-us-bridges-arestructurallyunsoundsaysnewreport.html
Costs Amount Desicription Overhead
$500,000.00
Includes Rent, Printer Costs, Printer Maintenance, Employee Salaries, Employee Benefits, Marketing
MarkForged Printers $88,000.00 16 Mark Two Printers @ $5,500 each Makerbot Printer $5,800.00 2 Replicator Printers @ $2,900 each Motor $50.00 1 Stepper to Drive Power Screw Carbon Fiber $240.00 Cost for Complete Set of Landing Gear Nylon $17.60 Cost for Complete Set of Landing Gear ABS $5.76 Cost for 6 Rotor Shields Producer Cost $313.36 Total Cost per Drone Modifcation Kit Price Sold to Customer $1,000.00 Profit per Set $686.64 Complete Sets Printed Annually 1,500 Annual Profit $1,029,960.00
Savings Amount Descirption Crane $1,000 Daily Cost of Crane Crane Operator $800 8 hours for Operator @ $100/hr Traffic Detail $400 8 hours for Police Officer @ $50/hr On-site Inspectors $3,200 8 hours for 3 Inspectors each @ $100/hr Daily Savings $5,400