A Year of Quadcopter ExperimentationBy Ken Gracey
Safety Testing Lessons LearnedJameco customers are perpetual experimenters, innovators and fabricators. It's been this way for a long time, well before our recent mini industrial revolution. With so much experience, they have probably encountered a safety incident that has reinforced their value for workmanship.
Basic Quadcopter: The ELEV-8 I'd like to share some of our experiences with this topic, applied to a specific project we've been doing. Parallax's technical team has been experimenting with quadcopters for over two years now. Flying robots are like aerial laboratories that provide a lifetime of projects, each requiring its own research. With quadcopters, you can experiment with first-person view (FPV) flight over video link, payload delivery of rolling robots (or burritos), aerial photography, GPS location and elevation sensing, and XBee High Power radio links.
Few projects demonstrate the connection between quality workmanship and personal safety as well as quadcopters. With larger quadcopters weighing over 10 pounds – or twice that with a payload – a craft that doesn't glide can cause serious damage if something goes wrong. This kind of experimentation is only growing in popularity, so the frequency of accidents will likely increase.
What kinds of accidents are possible? Listing them is truly concerning, so I'll leave most of that up to your imagination.
At Parallax I am the person who authorizes the expenses, the one who approves our errors and omissions insurance policy, and I'm also aware of workmen's compensation issues. And with the upcoming Federal Aviation Administration (FAA) focus on drone regulation, I pay attention to what our team is doing with quadcopters. No matter who on our staff is flying, an accident will become my problem personally and professionally. Yet I know we must also carefully participate in this growing market since our propeller chip is perfectly designed to fly multirotors.
This project has helped us reconsider the role of workmanship in hobby projects and to place an elevated importance on safety. Let me share a few experiences and findings.
Important Role of Workmanship
There's plenty of opportunity for poor workmanship to bring a quadcopter out of the sky:
• Connections must be soldered perfectly without mixing connector brands.
• Electronic speed controllers (ESCs) must be calibrated to work properly with the control system.
• Wiring between receiver and control system, and between ESCs and control system must, be exact with strain relief.
• Motors must spin in the right direction – half are counter-rotating and must have reverse propellers.
• Fasteners must be properly tightened with threadlock compound or else vibration will quickly rattle them apart.
• Final assembly of all parts to the airframe would need to be precise, with secure and proper mounting.
• Lithium polymer batteries would need to be carefully wired and charged.
• Rough landings can cause hidden frame or propeller damage that only exhibits problems when back in the air.
• Radio interference could be a complete surprise. Proper antenna placement and range-checks are necessary.
Consider these points of failure with the first-time excitement of building a quadcopter! Jameco and Parallax customers are innovative and have experience with assembly, yet all of us are doing this project because we want to. It's not something being requested by the boss, but a reward for the work we do every day. With limited spare time and lots of motivation, we want to work quickly and put the thing into the air before too many weekends pass by. Here lies another danger: rushing!
Recordkeeping Tells the Story About the Human Factor
The Parallax flight team posted accidents for all to see. While they may seem humorous, the accident log (shown below) worked to raise the bar among peers to have the highest safety and most time aloft. We don't share our accident log out of some passive arrogance that we had escaped more serious problems, but to transfer this experience to others so they may avoid duplicating our mistakes. And to be truthful, there were many.
"First Blood" occurred when Matt's quadcopter flew into his face on Christmas Eve. Though the firmware accepted an arming sequence, the radio must have had some configuration issue on the throttle channel (exponential throws, narrow throws, etc.) that caused this problem. Matt took 11 stitches to the face and was back at work after Christmas Day.
My "First Blood" was a careless mistake of brushing against the throttle while positioning an armed quadcopter for flight, resulting in a small cut on the ankle. A small number of other accidents were the result of loose screws and insecure wiring, occurring early in the process of experimentation.
In short, I was really impressed with the fact that workmanship wasn't the problem I thought it would be after we qualified the key components. After all, Nick and Kevin work as Technical Support Engineers. Their days are spent doing hands-on projects with Parallax products, laser cutters, 3D printers and code. Nick gave eight years to the country as a U.S. Marine on the front lines in Afghanistan and Iraq, and Kevin designed many printed circuit board sensors for Parallax.
Yet the human factor is what caused most of the accidents. What people do in the presence of others is often less reliable than what they do on their own. With quadcopters, an airborne collision takes two pilots; in our case, two Parallax pilots. Hitting "Bonnie's BMW" or "Kevin's Toaster Car" in the parking lot meant we were flying too close to the vehicles, not that the vehicles were too close to our flying area. The underwater recoveries occurred during a team camping trip when we were flying six LED-illuminated quadcopters at the same time in the steep American River Canyon – at night! Thankfully, the LEDs made the quadcopters visible on the bottom of the river for our reticent divers. Catastrophic crashes with trees or ballpark light standards were also common in nearby parks.
All of these types of accidents could be avoided by alert pilots who don't lose track of the front of a hovering quadcopter. Compasses are now used for heading hold and barometric pressure sensors are used to maintain elevation, so these problems are being diminished. Parallax now flies quadcopters at the end of a very open street near our business park. We've fine-tuned our approach toward safety by controlling everything we can.
Safety of Casual Observers
During field tests, we assume casual observers are entirely unaware of the dangers of any of our creative projects, whether a small CNC machine, 3D printer or large mobile robot. When properly built and controlled, all of these devices start to look almost natural. Watching a quadcopter fly can lull viewers into a false sense of comfort as it gently hovers, rotates and flies around like a dragonfly. Yet one loose cable or firmware problem could send it smashing straight to the ground or shooting out toward a freeway.
Last month in Taiwan I was asked to fly a quadcopter in front of 500 people to formally commence a national robot competition. To be comfortable with this idea, I used a quadcopter I had carefully built on my own. I had to see the facility in advance, inspect and test the quadcopter carefully the night before, test the radio range and possibility of interference, and on the flight day move the viewers to safe areas well outside of the flight path and under the second level. Only then did I decide it was appropriate to conduct the successful demonstration.
It's our responsibility to assess all of the variables that make any project dangerous, to minimize those dangers and make safe decisions even though some activities are inherently risky.
Why the Safety Officer Cares
There's a reason every company has a safety officer who seems to care about safety more than anybody. Chances are they've seen or been part of an accident that could've been avoided. At Parallax, you'll see my father Chuck making a daily tour of the facility. During spring, if he isn't bringing roses to the women in the office, he tours the facility and addresses unsafe situations. Chuck experienced a bad chemical burn on his arm and hearing loss from years of high-noise aerospace environments. Of course, he's a proponent of putting guards around our quadcopter propellers. It's this kind of experience that makes safety so important; safety officers know that accidents can be avoided.
The Human Factor Is True for All Projects
Quality workmanship is an important first effort toward safety. Once you're comfortable that you've done the best work possible, you can turn your attention to the human factor, which includes how you use your projects, how they are coded for fail-safe conditions, power management and how people interact with them.
Any hobbyist or multirotor pilot should consider my father Chuck's refrain: "there are bold pilots and there are old pilots, but there are no old, bold pilots." You can avoid crashing your project if you don't become a bold pilot.
Ken Gracey is the President of Parallax and an advocate of supporting technical interests among the team. His enthusiasm for projects began by watching from the highchair as his father built a cabin. Growing up with his brother Chip (creator of the BASIC Stamp and Propeller), the Gracey boys had a detached room where they could work with Apple computers, electronics, fireworks and woodworking tools. Parallax is that kind of laboratory today and they enjoy sharing it with guests from around the world.
If you have an electronics story you'd like to share, please send it to [email protected].