How Dusty Robotics used a refrigerator to diagnose and fix hardware malfunctions

How Dusty Robotics used a refrigerator to diagnose and fix hardware malfunctions

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Editor’s note: This story was originally published Tessa Lau’s Twitter feed. We have reprinted it here with Lau’s permission. He details how Dusty Robotics diagnosed and fixed a rare hardware flaw on some of its FieldPrinter robots, which can independently print full-size models onto masonry surfaces in a fraction of the time it takes a manual chalk-line layout crew.

About a year ago, we started getting reports from the field about unwanted behavior when running our bots. On rare occasions, they would act unpredictably. Our engineering and CS team investigated all of these reports to try and find out the root cause. Every time a report comes in from the field, we immediately troubleshoot. We were bringing the robot home to try to replicate the failure.

We haven’t been able to reproduce it, but we’ve come up with a theory as to why it might happen. It was the coupling that connected the engine to the wheel. If this is loose, the wheel will not rotate in time, and the robot will drive unpredictably.

So we redesigned the coupler system not to slip under normal operation, and put out the fix on all the robots. With so many customers in the hands of customers, it took a while to cycle through them all.

We have also developed a field repair which involves disassembling the robot and tightening the coupler. The next time a customer called in with this issue, we had them implement this fix. And it worked! The problem has been resolved.

Fast forward to 2022. In the past month, we have started receiving reports again of erratic robot behavior in the field. Once again we brought the bots home and again we were unable to reproduce the behaviour.

We thought this was a new problem. After all, we’ve fixed the couplings and haven’t had any issues with the couplers for the past 9 months. Our team has started systematically correcting all other possible causes.

Dusty Robotics placed several FieldPrinter robots in the refrigerator to help diagnose malfunctioning appliances. | Credit: Dusty Robotics

We assigned an intern to try to reproduce the problem. Since it seems to happen first thing in the morning, it may have been related to the energy boost sequence. The apprentice has turned it off and on a robot hundreds of times. The problem never appeared

Then someone had the brilliant idea of ​​putting a robot in the fridge. We took it out the next morning, and…it showed the problem. for 10 minutes. Then stop. Could it be related to temperature?

But not all robots showed the behavior after being cooled. And 10 minutes didn’t give us much time to debug before the problem went away. So we filled the fridge with the robots and brought them out one by one for the experiment. The kitchen has become the operating room, with robot corpses strewn across operating tables.

Some of the experiments involved measuring what was happening inside the robot while it was cold. At some point I found a speculum outside the fridge measuring the patient’s vitals inside.

Finally, we figured out the problem. One of the off-the-shelf components we’re using has behaved out of specification at certain temperatures, generating a noisy signal. We reverse engineered the component and found that removing two resistors fixed it. The problem is solved for real this time.

Muqrin’s troubles last year turned out to have the same root cause. While people were opening the robot and tightening the coupler, the robot was warming up. By the time they got it back together the problem was gone. It has nothing to do with couplers at all.

By the time we brought up the stabilizer “fix” on all of the bots, the weather had warmed enough across the country that the problem hadn’t recurred. We thought we fixed it, when spring actually fixed it.

When you realize that there are hundreds of components in the simplest robot, and each of them can have unpredictable failure modes like this, that’s why hardware is so difficult.

About the author

Tessa Lau is an experienced entrepreneur with expertise in AI, machine learning, and robotics. She is currently the CEO and founder of a company Dusty robots, which develops robot-powered tools for the modern construction workforce. Prior to Dusty, Lau was CTO/Co-Founder at Savioke, where she coordinated the deployment of more than 75 delivery robots in hotels and high-rise buildings.

Previously, she was a research scientist at Willow Garage, where she developed simple interfaces for personal robots. Lau also spent 11 years at IBM Research working on business process automation and knowledge acquisition. She was recognized as one of the top five female innovators in robotics by Inc. in 2018 and one of the most creative people on Fast Company in 2015. She holds a PhD in computer science from the University of Washington.


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