Thursday, March 03, 2016
Anti-Cogging Algorithm Brings Out the Best in your Hobby Brushless Motors
Hackaday: Cheap, brushless motors may be the workhorses behind our RC planes and quadcopters these days, but we’ve never seen them in any application that requires low-speed precision. Why? Sadly, cheap brushless motors simply aren’t mechanically well-constructed enough to offer precise position control because they exhibit cogging torque, an unexpected motor characteristic that causes slight variations in the output torque that depend rotor position. Undaunted, [Matthew Piccoli] and the folks at UPenn’s ModLab have developed two approaches to compensate and minimize torque-ripple, essentially giving a cheap BLDC Motor comparable performance to it’s pricier cousins. What’s more, they’ve proven their algorithm works in hardware by building a doodling direct-drive robotic arm from brushless motors that can trace trajectories.
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Well, Boevers, I did it. I clicked on an article that frightened me, an article that I understood very little of, and article that I needed the help of an online dictionary to get through. Am I a better person now? Have I suddenly grown into being a better student?
Probably not, but I did just learn something totally new.
Today, cheap, lightweight motors abound. Their in demand, whether it comes to quadcopters or basically anything that is lightweight but needs one or more mechanically moved elements. These motors are usually relatively cheap, and can be found for very low prices, but buyer beware. According to the video clip from the University of Pennsylvania, the cheaper a motor is, the more torque ripple it has. (Torque ripple, according to wikipedia, is the "difference in maximum and minimum torque over one complete revolution"). After finding out what that was, I was able to deduce generally what this article was saying.
Apparently, some people at the university of Pennsylvania have come up with a way to capture and visualize the amount of torque ripple a motor has depending on its position. (Torque ripple changes based on position, so that's big.) This allows for the most efficient installation of one of these small motors, something that will surely change some part of the world significantly.
Voila! I have learned!
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