The DIY promise certain is interesting: a enjoyable mission, a stupendous bespoke end result, and a price that’s only a fraction of what the shop desires. In fact, it by no means works out that means. The mission finally ends up being a nightmare, the outcomes aren’t pretty much as good as you count on, and the fee finally ends up being a lot larger than should you simply bought the factor. However Brandon Lai is younger and I like that he discovered that lesson with out giving up when he determined to DIY a robotic actuator.
Lai desires to construct a robotic and is conscious of the irritating reality, which is that robots are costly. The actuators are a serious line merchandise on a robotic’s invoice of supplies and Lai thought he may avoid wasting cash by constructing them himself. And he was sensible sufficient to know that he ought to work from an present design — MIT’s Cheetah, on this case.
The usual Cheetah actuator design crams a planetary gearbox inside of a BLDC (brushless direct present) motor, yielding plenty of torque in a compact package deal. Lai determined to take the identical method, however with a cycloidal gearbox as a substitute of a planetary gearbox. His reasoning was that it will have much less backlash and would put much less stress on the 3D-printed components.
To construct it, he began with an off-the-shelf stator ring. Then, by hand, he wound the copper wire round that. It, plus the 3D-printed cycloidal drive components, went inside a CNC-milled body/housing from PCBWay. Lai even tried to design his on STM32-based motor controller, however a flaw induced it to blow an IC within the drive circuit. So, he needed to abandon the customized controller at some stage in his testing.
The actuator labored, nevertheless it didn’t fairly stay as much as Lai’s hopes. It wasn’t pushing with as a lot torque as he had calculated (although that might have been as a result of restricted present from the facility provide) and had vital backlash. Extra importantly, the overall price — not together with the controller — was about $400.
For comparability, the CubeMars AK60-39 prices $448.90, exceeds Lai’s focused torque by a superb quantity, has nearly no backlash, and has a sturdy built-in controller. That’s the tough actuality: mass-production is actually arduous to beat.
However although Lai admits his unique aim was unrealistic, he isn’t dropping by the wayside. He has already gone again to the drafting board to begin growing a brand new design and that persistence is strictly how an individual learns the talents to make the DIY method possible.