Mechatronic Cat Ears For The Rest Of Us

Every now and then you see a project that makes you smile. It may not be something that will deliver world peace or feed the hungry, but when it opens in your browser in the morning you go to work a bit happier for the experience.

Just such a project is [Radomir Dopieralski’s] set of wearable mechatronic cat ears. A cosplay accessory that moves as you do. Very kawaii, but fun.

You may have seen the commercially available Necomimi brainwave activated mechatronic ears. [Radomir’s] version does not share their sophistication, instead he’s using an accelerometer to detect head movement coupled to an Arduino Pro Mini driving a pari of servos which manipulate the ears. He provides the source code, and has plans for a miniaturised version using an ATtiny85 on its own PCB.

Amusing cuteness aside, there are some considerations [Radomir] has had to observe that apply to any a head-mounted wearable computer. Not least the problem of putting the Pro Mini and its battery somewhere a little more unobtrusive and weatherproof than on top of his head. He also found that the micro-servos he was using did not have enough range of movement to fully bend the ears, something he is likely to address in a future version with bigger servos. He’s yet to address a particularly thorny problem: that a pair of servos mounted on your head can be rather noisy.

We’ve covered quite a few cosplay stories over the years. This is not even our first cat ear story. More than one example of a Pip Boy, a HAL 9000 costume, and a beautifully made Wheatley puppet have made these pages, to name a few. So scroll down and enjoy [Radomir’s] video demonstration of the ears in action.

14 thoughts on “Mechatronic Cat Ears For The Rest Of Us

  1. So… are there any “quiet” servos? Noise level is not something that shows up in the usual lists of specifications.
    What factors lead to noise in servos, anyway? (can you lessen noise by using a different gear tooth shape, for instance?)
    (I suppose you can make your own servos using more-expensive gear motors or steppers and feedback pots…)

    1. The gear train, mostly. Using helical gears makes them quieter but they are usually more expensive. But they are still not what I would consider quiet.

      You could do a direct drive brushless motor with little noise. You would want a pretty high PWM frequency to keep that noise down. Or possibly a voice coil like arrangement.

    2. Also in the video you can hear some of the noise is from the PID loop. Since most servos have the pot for feedback on the output shaft the PID loop is kind of slow so they tend to hunt a little bit when they change position. This means you hear more noise from the gear train because of backlash.

      1. You can disable the PID by stopping the PWM signal once you have given the servo enough time to travel. That amount of time can be figured out by knowing how much travel you are asking the servo to do and its rotational speed.

    3. I expect you could quiet down standard RC servos if you re-packed the gear-box solid with grease. An oil bath would work just as well with higher efficiency, but would be a giant mess without careful sealing.

      “muscle wire” would be another silent option. Hard to control though.

  2. Actually, these look much better than the necomimi. The necomimi are made of a fluff-coated, stiff foam core that can only rotate (not fold), giving it a slightly less realistic look. Also, the headpiece itself is really super clunky. And lastly, the EEG control they advertise makes for a nice story to tell people, but does barely work.

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