合宿参加不可に

  6月に開催予定のマウス合宿に参加する予定だったのだが，とても参加していられる状況ではなくなってしまった．よって今回は不参加ということに．

  なんとなく新作ハーフマウスの設計を進めていたが，これも当面凍結状態になる．今年の大会には間に合わない可能性が非常に高い．新規に導入する要素をあきらめれば11月くらいには完成するかもしれないが，それでは作る意味ないしなあ．なんとかこまめに設計を進められないものか．

Velocity measurement with the Kojimouse7 encoder

I received a youtube message from a mouser about the encoder of Kojimouse7. I want to answer the question in this blog so that we share the technique to estimate velocity of a mouse with other mousers.

Kojimouse7 has two sets of a spur gear with 8 holes and a photo reflector. The processor counts the edges of the holes while the wheel is rotating in order to measure the speed of the wheel. It can detect 2 edges for a hole, so, the resolution of this encoder is 16 per revolution. Since my mouse is controlled based on the 1 milisecond periodic interrupt, that low resolution encoder doesn't give enough precision for the instantaneous velocity.

It is almost impossible for a mouse to run smoothly only with the encoder. However, 100 ms average gives a comparatively precise velocity. In this case, the problem is that the obtained velocity is past information, which is a velocity of the mouse approximately 50 ms before.

In order to compensate the delay, Kojimouse7 uses acceleration sensor. Although an acceleration sensor is not good at measuring precise velocity in the long time scale due to the accumulation of errors with time, the integral of the acceleration in very short period gives the velocity change with good precision. So, accelerometer is very useful to compensate the velocity obtained using the encoder, which is past information. The instantaneous and latest velocity of a mouse is roughly obtained by adding the average of the encoder and the velocity change measured by accelerometer.

In short, Kojimouse7 measures the velocity by means of combining the average velocity obtained by the low resolution encoder and the velocity change measured by the acceleration sensor.

I hope you (readers of this article) understand the method above. Further questions and comments are welcome.

マイクロマウス合宿の申込

  ここで宣伝するのを忘れていましたが，6月9日，10日に第4回目となるマイクロマウス合宿が予定されています．詳細は案内ページをご覧ください．（最近ごたごたがあって関西支部のページが別のサーバーへ移動しています．今後再び移動になる見込です．）

  申込締切は5月12日（明日）ですので，参加希望の方は上記リンク先のページに従って担当者にメールを送ってください．
追記：締切を少し遅れても受け付けてもらえそうなので，多少遅れても構いませんので参加希望の方は申込メールをしましょう．

  話変わって，最近何かをgoogle検索していて偶然公開日直後に見つけた記事． 記事を書く人が実際に作ってその難しさと面白さを体験しながらの連載というのは良いですねえ．