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Micromouse Topics => Hardware => Topic started by: exapod on September 19, 2013, 12:47:27 AM

Title: Help with my first mouse
Post by: exapod on September 19, 2013, 12:47:27 AM
Finally i have some time to spend on my first micromouse but i have some doubts and questions.
I will be using the fauhaber 1717 with 16 line per rev encoder and using the 4 wheel configuration.
What is a better distance from the floor: 1,5 mm or 2mm?
Does someone knows where to buy 17 mm mini-z wheel?So the ending wheel will be 22mm.
In your opinion a resolution of 0.3 mm on the floor is enough to control a robot? i will also mount a gyro.
Should i mount an accelerometer to help the resolution or it is just impossible to use in such application?
With this low resolution you reccomend using 4 or 6 sensors?
This question is for the admin, i read that for your new mouse you have a gear ratio of 11:40, that is 3.63636363... how do you deal with this numbers? You use float or fixed point integer?
Thank you for the help and sorry for all this question :D
Title: Re: Help with my first mouse
Post by: Green on September 19, 2013, 01:02:47 AM
   16 lines for 1717 is terribly low to keep track of the speed unless you use accelerometer to monitor the velocity and use low resolution to count distance only.
1.5 is better,  not too much big difference with 2mm. It's better if you can make the mouse MUCH lighter instead.
I never seen 17mm wheel. You will have to make you own wheel either by lathe/CNC from a POM/acetal or high resolution 3D printing.
what does 0.3mm resolution mean?
gyro is required for a 4 wheel mouse otherwise the mouse won't be able to turn with only encoder.
Accelerometer is needed if you stick on low resolution encoder. The winner of half size micromouse, Kojima, use low resolution encoder accelerometer combo for his mouse, although it is not as comfortable as high resolution encoder to use.
Now 4 sensors and 6 sensors worked same for me. side sensor isn't that useful if you can tune your mouse well. Besides, less sensor equals less sensor pulsing time.

As of the gear ratio. I was just trying to get a little bit higher torque than my old mouse with 12:40 gear ratio, kinda came out of random, haha. It also helped me to lower the CG without making 2 wheels too close. The gear ratio won't really get involve into computation when mouse is build. I only use encoder counts per cell instead of caring the gear ratio and wheel size.
Title: Re: Help with my first mouse
Post by: exapod on September 19, 2013, 01:30:44 AM
0,3 mm resolution means that if i read the encoder X4 and with a gear ratio of 1:4 i will have a count every 0.3 mm.
The 17 mm wheel is without tyres, i've read that some mice have 22 mm diameter wheels with the tyres and i don't know where to buy them, the mini z wheels that i have are 20 mm without the tyres and 25 mm with the tyres.
I will mount an accelerometer somewhere, do you have some information on how to use the two sensors (accelerometer and gyro) to control a mouse ? I guess that i have to integrate the acceleration to get the speed and in a straight trajectory is simple, but when the mouse is turning things get a little complicated... do you know someone else who is using the accelerometer?
Title: Re: Help with my first mouse
Post by: Green on September 20, 2013, 06:52:46 PM
current the resolution per mm for my new mouse is 97 counts per mm
They customized wheel on their own for those who had 22mm diameter wheel.
If you maintain of using low resolution encoder, accelerometer will be your feedback for forward motion control and gyro will be the feedback for rotational feedback for rotational movement.
So far I only know Kojima use accelerometer as forward speed feedback since he only has low resolution encoder only to count distance.