Newsgroups: comp.robotics
Path: brunix!uunet!munnari.oz.au!bunyip.cc.uq.oz.au!wyeth
From: wyeth@elec.uq.oz.au (Gordon Wyeth)
Subject: Re: Micro-Mice questions
Message-ID: <wyeth.705643281@s1.elec.uq.oz.au>
Sender: news@bunyip.cc.uq.oz.au (USENET News System)
Organization: Prentice Centre, University of Queensland
References: <1992May5.143855.27347@a.cs.okstate.edu>
Date: Tue, 12 May 1992 04:01:21 GMT
Lines: 81

In <1992May5.143855.27347@a.cs.okstate.edu> rjs@a.cs.okstate.edu (STOLFA ROLAND JOSE) writes:


"|"Ok, I'm bitten by the micro-mice bug...  My wallet may never forgive me...
"|"I went to the ftp site recently sited in OZ and got some of the startup
"|"information (rules, discussion of past events, etc.) and a general
"|"question came up in reguards to the hardware.

"|"For the "typical" first generation mouse (probably in the 2 lbs range),
"|"how much torque would the stepper motors need.  Ie. out of all the
"|"micro-mice that are 2 lbs or less, what is the maximum (average, etc.)
"|"torque that their stepper motors are rated at.

"|"I have found some that are rated as follows, and basically wonder if
"|"these might work for a first generation mouse...

"|"	Model 4017-831
"|"		from Applied Motion Products, Inc.
"|"		     Scotts Valley, CA 95066
"|"		     (sorry, that's all I have)
"|"	Holding Torque		800 g * cm	(11.1 oz.in.)	min
"|"	Detent Torque		60 g * cm	(.83 oz.in)	min

"|"Any help would be appreciated.  BTW, let's face it.  On my kind of budget,
"|"I don't think I am any kind of real threat to anybody at any big-wig school,
"|"so please be generous with the hints/help/etc.  I'm not after _YOUR_ mouse.

Braitenberg vehicles and a micro-mouse? What a busy year you're
gunna have. Me too.

The maths for working out a motor torque for a micro-mouse is
straight forward.

Force = mass x acceleration

You know your mass, but what acceleration do you want? Well,
depending on your tyres and your drive setup your not likely
to get more than about 3m/s/s. If you try to accelerate any
faster than this your tyres will spin. Your mass you specified
as a maximum of ~ 1 kg. 

So the Force = 3 Newtons

Next I assume you are going to gear down your motor some, say
a ratio of N:1. Also your drive wheel has a radius Rw. The
torque required at the drive wheel is

Torque = Force x distance

Torque = 3 x Rw Nm

Now your motor will need only 1/N of that torque because of
your gears. SO....

Torque = 3 x Rw  Nm
		 ------
		   N

Don't forget to specify Rw in metres, and to convert from Nm
to g.cm at the end.

*************************************************************

Please feel free to correct or criticise this. And don't
forget the OzMouse competition is being held in Melbourne,
Australia in Novenber this year. International entries most
welcome.

Cheers


-- 
--------------------------------------
| Gordon Wyeth      Dept of Elec Eng |
|                  Uni of Queensland |
| wyeth@elec.uq.oz.au      Australia |
--
--------------------------------------
| Gordon Wyeth      Dept of Elec Eng |
|                  Uni of Queensland |
| wyeth@elec.uq.oz.au      Australia |
