Electrical Engineering - hi help me out guys

Author

hi help me out guys

suchi_84@yahoo.com

2006-03-13, 9:21 am

Hi folks,
I need a help. As I am basically an electrical engineer I have
succeeded in micro-stepping a stepper motor by 128 micro steps of step
angle 1.8degrees which mean it can at one instance move by as small as
0.014degrees. Well the problem now is that I need to convert this
angular motion into its equivalent linear motion(i micron) so that I
get a micron level motion. As not many were able to help me out in this
regard, I started browsing the net for some way of achieving this
conversion.
I hit upon something on which I
need your help. In a compact disk there is a rack and pinion
arrangement which is capable of moving by 0.5micron (maybe, 0.05
micron...me not pretty sure). There is an optical arrangement of infra
red beam which runs on this rack and pinion and which is reflect on to
the ridges of a cd so as to store data in cd's. as the distance
between adjacent ridges of cd is in the order of 0.5 micron(or maybe
0.05 micron) so this rack and pinion must support such minute movement
of 1 micron that is required in my project,I feel. Cant this apparatus
satisfy my need? Respond as soon as possible friends
suchi

ehsjr

2006-03-14, 2:21 am

suchi_84@yahoo.com wrote:
> Hi folks,
> I need a help. As I am basically an electrical engineer I have
> succeeded in micro-stepping a stepper motor by 128 micro steps of step
> angle 1.8degrees which mean it can at one instance move by as small as
> 0.014degrees. Well the problem now is that I need to convert this
> angular motion into its equivalent linear motion(i micron) so that I
> get a micron level motion. As not many were able to help me out in this
> regard, I started browsing the net for some way of achieving this
> conversion.
> I hit upon something on which I
> need your help. In a compact disk there is a rack and pinion
> arrangement which is capable of moving by 0.5micron (maybe, 0.05
> micron...me not pretty sure). There is an optical arrangement of infra
> red beam which runs on this rack and pinion and which is reflect on to
> the ridges of a cd so as to store data in cd's. as the distance
> between adjacent ridges of cd is in the order of 0.5 micron(or maybe
> 0.05 micron) so this rack and pinion must support such minute movement
> of 1 micron that is required in my project,I feel. Cant this apparatus
> satisfy my need? Respond as soon as possible friends
> suchi
>

Since you have not stated your needs, how can we tell you
if the CD rack and pinion will satisfy them?

You want to move *what* 1 micron? An ocean liner?
An amoeba? A surgical instrument?

*Must* you use a stepper motor? If so, why?

How will you determine that 1 micron of motion has
occurred? What is the feedback loop?

And on and on. 90 percent of your answer will be
found in asking the right question.

Ed

suchi_84@yahoo.com

2006-03-14, 6:21 am

hi, thanks for replying.. We need to move the tip of a laser beam thro
a micron. something similar to a cd drive optical lens mechanism. the
angular motion is converted into linear motion by a rack n pinion and
this laser tip/diode moves on the rack n pinion.

we planned to use a stepper as we could microstep it to a small degree
and there are no big probs like overshoot in a stepper..

feedback loop is gonna be an optical grating arrangement and a pulse
counter. or an encoder.

hope i have given the reqd details.

Roy L. Fuchs

2006-03-14, 8:21 am

On 14 Mar 2006 01:22:49 -0800, suchi_84@yahoo.com Gave us:

>hi, thanks for replying.. We need to move the tip of a laser beam thro
>a micron. something similar to a cd drive optical lens mechanism. the
>angular motion is converted into linear motion by a rack n pinion and
>this laser tip/diode moves on the rack n pinion.
>
>we planned to use a stepper as we could microstep it to a small degree
>and there are no big probs like overshoot in a stepper..
>
>feedback loop is gonna be an optical grating arrangement and a pulse
>counter. or an encoder.
>
>hope i have given the reqd details.

The pitch of the screw for rack and pinion setup will play into this
and is needed information. The pitch of the screw determines the
traverse the rack makes per screw revolution.

With that known, you should be able to determine how much of one
revolution is required to make a given amount of linear motion.

Roy L. Fuchs

2006-03-14, 8:21 am

On Tue, 14 Mar 2006 11:32:17 GMT, Roy L. Fuchs
<roylfuchs@urfargingicehole.org> Gave us:

> The pitch of the screw for rack and pinion setup will play into this
>and is needed information. The pitch of the screw determines the
>traverse the rack makes per screw revolution.
>
> With that known, you should be able to determine how much of one
>revolution is required to make a given amount of linear motion.

An added note. The rack and pinion setup must have very little
backlash in it, or said backlash must be 100% known or your system
will not behave as you might expect, ie a reversal of direction will
have a gap in shaft rotation before the laser head reverses direction.

ehsjr

2006-03-14, 2:21 pm

suchi_84@yahoo.com wrote:
> hi, thanks for replying.. We need to move the tip of a laser beam thro
> a micron. something similar to a cd drive optical lens mechanism. the
> angular motion is converted into linear motion by a rack n pinion and
> this laser tip/diode moves on the rack n pinion.
>
> we planned to use a stepper as we could microstep it to a small degree
> and there are no big probs like overshoot in a stepper..
>
> feedback loop is gonna be an optical grating arrangement and a pulse
> counter. or an encoder.
>
> hope i have given the reqd details.
>

No disrespect - but I'm not going to play this game.
You don't seem to know enough about what you are trying
to do. Go here as a starting point:
http://www.engineeringtalk.com/news/hea/hea131.html

Read up on linear actuators, VCM - maybe hire a consultant.
You haven't mentioned accuracy, repeatability, force,
acceleration etc - stuff you have to consider.

Ed

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