math/geometry for stepper timing

goodmonring,

math in the workplace? who'd a thought.

i have a tape reel system where a drive reel is controlled by a stepper and pulls tape forward wrapping it around itself.

So as it wraps, the diameter increases, and the time it takes to pull decreases

I can calculate the change in diameter, which i have an equation for

so now i need to calculate the change in the amount of time to have the stepper on for to achieve the same pull.

the only problem is this is 200 dollar tape, and i cant run through reels to determine this based on experimental data...

so knowing the start and end diameter,
the distance i need to pull,
the thickness of the tape
the diameter as it changes
how long it takes to pull currently at my current diameter,...
is there anyway anyone can help?

i feel like this should be simple

The time will depend on the speed at which you are pulling. If you know the length of tape required and the speed, then the time is length divided by speed.

Steve Bailey said:

The time will depend on the speed at which you are pulling. If you know the length of tape required and the speed, then the time is length divided by speed.

Click to expand...

The motor speed and pull length are unchanging... but the speed at which the tape is pulled is not... thank you. i knew it was simple, just couldnt wrap my head around it.

By "speed" I mean the linear speed of the tape, not the RPM of the reel. Also, you will need to factor in accel/decel if you are starting and stopping at zero speed.

Please try to find a way you can measure the tension of the tape,
lets suppose the diameter is 100 the circumference will be Pi*diam.
and the speed is 0.1
now you now the length/circle that gives number of revs in 1 second.
as stepper has 200 steps the time will be number / 200

You didn't really specify what the goal here is - or at least it wasn't very clear to me.

1. Is it to drive the stepper motor periodically making the tape move a fixed distance each time it is driven?

2. Is it to continously wind the tape and keep the tape speed constant by varying the stepper speed?


It seems you've come to the understanding that every 1 revolution your roll diameter is going to increase by 1 thickness of the tape then the above goals are achieved as follows.

1.# of steps to drive the motor = initial number of steps * (initial diameter/current diameter). If you're driving the stepper motor indirectly you will need to account for acceleration/deceleration as these are not a linear relationship.

2.step frequencey = initial step frequency * (initial diameter/current diameter)

in both cases you see that as the diameter of the tape roll grows, you will require less steps to move the same distance, or more time in between steps to achieve the same speed.

Hope this helps