Re: [Phys-l] The "why" questions

[brian whatcott <betwys1@sbcglobal.net>]

On 11/30/2010 11:06 AM, Bill Nettles wrote:
> [Bill Nettles]
> Now that's an interesting project. I do have a few questions.
> 1) In a system of stepper motors which provide definite accelerations independent of the mass which was being accelerated, did the power consumption of the motors depend on the mass being accelerated?
> 2) Were there situations in which the you had to get motors capable of larger torques because the first motors you used wouldn't provide the accelerations required?  If so, wouldn't it be reasonable to say that you couldn't get "ma" because the motor was incapable of producing "torque/r" when connected to that m? In other words, without the ability to produce sufficient torque you can't get the correct acceleration?
>
> __
1) No stepper motor drive offers acceleration independent of any load 
magnitude.
In systems where steppers run open loop (without output shaft 
position/velocity/acceleration feedback), it is necessary to limit 
angular acceleration demands to those which the motor/load combination 
can handle without losing steps.
In that sort of system, a sufficiently small acceleration demand will 
possibly lead to a steppy response, unless efforts are made to drive the 
motor(s) in a rather un-step-motor like mode.
You would expect greater agility with high loads to require greater power.

2) Not sure of the merits of your argument here, but sufficient drive 
requires sufficient torque, no doubt.

Brian W