Re: Re: G201 modifications/update(braking)
Posted by
ballendo@y...
on 2000-10-30 16:53:57 UTC
Jon,
I only use the braking mode of a drive when things are going (very)
wrong! In the case of a servo, it is quite useful to have a means to
brake.
With a stepper, I just disable the link (in hardware) from the pulse
train to the drive) and the drive has its' full torque to apply to
whatever "braking" needs to be done! (at least until auto-idle kicks
in from the lack of pulse train) It may "slip', but at this point
position is NOT the main concern.
I see many designs which IMO do not "appropriately" deal with an
emergency stop! Just "killing" the drives may be a recipe for
disaster!! Any machine designer needs to REALLY "think through" what
can go wrong and what will be the likely actions of BOTH machine AND
operator!!
And take/make correct actions to deal with this.
Ballendo
'********************************************************************
ballendo@y... wrote:
braking. If you have a large machine, with a lot of moving mass, it
can
continue traveling quite a distance if the drive is simply shut off,
without
a dynamic braking mode. It won't make much difference on a Sherline.
Stepper motors can be easily braked in a controlled manner by
connecting
a braking resistor where the DC power supply normally feeds the
full-bridge
switches (for a bipolar drive). The regenerated voltage from the motor
will be rectified by the freewheeling diodes and fed to the braking
resistor.
Jon Elson
I only use the braking mode of a drive when things are going (very)
wrong! In the case of a servo, it is quite useful to have a means to
brake.
With a stepper, I just disable the link (in hardware) from the pulse
train to the drive) and the drive has its' full torque to apply to
whatever "braking" needs to be done! (at least until auto-idle kicks
in from the lack of pulse train) It may "slip', but at this point
position is NOT the main concern.
I see many designs which IMO do not "appropriately" deal with an
emergency stop! Just "killing" the drives may be a recipe for
disaster!! Any machine designer needs to REALLY "think through" what
can go wrong and what will be the likely actions of BOTH machine AND
operator!!
And take/make correct actions to deal with this.
Ballendo
'********************************************************************
ballendo@y... wrote:
> Ballendo,This is not necessarily true. Stepper motors can take advantage of
>
> The G201 is a STEPPER drive. No fault indicator. No "braking"
> necessary. Duh. Sorry list.
braking. If you have a large machine, with a lot of moving mass, it
can
continue traveling quite a distance if the drive is simply shut off,
without
a dynamic braking mode. It won't make much difference on a Sherline.
Stepper motors can be easily braked in a controlled manner by
connecting
a braking resistor where the DC power supply normally feeds the
full-bridge
switches (for a bipolar drive). The regenerated voltage from the motor
will be rectified by the freewheeling diodes and fed to the braking
resistor.
Jon Elson