Re: [CAD_CAM_EDM_DRO] Re: deskcnc servo driver

With servo controls how does the software know the machine has reached
it commanded position if it starts to lag behind? I understand that the
servo control knows that the motor is behind but if the pc sends the
next command and it hasn't reached it's destination from the previous
command what happens?

I guess Geckos will only allow 125 step lag before faulting. Is this
really a problem?

Greg

> The step and direction are interpreted as absolute position
> commands. Rather than directly cogging a stepper motor, they are
> used to command a servo control loop that powers the servo motor. The
> actual position as measured with an encoder is compared to that which
> has been commanded by the step and direction signals, and any static
> deviation is opposed by the power of the servo motor power supply.
>
> If the "out of position" is more than the preset tolerance (static or
> dynamic), the driver will fault, and no additional motion will be
> permitted. All axis drives can be wired together to signal each
> other in the event of a servo fault on any axis.
>
> With an open loop stepper system, there is no encoder feedback and
> the position reliability is only assured by using a powerful motor
> and limiting the speed so that no steps are missed.
>
> Fred Smith - IMService