Re: [CAD_CAM_EDM_DRO] How do you compare steppers to servos

Hi,

Not only that, but the integral component of the control loop will also
increase the correction force as the error persists over time.

Cheers,

Peter

On 27/02/2011 1:03 PM, Jon Elson wrote:
> Les Newell wrote:
>>
>>> A servo, if you put an arm on it, is probably less capable of holding an
>>> exact position, as the encoder would sense motion and try to drive in
>>> the opposite direction to correct it, but it would be confused as to how
>>> MUCH to drive it.
>>>
>>
>> Not really. The drive system knows that if the motor is only one encoder
>> count out, it probably doesn't need to apply much torque to return to
>> center, whereas if you are lots of encoder counts out then you need to
>> apply more power. Integral helps overcome steady state loads.
>>
>>
> Yes, exactly. The error (commanded position minus actual position) is
> measured perhaps
> a thousand times a second and the amount of effort to restore the
> position to zero error
> is sent to the drive. Increasing error commands increasing torque,
> decreasing error commands
> less torque. A properly tuned servo will strongly resist deflections
> from commanded position,
> and can be so stiff you'd think there's a brake on the motor. The
> tuning of the servo control loop
> is so that it WON'T be "confused", but will always apply a controlled
> and optimum amount of
> torque to resist any outside forces.
>
> Jon
>
>
>
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