Re: [CAD_CAM_EDM_DRO] Re: +/- 10V Gecko

mariss92705@... wrote:

> Hi,
>
> Servo amplifiers can operate in velocity mode, torque mode and
> sometimes IR compensated mode as well. The mode determines how the
> control input (+/- 10 volts) is interpreted.
>
> Velocity Mode:
>
> In velocity mode the amplifier outputs a VOLTAGE that is proportional
> to the control input. It is called "velocity mode" because the motor
> speed is roughly proportional to the voltage applied to it. This is
> the same mode that audio amplifiers use.
>
> Torque Mode:
>
> In torque mode the amplifier outputs a CURRENT that is proportional
> to the control input. It is called "torque mode" because motor torque
> is proportional to the current passing thru it. By analogy, a car
> engine is a torque mode amplifier and the gas pedal is the control
> input.
>
> IR Compensated Mode:
>
> This is a variation of the velocity mode. The motor SPEED is
> proportional to the control input. Its purpose is to operate as a
> regulated speed control. Motor load (current) is sensed and summed
> with the input as positive feedback. The right amount of feedback
> will increase the output voltage just enough to compensate motor RPM
> drop with load. This makes the motor speed independent of load
> (within 1%).
>
> Most servo loops use the amplifier in the TORQUE mode. This mode
> gives the widest closed loop bandwidth (lowest response time)and is
> more stable than servo loops using VELOCITY mode amplifiers.

I always thought that a velocity servo used a tachometer or other actual
measurement of velocity to force movement to equal the commanded
velocity. Your velocity amp, as described above, is simply a voltage
amplifier. Motor velocity in a highly dynamic servo motion system may
not be anywhere near applied voltage, due to motor inductance and resistance.
So, you have to sense the current and the actual velocity to get all the info
needed for tight control.

Most servo amps (Copley, Servo Dynamics, Kollmorgen, etc.) do it
as I described.

Jon