how do i regulate the voltage/current from the MID 7654

[DuncW]

I am trying to control a linear motor using flex motion and the MID 7654 power drive, however there are variuos discprencies between what should happen and what is happening:

1) I have configured AXIS one as an open loop stepper, i have specified a target postion (1000) counts, Max reports movement complete however the power amplifier is outputing 50 volts as soon as motion is started and after it has finished. ( should this value not vary with varying speed and positions, i have tried and it does not ???)

2) If configuring the axis as a servo loop and specifying KP as zero, i still get a max output, should this not be zero also.

3) Follow intiialisation i get maximum output from the power amp. I realise the ax
is must be energised and a holding torque applied, but this is causing the motor to shoot off ! why ??
Any help or advice would be much appreciated !!!!

[Yusuf C]

Hello,

MID 7654 is a servo amplifier and will only work with servo motors. Do not expect anything reasonable to happen when the axis is configured as a stepper instead of a servo as it's not the intended use.
After you configure the axis as a servo you need to tune the PID loop parameters. Until you do that the current sent to the motor will not be correct and you might see unexpected movement on your axis.
Also make sure the current settings of the amplifier matches the ones in the motor's spec sheet.
Hope this helps!

Regards,

Yusuf C.
Application Engineering
National Instruments

[dazal]

Just a related question. Is there any way to regulate the voltage from the servo amplifier. My servo actuator is rated at 33V and the MID7652 is 48V. Can I adjust the suppoed voltage on labview? There is control limits on the current. What actually controls the supplied current I am pressuming the voltage from the motion control card? So if I can control it I can control the current in the motor.

[GiGe]

You are right that the current is controlled by the voltage from the controller.  The way voltage is controled is by setting the velocity.  The higher the velocity is then the higher the current will be.  I hope that helps

gg

[dazal]

Thanx gg

Right so what about controlling the voltage outputted to the servo from the amplifier. It energises to 48V but I would only want it to supply 33V nominal. The servo amplifier does have DIP switches to set continuous and peak current limits however does this control the voltage output?  I noticed on MAX you can change the voltage limits from _+10V. Woudl this adjustment decrease the supplied voltage by the servo?

Cheers,

Darren

[GiGe]

Hi Darren,

Your right, the dip switches will set the max current.  The voltage setting in max is going to change the voltage output on your motion controller, so that will also then change what is being output from your motion drive. 

GG