I have a motion controller that send a -10/+10V speed signal to a servodrive (the encoder goes from the servomotor to the motion controller).

I wanna know what happens when the motion controller receive a fast stop command from my PLC. Does it automatically send a 0V signal, or does it control the load to zero speed and then send a 0V signal (and probably disable the drive)?

 

Can you borrow an oscilloscope from someone?
That would answer the question for the particular
equipment you have. Set an output to use as a
trigger just before you issue the command.

Regards
cww

 

That depends entirely upon the motion controller in question. In our controllers there are three possible answers to that question depending on how the fast stop is implmented.

1) The fast stop goes to an amp fault input - the amp enable is dropped, voltage command goes to 0. Depending on the amp this counld mean that the motors coast to a stop.
2) A position limit input is set - this means a
controlled fast stop, but the amp does not drop out.
3) A general use input is used - reaction to command depends on programming around that input.

Davis Gentry
Delta Tau Data Systems

 

The acceleration significantly higher than defined for other operation modes (as jog or PTP) is used for fast stop as a rule.

 

It depends on the control. There is no standard
technique that I am aware of. A fast ramp down with an option to disable the drive would probably be best.

 

It, of course, depends on the controller so read the manual or call the manufacturer.

Generally what I want to happen is for the controller to decelerate the axis to zero speed at the max decel rate possible.

 

If your motion controller really issues "speed" signal to servo drive, it is clear that signal will be turned to another polarity for the short period of time. In practice, your motion controller should generate "error position" signal, which value is difference between current and specified positions. In this, realistic case, voltage always will be the same polarity till the moment, when position difference will be smaller, than position tolerance parameter. This is only true, of cause, if motion controller has right transient performance.

Mike Virgiliev.

 

This could be handled any number of ways and this is a good illustration of how a simple question can have a variety of answers.

1.) Does the motion controller have a dedicated "Quick Stop" function in firmware? This is typically the STOP decel used when a limit switch is opened or an ABORT command is issued to the controller (again, if it even has this function)

If indeed it has this function, usually you set a decel rate in a parameter in the controller and the controller constructs a linear decel ramp trajectory and brings the axis to a controlled stop within the capabilities of the PID loop. If excessive following error occurs, the loop typically faults with a Fatal Following Error and the axis then coasts to a stop (usually with catastrophic results)

2.) Is the amplifier a torque (current) mode amplifier or a velocity mode amplifier - this can have a significant affect on how the system is decelerated from the controller (especially if the amplifier enable is controlled by the motion controller or not)

3.) You can also deal with this programatically - i.e. using a general purpose input to trigger a software controlled deceleration of the axis(es) . . . lots of flexibility how this can be handled, do you want to stay on path in a coordinate system or do you not care of the axes each come to a stop along a linear ramp?

Lots of different things to consider - and the answer all depends on the hardware / software / firmware you are using.