How to commission TechApp (Technology App) Process Controller

What the TechApp "Process controller" is good for

The TechApp "Process controller" is used to control the torque or force (or any other value) of an axis according to a setpoint given over the fieldbus communication in evaluating an external sensor reflecting the actual value of the desired control signal.

The "process controller" function allows an external variable to be controlled in addition to the operation modes and control types already available in the drive. Thus, the drive can be used for direct, rapid process control. The possible options are, for example, force, pressure or distance control and many more, the feedback value being compensated by the ctrlX DRIVE TechApp directly in the drive. The command value can be preset by an external control, for example.

After "Process controller" control has been activated, the controller output is regulating and causes the process feedback value that was returned to reach the preset command value.

Test setup (typical torque test bench)

Setup and mechanical arrangement - Details of torque sensor attachment

Components and firmware used

In here the following components and firmware are used:

Components, firmware and process controller version

For Engineering the tool ctrlX DRIVE Engineering is used. In here version 01V36.2 is used.

ctrlX DRIVE Engineering version used (01V36.2)

Regulation settings

The regulation settings of both the load and test motor should be made in the usual way with PI gain in velocity loop and checked by means of frequency response diagrams. See as well: Link

Velocity regulation loop settings of load motor

Velocity regulation loop settings of test motor

Installation and activation of TechApp “Process controller”

Go to Technology Function – PLC settings, search for Technology App, select “Process Controller” and load it.

Installation of Technology App “Process Controller”

Take over the retain variables and start automatic reboot

Run the Technology App “Process Controller”!

Parameterize Technology App “Process controller” for constant speed command

Use e.g. Easy Startup Mode to enable both load and test motor drive (set to AF).

First leave the process controller inactivated.

Use e.g. Easy Startup Mode to create a speed command in both the load and the test motor axis, in here it was set to e.g. constant 100 rpm.

Set the analog input and scale it to your needs. In our example 1V equals 10 Nm. Therefor 10 V on the analog input equals 100 Nm.

A small filter time constant of 2 ms is recommended.

Analog input settings in process controller

Analog input settings reflected in normal menu (--> don´t change)

Leave the feedback value generation unfiltered.

Set the command value pre-processing to a high ramp rate (in here e.g. to 10 Nm per ms).

Configure the “Process controller”!

Set the Controller output limitation to proper values, in here 1000 rpm, to not restrict the controller but low enough to prohibit a too high set point. Set the tolerance window for control difference as well to a proper, usually small, window. The integral action time should first be set to a high value like 10000 ms.

Configuration of process controller with high Integral action time

Now activate process control and set a process command (cmd) value, like in here 2.0000. If the analog input is approaching this set point, everything is fine, otherwise deactivate the process control.

Check of proper behavior of process control

If set point is not achieved and thus counter-reacting, invert the control difference.

Now check the reaction in step response. Therefor set the command value from in here in before 2 Nm to 20 Nm (Setpoint 2.0000 to 20.0000).

Step response with high integral action time 10000 --> no overshoot but quite a time needed to get to setpoint

Change integral action time to medium small value like 20 ms and do step response (in here change command value from 2 to 20 Nm (Setpoint 2.0000 to 20.0000)) again.

Configuration of process controller with medium small integral action time 20

Step response with medium small integral action time 20 --> small overshoot but still quite a time needed to get to setpoint

Change integral action time to smaller value like 10 ms and do step response (in here change command value from 2 to 20 Nm (Setpoint 2.0000 to 20.0000)) again.

Configuration of process controller with medium small integral action time 10

Step response with small integral action time 10 --> higher overshoot not exceeding 1,4-times setpoint and small time needed to get to setpoint

In here this is thought to be good enough from the settings.

Parameterize TechApp “Process controller” for changing speed command

If the speed command is no longer set stable but is changing, in order that no errors show up, the following recommendations should be applied.

Set velocity control loop monitoring of load motor to “Not active”

Now by means of e.g. Easy startup mode the test motor axis can be made run alternating in speed. But still the process controller should control the torque to keep on to the set point.

In here the setpoint is set to “12 Nm” (Setpoint 12.0000).

Changing speed of test motor but trying to keep the torque constant at 12 Nm

In order to get better results the process controller regulation settings were changed.

Process controller regulation settings changed

Changing speed of test motor but trying to keep the torque constant at 12 Nm with changed process controller regulation settings settings

This behavior was acceptable for the process needed.