Optimizing The Pid Controller; How The Control Process Works; Significance And Influence Of The Controller Parameters - Danfoss MCO 305 Operating Instructions Manual

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MCO 305 Operating Instructions

Optimizing the PID Controller

The Testrun explained in the chapter 'PC Software interface' of the APOSS Online help can be used as a tool

to optimize the MCO 305 controller settings, thereby optimizing your system performance. To do that you

only need to know a few things about the control scheme of MCO 305:

The APOSS position controller has two parts:

1. The Setpoint Generator interprets the various positioning commands in APOSS and generates a series of

setpoint positions that eventually ends with the desired position.

Normally, all positioning processes have a trapeze-shaped velocity curve. That means that after a phase

of constant acceleration there is a phase with constant velocity and finally a phase with constant dece-

leration, which ends at the desired target position.

2. The PID controller receives the setpoint positions from the Setpoint Generator and in turn calculates the

speed reference needed for the motor to follow the current setpoint position.

By setting the PID control parameters you can directly influence to what degree and how quickly a

deviation from a theoretical set path (as specified by the setpoint series) should be counteracted.

The following behavior indicate that the control parameters are not optimally adjusted:

Drive vibrates

Drive is loud

Frequent occurrence of position errors

Poor control accuracy

NB!:

The control parameters are load-dependent. Thus the drive must be optimized under the actual

conditions of use.

In exceptional cases it may be necessary to determine various sets of control parameters while working

with heavily changing load conditions and to re-program them in subsequent application programs

depending on the motion process.

The PID control unit of the APOSS motion controller transfers the necessary output frequency via an internal

speed reference to the FC 300. This set value is periodically recalculated with an interval of one millisecond

(interval is programmable by the TIMER parameter). The MCO 305 is by default set with soft 'fit for all'

controller parameters.

MG.33.K2.02 – VLT is a registered Danfoss trademark

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