Sintonia Manual Kinetix6000

8/13/2019 Sintonia Manual Kinetix6000

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Copyright 2008 Rockwell Automation, Inc. All rights reserved.

Manually Tuning a

Servo Axis in a Logix5000 Motion System


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Copyright 2008 Rockwell Automation, Inc. All rights reserved. 3

Motion Applications Overview

High performance is required:

High speed

High accuracy Repeatability

System has been properly sized and applied:

Load to motor inertia ratio in acceptable range

Motion controller/drives can perform required tasks

Machine was properly built::

Compliance and machine resonance minimized

Quality gearboxes and actuators/guides chosen


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Inertia

Inertia is important for the following reasons:

Effect on dither in steady state AND in motion

Effect on all other tuning calculations

As inertia increases, gains are increased (scaling)

Drive quantization increases

Causes high frequency noise/heat in kHz of drive update

Requires a notch filter, but doesnt eliminate (cascades) Compliance and backlash issues made worse by high inertia

Why does a high resolution encoder help?

Dither distance is reduced

More information comes back (higher BW) per drive update


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Tuning Terminology

Loop Pgain can do most of the work, but not all

Use Integrals to help close the steady state error

Whether standing still or at constant speed Use velocity Igain if speed is crucial

Use position Igain if steady-state position is crucial

Use velocity Igain if path is important (this works)

Use Feed Forward values if following a path only Velocity(ff) for constant speed portion Acceleration(ff) for blending velocities


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Tuning Terminology


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Tuning Terminology

Output filters High integral gains can lead to low speed instability

High derivative gains can lead to high speed instability

Torque offset Compensation for vertical applications.

Requires bi-directional tuning

Friction compensation Used when not coming into end point tolerance due to stiction


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Basic Servo Loop Diagram


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Ziegler-Nichols Method to Tune a Closed-Loop

Ziegler-Nichols method of tuning for a closed control loop Determines ultimate gain

Determines ulltimate period

Requires the following steps Create an instability on the control loop

Continue decreasing the gain until a stable response is reached (do not want thesystem to be completely damped)

Tip: ZieglerTip: Ziegler--Nichols method recommended for schemes based onNichols method recommended for schemes based onproportional control. The value of gain should be 1/2 to 1/3 theproportional control. The value of gain should be 1/2 to 1/3 the

ultimate gain to obtain 1/4 wave response curve.ultimate gain to obtain 1/4 wave response curve.


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Over-damped

Ziegler-Nichols Method to Tune a Closed-Loop

Under-damped

Critically damped


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(3) Main Types of Motion Applications

Point

to Point

Pick-Place

Packaging

Cut to Length

Tracking

(Follower)

Winding

Flying Shear

Web

Constant

Speed

Conveyor

Line Shaft

Crank

Type 1 Type 2 Type 3

Tip:Tip: AutotuneAutotune works well if the inertia mismatch is less than 10:1. It isworks well if the inertia mismatch is less than 10:1. It isbest to manually tune when the inertia mismatch exceeds 10:1.best to manually tune when the inertia mismatch exceeds 10:1.


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Compliant Load Tuning Tips

For resonance below velocity loop bandwidth: Natural resonance of machine is within drives velocity BW

Must use BW reduction to detune (today), reduce Vel BW


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Additional Manual Tuning Tips

Start out with box settings

Use the RSLogix 5000 trend feature to monitor the motor position error.

Set the velocity and acceleration feedforward parameters to 100% in thegains tab.

Run the required motion profile.

If necessary, gradually increase the torque/force scaling value until the

position error becomes close to zero.


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Documents

Sintonia Manual Kinetix6000