copyright nti ag / linmot seminar2002_reglertuning-v1.0.ppt 1 6. tuning of a position controller 6.1...

Copyright NTI AG / LinMot Seminar2002_Reglertuning-V1.0.ppt 1

6. Tuning of a position controller

6.1 Evaluation of the position control

6.2 Components of a industrial position controller

6.3 Set-up and tuning of a position control


6.1 Evaluation of a position control

t

s

t

s 1

2

t

s

Overshooting, undershooting, Oscillation

Pull–in error External disturbance

Static positioning error

t

s

Following error

Motor erreicht Endposition, zeigt aber grössere Abweichung während der Uebergangsphase.

3

Overshooting (1), undershooting (2),Oscillation (3)


6.2 Industrial position controller

FF Acceleration(Feed Forward Acceleration)


Current Offset(Force Offset)


FF Deceleration(Feed Forward Deceleration


FF Friction(Feed Forward Friction)


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-

FilterP

D

I Current

Maximal Current(Maximal Force)

Curve

1ms+mLoad

ms Masse MotormLoad Masse Last

F v sa

Overview of an industrial positioncontroller.

Separation in different blocks: a) ‚limitation of requirements‘ b) ‚Applikation knowledge‘ c) PID-controller d) Mechanical components

b

a

a

b

b

b

d

c

c

c

dd

actual-Position

cf

Required position


6.3 Set-up and tuning

0.) Configuration and Default-values

1.) Generation of the profiles, limit v and a max (filter) avoid overloading

2.) Calculation of the Feedforward-Parameter „application knowledge“

3.) Tuning of the PID-Parameter (if needed)

Example

• Horizontal stroke 140 mm • mass of X-axes 4 kg • friction ?

Because the demonstration unit is not secured power will be reduced by 50 % !


6.3 Configuration

Selection of motor

Controller-Parameter

Selection of max a and v filter

Profiles


6.3 Set-up of the a v Filter (1)





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-

Required position

Filter

P

D

I Current


Curve

1ms+mLoad


F v sa

b

a

a

b

b

b

d

c

c

c

dd

actual-Position

cf





Control parameter P=1,5 D= 5 I=0

Feedforward FFfriction= 0 FFaccel=0 FFdec=0

Filter amax= 300 m/s2 vmax=5 m/s

Anforderung an den Motor sind zu gross! Der Antrieb kann der Sollkurve nicht folgen und zeigt ein ‚unkontrolliertes‘ Verhalten.

No a v limitation.





Filter amax= 24 m/s2 vmax=1,3 m/s

Calculation of the av filter based on the data sheet - vmax = 1.3 m/s- amax aus a:= Fmax/ m = 120N / 5kg

Figures from the datasheet about vmax und Fmax are based on v=0 m/s !





Filter amax= 14 m/s2 vmax=0.7 m/s

Calculation of the filter parameter with LinMot Designer

Still some following errors during acceleration and deceleration Feedforward Parameter


6.3 set-up of the Feedforward-Parameter (1)









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-

Filter

P

D

I Current


Curve

1ms+mLoad


F v sa

b

a

a

b

b

b

d

c

c

c

dd

actual-Position

cf



Required position





Vorfilter amax= 14 m/s2 vmax=0.7 m/s

Feedforward parameters calculated based on the formula (or use the tool which is integrated in LinMot Talk):

FFacc/dec:= Masse/Motorkraftkonstante := 5000g / 40N/A = 125

Following error during acceleration ? Friczton?











++

-

Filter

P

D

I Current


Curve

1ms+mLoad


F v sa

b

a

a

b

b

b

d

c

c

c

dd

Ist-Position

cf

F:= cf * Icf Motor force constant [N/A]



Required position



Control parameter P=0 D= 0 I=0



Hint: Set P and D-factors to 0 . Make a step movement and increase the feedforward FFfriction parameter until curves fit


Feedforward FFfriction= 0.42 A FFaccel=125 FFdec=125


now the friction can be calculated backward:

FFfriction=: cf * FFfriction = 40N/A * 0.42A = 16,8 N



Control parameter P=1.5 D= 5 I=0



Moved mass can change during the movement cycle (gripper picks and places payload).

In most application not a real problem

In critical application it may be neccessary to adapt the parameters on the fly

Optimized to : Mass:= 5 kg Increased mass: 5 kg + 1 kg = 6 Kg


6.3 Tuning of the PID-Parameter (1)

Control parameter P=1.5 D= 5 I=0



Higher P- and D-factors increase the performance regarding external disturbances.




External disturbtion


6.3 Tuning of the PID-Parameter (2)










Static positioning errors can be reduced with higher P-Factors ....

Static positioning errors can be eliminated with the I-factor.(use I factor only if needed because I-factor may make the system instabel.


6.3. Tuning / evaluation of current limits

Controller parameters

P=3 D= 10 I=50



Evaluating motors currents we see the 3 A limit is not exceeded.

The calculation based in the LinMot Designer shows that the power dissipation requirement is about 6 W and therefore well within the 37 W or 133W (with fan) dissipation capabilities.

copyright nti ag / linmot seminar2002_reglertuning-v1.0.ppt 1 6. tuning of a position controller 6.1...

Documents

position slide

position filter p d

position control slide

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position control t s

max filter

s masse motor

v limitation