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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
Copyright NTI AG / LinMot Seminar2002_Reglertuning-V1.0.ppt 2
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)
Copyright NTI AG / LinMot Seminar2002_Reglertuning-V1.0.ppt 3
6.2 Industrial position controller
FF Acceleration(Feed Forward Acceleration)
FF Acceleration(Feed Forward Acceleration)
Current Offset(Force Offset)
Current Offset(Force Offset)
FF Deceleration(Feed Forward Deceleration
FF Deceleration(Feed Forward Deceleration
FF Friction(Feed Forward Friction)
FF Friction(Feed Forward Friction)
++
-
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
Copyright NTI AG / LinMot Seminar2002_Reglertuning-V1.0.ppt 4
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 % !
Copyright NTI AG / LinMot Seminar2002_Reglertuning-V1.0.ppt 5
6.3 Configuration
Selection of motor
Controller-Parameter
Selection of max a and v filter
Profiles
Copyright NTI AG / LinMot Seminar2002_Reglertuning-V1.0.ppt 6
6.3 Set-up of the a v Filter (1)
FF Acceleration(Feed Forward Acceleration)
Current Offset(Force Offset)
FF Deceleration(Feed Forward Deceleration
FF Friction(Feed Forward Friction)
++
-
Required position
Filter
P
D
I Current
Maximal Current(Maximal Force)
Curve
1ms+mLoad
ms Masse MotormLoad Masse Last
F v sa
b
a
a
b
b
b
d
c
c
c
dd
actual-Position
cf
Overview of an industrial positioncontroller.
Separation in different blocks: a) ‚limitation of requirements‘ b) ‚Applikation knowledge‘ c) PID-controller d) Mechanical components
Copyright NTI AG / LinMot Seminar2002_Reglertuning-V1.0.ppt 7
6.3 Set-up of the a v Filter (2)
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.
Copyright NTI AG / LinMot Seminar2002_Reglertuning-V1.0.ppt 8
6.3 Set-up of the a v Filter (3)
Control parameter P=1,5 D= 5 I=0
Feedforward FFfriction= 0 FFaccel=0 FFdec=0
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 !
Copyright NTI AG / LinMot Seminar2002_Reglertuning-V1.0.ppt 9
6.3 Set-up of the a v Filter (4)
Control parameter P=1,5 D= 5 I=0
Feedforward FFfriction= 0 FFaccel=0 FFdec=0
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
Copyright NTI AG / LinMot Seminar2002_Reglertuning-V1.0.ppt 10
6.3 set-up of the Feedforward-Parameter (1)
FF Acceleration(Feed Forward Acceleration)
FF Acceleration(Feed Forward Acceleration)
Current Offset(Force Offset)
Current Offset(Force Offset)
FF Deceleration(Feed Forward Deceleration
FF Deceleration(Feed Forward Deceleration
FF Friction(Feed Forward Friction)
FF Friction(Feed Forward Friction)
++
-
Filter
P
D
I Current
Maximal Current(Maximal Force)
Curve
1ms+mLoad
ms Masse MotormLoad Masse Last
F v sa
b
a
a
b
b
b
d
c
c
c
dd
actual-Position
cf
Overview of an industrial positioncontroller.
Separation in different blocks: a) ‚limitation of requirements‘ b) ‚Applikation knowledge‘ c) PID-controller d) Mechanical components
Required position
Copyright NTI AG / LinMot Seminar2002_Reglertuning-V1.0.ppt 11
6.3 set-up of the Feedforward-Parameter (2)
Control parameter P=1,5 D= 5 I=0
Feedforward FFfriction= 0 FFaccel=125 FFdec=125
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?
Copyright NTI AG / LinMot Seminar2002_Reglertuning-V1.0.ppt 12
6.3 set-up of the Feedforward-Parameter (3)
FF Acceleration(Feed Forward Acceleration)
FF Acceleration(Feed Forward Acceleration)
Current Offset(Force Offset)
Current Offset(Force Offset)
FF Deceleration(Feed Forward Deceleration
FF Deceleration(Feed Forward Deceleration
FF Friction(Feed Forward Friction)
FF Friction(Feed Forward Friction)
++
-
Filter
P
D
I Current
Maximal Current(Maximal Force)
Curve
1ms+mLoad
ms Masse MotormLoad Masse Last
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]
Overview of an industrial positioncontroller.
Separation in different blocks: a) ‚limitation of requirements‘ b) ‚Applikation knowledge‘ c) PID-controller d) Mechanical components
Required position
Copyright NTI AG / LinMot Seminar2002_Reglertuning-V1.0.ppt 13
6.3 set-up of the Feedforward-Parameter (4)
Control parameter P=0 D= 0 I=0
Feedforward FFfriction= 0 FFaccel=125 FFdec=125
Filter amax= 14 m/s2 vmax=0.7 m/s
Hint: Set P and D-factors to 0 . Make a step movement and increase the feedforward FFfriction parameter until curves fit
Control parameter P=0 D= 0 I=0
Feedforward FFfriction= 0.42 A FFaccel=125 FFdec=125
Filter amax= 14 m/s2 vmax=0.7 m/s
now the friction can be calculated backward:
FFfriction=: cf * FFfriction = 40N/A * 0.42A = 16,8 N
Copyright NTI AG / LinMot Seminar2002_Reglertuning-V1.0.ppt 14
6.3 set-up of the Feedforward-Parameter (5)
Control parameter P=1.5 D= 5 I=0
Feedforward FFfriction= 0.42 A FFaccel=125 FFdec=125
Filter amax= 14 m/s2 vmax=0.7 m/s
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
Copyright NTI AG / LinMot Seminar2002_Reglertuning-V1.0.ppt 15
6.3 Tuning of the PID-Parameter (1)
Control parameter P=1.5 D= 5 I=0
Feedforward FFfriction= 0.42 A FFaccel=125 FFdec=125
Vorfilter amax= 14 m/s2 vmax=0.7 m/s
Higher P- and D-factors increase the performance regarding external disturbances.
Control parameter P=6 D= 20 I=0
Feedforward FFfriction= 0.42 A FFaccel=125 FFdec=125
Vorfilter amax= 14 m/s2 vmax=0.7 m/s
External disturbtion
Copyright NTI AG / LinMot Seminar2002_Reglertuning-V1.0.ppt 16
6.3 Tuning of the PID-Parameter (2)
Control parameter P=6 D= 20 I=0
Feedforward FFfriction= 0.42 A FFaccel=125 FFdec=125
Filter amax= 14 m/s2 vmax=0.7 m/s
Control parameter P=3 D= 10 I=0
Feedforward FFfriction= 0.42 A FFaccel=125 FFdec=125
Filter amax= 14 m/s2 vmax=0.7 m/s
Control parameter P=6 D= 20 I=50
Feedforward FFfriction= 0.42 A FFaccel=125 FFdec=125
Filter amax= 14 m/s2 vmax=0.7 m/s
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.
Copyright NTI AG / LinMot Seminar2002_Reglertuning-V1.0.ppt 17
6.3. Tuning / evaluation of current limits
Controller parameters
P=3 D= 10 I=50
Feedforward FFfriction= 0.42 A FFaccel=125 FFdec=125
Filter amax= 14 m/s2 vmax=0.7 m/s
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.
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