Appendix D Optimising The Dynamic Performance; Speed-Loop Parameters; Adjusting The Speed-Loop Gains - Control Techniques M'Ax 403 User Manual

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Appendix D Optimising the
Dynamic
Performance
D.1

Speed-loop parameters

The dynamic performance during operation in speed control is controlled
by the following parameters which are adjusted during commissioning of
the system:
3.10 { 0.13 } Speed-loop proportional gain
3.11 { 0.14 } Speed-loop integral gain
3.12 { 0.15 } Speed-loop derivative gain
The default values of these speed-loop PID-gains parameters can be
used for most applications.
Parameter
3.10 { 0.13 } Speed-loop proportional gain
3.11 { 0.14 } Speed-loop integral gain
3.12 { 0.15 } Speed-loop derivative gain
Table D.1 Ranges of values
The default values depend on the motor being used.
Inappropriate values entered in the parameters for the
speed-loop PID gains can cause the control system to
become unstable.
CAUTION
Current-loop bandwidth
If any mechanical resonances lie within the current-loop bandwidth of
the Drive they can give rise to torque oscillations resulting in the
following effects, for example:
• Noisy motor
Drive monitoring
Hardware enable
_SL
_MD
Speed reference
(±10V)
_AN
SPEED
CURRENT
(TORQUE)
RUN
RESET
Figure D-1 Signal connections for adjusting the speed-loop gains
92
•
•
•
(Inertia mismatch and flexible couplings are prone to introducing such
resonances.)
Torque oscillations can be minimised by adjusting the current-loop
bandwidth of the Drive in addition to the PID gains.
PID-gains buffers
The PID-gains parameters are held in the Drive, along with a copy of
each held in a buffer in the SLM for use by the speed loop.
Adjustment of the PID gains is made by changing the values of the
parameters held in the Drive (eg. 3.10 { 0.13 }, 3.11 { 0.14 }, 3.12 { 0.15 })
and updating the SLM either concurrently or subsequently.
In addition to the set of PID gains already described and which are
duplicated in Menu 0, two addtional sets of gains are available only in
Range
Menu 3. Rapid selection can be made between these three sets while
the motor is running (see Gain sequencing on page 96).
0 ~ 0.3000
0 ~ 20.00
Methods of adjusting the PID gains
0 ~ 0.1000 For a practical approach to optimising the dynamic performance, see
Adjusting the speed-loop gains (which follows).
For a simple approach, see Specifying shaft stiffness and load inertia on
page 93.
D.2
This procedure requires the Drive to be operated in speed control during
adjustments.
Higher gains result in the following:
•
•
•
If required, see also Gain sequencing on page 96.
MC/EIA485
Status
relay
11
24V user supply
3
Hardware enable
STANDALONE
13
High-precision
analog input
12
0V COMMON
14
SIM ENC
Standard-precision
analog input
15 Cable shields
0V
Analog output 1
9
Analog output 2
DIGITAL I/O
24V user supply
Digital input 1
Digital input 6
Vibration
Instability
Over-current trips

Adjusting the speed-loop gains

Greater shaft stiffness
Greater peak currents with increased possibility of the Drive tripping
on over-current
Smaller stability margin
M'Ax User Guide
Issue Number: 4