March 29, 2012 IFAC Conference on Advances in PID Control1
PID APPROACH & ISSUESIN SERIES CONTROL SYSTEMSFOR MACHINE AUTOMATION
Ing. Adriano Chinello
Technical Director Automation DivisionGefran S.p.A.
General Targets for Series Control Systems
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Standard PLC application development (IEC 61131-3, PLCopen) High-value PLC software libraries: easy, complete, time-saving, … Cost – optimized hardware architecture Respect of target control specifications among many different
machines and over a wide range of operating conditions
Reference applications: full-electric injection moulding machine (FE IMM) Hydraulic injection moulding machine (HY IMM)
Specific Targets for IMM Control Systems
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Precise, repeatable and smooth changes between different control loops on single motion axes (position – speed – torque – mould pressure)
Electronic Noise Filtering / Tolerance (high power and inductive loads, poor cabling and shielding, …)
Compresence of very different processes:
- Electric Motion control (cyclic + events) 0.1 ÷ 1 ms- Hydraulic Motion control (cyclic + events) 1 ÷ 5 ms- I/O (cyclic) 5 ÷ 20 ms- Thermoregulation (cyclic) 50 ÷ 100 ms- HMI (events) > 100 ms- Supervisoring, Statistics, etc… (cyclic + events) low priority
PID Distribution in a FE IMM Architecture
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Modbus / CANopen
I/O real-time control loops
Motion high-level control
HMItask
PLC / SPC / aux
tasks
Monitoring / data
collection
Analog Input
Current Torque Speed Loop
Position / AI Loop
Speed / Torque Ref
Optical internal link
Power high-level control
GDnet / CANopen
Power / Thermo Loop
Remote I/O
Servo rack
Panel PC
Power Controller
Pressure Sensor
Panel PC - Fieldbus Performance and Cost
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cost
www.cpubenchmark.net
PID decentralisation allows Panel PC and fieldbus downsizing
PLC Motion Application Library
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Standard PLCopen
Only one software application for the whole machine
High-level programming, fieldbus and hardware independent
Standard Function Blocks with add-on (more flexibility)
Special Function Blocks with interfaces in line with the standard
Example: Injection Axis Control
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1 - MC_MoveAbsolute P1 V1 Aborting2 - MC_MoveAbsolute P2 V2 Blending Previous3 - MC_MoveAbsolute P3 V3 Blending Previous4 - MC_MoveAbsolute P4 V4 Blending Previous5 - MC_AnalogControl PR5 Blending6 - MC_AnalogControl PR6 Aborting7 - MC_AnalogControl PR7 Aborting8 - MC_Stop Aborting
EXE1ABORT.
EXE2BL. PREV.
P2
P1
P3
t
V1
V2
V, PR
DONE1
V3
V4
EXE3BL. PREV.
EXE4BL. PREV.
DONE2 INCONTROL5
SWITCHOVER
PR5
EXE6ABORT.
EXE7ABORT.
EXE8ABORT.
PR6
PR7
INCONTROL6 INCONTROL7 DONE8
ANALOGINPUTTHRESHOLD
P4EXE5BLENDING
Easy to develop, with a series of Function Blocks in blending
Switchover on position, pressure, … Control phases preloaded into the drive
PID Open Issues
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Smooth control switch vs time reactivity
Noise rejection vs time reactivity
Robust tuning procedures for reliability in series production: possibly one single tuning (or tuning procedure) for many machines and many different moulds for each machine
PID modularization and packaging into PLC software libraries, with both “simple entry level” and “complex advanced” user interface