Project Three
MOTOR SPEED CONTROLLER
Ewan, Dave, Mitch, Simon, James and Chris
Background Motor Control
DC Series Motor.
Can be used for a variety of Industrial applications.
Pumps
Electric Trains
Motor control achieved through varying terminal
voltage across the motor armature.
Series DC motor Circuit [1]
DC series type motor [2]
Background Siemens PLC
S7-314C_2DP
Industrial type PLC
Middle of the range model
Two S7’s were used for this project to act as a
controller and process.
Siemens S7-300 [3]
PLC’s of the Past
Controller for Ferag Publishing Winder
TTL and wire wrapped pins
Siemens Controller
circa 1980
Background HMI
TP177B-PN/DP 6”
Discontinued model
Ability to adjust outputs and read
operating conditions
TP177- Siemens HMI [4]
Objectives
Utilise two Siemens PLC’s. (Controller and Process)
Utilise PID control for the Process in TIA.
Set point tracking
Compensation load variations on the motor
Additional Objectives:
Correctly operating visual indicators through the HMI
Delivery as a single multi-PLC project
Design: Overall Design
Controller and Process Design
Design: Initial Planning
Identified early that planning would be extremely
important for managing 6 team members.
Differing programming styles
Strengths and weaknesses
Project leader nominated.
The group decided on modelling a DC series motor.
Identified metrics for a successful simulation.
A Gantt chart was used so all team members knew their
roles and responsibilities.
Controller PLC
Process PLC
Report and Documentation
PID block
HMI
Design: Process Model
Process model was created in Simulink as a second
order system.
A second order was selected because its response
most closely represents a typical motor speed curve.
• Initial slope of zero.
• Initial response of zero.
• Simulates the motor ‘lag’ in
response to a set point
change.
A second order response
Design: Process Model
Discretised using Euler approximations.
This was done because it enables easy manipulation
of gain, natural period and damping coefficient.
The result of the Euler method was programmed in
TIA by utilising math blocks.
Noise was simulated through the use of multiple sine
waves added to the final output.
Load was simulated by the addition of a first order
disturbance to the output.
Design: Controller
Second order system response was controlled in the
S7 using the standard PID block.
The PID was originally used to achieve the desired
response.
No steady state offset
Quick response
No overshoot
The PID was used to accommodate the
implementation of disturbance.
The controller PLC also managed the extra functions
through use of the HMI.
Design: Entire Process
Simulink Model of Entire System
Design: HMI
Interact with Controller PLC
Monitor speed and controller response
Manipulate set point
Indicate fault status
Communication over MPI
Piggy-back off PLC
Transfer over Ethernet
Orders of magnitude faster than MPI
Substantial difficulty
commissioning
Results
Overall, system performed well.
Simulated process adequately.
Controller responded appropriately.
HMI allowed for enhanced control.
Responded as desired under all test conditions.
Emergency stop and system reset
Adding and shedding load:
Over and under speed responses.
Improvements
Additional testing/tuning of PID block to increase
robustness.
Increased safety measures and further condition
monitoring.
PLC Interfacing over MPI or Profibus instead of
using digital and analogue I/O.
Fault Screens on error.
Questions
References
[1]DC series Motor Circuit. Online: http://electrical-engineering-
portal.com/4-types-of-dc-motors-and-their-characteristics .
Accessed:7/6/15.
[2] DC Series Motor.
http://www.globalspec.com/reference/42926/203279/shunt-seriesand-compound-motors . Accessed: 7/6/15.
[3] Siemens S7-300. http://www.nexinstrument.com/CPU-314C-2DP6ES7314-6CH04-0AB0_p_69.html . Accessed: 7/6/15.
[4] TP177 HMI. http://www.comeon365.com/ProductInfo5165.html .
Accessed: 7/6/15.
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