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ELEC2540 Control Systems Lab
Note: Videos are supplementary to Lab handouts
What is the purpose of this experiment?
1. To understand the hardware components and their
connectivity and to then perform calibration and testing prior
to the start of the experiment
2. To investigate the hardware provided and determine the
critical transfer characteristics of the component parts
3. To investigate the performance of the closed loop control
system through the adjustment of critical closed loop
parameters. Both the hardware and software will be explored
from a maths perspective and also from the real time display
of closed loop critical points under the following conditions:
A. Proportional (P) Control
B. Proportional/Integral (PI) Control
C. Proportional/Integral with Anti-windup Control
Click on the following video link: Introduction
Understanding the hardware components
The compass unit:
• Magnetometer
• Servo drive and PWM
• Pulley belt system
The compass control unit:
• Power input requirement
• Connectivity to the compass unit
• Test Point outputs
The Human Machine Interface (HMI):
• FTDI USB to RS232-TTL-5V communications cable
• MTTTY terminal emulation software
• Connectivity and initialisation issues
The following video will discuss, in detail, the components used in
this experiment.
Click on the following video link: ELEC2540: Introduction to hardware
Compass Control Unit schematic
In the following video we will look at the Compass Control Unit from
an embedded design perspective and why it is designed to generate
positive and negative voltages and how it generates the correct Test
Point (TP) output voltages i.e. +/- 1.25 V from the single supply
Digital to Analogue Converters (DACs) within the microcontroller.
This analogue conversion allows us to visually represent, in real time,
the maths associated with control system algorithms and in
particular the values of:
• Error (e)
• Proportional Component i.e. K x e
• Integration Component i.e. Σ(e x Δt)
Click on the following video link: ELEC2540: Compass Control Unit Schematic
Compass Control Unit software
In the following video we will look at the Compass Control Unit from
a software perspective in terms of the following:
• HMI creation
• Internal RC oscillator calibration
• Servo null point adjustment
• DAC testing
• Compass positioning to North or South
• Compass pointer rotational speed control and direction
Click on the following video link: ELEC2540: Compass Control Unit Software
Calibration and testing
In this video we will be looking at the calibration and testing of the
hardware. Using the HMI we can stimulate events and observe
output signals on an oscilloscope
The order of calibration and testing is as follows, note that the page
numbers refer to the ELEC2540 Lab documentation:
• Setting the internal frequency of the microcontroller (Page 13
- 14)
• Setting the ‘Null’ point of the servo (Page 14 - 15)
• Testing the DAC outputs (Page 15)
• Testing the compass positioning control system (Page 16)
• Testing controlled clockwise and anticlockwise operation
(Page 17 - 18)
Click on the following video link: ELEC2540: Calibration and Testing
Servo Transfer Characteristics
• In this video we will be looking at the transfer characteristics of the servo.
By setting the compass pointer to rotate at a constant speed, via the HMI
option menu, it is possible to observe the magnetometer output position
from a maths perspective on the oscilloscope. The maths relationship can
be looked at in detail if you refer to the lab notes (Page 19 – 21)
• Note that the CMPS12 magnetometer output from the IIC interface is a
number from 0 to 3599 i.e. tenths of a degree where North equates to 0
and South equates to 1800. Within the software this value is converted into
degrees i.e. divided by 10 and then offset such that North to South in a
clockwise direction ranges from 0 to +180.0 and in an anticlockwise
direction 0 to -179.9. This value is then scaled and offset for loading into
the CH4 output DAC which has a voltage output range between +/- 1.25 V,
where North is represented by 0V
• This output is used to establish the frequency of rotation of the compass
pointer for defined PWM servo offset values ranging from 1 through to
500 μs
Click on the following video link: ELEC2540: Servo Transfer Characteristics
Servo Transfer Characteristic Results
From this data, plot graphs for each of the pulley
ratios and critically evaluate and comment on your
findings
From the previous video the following data was recorded
Proportional Control
In order to aid your understanding of the control algorithm
and its physical manifestation this section has been split into
two videos. The first video will explore the control system
schematic, software and HMI, and the second will explore
the physical properties through the experimental hardware
In this experiment you will determine the values for Ku and
the Tu as required by the Ziegler-Nichols methodology
Click on the following video link:
ELEC2540: Proportional Control Theoretical Analysis
Click on the following video link:
ELEC2540: Proportional Control Practical Analysis
Proportional Control Results
The following tables are the recorded results from the
experimentation for different pulley ratios
Proportional Control Results (Continued)
Proportional Control Results (Continued)
Why do you think the unstable oscillation period is relatively constant
between pulley ratios and why do you think the ratio 1:2 seems to
slightly increase the unstable oscillation period?
Proportional Integral Control
Click on the following video link:
ELEC2540: Proportional Integral Control Theoretical Analysis
Click on the following video link:
ELEC2540: Proportional Integral Control Practical Analysis
Similarly to the Proportional Control experiment, this section
has also been split into two videos. The first video will
explore the control system schematic, software and HMI,
whilst the second video will explore the physical properties
through the experimental hardware
Proportional Integral Control with Anti-Windup
Click on the following video link:
ELEC2540: Proportional Integral Control with Anti-Windup Theoretical Analysis
Click on the following video link:
ELEC2540: Proportional Integral Control with Anti-Windup Practical Analysis
Similarly to the Proportional and Proportional and Integral
Control experiments, this section has also been split into two
videos. The first video will explore the control system
schematic, software and HMI, whilst the second video will
explore the physical properties through the experimental
hardware