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CONTROL STUDIO A
Project Description
1. Gantry crane
Why gantry crane systems?
A gantry crane is a crane mounted on a moving gantry to allow horizontal movement along
an axis. Gantry cranes have a wide variety of applications in many industrial and construction
settings as shown in figure 1.1. Smaller cranes are often mounted in factories and industrial
complexes to allow movement of heavy loads such as bulk raw material and waste or used on
assembly lines of large machinery. These cranes tend to be mounted on walls. On a larger
scale, gantry cranes are used for maritime work; the overhead nature allows the crane to be
mounted over a channel to allow ships to pass beneath it and facilitate easy loading and
unloading heavy cargo without needing the large amount of space and clearance for
traditional boom cranes. As the load is suspended from the gantry, it acts as a pendulum upon
application of external forces such as the motion of the gantry or a distu
ance such as wind
and impact. This necessitates a method to stabilise the load to minimise the effect of
distu
ances upon the load.
Side-view of Super-PostPanamax portainer
crane at the APM Terminal in the Port of
Rotterdam
A ZPMC gantry crane used for construction
of the British aircraft ca
ier HMS Queen
Elizabeth
Figure 1.1: Some applications of gantry cranes 1
1 Source: https:
en.wikipedia.org/wiki/Gantry_crane
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Control objectives
The goal of this project is to develop a control scheme for a controllable Gantry Crane
consisting of a track, trolley and hoist along with control interface as shown in figure 1.2. The
controller must minimise the effect of distu
ance upon the pendulum by moving the trolley
to negate the movement of the suspended mass.
Figure 1.2: The gantry crane
Control requirements
• Overshoot < 15%
• Settling time < 5 s
• Steady state accuracy < 10%
• Swing angle < 150
• Test three types of controllers
2. Ball and Beam
Why ball and beam systems?
Most control problems that we meet in practical world are straightforward to control. For a
fixed input signal, the output stays more or less constant. An important set of systems
however are, either by design or nature, unstable and feedback control is essential to make
them operate safely. Many modern industrial processes and technological systems are
intrinsically unstable could be used without stabilizing feedback control.
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Figure 2.1: Aircraft roll control is a key real-world application of the Ball and Beam experiment
Important practical examples of unstable systems are:
1. In the chemical process industries - the control of exo-thermic chemical reactions. If a
chemical reaction generates heat and yet the reaction gets faster as temperature
increases, then control must be used to stabilise the temperature of the chemical reaction
to avoid a ‘run-away’ reaction. Exothermic reactions are used to produce many everyday
chemical products – without feedback control these products would not be available to
us.
2. In power generation – the position control of the plasma in the Joint European Torus (JET).
The object here is to control the vertical position of a plasma ring inside a hollow donut-
shaped metal container. The control is by using magnetic fields applied through the donut
and the plasma moves vertically in an unstable manner in response to the control fields.
To understand the problem, imagine pressing a wet ball of soap in between the flat of
your (slippery) hands. As you increase the pressure on the soap so it will slip out faster
when you alter the relative angles of your hands, (it’s the same problem trying to hold a
hamster).
3. In aerospace – the control of a rocket or aircraft during vertical take-off. The angle of
thruster jets or diverters must be continually controlled to prevent the rocket tumbling or
the aircraft tipping. Without feedback control to stabilise the movement, there would be
no space rockets and the famous Hawker Ha
ier ‘jump-jet’ would have remained a dream
on the desks of Sir Sydney Camm and his engineers at the Hawker Aircraft Company.
The control of unstable systems is critically important to many of the most difficult control
problems and must be studied in the laboratory. The problem is that real unstable systems
are usually dangerous and cannot be
ought into the laboratory. The ball and beam system
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was developed to resolve this paradox. It is a simple, safe mechanism and yet it has the
important dynamic features of an unstable system. 2
Control objectives
The Ball and Beam module consists of a steel rod in parallel with a nickel-chromium, wire-wound
esistor forming the track on which the metal ball is free to roll. The track is effectively a
potentiometer, outputting a voltage that’s proportional to the position of the ball (figure 2.2).
The control job is to automatically regulate the position of the ball on the beam by changing the angle
of the beam. This is an interesting control task because the ball does not stay in one place on the beam
ut moves with an acceleration that is proportional to the tilt of the beam. In control technology, the
system is open loop unstable because the system output (the ball position) increases without limit for
a fixed input (beam angle). Feedback control must be used to keep the ball in a desired position on
the beam.
Figure 2.2: An overall look of the Ball and Beam system
Control requirements
• Overshoot < 15%
• Settling time < 5 s
• Steady state accuracy < 1 cm
• Test three types of controllers
3. Magnetic Levitation
Why magnetic levitation systems?
Magnetic levitation is the method in which an object is suspended in air by the use of
magnetic fields and no other support. There is already a myriad of ways in which the principle
2 Peter Wellstead, BALL AND BEAM 1: Basics, control systems principles.co.uk
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of magnetic levitation is used in everyday life. One of these examples are the number of
maglev trains which operate around the world as shown in figure 3.1. The maglev trains are
able to move without making contact with the ground using permanent magnets to produce
lift and propulsion forces. This will consequently reduce friction by a great extent allowing for
very high speeds usually between XXXXXXXXXXmiles.
Transrapid 09 at the Emsland test
facility in Germany
SCMaglev test track in Yamanashi Prefecture,
Japan
Figure 3.1: Maglev trains.3
Magnetic levitation is also used for contactless melting, magnetic bearings and for product
display purposes (see Figure 3.2).
Melt metal with magnets
Magnetic bearing
Figure 3.2: Applications of magnetic levitation
Control objectives
The main objective of this project is to design a controller which is able to levitate a steel ball between
a pedestal position sensor and the electromagnet. The controller should control the coil cu
ent which
then in turn controls the magnetic force required to lift the ball and counteract the forces due to
gravitational acceleration.
3 https:
en.wikipedia.org/wiki/Maglev
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Figure 3.3: The magnetic levitation module in control lab.
Control requirements
• Be able to levitate the ball
• Settling time < 5 s
• Test three types of controllers
4. Pneumatic Rotary Pendulum
Why Pneumatic Rotary Pendulum?
Pneumatic rotary actuators are commonly used to convert compressed air pressure—in the
form of a cylinder stroke—into an oscillating rotary motion. In essence, this is a switched
actuator, i.e., the torque that can be applied to the rotary mechanism can take only three
possible values, maximum in clockwise direction, maximum in counter-clockwise direction,
and null. These actuators are commonly used in industrial applications such as conveying,
clamping, transfe
ing parts, positioning, and controlling valves. Like other pneumatic
components, they are durable, offer simplicity and high force for their size, and can operate
in hazardous environments. For instance, they can be found in food mixers (since no
lu
icants are required), and diesel and petrol pumps for safety reasons.
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Air-operated rotary gear pump for fast and safe
dispensing of diesel and petrol
Industrial food mixer and drier complying
sanitary standards
Figure 4.1: Applications of pneumatic rotary actuators.
Controlling a pneumatic rotary pendulum can also help one to understand how the attitude
of satellites and spacecrafts are governed in the space. In particular, attitude manoeuvres
involve changing the orientation of the spacecraft in any of three possible axes (called roll,
pitch, and yaw). For instance, to rotate a spacecraft, a pair of thruster rockets on opposite
sides of the vehicle are fired in opposite directions. To stop the rotation, a second pair is fired
to produce an opposing force.
Figure 4.2: Attitude control of spacecrafts and satellites
Control objectives
The pneumatic rotary pendulum is one of the most dynamic projects in the field of automatic
control. The system is a bi-directional rotating pendulum whose direction is controlled by
means of air pressure supplied from a jet. A pressure of about 200 kPa is used to drive the
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system. The main objective of the system is to control the flow of the air using electrically
operated solenoid valves which open and close and thus switching the direction of the air
flow as required. Hence, the position of the pendulum is controlled effectively via ‘discrete’
inputs with the help of control valves.
Figure 4.3: The Pneumatic Rotary Pendulum
Control requirements
• Overshoot < 15%
• Settling time < 10 s
• Steady state accuracy < 50
• Test three types of controllers
5. Rotary Inverted Pendulum
Why Inverted Pendulum?
An inverted pendulum is a pendulum that has its center of mass above its pivot point. It is
unstable and without additional help will fall over. Arguably the most prevalent example of a
stabilized inverted pendulum is a human being. A person standing upright acts as an inverted
pendulum with his feet as the pivot, and without constant small muscular adjustments would
fall over. The inverted pendulum