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151/23/005 > Automated controls > Flashcards

Automated controls Flashcards

1
Q

what are the 3 types of control?

A
  • manual
  • remote
  • automatic
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2
Q

sname dome types of control systems

A
  • regulatory
  • positional
  • programmable
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3
Q

give a brief description of regulatory control

A

power is required continuously to produce an output, there by an error signal is needed in steady state conditions

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4
Q

give a brief description of positional control systems

A

o/p and i/p under steady state conditions

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5
Q

give a brief description of programmable control systems

A

a laid don sequence of events is followed until the cycle is complete or interrupted

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6
Q

what are the four types of control medium

A
  • mechanical
  • electrical
  • pneumatic
  • hydraulic
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7
Q

Draw a block diagram of open loop control

A

See drawing

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8
Q

names the changes (disturbances) that will cause the output speed to change, in open loop control

A
  • fuel pressure
  • load change (most common)
  • wear
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9
Q

Draw the closed loop control block diagram

A

see drawing

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10
Q

define the term feedback

A

the relaying of output information back to the input

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11
Q

define the term EMD

A

Error measuring device

Any device which compares the input valve with the output value and produces an error signal proportional to the difference between the two

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12
Q

What are the two forms of feedback in closed loop control?

A
  • positive feedback
  • negative feedback
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13
Q

what is positive feedback in closed loop control?

A

Positive feedback has a regenerative and de-stabilising effect and is used in oscillators

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14
Q

what is negative feedback in closed loop control?

A

Most commonly used in control systems and is non-regenerative

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15
Q

what are the three levels of damping?
what are there values

A
  • underdamped. less than 1
  • overdamped. greater than 1
  • critically damped. equal to 1
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16
Q

list the graphical representations of time varying signals used in control engineering

A

step
ramp
pulse
impulse
sine wave

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17
Q

one thing in common to all RC combinations is time constant, which is defined as ?

A

the time taken for the output to reach 63% of its final value when a step input is applied

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18
Q

what are the two basic types of electrical interlocking systems?

A

power interlocking
control interlocking

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19
Q

what is control interlocking ?

A

the power source of the hazard is interrupted by the switching of a circuit which controls the power switching device

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20
Q

draw the diagram shoeing the different types of interlocking

A

see tree diagram drawing

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21
Q

what is a transducer?

A

A device which converts a signal into another type of signal

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22
Q

what are some of the common properties of transducers ?
DEFINE WHAT THEY ARE?

A
  • accuracy, the relationship about closeness of the output value to the input parameter
  • repeatability, the variation of the transducers output around an excepted value for given constant input
  • sensitivity, how much the output changes for a change input
  • response time, the output will always be considered to be equal to the input when 67% of the original error has been corrected
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23
Q

what is the fundamental interval of a Resistance Temperature detector?

A

38.5 ohms

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24
Q

what temperature transducer produces a voltage dependent on temperature?

A

thermocouple

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25
what dose RTD stand for?
resistance temperature detector
26
what effect dose a thermocouple use?
seebeck
27
what is POISSON's RATIO
when material is stretched length increases but cross sectional area decreases. the ratio of this is unknown as poissons ratio
28
what is the stainless gauge fitted to on the propeller shafts on ships and subs?
brushless torsionmeter
29
what are the different types of pressure transducers?
U tube manometer bourdon tube strain gauge
30
what dose LVDT stand for
linear variable differential transformer
31
what are the three basic elements of a LVDT?
- two identical secondary windings - one primary winding - a movable ferromagnetic armature
32
what are tach generators?
a form of transducer for the measurement of velocity
33
what are the two main types of tachogenerators?
AC DC
34
how can the ripple in a DC tachogenertor be reduced?
adding a low pass filter
35
when using a AC tach generator what is undesirable?
an increase in frequency
36
what would happen to the output of a DC tacho generator if the speed where to increase?
DC voltage decreases
37
what would cause a decrease in the number of pluses generated by a phonic wheel transducer
a decrease in shaft rotation speed
38
what are the four main types of float operated devices?
- spiral - wire -reed - float
39
wat is linvar used for?
to measure angular displacement
40
what does CJCU stand for?
cold junction compensating unit
41
how can a ships roll be compensated for in tank levels ?
use two or more level transducers
42
what are some elements of an ultra sonic level transducer?
- detector circuit - transmitter/receiver - comparator
43
what would happen to the sensing range of a ultra-sonic level sensor if the frequency is increased?
the range would decrease
44
what can float switches be used for?
high and low level alarms
45
what is used to create difference in pressure within pipes?
orifice plate
45
what is an LDR?
light dependent resistor the resistivity is a function of the incident electromagnetic radiation
46
what happens to the resistance of an LDR when the intensity of light increases?
decreases non-linear
47
what are the two types of LDRs?
- intrinsic - extrinsic
48
what is photo conductivity?
an optical phenomenon in which the materials conductivity is increased when light is absorbed by the material
49
draw the basic positional servo system
se drawing
50
what are the 3 forms of friction? what are their differences?
- static, causes initial drag - coulomb, drag of constant magnitude - viscous, directly proportional to velocity
51
define backlash
the loss of angular motion which occurs when the direction of rotation of a mechanical drive is reversed
52
what modifications are made to basic positional servo system to achieve velocity feedback?
a tacho generator, EMD and variable resistor is added
53
what are the two main types of rotary encoders? what are their differences ?
- absolute, when power is removed from the system, the encoder stays in position - incremental, accurately records change in position but dose not power up with fixed relationship between encoder state and physical shaft position
54
what is the equation for step angle
360 degrees/rotor teeth x stator phases
55
hoe do you calculate half step angle
step angle / 2
56
how do you calculate distanced travelled?
step angle x number of pluses
57
what are the three main types of stepper motors?
- variable reluctance - permanent magnet - hybrid
58
what is a stepper motor ?
it is a power device which converts D.C voltage pulses into a proportional mechanical movement of its spindle
59
what is the unipolar operation of a stepper motor?
A C B D A
60
what is the half step operation of a stepper motor?
A AC C CB B BD D DA A
61
what is pull out torque
maximum torque which can be applied to a motor, running at a given stepping rate, without losing synchronism
62
what is pull in torque
max torque against which a motor will tart at a given pulse rate and reach synchronism without losing step
63
what is holding torque
max torque which can be applied to an energised stationary motor without causing spindle rotation
63
what is stepping rate
the number of steps per second applied sequentially to the field windings to cause motor rotation
64
what is pull out ride
max switching rate at which a motor will remain in synchronism while the switching rate is gradually increased
65
what is pull in rate
max switching rate at which at which a loaded motor can start, stop and reverse without losing steps
66
what is slew range
range of switching rates between pull-in and pull-out curves, in which a motor will run in synchronism but cannot start or reverse
67
name some advantages of stepper motors
- they are easily controlled by computers, since windings currents are simply switched ON or OFF - speed of rotation can be controlled by setting the time between successive steps - direction of rotation is controlled by the winding excitation - no brushes or slip rings on the rotor therefore very reliable
68
name some disadvantages of stepper motors
- limited in velocity - limited by a available torque
69
what are the 5 main components of 4 to 20 mA? give a brief description of what they do
- transmitter, coverts measurements into current signal - sensor, measures a process variable - power source, produces a DV current output - loop, refers to the actual wire connecting the sensor to the device receiving 4 -20mA and back - receiver, receive and interpret the current signal
70
what is the distance 4 to 20 mA loops can work over? what electricity law allows this to happen?
3 km Ohms law
71
draw the 4-20mA tank level sensor
see drawing
72
draw a digital control system
see drawing
73
in a digital control system, what part of the system will compare the current value with its programmed value?
the microprocessor
74
what are the most common types of network configurations? give a brief description of each
- star, has a central connection point called a hub/router - ring, every device has exactly two neighbours. All messages travel through a ring in the same direction - bus, all devices use a common back bone to connect them.
75
what network requires less cabling compared to the others?
bus
76
what is band width?
The usable frequency range of the cable
77
what are the uses of fibre optic media?
- control systems - telecommunications - computing networks - video transmission -
78
what is broadband?
enables two or more communication channels to share the bandwidth
79
draw and label the bandwidth amplifier/frequency graph
see drawing
80
what causes performance issues when a bus network is overloaded with devices?
unacceptable number of collisions
81
what is a communication protocol?
rules foe sending blocks of data from one node to another
82
what percentage of network loading will results in collisions issues for a bus network?
80%
83
what mode of data transmission has only one transmitting device and several receivers?
baseband
84
how many oscillations will the response of an optimally damped system generally go through before entering the acceptance zone?
one and a half
85
what form of isolation barrier is required in an interlock when it is possible for two sets of contacts to touch each other back to back in the event of contact weld?
galvanic isolation
86
what are the three types of mechanically actuated interlocks?
tongue hinge cam
87
what are the 2 junctions called for a thermocouple?
hot and cold
88
draw a thermocouple
see drawing
89
in an RTD what is measured during temperature changes?
resistance
90
what is a sampling error?
insufficient samples
91
which digital to analogue convertor only requires 2 values of resistor
r2r ladder
92
which digital to analogue converter requires different values of resistors?
binary weighted ladder
93
name 4 components of a microcontroller?
RAM CPU

151/23/005 (13 decks)

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