CONTROL SYSTEM 1 (EIC - 501)
(Session: 2014 – 15)
Submitted By:
Mr. Dheeraj Singh
Mr. Mangal Das
EC Department.
ABES Engineering College
Ghaziabad, U.P
BASIC COMPONENTS OF CONTROL SYSTEM
System – An interconnection of elements and devices
for a desired purpose.
Control System – An interconnection of components
forming a system configuration that will provide a
desired response.
Process – The device, plant, or system under control.
The input and output relationship represents the
cause-and-effect relationship of the process.
OPEN LOOP CONTROL
SYSTEMS
They are conditional control configurations formulated under the basic
conditions that the system should not be subjected to any type of
disturbances.
Feedback is not Connected.
More Stable than Closed loop systems because the effect of feedback is that
it introduces delays or lags making the the speed of response of a closed
loop system slow
Performance analysis is not applicable to open loop systems because they
are highly stable
CLOSED LOOP SYSTEMS
In this config. Changes in the output are measured through feedback &
compared with Input or set point to achieve the control objective.
Measurement or feedback in automatic control system is done using sensors or
Transducers. Therefore feedback elements are measuring elements(Sensors or
Transducers).
EFFECTS OF FEEDBACK ON CONTROL SYSTEMS
The reduction of system error is merely one of the many important effects
that
feedback may have upon a system. There are other important effects , such as
stability,
bandwidth, overall gain, disturbance, and sensitivity.
If H=0 open loop system
1. Effect of Feedback on Overall Gain
Open-loop gain = G
Closed-loop gain =
The general effect of feedback is that it may increase or decrease the gain
G, and the gain of the system could increase in one frequency range but
decrease in another.
2. Effect of Feedback on Stability
If GH=-1, the system becomes unstable.
Feedback can improve stability or be harmful to stability if it is not
properly applied.
3. Effect of feedback on Sensitivity
The sensitivity of the gain of the overall system M to the variation in G is
defined as
4. Effect of feedback on External disturbance or noise.
A good control system should be insensitive to noise and disturbances and
sensitive to input commands. Consider the following system:
TYPES OF FEEDBACK CONTROL SYSTEM
BLOCK DIAGRAM REDUCTION TECHNIQUE
SIGNAL FLOW GRAPH
How to Obtain Transfer
function using Mason’s Gain
Formula
Mechanical Systems
All Mechanical Systems are classified into two types
(1) Mech Translational System
Input = Force(F) ;
Output = Linear Disp or Linear Velocity
The 3 – Ideal Elements
(1) Mass Element
M
(a) F = M dv/dt
X
V
F
(b) F = Md2X/dt2
(2) Damper Element
X1
V1
f or B
F = f (V1 – V2) = fV
F = f d (x1-x2) = fdx/dt
F
(3) Spring element
F = K (X1 - X2 ) = KX
F = K ᶴ (v1 – v2 ) dt
X2
v2
MECHANICAL ROTATIONAL SYSTEM
Input = Torque (T) ;
The 3 ideal elements are
(1) Inertia Element
(2) Damper Torsional Element
(3) Spring Torsional Element
Output = Angular disp or Angular velocity
ANALOGY BETWEEN MECHANICAL AND ELECTRICAL
SYSTEM
Electrical
Quantity
Mechanical Analog I
(Force-Current)
Mechanical
Analog II
(Force Voltage)
Voltage, e
Velocity, v
Force, f
Current, i
Force, f
Velocity, v
Resistance, R
Lubricity, 1/B
(Inverse friction)
Friction, B
Capacitance, C
Mass, M
Compliance, 1/K
(Inverse spring constant)
Inductance, L
Compliance, 1/K
(Inverse spring constant)
Mass, M
Sensors and Encoders in Control Systems
(i) Potentiometers
A potentiometer is an electromechanical transducer that converts
Mechanical Energy into electrical energy.
Ks = Proportional Constant
θc = shaft position
Ckt Representation
Tachometers
Tachometers are electromechanical devices that convert mechanical energy
Electrical energy.
Velocity control System with tachometer feedback
Position control system
Tachometer feedback
DC MOTORS IN CONTROL SYSTEM
Basic operational principle
Tm = Km ɸ Ia
Tm = Motor Torque
ɸ = Magnetic flux
Ia = Armature current
Km = Proportional constant
Back emf eb = Kmɸωm
ω = Shaft velocity
Mathematical Modelling of DC motors
Since ɸ is constant
Ki = Torque Constant
Block Diagram of DC Servo motor
Thank
You