AIMS OF THE EXPERIMENT
The aim of the experiment ...
AIMS OF THE EXPERIMENT
The aim of the experiment is to carry out an open loop step response on the process trainer PT326 and hence obtain a quantified transfer function of the form:
G(s) = (Ke^-T)/(1+TpS)
Output value (y) – This is the variable to be controlled i.e. temperature, speed.
Set point (v) – This is the desired value for the output value.
comparator – This forms the difference between the set point and the output value and the difference is often termed as error(e);
Process /plant – This is the thing to be controlled and it has an output value (y) and an input value called the control signal (u) or control effort.
Controller – This is a device which has input error (e) and produces the control signal at its output (u).
Once these parameters have been obtained, the following three design methods are to be applied to design proportional + integral controllers of the type shown in the above figure :
Ziegler-Nicholas method;
Cohen and Coon method;
Nyquist method.
Finally, the behaviour of the closed-loop system resulting from the use of each of these ‘rules’ is to be compared with a manually tuned PI controller and assessment of the alternative design methods is to be made.
INTRODUCTION:
Control system: A system to guide or manipulate various elements in order to achieve a prescribed result.
A control system is a device or set of devices to manage, command, direct or
Regulate the behaviour of other devices or systems.
The SPICE circuit for the Control System looks pretty much like the block diagram.
PID CONTROLLER: To get the proportional term, EP multiples Verror at v(2)by a fixed gain of 1. to get the integral term, current source G1converts v(2) to a current and integrates it on C1=1F.finally, the derivative term is created by GD converting v(2) to a current and forcing it through L1. the resulting voltage becomes v(5)=L1di/dt.a quick substitution of L1 =1H and i= Verror gets you v(5)=d Verror/dt
OUTPUT PROCESS: EOUT represents a very simplified model of a process to be controlled like motor velocity or heater temperature. The gain of 100 could represent an output transfer function of 100 RPM / V or 100 ° C / V. To include the effects of the motor's inertia or heater's thermal mass, we've added some time delay into the output using two cascaded RC filters. Although Vout is simulated in volts, we know it really represents other variables like velocity in RPM or temperature in °C.
SENSOR: The sensor tells you, typically by a voltage, what's happening at the control system output. For motor velocity, a tachometer could generate 1 V / 100 RPM; for temperature, a thermistor circuit could ...
