control actions
DESCRIPTION
control system controllersTRANSCRIPT
Basic Control Action
By :-Vishal Thakur100104143B.Tech (EE) Sem VSection B
• A controller compares the actual value of
output with the reference input, determines the deviation, and produces a control signal that will reduce the deviation to zero or to a small value.
• The manner in which the controller produces the control signal is called the control action.
Introduction
Block Diagram of a Basic Industrial Control System
Classifications of Controllers.
• 1. Proportional controllers
• 2. Integral controllers
• 3. Proportional-plus-integral controllers
• 4. Derivative controllers
• 5. Proportional-plus-derivative controllers
• 6. Proportional-plus-integral-plus-derivative controllers
Proportional Control of Systems.
• Actuating signal is proportional to error signal
• Such a system always has a steady-state error in the step response. Such a steady-state error is called an offset.
Change in gain in P controller• Increase in gain:
Upgrade both steady-state and transient responses
Increases oscillations
Reduce steady-state
error
Reduce stability!
Integral Control of Systems.
Integral Controller
• Integral of error with a constant gain increase the system type by 1eliminate steady-state error for
a unit step input amplify overshoot and oscillations
Proportional-Plus-Integral Control
• To eliminate offset, the proportional controller may be replaced by a proportional-plus-integral controller.
• If integral control action is added to the controller, then, as long as there is an error signal, a signal is developed by the controller to reduce this error, provided the control system is a stable one.
Change in gain for PI controller
• Increase in gain:
Do not upgrade steady-state responses
Increase slightly
settling time
Reduces stability and bandwidth of system
Increase oscillations and overshoot!
Derivative Controller
• Differentiation of error with a constant gain
detect rapid change in output reduce overshoot and oscillation
do not affect the steady-state response
Proportional-Plus-Derivative Control
With derivative action, the controller output is proportional to the rate of change of the measurement or error.
Effect of change for gain PD controller
• Increase in gain:
Upgrade transient
response
Decrease the peak and rise time
Improves stability and bandwidth of system
Increase overshoot
and settling time!
Proportional-Plus-Derivative -Plus-Integral Control
• A proportional–integral–derivative controller (PID controller) is a control loop feedback mechanism widely used in industrial control systems – a PID is the most commonly used feedback controller.
• A PID controller calculates an "error" value as the difference between a measured process variable and a desired setpoint. The controller attempts to minimize the error by adjusting the process control inputs.
• The PID controller calculation involves three separate constant parameters, and is accordingly sometimes called three-term control: the proportional, the integral and derivative values, denoted P, I, and D.
• These values can be interpreted in terms of time: P depends on the present error, I on the accumulation of past errors, and D is a prediction of future errors, based on current rate of change.
Changes in gains for PID Controller