Fundamentals of control system is essential to study before go to the more complex theories.
Feedback Control System (Closed Loop)
- Plant (controlled system) is the system (e.g. – vehicle, chemical process, power electronic converter) to be controlled.
- Feedback element is the sensor (s) that feeds that the plant output to the back to the controller.
- Controller is taking the error (Difference between reference input and the feedback output) into account to create a control signals (commands in a way the error is zero. (or at least minimized)
- Reference input is the desired output.
Plant or the control system
- Actuator such as motors in various form valves, engines etc. Controller communicate with the actuators of the plant.
- Loads such as number of passengers in a car (here car is plant), electric loads on a power generator (here generator is the plant, thermal loads (all heat emitting objects) in an air conditioning system.
Fundamental of Loads bound to vary
- Controller is the brain of the system. It processes the sensory information and produces the control commands to the actuators to be able to do this brain (or the controller).
Standalone air conditioning system
- Plant: Air conditioning unit and the indoor room.
- Actuators: Compressor powered by an electric motor
- Load: All the heat emitting objects in the indoor room such as humans, computers etc.
- Controller: Temperature controller such as micro controller or on-off controller with controller algorithms
- Micro controller (e.g. Inverter air conditioner)
- On-Off controller (e.g. Traditional air conditioner)
- Sensor: Thermostat
- Reference output: Set value for temperature in air conditioner
Engine – generator set (consider frequency control)
- Plant: Generator with its electric load
- Actuators: Combustion Engine
- Load: Electric load on the generator such an air conditioner, listing load, etc.
- Controller: this is usually call frequency governor
- Sensor: Output frequency or generator shaft speed sensor (frequency is proportional to the shaft speed)
- reference input: 50/60 Hz for the power system frequency
Writing by a Human
- Plant: Hand with the writing tool such as pen
- Actuators: Hand muscles involved in writing
- Load: Pen and the friction forces at the paper pen interface
- Controller: Human Brain with the writing Skills
- Sensor: Human Eye
- Reference input: What is to be write
Writing by robot arm
- Plant: Robot arm with the writing tool such as pen
- Actuators: Electric Motors
- Load: Pen and friction forces at the paper pen interface
- Controller: Micro controller with the robot motion control algorithms
- Sensor: Video Cameras
- Reference Input: What is required to be written (this maybe defined in a form the algorithm understand, for instance, in terms of x-y coordinate position trajectories.
Open Loop Vs Closed Loop Control
In the Open loop control system plant output has noninfluence in the control action. There I no feedback in the system. Np sensors are useing.
e.g. Bread Toaster: The setting if the darkness knob or timer respects the reference input and the degree of darkness or crispiness of the toasted bread is the output. If the degree of darkness is not satisfactory, there is not way automatically alter or adjust the length of the time the heat is supplied.
- There is not speed feedback in above system
- Here, Motor speed control is open- loop
- Temperature control is open loop
Above theories are the Fundamentals of control system and for more go to the control system article in this category.