A control system is a set of devices which consist of commands , instructions that are further manipulate to produce or develop controlled variables. these control variables are then passes to the plant processor which gives desired output.
it plays a very important role to develop the modern technology.every system require the control engineering involve with it to make the system more intelligent.these systems include mechanical, electronic, pneumatic and computer aided. there are number or control systems like refrigerator, air conditioner and automobiles etc. these all are the example of control system.
A mechatronics system consist of microprocessor, actuators, plant, sensors etc. there are other types of signal conditioning system to make the signal more desirable like low pass filter, analog to digital converter and digital to analog converter, amplifier etc. sensor play very important role in control system.
because sensors make the system more intelligent and also allow the system to interact with the external environment.these are used in most of the industries, robotics, automobile engineering, mechatronics engineering.
TYPES OF CONTROL SYSTEM
1. open loop control system
2. closed loop control system
OPEN LOOP CONTROL SYSTEM
open loop control system does not require any feedback control system. in this type of control system , system does not allow to interact with the external environment. the output signal does not compare with reference signal to modify the input parameters.
these system are more inexpensive than the closed loop control system.system does not observe the output of the processes that it is controlling.in this system output has no effect on the control action.
They hold good if its calibration is good.it does not require any feedback control system so it is so easy to construct it. it is more stable than the closed loop control system.if there are non- linearity in the signal then the system operation is not good.
WORKING OF OPEN LOOP CONTROL SYSTEM
here you can see a schematic of the open loop control system.
the command input in the form of analog signal is first feed to the analog to digital converter. it is require because analog signal can not be understood by the controller so A/D converter is used to convert the analog signal into the digital signal. these digital signals are feed to the controller to generate the controlled variable. these controlled variable are feed to the process or plant which gives the desired output.this is also known as the controlled output.
EXAMPLES OF OPEN LOOP CONTROL SYSTEM
1. WASHING MACHINE
2. TRAFFIC SYSTEM
3. CONTROL OF THE FURNACE FOR COAL HEATING
4. LIGHT SWITCH
5. GAS OVENS
6. TV REMOTE CONTROL
washing machine is a open loop control system because after the process of the machine (means after the clothing) it is not require to check the condition of the clothing whether it is clean or not.
there are several cyclic process in the washing machine
1. pre-wash cycle- in this cycle the clothes are first wash in cold water
2. main wash cycle – then further clothes wash in hot water
3.rinse cycle – after this clothes are rinsed with cold water
4.spinning cycle- in the last cycle water is remove from the clothes by spinning the drum.
ADVANTAGE OF OPEN LOOP CONTROL SYSTEM
1.These are easy to construct because they does not require any additional circuit like feedback control circuit.
2.these systems are more stable than the closed loop one.
3. these system are inexpensive than the closed loop control system.
4.these system are more economical than the closed loop one.
1.THESE are inaccurate.
3.output can not be corrected automatically.