Open System
Is one which interacts with environment either for collection of information on which to base their
strategy or control. E.g. Business system. An open system is a system that has external interactions.
Such interactions can take the form of information, energy, or material transfers into or out of the system boundary,
depending on the discipline which defines the concept. An open system is contrasted with the concept of an isolated system which exchanges neither energy, matter, nor information
with its environment. An open system is also known as a flow system.
Features of open system
i. They are influenced by environment
ii. They influence the environment
iii. They are connected to and interact with the environment.
2. Closed system
Are systems that do not interact with environment either for exchange of information or for transaction purposes. These systems are self-contained and stable i.e. can exist on their own.
They do not exchange material, information, energy with its environment. Closed System can also be defined as an isolated system that has no interaction with its external environment. Closed systems with outputs are knowable only thorough their outputs which are not dependent on the system being a closed or open system. Closed systems without any output are knowable only from within.
A completely closed system is rare in reality.
Features of closed system
i. They do not influence the environment.
ii. Are not influenced by the environment.
3. Open Loop System.
Are system that do not contain feedback element. This implies that there is no basis of output.
Open-loop system, also referred to as non-feedback system, is a type of continuous control system in which the output has no influence or effect on the control action of the input signal. In other words, in an open-loop control system the output is neither measured nor “fed back” for comparison with the input.
i. There is no comparison between actual and desired values.
ii. An open-loop system has no self-regulation or control action over the output value.
iii. Each input setting determines a fixed operating position for the controller.
iv. Changes or disturbances in external conditions does not result in a direct output change (unless
the controller setting is altered manually).
4. Closed loop System
These are system that has feedback loop i.e. communicate the measured output to the control.
A closed loop control system is a set of mechanical or electronic devices that automatically regulates
a process variable to a desired state or set point without human interaction. Closed loop control systems contrast with open loop control systems, which require manual input.
A closed loop system is a control system where the output of the system is monitored and fed back
into the system as an input to the system. Another example is the temperature control for a house.
When the temperature of the house falls too low, the thermostat measures it and turns on a heater.
e.g. of Closed loop system temperature control systems (house thermostat) and cruise control systems (in vehicles).
5. Physical System
These are systems are system whose elements are tangible and components of the sub units are
physically connected to each other e.g. a computer system.
Physical System may be static or dynamic in nature. For example, desks and chairs are the physical
parts of computer center which are static. A programmed computer is a dynamic system in which
programs, data, and applications can change according to the user’s needs.
6. Abstract Systems
These are system which are conceptual (non-physical) in nature i.e. the system can only be visualized
or imagined but cannot be touched e.g. economic systems.
7. Static System
Static systems are systems which remain relatively the same in size, activity and scope of influence.
E.g. Mechanical systems.
8. Dynamic Systems
Are systems that constantly changing in size, activities and scope of influence e.g. Business system.
9. Deterministic System
System which performs in A predefined manner when subjected to a specific input i.e. their output
can be predicted or determined by looking at the input. For example, two molecules of hydrogen and one molecule of oxygen makes water.
10. Probabilistic Systems
System which do not perform in a defined manner when subjected to a specific input i.e. the output
cannot be determined from their input. Such systems operate based on chances and output can be
predicted up to a certain limit. E.g. Weather forecasting, mail delivery.
11. Stochastic system
Stochastic refers to a randomly determined process “pertaining to chance” For a system to be stochastic, one or more parts of the system has randomness associated with it. Unlike a deterministic system, for example, a stochastic system does not always produce the same
output for a given input. A few components of systems that can be stochastic in nature include
stochastic inputs, random time-delays, noisy (modelled as random) disturbances, and even stochastic dynamic processes.
12. Permanent System- persists for long time. For example, business policies.
13. Temporary System
System made for specified time and after that they are demolished. For example, A DJ system is set
up for a program and it is dissembled after the program.
14. Adaptive System
System that responds to the change in the environment in a way to improve their performance and to survive. For example, human beings, animals.
15. Non-Adaptive System
These is the system which does not respond to the environment. For example, machines.
16. Social System- System made up of people. For example, social clubs, societies.
17. In Human-Machine System,
In Human-Machine System both human and machines are involved to perform a particular task. For example, Computer programming.
18. Machine System
Systems where human interference is neglected. All the tasks are performed by the machine. For
example, an autonomous robot.
