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Real Time System Program, Task -> software, hardware it yields the result that is desired or expected or programmed. ? optimal system? -> within time -> within assigned time -> deadline. A -> B -> faster method -> we should do the task within assigned time -> deadline -> system optimal. For example: Machine/Humanoid Robot -> home based task -> sensors -> touches some heated elements -> perceives certain input -> output yield -> actions -> repel action -> within deadline. Air Traffic System -> within assigned time -> different stat -> weather -> traffic, -> build one system -> built a system ABS Braking -> time -> distributing force ( control system), a particular time frame under brake smoothly distributed apply -> accident prevents. Without Abs -> stop -> given time -> accident -> crash. -> non optimal results. Firmware/ Application RTOS Hardware Real Time System Understanding RTS?
What is a Real Time System? A computer system which responds to the time is known as Real-Time System. A system that satisfies bounded response time constraint or risk of system failure. In real-time computing, the correctness depends on the time at which the results are produced not only depends upon the logical result. A Deadline is the given time after an event when a response time has completed.
traffic control systems are examples for hard real-time systems. On-line transaction systems, airline reservation systems are soft real-time systems.
Basic Model of Real Time System: The basic model of a real-time system presents the overview of all the components involved in a real-time system. Real-time systems include various hardware and software embedded in such a way that the specific tasks can be performed in the time constraints allowed. The accuracy and correctness involved in real-time systems makes the model complex. There are various models of real-time systems which are more complex and are hard to understand. Here we will discuss a basic model of a real-time system which has some commonly used terms and hardware. Following diagram represents a basic model of Real-time System:
digital signals. Similarly, while transmitting the signals to the output conditioning unit the interface of signals are changed i.e. from digital to analog. On this basis, Interface unit is also of two types: โ Input Interface: It is used for conversion of analog signals to digital. โ Output Interface: It is used for conversion of digital signals to analog.
Examples of Real Time Systems.
โ In real life situations like controlling a tra c signal or a nuclear reactor or an Aircraft. โ Mobile Phones, Digital Camera, Microwave Oven โ Radar Control System, Industrial Process Control Command and Control โ Multimedia system Types of Real Time System: Real-Time system can be characterized as
- Hard Real-Time Systems
- Soft Real-Time Systems
- Firm Real-Time Systems
Soft Real-Time System: This System should meet timings constraints. Response time overrun leads to disastrous damage. Here utility value becomes less/drops with time
Digital Control System: Digital control system is an implementation of real-time system that are embedded in sensors and actuators and functions as digital controller.The plant term in the block diagram refers to a controllers system, for
example, an engine, a brake, an aircraft. The state of the plant is monitored by sensors and can be changed by actuators. The sensors read the current state of the plant in analog form i.e y(t) and computes a control output based on the di erence between analog sensor reading and reference input (desired state).The computing is done in control-law computation of the controller. The output generated from it is then converted to analog signal to feed the plant from actuator to bring the plant closure to desired state. The controllers in a complex monitor and control system are often organized in a hierarchy. There can be multiple control loops and the high-level controller interfaces with the operator and monitors the behavior of low-level controllers. The output of the high-level controller acts as the reference input of the low-level controller. Example of Control Hierarchy A hierarchical control system is a form of control system in which a set of devices and governing software is arranged in a hierarchical tree.
inputs to on-board flight management systems. Thus, the ATC system indirectly controls the embedded components in low levels of the control hierarchy. Real Time Application:
- VideoConference Application
- Voice over internet protocol
- Online gaming
- Chatting
Characteristics of Real Time Application Real-time System is a system that is put through real time which means response is obtained within a specified timing constraint or system meets the specified deadline.Real time system is of two types โ Hard and Soft. Both are used in di erent cases. Hard real time systems are used where even the delay of some nano or micro seconds are not allowed. Soft real time systems provide some relaxation in time expression. Characteristics of Real-time System: Following are the some of the characteristics of Real-time System:
- Time Constraints: Time constraints related with real-time systems simply means that time interval allotted for the response of the ongoing program. This deadline means that the task should be completed within this time interval. Real-time system is responsible for the completion of all tasks within their time intervals.
- Correctness : Correctness is one of the prominent part of real-time systems. Real-time systems produce correct result within the given time
- Distributed : In various real-time systems, all the components of the systems are connected in a distributed way. The real-time systems are connected in such a way that di erent components are at di erent geographical locations. Thus all the operations of real-time systems are operated in distributed ways.
- Stability : Even when the load is very heavy, real-time systems respond in the time constraint i.e. real-time systems do not delay the result of tasks even when there are several tasks going on at the same time. This brings stability in real-time systems.
