Well, I wrote a book on exactly this topic - it's fairly reasonably priced on Amazon.com and I'm working on a second edition to provide better coverage of more recent topics like FreeRTOS - http://www.amazon.com/Real-Time-Embedded-Components-Computer-Engineering/dp/1584504684

Hi :

there are many examples of real-time system in our life, first we must know what is the real-time ...

Real-time is a more flexible word. If there is a network work with a speed 1 Kbyte/sec and the designed system can give an output by speed greater than 1 Kbyte/sec, it will be a real-time system with respect to that network, so it depend on the speed of the network and there aren’t a limited speed of execution to be a standard for real time that can according to it can be decided that the system is a real-time or not.

So , the MP3 player is a real-time system , sat lite receiver and routers also.

for study that , check this:

https://www.researchgate.net/publication/259216822_Creating_Real-Time_operation_System_Based_on_xPC_Target_Kernel

Article Creating Real-Time operation System Based on xPC Target Kernel

A frequently adopted definition of a real-time system is that in a real-time system not only the result of a computation is of importance, but also the time this very result is deliverd. E.g., in an antilock breaking system (ABS) not only the breaking pressure must be calculated, but also the time of application is critical to gain a functioning ABS.

Books on real-time systems are legion. One of my favorite books is "Real-Time Systems" by M. Krishna und Kang G. Shin. One of the most elaborated books is the one by Jane Lui (but IMHO it lacks a bit in comprehensibility). If you interested in designing specs for such systems you should have a look in control theory.

Example of a real time system is - a process control system. In a process industry the process parameters like temperature, flow, or pressure or status of a device (say a valve open or close) are continuously monitored and instant actions are initiated. A very simplistic house hold example is a Electric Geyser where water temperature is controlled in real time. Water is the media, Electric heater is source of heat. Thermostat is a sensor that puts off or puts on the heater basis the setpoint.

Actually, real-time systems are usually close-loop controlled systems as exampled by the above answers. If you are a beginner in this topic, it is better for you to know some initial knowledge about control theory by attending some courses or reading some relative books. I think you will have a good view of this topic after that.

There are several simple examples of real-time systems.

1. Room Air Conditioner which adaptively controls the temperature of a room.

2. Electric Power System which controls power quality parameters like Frequency, Peak Voltage, Power Factor, e.t.c.

3. Vacuum Control Systems which control the vacuum of a specific industrial chamber or vessel using different control strategies like PD, PID controllers e.t.c

There are so many examples around you.

Two of the more intuitive real-time systems that you can build in a general category called continuous media systems are:

1) Machine vision guided robotics (where an embedded or overhead camera is used to position a manipulator rather than position encoders and inverse kinematics - or use both) - I have found that this is great for teaching Rate Monotonic theory with hands on.

2) Digital audio decoding, transport over a network and encoding using a simple off-the-shelf sound card (VoIP or internet radio applications).

In the case of #1, you can see the effects of real-time response and computations used in guiding a robotic arm.

In the case of #2, you can hear any imperfections in real-time processing and transport with your ears.

Both are simple to build in a modest lab environment or in your home. To be accurate, you need to run off of interrupts and have microsecond or less latency on your hardware/software interface, so consider FreeRTOS and use of a simple camera port (ideally not USB since it has quite a bit of timing variation - or run low resolution on USB).

In general, systems take input and respond by producing outputs. Real-time systems are class of systems wherein there are strict timing restrictions on producing the outputs. The output needs to be appear every cycle (say 20s or so). Based on how strict the timing constraints are- real-time systems are further classified as hard-real time, and soft-real time. Hard real-time systems need to meet the timing requirement invariably, on the other hand soft-real time systems have some margin. A good survey paper to read is by Gambier- "Real-time control systems- A tutorial"

Dear Martin

Network Control Systems is one of the most important and promising real-time control systems.

I think the real time in control system are present in several fields of knowledge because all activities required precision of the time.

A real-time system means a system whose functioning monitored in real time e.g. in a process industry the process parameters like temperature, flow, or pressure or status of a component, failure, and repair are continuously monitored over time, examples are manufacturing industry, communication system, power system, aircraft industry etc

Any application that monitors static or dynamic behaviour of system continuously with respect to time is real time system. Traffic control systems or Process control based applications in industries are its appropriate examples.

The recursive least squares algorithm (RLS) is the recursive application of the least squares (LS) regression algorithm, so that each new data point is taken in account to modify (correct) a previous estimate of the parameters from some linear (or linearized) correlation thought to model the observed system. The method allows for the dynamical application of LS to time series acquired in real-time. As with LS, there may be several correlation equations and a set of dependent (observed) variables.

Years ago, while investigating adaptive control and energetic optimization of aerobic fermenters, I have applied the RLS algorithm with forgetting factor (RLS-FF) to estimate the parameters from the KLa correlation, used to predict the O2 gas-liquid mass-transfer, while giving increased weight to most recent data. Estimates were improved by imposing sinusoidal disturbance to air flow and agitation speed (manipulated variables). Simulations assessed the effect of numerically generated white Gaussian noise (2-sigma truncated) and of first order delay. This investigation was reported at (MSc Thesis):

Thesis Controlo do Oxigénio Dissolvido em Fermentadores para Minimi...

System where the results are definitely predictable , repeatable wrt time for safety of the function and system.

Autonomusation of systems leads them to real time system if it leads to human safety if not ensured.

Latency checks give clue on rts

Rm,

My final project for my Coursera 5318 is good - 1 Hz and 10 Hz observation of an external clock with a camera to save images that have no skips, no blurs, and no repeats. It is a reasonable challenge - you can get an idea of this by watching video or prior student projects. The Coursera course is here - Coursera: ECEA-5315, ECEA-5316, ECEA-5317, ECEA-5318