Implementing a Control System

Another good answer.

Learning theory is the first step. Learning to make the theory work in the real world is another significant task.

I'll add that the P&ID in PWSlacks good answer refer to Proportional, Integral and Differential. This gives a hint that PID controllers have both mathematical power and implementation complexity.

I have always assumed that P&ID stood for Process & Instrumentation diagram

I have heard it both ways. But I prefer to us piping rather than process. The piping and instrumentation, allows you to understand the process.

http://en.wikipedia.org/wiki/Piping_and_instrumentation_diagram

The world is analog at its basic, so are control systems. Whatever you do, you have to adapt your design to the physical design as it exist at the physical plant. If it is PID pneumatic actuators, that is what is given. If the sensors and instrumentation is Analog electrical output, that what is you have to live with. After you adapted yourself to this situation, it does not matter much, if the core control is analog or a microprocessor. You will have to implement, and tweak the same functions. Largely, it matters, which can you or your helper can handle competently. Incompetent help is worse, than none.

Then the real fun starts, when you have to demonstrate in real system, that it works. Sort of or better.

My question is: How a control system is implemented?

A lot of microcontrollers these days have built in Analog-to-Digital (A/D) and Digital-to-Analog (D/A) converters. Connect the sensor to the (A/D) input and your actuator to the D/A output through any necessary analog electronics to offset and scale your voltages and write your microcontroller code to do the necessary math in between.

The theory of controls is the foundation of how modern industry is controlled, not with the idea of eliminating worplaces as some would say, but rather to make uniform quality products by eliminating waste, excess energy use, reducing rework, etc.

As with everything you need a basis, which you are getting, but then comes the real world, where there are several basic constraints that we need to abide with one is not to reinvent the wheel, unless you have a genius stroke and can design something cheaper and better than what is in the market and second is that control systems like most anything in the world need to comply with many standards and codes, which makes a replacement by a microprocessor and an output card difficult to implement.

Now then A PWSlack mentioned the basis for most control implementations starts with several things like a P&ID that defines what needs to be controlled and how hopefully, then a review of the applicable standards and codes so that you can pre select the control system and components and finally the design and cost issues which every client want to me the simplest and cheapest.

So based on this can a control system done with a microchip and some software the answer is yes, will it fly in the real world, probably not.

So I would suggest that you further your education and contact suppliers of control systems to learn what is available and try to work with a company where they will allow you to learn under a professional before flexing your wings and ideas.

. . . How a control system is implemented? . . .

It all depends on what you are controlling and design constraints. If it is the simple control of a single actuator and you are only making one, you can find off the shelf boards to accomplish the function. If you are designing for a consumer product and thousands are to be produced, it may be more cost effective to design and build your own boards especially if there are packaging contstraints. If you are designing a control system for a complex machine or factory there are other options.

Hardware: Search "PLC" and you will find a class of hardware available from many suppliers that is designed for the industrial environment. Spend some time looking over the offerings. You will even find some application notes which will help you get familiar with the actual design and implementation of a control systems.

You will find that there a class called "Safety PLC". Safety PLCs essentially have two controllers running in parallel checking each other. (Caution here: When designing, safety comes from the architecture and careful design. It is up to the designer to put the controlled equipment into a sequenced safe state when a failure is detected. Just selecting Safety devices does not accomplish this.)

Software: Within the Programmable Logic Controller world you will find that there are multiple programming languages with multiple user interfaces. Some have graphical interfaces, some will work with traditional code such as C or basic, some work with Ladder Logic and some allow the languages to be mixed. The language that you select is a match of the functions that you want to accomplish and your proficiency in the available languages.

Thanks a lot for your replies guys :)

So from reading all the answers, this is what I understand so far: A control system can be implemented using purely analog circuitry (by tuning the frequency response) and can also be implemented by a microcontroller then program it. And the choice depend on the applications and constraints.

Please correct me if i am wrong :)

Thanks again guys :)