Designing and implementation of PID controller based Quadcopter (Raspberry pi 3)

I need some suggestions (warnings are also appreciated). I am a fresh engineer, have little know how of designing and python language and haven't used raspberry pi yet (planning to learn it in next month). I am planning to design a quad copter (within one year duration), I don't know much about it and couldn't find much good information on Google (or you could say I couldn't digest it). My questions are:

1. What simulator should I use to design PID controller for quad copter?
2. I have heard about flight controller, It has built in different sensors and controls speed of motors. Basically I am trying to control my quad copter through PID controller so should I say that my designed PID controller will be flight controller?
3. What is difficulty level of designing PID controller?
4. Designin PID controller would be most difficult part or there would also be other difficulties?
5. After designing PID should I directly move to hardware or do I need to do something else before?
6. Type of hardware I should use? I am planning to make it autonomous, object following (through camera) so raspberry pi is good option to do so?
7. Most important, how much time do you think a newbie will require to design it?

Abdullah,
A lot of good questions here. I think you are a bit ambitious in your idea (or maybe I'm not understanding exactly) but it sounds like an interesting project. When you think of PID control,  you have to think of what you are controlling. Typically there will be a variable that you wish to control (say, distance to object). So the first thing is to choose what variable to use. Then you will have sensors to tell you how far off you are (you mentioned camera but may be others) and actuators (motors) that you can control to bring you to where you should be.

In a simple system the feedback loop is very small. For instance, you want a motor to run at a certain speed and use the PID algorithm to adjust the voltage to the motor to achieve that speed. For a quad copter, the feedback loop is going to be much larger which will make it more difficult to control. In fact, you will want to have PID control of each motor within the overall PID control.I would recommend to start with PID speed control for one motor. Once that is designed, you can use that design in your overall design.
Oh, and I would consider flight control to be the function that would give commands to set the variable you want to use your PID control.
Hope this is helpful for a start.

Thanks, I think what you want to say is:1. Design cascaded PID loop.2. Start from basic (already aiming for that).
I did some research and got almost all answers except one (it's new one):Can you suggest me an IMU that will be suitable for me? So far I have found MPU9250 (accelerometer, gyroscope, and a magnetometer) and 10DOF (accelerometer, gyroscope, magnetometer and a barometer)

Go to somewhere like Digikey , Mouser, etc, and type in IMU. You will need some idea of the specifications. Then you need to go to the manufacturers web site and look for software support and libraries to help speed up the development cycle. Sometimes these are not available directly from the manufacturer, but from users who are using the parts in projects. Again, a search will turn up this sort of information. Type in the  IMU name and "problems" for example, and see what you turn up. Lack of user documentation and support from the manufacturer was the biggest problem. I believe this is not as bad as it use to be, thanks to a lot of work by  early adopters of the hardware. Can't be any more specific than that, I went through this whole process a year ago, a lot will have changed in that time,cheers,Richard

AbdullahYou may find the following article by Tim Wescott helpful PID Without a PhD

I would like a chinese manufacturer to release a micro quad copter with the source code and ability to upload new code and a few spare usable buttons on the controller so I could experiment with a HoverAI but alas this kind of thing today is very rare. Why would you want more options?

I am assigned to build it from scratch. Sounds strange but for students usually these kinds of projects are preferred.

Thanks!

Thanks, will do it!