Assume that you will design a flight controller for a quadcopter. Investigate and report below items. The items represent open-ended questions. Briefly, conduct a survey on the flight controllers of quadrotors and explore a design path which can be followed by you when you build your own flight controller. 

a) Modeling methods and tools of quadcopters. sensor types and modern sensor products. 

b) Actuator technology and modern components, position and attitude estimation methods and filters. 

c) Computation devices that can realize the onboard flight controller. 

d) Physically and practically realizable controller desgin methods, and modern development tools.