Dear Mr PaulS many thanks to you ,

Dear Mr JimboZA many thanks to you

I really appreciated that for you

Dear the case is very simple , but first , there is something to know that I constrained with some limitations that I couldn't overstep them , one of them is that the real world should be exactly as simulation for example in the simulation I consisted that robot started with (0,0) on coordinates x , y axis and I should put the goal point for example (10,20) and feed this point in the Artificial potential field method and then compute distance between robot and goal (so I don’t need any technique to determine the position of goal) and I don’t know if I could applied that.

the second constrain is that I should use the encoders of wheels to determine the current position of mobile robot and its orientation depending on a calculation formula (something like this

http://rossum.sourceforge.net/papers/DiffSteer/) even if that will be inaccurate .

I had a Rover 5 with two normal DC motors and two encoders (incremental rotary encoder) per each wheel , each encoder has four wires I don't know how to deal with them yet, and how could I translate the pulses of encoders or how to work out the x.y position of your robot based on the shaft encoder data..

I am still searching for ….

thanks a lot .