give help for following robot

[m_javad_m]

I wanna take part to robot match, my robot must folowing wire that has 2amper current and have 50Hz frequency.
I want give some idea for building it. for recognition the wire i use armature winder,I give answer by this way the questions I have is:
1-how many armature winder i must use to give the better result. (if i use 3 you think that's enough or no)
2-speed is importand for me, now what kind of motor is better for this robot(steper motor or usual motor whit gearbox):confused:

[franklin97355]

I guess the first question (from me) is how big? Small robots can use modified servos or small dc motors without gears.