Need a guidance about mobile robot implemtation

Hi all,
** I am working on design a mobile robot that should navigate from its initial point to goal point without collision with any obstacles dependent on the Artificial Potential Field algorithm , from my a little bit knowledge , that I will need these components below, please correct to me if there is any additional or shortage components :**
1- Two servo-motors (which had encoders) one per axis to determine heading angle and coordinate x-y of mobile robot .
actually this component is the main one should I get , but if there is a specific type you could advise me to buy it , please need your help in this.
2- Five ultrasonic sensors to detect obstacles .
3- H-BRIDGE (Motor Drive Shield) for servo-motors : actually I don't know if I need this component or not but I see many tutorial use these when it has two normal DC motor to control . need your help
4- Arduino UNO kit
5- Batteries : actually also I don't know which type that my work required (4x AA or 6x AA ... etc.)
6- Two capacitors one per servo-motor to help reduce RF noise .
7- Breadboard
8- Wires and cables for connections
Any help or ideas you offer would be highly appreciated.
Many thanks.

3- H-BRIDGE (Motor Drive Shield) for servo-motors : actually I don't know if I need this component or not but I see many tutorial use these when it has two normal DC motor to control . need your help

Servos do not need an H-Bridge.

8- Wires and cables for connections

Get only red ones at least three feet long. NEVER cut one. Just wad up the excess, like every other "it doesn't work" project posted here.

Are you using servos for locomotion or to point rangefinders?

PaulS:

3- H-BRIDGE (Motor Drive Shield) for servo-motors : actually I don't know if I need this component or not but I see many tutorial use these when it has two normal DC motor to control . need your help

Servos do not need an H-Bridge.

8- Wires and cables for connections

Get only red ones at least three feet long. NEVER cut one. Just wad up the excess, like every other "it doesn't work" project posted here.

Dear PaulS many thanks to you , but where the project ?

groundfungus:
Are you using servos for locomotion or to point rangefinders?

Dear groundfungus many thanks for reply
I want to use servos motors in locomotion ( to transport robot from place to place) and in the same time I need them in odometry (to determine heading angle and coordinate x-y of mobile robot with help of encoders the motor has)

Many thanks

For locomotion, you would normally use "continuous servos". They have the internal pot (encoder) disabled, so give no feedback as to position. For your robot maybe consider regular DC gearmotors driven with H-bridges and with encoders on the motors or wheels.