give some ideas about line follower mobot

hi guys!!! we have a class about microcontrollers and we have'nt started our class. I just want to know in advance on how to create a sensor on a line follower mobot coz that will be our final project. im not really up to the detail. I just want to gather some ideas on how to make a sensor.
I want to ask something about PWM. If a servo motor is controlled by PWM, then how can I control a DC Motor using the same Microcontroller. we are planning to use a z8 microcontroller. can a microcontroller has two PWM? my plan for my mobot is to control both servo and DC motor so that I can control my dc motor during curves on the tracks. tanx guys for ur help!!

I suggest you google each of those items. there is a huge amount of information on the internet.

line sensors - you can buy or build. building a photoreflective line sensor is tricky, though. you will need shield phototransistor from the LED look at this sensor for a good line sensor - https://www.electro-tech-online.com/custompdfs/2006/10/QRB113x-1.pdf it may be hard to find in the PI but you might get some ideas from the datasheet.

PWM - there is a ton of info about PWM on the net. I believe zilog has app notes on PWM. lots of uCs have multiple PWM channels and you can also use a software version for robotic needs.

it is the MCU timers that control PWM, two or more timers are typical in z8