hi,
I'm the new here.I want more advices and ideas from this electronic community to help me in doing this project.
Actually, this project is to develop a small truck model that equipped with digital speed control system. The truck should be able to travel uphill and downhill with a constant speed that had been digitally set in advance. the setting of the speed can be performed in such a way tat a numbers of bit input word are used to set the motors speed between 60 to 120 RPM (rotations per minute). In addition, the truck should also be able to keep a constant speed thoughout the journey regardless of the change of hill steepness or load carried. An electronic speed meter is vital and necessary to measure the truck's speed and display it in revolutions per minute (RPM) on a digits display.
I have some basic concepts before i start this project. It is to write a program to a microcontroller then this microcontroller has functions of setting the speed of the DC motor. Therefore, the DC motor will operate by moving the truck. Beside, the speed of the DC motor is adjust by the external device(Keypad) or variable resistor, thurs, the desire speed of motor can display on the 7-seg and the microcontroller can read it and operate the motor.
Now my questions are:
1) which microcontroller is the most suitable for doing this project and the advantages of specify microcontroller?
2)what kind of DC motor is suitable for this project as well?
3) does the mass of the truck will effect the speed of the truck?
4) what is the best way to let the truck moving uphill and downhill in the constant speed?
5)how is the speed detector can operate when the truck is moving?

(1) PIC or AVR. Pick one and use it.
(2)Any kind that is low enough voltage for your batteries but strong enough to move your car.
(3) Yes...of course.
(4) A tilt sensor- ball, electrolytic, or whatever can tell if you are on a slope or not. You need something else to tell the speed.
(5)You can use things like GPS or accelerometers or monitor how fast the wheel or motor is spinning with an encoder