Which kind of leads to another question since John mentioned it...
If you had a regulated power supply with enough amperage capability...would it in fact act like a cruise control?
Say...crank the power supply to 18 volts...regulate it down to 10 so that the engine always sees 10 volts...on a flat with no grade speed would be constant...yes?
Then...you add a pot on the board to dial in your speed (voltage)...and cruise...maybe...