ELECTRIC ASSIST SYSTEM AND ELECTRIC ASSIST VEHICLE

An electric power assist system generates an appropriate level of assist power while an electric assist vehicle is running on a slope and includes an electric motor that generates an assist power to assist human power of a rider of the electric assist vehicle, a controller that controls a magnitude of the assist power to be generated by the electric motor, and an acceleration sensor that outputs an acceleration signal representing an acceleration in a travel direction of the electric assist vehicle. The controller acquires speed information representing a running speed of the electric assist vehicle based on an external signal, detects an inclination angle of a road surface based on the speed information and the acceleration signal, and causes the electric motor to generate an assist power of a magnitude in accordance with the inclination angle.