Abstract: A power assisted electric bicycle includes a body, a motor, a torque sensor, and a controller. The motor is operated in an operating period. The torque sensor is configured to output a plurality of torque signals corresponding to a pedal force. The controller is coupled to the motor and the torque sensor. The controller is configured to: receive the torque signals from the torque sensor; determine a peak and a valley, which is adjacent to the peak, among the torque signals; compute and determine a pedaling period between the peak and the valley, which is adjacent to the peak, among the torque signals; and generate an error signal associated with the torque sensor if it is determined that the pedaling period and the operating period fail to meet a default ratio.

Abstract: An optical system affixed to an electronic apparatus is provided, including a first optical module, a second optical module, and a third optical module. The first optical module is configured to adjust the moving direction of a first light from a first moving direction to a second moving direction, wherein the first moving direction is not parallel to the second moving direction. The second optical module is configured to receive the first light moving in the second moving direction. The first light reaches the third optical module via the first optical module and the second optical module in sequence. The third optical module includes a first photoelectric converter configured to transform the first light into a first image signal.

Abstract: A method is provided for tracking printed articles. Input indicating that a first carrier is being mounted to take up printed articles is read, and an ID of the first carrier is read in. A record associating the printed articles with the first carrier is made. In a preferred embodiment, the ID of the first carrier is read in by reading a bar code of the first carrier. Also provided is a system for producing custom printed articles.