Method for detecting belt slip

A method for detecting belt slip of a belt drive driving a generator of an internal combustion engine, the belt drive including:

• i) a belt wrapped around a crankshaft pulley arranged on a crankshaft of the internal combustion engine, ii) a generator pulley arranged on a generator shaft of the generator, and, iii) a belt tensioner that can be adjusted in operation of the belt drive and adjusts a pre-tensioning force of the belt according to detected belt slip, the method comprising:
• recording a rotational speed profile of the crankshaft during an angular window of the crankshaft, defined by an equation m·360°, and forming an average value of crankshaft rotational speed from said rotational speed profile of the crankshaft,
• recording a rotation speed profile of the generator shaft, temporally independently of the recording of the rotational speed profile of the crankshaft, during an angular window of the generator shaft defined by an equation n·ü−1·360°, and forming an average value of generator shaft rotational speed from said rotational speed profile of the generator shaft,
• whether a rotational speed relationship between the average value of the crankshaft rotational speed and the average value of the generator shaft rotational speed is within a nominal range,
• adjusting the belt tensioner if the rotational speed relationship is outside the nominal range, and
• wherein m and n are real numbers and ü is a transmission ratio between the crankshaft pulley and the generator pulley.