Diagnostics system for a dual propeller drive unit

A computer implemented diagnostics system for a marine propeller drive unit, where the propeller drive unit is a self-balancing drive unit comprising a differential arrangement arranged to distribute an input drive torque from an electric machine between at least two propellers of a propeller system,

• the diagnostics system comprising processing circuitry connected to a speed sensor system associated with the propeller system and to a control unit associated with the electric machine,
• where the speed sensor system is arranged in connection to the differential arrangement to provide propeller speed data to the processing circuitry indicative of a speed of rotation of at least one propeller axle of the self-balancing propeller drive unit,
• wherein
• the control unit is arranged to provide motor current data to the processing circuitry indicative of a motor current drawn by the electric machine,
• the processing circuitry is arranged to monitor the motor current data from the control unit, and the propeller speed data from the speed sensor system, and to classify a state of the self-balancing propeller drive unit into a pre-determined number of states comprising one or more fault states, based on the motor current data and on the propeller speed data, wherein at least one fault state is associated with a detected anomaly in a spectral content of the motor current data such that the spectral content does not correspond to fixed multiples of the propeller speeds, and in that
• the processing circuitry is arranged to trigger an action by the diagnostics system in case the state of the self-balancing propeller drive unit is classified as a fault state.