System and method to characterize and compensate steering universal joint torque fluctuation

A system for compensating torque fluctuation in a steering column having at least one universal joint, the system comprising:

• an electric motor operably coupled to the steering column;
• an inverter configured to supply power to the electric motor;
• a steering angle sensor configured to measure an input steering angle of the steering column;
• an output angle sensor configured to measure output angle of the steering column;
• and
• an electronic control unit in functional communication with the inverter and configured to:
• determine a steering angular velocity value based on the input steering angle of the steering column;
• determine a TAS angular velocity value based on the output angle of the steering column;
• determine an angular velocity ratio signal based on a ratio of the steering angular velocity value and the TAS angular velocity value;
• determine, across a predetermined ranges of values of the input steering angle, a maximum value of the angular velocity ratio signal;
• determine, based on the maximum value of the angular velocity ratio signal, an equivalent angle and an equivalent phase, wherein the equivalent angle and the equivalent phase together characterize the torque fluctuation in the steering column generated by the at least one universal joint;
• determine a compensation torque signal based on the equivalent angle and the equivalent phase;
• and
• command the inverter based on the compensation torque signal to cause the electric motor to produce a compensation torque to compensate for the torque fluctuation in the steering column.