Method of Determining Torque in a Mechanical Drivetrain

A method for determining torque in a drivetrain in real-time, comprising the steps of:

• receiving an initial commissioning reference signal at a motor drive, wherein the commissioning reference signal corresponds to a desired commissioning run of a motor connected to the motor drive and of a portion of the drivetrain;
• determining a torque at a location along the drivetrain other than an output shaft of the motor during the commissioning run;
• receiving a subsequent reference signal at the motor drive, wherein the subsequent reference signal corresponds to a desired operation of the motor;
• generating an output current from the motor drive to control operation of the motor responsive to the subsequent reference signal;
• measuring the output current from the motor drive as it is supplied to the motor while executing the subsequent reference signal;
• determining an electromagnetic torque for the motor using the motor drive, wherein the electromagnetic torque is determined as a function of the output current measured while executing the subsequent reference signal;
• and
• determining the torque at the location along the drivetrain while executing the subsequent reference signal as a function of the electromagnetic torque and of the torque determined at the location during the commissioning run.

A system for determining torque at a point of interest along a drivetrain in real-time without a sensor mounted at the point of interest, the system comprising:

• a motor operatively connected to drive the drivetrain;
• and
• a motor drive operatively connected to control operation of the motor, wherein the motor drive further comprises:
• a current sensor operative to generate a current feedback signal corresponding to a current supplied from the motor drive to the motor;
• and
• a processor operative to:
• execute at least one commissioning run of the motor, wherein the at least one commissioning run controls operation of the motor according to a known motion profile,
• store either an operating parameter or at least one transfer function coefficient in memory, wherein the operating parameter or the at least one transfer function coefficient corresponds to a torque produced at the point of interest during the at least one commissioning run,
• execute at least one additional run after the commissioning run,
• determine an electromagnetic torque in the motor as a function of the current supplied from the motor drive to the motor during the at least one additional run, and
• determine a torque generated at the point of interest in real-time during the at least one additional run as a function of the electromagnetic torque and the operating parameter or the at least one transfer function coefficient.