Method and system for controlling torque in a powertrain that includes an induction motor

A control system for controlling torque in a torque transfer drive having a torque input member and a torque output member, the system including a programmable digital processor having a memory in which control algorithms are stored and a central processor unit for executing control processing steps in accordance with control algorithm instructions, the steps comprising:

• commanding a change in torque on the torque input member;
• determining commanded q-axis and d-axis stator voltage;
• calculating the product of the collected stator voltage and a desired windowing function, the windowing function being a multiplier for stator voltage following a change in torque command to effect a correctly tuned slip gain estimate;
• calculating Q and D factors for a current transient event as a time integral of a windowed q and d axis stator voltage waveform;
• determining, using Q and D factors, whether an estimate of slip gain is accurate;
• and
• correcting the slip gain estimate based on the Q and D factors for a given change in commanded torque relative to a slip gain estimate that is correctly tuned.

A system for controlling torque in a driveline having a multi-phase induction machine, the induction machine having a rotor and a fixed stator that form a torque flow path from a torque input member to a torque output member, the system having a digital processor with a memory containing an algorithm that responds to rotor position and speed data to achieve a torque control that includes the steps of:

• establishing a commanded torque change input in the form of a commanded stator current in a rotor flux reference frame;
• determining the stator current in the rotor flux frame;
• determining the difference in the stator currents in the rotor flux frame;
• computing a stator voltage in the rotor flux reference frame that depends on the current difference;
• determining slip frequency and a first rotor flux angle corresponding to commanded torque as a function of estimated slip gain;
• measuring rotor angle;
• determining an estimated rotor flux angle based on the summation of the first rotor flux angle and the rotor angle;
• the stator current in the rotor flux reference frame being determined as a function of estimated rotor flux angle and current in a stationary reference frame for the induction machine.