Patent ID: 7203578

Claim:
A method for determining driving wheel torque for a vehicle having a hybrid electric powertrain, the powertrain comprising an engine, an electric motor, a battery, a generator and gearing that define plural torgue flow paths from the engine and the motor to a torque output shaft, the powertrain having a parallel operating mode in which the engine and the motor together solely define a power source and a non-parallel operating mode in which the engine, the generator and the motor solely define a power source, and a powertrain controller for controlling power distribution to vehicle traction wheels; the method comprising: measuring values for motor speed, generator speed, engine speed, motor torque, generator torque, engine torque and storing these values in the controller; calculating an angular acceleration for the motor; calculating an annular acceleration for the engine; determining whether the powertrain is operating in the parallel operating mode or in the non-parallel operating mode; calculating a combined moment of inertia for the motor and a gearing element to which it is connected; calculating a combined moment of inertia for the generator and a gearing, element to which it is connected; calculating a combined moment of inertia for the engine and a gearing element to which it is connected; calculating torque ratio of gearing between the generator and the motor; calculating torque ratio of gearing between the engine and the motor; calculating torque ratio of gearing between the motor and vehicle traction wheels; calculating static gearing output torque at the motor when the powertrain is in the parallel operating mode as a function of torque ratio of gearing between the engine and the motor, engine torque, the combined moment of inertia of the engine and a gearing element to which it is connected, and angular acceleration of the engine; calculating static gearing output torque at the motor when the powertrain is in a non-parallel operating mode as a function of torque ratio of gearing between the generator and the motor and generator torque; and estimating total wheel torque as a function of torque ratio of gearing between the motor and the traction wheels, torque of the motor, static gearing output torque, combined moment of inertia of the generator and a gearing element to which it is connected, angular acceleration of the engine, the sum of the combined moment of inertia of the motor and a gearing element to which it is connected and the combined moment of inertia of the generator and a gearing element to which it is connected and engine angular acceleration; whereby total output torque at the traction wheels for given operating conditions is estimated to permit control of traction wheel torque and ensure that actual powertrain output torque corresponds to a torque command by the controller.