Output torque control method

Readings of multiple sensors are utilized to estimate transmission output, which is used as a feedback signal to control the torque capacity of a transmission clutch. Some sensor readings, such as transmission output speed, are used to compute an input vector. Then, a current state vector is computed as a linear function of the previous state vector and the input vector. One of the values in the state vector is shaft twist, which is proportional to transmission output torque. Various other sensor readings, including wheel speed, are used to correct for noise. Wheel speed signals are received with a delay. To accommodate this delay, the state vector is expanded to include estimates of wheel speed at various past points in time. An accelerometer reading is used at very low speeds at which the wheel speed sensor and transmission output speed sensor are unreliable.