Estimation of Vehicle Shaft Torque Using Nonlinear Observers

Current closed-loop automotive shift control algorithms could greatly benefit if a measurement of the drive axle shaft torque was available. Direct measurements using strain gauges are too expensive for commercial applications. Magnetic pickup sensors that count the passage of gear teeth provide very inexpensive RPM measurements and are currently being used in production vehicles. This paper shows through simulations how these sensors can be used with a nonlinear observer technique (sliding mode) to estimate axle shaft torque from measurements of transmission output speed and driven wheel speed.