Performance of Virtual Torque Sensor for Heavy Duty Truck Applications

Automotive companies are constantly looking to increase the fuel efficiency, shift quality, passenger comfort, and to reduce wear and tear on the components. Most of these aspects depend on the accuracy of torque used for transmission control, which determines the required operational gear position at a given speed and road conditions. Currently, SAE J-1939 CAN bus torque estimation relies on steady state maps that are generated during the calibration of the engine for different speeds and loads. In this paper we report the development of a Virtual Flywheel Torque Sensor (VFTS) useful for real time torque measurement based on an engine speed harmonics analysis. The VFTS uses a signal from the flywheel speed sensor to estimate the flywheel angular acceleration, which and provides a proportional torque value which corresponds to torque at the flywheel. The performance of the VFTS is evaluated using an engine with flywheel attached to driving a dynamometer at different torque loads (100%, 75%, and 50% load) and different speeds (900-1800 RPM). The accuracy of the sensor was found to vary within from 2-12% in the load range tested. The dynamometer test results are further validated using 1D AMESim engine modeling and simulation.