A Smart Measuring System for Vehicle Dynamics Testing

A fast measurement of the car handling performance is highly desirable to easily compare and assess different car setup, e.g. tires size and supplier, suspension settings, etc. Instead of the expensive professional equipment normally used by car manufacturers for vehicle testing, the authors propose a low-cost solution that is nevertheless accurate enough for comparative evaluations. The paper presents a novel measuring system for vehicle dynamics analysis, which is based uniquely on the sensors embedded in a smartphone and therefore completely independent on the signals available through vehicle CAN bus. Data from tri-axial accelerometer, gyroscope, GPS and camera are jointly used to compute the typical quantities analyzed in vehicle dynamics applications. In addition to signals such as yaw rate, lateral and longitudinal acceleration, vehicle speed and trajectory, normally available when working with Inertial Measurement Units (IMU) equipped with GPS, in the presented application the steering wheel angle is also measured, without additional sensors. The latter signal, besides being important for identifying the maneuver imposed by the driver, enables the usage of Kalman filters based on dynamic vehicle models (e.g. the single-track model) for the estimation of body sideslip angle. The system was tested during experimental campaigns on test tracks and the comparison between data from a professional measuring equipment and the Smart Measuring System showed a very good match. In the paper, hardware installation of smartphone and related accessories is discussed together with the main tasks of the algorithm implemented in the application, i.e. identification of smartphone orientation, steering wheel angle measurement, Kalman filter sideslip angle estimators (based on kinematic and single-track models). Furthermore, the time histories of the vehicle dynamics quantities during a lap on a handling test track are shown and compared with reference signals from the professional equipment. The proposed system proved to be a promising cost-A nd time-effective solution for vehicle dynamics testing.