Real-time estimation of roll angle and CG height for active rollover prevention applications

Roll angle and height of the center of gravity are important variables that play a critical role in the calculation of real-time rollover index for a vehicle. The rollover index predicts the real-time propensity for rollover and is used in activation of rollover prevention systems such as differential braking based stability control systems. Sensors to measure roll angle are expensive. Sensors to estimate the c.g. height of a vehicle do not exist. While the height of the center-of-gravity does not change in real-time, it does change with the number of passengers and loading of the vehicle. This paper focuses on algorithms to estimate roll angle and c.g. height. The algorithms investigated include a sensor fusion algorithm that utilizes a low frequency tilt angle sensor and a gyroscope and a dynamic observer that utilizes only a lateral accelerometer and a gyroscope. The performance of the developed algorithms is investigated using simulations and experimental tests. Experimental data confirm that the developed algorithms perform reliably in a number of different maneuvers that include constant steering, ramp steering, double lane change and sine with dwell steering tests.