On-line estimation of road profile in semi-active suspension based on unsprung mass acceleration

•A novel on-line estimation method of road profile is proposed for the semi-active suspension.•The estimator is robust considering the variable system parameters and vehicle velocity.•The effectiveness of this method is validated by two groups of tests. As the main excitation source in the process of vehicle driving, road roughness directly affects the vehicle ride comfort and handling stability. In this paper, an on-line estimation method of road profile based on vehicle dynamic response is proposed, which estimates the road disturbance using the transmission characteristics of the system and realizes the road roughness classification by calculating the road information via Power Spectral Density (PSD) estimation. Since the existing standard calculation method of PSD of road disturbance can only be used to process continuous data, an approximate method suitable for discrete data is proposed. In addition, in order to coordinate the response speed and estimation accuracy of the system, the mechanism of the influence of time-window on the estimation accuracy is studied, and the optimal length of time-window is determined. The estimation accuracy under the condition of sprung mass and damping coefficient variation is also analyzed. Finally, a 1/4 semi-active suspension test bench is conducted, and the results show that the system parameters (sprung mass and damping coefficient) and driving speed have little effect on the accuracy of road estimation. At the same time, the accuracy of on-line estimation method of road profile under five different levels of road is more than 90%, and the overall estimation accuracy rate reaches 98.5%, which verifies the effectiveness of on-line road estimation method.