The existing semi-active suspensions are very expensive and difficult to be popularized. Therefore, the search for the low-cost semi-active suspension has become a hotspot. To reduce the product cost of semi-active suspensions, this study proposed a new hydraulic semi-active suspension system based on road statistical properties and creates an identification method of road conditions. Firstly, the working process of the proposed semi-active suspension was given. Then, the formula for calculating the mean square value of the body acceleration under the running road condition was derived. Based on the formula, the road identification method was created. Finally, the road test was carried out using a test vehicle. The identified road PSD (power spectral density) values are all consistent with the real values. The test results show that the road identification method can effectively perceive the actual road grades. The identification interval with 20 s can meet the requirements of practical applications. The slight fluctuation of the running speed v has little effect on the identification results because of the statistical characteristics of road conditions.

The lightweight design of trucks is of great importance to enhance the load capacity and reduce the production cost. As a result, the taper-leaf spring will gradually replace the multi-leaf spring to become the main elastic element of the suspension for trucks. To reveal the changes of the handling stability after the replacement, the simulations and comparison of the taper-leaf and the multi-leaf spring suspensions with the same vertical stiffness for trucks were conducted. Firstly, to ensure the same comfort of the truck before and after the replacement, an analytical method of replacing the multi-leaf spring with the taper-leaf spring was proposed. Secondly, the effectiveness of the method was verified by the stiffness tests based on a case study. Thirdly, the dynamic models of the taper-leaf spring and the multi-leaf spring with the same vertical stiffness are established and validated, respectively. Based on this, the dynamic models of the truck before and after the replacement were established and verified by the steady static circular test, respectively. Lastly, the handling stability indexes for the truck were compared by the simulations of the drift test, the ramp steer test, and the step steer test. The results show that the yaw rate of the truck almost does not change, the steering wheel moment decreases, the vehicle roll angle obviously increases, and the vehicle side slip angle slightly increases after the replacement. Thus, the truck with the taper-leaf spring suspension has better steering portability, however, its handling stability performs worse.