Based on modelling and experimental validation of the hydropneumatic spring, a non-linear dynamic model is developed for active hydropneumatic suspensions of a special-purpose vehicle. In order to improve the system response to off-road terrain unevenness and vertical impact force, the non-linear system is transformed into a linear one by means of feedback linearization. Furthermore, a sliding mode control strategy is introduced for the purpose of raising the robustness of the system. The simulation results indicate that the present non-linear controller combining the feedback linearization with the linear control algorithm possesses high control accuracy and strong robustness, and the unique requirements for the special-purpose vehicle are therefore fairly well satisfied.

It is urgently necessary to develop practical programs for different purposes in the field of wastewater treatment. Now the design programs for grit chambers, anaerobic ponds, facultative ponds, aerobic ponds, aerated ponds and polishing ponds are being developed. Programs for automated plotting and man-machine interactive plotting are needed too. By using AutoCAD (Version 9.03 or 10.0), a secondary development of the softwares for engineering drawing of stabilization pond has been developed, which possesses the function of writing out explanatory notes. A program for writing out explanatory notes in Chinese is also being developed. In the process of developing such softwares, high-level language AutoLISP is used, so that the softwares possess artificial intelligence. Up to now the graphic softwares for plotting the general plan drawings and elevation drawings of grit chamber, various ponds, and pond systems have been developed.