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The electronic control system of the variable nozzle turbocharger (VNT) was designed. The actuator is the electro-hydraulic servo proportional solenoid. The signals of the engine pedal position sensor, the engine speed sensor, the boost pressure sensor, the intake air temperature sensor, and the ambient pressure sensor are sampled and filtered. The engine working condition is estimated. The control algorithm was designed as the closed-loop feedback digital PI control together with the open-loop feed forward control. The gain-scheduled PI control method is applied to improve the robustness. The control system was calibrated at the turbocharger test bench and the engine test bench. The results indicate the designed control system has good performance for the boost pressure control under the steady and transient conditions.

Injection rate control is considered as an effective way to optimize diesel combustion process, decrease emission and improve fuel economy. There are many injection rate shaping devices, but most of them still suffer from structure complexity and parameter sensitivity which limit their effectiveness and practicality. A new initial injection rate control method in solenoid-controlled diesel injection systems is introduced in this paper. The basic idea of this method is to maintain a small spill passage between plunger chamber and inlet port during initial injection period. The initial injection rate can be regulated by changing the closing timing of the solenoid-controlled spill valve. This method has the advantages of simple construction, flexible adjustment and stable performance. Computer aided analysis and design based on a simulation program of the system is conducted to compare and select the sizes of the small spill passage according to their effect on injection characteristics.