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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.

To realize the precise control of injection and ignition of compressed natural gas engine, the 32-Digit PowerPC561 was selected as the single-chip microcomputer for the compressed natural gas engine. The signal processing module, controller module and power driver module of the engine control system were introduced successively. In the injection valve drive circuit, a new design method realized the ‘Peak&Hold’ drive current wave shape, which reduced the software work of injection development. In the ignition module circuit, the feedback of the time of ignition persistence and preliminary coil close period were successfully realized. The Engine Control Unit (ECU) has flexible control functions, which fulfill the requirements of engine control system.

At first, the dynamic electromagnetic characteristics of a pulsed solenoid valve is analyzed by experiments. The fast valve response is obtained by material modifications. Then, the intelligent solenoid driving method is discussed. The new techniques of the “active” PWM and the “d2i/dt2” detection are developed for feedback control of the solenoid holding current and the valve closure timing. Finally, the control and diagnosis method for the valve closure duration is investigated. A sensing mechanism utilizing momentary camshaft speed fluctuations of fuel injection pump is presented, which provides the basis for feedback control and diagnosis of the valve closure duration and diesel fuel injection process.