In this paper, a theoretical mechanical model for the brake shoe is set up according to the foundation brake unit of railway freight cars, and it indicates that the friction moment is the origin resulting in brake shoe eccentric wear. On this basis, the pressure distribution formula on the brake shoe is derived when the train brakes in forward and backward direction respectively. The analysis results show that if the wheel and the brake shoe are concentric, the ratio of the revolving-in end pressure to the revolving-out end pressure in wheel forward revolving is larger than that in wheel backward revolving. It is consistent with the phenomena that upper eccentric wear often appears on the brake shoe in practice. Further research reveals that the degree of the eccentric wear is determined by the braking force action style, which is the theoretical basis for the design revision. In addition, the RecurDyn Multi-body Dynamics software is used to build the rigid-flexible coupling dynamics model for the foundation brake unit. The simulation experiment verified the analysis result. The research outcome provides the theoretical basis and technical support for further design improvement of the foundation brake unit in railway freight cars.

In order to develop actuation circuit for high pressure common rail injector solenoid valve, the high and low voltage time-sharing actuation control method based on current feedback was researched. A finite state machine tool called stateflow was used to establish the actuation model of solenoid, and the intelligent actuation control circuit was developed according to the model and MCU. The driving current can be adjusted automatically according to “Peak-High-Low” three-stage current, and the circuit can troubleshoot the state of solenoid. Driving Experiments on solenoid and injector were carried out and the results show the good performance of the intelligent actuation control circuit.

The multi-body dynamics model with rigid-flexible integration of the mechanicalhydraulic governor of diesel was set up based on the theory of computational dynamics of multi-body system. The initial conditions and boundary conditions were analyzed and added correctly to the components of the model. Then the working process of the mechanicalhydraulic governor was simulated, and the dynamic characteristics were analyzed. The results show that the model and the solving process are correct and credible. These pave the way for the further study about structure and capability optimum of the speed governing system. The whole analysis process provides a simple and feasible approach which can be used in other mechanical and hydraulic system.

Based on the analyses of the current solenoid valve driving circuits in marine diesel, a new type of dual-power double-maintain injector driving circuit is designed for marine high-pressure common-rail diesel. The circuit uses BOOST high voltage (80V) and storage battery low voltage (24V) to make up of dual-power time-sharing driver, which achieves automatic PWM feedback modulation of the solenoid valve injection current from the hardware. Experiments were carried out on a certain type of injector, the results showed that: the driving circuit had fast response time, only 0.045ms from zero to 22A of the solenoid valve current was required; the peak value of driving current has a good consistency, parameters including peakvalue current altitude, lasting time, maintain current altitude and maintain current lasting time could be adjusted flexibly. Besides, the circuit could be flexibly configured without occupying MCU resources.

In order to develop drive circuit for high pressure common rail injector solenoid valve, analysis the model of drive circuit and study the relation between voltage and electromagnetic response of solenoid valve. The controllable BOOST circuit was designed to provide the high voltage helping to improve electromagnetic response, and high and low voltage time-sharing driving circuit was designed based on current feedback control. Drive current can be adjusted automatically according to the peak current and holding current, with better consistency of peak current. The result of driving experiment for certain injector shows that: the new drive circuit has fast response, with only 0.045ms rising time for drive current reaching the peak value 22A, and peak current has good consistency.