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Electromagnetic force is crucial to the performance of the micro digital valve. The bigger electromagnetic force is needed to improve the rapidity of the micro digital valve. In the light of the traditional electromagnetic structure, which layouts the spring at the middle of the electromagnet, a new electromagnetic structure which sets the spring at the top of the electromagnet is studied. The relevant parameters and material are researched in the paper. The cross-sectional area of air gas and the electromagnetic force have a positive correlation relationship. The bigger driving current and the more turn of coil can increase the electromagnetic force in a certain range. The magnetic field would get the saturated state while driving current get a bigger value. At the moment, the magnetic force would not increase. Influence of magnetic material and non-magnetic material for valve seat is tiny. Electromagnetic force has a little difference between the two installation shells in the process of demagnetization. The simulation model is accurate and reliable. Using the simulation model, the electromagnetic cross section area, the different shell materials and the magnetic saturation phenomenon are simulated.

The principal purpose of this paper is to develop a new sliding sleeve which can overcome the inherent disadvantages of the present sliding sleeves. The working principle and structure of the device were explained. The novel energy source which adopted an accumulator was studied. Parametric optimization of the pipeline was developed by simulation study to avoid resonance. The key component, a new micro solenoid valve, was researched to control the sliding sleeve. The electromagnetic simulation was finished to research electromagnetic force. The compact structure which can satisfy the underground working environment was obtained. Design rationality of the novel intelligent sliding sleeve was validated by theory analysis and experiments. The novel intelligent sliding sleeve can meet the design requirements and perform well.

Safety is the most important issue for mobile and industrial machinery, and overspeed dropping of lifting actuators is extremely hazardous to the equipment, environment and operators. In this paper, to evaluate and improve the safety brake performance of hydraulic lifting systems in this emergent case, a multi-objective optimization model was proposed. Considering the load impacts in the braking process, a novel indicator named remaining vibration energy was defined to simply quantify the cushion performance. A mathematical and simulation model was established, and then the simulation model was verified by experimental tests. Minimization of the remaining vibration energy, the brake distance and the pressure loss of the hydraulic fuse on normal working conditions were considered as optimization objectives after analysis of the system dynamic behavior. The optimization model using a genetic algorithm was applied to a heavy hydraulic elevator system. The results indicated that the pressure impact was reduced, and the plunger stopped more smoothly in the optimized system. Also the brake distance and the pressure loss of the fuse are limited by the design criterion. Therefore, this paper presents an optimization method of hydraulic fuses to design safer hydraulic lifting systems.

A digital hydraulic valve is an important component of the digital hydraulic system, and its performance is directly related to the system function. In order to make the valve system more competitive in dimension, digital valve miniaturization is an important research point. A new micro digital valve is designed, which is analyzed from the mechanical structure and magnetic circuit mechanism, and the design difficulties are also expounded. The four subsystems and switching characteristics of the valve are theoretically analyzed and simulated. In order to test the performance of the valve, a test system is designed, and performance of the new micro valve is tested. The test results show that the switch characteristic analysis of the valve is correct. The comparison between the test curve and the simulation curve is carried out, which demonstrates that the accuracy of the simulation model is reasonable. The theoretical analysis of the new micro digital valve is consistent with experiments.