No abstract

Density functional theory (DFT) was used to calculate the stability, oxygen reduction reaction (ORR) mechanism and activity of B-doped FeN 4 CNT (carbon nano-tube [CNT]) and FeN 4 G (G, graphene). The B-doped catalysts are more stable and active than that of the un-doped, especially for FeN 4 B2 G and FeN 4 B2 CNT. Based on the Mulliken charge and electrostatic potential surface of these catalysts, Fe atom is found to be the most active site for the adsorption of O-contained species. It is shown that their adsorption energies decrease in the range: O > OH > Co-ad OH > OOH > O 2 > H 2 O > H 2 O 2 on these catalysts. H 2 O 2 will be directly dissociated into two co-adsorbed OH* or O* + H 2 O* instead of H 2 O 2 on the graphene series catalysts, and the process of reaction (H 2 O 2 + * ! 2OH*) on the active sites of the CNT series catalysts is strongly exothermic. Hence, desorption of H 2 O 2 * into the solution is difficult to proceed during the oxygen reduction process. All the catalysts are expected to promote a single site four electron process through the reaction path of I (O 2 ! O 2 * ! OOH* ! O* ! OH* ! H 2 O) except for the catalyst of FeN 4 CNT. The rate-determining step (RDS) for ORR process on FeN 4 B2 G is the first reduction step (O 2 * ! OOH*), while the RDS is the fourth reduction step (OH* ! H 2 O) for the other catalysts. FeN 4 B2 G exhibits the largest onset potentials of 0.53 V, which is larger than the on-set potential of un-doped B FeN 4 G catalyst (0.39 V). In addition, the B-doped FeN 4 CNT catalyst shows the better activity compared to the un-doped ones.

In order to suppress the impact of a loads-induced gear dynamic load of a drum shearer cutting transmission system, an active torque compensation control method is proposed in this paper based on the active disturbance rejection and adaptive neuro-fuzzy control technologies. Using the speed difference between the motor rotor and the first stage gear as a feedback state variable, an active disturbance rejection torque compensation controller is firstly designed for suppressing the dynamic load of the electromechanical transmission system. The controller uses the speed difference as the tracking control target and sets it to a zero value, thereby transforming the dynamic load suppressing problem into a trajectory tracking problem. Secondly, the active disturbance rejection controller parameters are tuned based on the adaptive neuro-fuzzy control technology. Therefore, the torque compensation can be realized adaptively in accordance with the various cutting conditions. Finally, the suppression effect on the dynamic load of the transmission system under continuous impact conditions with different load mutation rates is analyzed based on the proposed control method. Simulation results indicate that the proposed method exhibits a good control effect in suppressing the dynamic load and an improved adaptive ability to the complex and changeable working conditions. The proposed method also can be useful for the electromechanical transmission systems with similar structure applied in other areas.

In order to study the electromechanical coupling dynamics characteristics of the drive motor and gear transmission system in the electric vehicle electric drive system, firstly, an electromechanical coupling dynamics model of the electric vehicle electric drive system is established; the electromechanical coupling vibration characteristics of the electric drive system under current harmonic excitation is compared and analyzed. The influence law of permanent magnet synchronous motor current harmonics on the meshing vibration of gear transmission system is revealed. The simulation results show that there is an obvious electromechanical coupling effect in the electric drive system; the harmonics of the drive motor can aggravate seriously the vibration state of the mechanical drive system; the research results provide a theoretical reference for further research on the vibration source positioning and active vibration reduction control strategy for the electric drive system of electric vehicles.

Aiming at the shortcomings of the automatic height control of the existing coal shearer drum, the control strategy of the coal shearer drums height adjustment sliding mode based on the variable speed reach law is proposed. Firstly, the mathematical model of the coal shearer height-adjusting cylinder is established, and the sliding mode switching function and its derivative including the deviation variable are derived. The exponential approaching law sliding mode controller is designed. Secondly, the hydraulic simulation of the drum height is established. The model compares and analyzes the control effects of traditional PID control and exponential approach law sliding mode control. The results show that the exponential approach law sliding mode control is superior to PID control in signal tracking dynamic response and steady state error; when the coal shearer is under load, the height of the drum under control of the exponential approaching law is basically unaffected; finally, the method of shifting the approaching law of dynamically adjusting the arrival speed by the fuzzy parameter optimization strategy is used to adjust the drum height. The simulation results show that compared with the traditional control method, the coal shearer control mode of the coal shearer drum based on the variable speed reach law not only ensures faster response speed and higher control precision, but also effectively reduces system chattering. Improve the reliability of the coal shearer cutting drive system.