The hydro-mechanical power split transmission is an important form of hydraulic hybrid transmission, combining the stepless speed characteristics of hydraulic transmission and the high efficiency of mechanical transmission. Recently, the hydro-mechanical power split transmission, with its relatively large potential for energy recovery and improving the environment, and its low cost, has attracted many scholars from all over the world. Because there are many types of hydro-mechanical power split transmission, the different forms are complex, and researchers across the world are relatively dispersed, it has experienced a long and arduous development process. Therefore, it is important to summarize the types, developments, and achievements of this transmission. From the recent literature at home and abroad, this paper summarizes developments, key techniques and trends, analyses problems and difficulties in design and application, discusses the methods for solving these problems, and provides references for the development and application of hydro-mechanical power split transmission.
A water budget model is proposed to estimate the infiltration, runoff, evapotranspiration and recharge in vadose zone and apply to a case study. The instantaneous redistribution of infiltrated water is assumed to be uniform and a linear relationship between evapotranspiration and effective saturation is imposed. Infiltration is described by Philip's solution in conjunction with the time compression approximation method during rainfall. Runoff occurred when rainfall rate exceeds soil-infiltrating rate. The soil profile drainage was determined by evapotranspiration and recharge. Cumulative infiltration, runoff, evapotranspiration and recharge are estimated with different climate conditions and different soil hydraulic properties during simulating period. Analysis shows that initial effective saturation affects the estimated results in this water budget model in the short or mid-term simulations while not in long-term simulations. The climatic conditions of Yun-Lin plain area, Taiwan from 1991 to 1997 are used by referring to hydrological and hydrogeological parameters to provide the computational procedures of this study for estimating recharge. Results showed that the amount of annual recharge was affected by the amount of annual rainfall and soil properties. Nomenclature A = Parameter related to sorptivity [L 1/2 ] a = Infiltration constant [−] D = Diffusivity [L 2 T] d r = Depth of water reservoir [L] E = Evapotranspiration flux [L T −1 ] E p = Potential evapotranspiration rate [L T −1 ] i = Infiltration rate [L T −1 ] k = Unsaturated hydraulic conductivity [L T −1 ] k s = Saturated hydraulic conductivity [L T −1 ] P = Rainfall intensity [L T −1 ] P cum (t) = Cumulative rainfall [L] S = Sorptivity [L T −1/2 ] t = time [T] t e = Equivalent time to ponding [T] t p = Ponding time [T] 484 J.-F. CHEN ET AL. q = Unsaturated water flux [L T −1 ] q cum ie (t) = Amount of infiltration excess runoff [L T −1 ] q cum se (t) = Amount of saturation excess runoff [L T −1 ] q r = Recharge flux [L T −1 ] φ = Effective saturation [−] φ 0 = Initial effective saturation [−] λ = Pore size distribution index [−] θ = Volumetric water content [−] θ 0 = Initial volumetric water content [−] θ r = Residual water content [−] θ s = Saturated water content [−] h = Soil pressure head (<0 if soil unsaturated) [L] h s = Air entry value [L] h 0 = Initial soil pressure head [L]
Pantograph-catenary disconnection occurs quite frequently in high-speed situations. Pantograph arcing has a significant impact on the contact surfaces and power quality. This article focuses on the effect on the electrical characteristics of the four-quadrant converter of pantograph arcing. An arc model which combines Cassie's arc model with Mayr's arc model is built. This article mainly researches the influence of the pantograph arcing on the four-quadrant converter in different durations. Pantograph arcing leads to voltage pulse in voltage, as well as the harmonics in the current of the alternating current side. At the same time, the direct current voltage decreases when the arc occurs. Therefore, it can ultimately decrease the output torque and increase the torque pulsation of the motor.
This article deals with fault isolation issue for the redundant thrusters of frame-structure unmanned underwater vehicles (UUVs). Consistency check is adopted to accomplish this task while solving the reformed control input equations that are produced after getting rid of some fault-free terms from the given equations. Specially selected column vectors from the given control matrix together with the corresponding hypothetical thrust output faults are taken as the known/unknown elements for these equations. Redundant relations among the thrusters support the vector selection, which are revealed by analyzing the maximally linearly independent vectors of the given control matrix. Simulation with faulty thrusters under redundancy in a frame-structure unmanned underwater vehicle illustrates the effectiveness of the proposed methodologies.
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