Design of A Hydraulic Power Take-off System for the Wave Energy Device with An Inverse Pendulum

This paper describes a dual-stroke acting hydraulic power take-off （PTO） system employed in the wave energy converter （WEC） with an inverse pendulum. The hydraulic PTO converts slow irregular reciprocating wave motions to relatively smooth, fast rotation of an electrical generator. The design of the hydraulic PTO system and its control are critical to maximize the generated power. A time domain simulation study and the laboratory experiment of the full-scale beach test are presented. The results of the simulation and laboratory experiments including their comparison at full-scale are also presented, which have validated the rationality of the design and the reliability of some key components of the prototype of the WEC with an inverse pendulum with the dual-stroke acting hydraulic PTO system.

Capture Performance of A Multi-Freedom Wave Energy Converter with Different Power Take-off Systems

Among the wave energy converters (WECs), oscillating buoy is a promising type for wave energy development in offshore area. Conventional single-freedom oscillating buoy WECs with linear power take-off (PTO) system are less efficient under off-resonance conditions and have a narrow power capture bandwidth. Thus, a multi-freedom WEC with a nonlinear PTO system is proposed. This study examines a multi-freedom WEC with 3 degrees of freedom: surge, heave and pitch. Three different PTO systems (velocity-square, snap through, and constant PTO systems) and a traditional linear PTO system are applied to the WEC. A time-domain model is established using linear potential theory and Cummins equation. The kinematic equation is numerically calculated with the fourth-order Runge–Kutta method. The optimal average output power of the PTO systems in all degrees of freedom are obtained and compared. Other parameters of snap through PTO are also discussed in detail. Results show that according to the power capture performance, the order of the PTO systems from the best to worst is snap through PTO, constant PTO, linear PTO and velocity-square PTO. The resonant frequency of the WEC can be adjusted to the incident wave frequency by choosing specific parameters of the snap through PTO. Adding more DOFs can make the WEC get a better power performance in more wave frequencies. Both the above two methods can raise the WEC’s power capture performance significantly.

Research of Power Take-off System for “Sharp Eagle Ⅱ” Wave Energy Converter

The " Sharp Eagle” device is a wave energy converter of a hinged double floating body. The wave-absorbing floating body hinges on the semi-submerged floating body structure. Under the action of wave, the wave-absorbing floating body rotates around the hinge point, and the wave energy can be converted into kinetic energy. In this paper, the power take-off system of " Sharp Eagle Ⅱ” wave energy converter (the second generation of " Sharp Eagle”) was studied, which adopts the hydraulic type power take-off system. The 0-1 power generation mode was applied in this system to make the " Sharp Eagle Ⅱ” operate under various wave conditions. The principle of power generation was introduced in detail, and the power take-off system was simulated. Three groups of different movement period inputs were used to simulate three kinds of wave conditions, and the simulation results were obtained under three different working conditions. In addition, the prototype of " Sharp Eagle Ⅱ” wave energy converter was tested on land and in real sea conditions. The experimental data have been collected, and the experimental data and simulation results were compared and validated. This work has laid a foundation for the design and application of the following " Sharp Eagle” series of devices.

Power Absorption of A Two-Body Heaving Wave Energy Converter Considering Different Control and Power Take-off Systems

This study proposed a wave power system with two coaxial floating cylinders of different diameters and drafts.Wavebob’s conceptual design has been adopted in the wave power system.In this study,a basic analysis of the wave energy extraction by the relative motion between two floats is presented.The maximum power absorption was studied theoretically under regular wave conditions,and the effects of both linear and constant damping forces on the power take-off(PTO)were investigated.A set of dynamic equations describing the floats’displacement under regular waves and different PTOs are established.A time-domain numerical model is developed,considering the PTO parameter and viscous damping,and the optimal PTO damping and output power are obtained.With the analysis of estimating the maximum power absorption,a new estimation method called Power Capture Function(PCF)is proposed and constructed,which can be used to predict the power capture under both linear and constant PTO forces.Based on this,energy extraction is analyzed and optimized.Finally,the performance characteristics of the two-body power system are concluded.

Hydraulic Power Take-off and Buoy Geometries Charac-terisation for a Wave Energy Converter

In the past few decades, world energy consumption grew considerably. Regarding this fact, wave energy should not be discarded as a valid alternative for the production of electricity. Devices suitable to harness this kind of renewable energy source and turn it into electricity are not yet commercially competitive. The work described in this paper aims to contribute to this field of research. It is focused on the design and construction of robust, simple and affordable hydraulic Power Take-Off using hydraulic commercial components.

Application of the Latching Control System on the Power Performance of a Wave Energy Converter Characterized by Gearbox,Flywheel,and Electrical GeneratorGustavor

The latching control represents an attractive alternative to increase the power absorption of wave energy converters(WECs)by tuning the phase of oscillator velocity to the wave excitation phase.However,increasing the amplitude of motion of the floating body is not the only challenge to obtain a good performance of the WEC.It also depends on the efficiency of the power take-off system(PTO).This study aims to address the actual power performance and operation of a heaving point absorber with a direct mechanical drive PTO system controlled by latching.The PTO characteristics,such as the gear ratio,the flywheel inertia,and the electric generator,are analyzed in the WEC performance.Three cylindrical point absorbers are also considered in the present study.A wave-to-wire model is developed to simulate the coupled hydro-electro-mechanical system in regular waves.The wave energy converter(WEC)performance is analyzed using the potential linear theory but considering the viscous damping effect according to the Morison equation to avoid the overestimated responses of the linear theory near resonance when the latching control system is applied.The latching control system increases the mean power.However,the increase is not significant if the parameters that characterize the WEC provide a considerable mean power.The performance of the proposed mechanical power take-off depends on the gear ratio and flywheel.However,the gear ratio shows a more significant influence than the flywheel inertia.The operating range of the generator and the diameter/draft ratio of the buoy also influence the PTO performance.

The Method of Imbedded Lagrangian Element to Estimate Wave Power Absorption by Some Submerged Devices

A simple approach is described to estimate the wave power absorption potential of submerged devices known to cause wave focusing and flow enhancement. In particular, the presence of a flow-through power take-off （PTO） system, such as low-head turbines, can be accounted for. The wave radiation characteristics of an appropriately selected Lagrangian element （LE） in the fluid domain are first determined. In the limit of a vanishing mass, the LE reduces to a patch of distributed normal dipoles. The hydrodynamic coefficients of this virtual object are then input in a standard equation of motion where the effect of the PTO can be represented, for example, as a dashpot damping term. The process is illustrated for a class of devices recently proposed by Carter and Ertekin （2011）, although in a simplified form. Favorable wave power absorption is shown for large ratios of the LE wave radiation coefficient over the LE added mass coefficient. Under optimal conditions, the relative flow reduction from the PTO theoretically lies between 0.50 and 1 2 ≈ 0.71, with lower values corresponding to better configurations. Wave power capture widths, the sensitivity of results to PTO damping and sample spectral calculations at a typical site in Hawaiian waters are proposed to further illustrate the versatility of the method.

多源谐波激励HEV传动系扭振建模与特性分析

传动系扭振已成为影响混合动力汽车舒适性和驾驶品质的瓶颈问题,而动力源谐波扭矩是引发传动系扭转振动的关键,针对行星混联式混合动力汽车混合驱动模式下多动力源耦合驱动的特点,以研究行星齿轮传动系统的扭转振动特性为出发点,建立行星齿轮传动系扭振模型和考虑谐波激励的发动机和电机动态扭矩模型,选取混合驱动模式下整车高速匀速工况,开展四种扭矩激励模式下的传动系扭振特性仿真,研究多源谐波激励输入下的行星齿轮传动系耦合振动特性。结果表明,多源谐波扭矩会导致行星传动系输出端的平均转速降低、传动效率降低;发动机谐波扭矩引起的传动系转速波动要大于电机谐波扭矩所引起的;同时考虑发动机和电机扭矩谐波,行星齿轮耦合传动过程行星齿轮的扭转振动最为剧烈,齿圈作为行星传动的输出端,其扭振成分主要包含发动机2阶激励和电机的6阶、12阶激励,电机的谐波激励成分是发动机2阶激励的2倍之多。随着发动机与电机输出扭矩的分配比值增大,行星耦合系统中行星架和行星轮的扭转振动角加速度均方根值呈现增大趋势,而齿圈则呈现减小的趋势。

深度混合动力汽车的扭转振动特性研究

传动系的扭转振动是汽车振动的重要组成部分,对混合动力汽车而言,由于有两种或两种以上的动力源提供动力,因此混合动力传动系的扭转振动更复杂且形式更多样。本文研究基于国内自主研发的深度混合动力汽车,对其传动系的扭转振动进行了深入研究。研究结果为混合动力的开发提供了理论基础。

新型功率分流混合动力系统能量管理预测优化

针对新型双模功率分流混合动力系统,为改善拟搭载样车的能量经济性,开发了基于模型预测控制的实时优化能量管理策略并进行了仿真验证。通过分析各动力源在不同工作模式下的转速转矩关系,建立了功率分流系统模型。通过分析该构型方案在不同功率分流模式下的机械点,得到系统效率随传动比的变化关系,并基于发动机稳态燃油消耗特性曲线建立了其数学模型,基于安时积分法建立了动力电池一阶等效模型。根据已有的发动机模型及动力电池模型,建立了功率分流混合动力系统短时域预测模型,预测了有限时域内电池荷电状态及发动机燃油消耗率的变化。最后,基于预测时域内等效燃油消耗最小提出系统在混合动力模式下发动机工作点的最优决策律,并基于该最优决策律开发功率分流混合动力系统模型预测能量管理策略,实现了各动力源转矩的实时最优分配。设置预测时域和控制时域均为3s,新欧洲行驶工况仿真结果表明,该控制策略可实现能量管理的实时滚动优化,其百公里油耗为4.95L,相比于基于规则能量管理策略下的百公里油耗5.364L,可提升整车大约7.7%的燃油经济性。

野战加油车传动系结构参数匹配设计

分析了野战加油车传动系结构参数的设计原则,讨论了变速器最大、最小传动比及中间速比设计原则,阐述了传动系主要结构参数的设计思想。以某型野战加油车为例,对其结构参数进行优化匹配,从而提高了其动力性和燃油经济性。

摄动有限元法在汽车传动系扭振分析中的应用

将摄动有限元法引入到传动系扭振分析中,介绍了用摄动有限元法分析传动系扭振的基本过程,为快速而有效的分析传动系扭转振动提出了新的研究方法。指出了用摄动有限元法修改传动系扭振结构的一些注意事项,并提出了研究过程中可能面临的一些问题及应对方法,对传动系扭振特性研究具有一定的指导作用。

不同旋耕作业载荷下拖拉机动力输出传动系振动特性分析

为研究拖拉机旋耕作业载荷对动力输出传动系振动特性的影响,采用系统动力学建模、台架试验验证、田间试验与仿真分析相结合的方法加以分析。首先,在分析动力输出传动系结构的基础上,建立了描述其载荷传递机理的扭振耦合空间动力学模型,此模型详细考虑了横向和垂向的齿轮啮合传递效应。其次,利用拖拉机PTO加载试验台对模型的仿真结果进行试验验证,验证结果表明:横向和垂向的啮合频率误差最大分别为4.24%和5.12%,满足建模要求。然后,搭建了由无线扭矩传感器、北斗定位系统等组成的作业数据采集系统,分别采集了拖拉机在L1(2.07 km/h)、L2(3.10 km/h)、L3(5.29 km/h)常用挡位下的田间旋耕作业数据,田间试验结果表明:旋耕作业的载荷水平和波动范围均随着作业挡位、行驶速度的升高而增大。最后,利用所建立的动力学模型仿真分析了不同作业挡位PTO负荷对齿轮传递特性的影响,结果表明:拖拉机旋耕作业挡位越高,由PTO载荷波动所引起的传动系振动位移越大,而且主要体现在横向振动。

Research on Energy Conversion System of Floating Wave Energy Converter

A wave power device includes an energy harvesting system and a power take-off system. The power take-off system of a floating wave energy device is the key that converts wave energy into other forms. A set of hydraulic power take-off system, which suits for the floating wave energy devices, includes hydraulic system and power generation system. The hydraulic control system uses a special“self-hydraulic control system”to control hydraulic system to release or save energy under the maximum and the minimum pressures. The maximum pressure is enhanced to 23 MPa, the minimum to 9 MPa. Quite a few experiments show that the recent hydraulic system is evidently improved in efficiency and reliability than our previous one, that is expected to be great significant in the research and development of our prototype about wave energy conversion.

Connection Technology of HPTO Type WECs and DC Nano Grid in Island

Wave energy fluctuating a great deal endangers the security of power grid especially micro grid in island. A DC nano grid supported by batteries is proposed to smooth the output power of wave energy converters（WECs）. Thus, renewable energy converters connected to DC grid is a new subject. The characteristics of WECs are very important to the connection technology of HPTO type WECs and DC nano grid. Hydraulic power take-off system（HPTO） is the core unit of the largest category of WECs, with the functions of supplying suitable damping for a WEC to absorb wave energy, and converting captured wave energy to electricity. The HPTO is divided into a hydraulic energy storage system（HESS） and a hydraulic power generation system（HPGS）. A primary numerical model for the HPGS is established in this paper. Three important basic characteristics of the HPGS are deduced, which reveal how the generator load determines the HPGS rotation rate. Therefore, the connector of HPTO type WEC and DC nano grid would be an uncontrollable rectifier with high reliability, also would be a controllable power converter with high efficiency, such as interleaved boost converter-IBC. The research shows that it is very flexible to connect to DC nano grid for WECs, but bypass resistance loads are indispensable for the security of WECs.

Optimization of Bottom-hinged Flap-type Wave Energy Converter for a Specific Wave Rose

In this paper, we conducted a numerical analysis on the bottom-hinged flap-type Wave Energy Convertor (WEC). The basic model, implemented through the study using ANSYS-AQWA, has been validated by a three-dimensional physical model of a pitching vertical cylinder. Then, a systematic parametric assessment has been performed on stiffness, damping, and WEC direction against an incoming wave rose, resulting in an optimized flap-type WEC for a specific spot in the Persian Gulf. Here, stiffness is tuned to have a near-resonance condition considering the wave rose, while damping is modified to capture the highest energy for each device direction. Moreover, such sets of specifications have been checked at different directions to present the best combination of stiffness, damping, and device heading. It has been shown that for a real condition, including different wave heights, periods, and directions, it is very important to implement the methodology introduced here to guarantee device performance.

Theoretical and Experimental Study of A Coaxial Double-Buoy Wave Energy Converter

The double-body heave wave energy converter(WEC)is one of the most conducive devices to absorb the wave energy from relative motion while the law of which is not well understood.This paper makes an in-depth study on this wave energy converter,by means of the combination of theoretical analysis and physical model experiment.The hydrodynamic characteristics and energy capture of the double-buoy under constant and linear Power Take-Off(PTO)damping are investigated.Influences of absolute mass and mass ratio are discussed in the theoretical model.Relative displacement amplitude and average power output are tested in the experiment to analyze the effect of the wave period and outer buoy’s mass,while the capture width ratio(CWR)is also calculated.Results show that the wave period and mass of the buoys have a significant effect on the converter.Different forms of PTO damping have no influence on the optimal wave period and mass ratio of this device.It is recommended to select the double-buoy converter with a mass ratio of 0.80 and to place it in an area with the frequent wave period close to the natural period of the outer buoy to achieve the optimal energy capture.

Power enhancement of pontoon-type wave energy convertor via hydroelastic response and variable power take-off system

Wave energy has gained its popularity in recent decades due to the vast amount of untapped wave energy resources.There are numerous types of wave energy convertor(WEC)being proposed and to be economically viable,various means to enhance the power generation from WECs have been studied and investigated.In this paper,a novel pontoon-type WEC,which is formed by multiple plate-like modules connected by hinges,are considered.The power enhancement of this pontoon-type WEC is achieved by allowing certain level of structural deformation and by utilizing a series of optimal variable power take-off(PTO)system.The wave energy is converted into useful electricity by attaching the PTO systems on the hinge connectors such that the mechanical movements of the hinges could produce electricity.In this paper,various structural rigidity of the interconnected modules are considered by changing the material Young’s modulus in order to investigate its impact on the power enhancement.In addition,the genetic algorithm optimization scheme is utilized to seek for the optimal PTO damping in the variable PTO system.It is observed that under certain condition,the flexible pontoon-type WEC with lesser connection joints is more effective in generating energy as compared to its rigid counterpart with higher connection joints.It is also found that the variable PTO system is able to generate greater energy as compared to the PTO system with constant/uniform PTO damping.

车辆动力传动系扭转应力研究

为了较全面地了解动力传动系统内各个部件的振动特性,建立了某样车的动力传动系统扭振当量模型,研究变速器处于2档和5档时系统重要部件的扭转应力。

基于AVL-Cruise的车辆动力装置与传动系统匹配研究

通过对某新型轿车的设计目标进行分析,确定了该车型的基本结构型式。在给定动力装置的前提下,初选了多种传动系统匹配方案。应用软件AVL/Cruise对该轿车进行了整车建模,针对不同的动力装置与传动系统的组合进行了性能仿真与理论分析工作,最终选出了满足规定性能要求的变速器与主减速器的最优匹配。仿真结果表明:利用Cruise仿真平台可以显著缩短新车研发周期,减少研发成本。