A study on the effect of electronic engine speed regulator on agricultural tractor ride vibration behavior

In this study, the effect of electronic speed adjustment on tractor ride vibration levels is examined. With normal pedal operation the engine rotational speed drops with an increasing load. The electronic regulator provides a constant speed mode of operation independent of the load. Vibration levels were measured under different operating conditions and surfaces. As a first series of tests, the tractor was driven on a conglomerate bituminous track at speeds of 20, 25 and 28 km/h. Vibration was measured upon the surface of the operator seat simultaneously in the x, y and z directions. The reference axis system was that defined by the ISO 2631-1 [1]. The weighted r.m.s. acceleration was found to be between 8% and 8.6% higher for the case where operation with electronic speed adjustment had been selected. Secondly, cultivating was chosen as the field task and the vibration was measured while the tractor was traversing a rough farm track at speeds of 6, 7.5 and 9 km/h. In this case, the vibration levels with automatic speed adjustment were between 4.3% and 8.6% lower than when driving with normal foot pedal operation. From the above results, we may infer that electronic speed regulation should not be used in transportation on asphalt country roads. On the contrary, it seems that electronic regulation has an advantage when used in typical field tasks such as cultivating.     

Electro-hydraulic tillage depth control system for rotary implements mounted on agricultural tractor Design and response experiments of control system

A tillage depth control system for rotary implements mounted on an agricultural tractor was designed and constructed to improve accuracy of tillage depth. The control system was composed of five main units: (1) a detecting unit to measure the tilting angle (position) of the lift arm, the pitching angle of the tractor and heights of sensors from ground surface, (2) a controlling unit, (3) a hydraulic unit to operate a three-point hitch linkage by a lift arm cylinder, (4) a three-point hitch linkage and rotary implements, and (5) a setting unit to put the reference tillage depth and a dead zone into the control circuit. The tillage depth was controlled by an on/off operation of a solenoid valve, of which time was proportional to the controlling time. Experiments to evaluate the response characteristics of the control system were conducted under various engine speeds, i.e. various flow rates of hydraulic oil, various tillage depths and some input frequencies. The results of the response experiments of the control system are discussed in this paper.     

基于边光滑有限元法的加筋板静力和自由振动分析

运用边光滑有限元法,研究分析了加筋板结构的静力和自由振动问题。在边光滑有限元法中,将基于边的应变光滑技术用于对原来的应变场进行光滑操作;由于应变光滑技术能够适当地软化原来过刚的有限元模型,从而能够得到更加接近于系统准确刚度的光滑有限元模型;鉴于三角形单元良好的适用性,选用三角形单元对模型进行网格划分;同时,为了解决低阶Reissner-Mindlin板单元弯曲过程中的横向剪切自锁问题,采用了一种新型的离散剪切间隙技术。算例的数值计算结果表明,与传统的有限元法相比,边光滑有限元法能够得到精度更高的计算结果,且收敛更快,计算效率更佳。     

Transverse shear and normal deformation effects on vibration behaviors of functionally graded micro-beams

A quasi-three dimensional model is proposed for the vibration analysis of functionally graded(FG) micro-beams with general boundary conditions based on the modified strain gradient theory. To consider the effects of transverse shear and normal deformations, a general displacement field is achieved by relaxing the assumption of the constant transverse displacement through the thickness. The conventional beam theories including the classical beam theory, the first-order beam theory, and the higher...     

Recent advancement of flow-induced piezoelectric vibration energy harvesting techniques: principles,structures, and nonlinear designs

Energy harvesting induced from flowing fluids (e.g., air and water flows) is a well-known process, which can be regarded as a sustainable and renewable energy source. In addition to traditional high-efficiency devices (e.g., turbines and watermills), the micro-power extracting technologies based on the flow-induced vibration (FIV) effect have sparked great concerns by virtue of their prospective applications as a self-power source for the microelectronic devices in recent years. This article aims to conduct a comprehensive review for the FIV working principle and their potential applications for energy harvesting. First, various classifications of the FIV effect for energy harvesting are briefly introduced, such as vortex-induced vibration (VIV), galloping, flutter, and wake-induced vibration (WIV). Next, the development of FIV energy harvesting techniques is reviewed to discuss the research works in the past three years. The application of hybrid FIV energy harvesting techniques that can enhance the harvesting performance is also presented. Furthermore, the nonlinear designs of FIV-based energy harvesters are reported in this study, e.g., multi-stability and limit-cycle oscillation (LCO) phenomena. Moreover, advanced FIV-based energy harvesting studies for fluid engineering applications are briefly mentioned. Finally, conclusions and future outlook are summarized.