【摘要】：結(jié)合我國林區(qū)防火需求和消防車研究現(xiàn)狀,本文以一款由越野車底盤改裝而成的小型多功能消防車為研究對象,運用理論分析、試驗研究和計算機仿真相結(jié)合的方法,對樣車的振動特性進行了系統(tǒng)的研究�？紤]樣車實際作業(yè)情況,振動平順性的研究選擇空載和滿載兩種工況,根據(jù)GB/T4970,選取B、D路面等級下的三種常用車速來進行室內(nèi)道路模擬試驗和Matlab仿真；并依據(jù)GB/T7031采用總加權(quán)加速度均方根值法進行評價。經(jīng)過仿真和試驗分析可知：消防車振動響應(yīng)值較大,這主要是由于路況條件、載荷和車速等因素造成的,且由于Matlab仿真時建立的消防車數(shù)學(xué)模型是個理想的模型,忽略了發(fā)動機激勵和流體運動的影響,所得平順性結(jié)果優(yōu)于試驗結(jié)果,誤差值在5%左右。此外,通過對懸架固有頻率和阻尼比進行重新匹配實現(xiàn)了對消防車模型的優(yōu)化仿真,優(yōu)化后的加速度有效值改進了8%左右。消防車改裝后主要用于運水,因此在本研究中,將載荷對整車振動的影響作了深入的探究。首先利用Hypermesh和Nastran分析了消防車水罐在空載、50%充水、75%充水、100%充水4種工況下的流固耦合模態(tài),得出了各充水工況下前三階振動固有頻率值,同時得出響應(yīng)的振動模態(tài),分析可知：罐體隨充水量的增加振動明顯,且振動無突變屬于正常振動。另通過D級路面車速20km/h下四種充水工況下的試驗研究,得出了響應(yīng)的振動響應(yīng)值,并利用頻域分析細化了流固耦合對整車振動的作用效果。此外,利用試驗研究分析了發(fā)動機激勵對整車振動的影響,通過測量怠速(850rpm)、1500rpm、2500rpm和最大轉(zhuǎn)速(3500rpm)下的6個測點的加速度時間曲線和加速度功率譜曲線,對結(jié)果進行了時域和頻域分析。得出發(fā)動機轉(zhuǎn)速越快對整車振動影響越大,主要體現(xiàn)在對座椅垂向、橫向和前軸的影響。通過本文研究,得出了樣車振動情況受路面條件、車速、載荷(流固耦合)及發(fā)動機激勵等因素的影響,整車整體振動響應(yīng)值較大,即振動明顯�；谖恼卵芯�,建議對懸架、水罐隔波板、發(fā)動機懸置系統(tǒng)進行優(yōu)化,并在使用時控制車速,同時避免半載工況運行。
[Abstract]:According to the demand of forest fire prevention in China and the present situation of fire engine research, this paper takes a small multifunctional fire truck modified from off-road vehicle chassis as the research object, using the method of theoretical analysis, experimental research and computer simulation. The vibration characteristics of the sample car are studied systematically. Considering the actual operation situation of the sample car, the vibration ride comfort research selects two kinds of working conditions: no load and full load. According to GB/T4970, three kinds of commonly used vehicle speeds under B, D road grade are selected to carry out indoor road simulation test and Matlab simulation. According to GB/T7031, the total weighted acceleration root mean square method is used for evaluation. Through simulation and experimental analysis, it can be seen that the vibration response of fire engine is large, which is mainly caused by road condition, load and speed, and because the mathematical model of fire engine established in Matlab simulation is an ideal model. The effects of engine excitation and fluid motion are ignored, and the ride comfort results are better than the test results, and the error value is about 5%. In addition, the optimization simulation of the fire engine model is realized by matching the natural frequency and damping ratio of the suspension, and the effective value of the optimized acceleration is improved by about 8%. After refitting the fire engine, it is mainly used to transport water, so in this study, the influence of load on the vibration of the whole vehicle is deeply studied. Firstly, the fluid-solid coupling modes of fire truck water tank under four working conditions of no load, 50% water filling, 75% water filling and 100% water filling are analyzed by using Hypermesh and Nastran, and the natural frequency values of the first three vibration under each water filling condition are obtained. At the same time, the vibration mode of the response is obtained. The analysis shows that the vibration of the tank is obvious with the increase of water filling, and the vibration does not change to the normal vibration. In addition, through the experimental study under four kinds of water filling conditions under D grade pavement speed 20km/h, the vibration response value of the response is obtained, and the effect of fluid-solid coupling on the vibration of the whole vehicle is refined by frequency domain analysis. In addition, the influence of engine excitation on the vibration of the whole vehicle is studied and analyzed by experiments. The acceleration time curves and acceleration power spectrum curves of six measuring points at idle speed (850rpm), 1500rpm, 2500rpm and maximum speed (3500rpm) are measured. The results are analyzed in time domain and frequency domain. It is concluded that the faster the engine speed, the greater the influence on the vibration of the whole vehicle, which is mainly reflected in the vertical, transverse and front axle of the seat. Through the study of this paper, it is concluded that the vibration of the sample vehicle is affected by road conditions, speed, load (fluid-solid coupling) and engine excitation, and the overall vibration response of the vehicle is large, that is to say, the vibration is obvious. Based on the research of this paper, it is suggested that the suspension, water tank separator and engine mounting system should be optimized, and the speed should be controlled when in use, and the operation under half load condition should be avoided at the same time.
【學(xué)位授予單位】：北京林業(yè)大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2016
【分類號】：U469.68

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