張紅梅 張晨明 朱晨輝 祝英豪 李志杰 李鵬昌
摘要:為研究玉米免耕播種機振動特性以及振動對排種器漏播指數(shù)和重播指數(shù)的影響,搭建一套由振動加速度傳感器、電荷放大器、USB采集卡組成的播種作業(yè)振動測試系統(tǒng),在玉米免耕播種機免耕地表作業(yè)時進行振動測試采集播種作業(yè)的振動信號。因田間工作環(huán)境復雜,使用經典濾波法中的IIR濾波器濾除所采集振動信號中其他高頻干擾信號,對田間采集振動信號進行時域分析,均方值作為時域分析指標值。結果表明:振動加速度均方根隨著作業(yè)速度和旋耕機轉速的增加呈線性增加,旋耕機轉速和作業(yè)速度是引起玉米免耕播種機振動的主要因素,影響順序為:旋耕機轉速>作業(yè)速度。使用二次積分法對田間采集信號進行分析,得出播種機作業(yè)時最大振動位移為16.004mm,對振動信號進行頻域分析,使用直接法求出功率譜密度。結果表明:玉米免耕播種機振動頻率主要在0~100Hz之間,頻率分布與旋耕機轉速影響較大。根據田間振動信號所得工作參數(shù)搭建振動試驗臺,以播種機振動頻率、振動幅值、作業(yè)速度為試驗因素,合格指數(shù)、漏播指數(shù)為評價指標進行3因素3水平響應面試驗。結果表明:作業(yè)速度、振動幅值和振動頻率對合格指數(shù)和漏播指數(shù)影響較為顯著。各因素對合格指數(shù)影響順序為:振動幅值、作業(yè)速度、振動頻率;各因素對漏播指數(shù)影響順序為:振動幅值、振動頻率、作業(yè)速度。研究結果可為降低玉米免耕播種機振動和優(yōu)化指夾式排種器提供理論參考。
關鍵詞:玉米免耕播種機;指夾式排種器;振動;時頻分析;排種性能
中圖分類號:S223
文獻標識碼:A
文章編號:2095-5553 (2024) 05-0001-08
收稿日期:2022年8月31日? 修回日期:2022年12月5日*基金項目:河南省現(xiàn)代農業(yè)產業(yè)技術體系玉米全程機械化專項(HARS—22—02—G4)
第一作者:張紅梅,女,1977年生,河南駐馬店人,博士,教授;研究方向為智能農業(yè)裝備技術。E-mail: hmzh86022625@sina.com
通訊作者:朱晨輝,男,1989年生,河南開封人,博士,講師;研究方向為農業(yè)機械化及其自動化。E-mail: zhuchenhui@126.com
Analysis of vibration characteristics of corn no-till seeder and
its influence on seed metering performance
Zhang Hongmei, Zhang Chenming, Zhu Chenhui, Zhu Yinghao, Li Zhijie, Li Pengchang
(College of Mechanical and Electrical Engineering, Henan Agricultural University, Zhengzhou, 450002, China)
Abstract:
In order to study the vibration characteristics of maize no-tillage seeder and the influence of vibration on the leakage index and reseeding index of the seeder, a vibration test system composed of vibration acceleration sensor, charge amplifier and USB acquisition card was set up. A vibration test was carried out to collect the vibration signal of the sowing operation during the no-tillage surface operation of the corn no-till planter. Due to the complex working environment in the field, the IIR filter in the classical filtering method was used to filter out other high-frequency interference signals of the collected vibration signals. The time domain analysis was carried out on the vibration signals collected in the field, and the mean square value was used as the time domain analysis index value. The analysis results showed that the root mean square of vibration acceleration increased linearly with the increase of operating speed and rotational speed of rotary tillage, and the rotational speed and operating speed of rotary tillage were the main factors that caused the vibration of corn no-till planter. The order of influence? was: rotary tillage speed > working speed. Through using the quadratic integration method to analyze the collected signals in the field, it was concluded that the maximum vibration displacement of the planter was 16.004 mm. The vibration signal was analyzed in the frequency domain, and the power spectral density was obtained by the direct method. The results showed that the vibration frequency of the corn no-till planter was mainly between 0-100 Hz. The frequency distribution and rotary tillage speed had a great influence. According to the working parameters obtained from the field vibration signal, a vibration test bench was built, and the vibration frequency, vibration amplitude and working speed of the seeder were used as test factors, and the pass index and missed seeding index were used as evaluation indicators to conduct a three-factor and three-level response surface test. The analysis results showed that the working speed, vibration amplitude and vibration frequency had significant effects on the pass index and missed broadcast index. The order of the influence of each factor on the qualification index? was: vibration amplitude, working speed and vibration frequency, the order of each factor on the missed seeding index? was: vibration amplitude, vibration frequency and working speed. The research results of this paper can provide theoretical reference for reducing the vibration of maize no-till seeder and optimizing the finger clip seed feeder.
Keywords:
corn no-tillage seeder; finger-clip seed metering device; vibration; time-frequency analysis; seeding performance
0 引言
玉米免耕播種機在田間地表的不平度、機具的振動載荷、拖拉機行走速度等多種因素導致了玉米的均勻性與合格指數(shù)降低[1, 2]。
近幾年,國內外學者對振動對播種性能的影響進行了研究。張濤等[3]通過對田間作業(yè)時免耕播種機排種器振特性測試與分析,運用離散元軟件模擬了玉米種群的運動規(guī)律。王奇等[4]建立免耕播種機的振動特性模型,求解其穩(wěn)態(tài)振動響應。Liu等[5]采用正交試驗的方法對播種機振動特性進行研究,結果表明播種機作業(yè)前進速度為7km/h時振動較大。廖宜濤等[6]通過振動臺架試驗發(fā)現(xiàn)吸種負壓和振動頻率對氣力式排種器合格指數(shù)影響較大。黃與霞等[7]通過振動試驗,得出振動幅值、作業(yè)速度與振動頻率對勺輪式排種器播種質量的影響。
玉米免耕播種機在開溝器前增加了圓盤鋸齒開溝器裝置,作業(yè)時振動對播種質量影響較大。本文以帶旋耕刀的免耕播種機作為研究對象,通過對整機工作原理及結構的分析,采集播種機實際田間工作時的振動信號進行振動的影響因素分析,并在實驗室搭建振動試驗臺,探究各因素對指夾式排種器播種質量的影響,為改進播種機整體結構和優(yōu)化指夾式排種器提供理論依據。
1 免耕播種機結構和工作原理
玉米免耕播種機如圖1所示。主要由機架、旋耕裝置、播種排肥裝置和覆土鎮(zhèn)壓裝置組成,由四點懸掛和萬向節(jié)聯(lián)軸器與拖拉機相連。旋耕裝置采用了圓盤鋸齒開溝器,通過內翻刀和外翻刀形成一定夾角,將殘留的秸稈進行二次粉碎翻到背壟上,使種子著床到凈土上,保證種子出苗率。播種裝置是由種箱和肥箱、排種器和排肥器、輸種管、開溝器組成。圖2為指夾式排種器結構。
2 免耕播種機田間測試
1) 機具與地表相關參數(shù)。2021年6月12日在河南省周口市商水縣河南農業(yè)大學商水試驗田進行田間測試,前茬作物為小麥,土壤特質為潮土,拖拉機選用CHERY RC1004 4×4輪式拖拉機,機具與地表相關參數(shù)見表1。
2) 測試方法。本次振動測試試驗使用單向電荷型加速度傳感器,靈敏度為100.08mV/g,加速度可測范圍為-50~+50g,采樣率設置為1000Hz(采樣時間間隔為0.001s),PC計算機的DAQ軟件控制數(shù)據采集過程[8]參數(shù)如表2所示。
3) 試驗方案。本次振動測試選用加速度傳感器[9],固定在種箱后方,如圖3所示。因機械式排種器作業(yè)速度最佳在2~6km/h之內,作業(yè)速度v選擇2km/h、4km/h、6km/h,拖拉機轉速選擇1500~2300r/min。旋耕機轉速n′選擇280~320r/min。
通過更換拖拉機不同擋位調整作業(yè)速度和旋耕機轉速,在拖拉機帶動免耕播種機平穩(wěn)工作時開始測試,采集15s的振動數(shù)據。每種工況下進行5次重復試驗,后續(xù)振動信號由Matlab進行濾波和時頻分析,振動測試現(xiàn)場如圖4所示。
3 振動信號處理
3.1 濾波處理
在實際采集過程中,因大田工作環(huán)境復雜所以數(shù)據采集的振動信號包含了很多的噪聲部分,使用經典濾波法中的IIR濾波器對信號進行濾波處理,減少干擾信號對真實數(shù)據的影響[8]。
IIR濾波器結構帶有反饋環(huán)路,又稱為遞歸型濾波器。IIR濾波器的N階差分方程如式(1)所示。
根據回歸曲線和表中的數(shù)據可得,影響合格指數(shù)的順序為:振動幅值、作業(yè)速度、振動頻率;漏播指數(shù)的順序為:振動幅值、振動頻率、作業(yè)速度;為探究試驗指標和各因素的影響關系,使用響應面法求解各因素之間的交互關系。固定一個因素為0水平。得到另外兩因素響應面如圖11所示。
作業(yè)速度和振動幅值對合格指數(shù)有交互作用。當振動幅值一定時,合格指數(shù)隨著作業(yè)速度的增加而降低,且降低趨勢逐漸增大;當作業(yè)速度一定時,合格指數(shù)隨著振動幅值的增加而降低,且降低趨勢逐漸減小的。振動幅值分別與作業(yè)速度和振動頻率對漏播指數(shù)有交互作用。當振動幅值一定時,漏播指數(shù)隨著作業(yè)速度的增大而增大,且上升趨勢逐漸增大的;漏播指數(shù)隨著振動頻率的增大而增大的,且上升趨勢逐漸增大;當作業(yè)速度和振動頻率一定時,漏播指數(shù)隨著振動幅值的增大而增大的,且上升趨勢是平穩(wěn)增大的。圖12為通過延遲攝影功能拍攝漏種現(xiàn)象。
根據各因素對合格指數(shù)和漏播指數(shù)的影響結果分析可得,對比無振動和振動條件下,振動的增加會使合格指數(shù)明顯減小。對比三因素發(fā)現(xiàn)振動幅值是影響合格指數(shù)和漏播指數(shù)的主要因素,振動幅值的增加會使合格指數(shù)和漏播指數(shù)減小趨勢增大。主要原因為:種子運動過程中受到重力、離心力、摩擦力和振動所給的豎直力的作用,當振動幅值增大時,種子所受的垂直加速度增大,使種子從指夾中脫落,產生漏播現(xiàn)象。如何使種子在振動條件下不脫落,是優(yōu)化排種器結構的有效途徑。試驗結果為指夾式排種器優(yōu)化提供理論依據。
5 結論
1) 搭建一套玉米免耕播種機振動測試系統(tǒng),在免耕播種機工作時進行振動測試,并采集振動數(shù)據,分析不同作業(yè)速度和不同旋耕機轉速信號。結果表明,旋耕機轉速和作業(yè)速度對振動加速度影響較顯著,旋耕機轉速的振動加速度均方根最大增大倍數(shù)為1.45,作業(yè)速度的振動加速度均方根最大增大倍數(shù)為1.37,旋耕機轉速比作業(yè)速度對播種機振動更顯著。通過對振動加速度二次積分,播種機最大振動位移為16.004mm。
2) 不同工況下頻域分析結果表明,免耕播種機的振動頻率分布在0~100Hz,振動頻率分布與旋耕機轉速有關,與作業(yè)速度影響較小,旋耕刀振動基頻為28.02~31.98Hz,二倍頻為56.04~63.96Hz,三倍頻為84.06~95.94Hz。在旋耕裝置與播種機主體之間增加減震裝置是降低播種機振動的有效途徑。
3) 搭建振動試驗臺并開展排種器振動試驗,把作業(yè)速度、振動幅值、振動頻率作為主要試驗因素,合格指數(shù)、漏播指數(shù)作為試驗指標進行三因素三水平響應面試驗。通過二次回歸正交組合試驗可得,作業(yè)速度、振動幅值和振動頻率對合格指數(shù)和漏播指數(shù)影響顯著。合格指數(shù)影響順序為:振動幅值、作業(yè)速度、振動頻率;漏播指數(shù)的順序為:振動幅值、振動頻率、作業(yè)速度。為優(yōu)化指夾排種器關鍵部件,減小排種器漏播情況提供理論支撐。
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